Bump version to 0.2.8

Add GitHub issue templates

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -0,0 +1,101 @@
+name: Bug report
+description: Report a reproducible problem with Cassady / cass
+title: "bug: "
+labels: [bug]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for reporting a bug. Please include enough detail for someone to reproduce it.
+  - type: textarea
+    id: summary
+    attributes:
+      label: Summary
+      description: What went wrong?
+      placeholder: Cassady crashes when...
+    validations:
+      required: true
+  - type: textarea
+    id: steps
+    attributes:
+      label: Steps to reproduce
+      description: List the exact commands, key presses, or config changes needed to trigger the issue.
+      placeholder: |
+        1. Run `cass ...`
+        2. Press ...
+        3. See ...
+    validations:
+      required: true
+  - type: textarea
+    id: expected
+    attributes:
+      label: Expected behavior
+      description: What did you expect to happen?
+    validations:
+      required: true
+  - type: textarea
+    id: actual
+    attributes:
+      label: Actual behavior
+      description: What happened instead? Paste errors, logs, or terminal output when useful.
+      render: text
+    validations:
+      required: true
+  - type: input
+    id: version
+    attributes:
+      label: Cassady version
+      description: Output of `cass --version` or `cassady --version`.
+      placeholder: cassady 0.2.x
+    validations:
+      required: true
+  - type: dropdown
+    id: install
+    attributes:
+      label: Install method
+      options:
+        - Release archive
+        - cargo install --git
+        - cargo install --path / local build
+        - Other
+    validations:
+      required: true
+  - type: dropdown
+    id: platform
+    attributes:
+      label: Platform
+      options:
+        - macOS Apple Silicon
+        - macOS Intel
+        - Linux x86_64
+        - Linux ARM64
+        - Windows x86_64
+        - Other
+    validations:
+      required: true
+  - type: textarea
+    id: environment
+    attributes:
+      label: Environment details
+      description: Terminal, shell, provider/model, access mode, and anything notable from `cass check`. Do not include API keys.
+      placeholder: |
+        Terminal: ...
+        Shell: ...
+        Provider/model: ...
+        Access mode: ...
+        `cass check`: ...
+  - type: textarea
+    id: config
+    attributes:
+      label: Relevant configuration
+      description: Paste sanitized snippets from `~/.cass/config.json`, `providers.json`, or `models.json` if relevant. Remove API keys and secrets.
+      render: json
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Checklist
+      options:
+        - label: I removed API keys, tokens, and other secrets from this report.
+          required: true
+        - label: I searched existing issues for a duplicate.
+          required: true

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,5 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Questions and usage help
+    url: https://github.com/owenqwenstarsky/cassady/discussions
+    about: Ask questions, share setup notes, or discuss ideas before filing an issue.

.github/ISSUE_TEMPLATE/docs.yml

@@ -0,0 +1,44 @@
+name: Documentation issue
+description: Report missing, confusing, or incorrect documentation
+title: "docs: "
+labels: [documentation]
+body:
+  - type: textarea
+    id: location
+    attributes:
+      label: Documentation location
+      description: Link to the page or name the file/section, if known.
+      placeholder: README.md, docs/providers.md, docs/access-modes.md, ...
+    validations:
+      required: true
+  - type: textarea
+    id: issue
+    attributes:
+      label: What is unclear or incorrect?
+      description: Describe the gap, mistake, or confusing wording.
+    validations:
+      required: true
+  - type: textarea
+    id: suggested
+    attributes:
+      label: Suggested improvement
+      description: If you have specific wording or examples in mind, add them here.
+  - type: dropdown
+    id: impact
+    attributes:
+      label: Impact
+      options:
+        - Blocks installation or first use
+        - Causes incorrect configuration
+        - Confuses normal usage
+        - Typo or small polish
+        - Other
+    validations:
+      required: true
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Checklist
+      options:
+        - label: I searched existing issues for a duplicate.
+          required: true

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -0,0 +1,59 @@
+name: Feature request
+description: Suggest an improvement or new capability for Cassady / cass
+title: "feat: "
+labels: [enhancement]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for suggesting an improvement. Please focus on the user problem and desired outcome.
+  - type: textarea
+    id: problem
+    attributes:
+      label: Problem or use case
+      description: What are you trying to do, and what makes it hard today?
+      placeholder: I want to...
+    validations:
+      required: true
+  - type: textarea
+    id: proposal
+    attributes:
+      label: Proposed behavior
+      description: Describe the change you would like to see.
+    validations:
+      required: true
+  - type: textarea
+    id: alternatives
+    attributes:
+      label: Alternatives considered
+      description: What workarounds or other designs have you considered?
+  - type: dropdown
+    id: area
+    attributes:
+      label: Area
+      options:
+        - Terminal UI
+        - Setup and configuration
+        - Providers and models
+        - Tools and file editing
+        - Safety and access modes
+        - Conversation history and resume
+        - Documentation
+        - Packaging and releases
+        - Other
+    validations:
+      required: true
+  - type: textarea
+    id: examples
+    attributes:
+      label: Examples or mockups
+      description: Add sample commands, UI text, config snippets, screenshots, or links that clarify the request.
+  - type: checkboxes
+    id: checklist
+    attributes:
+      label: Checklist
+      options:
+        - label: I searched existing issues for related requests.
+          required: true
+        - label: This request is in scope for a terminal coding agent, not a general package manager or updater.
+          required: false

.github/ISSUE_TEMPLATE/task.yml

@@ -0,0 +1,52 @@
+name: Maintenance task
+description: Track internal cleanup, refactoring, testing, CI, or release work
+title: "chore: "
+labels: [maintenance]
+body:
+  - type: textarea
+    id: goal
+    attributes:
+      label: Goal
+      description: What should be done, and why?
+    validations:
+      required: true
+  - type: textarea
+    id: scope
+    attributes:
+      label: Scope
+      description: List concrete files, modules, or workflows that are in scope.
+      placeholder: |
+        - src/...
+        - tests/...
+        - .github/workflows/...
+    validations:
+      required: true
+  - type: textarea
+    id: out_of_scope
+    attributes:
+      label: Out of scope
+      description: Note anything this task should intentionally avoid.
+  - type: textarea
+    id: acceptance
+    attributes:
+      label: Acceptance criteria
+      description: What must be true before this can be closed?
+      placeholder: |
+        - [ ] ...
+        - [ ] `cargo test --locked --all-targets` passes
+    validations:
+      required: true
+  - type: dropdown
+    id: area
+    attributes:
+      label: Area
+      options:
+        - Refactoring
+        - Tests
+        - CI
+        - Release process
+        - Dependencies
+        - Documentation maintenance
+        - Other
+    validations:
+      required: true

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cassady"
-version = "0.2.3"
+version = "0.2.8"
 edition = "2021"
 description = "Cassady/Cass minimal terminal coding agent"
 license = "MIT"
@@ -23,22 +23,26 @@ anyhow = "1"
 async-trait = "0.1"
 chrono = { version = "0.4", features = ["serde"] }
 clap = { version = "4", features = ["derive"] }
-crossterm = "0.28"
+crossterm = "0.29"
 dirs = "5"
 futures-util = "0.3"
 ignore = "0.4"
 include_dir = "0.7"
 nanoid = "0.4"
-ratatui = "0.28"
+ratatui = { version = "0.30", default-features = false, features = ["crossterm", "underline-color"] }
 regex = "1"
 pulldown-cmark = "0.12"
 reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls", "stream"] }
+semver = "1"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
+sha2 = "0.10"
+flate2 = "1"
+tar = "0.4"
 thiserror = "1"
 tokio = { version = "1", features = ["macros", "rt-multi-thread", "sync", "time", "process", "io-util"] }
-tui-textarea = "0.6"
 unicode-width = "0.1"
+zip = { version = "2", default-features = false, features = ["deflate"] }
 
 [dev-dependencies]
 tempfile = "3"

README.md

@@ -8,9 +8,10 @@ The project installs two equivalent commands, `cass` and `cassady`; examples use
 
 - Provider support is OpenAI-compatible chat/completions APIs only.
 - The primary interface is an interactive terminal UI.
+- v0.2.6 adds an experimental Rust embedding API for headless sessions; it is useful for early integrations but not yet a stable long-term library contract.
 - Config and conversation state live under `~/.cass`.
 - Windows binaries are built for releases, but deeper Windows terminal, path, shell, and filesystem polish is planned for a later release.
-- Cassady is not an installer, updater, or package manager.
+- `cass update` can update release-archive installs from official GitHub releases; external package managers should still be updated through their own tools.
 
 ## Install from source
 
@@ -38,6 +39,7 @@ If Cassady cannot resolve a usable provider, model, or API key, it offers to run
 ```sh
 cass setup
 cass check
+cass update --check
 cass
 ```
 
@@ -65,12 +67,14 @@ cass --resume <chat-id>
 cass --resume
 cass check
 cass setup
+cass update
 ```
 
-`cass --resume` without an id lists saved chats for the current directory. When Cassady exits a chat, it prints a resume command for that session.
+`cass --resume` without an id lists saved chats for the current directory. `cass update` checks official GitHub releases and can update both `cass` and `cassady` in the current install directory. When Cassady exits a chat, it prints a resume command for that session.
 
 Common in-chat commands:
 
+- `/branch` or `/restore`: open the branch/restore menu.
 - `/model <model>`: switch to a model from `~/.cass/models.json`.
 - `/new`: create a new chat for the current directory.
 - `/resume <chat>`: resume a saved chat for the current directory.
@@ -85,7 +89,7 @@ Helpful keys:
 - `Tab`: cycle reasoning effort while idle.
 - `Ctrl-O`: toggle compact/full tool output display.
 - `Ctrl-Shift-R` or `Ctrl-R`: toggle reasoning display.
-- `Esc`: request turn cancellation while a turn is running.
+- `Esc`: request turn cancellation while a turn is running; while idle, press twice within 1.5 seconds to open branch/restore.
 - `Ctrl-C` twice within 1.5 seconds: exit.
 
 ## Safety model
@@ -98,6 +102,12 @@ Cassady exposes tools according to the active access mode:
 
 Use `--readonly`, `--workspace-edit`, or `--full-access` to choose a mode at launch, or press `Shift-Tab` while idle.
 
+## Branch and restore
+
+Press `Esc` twice while idle, or type `/branch`, to browse the current conversation's branch family. Selecting an earlier user message, assistant message, tool call, or tool result creates a new branch conversation instead of truncating the original chat. The menu also lets you switch back to related branches later.
+
+Conversation-only branching is the safe default. If you choose file restore, Cassady restores only file changes it tracked from successful `write` and `edit` tools. Shell commands, manual edits, unsupported files, and hash conflicts are reported or skipped rather than overwritten blindly.
+
 ## Configuration and docs
 
 Cassady stores user-editable files in `~/.cass`:
@@ -105,19 +115,36 @@ Cassady stores user-editable files in `~/.cass`:
 - `config.json`: active defaults and preferences.
 - `providers.json`: provider base URLs and API key references.
 - `models.json`: model metadata.
-- `global.md`: optional global instructions added to new chats.
+- `global.md`: optional global instructions added to new chat system prompts when they fit the active request; they cannot override access modes, tool denials, approvals, or workspace boundaries.
 - `docs/`: bundled documentation installed from the current binary.
 
 API key references should usually be written as environment variables such as `"$OPENAI_API_KEY"`.
 
 Detailed bundled docs live in this repository under [`docs/`](docs/README.md) and are installed to `~/.cass/docs` at runtime.
 
+## Experimental Rust embedding API
+
+Rust applications can import Cassady and run headless sessions without launching the TUI:
+
+```rust
+use cassady::prelude::*;
+
+let session = SessionBuilder::new()
+    .cwd(".")
+    .access_mode(AccessMode::ReadOnly)
+    .build()
+    .await?;
+```
+
+See [Experimental Rust embedding API](docs/embedding.md) for session creation, streamed events, approval handling, cancellation, and current limitations.
+
 ## More documentation
 
 - [Commands](docs/commands.md)
 - [Configuration](docs/configuration.md)
 - [Providers and models](docs/providers.md)
 - [Access modes and tool safety](docs/access-modes.md)
+- [Experimental Rust embedding API](docs/embedding.md)
 - [Workflows](docs/workflows.md)
 - [Troubleshooting](docs/troubleshooting.md)
 - [Platform notes](docs/platforms.md)

ROADMAP.md

@@ -1,102 +1,167 @@
 # Cassady (Cass) Roadmap
 
-## v0.2.4 — Windows CLI Usability
+## v0.2.8 — Conversation Branch and Restore
 
-This release focuses on making Cassady feel reliable and native when the CLI is run on Windows. It covers runtime usability after `cass` or `cassady` is already available on the machine; installers, package managers, PATH setup, code signing, and update delivery are intentionally out of scope.
+This release focuses on making conversation recovery safe and explorable. Pressing `Esc` twice while idle opens a branch/restore menu where users can browse prior user messages, assistant messages, and tool calls, create a new branch from a selected checkpoint, and optionally restore Cassady-tracked file edits without destroying the original conversation. See `plans/V0_2_8_CONVERSATION_BRANCH_RESTORE_PLAN.md`.
 
-### Terminal Experience
+### Branch Navigation
 
-- [ ] **Make interactive rendering robust in Windows terminals.** Ensure chat, setup, confirmation prompts, streamed output, spinners, diffs, and tool summaries render cleanly in Windows Terminal, PowerShell, Command Prompt, and common VS Code integrated terminals.
-  - Enable or gracefully detect ANSI/VT support instead of emitting broken escape sequences.
-  - Respect `NO_COLOR`, non-interactive output, redirected stdout/stderr, and narrow terminal widths.
-  - Avoid relying on glyphs, emoji, box drawing, or cursor control sequences that render poorly on default Windows fonts.
-  - Keep wrapping and cursor positioning correct for multi-line input, Markdown output, and long tool-call summaries.
+- [x] **Open a branch/restore menu with double Esc.** Add an idle `Esc`-twice shortcut that mirrors the discoverability of double `Ctrl-C` while preserving current busy-turn cancellation and approval-denial behavior.
+  - Keep draft input intact when the menu is opened or cancelled.
+  - Provide clear status text after the first `Esc` so users know a second press opens branch/restore.
 
-- [ ] **Harden keyboard handling on Windows.** Make the TUI and prompts respond predictably to Windows console input events.
-  - Verify `Enter`, `Backspace`, `Delete`, arrow keys, `Home`, `End`, `PageUp`, `PageDown`, `Tab`, and paste behavior.
-  - Preserve existing `Ctrl-C` cancellation semantics and handle `Ctrl-Break`/console close events gracefully where supported.
-  - Ensure `Esc` cancellation and prompt dismissal work consistently across PowerShell, Command Prompt, and Windows Terminal.
+- [x] **Browse checkpoints across the related branch family.** Show user messages, assistant messages, tool-call requests, and tool results from the current chat and related branches.
+  - Include enough preview text, tool names, paths, timestamps, and branch labels to choose the right point.
+  - Allow switching back to the original conversation or another existing branch from the same menu.
 
-- [ ] **Improve plain CLI output for Windows users.** Commands such as `cass check`, setup diagnostics, validation errors, and usage text should remain readable without a fully interactive terminal.
-  - Prefer actionable Windows examples using PowerShell syntax when the current platform is Windows.
-  - Avoid POSIX-only command snippets in runtime guidance unless explicitly labeled.
-  - Keep error messages copy/paste-friendly and free of terminal control characters when output is redirected.
+### Safe Conversation Branching
 
-### Windows Paths and Files
+- [x] **Create branches instead of destructive reverts.** Selecting a checkpoint should write a new conversation JSONL with parent/checkpoint metadata, leaving the source conversation unchanged.
+  - Support repeated branching so users can return to the menu later and branch or switch again.
+  - Keep older conversations without branch metadata loadable.
 
-- [ ] **Support Windows path syntax everywhere the CLI accepts paths.** Normalize and validate paths consistently across arguments, tool calls, diffs, session metadata, and model-visible file references.
-  - Handle drive-letter paths such as `C:\Users\name\project`, rooted paths such as `\temp`, UNC paths such as `\\server\share\repo`, and mixed `/`/`\` separators.
-  - Preserve user-facing paths in a readable Windows form while using canonicalized paths for safety decisions.
-  - Avoid treating `:` in drive letters as URL schemes or command separators.
-  - Add tests for relative path resolution from Windows workspaces and for paths containing spaces, apostrophes, parentheses, brackets, and non-ASCII characters.
+- [x] **Handle tool-call checkpoints cleanly.** Branching at a specific tool call or tool result should preserve a valid provider message history.
+  - Repair partial multi-tool assistant turns with synthetic cancelled/omitted tool results where needed.
+  - Add tests for branching at user, assistant, and tool boundaries.
 
-- [ ] **Respect Windows filesystem semantics in workspace policy.** Keep read, write, edit, and shell safety checks correct on NTFS and common Windows filesystems.
-  - Account for case-insensitive path comparisons, symlinks, junctions, directory symlinks, and network shares.
-  - Prevent workspace escapes through `..`, junctions, symlink targets, alternate path spellings, and UNC aliases.
-  - Handle reserved device names, trailing dots/spaces, invalid filename characters, and long-path edge cases with clear errors.
-  - Preserve current access modes (`read-only`, `workspace-edit`, `full-access`) with Windows-specific authorization tests.
+### File Edit Restoration
 
-- [ ] **Handle line endings and encodings cleanly.** Make file reads, edits, diffs, and generated files predictable on Windows projects.
-  - Preserve existing CRLF/LF style when editing files where practical.
-  - Render diffs clearly even when files use CRLF line endings.
-  - Avoid corrupting UTF-8 with BOM, UTF-16, or non-UTF-8 files; detect unsupported text encodings and explain the limitation.
-  - Keep binary-file detection reliable for Windows executables, images, archives, and generated build artifacts.
+- [x] **Journal Cassady file edits with restorable snapshots.** Record successful `write` and `edit` tool mutations outside the model-visible transcript with before/after hashes and snapshots.
+  - Keep restore support limited to Cassady-tracked file tools; warn that shell commands and manual edits are not automatically reversible.
+  - Store enough data to restore both backward and forward between tracked checkpoints.
 
-### Shell and Process Integration
+- [x] **Offer explicit conversation-only or conversation-plus-files restore actions.** Make conversation-only branching the safe default, and require confirmation before changing workspace files.
+  - Preview files to update or delete, detect hash conflicts, and refuse unsafe overwrites by default.
+  - Use atomic writes for restored files and preserve clear status/transcript messages for skipped or conflicted paths.
 
-- [ ] **Use the right shell behavior on Windows.** Make `shell` tool execution, approval prompts, command summaries, cancellation, and exit status reporting work with Windows process semantics.
-  - Prefer PowerShell-friendly examples and diagnostics while still supporting `cmd.exe`-style commands when users provide them.
-  - Quote paths with spaces safely and avoid POSIX-only escaping in Windows-generated commands.
-  - Surface the actual executable, working directory, exit code, stdout, and stderr in a way users can debug.
-  - Cancel long-running child processes cleanly, including process trees where possible.
+### Documentation and Validation
 
-- [ ] **Normalize environment-variable handling.** Ensure provider API key checks, diagnostics, setup guidance, and spawned tools work with Windows environment conventions.
-  - Treat environment variable names consistently despite Windows case-insensitive lookup behavior.
-  - Show PowerShell examples such as `$env:OPENAI_API_KEY = "..."` for temporary values.
-  - Avoid relying on POSIX shell expansion, `export`, `$VAR`, or `~` in Windows-specific guidance.
+- [x] **Document branch/restore workflows and limitations.** Update README and bundled docs with the double-`Esc` shortcut, menu controls, branch semantics, and file-restore safety model.
+  - Include troubleshooting for restore conflicts and unsupported shell/manual filesystem changes.
 
-- [ ] **Support common Windows external commands and editors.** When Cassady suggests or launches helper commands, make the behavior compatible with typical Windows environments.
-  - Detect missing tools and explain alternatives rather than assuming Unix utilities are present.
-  - Avoid hard dependencies on `sh`, `bash`, `grep`, `sed`, `cat`, `less`, or `/tmp` during normal CLI operation.
-  - Respect configured editor/browser commands and quote file paths correctly when opening files or URLs.
+- [x] **Test the branch and restore model.** Cover branch metadata, checkpoint extraction, tool-call repair, edit journaling, restore planning, and keybinding behavior where practical.
+  - Verify `cargo fmt` and `cargo test --locked --all-targets` pass before release.
 
-### Config, State, and Session Usability
+## v0.2.7 — Self-Update Command
 
-- [ ] **Use Windows-appropriate runtime locations.** Keep config, logs, caches, sessions, temporary files, and diagnostics in locations that align with Windows conventions.
-  - Prefer the existing cross-platform directory abstraction where available, and verify behavior with `APPDATA`, `LOCALAPPDATA`, `TEMP`, and `USERPROFILE`.
-  - Expand `~` and environment-derived paths consistently in config values.
-  - Keep session history portable enough to display Windows paths without breaking transcript replay.
+This release focuses on making Cassady easy to keep current after installation. The goal is to let users run one clean command, `cass update`, to check GitHub releases, choose the recommended prebuilt binary or a source-build fallback, verify what will be installed, and update both `cass` and `cassady` safely. See `plans/V0_2_7_SELF_UPDATE_COMMAND_PLAN.md`.
 
-- [ ] **Make diagnostics expose Windows-specific context.** Improve `cass check` and error reports so Windows users can understand terminal, filesystem, shell, and config problems quickly.
-  - Include OS, architecture, terminal detection, active shell, config path, workspace path, and access mode when relevant.
-  - Clearly distinguish provider/API-key failures from Windows runtime issues.
-  - Recommend Windows-native remediation steps without mentioning installation tasks.
+### Update Command Experience
 
-- [ ] **Keep aliases and command parsing consistent.** Ensure `cass` and `cassady` subcommands, flags, config overrides, and path arguments behave the same on Windows as on Unix-like systems.
-  - Validate quoting behavior for arguments containing spaces and backslashes.
-  - Ensure help text and examples do not imply shell features unavailable in PowerShell or Command Prompt.
-  - Keep machine-readable output stable across platforms when output is consumed by scripts.
+- [x] **Add a polished `cass update` command.** Check the official Cassady GitHub releases, compare the running version to the selected release, and guide the user through an interactive update flow.
+  - Keep update independent of provider/model setup so it works even when config is missing or invalid.
+  - Support script-friendly checks with flags such as `--check`, `--dry-run`, and `--yes`.
 
-### Verification and Documentation
+- [x] **Select the right update path.** Prefer a matching prebuilt release archive when available, with explicit `--prebuilt` and `--source` modes for users who want to choose.
+  - Support the same macOS, Linux, and Windows targets used by Cassady releases.
+  - Offer source builds for unsupported targets or users who prefer building locally.
 
-- [ ] **Add Windows-focused automated coverage.** Add unit and integration tests that exercise Windows path parsing, policy checks, config discovery, line endings, environment variables, and command rendering.
-  - Use platform-gated tests for behavior that can only run on Windows.
-  - Add platform-independent tests for Windows path strings where possible.
-  - Include regression tests for spaces in paths, UNC paths, CRLF edits, and workspace escape attempts.
+### Safe Installation
 
-- [ ] **Run a manual Windows CLI acceptance pass.** Validate the release on a real Windows environment, not just cross-compilation.
-  - Test PowerShell, Command Prompt, Windows Terminal, and VS Code integrated terminal.
-  - Exercise interactive chat, first-run setup, `cass check`, tool approvals, file read/edit/diff, shell cancellation, and redirected output.
-  - Record any unsupported terminal or shell behavior as explicit known limitations.
+- [x] **Verify and stage prebuilt artifacts before replacing binaries.** Download archives and SHA-256 files from the release, verify checksums, extract safely, and validate staged `cass`/`cassady` binaries.
+  - Reject checksum mismatches, unsafe archive paths, missing binaries, and unexpected versions.
+  - Show clear progress and failure messages without dumping raw implementation details.
 
-- [ ] **Update runtime documentation for Windows usage.** Refresh README and bundled docs with Windows-specific CLI usage guidance while avoiding installation instructions.
-  - Document PowerShell environment-variable examples, path examples, terminal expectations, and known limitations.
-  - Include troubleshooting for broken colors, bad wrapping, path authorization failures, CRLF diffs, and missing Unix helper commands.
-  - Keep all Windows guidance consistent with existing access modes and safety policies.
+- [x] **Replace installed binaries cleanly.** Update the current binary and same-directory companion binary when possible, using backups and rollback on failure.
+  - Do not auto-run `sudo` or administrator prompts.
+  - Handle Windows executable replacement with a staged helper or documented manual fallback if necessary.
 
-## v0.2.3 — Documentation and README Refresh
+### Source Build Fallback and Documentation
 
-This release focuses on making Cassady understandable, trustworthy, and easy to operate by rewriting the README and bringing all bundled documentation up to date with the current CLI behavior. The work should cover user-facing documentation only; broad CLI feature work and Windows-specific runtime improvements are deferred to v0.2.4. See `plans/V0_2_3_DOCUMENTATION_README_REFRESH_PLAN.md`.
+- [x] **Build from release source when requested.** Download the selected release source, validate its version, check for Rust tooling, run a locked release build, and install the resulting local binaries.
+  - Keep source mode tied to release tags rather than arbitrary branches.
+  - Do not attempt cross-compilation or Rust toolchain installation in this release.
+
+- [x] **Document and test update behavior.** Update README and bundled docs for `cass update`, platform notes, troubleshooting, and package-manager caveats.
+  - Add tests for release parsing, target mapping, asset selection, checksum validation, archive extraction safety, install planning, and mocked update flows.
+
+## v0.2.6 — Rust Embedding API ✅ Completed
+
+This release focuses on adding the first intentional Rust library surface for embedding Cassady in other Rust projects. The goal is to provide the bones for programmatic, headless agent sessions: configure a workspace, start or resume an agent session, send turns, stream typed events, and handle approvals without launching the TUI. See `plans/V0_2_6_RUST_EMBEDDING_API_PLAN.md`.
+
+### Experimental Public API
+
+- [x] **Add a supported embedding module.** Provide a small `cassady::embedding` API with builder, session, turn, event, approval, and error types so callers do not need to stitch together internal modules directly.
+  - Mark the API experimental for v0.2.6 rather than promising long-term semver stability.
+  - Keep existing CLI/TUI behavior unchanged while steering library users toward the new module.
+
+- [x] **Support host-configured agent sessions.** Let Rust callers create or resume headless sessions with explicit cwd, access mode, model/provider overrides, reasoning effort, and Cassady config root.
+  - Reuse existing config files, global instructions, bundled docs, security policy, and JSONL conversation storage.
+  - Avoid requiring callers to construct CLI-specific types.
+
+### Headless Turn Execution
+
+- [x] **Run agent turns programmatically.** Add a Tokio-native API for sending one user message, streaming assistant/tool/status events, and returning the updated session or conversation state.
+  - Prevent or clearly reject overlapping turns unless the type design makes them impossible.
+  - Preserve provider streaming, tool execution, prompt generation, and context behavior from the existing agent loop.
+
+- [x] **Expose approval handling to host applications.** Allow embedded callers to approve or deny tool approval requests, especially shell commands in `workspace-edit` mode.
+  - Include request id, tool call id, tool name, arguments, and reason in approval events.
+  - Document cancellation/drop behavior for active turns.
+
+### Documentation and Validation
+
+- [x] **Add a minimal headless example.** Include a compilable Rust example that imports Cassady, starts a session, sends a prompt, and prints streamed assistant output.
+  - Note that a configured OpenAI-compatible provider and API key are still required.
+  - Show where to handle approval requests even if the first example defaults to `read-only`.
+
+- [x] **Document the experimental Rust API.** Add bundled docs and README links for setup requirements, basic usage, event handling, approvals, limitations, and current non-goals.
+  - Make clear that multi-agent orchestration, custom providers, custom tools, daemons, and stable plugin APIs are deferred.
+
+- [x] **Test embedding without a terminal.** Add integration tests that use temporary config/conversation roots and mock provider responses to verify session creation, turn streaming, resume, approval flow, and access-mode behavior.
+  - Ensure `cargo test --locked --all-targets` covers the new public API and examples.
+
+## v0.2.4 — System Prompt Refinement
+
+This release focuses on making Cassady's system prompt clearer, more intuitive, and more useful for everyday coding work without letting it become bulky. The target is a well-structured prompt around 1,000 tokens that gives the model enough product context, safety expectations, and workflow guidance to behave consistently across read-only, workspace-edit, and full-access sessions. See `plans/V0_2_4_SYSTEM_PROMPT_REFINEMENT_PLAN.md`.
+
+### Prompt Structure and Content
+
+- [x] **Restructure the prompt into clear sections.** Replace the current compact prompt with a polished, scannable structure that explains identity, operating principles, tool use, editing, safety, and response style in a predictable order.
+  - Keep headings short and model-friendly so the prompt is easy to follow during long sessions.
+  - Preserve the existing split between the reusable base prompt, user global instructions, and runtime constraints.
+  - Avoid duplicating long documentation that already lives in README or bundled docs.
+
+- [x] **Add enough product context for intuitive behavior.** Teach the model what Cassady is, how the terminal chat works, and what the user can see without over-explaining implementation details.
+  - Explain that tool calls, tool results, diffs, approvals, and streamed assistant text are visible in the transcript.
+  - Clarify that Cassady is a coding assistant for real project work, so it should inspect before changing files, make targeted edits, and summarize outcomes honestly.
+  - Include guidance for asking focused follow-up questions only when necessary, instead of over-planning or guessing.
+
+- [x] **Keep the prompt intentionally compact.** Aim for roughly 900-1,100 tokens for the normal effective system prompt, including runtime access-mode guidance but excluding user-provided global instructions.
+  - Prefer dense, high-signal instructions over broad lists of examples.
+  - Remove redundant wording when new guidance overlaps with existing safety or response rules.
+  - Add a lightweight test or snapshot check so future prompt changes do not accidentally grow far beyond the intended size.
+
+### Tool, Editing, and Safety Guidance
+
+- [x] **Improve tool-use instructions.** Make the prompt explicit about when to read, grep, edit, write, and shell while still letting the model choose the right tool for the task.
+  - Encourage targeted inspection before edits and `grep`/search before opening large or unknown files.
+  - Explain that the model should request tools directly when useful; Cassady will enforce access policy, denials, and approval prompts at runtime.
+  - Remind the model not to claim a tool succeeded until the tool result confirms it.
+
+- [x] **Sharpen editing guidance.** Make file-change behavior safer and more reliable, especially for exact-text edits.
+  - Prefer `edit` for focused modifications and `write` only for new files or intentional full rewrites.
+  - Instruct the model to keep replacements minimal, unique, and non-overlapping.
+  - Encourage running or suggesting relevant tests after meaningful code changes.
+
+- [x] **Make access-mode behavior easy for the model to follow.** Rewrite read-only, workspace-edit, and full-access guidance in plain language that maps directly to available tools.
+  - Keep workspace and bundled-doc boundaries clear.
+  - State that shell approval is handled by Cassady's UI rather than by asking for permission in chat.
+  - Preserve conservative behavior when a task requires permissions the current mode does not allow.
+
+### Validation and Documentation
+
+- [x] **Add prompt-focused tests.** Verify that the generated prompt includes the required sections, preserves global instructions, reflects the active access mode, and stays within the intended size range.
+  - Cover read-only, workspace-edit, and full-access effective prompts.
+  - Include a regression check for prompt ordering so runtime constraints remain near the end.
+
+- [x] **Update user-facing references to global instructions.** Refresh docs only where needed to explain how `~/.cass/global.md` fits into the structured prompt.
+  - Avoid exposing the full internal prompt in documentation.
+  - Mention that user global instructions are respected unless they conflict with runtime safety constraints.
+
+## v0.2.3 — Documentation and README Refresh ✅ Completed
+
+This release focuses on making Cassady understandable, trustworthy, and easy to operate by rewriting the README and bringing all bundled documentation up to date with the current CLI behavior. The work should cover user-facing documentation only; broad CLI feature work and Windows-specific runtime improvements are deferred to the planned Windows CLI usability work. See `plans/V0_2_3_DOCUMENTATION_README_REFRESH_PLAN.md`.
 
 ### README Rewrite
 
@@ -156,9 +221,9 @@ This release focuses on making Cassady understandable, trustworthy, and easy to
   - Updating config or switching providers/models.
   - Resuming work after a failed provider request or cancelled turn.
 
-- [x] **Document platform expectations without duplicating future Windows work.** Add accurate notes for macOS, Linux, and Windows users while keeping deep Windows CLI usability improvements scoped to v0.2.4.
+- [x] **Document platform expectations without duplicating future Windows work.** Add accurate notes for macOS, Linux, and Windows users while keeping deep Windows CLI usability improvements scoped to the planned Windows CLI usability work.
   - Include path, shell, and environment-variable examples for each platform when documentation needs them.
-  - Mark known Windows limitations clearly until the v0.2.4 work lands.
+  - Mark known Windows limitations clearly until the planned Windows CLI usability work lands.
   - Avoid promising installer, package manager, or auto-update behavior that is not implemented.
 
 ### Documentation Quality and Maintenance
@@ -274,3 +339,101 @@ This release focuses on making Cass easier to interrupt, easier to audit, and sa
 - [x] **Edit diff output.** Make `edit` changes reviewable in the transcript.
   - First version: show a unified before/after diff after the edit is applied.
   - Later versions may add pre-apply approval, but that requires a confirmation flow between tools and the TUI.
+
+## Planned within the next major release
+
+These sections describe work Cassady intends to complete before or as part of the next major release, but which has not yet been assigned to a specific version. Scope, order, and version numbers may change.
+
+### Windows CLI Usability
+
+This work focuses on making Cassady feel reliable and native when the CLI is run on Windows. It covers runtime usability after `cass` or `cassady` is already available on the machine; installers, package managers, PATH setup, code signing, and update delivery are intentionally out of scope.
+
+#### Terminal Experience
+
+- [ ] **Make interactive rendering robust in Windows terminals.** Ensure chat, setup, confirmation prompts, streamed output, spinners, diffs, and tool summaries render cleanly in Windows Terminal, PowerShell, Command Prompt, and common VS Code integrated terminals.
+  - Enable or gracefully detect ANSI/VT support instead of emitting broken escape sequences.
+  - Respect `NO_COLOR`, non-interactive output, redirected stdout/stderr, and narrow terminal widths.
+  - Avoid relying on glyphs, emoji, box drawing, or cursor control sequences that render poorly on default Windows fonts.
+  - Keep wrapping and cursor positioning correct for multi-line input, Markdown output, and long tool-call summaries.
+
+- [ ] **Harden keyboard handling on Windows.** Make the TUI and prompts respond predictably to Windows console input events.
+  - Verify `Enter`, `Backspace`, `Delete`, arrow keys, `Home`, `End`, `PageUp`, `PageDown`, `Tab`, and paste behavior.
+  - Preserve existing `Ctrl-C` cancellation semantics and handle `Ctrl-Break`/console close events gracefully where supported.
+  - Ensure `Esc` cancellation and prompt dismissal work consistently across PowerShell, Command Prompt, and Windows Terminal.
+
+- [ ] **Improve plain CLI output for Windows users.** Commands such as `cass check`, setup diagnostics, validation errors, and usage text should remain readable without a fully interactive terminal.
+  - Prefer actionable Windows examples using PowerShell syntax when the current platform is Windows.
+  - Avoid POSIX-only command snippets in runtime guidance unless explicitly labeled.
+  - Keep error messages copy/paste-friendly and free of terminal control characters when output is redirected.
+
+#### Windows Paths and Files
+
+- [ ] **Support Windows path syntax everywhere the CLI accepts paths.** Normalize and validate paths consistently across arguments, tool calls, diffs, session metadata, and model-visible file references.
+  - Handle drive-letter paths such as `C:\Users\name\project`, rooted paths such as `\temp`, UNC paths such as `\\server\share\repo`, and mixed `/`/`\` separators.
+  - Preserve user-facing paths in a readable Windows form while using canonicalized paths for safety decisions.
+  - Avoid treating `:` in drive letters as URL schemes or command separators.
+  - Add tests for relative path resolution from Windows workspaces and for paths containing spaces, apostrophes, parentheses, brackets, and non-ASCII characters.
+
+- [ ] **Respect Windows filesystem semantics in workspace policy.** Keep read, write, edit, and shell safety checks correct on NTFS and common Windows filesystems.
+  - Account for case-insensitive path comparisons, symlinks, junctions, directory symlinks, and network shares.
+  - Prevent workspace escapes through `..`, junctions, symlink targets, alternate path spellings, and UNC aliases.
+  - Handle reserved device names, trailing dots/spaces, invalid filename characters, and long-path edge cases with clear errors.
+  - Preserve current access modes (`read-only`, `workspace-edit`, `full-access`) with Windows-specific authorization tests.
+
+- [ ] **Handle line endings and encodings cleanly.** Make file reads, edits, diffs, and generated files predictable on Windows projects.
+  - Preserve existing CRLF/LF style when editing files where practical.
+  - Render diffs clearly even when files use CRLF line endings.
+  - Avoid corrupting UTF-8 with BOM, UTF-16, or non-UTF-8 files; detect unsupported text encodings and explain the limitation.
+  - Keep binary-file detection reliable for Windows executables, images, archives, and generated build artifacts.
+
+#### Shell and Process Integration
+
+- [ ] **Use the right shell behavior on Windows.** Make `shell` tool execution, approval prompts, command summaries, cancellation, and exit status reporting work with Windows process semantics.
+  - Prefer PowerShell-friendly examples and diagnostics while still supporting `cmd.exe`-style commands when users provide them.
+  - Quote paths with spaces safely and avoid POSIX-only escaping in Windows-generated commands.
+  - Surface the actual executable, working directory, exit code, stdout, and stderr in a way users can debug.
+  - Cancel long-running child processes cleanly, including process trees where possible.
+
+- [ ] **Normalize environment-variable handling.** Ensure provider API key checks, diagnostics, setup guidance, and spawned tools work with Windows environment conventions.
+  - Treat environment variable names consistently despite Windows case-insensitive lookup behavior.
+  - Show PowerShell examples such as `$env:OPENAI_API_KEY = "..."` for temporary values.
+  - Avoid relying on POSIX shell expansion, `export`, `$VAR`, or `~` in Windows-specific guidance.
+
+- [ ] **Support common Windows external commands and editors.** When Cassady suggests or launches helper commands, make the behavior compatible with typical Windows environments.
+  - Detect missing tools and explain alternatives rather than assuming Unix utilities are present.
+  - Avoid hard dependencies on `sh`, `bash`, `grep`, `sed`, `cat`, `less`, or `/tmp` during normal CLI operation.
+  - Respect configured editor/browser commands and quote file paths correctly when opening files or URLs.
+
+#### Config, State, and Session Usability
+
+- [ ] **Use Windows-appropriate runtime locations.** Keep config, logs, caches, sessions, temporary files, and diagnostics in locations that align with Windows conventions.
+  - Prefer the existing cross-platform directory abstraction where available, and verify behavior with `APPDATA`, `LOCALAPPDATA`, `TEMP`, and `USERPROFILE`.
+  - Expand `~` and environment-derived paths consistently in config values.
+  - Keep session history portable enough to display Windows paths without breaking transcript replay.
+
+- [ ] **Make diagnostics expose Windows-specific context.** Improve `cass check` and error reports so Windows users can understand terminal, filesystem, shell, and config problems quickly.
+  - Include OS, architecture, terminal detection, active shell, config path, workspace path, and access mode when relevant.
+  - Clearly distinguish provider/API-key failures from Windows runtime issues.
+  - Recommend Windows-native remediation steps without mentioning installation tasks.
+
+- [ ] **Keep aliases and command parsing consistent.** Ensure `cass` and `cassady` subcommands, flags, config overrides, and path arguments behave the same on Windows as on Unix-like systems.
+  - Validate quoting behavior for arguments containing spaces and backslashes.
+  - Ensure help text and examples do not imply shell features unavailable in PowerShell or Command Prompt.
+  - Keep machine-readable output stable across platforms when output is consumed by scripts.
+
+#### Verification and Documentation
+
+- [ ] **Add Windows-focused automated coverage.** Add unit and integration tests that exercise Windows path parsing, policy checks, config discovery, line endings, environment variables, and command rendering.
+  - Use platform-gated tests for behavior that can only run on Windows.
+  - Add platform-independent tests for Windows path strings where possible.
+  - Include regression tests for spaces in paths, UNC paths, CRLF edits, and workspace escape attempts.
+
+- [ ] **Run a manual Windows CLI acceptance pass.** Validate the release on a real Windows environment, not just cross-compilation.
+  - Test PowerShell, Command Prompt, Windows Terminal, and VS Code integrated terminal.
+  - Exercise interactive chat, first-run setup, `cass check`, tool approvals, file read/edit/diff, shell cancellation, and redirected output.
+  - Record any unsupported terminal or shell behavior as explicit known limitations.
+
+- [ ] **Update runtime documentation for Windows usage.** Refresh README and bundled docs with Windows-specific CLI usage guidance while avoiding installation instructions.
+  - Document PowerShell environment-variable examples, path examples, terminal expectations, and known limitations.
+  - Include troubleshooting for broken colors, bad wrapping, path authorization failures, CRLF diffs, and missing Unix helper commands.
+  - Keep all Windows guidance consistent with existing access modes and safety policies.

SECURITY.md

@@ -0,0 +1,64 @@
+# Security Policy
+
+## Supported Versions
+
+Security updates are provided for the latest released version of Cassady. If you are using an older version, please upgrade to the latest release before reporting an issue, unless the issue also affects the latest release.
+
+| Version | Supported |
+| ------- | --------- |
+| Latest | ✅ |
+| Older releases | ❌ |
+
+## Reporting a Vulnerability
+
+Please do **not** report security vulnerabilities in public GitHub issues, discussions, or pull requests.
+
+To report a vulnerability, use GitHub's private vulnerability reporting for this repository:
+
+1. Open the repository on GitHub.
+2. Go to **Security** → **Report a vulnerability**.
+3. Include as much detail as you can about the issue, impact, affected versions, and steps to reproduce.
+
+## What to Include
+
+Helpful reports include:
+
+- A description of the vulnerability and likely impact.
+- Steps to reproduce or a minimal proof of concept.
+- The Cassady version, operating system, shell, and terminal environment.
+- Relevant configuration details with secrets removed.
+- Any known mitigations or workarounds.
+
+Do not include live API keys, tokens, private prompts, or sensitive project files in a report. Redact secrets before sharing logs or configuration.
+
+## Response Expectations
+
+After a report is received, the maintainer will aim to:
+
+- Acknowledge the report within 7 days.
+- Confirm whether the issue is in scope and reproducible.
+- Provide status updates when there is meaningful progress.
+- Coordinate disclosure timing before publishing details publicly.
+
+Security fixes may be released as patch versions when appropriate. Public disclosure should wait until a fix or mitigation is available, unless otherwise coordinated with the maintainer.
+
+## Scope
+
+Examples of in-scope issues include vulnerabilities in Cassady that could:
+
+- Bypass documented access modes, approval prompts, or workspace boundaries.
+- Cause unintended file reads, writes, edits, or shell command execution.
+- Leak API keys, provider credentials, chat history, or local configuration.
+- Corrupt or expose session data stored under `~/.cass`.
+- Introduce unsafe behavior in bundled release artifacts.
+
+Out-of-scope issues generally include:
+
+- Vulnerabilities in third-party model providers or APIs not controlled by this project.
+- Prompt-injection behavior that does not bypass Cassady's documented safety controls.
+- Issues that require a compromised local machine, shell, dependency cache, or provider account.
+- Reports against unsupported older versions that are fixed in the latest release.
+
+## Safe Harbor
+
+Good-faith security research is welcome. Please avoid privacy violations, data destruction, service disruption, and accessing data that does not belong to you. If you follow this policy and make a good-faith effort to avoid harm, the maintainer will not pursue legal action for your research.

docs/README.md

@@ -6,11 +6,12 @@ Cassady tools may list, search, and read this directory. Mutating tools are bloc
 
 ## Contents
 
-- [Commands](commands.md): CLI forms, global flags, in-chat commands, and keys.
+- [Commands](commands.md): CLI forms, global flags, `cass update`, in-chat commands, and keys.
 - [Configuration](configuration.md): `~/.cass` files, setup, precedence, schema examples, and validation.
 - [Providers and models](providers.md): built-in OpenAI-compatible providers, custom endpoints, model discovery, and reasoning metadata.
 - [Access modes and tool safety](access-modes.md): what tools can read, write, edit, and run in each mode.
+- [Experimental Rust embedding API](embedding.md): import Cassady from Rust, start headless sessions, stream events, and handle approvals.
 - [Workflows](workflows.md): common ways to inspect code, apply edits, run checks, switch models, and resume chats.
 - [Troubleshooting](troubleshooting.md): symptoms, likely causes, fixes, and verification commands.
-- [Platform notes](platforms.md): macOS, Linux, and Windows environment/path notes.
+- [Platform notes](platforms.md): macOS, Linux, Windows, release artifact, and update notes.
 - [Glossary](glossary.md): short definitions for Cassady terms.

docs/commands.md

@@ -9,10 +9,11 @@ cass [OPTIONS]
 cassady [OPTIONS]
 cass check [OPTIONS]
 cass setup [OPTIONS]
+cass update [OPTIONS]
 cass --resume [CHAT_ID]
 ```
 
-Run `cass --help`, `cass check --help`, or `cass setup --help` for the help generated by the current binary.
+Run `cass --help`, `cass check --help`, `cass setup --help`, or `cass update --help` for the help generated by the current binary.
 
 ## Startup behavior
 
@@ -61,10 +62,37 @@ Missing API keys for inactive providers are warnings. A missing active API key i
 
 Runs the interactive setup wizard in a terminal. It configures OpenAI-compatible providers, API key environment-variable references, and first models. It updates `config.json`, `providers.json`, and `models.json` while preserving unrelated entries where possible.
 
+### `cass update`
+
+Checks official GitHub releases for Cassady, including Cassady prereleases, and updates the current install directory. The updater runs before provider/model config is loaded, so it can be used even if `~/.cass` is missing or invalid.
+
+By default, Cassady selects the matching prebuilt archive for the current platform, downloads the archive and `.sha256` file, verifies SHA-256, stages both `cass` and `cassady`, and replaces same-directory binaries with rollback backups. If no prebuilt archive is available, it can build from the selected release source when you choose source mode.
+
+Useful options:
+
+- `--check`: check the selected release without installing.
+- `--dry-run`: show the selected release, mode, asset, and install plan without downloading or installing.
+- `--yes` / `-y`: accept default prompts for non-interactive use.
+- `--prebuilt`: require a matching prebuilt archive.
+- `--source`: build from release source even when a prebuilt archive exists.
+- `--to TAG`: use a specific release tag such as `v0.2.7`.
+
+Examples:
+
+```sh
+cass update --check
+cass update --dry-run
+cass update
+cass update --source
+```
+
+The updater does not invoke `sudo` or administrator prompts. If the install directory is not writable, rerun the update from an install location you own or update through the same package manager or manual process you originally used.
+
 ## In-chat commands
 
 Type `/` to open command autocomplete.
 
+- `/branch` or `/restore`: open the branch/restore menu for the current conversation family.
 - `/model <model>`: switch the model for future turns. Autocomplete lists models from `~/.cass/models.json`.
 - `/new`: create a new chat for the current directory.
 - `/resume <chat>`: resume a saved chat from the current directory. Autocomplete lists matching chats.
@@ -86,8 +114,13 @@ Local commands can be used only when the agent is idle.
 - `y`: approve a pending tool approval prompt.
 - `n` or `Esc`: deny a pending tool approval prompt.
 - `Esc`: request cancellation while a turn is running.
+- `Esc` twice while idle: open the branch/restore menu without discarding draft input.
 - `Ctrl-C`: request cancellation while busy; press twice within 1.5 seconds to exit.
 
+## Branch/restore notes
+
+The branch/restore menu lists related conversations plus checkpoints for user messages, assistant messages, tool-call requests, and tool results. Selecting a checkpoint creates a new branch JSONL conversation and leaves the source conversation unchanged. Conversation-only branching leaves files untouched; branch-plus-file restore applies Cassady's tracked `write`/`edit` snapshots and skips unsafe hash conflicts.
+
 ## Output notes
 
 Tool calls are shown compactly by default. Press `Ctrl-O` to expand full tool output. Provider-streamed reasoning is hidden by default unless `show_reasoning` is enabled in config or toggled at runtime.

docs/configuration.md

@@ -5,7 +5,7 @@ Cassady reads user-editable config files from `~/.cass`.
 - `config.json`: user preferences, active defaults, and compatibility fields.
 - `providers.json`: provider connection definitions.
 - `models.json`: model metadata.
-- `global.md`: optional global instructions included in new chats.
+- `global.md`: optional global instructions included in new chat system prompts when they fit the active request; they cannot override access modes, tool denials, approvals, or workspace boundaries.
 - `conversations/`: saved JSONL chats.
 - `docs/`: bundled docs installed from the current binary.
 

docs/embedding.md

@@ -0,0 +1,98 @@
+# Experimental Rust embedding API
+
+Cassady v0.2.6 includes an experimental Rust API for running headless agent sessions from another Rust program. The API is intended for early integrations and may change before Cassady declares a stable library contract.
+
+The embedding API uses the same provider configuration, global instructions, prompts, access modes, tools, and JSONL conversation storage as the `cass` terminal UI. By default it reads and writes under `~/.cass`, so run `cass setup` first or create compatible `config.json`, `providers.json`, and `models.json` files programmatically.
+
+## Minimal example
+
+```rust
+use cassady::prelude::*;
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    let session = SessionBuilder::new()
+        .cwd(std::env::current_dir()?)
+        .access_mode(AccessMode::ReadOnly)
+        .build()
+        .await?;
+
+    let mut turn = session
+        .start_turn("Summarize this project in a few sentences.")
+        .await?;
+
+    while let Some(event) = turn.next_event().await? {
+        match event {
+            Event::AssistantChunk(text) => print!("{text}"),
+            Event::Finished => break,
+            _ => {}
+        }
+    }
+
+    let session = turn.finish().await?;
+    eprintln!("\nResume chat with: cass --resume {}", session.id());
+    Ok(())
+}
+```
+
+Add Cassady from a git checkout or path dependency, and ensure your application runs on Tokio.
+
+## Creating or resuming sessions
+
+Use `SessionBuilder` to set host-controlled options:
+
+```rust
+let session = SessionBuilder::new()
+    .config_root("/tmp/my-cass-root")
+    .cwd("/path/to/workspace")
+    .access_mode(AccessMode::WorkspaceEdit)
+    .model("my-model")
+    .base_url("https://provider.example/v1")
+    .api_key_env("MY_PROVIDER_KEY")
+    .build()
+    .await?;
+
+let resumed = SessionBuilder::new()
+    .cwd("/path/to/workspace")
+    .resume(session.id())
+    .await?;
+```
+
+`build()` is equivalent to `new_session()`. Resumed and new sessions use Cassady's normal `conversations/*.jsonl` files, so CLI and embedded sessions can interoperate.
+
+## Events and approvals
+
+`Session::start_turn` consumes the session and returns a `Turn`. This type design prevents overlapping turns for the same session. Call `turn.finish().await?` after receiving `Event::Finished` to recover the updated `Session`.
+
+Important events include:
+
+- `AssistantChunk` and `ReasoningChunk`
+- `ToolCallStarted`, `ToolOutputChunk`, and `ToolResult`
+- `ApprovalRequested` and `ApprovalResolved`
+- `Status`
+- `Finished`
+
+When a tool needs approval, decide in host code:
+
+```rust
+while let Some(event) = turn.next_event().await? {
+    match event {
+        Event::ApprovalRequested(request) => {
+            eprintln!("approval needed for {}: {}", request.name, request.reason);
+            turn.deny(&request.request_id)?;
+        }
+        Event::Finished => break,
+        _ => {}
+    }
+}
+```
+
+The approval policy is the same as the TUI: shell is unavailable in `read-only`, requires approval in `workspace-edit`, and runs directly in `full-access` unless destructive-operation confirmation is enabled.
+
+## Cancellation
+
+Dropping a `Turn` aborts the underlying task. Prefer `turn.cancel().await?` when you want Cassady to repair the conversation with cancellation records before returning the session.
+
+## Current limitations
+
+The v0.2.6 API is intentionally small and experimental. It does not include custom provider traits, custom tools, plugin loading, multi-agent orchestration, background daemons, task queues, or a synchronous/blocking wrapper.

docs/glossary.md

@@ -14,7 +14,7 @@
 
 **Exact edit**: An `edit` tool replacement where each `old_text` must match exactly once in the original file before anything is written.
 
-**Global instructions**: Optional text in `~/.cass/global.md` included in new chat system prompts.
+**Global instructions**: Optional text in `~/.cass/global.md` included in new chat system prompts. Cassady follows these instructions when they fit the active request, but they cannot override runtime safety constraints such as access modes, tool denials, approvals, or workspace boundaries.
 
 **Model metadata**: The `models.json` entry describing a model id, owning provider, display name, context limits, tool/streaming support, and reasoning behavior.
 

docs/platforms.md

@@ -52,9 +52,22 @@ That directory contains `config.json`, `providers.json`, `models.json`, `global.
 ## Non-interactive contexts
 
 - `cass check` is suitable for scripts and CI because it prints text and exits non-zero on errors.
+- `cass update --check` and `cass update --dry-run` are suitable for scripts that only need release status or an install plan.
+- `cass update --yes` accepts default prompts for scripted updates, but still fails instead of escalating privileges when the install directory is not writable.
 - `cass setup` requires an interactive terminal.
 - `cass` chat is an interactive terminal UI.
 
-## Release artifacts
+## Release artifacts and updates
 
-When using release archives, each archive contains both `cass` and `cassady`. Put the extracted binaries somewhere on your `PATH` or run them by explicit path. Cassady itself does not install, update, or manage PATH entries.
+When using release archives, each archive contains both `cass` and `cassady`. Put the extracted binaries somewhere on your `PATH` or run them by explicit path.
+
+`cass update` can update release-archive installs from official GitHub releases. It supports the same prebuilt targets as the release process:
+
+- macOS Apple Silicon: `aarch64-apple-darwin`
+- Linux x86_64: `x86_64-unknown-linux-gnu`
+- Linux ARM64: `aarch64-unknown-linux-gnu`
+- Windows x86_64: `x86_64-pc-windows-gnu`
+
+On macOS and Linux, the updater replaces same-directory `cass` and `cassady` binaries with backups and rollback on failure. On Windows, replacing a running `.exe` is more constrained; if automatic replacement is unavailable, Cassady leaves staged files in place and reports manual copy guidance instead of partially modifying the install.
+
+If Cassady is installed through a package manager in the future, prefer that package manager's update command instead of `cass update`.

docs/troubleshooting.md

@@ -143,6 +143,37 @@ Likely cause: Windows CRLF line endings or invisible whitespace differences.
 
 Fix: re-read the exact target region and preserve the line endings in `old_text`, or use a smaller unique snippet.
 
+## Branch/restore file conflicts
+
+Symptom: branch-plus-file restore reports conflicts or skips paths.
+
+Likely cause: the file changed outside Cassady after the tracked `write`/`edit`, the file is unsupported for snapshots, or the change came from a shell command or manual editor rather than a Cassady file tool.
+
+Fix: review the restore preview, inspect conflicted files manually, and rerun the menu with conversation-only branching if you only need to revisit the chat. Cassady will not overwrite unknown current content by default. Open the branch/restore menu again with double `Esc` or `/branch` to switch back to the original branch.
+
+## Update command problems
+
+Symptom: `cass update` cannot complete.
+
+Likely causes and fixes:
+
+- Network or GitHub API failure: retry later or verify proxy/firewall settings.
+- No matching prebuilt archive: use `cass update --source` if you have Rust installed, or download the release archive manually for a supported target.
+- SHA-256 mismatch: do not install the archive. Retry the update; if it repeats, check the GitHub release page before proceeding.
+- Missing Rust toolchain in source mode: install Rust/Cargo yourself, then rerun `cass update --source`. Cassady does not install Rust automatically.
+- Non-writable install directory: update through the original install method, move Cassady to a directory you own, or manually replace the binaries. Cassady does not run `sudo` for you.
+- PATH conflict: `cass update` updates the current executable directory. Run `which cass` / `which cassady` on macOS/Linux or `Get-Command cass` in PowerShell to confirm which binary your shell starts.
+- Windows replacement limitation: if Cassady reports that automatic replacement is unavailable, use the staged file paths it prints and copy them after the running process exits.
+
+Useful checks:
+
+```sh
+cass update --check
+cass update --dry-run
+cass --version
+cassady --version
+```
+
 ## Terminal rendering problems
 
 Symptom: the UI appears garbled or keys do not behave as expected.

docs/workflows.md

@@ -103,6 +103,16 @@ Inside the UI:
 
 This creates a new chat for the same cwd and model while preserving your current configuration.
 
+## Branch or restore a conversation point
+
+Press `Esc` twice while idle, or type:
+
+```text
+/branch
+```
+
+Use the menu to select a related branch or a checkpoint from a user message, assistant message, tool-call request, or tool result. Branching creates a new chat from that point and leaves the original chat available in the same menu. Choose conversation-only branching to leave files untouched, or choose branch-plus-files to restore Cassady-tracked `write`/`edit` snapshots with conflict checks.
+
 ## Check status
 
 ```text

examples/headless_agent.rs

@@ -0,0 +1,33 @@
+use cassady::prelude::*;
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    let session = SessionBuilder::new()
+        .cwd(std::env::current_dir()?)
+        .access_mode(AccessMode::ReadOnly)
+        .build()
+        .await?;
+
+    let mut turn = session
+        .start_turn("Summarize this project in a few sentences.")
+        .await?;
+
+    while let Some(event) = turn.next_event().await? {
+        match event {
+            Event::AssistantChunk(text) => print!("{text}"),
+            Event::ApprovalRequested(request) => {
+                eprintln!(
+                    "approval requested for {}: {}; denying in this example",
+                    request.name, request.reason
+                );
+                turn.deny(&request.request_id)?;
+            }
+            Event::Finished => break,
+            _ => {}
+        }
+    }
+
+    let session = turn.finish().await?;
+    eprintln!("\nResume chat with: cass --resume {}", session.id());
+    Ok(())
+}

plans/V0_2_4_SYSTEM_PROMPT_REFINEMENT_PLAN.md

@@ -0,0 +1,499 @@
+# v0.2.4 System Prompt Refinement Implementation Plan
+
+## Goal
+
+v0.2.4 refines Cassady's generated system prompt so the model receives clearer, more intuitive operating instructions without turning the prompt into a long manual. The effective prompt should explain Cassady's role, terminal transcript behavior, tool use, editing expectations, runtime safety constraints, and response style in a structured way that models can follow reliably.
+
+Success statement:
+
+> A normal effective system prompt, excluding user-provided global instructions, is roughly 900-1,100 tokens and consistently guides the model to inspect before editing, use tools directly when useful, respect access modes, make targeted file changes, and finish each turn with an honest concise response.
+
+## Scope
+
+### In scope
+
+- Rewrite `src/prompt.rs` prompt text into a clearer sectioned structure.
+- Preserve the existing prompt-generation model:
+  - `build_base_system_prompt(global)` creates reusable conversation-level instructions.
+  - `build_effective_system_prompt(...)` appends model/workspace/docs/access/tool runtime constraints.
+  - `~/.cass/global.md` text remains embedded as user global instructions when present.
+- Add product context that helps the model understand Cassady's terminal chat UX.
+- Improve guidance for tool selection, exact-text edits, use of shell, and test/summarization behavior.
+- Make access-mode guidance concise and easy to map to the currently allowed tools.
+- Add focused tests for prompt sections, ordering, global instructions, access modes, and approximate size.
+- Update docs only where they mention global instructions or prompt behavior.
+- Keep the prompt provider-agnostic and compatible with all OpenAI-compatible models Cassady supports.
+
+### Out of scope
+
+- Adding prompt templates, profile selection, or user-selectable prompt modes.
+- Exposing a CLI command to print or edit the full generated system prompt.
+- Changing the `~/.cass/global.md` file format or adding layered project instructions.
+- Changing access-policy enforcement, tool schemas, approval UI, or security decisions.
+- Adding new tools or changing tool argument formats.
+- Implementing automatic prompt compression or conversation summarization.
+- Maintaining separate prompts per provider/model family.
+- Stuffing large reference documentation, provider catalogs, or CLI help into the system prompt.
+
+## Context and Current State
+
+Relevant files:
+
+- `src/prompt.rs`: builds both the base and effective system prompts. The current prompt is short and functional but sparse.
+- `src/app.rs`: reads global instructions and stores the base prompt in new conversations.
+- `src/agent.rs`: calls `build_effective_system_prompt(...)` before provider requests.
+- `src/conversation.rs`: persists the base system prompt in the conversation record and reuses it when a chat is resumed.
+- `src/access.rs`: defines `read-only`, `workspace-edit`, and `full-access` modes.
+- `src/security.rs`: central policy for tool availability, read/write boundaries, shell approval, and denials.
+- `src/tools/*`: tool implementations and schemas for `ls`, `read`, `grep`, `write`, `edit`, and `shell`.
+- `docs/glossary.md`: defines global instructions as optional text in `~/.cass/global.md` included in new chat system prompts.
+- `tests/*`: no dedicated prompt tests exist yet; prompt behavior is only indirectly covered through agent/conversation tests.
+
+Current prompt behavior to preserve:
+
+- Cassady identifies itself as Cassady/Cass, a coding agent running in a terminal chat interface.
+- User global instructions are included only when non-empty after trimming.
+- Global instructions are subordinate to runtime safety constraints.
+- The effective prompt includes:
+  - model id,
+  - active access mode,
+  - launch working directory,
+  - bundled docs directory,
+  - allowed tools,
+  - access-mode-specific instructions,
+  - final response behavior.
+- Tool access is ultimately enforced by runtime policy, not by prompt wording alone.
+
+Current gaps:
+
+- The prompt is organized as numbered sections but does not fully explain Cassady's user-visible transcript model.
+- Tool and editing guidance is too compact for models that need stronger direction on when to inspect, search, edit, write, or run shell.
+- Access-mode text is accurate but can be made more direct and less repetitive.
+- There is no automated check that future prompt edits preserve required sections or stay near the intended size.
+- Documentation mentions global instructions, but not how they relate to runtime safety constraints in the refined prompt.
+
+## Design Principles
+
+1. **High signal, low bulk.** The prompt should contain the instructions most likely to improve model behavior, not a copy of the README.
+2. **Runtime policy remains authoritative.** Prompt text should guide the model, while `src/security.rs` and tool availability continue to enforce real permissions.
+3. **Structure beats length.** Use clear headings and dense paragraphs/bullets so models can find instructions during long sessions.
+4. **Tell the model what the user can see.** Explain streamed output, visible tool calls/results, approvals, and edit diffs so the assistant does not narrate inaccurately.
+5. **Prefer action over ceremony.** Encourage the model to use tools directly, inspect before changing files, and ask questions only when missing information materially blocks progress.
+6. **Make editing rules concrete.** Exact-text edits are a core reliability constraint and should be stated plainly.
+7. **Avoid provider-specific assumptions.** The prompt should work for small and large OpenAI-compatible models without relying on special model behavior.
+8. **Keep user instructions safe.** Global instructions are important, but they must never override runtime access modes, tool denials, or user requests in the active chat.
+
+## Prompt Architecture
+
+Keep the two-stage prompt generation, but make the internal structure more intentional.
+
+### Base prompt
+
+`build_base_system_prompt(global)` should contain stable instructions that are true for every session:
+
+1. Identity and role.
+2. Operating principles.
+3. User global instructions, when present.
+4. Tool-use behavior.
+5. Editing behavior.
+6. Response behavior.
+
+The base prompt is stored in the conversation when a chat is created. Because resumed chats reuse the stored base prompt, changing the base prompt affects new chats but not necessarily existing conversations. That behavior is acceptable and should be documented only if user-facing docs mention prompt changes.
+
+### Effective prompt
+
+`build_effective_system_prompt(...)` should append runtime-specific information near the end:
+
+1. Current runtime context:
+   - model,
+   - access mode,
+   - launch working directory,
+   - bundled docs directory,
+   - allowed tools.
+2. Access-mode rules for the active mode.
+3. Final reminder that runtime policy and tool results are authoritative.
+
+Runtime constraints should remain near the end so they are fresh in the model's context and can override earlier general instructions.
+
+### Numbering and headings
+
+Use stable Markdown-like headings rather than fragile sentence-only text. For example:
+
+```text
+# Cassady operating instructions
+
+## Role
+...
+
+## Working style
+...
+```
+
+Numbered headings are acceptable if tests are written against section names rather than exact numbers. Avoid deeply nested outlines.
+
+## Target Prompt Content
+
+The final wording can change during implementation, but it should cover the following content.
+
+### 1. Role
+
+Required ideas:
+
+- You are Cassady, also called Cass.
+- You are a coding assistant inside an interactive terminal chat.
+- You help with real project work: reading code, explaining behavior, editing files, and running relevant commands when allowed.
+- Work carefully and honestly; do not pretend to have inspected or changed files unless tool results confirm it.
+
+Avoid:
+
+- Overly broad claims such as being a general-purpose autonomous system.
+- Long branding language.
+- Any implication that prompt instructions can bypass runtime access policy.
+
+### 2. Working style
+
+Required ideas:
+
+- Prefer concrete progress over long speculative plans.
+- Inspect relevant files before making claims or edits.
+- Ask a focused follow-up question only when the task is ambiguous or blocked.
+- Keep explanations concise but include enough context for the user to review the work.
+- If the user's request is impossible in the current mode, explain the limitation and the next viable step.
+
+Suggested wording style:
+
+```text
+Make the smallest useful plan, then act. Do not over-plan routine code tasks. When information is missing, gather it with tools if possible; ask the user only when a choice or secret is genuinely required.
+```
+
+### 3. Transcript and UI awareness
+
+Required ideas:
+
+- Assistant text is streamed to the user.
+- Tool calls and tool results are visible in the transcript.
+- Edit diffs and approval prompts may be shown by Cassady's UI.
+- The model should request tools directly rather than asking for chat permission before every tool call.
+- Cassady handles access denials and approval UI separately.
+
+This section should reduce behaviors such as:
+
+- Saying "I will run X" and then not calling the tool.
+- Asking "May I read the file?" when the tool is available.
+- Claiming a shell command ran before its result arrives.
+- Repeating huge summaries of tool output that the user can already see.
+
+### 4. Tool use
+
+Required guidance by tool area:
+
+- `ls`: use for directory orientation.
+- `grep`: use before reading large or unknown files, or to locate definitions/usages.
+- `read`: use targeted reads for files or ranges that matter.
+- `edit`: use for focused changes to existing files.
+- `write`: use for new files or intentional full rewrites.
+- `shell`: use for tests, builds, formatting, diagnostics, or project commands when allowed and useful.
+
+General instructions:
+
+- Use tools when current filesystem state matters.
+- Prefer targeted inspection over guessing.
+- Batch related reads when possible, but avoid reading unrelated files.
+- Do not use shell for file inspection when `ls`/`grep`/`read` is safer and sufficient.
+- If a tool is denied, adapt to the denial instead of repeating the same call.
+
+### 5. Editing
+
+Required ideas:
+
+- Prefer `edit` for small and medium modifications to existing files.
+- `edit` replacements must use exact old text that appears uniquely in the original file.
+- Keep edits minimal, unique, and non-overlapping.
+- Combine related replacements for the same file in one `edit` call when practical.
+- Use `write` only for new files or full rewrites where that is safer and intentional.
+- After meaningful code changes, run relevant tests/formatters when allowed, or tell the user what should be run.
+- Mention changed files and verification in the final response.
+
+### 6. Safety and access modes
+
+The base prompt should state the general principle:
+
+- Follow runtime constraints and active access mode.
+- Do not try to bypass workspace boundaries, docs read-only rules, approvals, or tool denials.
+
+The effective prompt should include active-mode-specific guidance:
+
+#### read-only
+
+- Allowed tools should normally be `ls`, `read`, and `grep`.
+- Inspect only inside the launch workspace and bundled docs directory.
+- Do not request `write`, `edit`, or `shell`.
+- If changes or commands are needed, explain that a more permissive access mode is required.
+
+#### workspace-edit
+
+- Read/list/search inside the launch workspace and bundled docs directory.
+- Write/edit only inside the launch workspace.
+- Bundled docs are read-only.
+- Shell may be requested when useful, but Cassady will show the approval UI; do not ask for shell permission in chat first.
+- If a path escapes the workspace, choose an in-workspace alternative or explain the limitation.
+
+#### full-access
+
+- `ls`, `read`, `grep`, `write`, `edit`, and `shell` may be requested when needed.
+- Shell runs from the launch working directory.
+- Normal OS permissions still apply.
+- Bundled docs remain read-only for write/edit.
+- Even in full-access, keep changes targeted and avoid destructive commands unless the user explicitly requested them and the action is necessary.
+
+### 7. Final response behavior
+
+Required ideas:
+
+- Always end the turn with a concise user-facing response after tool work.
+- Do not finish with only tool calls.
+- Summarize what changed, where, and how it was verified.
+- If no changes were made, summarize findings or blockers.
+- Be honest about failures, denials, skipped tests, or assumptions.
+
+## Approximate Prompt Budget
+
+Target size: roughly 900-1,100 tokens for the normal effective system prompt, excluding user global instructions.
+
+Because Cassady does not currently include a tokenizer, implement a simple approximate check rather than adding a heavy tokenizer dependency unless the implementer strongly prefers otherwise.
+
+Recommended helper for tests:
+
+```rust
+fn approximate_token_count(s: &str) -> usize {
+    s.split_whitespace().count() * 4 / 3
+}
+```
+
+This heuristic is intentionally rough. The test should prevent accidental prompt bloat, not enforce an exact model-token count. Suggested limits:
+
+- Base prompt without global instructions: approximately 650-850 heuristic tokens.
+- Effective prompt in each access mode without global instructions: approximately 900-1,150 heuristic tokens.
+
+If the final prompt is slightly outside the target but demonstrably better, prefer readability over gaming the heuristic. The acceptance target should remain "around 1,000 tokens," not an exact failure-prone threshold.
+
+## Proposed Prompt Skeleton
+
+This skeleton is illustrative, not a required exact implementation.
+
+```text
+# Cassady operating instructions
+
+## Role
+You are Cassady, also called Cass, a coding assistant running in an interactive terminal chat. Help with real project work: inspect files, explain code, make targeted edits, and run useful commands when allowed. Work carefully and do not claim that files were read, commands ran, or edits succeeded until tool results confirm it.
+
+## Working style
+Make the smallest useful plan, then act. Prefer current project evidence over guesses. Use tools to gather missing filesystem context. Ask a focused follow-up question only when a user choice, secret, or missing requirement blocks progress. Keep user-facing explanations concise and practical.
+
+## Transcript and tools
+Assistant text is streamed. Tool calls, tool results, approvals, and edit diffs are visible in the transcript. Request tools directly when they are the right next step; Cassady enforces access policy and shows approval prompts separately. If a tool is denied or fails, adapt and explain the limitation.
+
+## Tool use
+Use ls for directory orientation, grep to locate text or inspect large/unknown areas, read for relevant files or ranges, edit for targeted changes, write for new files or intentional full rewrites, and shell for tests/builds/diagnostics when allowed. Prefer targeted reads and related batched reads over broad exploration.
+
+## Editing
+Inspect before editing. For edit, each old text must match exactly and uniquely in the original file; keep replacements minimal and non-overlapping. Do not use write for small changes to existing files. After meaningful code changes, run relevant verification when allowed or state what should be run.
+
+## User global instructions
+...
+
+## Runtime context
+Model: ...
+Access mode: ...
+Launch working directory: ...
+Bundled Cass docs directory: ...
+Allowed tools this turn: ...
+
+## Access rules for this session
+...
+
+## Final response
+End every turn with a concise response. Summarize changed files and verification, or summarize findings/blockers if no change was made. Do not end with only tool calls.
+```
+
+## Implementation Steps
+
+### 1. Inventory exact current behavior
+
+- Review `src/prompt.rs`, `src/agent.rs`, `src/app.rs`, `src/conversation.rs`, `src/access.rs`, `src/security.rs`, and `src/tools/schema.rs`.
+- Confirm current tool names and per-mode availability from `SecurityPolicy::tool_availability`.
+- Confirm docs directory behavior and blocked write roots from app/tool context construction.
+- Confirm how global instructions are loaded and trimmed.
+- Confirm how resumed conversations reuse the stored base prompt.
+
+### 2. Rewrite `build_base_system_prompt`
+
+- Replace the current compact numbered prompt with structured, high-signal sections.
+- Include identity, working style, transcript/tool visibility, general tool guidance, editing guidance, global instructions, and response behavior.
+- Preserve trimming behavior for `global`.
+- Keep global instructions clearly labelled and explicitly subordinate to runtime safety constraints.
+- Avoid including runtime-only values in the base prompt.
+
+### 3. Rewrite `build_effective_system_prompt`
+
+- Keep appending to `base.trim_end()`.
+- Add a clear `Runtime context` section with model, access mode, cwd, docs dir, and allowed tools.
+- Add one active-mode-specific `Access rules for this session` paragraph/bullet set.
+- Keep runtime constraints after global/base text.
+- Keep the final response reminder either at the end of the base prompt or at the end of the effective prompt. If it remains in the base prompt, add a short final runtime-policy reminder after access rules.
+
+### 4. Add prompt tests
+
+Create `tests/prompt_tests.rs` or add focused unit tests in `src/prompt.rs`. Prefer integration tests in `tests/prompt_tests.rs` so prompt behavior is covered through the public crate API if exports allow it.
+
+Recommended tests:
+
+1. **Base prompt has required sections.**
+   - Build with `None`.
+   - Assert it contains headings/phrases for role, working style, tools, editing, and final response behavior.
+   - Assert it does not contain runtime-only paths or model labels.
+
+2. **Global instructions are included and trimmed.**
+   - Build with whitespace-wrapped global text.
+   - Assert the exact trimmed content appears.
+   - Assert the prompt says global instructions cannot conflict with runtime safety constraints.
+
+3. **Empty global instructions are omitted.**
+   - Build with `Some("   \n")`.
+   - Assert the global-instructions heading is absent.
+
+4. **Effective prompt includes runtime context.**
+   - Use temporary or fixed paths for cwd/docs.
+   - Assert model, mode, cwd, docs dir, and allowed tools are present.
+
+5. **Each access mode gets correct instructions.**
+   - `read-only`: contains no write/edit/shell request guidance and says more permissive mode is needed for modifications.
+   - `workspace-edit`: says write/edit only inside workspace and shell approval is handled by Cassady UI.
+   - `full-access`: says all tools may be requested, shell runs from cwd, docs remain read-only.
+
+6. **Runtime constraints stay after global instructions.**
+   - Build base with global text, then effective prompt.
+   - Assert global text index is before runtime context index.
+   - Assert access rules appear after runtime context.
+
+7. **Prompt size remains intentional.**
+   - Build effective prompts for all modes without global instructions.
+   - Use the approximate token helper.
+   - Assert each is within the chosen guardrail, for example `800..=1250` approximate tokens.
+
+8. **Allowed tools list reflects caller input.**
+   - Pass a small custom tool list.
+   - Assert the rendered list matches it.
+
+Test guidance:
+
+- Avoid asserting the entire prompt as one giant snapshot unless the project already uses snapshot testing.
+- Prefer stable phrases and section headings so minor copy edits do not make tests brittle.
+- If a snapshot is added, keep it intentionally small or use one golden prompt plus semantic tests.
+
+### 5. Update docs references
+
+Update only docs that need to mention global instructions or prompt behavior.
+
+Likely files:
+
+- `docs/glossary.md`: expand `Global instructions` to say they are included in new chat system prompts and followed unless they conflict with runtime safety constraints.
+- `docs/configuration.md` or `README.md` only if they already mention `~/.cass/global.md` and need clarification.
+
+Do not publish the full internal system prompt in docs. It is implementation detail and will evolve.
+
+### 6. Run verification
+
+Required commands:
+
+```sh
+cargo fmt --check
+cargo test --locked --all-targets
+```
+
+If prompt tests use temp paths or platform-dependent path display, run on the current platform and avoid hardcoding separators where possible.
+
+## Tests
+
+Automated tests to add:
+
+- New prompt tests covering base prompt structure, global instruction behavior, effective runtime context, access-mode-specific wording, ordering, and approximate size.
+- Existing agent/conversation/tool tests should continue to pass unchanged.
+
+Manual checks:
+
+- Read one generated prompt for each access mode and verify it is understandable as prose.
+- Check that the prompt does not repeat the same instruction in several sections.
+- Check that docs/global-instruction wording matches the generated prompt.
+- Confirm a normal prompt is around 1,000 tokens by the chosen heuristic or an external tokenizer if one is available.
+
+## Documentation
+
+Required documentation updates are intentionally small:
+
+- `docs/glossary.md`: update the `Global instructions` definition.
+- Any existing README/configuration references to `~/.cass/global.md`: clarify that these instructions are included in new chat system prompts and cannot override safety constraints.
+
+No new user guide is required for this release unless implementation adds user-visible commands or configuration, which is out of scope.
+
+## Compatibility and Migration Notes
+
+- Existing conversations keep the base system prompt stored when they were created. The refined base prompt will apply to new conversations.
+- Runtime constraints are still generated at request time, so active access mode, cwd, docs dir, and allowed tools remain current for resumed chats.
+- `~/.cass/global.md` remains plain text and does not require migration.
+- No config schema changes are expected.
+- No provider/model configuration changes are expected.
+
+## Risks and Mitigations
+
+### Risk: prompt grows too large
+
+Mitigation:
+
+- Add a size guardrail test.
+- Keep docs/provider details out of the prompt.
+- Prefer compact instructions over long examples.
+
+### Risk: tests become brittle
+
+Mitigation:
+
+- Test for section presence and key behavior, not every exact sentence.
+- Keep exact string assertions limited to stable safety-critical phrases.
+
+### Risk: prompt implies permissions the runtime denies
+
+Mitigation:
+
+- Derive access-mode wording from `SecurityPolicy::tool_availability` and current policy behavior.
+- Include allowed tools in the runtime context.
+- Phrase guidance as "may request when allowed" rather than unconditional permission, except in mode-specific sections verified against code.
+
+### Risk: global instructions appear stronger than safety rules
+
+Mitigation:
+
+- Place global instructions in a clearly labelled section.
+- State that they are followed only when consistent with user requests and runtime safety constraints.
+- Add a test for this wording.
+
+### Risk: models ignore concise instructions
+
+Mitigation:
+
+- Use direct imperative wording.
+- Put runtime constraints near the end.
+- Avoid burying editing and safety rules in long paragraphs.
+
+## Acceptance Criteria
+
+- `src/prompt.rs` produces a structured, readable prompt with clear sections for role, working style, transcript/tool behavior, tool use, editing, runtime context, access rules, and final responses.
+- The effective prompt for each access mode is roughly 900-1,100 tokens excluding user global instructions, with an automated guardrail preventing major accidental bloat.
+- User global instructions are included only when non-empty, trimmed, clearly labelled, and subordinate to runtime safety constraints.
+- Runtime context includes model, access mode, launch cwd, bundled docs directory, and allowed tools.
+- Access-mode guidance matches current policy for `read-only`, `workspace-edit`, and `full-access`.
+- Editing instructions explicitly cover exact unique old text, minimal non-overlapping replacements, and using `write` only for new files or intentional rewrites.
+- Tool-use instructions explain when to use `ls`, `grep`, `read`, `edit`, `write`, and `shell` without over-constraining the model.
+- Final response guidance requires a concise user-facing response after tool work and honest reporting of verification or blockers.
+- Documentation references to global instructions are accurate and do not expose the full internal prompt.
+- `cargo fmt --check` and `cargo test --locked --all-targets` pass.

plans/V0_2_6_RUST_EMBEDDING_API_PLAN.md

@@ -0,0 +1,298 @@
+# v0.2.6 Rust Embedding API Implementation Plan
+
+## Goal
+
+v0.2.6 adds the first intentional public Rust API for embedding Cassady in another Rust project. A developer should be able to add Cassady as a dependency, configure a workspace/model/access mode, start a headless agent session, send user messages, receive streamed agent events, and handle approval requests without launching the interactive TUI.
+
+Success statement:
+
+> A small Rust program can import `cassady`, start a new headless session in a workspace, stream assistant/tool events from a turn, optionally approve shell requests, and inspect the updated conversation state using documented experimental APIs.
+
+## Scope
+
+### In scope
+
+- Add an experimental embedding API module with cohesive public types instead of requiring callers to wire together internal modules directly.
+- Support starting a new headless agent session from Rust code.
+- Support resuming an existing conversation by id when using Cassady's existing conversation storage.
+- Support running one turn at a time and streaming typed events to the host application.
+- Expose approval handling for tools that require host/user consent, especially shell in `workspace-edit` mode.
+- Reuse the existing config, provider, prompt, security, conversation, and tool execution paths used by the CLI/TUI.
+- Provide simple builder/options types for cwd, access mode, model/base URL/API key overrides, reasoning effort, and Cassady config root.
+- Add a crate-level `prelude` or clearly documented imports for common embedding use.
+- Add docs and examples that show a minimal headless integration.
+- Add integration tests that exercise the public API without a terminal.
+
+### Out of scope
+
+- Declaring the Rust API stable for semver compatibility. The API should be explicitly marked experimental in v0.2.6.
+- Replacing the CLI/TUI as the primary user interface.
+- Multi-agent orchestration, task queues, background daemons, schedulers, or distributed workers.
+- Custom model provider traits or non-OpenAI-compatible protocols.
+- User-defined custom tools or plugin loading.
+- A synchronous/blocking API. The first embedding surface can require Tokio.
+- Exposing low-level terminal UI internals as supported public API.
+- Publishing to crates.io as part of this release unless separately requested.
+
+## Context and Current State
+
+Cassady already builds a library crate:
+
+- `Cargo.toml` defines `[lib] name = "cassady" path = "src/lib.rs"`.
+- `src/lib.rs` currently re-exports many internal modules directly and exposes `run()` for the CLI/TUI path.
+- `src/agent.rs` contains the core async turn loop:
+  - `AgentSettings`
+  - `AgentEvent`
+  - `AgentCommand`
+  - `run_turn(...)`
+  - `run_turn_with_commands(...)`
+- `src/app.rs` owns interactive startup, TUI state, chat creation/resume, cancellation, approval UI, and local slash commands.
+- `src/conversation.rs` persists conversations as JSONL and can create/load/list chats.
+- `src/config.rs` loads providers, models, active defaults, API key references, access mode, tool limits, and docs paths.
+- `src/security.rs` centralizes access-mode decisions.
+- `src/tools/*` implements the same tools that headless sessions should use.
+
+The current crate can technically be imported, but the supported path is unclear: callers must know which internal modules to combine, how to create base prompts, how to load config safely, how to route approval commands, and how to consume events. v0.2.6 should add a thin, intentional API layer over these internals.
+
+## Design Principles
+
+1. **Thin wrapper over proven internals.** Reuse the same agent loop and policy code as the CLI so embedded behavior matches interactive behavior.
+2. **Explicitly experimental.** Make the new API useful without promising final naming or long-term stability yet.
+3. **Headless first.** The API should not depend on `ratatui`, terminal setup, crossterm event loops, or slash-command UI state.
+4. **Host owns presentation.** Embedded callers receive typed events and decide how to display assistant chunks, tool calls, approvals, and errors.
+5. **Safe defaults.** Default to `read-only`, environment-variable API keys, existing Cassady config files, and workspace-rooted paths.
+6. **Approval is part of the API.** Hosts must be able to approve or deny requests rather than having Cassady assume a TUI is present.
+7. **Keep the first surface small.** Prefer one clear session builder and one turn-running method over exposing every internal knob.
+
+## Design
+
+### Module layout
+
+Add a new module, for example:
+
+```rust
+pub mod embedding;
+pub mod prelude;
+```
+
+`src/embedding.rs` should be the supported experimental API. Existing internal modules can remain public in v0.2.6 for compatibility, but docs should steer new users toward `cassady::embedding` or `cassady::prelude`.
+
+Suggested public surface:
+
+```rust
+pub struct SessionBuilder { ... }
+
+pub struct Session { ... }
+
+pub struct SessionOptions { ... }
+
+pub struct Turn { ... }
+
+pub enum Event { ... }
+
+pub enum Command { ... }
+
+pub struct ConversationInfo { ... }
+```
+
+The exact names can change during implementation, but they should avoid leaking TUI-specific terms.
+
+### Builder and options
+
+Provide a builder that covers common embedding setup:
+
+```rust
+let mut session = cassady::embedding::SessionBuilder::new()
+    .cwd("/path/to/project")
+    .access_mode(AccessMode::WorkspaceEdit)
+    .model("accounts/fireworks/models/qwen3p7-plus")
+    .build()
+    .await?;
+```
+
+Builder responsibilities:
+
+- Resolve and canonicalize `cwd` like CLI startup.
+- Load config from the default Cassady root unless an explicit root/path is supplied.
+- Apply model/base URL/API key env overrides without requiring a `Cli` value from callers.
+- Resolve API key availability before starting a turn and return a useful error.
+- Install or locate bundled docs as needed by `Config::load` behavior.
+- Create the base system prompt with `~/.cass/global.md` when starting a new conversation.
+- Default access mode to config/default, then builder override, then `read-only` if no config exists.
+
+Avoid requiring callers to import or construct `cli::Cli`.
+
+### New and resumed sessions
+
+Support at least:
+
+```rust
+let session = SessionBuilder::new().cwd(".").new_session().await?;
+let session = SessionBuilder::new().cwd(".").resume("chat-id").await?;
+```
+
+A `Session` should expose lightweight metadata:
+
+```rust
+session.id();
+session.cwd();
+session.model();
+session.access_mode();
+session.conversation_path();
+```
+
+The conversation should continue to be persisted in the same JSONL format so CLI and library sessions can interoperate.
+
+### Running a turn
+
+Provide a headless one-turn API that streams events:
+
+```rust
+let mut turn = session.start_turn("Explain the crate layout").await?;
+while let Some(event) = turn.next_event().await? {
+    match event {
+        Event::AssistantChunk(text) => print!("{text}"),
+        Event::ApprovalRequested(request) => {
+            turn.approve(request.id).await?;
+        }
+        Event::Finished => break,
+        _ => {}
+    }
+}
+let session = turn.finish().await?;
+```
+
+Alternative designs are acceptable, such as returning `(EventStream, CommandSink)` plus a completion handle, as long as examples are simple and approval commands are supported.
+
+The wrapper can map `agent::AgentEvent` and `agent::AgentCommand` into public embedding types. It should avoid exposing internal channel mechanics unless that is the cleanest Tokio-native API.
+
+### Event model
+
+Expose typed events that are stable enough for hosts to build UI/logging around:
+
+- assistant text chunks
+- reasoning chunks, when provider/model returns them
+- tool call started
+- tool output chunk
+- tool result
+- approval requested
+- approval resolved
+- status
+- turn finished
+- error or turn failure
+
+The public event type can wrap or re-export `agent::AgentEvent` initially, but the plan should prefer a dedicated type if it prevents low-level internals from becoming accidental API.
+
+### Approval behavior
+
+Approval requests should include:
+
+- request id
+- tool call id
+- tool name
+- arguments
+- human-readable reason
+
+The host should be able to approve or deny by request id. If the host drops the turn or never responds, cancellation/drop behavior should be documented.
+
+For v0.2.6, keep approval policy aligned with `security.rs`:
+
+- `read-only`: shell unavailable.
+- `workspace-edit`: shell asks.
+- `full-access`: shell allowed.
+
+### Cancellation and drop behavior
+
+The TUI already cancels by aborting the agent task and repairing pending records. The embedding API should define a basic behavior:
+
+- Dropping an active turn should abort the underlying task if possible.
+- A simple explicit `cancel()` method is preferred if practical.
+- Conversation repair for cancelled turns can be minimal in v0.2.6, but pending tool calls must not corrupt resumed conversations.
+
+If full parity with the TUI cancellation path is too large, document the limitation and add tests for the supported behavior.
+
+### Error handling
+
+Use a public result alias such as:
+
+```rust
+pub type Result<T> = std::result::Result<T, Error>;
+```
+
+The first pass may wrap `anyhow::Error`, but public errors should include enough context for embedding callers to distinguish:
+
+- config load errors
+- missing API key
+- provider request errors
+- conversation load/create errors
+- active turn already running
+- approval request not found or already resolved
+
+Do not panic for ordinary configuration or runtime failures.
+
+### Examples
+
+Add at least one compilable example under `examples/`, for example `examples/headless_agent.rs`:
+
+```rust
+use cassady::prelude::*;
+
+#[tokio::main]
+async fn main() -> cassady::embedding::Result<()> {
+    let mut session = SessionBuilder::new()
+        .cwd(std::env::current_dir()?)
+        .access_mode(AccessMode::ReadOnly)
+        .build()
+        .await?;
+
+    let mut turn = session.start_turn("Summarize this project.").await?;
+    while let Some(event) = turn.next_event().await? {
+        if let Event::AssistantChunk(text) = event {
+            print!("{text}");
+        }
+    }
+    turn.finish().await?;
+    Ok(())
+}
+```
+
+The example should be honest about requiring configured providers and API keys.
+
+## Implementation Steps
+
+1. **Define the experimental API shape.** Add `src/embedding.rs` with builder, session, turn, event, command/approval, and result/error types.
+2. **Add non-CLI config loading helpers.** Refactor or add helpers in `src/config.rs` so library callers can apply overrides without constructing `cli::Cli`.
+3. **Extract chat creation/resume helpers.** Move reusable prompt/global/conversation setup out of `src/app.rs` into functions usable by both TUI and embedding API.
+4. **Wrap the existing agent loop.** Use `agent::run_turn_with_commands` internally and provide a host-friendly event stream plus approval methods.
+5. **Handle turn lifecycle.** Ensure a session cannot run overlapping turns unless explicitly supported; persist and return the updated conversation after a turn finishes.
+6. **Add cancellation/drop handling.** Provide at least a documented `cancel()` path and avoid leaving pending tool-call records in a corrupted state.
+7. **Add examples and docs.** Create a headless example and a bundled docs page for the experimental Rust API.
+8. **Update README and crate exports.** Add `embedding`/`prelude` exports and a short README section pointing to the new docs.
+9. **Test the public surface.** Add integration tests with a mock OpenAI-compatible server and temporary config/conversation roots.
+
+## Tests
+
+- Unit tests for builder option precedence: default config, explicit cwd, access mode, model, base URL, API key env, and config root.
+- Integration test that starts a new session and runs a turn against `wiremock`, asserting assistant chunks and persisted conversation records.
+- Integration test that resumes an existing conversation through the embedding API.
+- Integration test for approval flow in `workspace-edit` mode using a mock tool call that requests shell approval.
+- Test that read-only sessions do not expose write/edit/shell tools through the embedded turn.
+- Test that starting a second turn while one is active returns an error or is impossible by type design.
+- Example compilation through `cargo test --examples` or equivalent.
+
+## Documentation
+
+- Add `docs/rust-api.md` or `docs/embedding.md` describing the experimental API, setup requirements, minimal example, event loop, approval handling, and limitations.
+- Link the new page from `docs/README.md` and the README.
+- Document that the API is experimental in v0.2.6 and may change before a stable 1.0-style library contract.
+- Include a note that embedded sessions use the same `~/.cass` config and conversation storage by default.
+- Mention how hosts should run `cass setup` or provide config programmatically before using the API.
+
+## Acceptance Criteria
+
+- A Rust binary in `examples/` can import `cassady`, create a headless session, run a turn, and stream assistant output without launching the TUI.
+- Embedded sessions use the same provider, prompt, security, tool, and conversation paths as the CLI.
+- Approval requests can be approved or denied programmatically.
+- New public API docs and README links clearly label the surface experimental.
+- CLI/TUI behavior remains unchanged.
+- `cargo fmt` and `cargo test --locked --all-targets` pass.

plans/V0_2_7_SELF_UPDATE_COMMAND_PLAN.md

@@ -0,0 +1,390 @@
+# v0.2.7 Self-Update Command Implementation Plan
+
+## Goal
+
+v0.2.7 adds a polished `cass update` command that can update Cassady from official GitHub releases without requiring users to manually download archives, verify checksums, unpack binaries, or rebuild from source.
+
+Success statement:
+
+> A user can run `cass update`, see the available release, choose the recommended prebuilt binary or a source build fallback, and finish with updated `cass` and `cassady` commands in the same install location.
+
+## Scope
+
+### In scope
+
+- Add a `cass update` / `cassady update` subcommand.
+- Query official Cassady GitHub releases from `owenqwenstarsky/cassady`.
+- Compare the current binary version with the latest stable release.
+- Download and install the matching prebuilt archive when available.
+- Verify prebuilt archives with the shipped `.sha256` files before installing.
+- Offer a source-build path that downloads release source for the selected tag and builds local binaries.
+- Update both shipped binaries, `cass` and `cassady`, when possible.
+- Use interactive prompts by default with clear summaries, confirmations, progress, success, and recovery messages.
+- Provide non-interactive flags for check-only and yes-to-prompts usage.
+- Keep `cass update` independent of model/provider setup so updates work even when `~/.cass` is missing or broken.
+- Add tests for release parsing, target detection, asset selection, checksum validation, archive extraction safety, and install planning.
+- Update README and bundled docs.
+
+### Out of scope
+
+- Publishing through Homebrew, apt, winget, Scoop, npm, or other package managers.
+- Automatic background updates or prompts during normal chat startup.
+- Updating Cassady when it was installed by an external package manager that should own the install directory.
+- Privilege escalation, `sudo` automation, or administrator prompts.
+- Code signing, notarization, or signature verification beyond existing SHA-256 files.
+- Downgrading by default. Installing an older tag should require an explicit flag if supported.
+- Cross-compiling in source mode. Source builds target the current host platform only.
+
+## Context and Current State
+
+Relevant files:
+
+- `Cargo.toml`: package version and two binaries, `cass` and `cassady`.
+- `src/cli.rs`: Clap command definitions currently include `check` and `setup`.
+- `src/app.rs`: top-level command dispatch; update should run before setup/config loading.
+- `src/main.rs` and `src/bin/cassady.rs`: both call `cassady::run()`.
+- `README.md` and `docs/commands.md`: command documentation.
+- `docs/platforms.md` and `docs/troubleshooting.md`: platform and recovery guidance.
+- `AGENTS.md`: release artifacts use these names:
+  - `cassady-vX.Y.Z-aarch64-apple-darwin.tar.gz`
+  - `cassady-vX.Y.Z-x86_64-unknown-linux-gnu.tar.gz`
+  - `cassady-vX.Y.Z-aarch64-unknown-linux-gnu.tar.gz`
+  - `cassady-vX.Y.Z-x86_64-pc-windows-gnu.zip`
+
+Current releases include both `cass` and `cassady` in each archive plus one `.sha256` file per archive. The update command should reuse that release contract instead of inventing a new distribution format.
+
+## Design Principles
+
+1. **Boring and recoverable.** Updating should be explicit, easy to understand, and safe to interrupt before installation starts.
+2. **Use official release artifacts first.** Prefer prebuilt archives with SHA-256 verification; fall back to source builds when the user asks or no asset matches.
+3. **No surprise setup coupling.** Users should not need a configured provider, model, or API key to update the CLI.
+4. **Respect install ownership.** Do not auto-escalate privileges or overwrite package-manager-owned paths without clear user confirmation.
+5. **Both command names stay aligned.** If the user has both `cass` and `cassady` in the install directory, update them together.
+6. **Interactive by default, scriptable when requested.** The normal path should be friendly; flags should support CI/check scripts.
+7. **Fail closed on integrity.** Missing or mismatched checksums for prebuilt artifacts must stop installation.
+
+## User Experience
+
+### Default interactive flow
+
+```text
+$ cass update
+Cassady update
+
+Current version: v0.2.6
+Latest release:  v0.2.7
+Install path:    /usr/local/bin
+Recommended:     prebuilt aarch64-apple-darwin archive
+
+Update Cassady to v0.2.7? [Y/n]
+```
+
+If the user accepts, Cassady should show concise phases:
+
+```text
+Downloading cassady-v0.2.7-aarch64-apple-darwin.tar.gz ... 8.4 MB
+Downloading cassady-v0.2.7-aarch64-apple-darwin.tar.gz.sha256 ... done
+Verifying SHA-256 ... ok
+Preparing cass and cassady ... ok
+Installing to /usr/local/bin ... ok
+Verifying installed version ... cass 0.2.7
+
+Cassady is up to date.
+```
+
+If the current version is already latest:
+
+```text
+Cassady is already up to date.
+Current version: v0.2.7
+Latest release:  v0.2.7
+```
+
+### Prebuilt or source selection
+
+The default `auto` mode should choose the prebuilt release asset when a supported target is detected. If no matching prebuilt exists, prompt for source mode:
+
+```text
+No prebuilt archive is available for this platform.
+Build Cassady v0.2.7 from source instead? [Y/n]
+```
+
+If both paths are available and the user asks for source mode:
+
+```sh
+cass update --source
+```
+
+Cassady should confirm prerequisites before building:
+
+```text
+Source build requires cargo, rustc, and a working C toolchain.
+Build Cassady v0.2.7 from release source now? [Y/n]
+```
+
+### Useful flags
+
+Add a command shape like:
+
+```sh
+cass update [OPTIONS]
+```
+
+Suggested options:
+
+- `--check`: check GitHub for the latest release and print status without installing.
+- `--yes`: accept default prompts for non-interactive use.
+- `--prebuilt`: require a matching prebuilt archive; fail instead of falling back to source.
+- `--source`: build from release source even when a prebuilt archive exists.
+- `--to TAG`: install a specific release tag such as `v0.2.7`.
+- `--dry-run`: resolve the release, target, assets, and install path without downloading or installing.
+
+Optional later flags, only if implementation needs them:
+
+- `--stable-only`: ignore prerelease tags during latest-release selection if Cassady later publishes both stable and prerelease channels.
+- `--install-dir PATH`: install into an explicit directory. This should be advanced and carefully documented because it can conflict with PATH order.
+
+Avoid adding a public `--repo` override unless needed for testing; tests can inject a mock client instead.
+
+## Design
+
+### Module layout
+
+Add a focused update module:
+
+```rust
+pub mod update;
+```
+
+Suggested internal types:
+
+```rust
+pub struct UpdateOptions { ... }
+pub enum UpdateMode { Auto, Prebuilt, Source }
+pub struct ReleaseInfo { ... }
+pub struct ReleaseAsset { ... }
+pub struct PlatformTarget { ... }
+pub struct UpdatePlan { ... }
+pub enum InstallAction { Replace, AddCompanion, SkipMissingCompanion }
+```
+
+`src/cli.rs` should add an `Update` subcommand with parsed flags. `src/app.rs` should dispatch it before setup/config loading:
+
+```rust
+if let Some(Command::Update(args)) = cli.command {
+    return crate::update::run(args).await;
+}
+```
+
+This keeps update usable even when `Config::load()` would fail.
+
+### GitHub release discovery
+
+Use the GitHub Releases API with an explicit user agent:
+
+- Latest release: `GET https://api.github.com/repos/owenqwenstarsky/cassady/releases?per_page=30` and choose the highest semver non-draft tag, including prereleases because Cassady's current release process marks releases as prereleases.
+- Specific tag: `GET https://api.github.com/repos/owenqwenstarsky/cassady/releases/tags/{tag}`
+
+Parse:
+
+- `tag_name`
+- `name`
+- `draft`
+- `prerelease`
+- `assets[].name`
+- `assets[].browser_download_url`
+- `assets[].size`
+- `tarball_url` or `zipball_url` for source mode
+
+Use `semver` to compare `env!("CARGO_PKG_VERSION")` with release tags after stripping a leading `v`. Draft releases should never be selected. Prereleases should be eligible by default while Cassady's official releases are marked as prereleases.
+
+### Platform target mapping
+
+Map the running platform to release asset targets:
+
+| OS | Arch | Target | Archive |
+| --- | --- | --- | --- |
+| macOS | `aarch64` | `aarch64-apple-darwin` | `.tar.gz` |
+| Linux | `x86_64` | `x86_64-unknown-linux-gnu` | `.tar.gz` |
+| Linux | `aarch64` | `aarch64-unknown-linux-gnu` | `.tar.gz` |
+| Windows | `x86_64` | `x86_64-pc-windows-gnu` | `.zip` |
+
+Unsupported platforms should produce a clean message and offer source mode when possible.
+
+### Prebuilt update path
+
+For tag `vX.Y.Z` and target `TARGET`, find:
+
+```text
+cassady-vX.Y.Z-TARGET.tar.gz
+cassady-vX.Y.Z-TARGET.tar.gz.sha256
+```
+
+or on Windows:
+
+```text
+cassady-vX.Y.Z-x86_64-pc-windows-gnu.zip
+cassady-vX.Y.Z-x86_64-pc-windows-gnu.zip.sha256
+```
+
+Flow:
+
+1. Download archive and checksum into a temporary staging directory.
+2. Parse the `.sha256` file and verify that the checksum filename matches the downloaded archive name.
+3. Compute SHA-256 of the archive and compare exactly.
+4. Extract into staging using path traversal checks.
+5. Require the expected binaries:
+   - Unix: `cass`, `cassady`
+   - Windows: `cass.exe`, `cassady.exe`
+6. Run the staged `cass --version` or `cassady --version` when possible and confirm the expected version.
+7. Build an install plan for the current executable directory.
+8. Confirm the final plan with the user unless `--yes` was supplied.
+9. Replace binaries with backups and rollback on failure.
+10. Verify installed version after replacement when possible.
+
+Archive extraction must reject absolute paths, `..` components, symlinks that escape staging, and unexpected top-level layouts.
+
+### Source-build update path
+
+Source mode should still be tied to a GitHub release tag, not an arbitrary branch.
+
+Flow:
+
+1. Resolve the selected release tag.
+2. Download release source from `tarball_url` or `zipball_url` into staging.
+3. Extract with the same path traversal protections as prebuilt archives.
+4. Verify `Cargo.toml` version matches the selected tag.
+5. Run:
+
+   ```sh
+   cargo build --release --locked --bins
+   ```
+
+   from the extracted source tree.
+6. Locate built binaries under `target/release/`.
+7. Run staged `--version` checks.
+8. Install using the same installer path as prebuilt updates.
+
+Before source mode starts, check for `cargo` and `rustc` on PATH and show a clear error if they are missing. Do not attempt to install Rust automatically.
+
+### Install planning and replacement
+
+Determine the current executable path with `std::env::current_exe()`, then derive the install directory. The install plan should include:
+
+- current binary path
+- sibling `cass` path
+- sibling `cassady` path
+- which binaries currently exist
+- which binaries are writable
+- whether companion binaries will be updated, added, skipped, or blocked
+
+Recommended behavior:
+
+- Always update the currently running binary name.
+- If the sibling binary exists in the same directory, update it too.
+- If the sibling binary is missing and the directory is writable, ask whether to install it.
+- If a target path is not writable, stop with an actionable message. Do not invoke `sudo` or administrator prompts automatically.
+- Use backups such as `.cass-update-backup-v0.2.6-<timestamp>` during replacement.
+- If any replacement fails, restore backups before returning an error.
+
+Unix can generally replace a running executable via atomic rename. Windows cannot reliably overwrite the running `.exe`; implement one of these approaches during coding:
+
+1. Preferred: stage replacements and spawn a small PowerShell or `cmd` helper that waits for the current process to exit, moves files into place, and writes a log.
+2. Fallback: stage replacements and print exact manual copy commands if helper launch is unavailable.
+
+Document any Windows limitation honestly in `docs/platforms.md` and `docs/troubleshooting.md`.
+
+### Output and error style
+
+Keep output concise and user-facing:
+
+- Show current version, target version, install directory, selected mode, and asset/source name before changing files.
+- Show clear phase lines for download, verify, build, install, and final verification.
+- On failure, say whether anything was changed and where staging/backups are located.
+- If update cannot proceed because the install path is not writable, tell the user which path failed and suggest reinstalling through the same method they originally used.
+
+Avoid dumping raw GitHub JSON, backtraces, or Cargo logs unless the source build fails; in that case, preserve the final relevant Cargo output and staging path.
+
+## Dependencies
+
+Likely additions to `Cargo.toml`:
+
+- `semver` for version comparison.
+- `sha2` for SHA-256 verification.
+- `tar` and `flate2` for `.tar.gz` extraction.
+- `zip` for Windows release archives and GitHub source zips if used.
+
+Prefer small, well-maintained crates. Reuse existing `reqwest`, `tokio`, `serde`, and `serde_json`.
+
+## Implementation Steps
+
+1. Add CLI parsing for `cass update` and dispatch it before setup/config loading.
+2. Add `src/update.rs` with release API types, version comparison, and target detection.
+3. Implement GitHub release fetching with a testable client abstraction or injectable base URL for tests.
+4. Implement asset selection for current platform and update mode.
+5. Implement download, progress reporting, and checksum verification for prebuilt archives.
+6. Implement safe archive extraction and staged binary validation.
+7. Implement install planning from `current_exe()` and companion binary detection.
+8. Implement Unix replacement with backups and rollback.
+9. Implement Windows staged-helper replacement or a clearly documented manual fallback.
+10. Implement source mode: source download, version validation, prerequisite checks, `cargo build --release --locked --bins`, and staged binary validation.
+11. Polish interactive prompts and `--check`, `--dry-run`, `--yes`, `--prebuilt`, `--source`, and `--to` behavior.
+12. Update docs and release notes template expectations if needed.
+13. Add tests and run full verification.
+
+## Tests
+
+Add focused unit tests for:
+
+- parsing `vX.Y.Z` tags and comparing against the current version shape
+- ignoring drafts and prereleases where applicable
+- mapping supported and unsupported platform targets
+- matching asset and checksum filenames
+- parsing `.sha256` lines generated by the release process
+- rejecting checksum filename mismatches and digest mismatches
+- rejecting archive path traversal entries
+- planning installation when only `cass`, only `cassady`, or both binaries exist
+- refusing non-writable install targets in planning or dry-run mode
+- source mode validating that `Cargo.toml` version matches the selected tag
+
+Add integration-style tests with a mock HTTP server for:
+
+- already-up-to-date response
+- latest prebuilt update plan
+- missing prebuilt with source fallback prompt path, where build execution can be mocked
+- download checksum mismatch failure
+- successful staged install into a temporary directory using fake binaries
+
+Manual checks:
+
+```sh
+cargo fmt
+cargo test --locked --all-targets
+cargo run -- update --check
+cargo run -- update --dry-run --to v0.2.7
+```
+
+For a real release candidate, test from a temporary install directory before using `cass update` on the developer's normal binary.
+
+## Documentation
+
+Update:
+
+- `README.md`: mention `cass update` in install/update and everyday command sections.
+- `docs/commands.md`: full command reference, flags, interactivity, examples, and exit behavior.
+- `docs/platforms.md`: platform-specific update support and Windows replacement notes.
+- `docs/troubleshooting.md`: network failures, checksum mismatch, no matching prebuilt, missing Rust toolchain, non-writable install directory, PATH conflicts, and rollback recovery.
+- `docs/README.md`: add any new update-related links or summaries.
+
+Document that users should prefer the package manager's update mechanism if Cassady was installed through a package manager in the future.
+
+## Acceptance Criteria
+
+- `cass update --check` reports the current/latest release without reading provider config.
+- `cass update --dry-run` shows the selected release, mode, asset/source, and install plan without modifying files.
+- On supported release targets, `cass update` can download the matching official archive, verify SHA-256, stage both binaries, and update the current install directory.
+- `cass update --source` can download release source, build with `cargo build --release --locked --bins`, and install the resulting local binaries.
+- Checksum mismatch, missing assets, unsupported platforms, missing Rust toolchain, and non-writable install paths fail with clear messages and no partial install.
+- Existing `cass` and `cassady` sibling binaries remain version-aligned after a successful update.
+- README and bundled docs explain the command accurately.
+- `cargo fmt` and `cargo test --locked --all-targets` pass.

plans/V0_2_8_CONVERSATION_BRANCH_RESTORE_PLAN.md

@@ -0,0 +1,373 @@
+# v0.2.8 Conversation Branch and Restore Implementation Plan
+
+## Goal
+
+v0.2.8 adds an in-chat branch and restore menu opened by pressing `Esc` twice while Cassady is idle. Users should be able to browse the current conversation timeline, choose a checkpoint at a user message, assistant message, or tool call, and branch from that point without destroying the original conversation. They can optionally restore Cassady-tracked file edits to match the selected checkpoint, or branch the conversation only.
+
+Success statement:
+
+> A user can press `Esc` twice, select an earlier message or tool call, create a new branch from that point, optionally restore tracked file edits, and later open the same menu from either branch to switch or branch again from the related conversation history.
+
+## Scope
+
+### In scope
+
+- Add a double-`Esc` idle shortcut that opens a branch/restore menu, similar in feel to the double-`Ctrl-C` exit affordance.
+- Keep the existing busy `Esc` behavior for turn cancellation and approval denial.
+- Add a branch-aware conversation model that creates a new conversation file when restoring to a checkpoint instead of truncating or overwriting the original chat.
+- Let users browse checkpoints for:
+  - user messages,
+  - assistant messages,
+  - assistant tool-call requests,
+  - completed tool results.
+- Preserve valid model conversation structure when branching at or around tool calls.
+- Track file mutations made by Cassady's `write` and `edit` tools with enough before/after data to restore workspace files backward or forward between tracked checkpoints.
+- Offer restore actions that clearly separate conversation-only branching from conversation-plus-file restoration.
+- Allow users to return to the original conversation or other related branches by opening the menu again.
+- Add tests for branch metadata, checkpoint extraction, valid tool-call repair, file-edit journaling, workspace restore planning, conflict detection, and keybinding behavior where practical.
+- Update README and bundled docs for the new shortcut, branch semantics, file-restore limitations, and safety prompts.
+
+### Out of scope
+
+- Rewriting arbitrary filesystem changes made by shell commands, editors, package managers, test runners, or the user outside Cassady's `write`/`edit` tools.
+- Git integration, commits, worktrees, or automatic VCS operations.
+- A visual diff editor for every file restore. v0.2.8 should show a concise restore plan and rely on safe conflict checks.
+- Merging branches or replaying assistant responses across branches.
+- Branching while an agent turn is running.
+- Changing provider message semantics beyond the minimum repair needed for valid branched conversations.
+
+## Context and Current State
+
+Relevant files and behavior:
+
+- `src/app.rs` owns the TUI event loop, current conversation, transcript blocks, double-`Ctrl-C` exit behavior, busy `Esc` cancellation, local `/new` and `/resume` commands, and turn spawning.
+- `src/conversation.rs` stores conversations as append-only JSONL with `Meta`, `System`, `User`, `Assistant`, and `Tool` records. There is no branch metadata, checkpoint API, or rewrite/create-from-prefix helper yet.
+- `src/agent.rs` appends user, assistant, and tool records during a turn. Assistant records can contain multiple tool calls, while each tool result is a separate `Record::Tool`.
+- `src/tools/edit.rs` and `src/tools/write.rs` perform atomic writes and return user-visible summaries/diffs, but they do not persist before/after snapshots that can be used for later restore.
+- `src/ui/render.rs` renders the main chat. A branch menu should be integrated as an in-TUI modal or state, not by dropping into the setup/update prompt menu in `src/menu.rs`.
+
+The key design constraint is that restore must not mean destructive truncation. Selecting an old point creates a new branch conversation and leaves the source conversation available.
+
+## Design Principles
+
+1. **Branch, do not erase.** Restoring conversation state always creates or switches to a conversation branch; the original JSONL file remains intact.
+2. **Make file restore explicit.** Conversation branching is safe and default. File restoration is a separate confirmation because it changes the workspace.
+3. **Keep model history valid.** Branches created at tool boundaries must not leave assistant tool calls without corresponding tool records.
+4. **Track only what Cassady can prove.** File restore uses durable snapshots from `write`/`edit`; unsupported shell/user changes are detected or warned about, not guessed.
+5. **Recoverable navigation.** Every branch keeps parent/checkpoint metadata so the menu can show the related branch family and let users switch or branch again.
+6. **Small, testable modules.** Put checkpoint extraction, branch creation, and file restore planning in dedicated modules rather than expanding the TUI loop with business logic.
+
+## User Experience
+
+### Shortcut behavior
+
+- While idle, first `Esc` sets status text:
+
+  ```text
+  press Esc again within 1.5s to branch or restore
+  ```
+
+- A second `Esc` within the same window opens the branch/restore menu.
+- If the input box is non-empty, do not discard it silently. The first `Esc` should keep the input and show the same status; opening the menu should preserve the draft input if the user cancels.
+- While an agent turn is running, keep the current behavior: `Esc` cancels the active turn. Do not open the branch menu while busy.
+- During approval prompts, keep `Esc` as denial for the approval request.
+
+### Main branch menu
+
+The menu should show the current branch family, not only the current JSONL prefix:
+
+```text
+Branch / Restore
+
+Current chat: 2026-06-25-101533-abcd
+
+Branches
+  • current branch
+  • original chat from before restore
+  • earlier branch: "try without refactor"
+
+Timeline
+  1. user      Add tests for config loading
+  2. assistant Proposed plan
+  3. tool      read src/config.rs ✓
+  4. assistant Found config parser
+  5. tool      edit src/config.rs ✓  file: src/config.rs
+  6. user      Make it cleaner
+```
+
+Keyboard controls should be consistent with the main TUI: up/down or `j`/`k` move, Enter selects, `Esc` cancels, and an optional `/` filter can be deferred unless cheap.
+
+### Checkpoint actions
+
+After selecting a checkpoint, show an action menu:
+
+```text
+Branch from checkpoint
+
+Selected: tool edit src/config.rs at 10:24:11
+
+  1. Branch conversation only
+  2. Branch conversation and restore tracked file edits
+  3. Preview tracked file restore plan
+  4. Cancel
+```
+
+Default should be conversation-only. The branch should get a fresh chat id, copy records through the selected checkpoint, and append branch metadata. The status should make the branch explicit:
+
+```text
+branched 2026-06-25-110212-wxyz from 2026-06-25-101533-abcd at tool edit src/config.rs
+```
+
+### Switching among related branches
+
+Opening the menu from a branch should show its ancestors and descendants. Users can switch back to an existing branch without creating another branch:
+
+```text
+Switch to branch
+
+  original  2026-06-25-101533-abcd  18 records
+  current   2026-06-25-110212-wxyz  branched at tool edit src/config.rs
+```
+
+Switching branch changes the active conversation/transcript only. It should not change files unless the user explicitly chooses a file restore action.
+
+### File restore safety
+
+When the user chooses file restoration, show a concise plan before writing:
+
+```text
+Restore tracked file edits to selected checkpoint?
+
+Will update:
+  src/config.rs        current hash matches Cassady snapshot
+  src/app.rs           current hash differs; requires confirmation or skip
+
+Will delete:
+  src/generated.rs     created after the checkpoint by Cassady write
+
+Not tracked:
+  shell command outputs and manual edits cannot be restored automatically
+
+Proceed? [y/N]
+```
+
+Rules:
+
+- If the current file hash matches the expected tracked hash, restore automatically after confirmation.
+- If the file changed outside Cassady since the relevant snapshot, mark it as a conflict and default to skipping or cancelling the whole restore.
+- For files that did not exist at the target checkpoint, delete only if the current content hash matches the tracked created-file hash.
+- Never overwrite unknown current content without an explicit conflict confirmation.
+
+## Design
+
+### Conversation branch metadata
+
+Extend the conversation metadata in a backward-compatible way. One acceptable shape is adding optional fields to `Record::Meta` with `#[serde(default)]` and `skip_serializing_if`:
+
+```rust
+Record::Meta {
+    chat_id: String,
+    created_at: String,
+    model: String,
+    cwd: String,
+    parent_chat_id: Option<String>,
+    branch_from: Option<BranchPoint>,
+}
+
+struct BranchPoint {
+    chat_id: String,
+    record_index: usize,
+    tool_call_id: Option<String>,
+    checkpoint_label: String,
+}
+```
+
+Older conversations load with no parent. Descendants can be discovered by scanning `config.conversations_dir()` for `Meta.parent_chat_id` references.
+
+Add a `conversation::create_branch(...)` helper that:
+
+1. loads the source conversation,
+2. computes a valid record prefix for the selected checkpoint,
+3. writes a new JSONL file with a fresh chat id and branch metadata,
+4. preserves the original `System` prompt and source metadata needed for branch navigation,
+5. returns the new `Conversation` for the TUI to load immediately.
+
+Do not truncate or rewrite the source conversation.
+
+### Checkpoint extraction
+
+Add a focused module such as `src/branch.rs` or `src/conversation_branch.rs` with types like:
+
+```rust
+struct Checkpoint {
+    id: String,
+    chat_id: String,
+    record_index: usize,
+    tool_call_id: Option<String>,
+    kind: CheckpointKind,
+    label: String,
+    detail: String,
+    ts: Option<String>,
+}
+
+enum CheckpointKind {
+    User,
+    Assistant,
+    ToolCall,
+    ToolResult,
+}
+```
+
+Checkpoint rules:
+
+- A user checkpoint means the branch includes that user record.
+- An assistant checkpoint means the branch includes that assistant record. If the assistant requested tools, the branch helper must repair or omit incomplete tool-call state before the next provider turn.
+- A tool-result checkpoint means the branch includes records through that tool result.
+- A tool-call checkpoint without a completed result should branch to the state immediately before executing that tool call, represented by an assistant record plus synthetic denied/cancelled tool records for any required missing calls.
+
+Because OpenAI-compatible providers require every assistant tool call to receive a tool message before the next user message, branch creation must repair partial tool-call groups. Reuse or generalize the existing cancellation repair behavior in `src/app.rs` (`finalize_cancelled_turn` and pending tool-call handling) so branched conversations remain valid.
+
+### File edit journal
+
+Add a durable edit journal separate from model-visible conversation records, for example:
+
+```text
+~/.cass/file-edits/<chat_id>.jsonl
+~/.cass/file-snapshots/<chat_id>/<tool_call_id>/<hash>.bin
+```
+
+Journal entries should be written only for successful `write` and `edit` tool calls:
+
+```rust
+struct FileEditJournalEntry {
+    chat_id: String,
+    record_index: usize,
+    tool_call_id: String,
+    tool_name: String, // write | edit
+    path: PathBuf,
+    existed_before: bool,
+    existed_after: bool,
+    before_hash: Option<String>,
+    after_hash: Option<String>,
+    before_snapshot: Option<PathBuf>,
+    after_snapshot: Option<PathBuf>,
+    ts: String,
+}
+```
+
+Implementation approach:
+
+- Add a `file_edits` module that can capture before/after bytes, hash them, store snapshots, append journal entries, and build restore plans.
+- Pass chat id / record index / tool call id into tool execution context, or wrap `write`/`edit` execution in `agent.rs` so the agent captures before/after around successful file tools.
+- Store full bytes, not just unified diffs, so restore works both backward and forward.
+- Limit snapshots to regular files. If a path is a directory, symlink, binary too large, or otherwise unsafe, skip journaling and note that restore will not cover it.
+
+The first implementation can treat text and binary bytes uniformly for snapshot storage, while still using existing `write`/`edit` tools for text operations.
+
+### Restore planning
+
+File restore should compute a target workspace state from the selected checkpoint and branch lineage:
+
+1. Determine the selected checkpoint's branch lineage back to the root conversation.
+2. Load file-edit journal entries along that lineage up to the checkpoint.
+3. For every path touched by tracked edits in the relevant branch family, compute the desired state at the checkpoint:
+   - absent if no tracked edit existed before the checkpoint and the file was created later,
+   - the last `after_snapshot` at or before the checkpoint,
+   - the `before_snapshot` for paths whose first tracked edit happened after the checkpoint.
+4. Compare the current workspace file hash to the journal's expected current hash when possible.
+5. Produce a restore plan with actions: write snapshot, delete file, skip unsupported, conflict.
+6. Apply only after explicit confirmation.
+
+For v0.2.8, if cross-branch target-state computation becomes too large, keep the algorithm conservative: support full restore for the current branch's lineage and show a clear unsupported/conflict message for unrelated sibling states. The branch metadata should still be designed so broader cross-branch restore can be added later without changing saved data.
+
+### TUI integration
+
+Add branch-menu state to `run_tui` rather than invoking `src/menu.rs` inside the alternate-screen UI. Suggested approach:
+
+- Add an enum such as `OverlayState::BranchMenu(BranchMenuState)` in `src/app.rs` or a new `src/ui/branch_menu.rs`.
+- Extend `render::RenderState` to include an optional overlay.
+- Render a centered modal with title, help text, visible items, selected row, and preview/detail panel.
+- Route key events to the overlay first while it is open.
+- On confirmed branch/switch/restore, update:
+  - `conversation`,
+  - `chat_id`,
+  - `transcript = transcript_from_loaded(...)`,
+  - active assistant/tool state,
+  - scroll/stick-to-bottom/status.
+
+Keep the TUI loop readable by moving branch operations into functions such as:
+
+```rust
+open_branch_menu(...)
+handle_branch_menu_key(...)
+apply_branch_action(...)
+```
+
+### Slash command fallback
+
+Optionally add a discoverable slash command such as `/branch` or `/restore` that opens the same menu. This is useful for users whose terminals send unusual `Esc` sequences. If added, document it as an alias for the menu rather than a separate workflow.
+
+## Implementation Steps
+
+1. **Add branch metadata and helpers.** Extend `Record::Meta` compatibly, add branch point types, implement branch-family scanning and `create_branch` from a record prefix.
+2. **Build checkpoint extraction.** Convert conversations into user/assistant/tool checkpoints with labels, previews, timestamps, and valid prefix calculations.
+3. **Repair tool-call prefixes.** Generalize pending-tool-call repair so branches created around tool calls are valid for future provider requests.
+4. **Add edit journaling.** Capture successful `write`/`edit` before/after snapshots, append a file-edit journal entry, and keep this separate from model-visible JSONL records.
+5. **Implement restore planning.** Load journal entries, compute target states, detect conflicts by hash, and apply writes/deletes safely with existing atomic-write behavior.
+6. **Add the in-TUI menu.** Implement double-`Esc` idle detection, overlay state, rendering, keyboard navigation, action confirmation, and branch/switch application.
+7. **Wire status and recovery messages.** Make every branch, switch, restore, skip, and conflict result visible in the transcript or status line.
+8. **Document the feature.** Update README and bundled docs with shortcut behavior, branch semantics, file restore coverage, and limitations around shell/manual edits.
+9. **Test and polish.** Add unit/integration tests, run formatting, and verify the TUI manually in a small repository.
+
+## Tests
+
+- `conversation` tests:
+  - old JSONL conversations without branch metadata still load,
+  - new branch metadata serializes/deserializes,
+  - `create_branch` leaves the source file unchanged,
+  - branch-family scanning finds ancestors and descendants.
+- Checkpoint tests:
+  - user, assistant, tool-call, and tool-result checkpoints are extracted with stable labels,
+  - branching at a tool result keeps valid assistant/tool ordering,
+  - branching in the middle of multi-tool assistant output repairs missing tool results.
+- File journal tests:
+  - `write` records absent-to-present and present-to-present snapshots,
+  - `edit` records before/after bytes for successful edits only,
+  - failed or denied tools do not create journal entries.
+- Restore-plan tests:
+  - restore to an earlier checkpoint rewrites tracked files to prior content,
+  - restore to a later checkpoint can reapply tracked content from snapshots,
+  - created files are deleted only when hashes match,
+  - external modifications are reported as conflicts.
+- TUI/key tests where practical:
+  - first idle `Esc` sets double-press status,
+  - second idle `Esc` opens the branch menu,
+  - busy `Esc` still cancels a turn,
+  - approval `Esc` still denies approval.
+
+Manual checks:
+
+- Start a chat, make a `write` edit, branch conversation-only from before the edit, confirm the original remains available.
+- Open the menu from the branch and switch back to the original chat.
+- Branch with file restore and verify the workspace file content matches the chosen checkpoint.
+- Trigger a conflict by manually editing a tracked file before restore and confirm Cassady refuses to overwrite it by default.
+
+## Documentation
+
+Update:
+
+- `README.md`: everyday workflow section for branching/restoring and a short safety note.
+- `docs/commands.md` or the relevant TUI guide: double-`Esc`, optional `/branch`, and menu controls.
+- `docs/troubleshooting.md`: conflicts, unsupported shell/manual edits, and how to switch back to the original branch.
+- Any keyboard shortcut table maintained in bundled docs.
+
+## Acceptance Criteria
+
+- Pressing `Esc` twice while idle opens a branch/restore menu.
+- Selecting a user, assistant, or tool checkpoint creates a new branch conversation without modifying the source conversation.
+- The branch menu can be opened from the new branch to switch back to the original or create another branch.
+- Users can choose conversation-only branching or branch-plus-file restore.
+- File restore covers successful Cassady `write`/`edit` mutations with before/after snapshots and refuses unsafe overwrites by default.
+- Branches created around tool calls produce valid future model requests.
+- Existing conversations remain loadable.
+- `cargo fmt` and `cargo test --locked --all-targets` pass.

src/agent.rs

@@ -304,10 +304,19 @@ pub async fn run_turn_with_commands(
             let (runtime_tx, mut runtime_rx) = mpsc::unbounded_channel::<ToolRuntimeEvent>();
             let mut call_tool_ctx = tool_ctx.clone();
             call_tool_ctx.runtime_tx = Some(runtime_tx);
+            let file_edit_snapshot = crate::file_edits::begin_tool_edit(
+                &settings.config.root,
+                &conversation.id,
+                conversation.records.len(),
+                &call_id,
+                &call_name,
+                &call_arguments,
+                &call_tool_ctx,
+            );
             let output = {
                 let execute = tools::execute_with_approval(
                     &call_name,
-                    call_arguments,
+                    call_arguments.clone(),
                     &call_tool_ctx,
                     approved,
                 );
@@ -325,6 +334,11 @@ pub async fn run_turn_with_commands(
                 }
                 output
             };
+            if output.ok {
+                if let Some(snapshot) = file_edit_snapshot {
+                    let _ = crate::file_edits::finish_tool_edit(&settings.config.root, snapshot);
+                }
+            }
             let _ = tx.send(AgentEvent::ToolResult {
                 id: call_id.clone(),
                 name: call_name.clone(),

src/app.rs

@@ -21,6 +21,10 @@ const TOOL_CANCELLED_MESSAGE: &str = "Tool execution cancelled by user.";
 
 pub async fn run() -> Result<()> {
     let mut cli = cli::parse();
+    if let Some(Command::Update(args)) = cli.command.clone() {
+        return crate::update::run(args).await;
+    }
+
     if matches!(cli.command, Some(Command::Check)) {
         let report = crate::check::run(&cli)?;
         print!("{}", report.render());
@@ -204,6 +208,8 @@ async fn run_tui(
     let mut reasoning_effort = config.reasoning_effort;
     let mut scroll: u16 = 0;
     let mut last_ctrl_c: Option<Instant> = None;
+    let mut last_esc: Option<Instant> = None;
+    let mut branch_menu: Option<BranchMenuState> = None;
     let mut handle: Option<JoinHandle<Result<Conversation>>> = None;
     let mut cancel_requested = false;
     let mut current_turn_start_len: Option<usize> = None;
@@ -328,6 +334,7 @@ async fn run_tui(
             )?
         };
 
+        let overlay_view = branch_menu.as_ref().map(BranchMenuState::overlay_view);
         terminal.draw(|f| {
             render::render(
                 f,
@@ -345,7 +352,12 @@ async fn run_tui(
                     show_reasoning,
                     reasoning_effort,
                     scroll,
-                    autofill: autofill.as_ref(),
+                    autofill: if branch_menu.is_some() {
+                        None
+                    } else {
+                        autofill.as_ref()
+                    },
+                    overlay: overlay_view.as_ref(),
                 },
             )
         })?;
@@ -354,6 +366,43 @@ async fn run_tui(
             match event {
                 Event::Key(key) if key.kind == KeyEventKind::Press => {
                     let busy = handle.is_some();
+                    if branch_menu.is_some() {
+                        match handle_branch_menu_key(
+                            key.code,
+                            &mut branch_menu,
+                            &config,
+                            &cwd,
+                            &mut conversation,
+                            &mut chat_id,
+                            &mut transcript,
+                            &mut active_assistant,
+                            &mut active_reasoning,
+                            &mut active_tools,
+                            &mut status,
+                        ) {
+                            Ok(BranchMenuOutcome::None) => {}
+                            Ok(BranchMenuOutcome::Changed) => {
+                                stick_to_bottom = true;
+                                scroll = bottom_scroll(
+                                    &terminal,
+                                    &input,
+                                    &transcript,
+                                    show_full_tools,
+                                    show_reasoning,
+                                )?;
+                            }
+                            Err(err) => {
+                                branch_menu = None;
+                                status = format!("branch menu failed: {err}");
+                                transcript.push(TranscriptBlock {
+                                    kind: TranscriptKind::Error,
+                                    title: "branch".into(),
+                                    content: err.to_string(),
+                                });
+                            }
+                        }
+                        continue;
+                    }
                     if busy {
                         if let Some(pending) = pending_approval.clone() {
                             match key.code {
@@ -425,11 +474,13 @@ async fn run_tui(
                                 }
                                 cancel_requested = true;
                                 last_ctrl_c = Some(now);
+                                last_esc = None;
                                 status = "turn cancellation requested; press Ctrl-C again within 1.5s to exit".into();
                             } else {
                                 input.clear();
                                 autofill_selected = 0;
                                 last_ctrl_c = Some(now);
+                                last_esc = None;
                                 status = "press Ctrl-C again within 1.5s to exit".into();
                             }
                         }
@@ -439,8 +490,31 @@ async fn run_tui(
                             }
                             cancel_requested = true;
                             last_ctrl_c = None;
+                            last_esc = None;
                             status = "turn cancellation requested".into();
                         }
+                        (KeyCode::Esc, _) => {
+                            let now = Instant::now();
+                            if last_esc
+                                .map(|t| now.duration_since(t) <= Duration::from_millis(1500))
+                                .unwrap_or(false)
+                            {
+                                match BranchMenuState::open(&config, &conversation) {
+                                    Ok(menu) => {
+                                        branch_menu = Some(menu);
+                                        last_esc = None;
+                                        status = "branch/restore menu".into();
+                                    }
+                                    Err(err) => {
+                                        last_esc = None;
+                                        status = format!("branch menu failed: {err}");
+                                    }
+                                }
+                            } else {
+                                last_esc = Some(now);
+                                status = "press Esc again within 1.5s to branch or restore".into();
+                            }
+                        }
                         (KeyCode::BackTab, _) => {
                             if busy {
                                 status = "mode can be changed when idle".into();
@@ -576,6 +650,28 @@ async fn run_tui(
                                 input.clear();
                             } else if input.trim_start().starts_with('/') {
                                 match parse_local_command(&input) {
+                                    Ok(LocalCommand::Branch) => {
+                                        if busy {
+                                            status = "branch menu can be opened when idle".into();
+                                        } else {
+                                            match BranchMenuState::open(&config, &conversation) {
+                                                Ok(menu) => {
+                                                    branch_menu = Some(menu);
+                                                    input.clear();
+                                                    autofill_selected = 0;
+                                                    status = "branch/restore menu".into();
+                                                }
+                                                Err(err) => {
+                                                    status = format!("branch menu failed: {err}");
+                                                    transcript.push(TranscriptBlock {
+                                                        kind: TranscriptKind::Error,
+                                                        title: "branch".into(),
+                                                        content: err.to_string(),
+                                                    });
+                                                }
+                                            }
+                                        }
+                                    }
                                     Ok(LocalCommand::Status) => {
                                         let content = chat_status(
                                             &chat_id,
@@ -859,6 +955,12 @@ async fn run_tui(
         {
             last_ctrl_c = None;
         }
+        if last_esc
+            .map(|t| t.elapsed() > Duration::from_millis(1500))
+            .unwrap_or(false)
+        {
+            last_esc = None;
+        }
     }
 }
 
@@ -868,6 +970,337 @@ struct PendingApproval {
     block_index: usize,
 }
 
+#[derive(Debug, Clone)]
+enum BranchMenuMode {
+    Main,
+    Actions(crate::branch::Checkpoint),
+}
+
+#[derive(Debug, Clone)]
+struct BranchMenuState {
+    mode: BranchMenuMode,
+    selected: usize,
+    family: crate::branch::BranchFamily,
+}
+
+#[derive(Debug, Clone)]
+enum BranchMenuItem {
+    Switch(String),
+    Checkpoint(crate::branch::Checkpoint),
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum BranchMenuOutcome {
+    None,
+    Changed,
+}
+
+impl BranchMenuState {
+    fn open(config: &Config, conversation: &Conversation) -> Result<Self> {
+        let family = crate::branch::load_family(&config.conversations_dir(), conversation)?;
+        Ok(Self {
+            mode: BranchMenuMode::Main,
+            selected: 0,
+            family,
+        })
+    }
+
+    fn overlay_view(&self) -> render::OverlayView {
+        match &self.mode {
+            BranchMenuMode::Main => render::OverlayView {
+                title: "Branch / Restore".into(),
+                help: "Enter select · Esc cancel · ↑/↓ move".into(),
+                selected: self.selected,
+                items: self
+                    .main_items()
+                    .into_iter()
+                    .map(|item| match item {
+                        BranchMenuItem::Switch(id) => {
+                            let branch = self.family.branches.iter().find(|b| b.id == id);
+                            let mut label = if branch.is_some_and(|b| b.current) {
+                                format!("current branch {id}")
+                            } else {
+                                format!("switch to {id}")
+                            };
+                            if branch.and_then(|b| b.parent_chat_id.as_ref()).is_none() {
+                                label.push_str(" (root)");
+                            }
+                            render::OverlayItem {
+                                label,
+                                detail: branch.and_then(|b| b.branch_label.clone()).unwrap_or_else(
+                                    || {
+                                        branch
+                                            .map(|b| format!("{} records", b.record_count))
+                                            .unwrap_or_default()
+                                    },
+                                ),
+                            }
+                        }
+                        BranchMenuItem::Checkpoint(checkpoint) => render::OverlayItem {
+                            label: format!("{} · {}", checkpoint.chat_id, checkpoint.label),
+                            detail: checkpoint.detail,
+                        },
+                    })
+                    .collect(),
+            },
+            BranchMenuMode::Actions(checkpoint) => render::OverlayView {
+                title: "Branch from checkpoint".into(),
+                help: format!(
+                    "{} · Enter select · Esc back",
+                    crate::branch::checkpoint_title(checkpoint)
+                ),
+                selected: self.selected,
+                items: vec![
+                    render::OverlayItem {
+                        label: "Branch conversation only".into(),
+                        detail: "safe default; leaves files unchanged".into(),
+                    },
+                    render::OverlayItem {
+                        label: "Branch conversation and restore tracked files".into(),
+                        detail: "applies safe Cassady write/edit snapshots; conflicts are skipped"
+                            .into(),
+                    },
+                    render::OverlayItem {
+                        label: "Preview tracked file restore plan".into(),
+                        detail: "show file actions in transcript".into(),
+                    },
+                    render::OverlayItem {
+                        label: "Cancel".into(),
+                        detail: String::new(),
+                    },
+                ],
+            },
+        }
+    }
+
+    fn main_items(&self) -> Vec<BranchMenuItem> {
+        let mut items = Vec::new();
+        for branch in &self.family.branches {
+            items.push(BranchMenuItem::Switch(branch.id.clone()));
+        }
+        for checkpoint in &self.family.checkpoints {
+            items.push(BranchMenuItem::Checkpoint(checkpoint.clone()));
+        }
+        items
+    }
+
+    fn len(&self) -> usize {
+        match self.mode {
+            BranchMenuMode::Main => self.main_items().len(),
+            BranchMenuMode::Actions(_) => 4,
+        }
+    }
+}
+
+#[allow(clippy::too_many_arguments)]
+fn handle_branch_menu_key(
+    code: KeyCode,
+    menu: &mut Option<BranchMenuState>,
+    config: &Config,
+    _cwd: &Path,
+    conversation: &mut Conversation,
+    chat_id: &mut String,
+    transcript: &mut Vec<TranscriptBlock>,
+    active_assistant: &mut Option<usize>,
+    active_reasoning: &mut Option<usize>,
+    active_tools: &mut HashMap<String, usize>,
+    status: &mut String,
+) -> Result<BranchMenuOutcome> {
+    let Some(state) = menu.as_mut() else {
+        return Ok(BranchMenuOutcome::None);
+    };
+    match code {
+        KeyCode::Esc => match state.mode {
+            BranchMenuMode::Main => {
+                *menu = None;
+                *status = "branch menu cancelled".into();
+            }
+            BranchMenuMode::Actions(_) => {
+                state.mode = BranchMenuMode::Main;
+                state.selected = 0;
+            }
+        },
+        KeyCode::Up | KeyCode::Char('k') => {
+            state.selected = state.selected.saturating_sub(1);
+        }
+        KeyCode::Down | KeyCode::Char('j') => {
+            let max = state.len().saturating_sub(1);
+            state.selected = state.selected.saturating_add(1).min(max);
+        }
+        KeyCode::Enter => {
+            return apply_branch_menu_selection(
+                menu,
+                config,
+                conversation,
+                chat_id,
+                transcript,
+                active_assistant,
+                active_reasoning,
+                active_tools,
+                status,
+            );
+        }
+        _ => {}
+    }
+    Ok(BranchMenuOutcome::None)
+}
+
+#[allow(clippy::too_many_arguments)]
+fn apply_branch_menu_selection(
+    menu: &mut Option<BranchMenuState>,
+    config: &Config,
+    conversation: &mut Conversation,
+    chat_id: &mut String,
+    transcript: &mut Vec<TranscriptBlock>,
+    active_assistant: &mut Option<usize>,
+    active_reasoning: &mut Option<usize>,
+    active_tools: &mut HashMap<String, usize>,
+    status: &mut String,
+) -> Result<BranchMenuOutcome> {
+    let Some(state) = menu.as_mut() else {
+        return Ok(BranchMenuOutcome::None);
+    };
+    match &state.mode {
+        BranchMenuMode::Main => {
+            let items = state.main_items();
+            let Some(item) = items.get(state.selected).cloned() else {
+                return Ok(BranchMenuOutcome::None);
+            };
+            match item {
+                BranchMenuItem::Switch(id) => {
+                    let (loaded, warning) = Conversation::load(&config.conversations_dir(), &id)?;
+                    *conversation = loaded;
+                    *chat_id = conversation.id.clone();
+                    *transcript = transcript_from_loaded(conversation, warning);
+                    *active_assistant = None;
+                    *active_reasoning = None;
+                    active_tools.clear();
+                    *status = format!("switched to branch {chat_id}");
+                    *menu = None;
+                    Ok(BranchMenuOutcome::Changed)
+                }
+                BranchMenuItem::Checkpoint(checkpoint) => {
+                    state.mode = BranchMenuMode::Actions(checkpoint);
+                    state.selected = 0;
+                    Ok(BranchMenuOutcome::None)
+                }
+            }
+        }
+        BranchMenuMode::Actions(checkpoint) => {
+            let selected = state.selected;
+            let checkpoint = checkpoint.clone();
+            match selected {
+                0 => branch_from_checkpoint(
+                    menu,
+                    config,
+                    &checkpoint,
+                    false,
+                    conversation,
+                    chat_id,
+                    transcript,
+                    active_assistant,
+                    active_reasoning,
+                    active_tools,
+                    status,
+                ),
+                1 => branch_from_checkpoint(
+                    menu,
+                    config,
+                    &checkpoint,
+                    true,
+                    conversation,
+                    chat_id,
+                    transcript,
+                    active_assistant,
+                    active_reasoning,
+                    active_tools,
+                    status,
+                ),
+                2 => {
+                    let plan = crate::file_edits::plan_restore(
+                        &config.root,
+                        &checkpoint.chat_id,
+                        checkpoint.record_index,
+                    )?;
+                    transcript.push(TranscriptBlock {
+                        kind: TranscriptKind::Status,
+                        title: "restore preview".into(),
+                        content: crate::file_edits::summarize_plan(&plan),
+                    });
+                    *status = "restore plan previewed".into();
+                    *menu = None;
+                    Ok(BranchMenuOutcome::Changed)
+                }
+                _ => {
+                    state.mode = BranchMenuMode::Main;
+                    state.selected = 0;
+                    Ok(BranchMenuOutcome::None)
+                }
+            }
+        }
+    }
+}
+
+#[allow(clippy::too_many_arguments)]
+fn branch_from_checkpoint(
+    menu: &mut Option<BranchMenuState>,
+    config: &Config,
+    checkpoint: &crate::branch::Checkpoint,
+    restore_files: bool,
+    conversation: &mut Conversation,
+    chat_id: &mut String,
+    transcript: &mut Vec<TranscriptBlock>,
+    active_assistant: &mut Option<usize>,
+    active_reasoning: &mut Option<usize>,
+    active_tools: &mut HashMap<String, usize>,
+    status: &mut String,
+) -> Result<BranchMenuOutcome> {
+    let (source, _) = Conversation::load(&config.conversations_dir(), &checkpoint.chat_id)?;
+    let branch = crate::branch::create_branch(&config.conversations_dir(), &source, checkpoint)?;
+    let old_id = checkpoint.chat_id.clone();
+    *conversation = branch;
+    *chat_id = conversation.id.clone();
+    *transcript = transcript_from_loaded(conversation, None);
+    *active_assistant = None;
+    *active_reasoning = None;
+    active_tools.clear();
+
+    let mut restore_status = String::new();
+    if restore_files {
+        let plan = crate::file_edits::plan_restore(
+            &config.root,
+            &checkpoint.chat_id,
+            checkpoint.record_index,
+        )?;
+        let summary = crate::file_edits::summarize_plan(&plan);
+        let outcome = crate::file_edits::apply_restore_plan(&plan)?;
+        restore_status = format!(
+            "; restored files: {} applied, {} skipped, {} conflicts",
+            outcome.applied, outcome.skipped, outcome.conflicts
+        );
+        transcript.push(TranscriptBlock {
+            kind: if outcome.conflicts == 0 {
+                TranscriptKind::Status
+            } else {
+                TranscriptKind::Error
+            },
+            title: "file restore".into(),
+            content: format!(
+                "{summary}\n\nApplied: {}\nSkipped: {}\nConflicts: {}",
+                outcome.applied, outcome.skipped, outcome.conflicts
+            ),
+        });
+    }
+
+    *status = format!(
+        "branched {chat_id} from {old_id} at {}{}",
+        crate::branch::checkpoint_title(checkpoint),
+        restore_status
+    );
+    *menu = None;
+    Ok(BranchMenuOutcome::Changed)
+}
+
 struct AgentEventContext<'a> {
     terminal: &'a terminal::CassTerminal,
     input: &'a str,
@@ -1243,6 +1676,7 @@ fn assistant_content_matches(a: &str, b: &str) -> bool {
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 enum LocalCommand {
+    Branch,
     Model(String),
     New,
     Resume(String),
@@ -1257,6 +1691,12 @@ struct CommandSpec {
 }
 
 const COMMANDS: &[CommandSpec] = &[
+    CommandSpec {
+        name: "branch",
+        usage: "/branch",
+        description: "open branch/restore menu",
+        takes_value: false,
+    },
     CommandSpec {
         name: "model",
         usage: "/model <model>",
@@ -1507,6 +1947,12 @@ fn parse_local_command(input: &str) -> std::result::Result<LocalCommand, String>
     };
 
     match command {
+        "/branch" | "/restore" => {
+            if parts.next().is_some() {
+                return Err("usage: /branch".into());
+            }
+            Ok(LocalCommand::Branch)
+        }
         "/model" => {
             let Some(model) = parts.next() else {
                 return Err("usage: /model <model>".into());

src/branch.rs

@@ -0,0 +1,435 @@
+use crate::conversation::{self, BranchPoint, Conversation, Record, StoredToolCall};
+use anyhow::{bail, Context, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::{BTreeMap, BTreeSet, HashSet};
+use std::fs::{self, File, OpenOptions};
+use std::io::{BufRead, BufReader, Write};
+use std::path::Path;
+
+const TOOL_CANCELLED_MESSAGE: &str = "Tool execution cancelled by user.";
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum CheckpointKind {
+    User,
+    Assistant,
+    ToolCall,
+    ToolResult,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Checkpoint {
+    pub id: String,
+    pub chat_id: String,
+    pub record_index: usize,
+    pub tool_call_id: Option<String>,
+    pub kind: CheckpointKind,
+    pub label: String,
+    pub detail: String,
+    pub ts: Option<String>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct BranchSummary {
+    pub id: String,
+    pub created_at: String,
+    pub parent_chat_id: Option<String>,
+    pub branch_label: Option<String>,
+    pub record_count: usize,
+    pub current: bool,
+}
+
+#[derive(Debug, Clone)]
+pub struct BranchFamily {
+    pub branches: Vec<BranchSummary>,
+    pub checkpoints: Vec<Checkpoint>,
+}
+
+pub fn checkpoint_records(records: &[Record], chat_id: &str) -> Vec<Checkpoint> {
+    let mut checkpoints = Vec::new();
+    for (idx, record) in records.iter().enumerate() {
+        match record {
+            Record::User { content, ts } => checkpoints.push(Checkpoint {
+                id: format!("{chat_id}:{idx}:user"),
+                chat_id: chat_id.to_string(),
+                record_index: idx,
+                tool_call_id: None,
+                kind: CheckpointKind::User,
+                label: "user".into(),
+                detail: preview(content),
+                ts: Some(ts.clone()),
+            }),
+            Record::Assistant {
+                content,
+                reasoning,
+                tool_calls,
+                ts,
+                ..
+            } => {
+                let detail = if content.trim().is_empty() {
+                    preview(reasoning)
+                } else {
+                    preview(content)
+                };
+                checkpoints.push(Checkpoint {
+                    id: format!("{chat_id}:{idx}:assistant"),
+                    chat_id: chat_id.to_string(),
+                    record_index: idx,
+                    tool_call_id: None,
+                    kind: CheckpointKind::Assistant,
+                    label: "assistant".into(),
+                    detail,
+                    ts: Some(ts.clone()),
+                });
+                for call in tool_calls {
+                    checkpoints.push(Checkpoint {
+                        id: format!("{chat_id}:{idx}:tool_call:{}", call.id),
+                        chat_id: chat_id.to_string(),
+                        record_index: idx,
+                        tool_call_id: Some(call.id.clone()),
+                        kind: CheckpointKind::ToolCall,
+                        label: format!("tool call {}", call.name),
+                        detail: tool_call_detail(call),
+                        ts: Some(ts.clone()),
+                    });
+                }
+            }
+            Record::Tool {
+                tool_call_id,
+                name,
+                ok,
+                content,
+                ts,
+            } => checkpoints.push(Checkpoint {
+                id: format!("{chat_id}:{idx}:tool_result:{tool_call_id}"),
+                chat_id: chat_id.to_string(),
+                record_index: idx,
+                tool_call_id: Some(tool_call_id.clone()),
+                kind: CheckpointKind::ToolResult,
+                label: format!("tool {name} {}", if *ok { "✓" } else { "✗" }),
+                detail: preview(content),
+                ts: Some(ts.clone()),
+            }),
+            _ => {}
+        }
+    }
+    checkpoints
+}
+
+pub fn load_family(conversations_dir: &Path, current: &Conversation) -> Result<BranchFamily> {
+    let metas = load_all_metas(conversations_dir)?;
+    let root = root_for(&current.id, &metas);
+    let mut ids = BTreeSet::new();
+    for id in metas.keys() {
+        if root_for(id, &metas) == root {
+            ids.insert(id.clone());
+        }
+    }
+    ids.insert(current.id.clone());
+
+    let mut branches = Vec::new();
+    let mut checkpoints = Vec::new();
+    for id in ids {
+        let Ok((conversation, _)) = Conversation::load(conversations_dir, &id) else {
+            continue;
+        };
+        let meta = conversation.meta();
+        branches.push(BranchSummary {
+            id: conversation.id.clone(),
+            created_at: meta
+                .as_ref()
+                .map(|m| m.created_at.clone())
+                .unwrap_or_default(),
+            parent_chat_id: meta.as_ref().and_then(|m| m.parent_chat_id.clone()),
+            branch_label: meta
+                .as_ref()
+                .and_then(|m| m.branch_from.as_ref().map(|p| p.checkpoint_label.clone())),
+            record_count: conversation.records.len(),
+            current: conversation.id == current.id,
+        });
+        checkpoints.extend(checkpoint_records(&conversation.records, &conversation.id));
+    }
+    branches.sort_by(|a, b| b.created_at.cmp(&a.created_at));
+    checkpoints.sort_by(|a, b| {
+        a.chat_id
+            .cmp(&b.chat_id)
+            .then(a.record_index.cmp(&b.record_index))
+            .then(a.id.cmp(&b.id))
+    });
+    Ok(BranchFamily {
+        branches,
+        checkpoints,
+    })
+}
+
+pub fn create_branch(
+    conversations_dir: &Path,
+    source: &Conversation,
+    checkpoint: &Checkpoint,
+) -> Result<Conversation> {
+    if source.id != checkpoint.chat_id {
+        bail!(
+            "checkpoint {} belongs to {}, not {}",
+            checkpoint.id,
+            checkpoint.chat_id,
+            source.id
+        );
+    }
+    if checkpoint.record_index >= source.records.len() {
+        bail!("checkpoint record index is out of range");
+    }
+
+    fs::create_dir_all(conversations_dir)?;
+    let id = conversation::new_chat_id();
+    let path = conversations_dir.join(format!("{id}.jsonl"));
+    let mut records = Vec::new();
+    let meta = source
+        .meta()
+        .context("source conversation is missing metadata")?;
+    records.push(Record::Meta {
+        chat_id: id.clone(),
+        created_at: conversation::now_ts(),
+        model: meta.model,
+        cwd: meta.cwd,
+        parent_chat_id: Some(source.id.clone()),
+        branch_from: Some(BranchPoint {
+            chat_id: source.id.clone(),
+            record_index: checkpoint.record_index,
+            tool_call_id: checkpoint.tool_call_id.clone(),
+            checkpoint_label: checkpoint_title(checkpoint),
+        }),
+    });
+
+    let prefix = valid_prefix(source, checkpoint)?;
+    records.extend(prefix);
+    repair_pending_tool_calls(&mut records);
+
+    let mut file = OpenOptions::new()
+        .create_new(true)
+        .write(true)
+        .open(&path)
+        .with_context(|| format!("creating branch conversation {}", path.display()))?;
+    for record in &records {
+        writeln!(file, "{}", serde_json::to_string(record)?)?;
+    }
+    file.flush()?;
+
+    Ok(Conversation { id, path, records })
+}
+
+fn valid_prefix(source: &Conversation, checkpoint: &Checkpoint) -> Result<Vec<Record>> {
+    let mut end = checkpoint.record_index + 1;
+    if matches!(checkpoint.kind, CheckpointKind::ToolCall) {
+        end = checkpoint.record_index + 1;
+    }
+    let mut prefix = source.records[..end].to_vec();
+
+    // Drop the source meta; the branch writes its own meta record.
+    if matches!(prefix.first(), Some(Record::Meta { .. })) {
+        prefix.remove(0);
+    }
+
+    // For a tool-call checkpoint, keep the assistant turn but do not copy any
+    // later tool result. The repair step below writes cancelled tool results so
+    // the next provider request remains valid.
+    Ok(prefix)
+}
+
+pub fn repair_pending_tool_calls(records: &mut Vec<Record>) {
+    let mut pending: Vec<(String, String)> = Vec::new();
+    for record in records.iter() {
+        match record {
+            Record::Assistant { tool_calls, .. } => {
+                pending = tool_calls
+                    .iter()
+                    .map(|call| (call.id.clone(), call.name.clone()))
+                    .collect();
+            }
+            Record::Tool { tool_call_id, .. } => pending.retain(|(id, _)| id != tool_call_id),
+            Record::User { .. } => pending.clear(),
+            _ => {}
+        }
+    }
+    let seen: HashSet<String> = records
+        .iter()
+        .filter_map(|record| match record {
+            Record::Tool { tool_call_id, .. } => Some(tool_call_id.clone()),
+            _ => None,
+        })
+        .collect();
+    for (id, name) in pending {
+        if seen.contains(&id) {
+            continue;
+        }
+        records.push(Record::Tool {
+            tool_call_id: id,
+            name,
+            ok: false,
+            content: TOOL_CANCELLED_MESSAGE.to_string(),
+            ts: conversation::now_ts(),
+        });
+    }
+}
+
+fn load_all_metas(conversations_dir: &Path) -> Result<BTreeMap<String, (Option<String>, String)>> {
+    let mut out = BTreeMap::new();
+    if !conversations_dir.exists() {
+        return Ok(out);
+    }
+    for entry in fs::read_dir(conversations_dir)? {
+        let entry = entry?;
+        let path = entry.path();
+        if path.extension().and_then(|s| s.to_str()) != Some("jsonl") {
+            continue;
+        }
+        let Some(id) = path.file_stem().and_then(|s| s.to_str()) else {
+            continue;
+        };
+        if let Ok(Some((parent, cwd))) = read_meta_parent_cwd(&path) {
+            out.insert(id.to_string(), (parent, cwd));
+        }
+    }
+    Ok(out)
+}
+
+fn read_meta_parent_cwd(path: &Path) -> Result<Option<(Option<String>, String)>> {
+    let file = File::open(path)?;
+    for line in BufReader::new(file).lines().take(10) {
+        let line = line?;
+        if line.trim().is_empty() {
+            continue;
+        }
+        let record: Record = serde_json::from_str(&line)?;
+        if let Record::Meta {
+            parent_chat_id,
+            cwd,
+            ..
+        } = record
+        {
+            return Ok(Some((parent_chat_id, cwd)));
+        }
+    }
+    Ok(None)
+}
+
+fn root_for(id: &str, metas: &BTreeMap<String, (Option<String>, String)>) -> String {
+    let mut current = id.to_string();
+    let mut seen = HashSet::new();
+    while seen.insert(current.clone()) {
+        let Some((Some(parent), _)) = metas.get(&current) else {
+            break;
+        };
+        current = parent.clone();
+    }
+    current
+}
+
+pub fn checkpoint_title(checkpoint: &Checkpoint) -> String {
+    if checkpoint.detail.is_empty() {
+        checkpoint.label.clone()
+    } else {
+        format!("{}: {}", checkpoint.label, checkpoint.detail)
+    }
+}
+
+fn tool_call_detail(call: &StoredToolCall) -> String {
+    let mut detail = String::new();
+    if let Some(path) = call.arguments.get("path").and_then(|v| v.as_str()) {
+        detail = format!("file: {path}");
+    } else if let Some(command) = call.arguments.get("command").and_then(|v| v.as_str()) {
+        detail = command.to_string();
+    }
+    if detail.is_empty() {
+        preview(&call.arguments.to_string())
+    } else {
+        preview(&detail)
+    }
+}
+
+fn preview(content: &str) -> String {
+    content
+        .lines()
+        .find(|line| !line.trim().is_empty())
+        .unwrap_or("")
+        .chars()
+        .take(96)
+        .collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde_json::json;
+    use tempfile::tempdir;
+
+    fn base_records(id: &str) -> Vec<Record> {
+        vec![
+            Record::Meta {
+                chat_id: id.into(),
+                created_at: "now".into(),
+                model: "m".into(),
+                cwd: "/tmp".into(),
+                parent_chat_id: None,
+                branch_from: None,
+            },
+            Record::System {
+                content: "s".into(),
+            },
+            Record::User {
+                content: "u".into(),
+                ts: "t".into(),
+            },
+            Record::Assistant {
+                content: "a".into(),
+                reasoning: String::new(),
+                reasoning_field: None,
+                tool_calls: vec![StoredToolCall {
+                    id: "call1".into(),
+                    name: "read".into(),
+                    arguments: json!({"path":"x"}),
+                }],
+                ts: "t".into(),
+            },
+        ]
+    }
+
+    #[test]
+    fn checkpoints_include_tool_calls() {
+        let checkpoints = checkpoint_records(&base_records("c"), "c");
+        assert!(checkpoints.iter().any(|c| c.kind == CheckpointKind::User));
+        assert!(checkpoints
+            .iter()
+            .any(|c| c.kind == CheckpointKind::Assistant));
+        assert!(checkpoints
+            .iter()
+            .any(|c| c.kind == CheckpointKind::ToolCall));
+    }
+
+    #[test]
+    fn create_branch_does_not_modify_source_and_repairs_pending_tools() {
+        let dir = tempdir().unwrap();
+        let source = Conversation {
+            id: "source".into(),
+            path: dir.path().join("source.jsonl"),
+            records: base_records("source"),
+        };
+        let checkpoint = checkpoint_records(&source.records, &source.id)
+            .into_iter()
+            .find(|c| c.kind == CheckpointKind::Assistant)
+            .unwrap();
+        let branch = create_branch(dir.path(), &source, &checkpoint).unwrap();
+        assert_ne!(branch.id, source.id);
+        assert!(
+            source
+                .records
+                .iter()
+                .filter(|r| matches!(r, Record::Tool { .. }))
+                .count()
+                == 0
+        );
+        assert!(branch
+            .records
+            .iter()
+            .any(|r| matches!(r, Record::Tool { ok: false, .. })));
+    }
+}

src/cli.rs

@@ -1,4 +1,4 @@
-use clap::{Parser, Subcommand};
+use clap::{Args, Parser, Subcommand};
 use std::path::PathBuf;
 
 #[derive(Debug, Parser, Clone)]
@@ -46,6 +46,35 @@ pub enum Command {
     Check,
     /// Configure an OpenAI-compatible provider and first model.
     Setup,
+    /// Update Cassady from official GitHub releases.
+    Update(UpdateArgs),
+}
+
+#[derive(Debug, Args, Clone, PartialEq, Eq)]
+pub struct UpdateArgs {
+    /// Check the latest release without installing.
+    #[arg(long)]
+    pub check: bool,
+
+    /// Show what would be updated without downloading or installing.
+    #[arg(long)]
+    pub dry_run: bool,
+
+    /// Accept default prompts for non-interactive use.
+    #[arg(long, short = 'y')]
+    pub yes: bool,
+
+    /// Require a matching prebuilt archive and do not fall back to source.
+    #[arg(long, conflicts_with = "source")]
+    pub prebuilt: bool,
+
+    /// Build from release source even when a prebuilt archive exists.
+    #[arg(long, conflicts_with = "prebuilt")]
+    pub source: bool,
+
+    /// Install a specific release tag, such as v0.2.7.
+    #[arg(long, value_name = "TAG")]
+    pub to: Option<String>,
 }
 
 pub fn parse() -> Cli {

src/config.rs

@@ -151,6 +151,34 @@ pub struct Config {
     pub docs_dir: PathBuf,
 }
 
+#[derive(Debug, Clone, Default)]
+pub struct ConfigOverrides {
+    pub model: Option<String>,
+    pub base_url: Option<String>,
+    pub api_key_env: Option<String>,
+    pub access_mode: Option<AccessMode>,
+}
+
+impl ConfigOverrides {
+    pub fn from_cli(cli: &Cli) -> Self {
+        let access_mode = if cli.readonly {
+            Some(AccessMode::ReadOnly)
+        } else if cli.workspace_edit {
+            Some(AccessMode::WorkspaceEdit)
+        } else if cli.full_access {
+            Some(AccessMode::FullAccess)
+        } else {
+            None
+        };
+        Self {
+            model: cli.model.clone(),
+            base_url: cli.base_url.clone(),
+            api_key_env: cli.api_key_env.clone(),
+            access_mode,
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum ApiKeyReference {
     Env(String),
@@ -287,17 +315,29 @@ pub fn models_path(root: &Path) -> PathBuf {
 
 impl Config {
     pub fn load(cli: &Cli) -> Result<Self> {
-        Self::load_from_root(cass_root(), cli)
+        Self::load_with_overrides(cass_root(), ConfigOverrides::from_cli(cli))
     }
 
-    pub fn load_from_root(root: PathBuf, cli: &Cli) -> Result<Self> {
+    pub fn load_with_overrides(root: PathBuf, overrides: ConfigOverrides) -> Result<Self> {
         fs::create_dir_all(root.join("conversations"))
             .with_context(|| format!("creating {}", root.join("conversations").display()))?;
         let docs_dir = crate::docs::install(&root)?;
-        Self::load_from_root_with_docs(root, docs_dir, cli)
+        Self::load_from_root_with_docs_and_overrides(root, docs_dir, overrides)
+    }
+
+    pub fn load_from_root(root: PathBuf, cli: &Cli) -> Result<Self> {
+        Self::load_with_overrides(root, ConfigOverrides::from_cli(cli))
     }
 
     pub fn load_from_root_with_docs(root: PathBuf, docs_dir: PathBuf, cli: &Cli) -> Result<Self> {
+        Self::load_from_root_with_docs_and_overrides(root, docs_dir, ConfigOverrides::from_cli(cli))
+    }
+
+    pub fn load_from_root_with_docs_and_overrides(
+        root: PathBuf,
+        docs_dir: PathBuf,
+        overrides: ConfigOverrides,
+    ) -> Result<Self> {
         fs::create_dir_all(&root).with_context(|| format!("creating {}", root.display()))?;
         let providers = load_or_create_default_provider_registry(&root)?;
         let models = load_or_create_default_model_registry(&root)?;
@@ -330,19 +370,13 @@ impl Config {
             }
         }
 
-        if cli.readonly {
-            cfg.default_access_mode = AccessMode::ReadOnly;
-        }
-        if cli.workspace_edit {
-            cfg.default_access_mode = AccessMode::WorkspaceEdit;
-        }
-        if cli.full_access {
-            cfg.default_access_mode = AccessMode::FullAccess;
+        if let Some(access_mode) = overrides.access_mode {
+            cfg.default_access_mode = access_mode;
         }
 
-        let requested_model = requested_model(file.as_ref(), cli);
+        let requested_model = requested_model(file.as_ref(), &overrides);
         let provider_id_from_config = requested_provider_id(file.as_ref(), &providers);
-        let legacy = legacy_provider_override(file.as_ref(), cli);
+        let legacy = legacy_provider_override(file.as_ref(), &overrides);
 
         let mut provider = resolve_provider(
             requested_model.as_deref().unwrap_or(DEFAULT_MODEL),
@@ -353,10 +387,10 @@ impl Config {
             &models,
         )?;
 
-        if let Some(base_url) = &cli.base_url {
+        if let Some(base_url) = &overrides.base_url {
             provider.base_url = base_url.clone();
         }
-        if let Some(api_key_env) = &cli.api_key_env {
+        if let Some(api_key_env) = &overrides.api_key_env {
             provider.api_key = format!("${api_key_env}");
         }
 
@@ -706,8 +740,8 @@ pub fn find_model_for_provider<'a>(
         .find(|m| m.provider == provider_id && m.id == model_id)
 }
 
-fn requested_model(file: Option<&ConfigFile>, cli: &Cli) -> Option<String> {
-    cli.model.clone().or_else(|| {
+fn requested_model(file: Option<&ConfigFile>, overrides: &ConfigOverrides) -> Option<String> {
+    overrides.model.clone().or_else(|| {
         file.and_then(|f| {
             f.default_model
                 .clone()
@@ -738,13 +772,13 @@ struct LegacyProviderOverride {
 
 fn legacy_provider_override(
     file: Option<&ConfigFile>,
-    cli: &Cli,
+    overrides: &ConfigOverrides,
 ) -> Option<LegacyProviderOverride> {
-    let base_url = cli
+    let base_url = overrides
         .base_url
         .clone()
         .or_else(|| file.and_then(|f| f.base_url.clone()));
-    let api_key = cli
+    let api_key = overrides
         .api_key_env
         .as_ref()
         .map(|env| format!("${env}"))

src/conversation.rs

@@ -14,6 +14,10 @@ pub enum Record {
         created_at: String,
         model: String,
         cwd: String,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        parent_chat_id: Option<String>,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        branch_from: Option<BranchPoint>,
     },
     System {
         content: String,
@@ -40,6 +44,15 @@ pub enum Record {
     },
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct BranchPoint {
+    pub chat_id: String,
+    pub record_index: usize,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub tool_call_id: Option<String>,
+    pub checkpoint_label: String,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 pub struct StoredToolCall {
     pub id: String,
@@ -92,6 +105,8 @@ impl Conversation {
             created_at: now_ts(),
             model: model.to_string(),
             cwd: cwd.display().to_string(),
+            parent_chat_id: None,
+            branch_from: None,
         })?;
         convo.append(Record::System {
             content: base_system,
@@ -161,6 +176,37 @@ impl Conversation {
             _ => None,
         })
     }
+
+    pub fn meta(&self) -> Option<ConversationMeta> {
+        self.records.iter().find_map(|r| match r {
+            Record::Meta {
+                chat_id,
+                created_at,
+                model,
+                cwd,
+                parent_chat_id,
+                branch_from,
+            } => Some(ConversationMeta {
+                chat_id: chat_id.clone(),
+                created_at: created_at.clone(),
+                model: model.clone(),
+                cwd: cwd.clone(),
+                parent_chat_id: parent_chat_id.clone(),
+                branch_from: branch_from.clone(),
+            }),
+            _ => None,
+        })
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ConversationMeta {
+    pub chat_id: String,
+    pub created_at: String,
+    pub model: String,
+    pub cwd: String,
+    pub parent_chat_id: Option<String>,
+    pub branch_from: Option<BranchPoint>,
 }
 
 pub fn list_chats(conversations_dir: &Path, cwd: &Path) -> Result<Vec<ChatSummary>> {

src/embedding.rs

@@ -0,0 +1,563 @@
+//! Experimental Rust embedding API for running Cassady without the TUI.
+//!
+//! This module provides the first Rust-native surface for embedding Cassady in
+//! another application. It reuses Cassady's existing runtime behavior while
+//! giving the host application control over event presentation, turn lifecycle,
+//! and approval decisions.
+
+use crate::access::AccessMode;
+use crate::agent::{self, AgentCommand, AgentEvent, AgentSettings};
+use crate::config::{Config, ConfigOverrides, ReasoningEffort};
+use crate::conversation::{self, Conversation, Record};
+use crate::prompt;
+use serde_json::Value;
+use std::collections::BTreeSet;
+use std::fs;
+use std::path::{Path, PathBuf};
+use thiserror::Error;
+use tokio::sync::mpsc;
+use tokio::task::JoinHandle;
+
+const TURN_CANCELLED_MESSAGE: &str = "Turn cancelled by host.";
+const TOOL_CANCELLED_MESSAGE: &str = "Tool execution cancelled by host.";
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug, Error)]
+pub enum Error {
+    #[error("configuration error: {0}")]
+    Config(#[source] anyhow::Error),
+    #[error("conversation error: {0}")]
+    Conversation(#[source] anyhow::Error),
+    #[error("agent error: {0}")]
+    Agent(#[source] anyhow::Error),
+    #[error("agent task failed: {0}")]
+    Join(#[source] tokio::task::JoinError),
+    #[error("turn is already closed")]
+    TurnClosed,
+    #[error("approval request `{0}` is not pending")]
+    ApprovalNotPending(String),
+    #[error("turn session state is unavailable")]
+    MissingSession,
+}
+
+impl Error {
+    fn config(err: anyhow::Error) -> Self {
+        Self::Config(err)
+    }
+
+    fn conversation(err: anyhow::Error) -> Self {
+        Self::Conversation(err)
+    }
+
+    fn agent(err: anyhow::Error) -> Self {
+        Self::Agent(err)
+    }
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct SessionBuilder {
+    config_root: Option<PathBuf>,
+    cwd: Option<PathBuf>,
+    access_mode: Option<AccessMode>,
+    model: Option<String>,
+    base_url: Option<String>,
+    api_key_env: Option<String>,
+    reasoning_effort: Option<ReasoningEffort>,
+}
+
+impl SessionBuilder {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn config_root(mut self, root: impl Into<PathBuf>) -> Self {
+        self.config_root = Some(root.into());
+        self
+    }
+
+    pub fn cwd(mut self, cwd: impl Into<PathBuf>) -> Self {
+        self.cwd = Some(cwd.into());
+        self
+    }
+
+    pub fn access_mode(mut self, mode: AccessMode) -> Self {
+        self.access_mode = Some(mode);
+        self
+    }
+
+    pub fn model(mut self, model: impl Into<String>) -> Self {
+        self.model = Some(model.into());
+        self
+    }
+
+    pub fn base_url(mut self, base_url: impl Into<String>) -> Self {
+        self.base_url = Some(base_url.into());
+        self
+    }
+
+    pub fn api_key_env(mut self, api_key_env: impl Into<String>) -> Self {
+        self.api_key_env = Some(api_key_env.into());
+        self
+    }
+
+    pub fn reasoning_effort(mut self, effort: ReasoningEffort) -> Self {
+        self.reasoning_effort = Some(effort);
+        self
+    }
+
+    pub async fn build(self) -> Result<Session> {
+        self.new_session().await
+    }
+
+    pub async fn new_session(self) -> Result<Session> {
+        let PreparedSession {
+            config,
+            cwd,
+            mode,
+            reasoning_effort,
+        } = self.prepare().await?;
+        let conversation = create_new_conversation(&config, &cwd)?;
+        Ok(Session {
+            config,
+            cwd,
+            mode,
+            reasoning_effort,
+            conversation,
+            resume_warning: None,
+        })
+    }
+
+    pub async fn resume(self, chat_id: impl AsRef<str>) -> Result<Session> {
+        let PreparedSession {
+            config,
+            cwd,
+            mode,
+            reasoning_effort,
+        } = self.prepare().await?;
+        let (conversation, warning) =
+            Conversation::load(&config.conversations_dir(), chat_id.as_ref())
+                .map_err(Error::conversation)?;
+        Ok(Session {
+            config,
+            cwd,
+            mode,
+            reasoning_effort,
+            conversation,
+            resume_warning: warning,
+        })
+    }
+
+    async fn prepare(self) -> Result<PreparedSession> {
+        let root = self.config_root.unwrap_or_else(crate::config::cass_root);
+        let overrides = ConfigOverrides {
+            model: self.model,
+            base_url: self.base_url,
+            api_key_env: self.api_key_env,
+            access_mode: self.access_mode,
+        };
+        let config = Config::load_with_overrides(root, overrides).map_err(Error::config)?;
+        config.resolved_api_key().map_err(Error::config)?;
+        let cwd = resolve_cwd(self.cwd).map_err(Error::config)?;
+        let mode = config.default_access_mode;
+        let reasoning_effort = self
+            .reasoning_effort
+            .unwrap_or(config.reasoning_effort)
+            .clamp_for_model(config.model_metadata.as_ref());
+        Ok(PreparedSession {
+            config,
+            cwd,
+            mode,
+            reasoning_effort,
+        })
+    }
+}
+
+struct PreparedSession {
+    config: Config,
+    cwd: PathBuf,
+    mode: AccessMode,
+    reasoning_effort: ReasoningEffort,
+}
+
+#[derive(Debug)]
+pub struct Session {
+    config: Config,
+    cwd: PathBuf,
+    mode: AccessMode,
+    reasoning_effort: ReasoningEffort,
+    conversation: Conversation,
+    resume_warning: Option<String>,
+}
+
+impl Session {
+    pub fn id(&self) -> &str {
+        &self.conversation.id
+    }
+
+    pub fn cwd(&self) -> &Path {
+        &self.cwd
+    }
+
+    pub fn model(&self) -> &str {
+        &self.config.model
+    }
+
+    pub fn access_mode(&self) -> AccessMode {
+        self.mode
+    }
+
+    pub fn reasoning_effort(&self) -> ReasoningEffort {
+        self.reasoning_effort
+    }
+
+    pub fn conversation_path(&self) -> &Path {
+        &self.conversation.path
+    }
+
+    pub fn records(&self) -> &[Record] {
+        &self.conversation.records
+    }
+
+    pub fn resume_warning(&self) -> Option<&str> {
+        self.resume_warning.as_deref()
+    }
+
+    pub fn info(&self) -> ConversationInfo {
+        ConversationInfo {
+            id: self.conversation.id.clone(),
+            cwd: self.cwd.clone(),
+            model: self.config.model.clone(),
+            access_mode: self.mode,
+            reasoning_effort: self.reasoning_effort,
+            path: self.conversation.path.clone(),
+            record_count: self.conversation.records.len(),
+        }
+    }
+
+    pub async fn start_turn(self, user_message: impl Into<String>) -> Result<Turn> {
+        let message = user_message.into();
+        let turn_start_len = self.conversation.records.len();
+        let (event_tx, event_rx) = mpsc::unbounded_channel::<AgentEvent>();
+        let (command_tx, command_rx) = mpsc::unbounded_channel::<AgentCommand>();
+        let settings = AgentSettings {
+            config: self.config.clone(),
+            cwd: self.cwd.clone(),
+            mode: self.mode,
+            reasoning_effort: self.reasoning_effort,
+        };
+        let conversation = self.conversation.clone();
+        let task_message = message.clone();
+        let handle = tokio::spawn(agent::run_turn_with_commands(
+            conversation,
+            task_message,
+            settings,
+            event_tx,
+            command_rx,
+        ));
+        Ok(Turn {
+            session: Some(self),
+            handle: Some(handle),
+            event_rx,
+            command_tx: Some(command_tx),
+            pending_approvals: BTreeSet::new(),
+            turn_start_len,
+            user_message: message,
+        })
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct ConversationInfo {
+    pub id: String,
+    pub cwd: PathBuf,
+    pub model: String,
+    pub access_mode: AccessMode,
+    pub reasoning_effort: ReasoningEffort,
+    pub path: PathBuf,
+    pub record_count: usize,
+}
+
+#[derive(Debug)]
+pub struct Turn {
+    session: Option<Session>,
+    handle: Option<JoinHandle<anyhow::Result<Conversation>>>,
+    event_rx: mpsc::UnboundedReceiver<AgentEvent>,
+    command_tx: Option<mpsc::UnboundedSender<AgentCommand>>,
+    pending_approvals: BTreeSet<String>,
+    turn_start_len: usize,
+    user_message: String,
+}
+
+impl Turn {
+    pub async fn next_event(&mut self) -> Result<Option<Event>> {
+        match self.event_rx.recv().await {
+            Some(event) => {
+                let event = Event::from_agent(event);
+                match &event {
+                    Event::ApprovalRequested(request) => {
+                        self.pending_approvals.insert(request.request_id.clone());
+                    }
+                    Event::ApprovalResolved { request_id, .. } => {
+                        self.pending_approvals.remove(request_id);
+                    }
+                    _ => {}
+                }
+                Ok(Some(event))
+            }
+            None => Ok(None),
+        }
+    }
+
+    pub fn approve(&mut self, request_id: impl AsRef<str>) -> Result<()> {
+        self.resolve_approval(request_id.as_ref(), true)
+    }
+
+    pub fn deny(&mut self, request_id: impl AsRef<str>) -> Result<()> {
+        self.resolve_approval(request_id.as_ref(), false)
+    }
+
+    pub async fn finish(mut self) -> Result<Session> {
+        let handle = self.handle.take().ok_or(Error::TurnClosed)?;
+        let conversation = match handle.await.map_err(Error::Join)? {
+            Ok(conversation) => conversation,
+            Err(err) => return Err(Error::agent(err)),
+        };
+        let mut session = self.session.take().ok_or(Error::MissingSession)?;
+        session.conversation = conversation;
+        self.command_tx = None;
+        Ok(session)
+    }
+
+    pub async fn cancel(mut self) -> Result<Session> {
+        if let Some(handle) = &self.handle {
+            handle.abort();
+        }
+        if let Some(handle) = self.handle.take() {
+            match handle.await {
+                Ok(Ok(conversation)) => {
+                    let mut session = self.session.take().ok_or(Error::MissingSession)?;
+                    session.conversation = conversation;
+                    self.command_tx = None;
+                    return Ok(session);
+                }
+                Ok(Err(err)) => return Err(Error::agent(err)),
+                Err(err) if err.is_cancelled() => {}
+                Err(err) => return Err(Error::Join(err)),
+            }
+        }
+        let mut session = self.session.take().ok_or(Error::MissingSession)?;
+        session.conversation = finalize_cancelled_turn(
+            &session.config,
+            &session.conversation.id,
+            self.turn_start_len,
+            &self.user_message,
+        )?;
+        self.command_tx = None;
+        Ok(session)
+    }
+
+    fn resolve_approval(&mut self, request_id: &str, approved: bool) -> Result<()> {
+        if !self.pending_approvals.remove(request_id) {
+            return Err(Error::ApprovalNotPending(request_id.to_string()));
+        }
+        let tx = self.command_tx.as_ref().ok_or(Error::TurnClosed)?;
+        tx.send(AgentCommand::ApprovalDecision {
+            request_id: request_id.to_string(),
+            approved,
+        })
+        .map_err(|_| Error::TurnClosed)
+    }
+}
+
+impl Drop for Turn {
+    fn drop(&mut self) {
+        if let Some(handle) = &self.handle {
+            handle.abort();
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum Event {
+    AssistantChunk(String),
+    ReasoningChunk(String),
+    ToolCallStarted {
+        id: String,
+        name: String,
+        arguments: Value,
+    },
+    ToolOutputChunk {
+        id: String,
+        name: String,
+        stream: String,
+        content: String,
+    },
+    ToolResult {
+        id: String,
+        name: String,
+        ok: bool,
+        content: String,
+    },
+    ApprovalRequested(ApprovalRequest),
+    ApprovalResolved {
+        request_id: String,
+        approved: bool,
+    },
+    Status(String),
+    Finished,
+}
+
+impl Event {
+    fn from_agent(event: AgentEvent) -> Self {
+        match event {
+            AgentEvent::AssistantChunk(text) => Self::AssistantChunk(text),
+            AgentEvent::ReasoningChunk(text) => Self::ReasoningChunk(text),
+            AgentEvent::ToolCallStarted {
+                id,
+                name,
+                arguments,
+            } => Self::ToolCallStarted {
+                id,
+                name,
+                arguments,
+            },
+            AgentEvent::ToolOutputChunk {
+                id,
+                name,
+                stream,
+                content,
+            } => Self::ToolOutputChunk {
+                id,
+                name,
+                stream,
+                content,
+            },
+            AgentEvent::ToolResult {
+                id,
+                name,
+                ok,
+                content,
+            } => Self::ToolResult {
+                id,
+                name,
+                ok,
+                content,
+            },
+            AgentEvent::ApprovalRequested {
+                request_id,
+                tool_call_id,
+                name,
+                arguments,
+                reason,
+            } => Self::ApprovalRequested(ApprovalRequest {
+                request_id,
+                tool_call_id,
+                name,
+                arguments,
+                reason,
+            }),
+            AgentEvent::ApprovalResolved {
+                request_id,
+                approved,
+            } => Self::ApprovalResolved {
+                request_id,
+                approved,
+            },
+            AgentEvent::Status(status) => Self::Status(status),
+            AgentEvent::TurnFinished => Self::Finished,
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct ApprovalRequest {
+    pub request_id: String,
+    pub tool_call_id: String,
+    pub name: String,
+    pub arguments: Value,
+    pub reason: String,
+}
+
+fn resolve_cwd(cwd: Option<PathBuf>) -> anyhow::Result<PathBuf> {
+    let cwd = cwd.unwrap_or(std::env::current_dir()?);
+    cwd.canonicalize()
+        .map_err(anyhow::Error::from)
+        .map_err(|err| anyhow::anyhow!("resolving cwd {}: {err}", cwd.display()))
+}
+
+fn create_new_conversation(config: &Config, cwd: &Path) -> Result<Conversation> {
+    let global = fs::read_to_string(config.global_path()).ok();
+    let base = prompt::build_base_system_prompt(global.as_deref());
+    Conversation::create(&config.conversations_dir(), &config.model, cwd, base)
+        .map_err(Error::conversation)
+}
+
+fn finalize_cancelled_turn(
+    config: &Config,
+    chat_id: &str,
+    turn_start_len: usize,
+    turn_message: &str,
+) -> Result<Conversation> {
+    let (mut conversation, _) =
+        Conversation::load(&config.conversations_dir(), chat_id).map_err(Error::conversation)?;
+
+    if conversation.records.len() <= turn_start_len {
+        conversation
+            .append(Record::User {
+                content: turn_message.to_string(),
+                ts: conversation::now_ts(),
+            })
+            .map_err(Error::conversation)?;
+    }
+
+    for (id, name) in pending_tool_calls(&conversation.records) {
+        conversation
+            .append(Record::Tool {
+                tool_call_id: id,
+                name,
+                ok: false,
+                content: TOOL_CANCELLED_MESSAGE.to_string(),
+                ts: conversation::now_ts(),
+            })
+            .map_err(Error::conversation)?;
+    }
+
+    if !matches!(
+        conversation.records.last(),
+        Some(Record::Assistant { content, tool_calls, .. })
+            if content == TURN_CANCELLED_MESSAGE && tool_calls.is_empty()
+    ) {
+        conversation
+            .append(Record::Assistant {
+                content: TURN_CANCELLED_MESSAGE.to_string(),
+                reasoning: String::new(),
+                reasoning_field: None,
+                tool_calls: Vec::new(),
+                ts: conversation::now_ts(),
+            })
+            .map_err(Error::conversation)?;
+    }
+
+    Ok(conversation)
+}
+
+fn pending_tool_calls(records: &[Record]) -> Vec<(String, String)> {
+    let mut pending = Vec::new();
+    for record in records {
+        match record {
+            Record::Assistant { tool_calls, .. } => {
+                pending = tool_calls
+                    .iter()
+                    .map(|call| (call.id.clone(), call.name.clone()))
+                    .collect();
+            }
+            Record::Tool { tool_call_id, .. } => {
+                pending.retain(|(id, _)| id != tool_call_id);
+            }
+            Record::User { .. } => pending.clear(),
+            _ => {}
+        }
+    }
+    pending
+}

src/file_edits.rs

@@ -0,0 +1,470 @@
+use crate::tools::{self, ToolContext};
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+use sha2::{Digest, Sha256};
+use std::collections::BTreeMap;
+use std::fs::{self, OpenOptions};
+use std::io::Write;
+use std::path::{Path, PathBuf};
+
+const MAX_SNAPSHOT_BYTES: u64 = 10 * 1024 * 1024;
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct FileEditJournalEntry {
+    pub chat_id: String,
+    pub record_index: usize,
+    pub tool_call_id: String,
+    pub tool_name: String,
+    pub path: PathBuf,
+    pub existed_before: bool,
+    pub existed_after: bool,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub before_hash: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub after_hash: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub before_snapshot: Option<PathBuf>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub after_snapshot: Option<PathBuf>,
+    pub ts: String,
+}
+
+#[derive(Debug, Clone)]
+pub struct PendingFileEditSnapshot {
+    pub chat_id: String,
+    pub record_index: usize,
+    pub tool_call_id: String,
+    pub tool_name: String,
+    pub path: PathBuf,
+    before: SnapshotState,
+}
+
+#[derive(Debug, Clone)]
+enum SnapshotState {
+    Missing,
+    File { bytes: Vec<u8>, hash: String },
+    Unsupported,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct RestorePlan {
+    pub actions: Vec<RestoreAction>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum RestoreAction {
+    Write {
+        path: PathBuf,
+        snapshot: PathBuf,
+        desired_hash: String,
+        expected_current_hash: Option<String>,
+        conflict: bool,
+    },
+    Delete {
+        path: PathBuf,
+        expected_current_hash: Option<String>,
+        conflict: bool,
+    },
+    Skip {
+        path: PathBuf,
+        reason: String,
+    },
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct RestoreOutcome {
+    pub applied: usize,
+    pub skipped: usize,
+    pub conflicts: usize,
+}
+
+pub fn begin_tool_edit(
+    cass_root: &Path,
+    chat_id: &str,
+    record_index: usize,
+    tool_call_id: &str,
+    tool_name: &str,
+    args: &Value,
+    ctx: &ToolContext,
+) -> Option<PendingFileEditSnapshot> {
+    if !matches!(tool_name, "write" | "edit") {
+        return None;
+    }
+    let path_arg = args.get("path")?.as_str()?;
+    let path =
+        tools::path::resolve_for_write(path_arg, &ctx.cwd, ctx.mode, &ctx.blocked_write_roots)
+            .ok()?;
+    let before = snapshot_state(&path).unwrap_or(SnapshotState::Unsupported);
+    // Ensure journal directories are creatable before executing, but do not fail
+    // the tool if Cassady cannot journal; restore will simply be unavailable.
+    let _ = fs::create_dir_all(cass_root.join("file-edits"));
+    let _ = fs::create_dir_all(cass_root.join("file-snapshots"));
+    Some(PendingFileEditSnapshot {
+        chat_id: chat_id.to_string(),
+        record_index,
+        tool_call_id: tool_call_id.to_string(),
+        tool_name: tool_name.to_string(),
+        path,
+        before,
+    })
+}
+
+pub fn finish_tool_edit(cass_root: &Path, pending: PendingFileEditSnapshot) -> Result<()> {
+    let after = snapshot_state(&pending.path).unwrap_or(SnapshotState::Unsupported);
+    if matches!(pending.before, SnapshotState::Unsupported)
+        || matches!(after, SnapshotState::Unsupported)
+    {
+        return Ok(());
+    }
+    if same_state(&pending.before, &after) {
+        return Ok(());
+    }
+
+    let (existed_before, before_hash, before_snapshot) = store_snapshot(
+        cass_root,
+        &pending.chat_id,
+        &pending.tool_call_id,
+        "before",
+        &pending.before,
+    )?;
+    let (existed_after, after_hash, after_snapshot) = store_snapshot(
+        cass_root,
+        &pending.chat_id,
+        &pending.tool_call_id,
+        "after",
+        &after,
+    )?;
+
+    let entry = FileEditJournalEntry {
+        chat_id: pending.chat_id.clone(),
+        record_index: pending.record_index,
+        tool_call_id: pending.tool_call_id,
+        tool_name: pending.tool_name,
+        path: pending.path,
+        existed_before,
+        existed_after,
+        before_hash,
+        after_hash,
+        before_snapshot,
+        after_snapshot,
+        ts: crate::conversation::now_ts(),
+    };
+    append_journal(cass_root, &pending.chat_id, &entry)
+}
+
+pub fn load_journal(cass_root: &Path, chat_id: &str) -> Result<Vec<FileEditJournalEntry>> {
+    let path = journal_path(cass_root, chat_id);
+    if !path.exists() {
+        return Ok(Vec::new());
+    }
+    let content =
+        fs::read_to_string(&path).with_context(|| format!("reading {}", path.display()))?;
+    let mut out = Vec::new();
+    for (idx, line) in content.lines().enumerate() {
+        if line.trim().is_empty() {
+            continue;
+        }
+        let entry: FileEditJournalEntry = serde_json::from_str(line)
+            .with_context(|| format!("parsing {} line {}", path.display(), idx + 1))?;
+        out.push(entry);
+    }
+    out.sort_by_key(|entry| entry.record_index);
+    Ok(out)
+}
+
+pub fn plan_restore(
+    cass_root: &Path,
+    chat_id: &str,
+    target_record_index: usize,
+) -> Result<RestorePlan> {
+    let entries = load_journal(cass_root, chat_id)?;
+    let mut by_path: BTreeMap<PathBuf, Vec<FileEditJournalEntry>> = BTreeMap::new();
+    for entry in entries {
+        by_path.entry(entry.path.clone()).or_default().push(entry);
+    }
+
+    let mut actions = Vec::new();
+    for (path, mut entries) in by_path {
+        entries.sort_by_key(|entry| entry.record_index);
+        let latest = entries.last().cloned();
+        let desired = entries
+            .iter()
+            .rev()
+            .find(|entry| entry.record_index <= target_record_index)
+            .cloned();
+        let first_after = entries
+            .iter()
+            .find(|entry| entry.record_index > target_record_index)
+            .cloned();
+
+        let (want_exists, want_hash, want_snapshot) = if let Some(entry) = desired {
+            (entry.existed_after, entry.after_hash, entry.after_snapshot)
+        } else if let Some(entry) = first_after {
+            (
+                entry.existed_before,
+                entry.before_hash,
+                entry.before_snapshot,
+            )
+        } else {
+            continue;
+        };
+
+        let expected_current_hash = latest.and_then(|entry| entry.after_hash);
+        let current_hash = hash_existing_file(&path)?;
+        let conflict = expected_current_hash.is_some()
+            && current_hash.is_some()
+            && expected_current_hash != current_hash;
+
+        if want_exists {
+            match (want_hash, want_snapshot) {
+                (Some(desired_hash), Some(snapshot)) => actions.push(RestoreAction::Write {
+                    path,
+                    snapshot,
+                    desired_hash,
+                    expected_current_hash,
+                    conflict,
+                }),
+                _ => actions.push(RestoreAction::Skip {
+                    path,
+                    reason: "missing desired snapshot".into(),
+                }),
+            }
+        } else {
+            let conflict = conflict
+                || (current_hash.is_some()
+                    && expected_current_hash.is_none()
+                    && current_hash != expected_current_hash);
+            actions.push(RestoreAction::Delete {
+                path,
+                expected_current_hash,
+                conflict,
+            });
+        }
+    }
+
+    Ok(RestorePlan { actions })
+}
+
+pub fn apply_restore_plan(plan: &RestorePlan) -> Result<RestoreOutcome> {
+    let mut outcome = RestoreOutcome {
+        applied: 0,
+        skipped: 0,
+        conflicts: 0,
+    };
+    for action in &plan.actions {
+        match action {
+            RestoreAction::Write {
+                path,
+                snapshot,
+                conflict,
+                ..
+            } => {
+                if *conflict {
+                    outcome.conflicts += 1;
+                    continue;
+                }
+                let bytes = fs::read(snapshot)
+                    .with_context(|| format!("reading snapshot {}", snapshot.display()))?;
+                crate::tools::write::atomic_write(path, &bytes)
+                    .with_context(|| format!("restoring {}", path.display()))?;
+                outcome.applied += 1;
+            }
+            RestoreAction::Delete { path, conflict, .. } => {
+                if *conflict {
+                    outcome.conflicts += 1;
+                    continue;
+                }
+                if path.exists() {
+                    fs::remove_file(path)
+                        .with_context(|| format!("deleting {}", path.display()))?;
+                    outcome.applied += 1;
+                } else {
+                    outcome.skipped += 1;
+                }
+            }
+            RestoreAction::Skip { .. } => outcome.skipped += 1,
+        }
+    }
+    Ok(outcome)
+}
+
+pub fn summarize_plan(plan: &RestorePlan) -> String {
+    if plan.actions.is_empty() {
+        return "No tracked file edits need restoration for this checkpoint.".into();
+    }
+    let mut lines = Vec::new();
+    for action in &plan.actions {
+        match action {
+            RestoreAction::Write { path, conflict, .. } => lines.push(format!(
+                "{} update {}",
+                if *conflict { "CONFLICT" } else { "will" },
+                path.display()
+            )),
+            RestoreAction::Delete { path, conflict, .. } => lines.push(format!(
+                "{} delete {}",
+                if *conflict { "CONFLICT" } else { "will" },
+                path.display()
+            )),
+            RestoreAction::Skip { path, reason } => {
+                lines.push(format!("skip {}: {reason}", path.display()))
+            }
+        }
+    }
+    lines.join("\n")
+}
+
+fn snapshot_state(path: &Path) -> Result<SnapshotState> {
+    match fs::metadata(path) {
+        Ok(metadata) => {
+            if !metadata.is_file() || metadata.len() > MAX_SNAPSHOT_BYTES {
+                return Ok(SnapshotState::Unsupported);
+            }
+            let bytes = fs::read(path)?;
+            let hash = sha256_hex(&bytes);
+            Ok(SnapshotState::File { bytes, hash })
+        }
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound => Ok(SnapshotState::Missing),
+        Err(err) => Err(err.into()),
+    }
+}
+
+fn same_state(a: &SnapshotState, b: &SnapshotState) -> bool {
+    match (a, b) {
+        (SnapshotState::Missing, SnapshotState::Missing) => true,
+        (SnapshotState::File { hash: a, .. }, SnapshotState::File { hash: b, .. }) => a == b,
+        _ => false,
+    }
+}
+
+fn store_snapshot(
+    cass_root: &Path,
+    chat_id: &str,
+    tool_call_id: &str,
+    side: &str,
+    state: &SnapshotState,
+) -> Result<(bool, Option<String>, Option<PathBuf>)> {
+    match state {
+        SnapshotState::Missing => Ok((false, None, None)),
+        SnapshotState::Unsupported => Ok((false, None, None)),
+        SnapshotState::File { bytes, hash } => {
+            let dir = cass_root
+                .join("file-snapshots")
+                .join(chat_id)
+                .join(tool_call_id);
+            fs::create_dir_all(&dir)?;
+            let path = dir.join(format!("{side}-{hash}.bin"));
+            if !path.exists() {
+                fs::write(&path, bytes)?;
+            }
+            Ok((true, Some(hash.clone()), Some(path)))
+        }
+    }
+}
+
+fn append_journal(cass_root: &Path, chat_id: &str, entry: &FileEditJournalEntry) -> Result<()> {
+    let path = journal_path(cass_root, chat_id);
+    if let Some(parent) = path.parent() {
+        fs::create_dir_all(parent)?;
+    }
+    let mut file = OpenOptions::new().create(true).append(true).open(&path)?;
+    writeln!(file, "{}", serde_json::to_string(entry)?)?;
+    file.flush()?;
+    Ok(())
+}
+
+fn journal_path(cass_root: &Path, chat_id: &str) -> PathBuf {
+    cass_root
+        .join("file-edits")
+        .join(format!("{chat_id}.jsonl"))
+}
+
+fn hash_existing_file(path: &Path) -> Result<Option<String>> {
+    match fs::metadata(path) {
+        Ok(metadata) => {
+            if !metadata.is_file() || metadata.len() > MAX_SNAPSHOT_BYTES {
+                return Ok(None);
+            }
+            Ok(Some(sha256_hex(&fs::read(path)?)))
+        }
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound => Ok(None),
+        Err(err) => Err(err.into()),
+    }
+}
+
+fn sha256_hex(bytes: &[u8]) -> String {
+    let digest = Sha256::digest(bytes);
+    digest.iter().map(|b| format!("{b:02x}")).collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::access::AccessMode;
+    use tempfile::tempdir;
+
+    fn tool_ctx(cwd: &Path) -> ToolContext {
+        ToolContext {
+            mode: AccessMode::WorkspaceEdit,
+            cwd: cwd.to_path_buf(),
+            read_roots: vec![cwd.to_path_buf()],
+            blocked_write_roots: Vec::new(),
+            model_result_limit: 1000,
+            runtime_tx: None,
+        }
+    }
+
+    #[test]
+    fn journal_and_restore_rewinds_write() {
+        let root = tempdir().unwrap();
+        let work = tempdir().unwrap();
+        let path = work.path().join("a.txt");
+        fs::write(&path, "old").unwrap();
+        let ctx = tool_ctx(work.path());
+        let pending = begin_tool_edit(
+            root.path(),
+            "chat",
+            3,
+            "call",
+            "write",
+            &serde_json::json!({"path":"a.txt"}),
+            &ctx,
+        )
+        .unwrap();
+        fs::write(&path, "new").unwrap();
+        finish_tool_edit(root.path(), pending).unwrap();
+
+        let plan = plan_restore(root.path(), "chat", 2).unwrap();
+        assert_eq!(plan.actions.len(), 1);
+        let outcome = apply_restore_plan(&plan).unwrap();
+        assert_eq!(outcome.applied, 1);
+        assert_eq!(fs::read_to_string(&path).unwrap(), "old");
+    }
+
+    #[test]
+    fn restore_detects_external_conflict() {
+        let root = tempdir().unwrap();
+        let work = tempdir().unwrap();
+        let path = work.path().join("a.txt");
+        fs::write(&path, "old").unwrap();
+        let ctx = tool_ctx(work.path());
+        let pending = begin_tool_edit(
+            root.path(),
+            "chat",
+            3,
+            "call",
+            "write",
+            &serde_json::json!({"path":"a.txt"}),
+            &ctx,
+        )
+        .unwrap();
+        fs::write(&path, "new").unwrap();
+        finish_tool_edit(root.path(), pending).unwrap();
+        fs::write(&path, "manual").unwrap();
+        let plan = plan_restore(root.path(), "chat", 2).unwrap();
+        assert!(matches!(
+            &plan.actions[0],
+            RestoreAction::Write { conflict: true, .. }
+        ));
+    }
+}

src/lib.rs

@@ -1,19 +1,24 @@
 pub mod access;
 pub mod agent;
 pub mod app;
+pub mod branch;
 pub mod check;
 pub mod cli;
 pub mod config;
 pub mod conversation;
 pub mod docs;
+pub mod embedding;
 pub mod error;
+pub mod file_edits;
 pub mod menu;
+pub mod prelude;
 pub mod prompt;
 pub mod providers;
 pub mod security;
 pub mod setup;
 pub mod tools;
 pub mod ui;
+pub mod update;
 
 pub async fn run() -> anyhow::Result<()> {
     app::run().await

src/prelude.rs

@@ -0,0 +1,7 @@
+//! Common imports for Cassady's experimental Rust embedding API.
+
+pub use crate::access::AccessMode;
+pub use crate::config::ReasoningEffort;
+pub use crate::embedding::{
+    ApprovalRequest, ConversationInfo, Event, Session, SessionBuilder, Turn,
+};

src/prompt.rs

@@ -3,20 +3,33 @@ use std::path::Path;
 
 pub fn build_base_system_prompt(global: Option<&str>) -> String {
     let mut prompt = String::new();
-    prompt.push_str("1. Identity and operating style\n\n");
-    prompt.push_str("You are Cassady, also called Cass, a minimal coding agent running in a terminal chat interface. Work carefully, inspect files before changing them, explain concise next steps, and avoid unnecessary ceremony.\n\n");
+    prompt.push_str(
+        "# Cassady operating instructions\n\n\
+## Role\n\
+You are Cassady, also called Cass, a coding assistant running in an interactive terminal chat. Help with real project work: read and explain code, inspect behavior, make targeted file changes, and run relevant project commands when allowed. Work carefully and honestly; do not claim that files were read, commands ran, or edits succeeded until tool results confirm it.\n\n\
+## Working style\n\
+Make the smallest useful plan, then act. Prefer current project evidence over guesses, and inspect relevant files before making claims or edits. When information is missing, gather it with tools if possible; ask a focused follow-up question only when a user choice, secret, or missing requirement blocks progress. If the task is impossible in the current access mode, explain the limitation and the next viable step. Keep explanations concise while giving enough context for review.\n\n",
+    );
 
     if let Some(global) = global.map(str::trim).filter(|s| !s.is_empty()) {
-        prompt.push_str("2. User global instructions\n\n");
-        prompt.push_str("The following additional instructions were provided by the user. Follow them when they do not conflict with runtime safety constraints.\n\n");
+        prompt.push_str("## User global instructions\n");
+        prompt.push_str(
+            "The following user-provided instructions apply to new chats. Follow them when they are consistent with the active user request and runtime safety constraints; they cannot override access modes, tool denials, approvals, or workspace boundaries.\n\n",
+        );
         prompt.push_str(global);
         prompt.push_str("\n\n");
     }
 
-    prompt.push_str("3. Tool-use style\n\n");
-    prompt.push_str("Use tools when you need current filesystem context. Prefer targeted inspection over guessing. Batch related reads into one read call when possible. Use grep before read when a directory or file may be too large to inspect directly. Do not ask the user in chat for permission before making a tool call; request the tool directly when it is the right next step. Cass enforces access policy at runtime and will allow, deny, or show a separate approval UI as needed.\n\n");
-    prompt.push_str("4. Editing style\n\n");
-    prompt.push_str("Use edit for targeted changes. Each edit must identify exact old text that appears uniquely in the file and replacement text. Do not use write to make small modifications to existing files unless a full rewrite is intentionally safer.\n");
+    prompt.push_str(
+        "## Transcript and tools\n\
+Assistant text is streamed to the user. Tool calls, tool results, edit diffs, denials, and approval prompts are visible in the transcript. Request tools directly when they are the right next step; Cassady enforces access policy and shows approval UI separately. Do not ask for chat permission before every tool call, and do not say a tool succeeded before its result arrives. If a tool fails or is denied, adapt instead of repeating the same request.\n\n\
+## Tool use\n\
+Use tools when the current filesystem or command result matters. Use `ls` for directory orientation, `grep` to locate definitions/usages or inspect large or unknown areas before opening files, `read` for relevant files or ranges, `edit` for focused changes to existing files, `write` for new files or intentional full rewrites, and `shell` for tests, builds, formatting, diagnostics, or project commands when allowed and useful. Prefer targeted inspection and related batched reads over broad exploration. Do not use `shell` for file inspection when `ls`, `grep`, or `read` is safer and sufficient.\n\n\
+## Editing\n\
+Inspect before editing. Prefer `edit` for small and medium modifications to existing files. For `edit`, each old text must match exactly and uniquely in the original file; keep replacements minimal, unique, and non-overlapping, and combine related replacements for the same file in one call when practical. Use `write` only for new files or full rewrites where that is safer and intentional. After meaningful code changes, run relevant tests or formatters when allowed, or tell the user what should be run.\n\n\
+## Safety and final response\n\
+Follow runtime constraints, active access mode, tool availability, and tool results as authoritative. Do not try to bypass workspace boundaries, read-only docs rules, approval requirements, or denials. End every turn with a concise user-facing response after tool work; do not finish with only tool calls. Summarize what changed, where, and how it was verified, or summarize findings, blockers, skipped tests, and assumptions if no change was made.\n",
+    );
     prompt
 }
 
@@ -30,23 +43,43 @@ pub fn build_effective_system_prompt(
 ) -> String {
     let mut prompt = String::new();
     prompt.push_str(base.trim_end());
-    prompt.push_str("\n\n5. Current runtime constraints\n\n");
+    prompt.push_str("\n\n## Runtime context\n");
     prompt.push_str(&format!("Model: {model}.\n"));
     prompt.push_str(&format!("Access mode: {}.\n", mode.as_str()));
     prompt.push_str(&format!("Launch working directory: {}.\n", cwd.display()));
     prompt.push_str(&format!(
-        "Bundled Cass docs directory: {}. This directory is read-only for tools. Use ls, read, and grep there when you need Cass documentation.\n",
+        "Bundled Cass docs directory: {}. Use this directory for Cass documentation; write/edit are blocked there.\n",
         docs_dir.display()
     ));
     prompt.push_str(&format!(
         "Allowed tools this turn: {}.\n\n",
-        allowed_tools.join(", ")
+        render_allowed_tools(allowed_tools)
     ));
+
+    prompt.push_str("## Access rules for this session\n");
     match mode {
-        AccessMode::ReadOnly => prompt.push_str("In read-only mode, you may inspect files with ls, read, and grep only inside the launch working directory or bundled Cass docs directory. Do not request write, edit, or shell. If a task requires modification, explain that a more permissive mode is needed.\n\n"),
-        AccessMode::WorkspaceEdit => prompt.push_str("In workspace-edit mode, you may inspect files with ls, read, and grep only inside the launch working directory or bundled Cass docs directory. You may write and edit files only inside the launch working directory. Bundled Cass docs are read-only. You may request shell when useful. Do not ask the user for shell permission in chat; call the shell tool directly and Cass will handle any required approval separately before execution.\n\n"),
-        AccessMode::FullAccess => prompt.push_str("In full-access mode, you may request ls, read, grep, write, edit, and shell when needed. The shell tool runs commands in the launch working directory. Cass does not restrict read paths to the launch directory, but normal operating-system permissions still apply. write and edit are still blocked under the bundled Cass docs directory.\n\n"),
+        AccessMode::ReadOnly => prompt.push_str(
+            "Read-only mode permits inspection only. Use `ls`, `read`, and `grep` only inside the launch workspace or bundled Cass docs directory. Do not request `write`, `edit`, or `shell`. If changes, commands, or out-of-scope paths are needed, explain that a more permissive access mode is required.\n\n",
+        ),
+        AccessMode::WorkspaceEdit => prompt.push_str(
+            "Workspace-edit mode permits `ls`, `read`, and `grep` inside the launch workspace and bundled Cass docs directory. Write/edit only inside the launch workspace; bundled docs remain read-only. Shell may be requested when useful, but Cassady handles the approval UI, so do not ask for shell permission in chat first. If a path escapes the workspace, choose an in-workspace alternative or explain the limitation.\n\n",
+        ),
+        AccessMode::FullAccess => prompt.push_str(
+            "Full-access mode permits `ls`, `read`, `grep`, `write`, `edit`, and `shell` when needed. Shell runs from the launch working directory, and normal operating-system permissions still apply. Bundled docs remain read-only for write/edit. Even in full-access, keep changes targeted and avoid destructive commands unless the user explicitly requested them and they are necessary.\n\n",
+        ),
     }
-    prompt.push_str("6. Response behavior\n\nAssistant output is streamed to the user. Keep user-facing text direct and useful. Tool calls and results are visible to the user, so avoid claiming work happened until the relevant tool result confirms it. After using tools or completing requested work, always end the turn with a concise final user-facing response. Do not finish a turn with only tool calls.\n");
+
+    prompt.push_str(
+        "## Runtime authority\n\
+Runtime policy and tool results override general guidance and user global instructions. The allowed-tools list is the source of truth for this turn; if Cassady denies a tool or path, adapt and report the limitation. Always provide a concise final response after tool activity.\n",
+    );
     prompt
 }
+
+fn render_allowed_tools(allowed_tools: &[String]) -> String {
+    if allowed_tools.is_empty() {
+        "<none>".into()
+    } else {
+        allowed_tools.join(", ")
+    }
+}

src/ui/render.rs

@@ -5,7 +5,7 @@ use crate::ui::theme;
 use pulldown_cmark::{CodeBlockKind, Event, HeadingLevel, Parser, Tag, TagEnd};
 use ratatui::layout::{Constraint, Direction, Layout};
 use ratatui::prelude::*;
-use ratatui::widgets::{Paragraph, Wrap};
+use ratatui::widgets::{Block, Borders, Clear, Paragraph, Wrap};
 use std::path::Path;
 use unicode_width::UnicodeWidthChar;
 
@@ -26,7 +26,20 @@ pub struct TranscriptBlock {
     pub content: String,
 }
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
+pub struct OverlayView {
+    pub title: String,
+    pub help: String,
+    pub items: Vec<OverlayItem>,
+    pub selected: usize,
+}
+
+#[derive(Debug, Clone)]
+pub struct OverlayItem {
+    pub label: String,
+    pub detail: String,
+}
+
 pub struct RenderState<'a> {
     pub app_name: &'a str,
     pub chat_id: &'a str,
@@ -42,6 +55,7 @@ pub struct RenderState<'a> {
     pub reasoning_effort: ReasoningEffort,
     pub scroll: u16,
     pub autofill: Option<&'a AutoFillMenu>,
+    pub overlay: Option<&'a OverlayView>,
 }
 
 pub fn render(f: &mut Frame<'_>, state: &RenderState<'_>) {
@@ -74,6 +88,10 @@ pub fn render(f: &mut Frame<'_>, state: &RenderState<'_>) {
 
     let footer = truncate_end(&footer_text(state), chunks[3].width as usize);
     f.render_widget(Paragraph::new(footer).style(theme::footer()), chunks[3]);
+
+    if let Some(overlay) = state.overlay {
+        render_overlay(f, f.area(), overlay);
+    }
 }
 
 pub fn transcript_area(area: Rect, input: &str) -> Rect {
@@ -116,6 +134,61 @@ fn autofill_height(menu: Option<&AutoFillMenu>) -> u16 {
     menu.map(|menu| menu.items.len().min(6) as u16).unwrap_or(0)
 }
 
+fn render_overlay(f: &mut Frame<'_>, area: Rect, overlay: &OverlayView) {
+    let max_width = area.width.max(1);
+    let preferred_width = area.width.saturating_mul(4).saturating_div(5).max(40);
+    let width = preferred_width.min(max_width);
+    let max_height = area.height.saturating_sub(2).max(1);
+    let preferred_height = (overlay.items.len() as u16 + 5).max(8);
+    let height = preferred_height.min(max_height);
+    let x = area.x + area.width.saturating_sub(width) / 2;
+    let y = area.y + area.height.saturating_sub(height) / 2;
+    let rect = Rect::new(x, y, width, height);
+    f.render_widget(Clear, rect);
+    let block = Block::default()
+        .title(overlay.title.clone())
+        .borders(Borders::ALL)
+        .style(theme::menu());
+    let inner = block.inner(rect);
+    f.render_widget(block, rect);
+
+    let visible = inner.height.saturating_sub(2) as usize;
+    let selected = overlay.selected.min(overlay.items.len().saturating_sub(1));
+    let start = if selected >= visible && visible > 0 {
+        selected + 1 - visible
+    } else {
+        0
+    };
+    let end = (start + visible).min(overlay.items.len());
+    let mut lines = Vec::new();
+    lines.push(Line::styled(
+        truncate_end(&overlay.help, inner.width as usize),
+        Style::default().fg(Color::DarkGray),
+    ));
+    for idx in start..end {
+        let item = &overlay.items[idx];
+        let marker = if idx == selected { "›" } else { " " };
+        let mut text = format!("{marker} {}", item.label);
+        if !item.detail.is_empty() {
+            text.push_str("  ");
+            text.push_str(&item.detail);
+        }
+        let style = if idx == selected {
+            theme::selection()
+        } else {
+            theme::menu()
+        };
+        lines.push(Line::styled(
+            truncate_end(&text, inner.width as usize),
+            style,
+        ));
+    }
+    f.render_widget(
+        Paragraph::new(Text::from(lines)).wrap(Wrap { trim: false }),
+        inner,
+    );
+}
+
 fn render_autofill_menu(f: &mut Frame<'_>, area: Rect, menu: &AutoFillMenu) {
     if area.height == 0 || menu.items.is_empty() {
         return;

tests/conversation_tests.rs

@@ -23,3 +23,22 @@ fn conversation_appends_loads_and_lists_by_cwd() {
     assert_eq!(chats[0].id, convo.id);
     assert_eq!(chats[0].first_user_preview, "hello world");
 }
+
+#[test]
+fn legacy_meta_without_branch_fields_still_loads() {
+    let root = tempdir().unwrap();
+    let id = "legacy";
+    std::fs::write(
+        root.path().join(format!("{id}.jsonl")),
+        r#"{"type":"meta","chat_id":"legacy","created_at":"now","model":"m","cwd":"/tmp"}
+{"type":"system","content":"base"}
+"#,
+    )
+    .unwrap();
+
+    let (loaded, warning) = Conversation::load(root.path(), id).unwrap();
+    assert!(warning.is_none());
+    let meta = loaded.meta().unwrap();
+    assert_eq!(meta.parent_chat_id, None);
+    assert_eq!(meta.branch_from, None);
+}

tests/docs_tests.rs

@@ -59,6 +59,7 @@ fn expected_bundled_docs_exist() {
         "configuration.md",
         "providers.md",
         "access-modes.md",
+        "embedding.md",
         "workflows.md",
         "troubleshooting.md",
         "platforms.md",

tests/embedding_tests.rs

@@ -0,0 +1,315 @@
+use cassady::access::AccessMode;
+use cassady::config::ReasoningEffort;
+use cassady::conversation::Record;
+use cassady::embedding::{Event, SessionBuilder};
+use serde_json::json;
+use tempfile::tempdir;
+use wiremock::matchers::{body_string_contains, method, path};
+use wiremock::{Mock, MockServer, ResponseTemplate};
+
+fn sse(body: &str) -> ResponseTemplate {
+    ResponseTemplate::new(200).set_body_raw(body.as_bytes().to_vec(), "text/event-stream")
+}
+
+fn content_sse(content: &str) -> ResponseTemplate {
+    sse(&format!(
+        "data: {{\"choices\":[{{\"index\":0,\"delta\":{{\"content\":{}}}}}]}}\r\n\r\ndata: [DONE]\r\n\r\n",
+        serde_json::to_string(content).unwrap()
+    ))
+}
+
+fn tool_call_sse(id: &str, name: &str, arguments: &str) -> ResponseTemplate {
+    sse(&format!(
+        "data: {{\"choices\":[{{\"index\":0,\"delta\":{{\"tool_calls\":[{{\"index\":0,\"id\":\"{id}\",\"type\":\"function\",\"function\":{{\"name\":\"{name}\",\"arguments\":{}}}}}]}}}}]}}\r\n\r\ndata: [DONE]\r\n\r\n",
+        serde_json::to_string(arguments).unwrap()
+    ))
+}
+
+fn write_test_config(root: &std::path::Path, base_url: &str) {
+    std::fs::write(
+        root.join("providers.json"),
+        serde_json::to_string_pretty(&json!({
+            "providers": [{
+                "id": "test-provider",
+                "kind": "openai-compatible",
+                "base_url": base_url,
+                "api_key": "test-key",
+                "default_model": "test-model",
+                "models": ["test-model"]
+            }]
+        }))
+        .unwrap(),
+    )
+    .unwrap();
+    std::fs::write(
+        root.join("models.json"),
+        serde_json::to_string_pretty(&json!({
+            "models": [{
+                "id": "test-model",
+                "provider": "test-provider",
+                "context_length": 128,
+                "max_output_tokens": 64,
+                "reasoning": {
+                    "supported": true,
+                    "required": false,
+                    "default_effort": "off",
+                    "request_format": "reasoning_effort"
+                }
+            }]
+        }))
+        .unwrap(),
+    )
+    .unwrap();
+    std::fs::write(
+        root.join("config.json"),
+        serde_json::to_string_pretty(&json!({
+            "default_provider": "test-provider",
+            "default_model": "test-model",
+            "default_reasoning_effort": "off"
+        }))
+        .unwrap(),
+    )
+    .unwrap();
+}
+
+#[tokio::test]
+async fn embedded_session_runs_turn_and_streams_events() {
+    let server = MockServer::start().await;
+    Mock::given(method("POST"))
+        .and(path("/chat/completions"))
+        .respond_with(content_sse("Hello from embedded Cassady."))
+        .expect(1)
+        .mount(&server)
+        .await;
+
+    let root = tempdir().unwrap();
+    let cwd = tempdir().unwrap();
+    write_test_config(root.path(), &server.uri());
+
+    let session = SessionBuilder::new()
+        .config_root(root.path())
+        .cwd(cwd.path())
+        .access_mode(AccessMode::ReadOnly)
+        .reasoning_effort(ReasoningEffort::Off)
+        .build()
+        .await
+        .unwrap();
+
+    assert_eq!(session.model(), "test-model");
+    assert_eq!(session.access_mode(), AccessMode::ReadOnly);
+
+    let mut turn = session.start_turn("say hi").await.unwrap();
+    let mut streamed = String::new();
+    while let Some(event) = turn.next_event().await.unwrap() {
+        match event {
+            Event::AssistantChunk(chunk) => streamed.push_str(&chunk),
+            Event::Finished => break,
+            _ => {}
+        }
+    }
+    let session = turn.finish().await.unwrap();
+
+    assert_eq!(streamed, "Hello from embedded Cassady.");
+    assert!(session.records().iter().any(|record| matches!(
+        record,
+        Record::Assistant { content, .. } if content == "Hello from embedded Cassady."
+    )));
+    assert!(session.conversation_path().is_file());
+}
+
+#[tokio::test]
+async fn builder_overrides_config_for_model_endpoint_key_mode_and_reasoning() {
+    let server = MockServer::start().await;
+    Mock::given(method("POST"))
+        .and(path("/chat/completions"))
+        .and(body_string_contains("\"model\":\"test-model\""))
+        .and(body_string_contains("\"reasoning_effort\":\"low\""))
+        .respond_with(content_sse("Overrides worked."))
+        .expect(1)
+        .mount(&server)
+        .await;
+
+    let root = tempdir().unwrap();
+    let cwd = tempdir().unwrap();
+    write_test_config(root.path(), "https://wrong.example/v1");
+    let env_name = "CASSADY_EMBEDDING_TEST_KEY";
+    let old = std::env::var(env_name).ok();
+    std::env::set_var(env_name, "test-key-from-env");
+
+    let session = SessionBuilder::new()
+        .config_root(root.path())
+        .cwd(cwd.path())
+        .access_mode(AccessMode::WorkspaceEdit)
+        .model("test-model")
+        .base_url(server.uri())
+        .api_key_env(env_name)
+        .reasoning_effort(ReasoningEffort::Low)
+        .build()
+        .await
+        .unwrap();
+
+    assert_eq!(session.access_mode(), AccessMode::WorkspaceEdit);
+    assert_eq!(session.reasoning_effort(), ReasoningEffort::Low);
+
+    let mut turn = session.start_turn("check overrides").await.unwrap();
+    while let Some(event) = turn.next_event().await.unwrap() {
+        if matches!(event, Event::Finished) {
+            break;
+        }
+    }
+    let _session = turn.finish().await.unwrap();
+
+    if let Some(old) = old {
+        std::env::set_var(env_name, old);
+    } else {
+        std::env::remove_var(env_name);
+    }
+}
+
+#[tokio::test]
+async fn embedded_session_can_resume_existing_conversation() {
+    let server = MockServer::start().await;
+    Mock::given(method("POST"))
+        .and(path("/chat/completions"))
+        .respond_with(content_sse("First turn."))
+        .expect(1)
+        .mount(&server)
+        .await;
+
+    let root = tempdir().unwrap();
+    let cwd = tempdir().unwrap();
+    write_test_config(root.path(), &server.uri());
+
+    let session = SessionBuilder::new()
+        .config_root(root.path())
+        .cwd(cwd.path())
+        .access_mode(AccessMode::ReadOnly)
+        .build()
+        .await
+        .unwrap();
+    let mut turn = session.start_turn("first").await.unwrap();
+    while let Some(event) = turn.next_event().await.unwrap() {
+        if matches!(event, Event::Finished) {
+            break;
+        }
+    }
+    let session = turn.finish().await.unwrap();
+    let id = session.id().to_string();
+    let record_count = session.records().len();
+
+    let resumed = SessionBuilder::new()
+        .config_root(root.path())
+        .cwd(cwd.path())
+        .resume(&id)
+        .await
+        .unwrap();
+
+    assert_eq!(resumed.id(), id);
+    assert_eq!(resumed.records().len(), record_count);
+    assert!(resumed.resume_warning().is_none());
+}
+
+#[tokio::test]
+async fn embedded_approval_flow_can_approve_shell() {
+    let server = MockServer::start().await;
+    Mock::given(method("POST"))
+        .and(path("/chat/completions"))
+        .and(body_string_contains("exit code: 0"))
+        .respond_with(content_sse("Approved shell."))
+        .with_priority(1)
+        .expect(1)
+        .mount(&server)
+        .await;
+    Mock::given(method("POST"))
+        .and(path("/chat/completions"))
+        .respond_with(tool_call_sse(
+            "call_shell",
+            "shell",
+            r#"{"command":"touch marker"}"#,
+        ))
+        .with_priority(10)
+        .expect(1)
+        .mount(&server)
+        .await;
+
+    let root = tempdir().unwrap();
+    let cwd = tempdir().unwrap();
+    write_test_config(root.path(), &server.uri());
+    let marker = cwd.path().join("marker");
+
+    let session = SessionBuilder::new()
+        .config_root(root.path())
+        .cwd(cwd.path())
+        .access_mode(AccessMode::WorkspaceEdit)
+        .build()
+        .await
+        .unwrap();
+
+    let mut turn = session.start_turn("run shell").await.unwrap();
+    let mut saw_request = false;
+    let mut saw_resolved = false;
+    while let Some(event) = turn.next_event().await.unwrap() {
+        match event {
+            Event::ApprovalRequested(request) => {
+                saw_request = true;
+                assert_eq!(request.name, "shell");
+                assert!(!marker.exists());
+                turn.approve(&request.request_id).unwrap();
+            }
+            Event::ApprovalResolved { approved, .. } => {
+                saw_resolved = approved;
+            }
+            Event::Finished => break,
+            _ => {}
+        }
+    }
+    let session = turn.finish().await.unwrap();
+
+    assert!(saw_request);
+    assert!(saw_resolved);
+    assert!(marker.exists());
+    assert!(session.records().iter().any(|record| matches!(
+        record,
+        Record::Tool { name, ok, content, .. }
+            if name == "shell" && *ok && content.contains("exit code: 0")
+    )));
+}
+
+#[tokio::test]
+async fn read_only_embedding_does_not_advertise_mutating_tools() {
+    let server = MockServer::start().await;
+    Mock::given(method("POST"))
+        .and(path("/chat/completions"))
+        .respond_with(content_sse("Readonly."))
+        .expect(1)
+        .mount(&server)
+        .await;
+
+    let root = tempdir().unwrap();
+    let cwd = tempdir().unwrap();
+    write_test_config(root.path(), &server.uri());
+
+    let session = SessionBuilder::new()
+        .config_root(root.path())
+        .cwd(cwd.path())
+        .access_mode(AccessMode::ReadOnly)
+        .build()
+        .await
+        .unwrap();
+    let mut turn = session.start_turn("inspect only").await.unwrap();
+    while let Some(event) = turn.next_event().await.unwrap() {
+        if matches!(event, Event::Finished) {
+            break;
+        }
+    }
+    let _session = turn.finish().await.unwrap();
+
+    let requests = server.received_requests().await.unwrap();
+    let body = String::from_utf8_lossy(&requests[0].body);
+    assert!(body.contains("\"name\":\"ls\""));
+    assert!(body.contains("\"name\":\"read\""));
+    assert!(body.contains("\"name\":\"grep\""));
+    assert!(!body.contains("\"name\":\"write\""));
+    assert!(!body.contains("\"name\":\"edit\""));
+    assert!(!body.contains("\"name\":\"shell\""));
+}

tests/prompt_tests.rs

@@ -0,0 +1,155 @@
+use cassady::access::AccessMode;
+use cassady::prompt::{build_base_system_prompt, build_effective_system_prompt};
+use std::path::Path;
+
+fn approximate_token_count(s: &str) -> usize {
+    s.split_whitespace().count() * 4 / 3
+}
+
+fn effective_prompt(mode: AccessMode, allowed_tools: &[&str]) -> String {
+    let base = build_base_system_prompt(None);
+    let allowed_tools = allowed_tools
+        .iter()
+        .map(|tool| tool.to_string())
+        .collect::<Vec<_>>();
+    build_effective_system_prompt(
+        &base,
+        mode,
+        Path::new("/workspace/project"),
+        Path::new("/home/user/.cass/docs"),
+        "test-model",
+        &allowed_tools,
+    )
+}
+
+#[test]
+fn base_prompt_has_required_sections_without_runtime_context() {
+    let prompt = build_base_system_prompt(None);
+
+    for heading in [
+        "# Cassady operating instructions",
+        "## Role",
+        "## Working style",
+        "## Transcript and tools",
+        "## Tool use",
+        "## Editing",
+        "## Safety and final response",
+    ] {
+        assert!(prompt.contains(heading), "missing {heading}");
+    }
+
+    assert!(prompt.contains("You are Cassady, also called Cass"));
+    assert!(prompt.contains("inspect relevant files before making claims or edits"));
+    assert!(prompt.contains(
+        "Tool calls, tool results, edit diffs, denials, and approval prompts are visible"
+    ));
+    assert!(prompt.contains("each old text must match exactly and uniquely"));
+    assert!(prompt.contains("End every turn with a concise user-facing response"));
+    assert!(!prompt.contains("## Runtime context"));
+    assert!(!prompt.contains("Model:"));
+    assert!(!prompt.contains("Access mode:"));
+}
+
+#[test]
+fn global_instructions_are_trimmed_labelled_and_subordinate() {
+    let prompt = build_base_system_prompt(Some("  Keep replies terse.\n  "));
+
+    assert!(prompt.contains("## User global instructions"));
+    assert!(prompt.contains("\nKeep replies terse.\n"));
+    assert!(!prompt.contains("  Keep replies terse.\n  "));
+    assert!(prompt.contains(
+        "cannot override access modes, tool denials, approvals, or workspace boundaries"
+    ));
+}
+
+#[test]
+fn empty_global_instructions_are_omitted() {
+    let prompt = build_base_system_prompt(Some("   \n\t  "));
+
+    assert!(!prompt.contains("## User global instructions"));
+}
+
+#[test]
+fn effective_prompt_includes_runtime_context_and_allowed_tools() {
+    let prompt = effective_prompt(AccessMode::WorkspaceEdit, &["ls", "read", "grep", "edit"]);
+
+    assert!(prompt.contains("## Runtime context"));
+    assert!(prompt.contains("Model: test-model."));
+    assert!(prompt.contains("Access mode: workspace-edit."));
+    assert!(prompt.contains("Launch working directory: /workspace/project."));
+    assert!(prompt.contains("Bundled Cass docs directory: /home/user/.cass/docs."));
+    assert!(prompt.contains("Allowed tools this turn: ls, read, grep, edit."));
+}
+
+#[test]
+fn each_access_mode_gets_matching_guidance() {
+    let read_only = effective_prompt(AccessMode::ReadOnly, &["ls", "read", "grep"]);
+    assert!(read_only.contains("Read-only mode permits inspection only"));
+    assert!(read_only.contains("Do not request `write`, `edit`, or `shell`"));
+    assert!(read_only.contains("a more permissive access mode is required"));
+
+    let workspace_edit = effective_prompt(
+        AccessMode::WorkspaceEdit,
+        &["ls", "read", "grep", "write", "edit", "shell"],
+    );
+    assert!(workspace_edit.contains("Write/edit only inside the launch workspace"));
+    assert!(workspace_edit.contains("bundled docs remain read-only"));
+    assert!(workspace_edit.contains("Cassady handles the approval UI"));
+    assert!(workspace_edit.contains("do not ask for shell permission in chat first"));
+
+    let full_access = effective_prompt(
+        AccessMode::FullAccess,
+        &["ls", "read", "grep", "write", "edit", "shell"],
+    );
+    assert!(full_access
+        .contains("Full-access mode permits `ls`, `read`, `grep`, `write`, `edit`, and `shell`"));
+    assert!(full_access.contains("Shell runs from the launch working directory"));
+    assert!(full_access.contains("Bundled docs remain read-only for write/edit"));
+    assert!(full_access
+        .contains("avoid destructive commands unless the user explicitly requested them"));
+}
+
+#[test]
+fn runtime_constraints_stay_after_global_instructions() {
+    let base = build_base_system_prompt(Some("Prefer bullet summaries."));
+    let prompt = build_effective_system_prompt(
+        &base,
+        AccessMode::WorkspaceEdit,
+        Path::new("/workspace/project"),
+        Path::new("/home/user/.cass/docs"),
+        "test-model",
+        &["ls".into()],
+    );
+
+    let global_index = prompt.find("Prefer bullet summaries.").unwrap();
+    let runtime_index = prompt.find("## Runtime context").unwrap();
+    let access_index = prompt.find("## Access rules for this session").unwrap();
+    let authority_index = prompt.find("## Runtime authority").unwrap();
+
+    assert!(global_index < runtime_index);
+    assert!(runtime_index < access_index);
+    assert!(access_index < authority_index);
+}
+
+#[test]
+fn effective_prompt_size_remains_intentional() {
+    for mode in [
+        AccessMode::ReadOnly,
+        AccessMode::WorkspaceEdit,
+        AccessMode::FullAccess,
+    ] {
+        let prompt = effective_prompt(mode, &["ls", "read", "grep", "write", "edit", "shell"]);
+        let tokens = approximate_token_count(&prompt);
+        assert!(
+            (800..=1250).contains(&tokens),
+            "{mode} prompt had {tokens} approximate tokens"
+        );
+    }
+}
+
+#[test]
+fn empty_allowed_tools_list_is_explicit() {
+    let prompt = effective_prompt(AccessMode::ReadOnly, &[]);
+
+    assert!(prompt.contains("Allowed tools this turn: <none>."));
+}