Hooks reference changedhooks
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14321432An [Agent SDK callback hook](/docs/en/agent-sdk/hooks) on `UserPromptSubmit` that reaches its timeout blocks the prompt with a message naming the hook and the timeout, because a callback there can be acting as a policy gate that must not fail open. The session continues. Before v2.1.208, a callback timeout on that event ended the turn with an execution error.
14331433
1434If you press `Esc` in the terminal while `UserPromptSubmit` hooks are still checking a prompt, the text you typed goes back into the prompt box.
1435
14341436#### UserPromptSubmit input
14351437
14361438In addition to the [common input fields](#common-input-fields), UserPromptSubmit hooks receive the `prompt` field containing the submitted text. Pasted content that collapsed to a `[Pasted text #N]` placeholder arrives expanded in place. In sessions where Claude Code [marks pasted text for Claude](/docs/en/terminal-config#how-claude-treats-pasted-text), that expanded content sits between a `<pasted_content id="…">` line and a `</pasted_content id="…">` line, so account for those lines if your hook parses the prompt.
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32203222| Matcher | When it fires |
32213223| :- | :- |
32223224| `manual` | `/compact` |
3223| `auto` | Auto-compact when the conversation reaches the [auto-compact window](/docs/en/model-config#set-the-auto-compact-window) |
3225| `auto` | Auto-compact when the conversation reaches the [auto-compact window](/docs/en/model-config#set-the-auto-compact-window), and [idle compaction](/docs/en/settings-reference#idlecompaction) |
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32253227Exit with code 2 to block compaction. For a manual `/compact`, the stderr message is shown to the user. You can also block by returning JSON with `"decision": "block"`.
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32523254| Matcher | When it fires |
32533255| :- | :- |
32543256| `manual` | After `/compact` |
3255| `auto` | After auto-compact when the conversation reaches the [auto-compact window](/docs/en/model-config#set-the-auto-compact-window) |
3257| `auto` | After auto-compact when the conversation reaches the [auto-compact window](/docs/en/model-config#set-the-auto-compact-window), and after [idle compaction](/docs/en/settings-reference#idlecompaction) |
32563258
32573259#### PostCompact input
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40334035* **Alone on stdout**: when the response is the only text on stdout, it can span several lines, such as pretty-printed `jq` output. Spanning several lines requires Claude Code v2.1.295 or later.
40344036* **On one line of its own**: an async hook can print other text to stdout when the response fits on one line by itself, for example with `jq -c`.
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4036Claude Code validates that JSON response against the same [output schema](#json-output) as synchronous hooks, and drops any field whose value has the wrong type, such as a `systemMessage` that isn't a string, instead of delivering it. Run with `--debug` to see a warning naming each dropped field. Before v2.1.202, malformed JSON output from an async hook could crash the session, and the crash recurred each time the session was resumed.
4038Claude Code validates that JSON response against the same [output schema](#json-output) as synchronous hooks, and drops any field whose value has the wrong type, such as a `systemMessage` that isn't a string, instead of delivering it. Run with `--debug` to see a warning naming each dropped field.
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40384040Async hook completion notifications are suppressed by default. To see them, enable verbose mode with `Ctrl+O` or start Claude Code with `--verbose`.
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40634065else
40644066 MSG="Tests failed after editing $FILE_PATH: $RESULT"
40654067fi
4066jq -nc --arg msg "$MSG" '{hookSpecificOutput: {hookEventName: "PostToolUse", additionalContext: $msg}}'
4067```
4068
4069Then add this configuration to `.claude/se
4068jq -nc
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