Docs/Advanced: command line/Hooks

Hooks

Hooks are shell commands that fire automatically on events — before tool calls, after edits, when the model finishes. Configure in dynamo.yaml or .dynamo/hooks/*.yaml.

Configuration

yaml

hooks:
  - event: PreToolUse
    matcher: "run_command"
    if: "rm -rf"
    command: "echo 'blocked' >&2; exit 2"

  - event: PostToolUse
    matcher: "edit_file"
    command: ".dynamo/hooks/lint.sh"

  - event: Stop
    command: ".dynamo/hooks/build-gate.sh"
    timeout: 30000

Hooks can also be defined in separate files under .dynamo/hooks/*.yaml (project) or ~/.config/dynamo/hooks/*.yaml (global).

Events

Event	When	Use case
PreToolUse	Before tool executes	Block dangerous commands, modify input
PostToolUse	After tool executes	Auto-lint, inject build errors as context
Stop	Model finishes responding	Build gates — model auto-fixes errors
SessionStart	Session begins	Environment checks, context loading
SessionEnd	Session ends	Cleanup, metrics, logging

Matching

●`matcher` — exact tool name, or several separated by | (e.g. "edit_file|write_file"). Only used on PreToolUse and PostToolUse; other events ignore it.
●`if` — plain text that must appear somewhere in the tool call's input (case-sensitive). "rm" also matches words like format, so make it specific, e.g. "rm -rf".

Sequential execution, first block wins.

Exit Codes

Code	Meaning
`0`	Approve — continue execution. Parse stdout as JSON for structured output.
`2`	Block — prevent the tool from executing
Other	Warn — show a warning but continue

Hooks receive JSON on stdin: event, toolName, toolInput, toolOutput and toolIsError (PostToolUse), sessionId, timestamp, and stop_hook_active (Stop). On exit 0, stdout can be JSON with action, reason, updatedInput (PreToolUse: change the tool's input), additionalContext (added for the model), or continue: true (Stop: keep going). timeout is in milliseconds and defaults to 10000.

Managing Hooks

Settings → Advanced → Hooks in Dynamo Engine — In the app: Settings → Advanced → Hooks

Use /hooks to browse configured hooks — a 3-level picker showing event types, numbered hook list, and detail view with execution history.

Trusting project hooks

Hooks that live in the project (dynamo.yaml or .dynamo/hooks/*.yaml) run only after you trust the folder once:

bash

dynamo hooks trust

Trust takes effect the next time you launch `dynamo` — the gate is read once at startup, and there's no in-session way to re-trust, so running the command in a second terminal while Dynamo is open won't make hooks start firing.

The trust check is fingerprinted over the hook set, so it asks again after you add or change a project hook — that's deliberate, since a hook is arbitrary shell. Personal hooks in your Dynamo config dir (~/.config/dynamo/hooks/ on macOS and Linux, %APPDATA%\dynamo\hooks\ on Windows) always run. Dynamo tells you at startup when project hooks are waiting on trust.

Examples

Auto-lint after edits

yaml

hooks:
  - event: PostToolUse
    matcher: "edit_file"
    command: "jq -r '.toolInput.path' | xargs -r npx eslint --fix"

Build gate on Stop

yaml

hooks:
  - event: Stop
    command: "npm run build 1>&2 || exit 2"
    timeout: 30000

When a Stop hook exits with code 2, Dynamo sends its stderr back to the model, which fixes the errors and tries again. Any other non-zero code only shows a warning.

Block dangerous commands

yaml

hooks:
  - event: PreToolUse
    matcher: "run_command"
    if: "docker"
    command: "echo 'Docker commands blocked' >&2; exit 2"

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