127 lines
2.7 KiB
Markdown
127 lines
2.7 KiB
Markdown
# Hook Input/Output Schemas
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This documents the JSON payloads each Claude Code hook receives on stdin for every event type.
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## PreToolUse
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Fired before a tool is executed. Can **allow** (exit 0) or **block** (exit 2).
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### PreToolUse: Bash
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```json
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{
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"tool_name": "Bash",
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"tool_input": {
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"command": "git commit -m 'feat: add player health system'",
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"description": "Commit changes with message",
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"timeout": 120000
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}
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}
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```
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### PreToolUse: Write
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```json
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{
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"tool_name": "Write",
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"tool_input": {
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"file_path": "src/gameplay/health.gd",
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"content": "extends Node\n..."
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}
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}
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```
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### PreToolUse: Edit
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```json
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{
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"tool_name": "Edit",
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"tool_input": {
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"file_path": "src/gameplay/health.gd",
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"old_string": "var health = 100",
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"new_string": "var health: int = 100"
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}
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}
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```
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### PreToolUse: Read
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```json
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{
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"tool_name": "Read",
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"tool_input": {
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"file_path": "src/gameplay/health.gd"
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}
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}
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```
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## PostToolUse
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Fired after a tool completes. **Cannot block** (exit code ignored for blocking). Stderr messages are shown as warnings.
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### PostToolUse: Write
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```json
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{
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"tool_name": "Write",
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"tool_input": {
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"file_path": "assets/data/enemy_stats.json",
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"content": "{\"goblin\": {\"health\": 50}}"
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},
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"tool_output": "File written successfully"
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}
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```
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### PostToolUse: Edit
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```json
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{
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"tool_name": "Edit",
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"tool_input": {
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"file_path": "assets/data/enemy_stats.json",
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"old_string": "\"health\": 50",
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"new_string": "\"health\": 75"
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},
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"tool_output": "File edited successfully"
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}
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```
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## SubagentStart
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Fired when a subagent is spawned via the Task tool.
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```json
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{
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"agent_name": "game-designer",
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"model": "sonnet",
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"description": "Design the combat healing mechanic"
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}
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```
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## SessionStart
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Fired when a Claude Code session begins. **No stdin input** — the hook just runs and its stdout is shown to Claude as context.
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## PreCompact
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Fired before context window compression. **No stdin input** — the hook runs to save state before compression occurs.
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## Stop
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Fired when the Claude Code session ends. **No stdin input** — the hook runs for cleanup and logging.
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## Exit Code Reference
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| Exit Code | Meaning | Applicable Events |
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|-----------|---------|-------------------|
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| 0 | Allow / Success | All events |
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| 2 | Block (stderr shown to Claude) | PreToolUse only |
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| Other | Treated as error, tool proceeds | All events |
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## Notes
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- Hooks receive JSON on **stdin** (pipe). Use `INPUT=$(cat)` to capture.
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- Parse with `jq` if available, fall back to `grep` for cross-platform compatibility.
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- On Windows, `grep -P` (Perl regex) is often unavailable. Use `grep -E` (POSIX extended) instead.
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- Path separators may be `\` on Windows. Normalize with `sed 's|\\|/|g'` when comparing paths.
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