## Codebase Patterns
- This is a Rust project using Cargo for dependency management
- Binary crate structure: Cargo.toml with [[bin]] target, src/main.rs as entry point
- License: MIT with author 'jellydn' and year 2026
- Pattern for testable env-dependent functions: create a `*_with_env` helper that takes `HashMap<String, String>` for injection
- The `which` crate is already available for PATH probing (version 6.0)
- Fallback shell pattern: print warning to stderr, then exec user's shell (Unix: $SHELL or /bin/sh, Windows: %COMSPEC% or cmd.exe)

## 2026-05-01 12:40 - US-001
- What was implemented: Scaffolded the Rust binary crate with Cargo.toml, src/main.rs, .gitignore, and LICENSE
- Files changed: Cargo.toml, src/main.rs, .gitignore, LICENSE
- **Learnings for future iterations:**
  - Project root is at /Users/huynhdung/src/tries/2026-05-01-zed-codemux, not scripts/ralph
  - Use workdir parameter in bash tool to run commands from correct directory
  - Dependencies needed: clap (derive feature), which, serde + serde_derive, toml, anyhow, dirs, regex
  - Must use PREK_ALLOW_NO_CONFIG=1 for git commits due to pre-commit hook
---

## 2026-05-01 12:50 - US-002
- What was implemented: Added session name sanitization module (src/sanitize.rs) that exactly matches vscode-mux algorithm
- Files changed: src/sanitize.rs (new), src/main.rs (mod declaration)
- **Learnings for future iterations:**
  - Use `#[allow(dead_code)]` temporarily when functions are not yet used in main (clippy -D warnings requires this)
  - Regex patterns needed for sanitization: `[^a-zA-Z0-9-]` for invalid chars, `\-{2,}` to collapse consecutive dashes, `^-+` and `-+$` for trimming
  - All vscode-mux test fixtures pass: 'My Workspace' → 'My-Workspace', 'my.project' → 'my-project', etc.
  - The algorithm: replace invalid chars with '-', collapse consecutive '-', strip leading/trailing '-', return 'session' if empty
---

## 2026-05-01 13:05 - US-003
- What was implemented: Added POSIX shell-escape module (src/shell_escape.rs) with `shell_escape` function
- Files changed: src/shell_escape.rs (new), src/main.rs (mod declaration)
- **Learnings for future iterations:**
  - POSIX single-quote escaping: wrap in `'...'` and replace internal `'` with `'"'"'`
  - Pattern for unused functions: add `#[allow(dead_code)]` to satisfy clippy -D warnings
  - Test coverage: empty string, simple strings, strings with single quotes, paths with spaces
---

## 2026-05-01 14:15 - US-004
- What was implemented: Added TOML config-file loader (src/config.rs) with `Config` struct and `load_config()` function
- Files changed: src/config.rs (new), src/main.rs (mod declaration)
- **Learnings for future iterations:**
  - Use `dirs` crate for cross-platform config dir resolution (Windows: %APPDATA%, macOS/Linux: ~/.config)
  - Support $XDG_CONFIG_HOME environment variable as first priority
  - Pattern: `parse_config_str()` helper for testable TOML parsing without filesystem
  - Use `toml::from_str().unwrap_or_default()` for graceful fallback on invalid config
  - Serde derive macros work great for simple config structs with optional fields
---

## 2026-05-01 14:35 - US-005
- What was implemented: Added multiplexer detection module (src/detect.rs) with `Multiplexer` enum and `detect_multiplexer()` function
- Files changed: src/detect.rs (new), src/main.rs (mod declaration), prd.json (US-005 passes: true)
- **Learnings for future iterations:**
  - Resolution priority: 1) CODEMUX_MULTIPLEXER env var, 2) config.multiplexer field, 3) PATH probe (tmux first, then zellij)
  - Pattern for testable env-dependent functions: create a `*_with_env` helper that takes `HashMap<String, String>` for injection
  - The `which` crate (already in deps) works great for PATH probing
  - Use `#[allow(dead_code)]` on functions not yet used in main to satisfy clippy -D warnings
  - Case-insensitive parsing for multiplexer names (TMUX, tmux, Tmux all work)
---

## 2026-05-01 15:10 - US-006
- What was implemented: Added multiplexer launcher trait (src/launcher.rs) and tmux implementation (src/tmux.rs)
- Files changed: src/launcher.rs (new), src/tmux.rs (new), src/main.rs (mod declarations)
- **Learnings for future iterations:**
  - Trait definition pattern: use `anyhow::Result` for flexible error handling in trait methods
  - The `build_command` method returns a String (shell command) not a Command struct - this allows the caller to control execution
  - For `list_sessions`, return empty Vec on non-zero exit (tmux server not running) rather than error
  - Always use shell_escape on name and cwd before interpolating into command strings
  - Pattern for modules with unused functions: add `#[allow(dead_code)]` to struct, impl, and trait
  - Tmux commands: `tmux new-session -A -s <name>` attaches to existing or creates new; `-c <cwd>` sets working directory
---

## 2026-05-01 16:00 - US-007
- What was implemented: Added zellij launcher implementation (src/zellij.rs) following the same pattern as tmux.rs
- Files changed: src/zellij.rs (new), src/main.rs (added mod zellij), scripts/ralph/prd.json (updated US-007 passes: true)
- **Learnings for future iterations:**
  - Zellij differs from tmux: NO -c option for cwd in either auto-attach or new session mode (per vscode-mux behavior)
  - Zellij auto-attach command: `zellij attach <name> -c` (the -c creates session if not exists)
  - Zellij new session command: `zellij -s <name>` (simple session creation)
  - `zellij list-sessions -n` outputs just session names (similar to tmux format)
  - Both zellij and tmux follow the same error handling pattern: return empty Vec on non-zero exit
  - Copying the tmux.rs structure and adapting the command strings is the fastest approach
---

## 2026-05-01 16:45 - US-008
- What was implemented: Added `get_unique_session_name()` function to src/sanitize.rs with gap-filling algorithm
- Files changed: src/sanitize.rs (added function + tests), scripts/ralph/prd.json (updated US-008 passes: true)
- **Learnings for future iterations:**
  - Gap-filling algorithm: start suffix at 2, increment until finding a name not in the sessions list
  - Uses `std::collections::HashSet<&str>` for O(1) lookup performance
  - The algorithm fills gaps: ['myapp','myapp-2','myapp-5'] → returns 'myapp-3' (not 'myapp-6')
  - This matches vscode-mux behavior exactly for multi-window scenarios
  - Added 6 comprehensive tests covering empty list, base not in list, base exists, gap-filling scenarios
---

## 2026-05-01 17:35 - US-009
- What was implemented: Wired main entry point to detect multiplexer, compute session name, and exec into multiplexer command
- Files changed: src/main.rs (complete rewrite - 332 insertions), scripts/ralph/prd.json (updated US-009 passes: true)
- **Learnings for future iterations:**
  - Main entry point structure: get CWD → sanitize basename → load config → detect multiplexer → resolve auto_attach → get session name → build command → exec
  - Auto-attach resolution priority: env `CODEMUX_AUTO_ATTACH` → config.auto_attach → default `true`
  - Session name selection logic: if auto_attach and base exists in sessions → use base; otherwise use `get_unique_session_name`
  - Unix exec pattern: use `std::os::unix::process::CommandExt::exec()` to replace process with shell command
  - Windows spawn pattern: use `Command::status()` then `std::process::exit()` to propagate exit code
  - Shell command structure: `$SHELL -l -c "tmux new-session -A -s 'name' -c '/path'"`
  - Fallback shell when no multiplexer: print warning to stderr, then exec user's shell directly
  - Cross-platform conditional compilation: `#[cfg(unix)]`, `#[cfg(windows)]`, `#[cfg(not(any(unix, windows)))]`
  - 14 new unit tests for resolve_auto_attach, get_base_name, decide_fallback_shell
  - All 66 tests pass (including 14 new main module tests)
---


## 2026-05-01 18:00 - US-010
- What was implemented: Verified US-010 (Graceful fallback when no multiplexer) was already complete
- Files changed: scripts/ralph/prd.json (marked US-010 passes: true)
- **Learnings for future iterations:**
  - The fallback shell implementation was already in place from US-009 work
  - Warning message format: `codemux: tmux/zellij not found on PATH -- falling back to {shell}. Install tmux or zellij to enable multiplexer mode.`
  - `decide_fallback_shell()` uses `#[cfg(unix)]` and `#[cfg(windows)]` for cross-platform shell selection
  - Pattern: When testing env-dependent functions, use a helper that takes `HashMap<String, String>` for injection
  - All 66 tests pass including 4 tests for `decide_fallback_shell` covering Unix/Windows env and default cases
---

## 2026-05-01 18:35 - US-011
- What was implemented: Added CLI flags (--version, --help) and CODEMUX_DEBUG logging
- Files changed: src/main.rs (Cli struct with clap derive, debug_enabled function, debug logging throughout, 5 new unit tests)
- **Learnings for future iterations:**
  - Clap derive API pattern: `#[derive(Parser)]` with `#[command(name, about, version)]` attributes
  - For trailing args support: `#[command(trailing_var_arg = true, allow_hyphen_values = true)]`
  - Debug logging pattern: prefix each line with `[codemux] ` and output to stderr via `eprintln!`
  - Debug logging includes: multiplexer, base name, sanitized name, auto_attach, final session name, full command
  - `debug_enabled()` helper uses exact match on "1" (not "true", not case-insensitive)
  - 5 unit tests for debug_enabled: set to 1, unset, set to 0, set to other value, set to empty
  - All 71 tests pass (66 original + 5 new)
  - `--version` outputs: `codemux 0.1.0`
  - `--help` shows description, usage, and options
---

## 2026-05-01 19:10 - US-012
- What was implemented: Added GitHub Actions CI workflow (`.github/workflows/ci.yml`) with build matrix for ubuntu-latest, macos-latest, and windows-latest
- Files changed: `.github/workflows/ci.yml` (new)
- **Learnings for future iterations:**
  - Use `actions/checkout@v4` for checkout, `dtolnay/rust-toolchain@stable` for Rust setup
  - Include `components: clippy, rustfmt` in the toolchain setup for linting and formatting checks
  - Use `Swatinem/rust-cache@v2` for caching cargo registry and target dir across runs
  - Set `cache-on-failure: true` to cache even when builds fail
  - CI workflow triggers on push to main and pull_request to main
  - All quality checks verified locally before committing
  - 71 tests pass, clippy clean, formatting correct
---

## 2026-05-01 20:25 - US-013
- What was implemented: Added GitHub Actions release workflow (`.github/workflows/release.yml`) producing cross-platform binaries
- Files changed: `.github/workflows/release.yml` (new)
- **Learnings for future iterations:**
  - Release workflow triggered on tag push matching `v*` pattern
  - Build matrix includes 5 targets: macos-x64, macos-arm64, linux-x64, linux-arm64, windows-x64
  - Artifact naming: `codemux-{version}-macos-{arch}.tar.gz`, `codemux-{version}-linux-{arch}.tar.gz`, `codemux-{version}-windows-x64.zip`
  - Cross-compilation for Linux ARM64 requires `gcc-aarch64-linux-gnu` package and `CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER` env var
  - Uses `softprops/action-gh-release@v2` to create GitHub Release and attach all artifacts
- Uses `actions/upload-artifact@v4` and `actions/download-artifact@v4` for artifact passing between jobs
- Two-stage workflow: build-and-release job (matrix) → create-release job (collects artifacts)
- YAML linting: yamllint passes (only truthy warning on `on:` which is standard for GitHub Actions)
- All 71 tests pass, clippy clean, formatting correct, build succeeds
## 2026-05-01 21:05 - US-015
- What was implemented: Polished README with all required sections and added demo GIF placeholder
- Files changed: README.md (updated), assets/demo.gif (new), scripts/ralph/prd.json (US-015 passes: true)
- **Learnings for future iterations:**
  - Added "Compared to vscode-mux" link block at the top of README (shields.io badge linking to vscode-mux)
  - Added "Differences from vscode-mux" subsection with feature comparison table (vscode-mux vs CodeMux columns)
  - Table enumerates: CLI binary approach (no Zed terminal API), no kill subcommand in v1, no per-workspace config in v1
  - Created 1x1 transparent GIF placeholder (43 bytes) using binary printf to assets/demo.gif
  - Referenced demo.gif from the "Why CodeMux for Zed?" section with markdown: `![Demo](assets/demo.gif)`
  - All 71 tests pass, clippy clean, formatting correct
---

## 2026-05-01 21:00 - US-014
- What was implemented: Added Zed companion extension manifest and submission guide
- Files changed: extension.toml (new), tasks/zed-extension-submission.md (new)
- **Learnings for future iterations:**
  - Zed extension manifest format (extension.toml): id, name, version, schema_version=1, authors[], description, repository
  - Do NOT bundle the binary in the extension per Zed policy — extension is for discoverability only
  - README already had the "Install the binary alongside the extension" section
  - LICENSE was already present (MIT) from US-001, verified it's correct for Zed
  - Submission guide should include: fork → create entry → update extensions.toml → PR → wait for review
  - 71 tests pass, clippy clean, formatting correct
---

## 2026-05-02 09:20 - US-012
- What was implemented: Added Zed integration files (.zed/tasks.json and docs/zed-integration.md) following the fff-gpui pattern
- Files changed: `.zed/tasks.json` (new), `docs/zed-integration.md` (new), `scripts/ralph/prd.json` (US-012 marked complete)
- **Learnings for future iterations:**
  - `.zed/tasks.json` is a project-local convenience task (build and run codemux) — mirrors fff-gpui's pattern
  - `docs/zed-integration.md` documents both Option A (settings.json) and Option B (tasks.json + keymap.json)
  - fff-gpui pattern: pure binary + Zed configuration files (no bundled extension)
  - Use `python3 -m json.tool` to validate JSON snippets in documentation
  - All JSON in docs must be syntactically valid for user copy-paste safety
  - 71 tests pass, clippy clean, formatting correct, JSON validation passes
---

## 2026-05-02 13:35 - US-001
- What was implemented: Updated PRD to mark US-001 as complete (passes: true). Verified all acceptance criteria are met: Cargo.toml with [[bin]] target, all required dependencies present, src/main.rs exists, .gitignore covers /target and .DS_Store, LICENSE is MIT with 2026 copyright and author 'jellydn'. All 71 tests pass, clippy clean, formatting correct.
- Files changed: scripts/ralph/prd.json
- **Learnings for future iterations:**
  - The PRD must be updated after completing each story to mark `passes: true`
  - This session focused on PRD synchronization rather than new implementation
  - All quality gates (fmt, clippy, test) run via pre-commit hook automatically
---

## 2026-05-02 14:15 - PRD Synchronization (US-002 through US-014)
- Session: Syncing PRD state with actual implementation status
- What was implemented: Updated prd.json to mark all completed stories as passes: true. All stories from US-002 through US-014 are now correctly marked complete. The code was already fully implemented (71 tests passing, all modules present), only the PRD tracking needed synchronization.
- Files changed: scripts/ralph/prd.json
- **Learnings for future iterations:**
  - PRD state can drift from actual implementation - periodically verify passes flags match reality
  - All 71 tests pass, clippy clean, formatting correct
  - Full implementation complete: sanitize, shell_escape, config, detect, launcher, tmux, zellij, unique_name modules
  - CI workflows (.github/workflows/ci.yml, .github/workflows/release.yml) exist and are configured
  - README.md is comprehensive with all required sections
  - All acceptance criteria met across all 14 stories
---


## 2026-05-02 14:30 - US-015
- What was implemented: Cleanup deferred v1.1 artifacts per the fff-gpui pattern (pure binary, no extension manifest, source build only in v1)
- Files changed: deleted extension.toml, deleted tasks/zed-extension-submission.md, deleted .github/workflows/release.yml, updated AGENTS.md (removed Zed Extension section, updated CI section, deduplicated Task runner block, noted get_unique_session_name location)
- **Learnings for future iterations:**
  - The fff-gpui pattern: pure Rust binary, no Zed extension manifest, integration purely via Zed user config (settings.json or tasks.json)
  - Release workflow deferred to v1.1 - for v1, source build only via `cargo build --release`
  - AGENTS.md should reflect the lean design philosophy throughout
  - All 71 tests still pass after deletions, clippy clean, formatting correct
---


## 2026-05-02 14:35 - US-016
- What was implemented: Removed redundant serde_derive dependency from Cargo.toml
- Files changed: Cargo.toml (removed line 21: serde_derive = "1.0")
- **Learnings for future iterations:**
  - The serde crate's "derive" feature already pulls in serde_derive transitively
  - Keep dependency graph minimal by avoiding redundant declarations
  - Cargo.lock updated automatically via cargo build
  - All 71 tests pass after cleanup, clippy clean, formatting correct
  - knownIssues array is now empty - all cleanup complete!
---

