claude-foundations/HOOKS.md

# Hooks

Claude Code hooks that run automatically in response to events. Source of truth lives here; symlinks point from `~/.claude/hooks/` back to this directory.

## Available Hooks

| Hook | Event | File |
|------|-------|------|
| Pre-compact backup | PreCompact (auto + manual) | `hooks/pre-compact-backup.sh` |
| Post-edit lint | PostToolUse (Edit/Write/MultiEdit) | `hooks/post-edit-lint.sh` |
| Pre-commit lint | Git pre-commit | `hooks/pre-commit-lint.sh` |
| WezTerm profile theme | SessionStart (per-profile) | `hooks/set-wezterm-profile.sh` |

## Post-edit Lint

Formats and lints files after every Edit/Write/MultiEdit. Dispatches to project-local `formatters/` directory (symlinks to `claude-foundations/formatters/`).

**Flow:**
1. Extracts `file_path` and `cwd` from stdin JSON
2. Walks up from `cwd` to find `formatters/` directory
3. Creates a `git hash-object` checkpoint (`.pre-lint` file with blob SHA)
4. Runs the matching formatter script
5. On clean pass: removes checkpoint, exits 0 (silent)
6. On lint errors: keeps checkpoint, exits 2 (feeds errors back to Claude via stderr)

**Requires:** `python3` (for JSON parsing from stdin). Formatter tools are optional — missing tools silently pass.

**Revert:** `git cat-file blob $(cat <file>.pre-lint) > <file>`

## Pre-commit Lint

Git pre-commit hook that runs project formatters on staged files. Reuses the same formatter scripts.

**Flow:** iterates staged files → runs matching formatter → re-stages formatted files → exits non-zero if lint errors remain (blocks commit).

**Install:** symlink `.git/hooks/pre-commit` → `pre-commit-lint.sh`, or use `scripts/setup-formatters.sh`.

## Pre-compact Backup

Saves a copy of the session transcript before context compaction so no conversation history is lost. Backs up to `~/.claude/transcript-backups/` with timestamped filenames. Auto-prunes backups older than 30 days.

**Triggers:** Both auto-compaction (context window full) and manual (`/compact` command).

**Requires:** `python3` (for JSON parsing from stdin).

## Installation

The easiest way is to run the install script:

```bash
cd ~/dev/claude/projects/claude-foundations
scripts/install-hooks.sh
```

This symlinks all hooks into `~/.claude/hooks/` and prints the `settings.json` config to add.

### Manual installation

1. Symlink each hook into `~/.claude/hooks/`:
   ```bash
   mkdir -p ~/.claude/hooks
   ln -sf "$(pwd)/hooks/pre-compact-backup.sh" ~/.claude/hooks/pre-compact-backup.sh
   ln -sf "$(pwd)/hooks/post-edit-lint.sh" ~/.claude/hooks/post-edit-lint.sh
   ln -sf "$(pwd)/hooks/pre-commit-lint.sh" ~/.claude/hooks/pre-commit-lint.sh
   ```

2. Add the hook configuration to `~/.claude/settings.json`:
   ```json
   {
     "hooks": {
       "PreCompact": [
         {
           "matcher": "auto",
           "hooks": [{ "type": "command", "command": "~/.claude/hooks/pre-compact-backup.sh", "timeout": 15, "statusMessage": "Backing up transcript before compaction..." }]
         },
         {
           "matcher": "manual",
           "hooks": [{ "type": "command", "command": "~/.claude/hooks/pre-compact-backup.sh", "timeout": 15, "statusMessage": "Backing up transcript before compaction..." }]
         }
       ],
       "PostToolUse": [
         {
           "matcher": "Edit|Write|MultiEdit",
           "hooks": [{ "type": "command", "command": "~/.claude/hooks/post-edit-lint.sh", "timeout": 30, "statusMessage": "Formatting and linting..." }]
         }
       ]
     }
   }
   ```

3. For per-project formatters, run:
   ```bash
   scripts/setup-formatters.sh <project-dir> <ext> [<ext> ...]
   ```

## WezTerm Profile Theme

Sets the WezTerm terminal theme when a Claude session starts or resumes, by emitting an OSC 1337 `SetUserVar` escape sequence. WezTerm fires its `user-var-changed` Lua event and applies the matching color scheme and background image from `wezterm.lua`.

**Derives profile name** from `CLAUDE_CONFIG_DIR` (e.g. `~/.claude-octopus` → `octopus`). No-ops for the default profile.

**Writes to `/dev/tty`** to reach WezTerm directly, bypassing Claude Code's stdout capture. Safe in non-WezTerm terminals — the sequence is silently ignored.

**Configure per profile** in `~/.claude-<name>/settings.json`:
```json
"SessionStart": [
  { "hooks": [{ "type": "command", "command": "~/.claude/hooks/set-wezterm-profile.sh" }] }
]
```

## Adding New Hooks

1. Create the script in `hooks/`
2. Add an entry to this file
3. Symlink into `~/.claude/hooks/`
4. Add the matcher config to `~/.claude/settings.json`