hook-author

name	hook-author
description	Author a new git or runtime hook with a parity test to prove it behaves identically across both runtime surfaces (OpenCode/Claude).

hook-author

Purpose

Author a new hook that works correctly on both the git surface AND the runtime tool surface from a single shared implementation. The parity test proves the hook catches the same violations, produces the same messages, and respects the same enforcement mode regardless of which surface triggered it.

When to use

• Adding a new hook (git or runtime).
• Modifying an existing hook's logic.
• Changing a hook's enforcement mode (warn <-> block).

Procedure

1. Define the hook's purpose and which violations it detects.
2. Author the hook logic ONCE as a Python module under .aspis/scripts/hooks/ — this is the shared core. Per R-006, never copy logic between surfaces.
3. Create the git-surface entry point (shell script in .git/hooks/) that imports the shared module.
4. Create the runtime-surface entry point (OpenCode plugin / Claude PreToolUse hook) that imports the SAME shared module. No second copy.
5. Write a parity test: run identical scenarios (clean commit, violation commit) through BOTH surfaces; assert identical exit codes, error messages, violation counts, and enforcement behavior.
6. Set the enforcement mode: warn for pre-commit (auto-fixes, non-blocking), block for runtime tools (hard wall). Read the mode from config, not from the hook body.
7. Register the hook in hooks.yaml so the system knows it exists.

Outputs

• A new hook module in .aspis/scripts/hooks/.
• Both surface entry points (git + runtime).
• Parity test results proving identical behavior across surfaces.
• Updated hooks.yaml registration.

Anti-patterns

• Copy-pasting hook logic between surfaces instead of sharing a module (R-006 violation — the rule is "two surfaces, one shared core").
• Testing only one surface and assuming the other works.
• Authoring a hook without a parity test — untrustworthy by construction.
• Hard-coding enforcement mode in the hook body instead of reading config.
• Blocking but ignoring the ASPIS_ENFORCEMENT env var override.