One could build a simple version of this easily - e.g. setup an endpoint that listens for the particular event you are concerned with, and fire off the headless agent with your hook specific prompt - but the amount of work involved to listen for that particular event while filtering out noise and orchestrating the task is actually not trivial.
Plus, that involves writing a lot of code. It's really magical to express all of this in natural language.
For example, this is the YAML frontmatter for a a daemon that keeps a GitHub PR in a mergeable state in the event of CI failures or branch base changes.
---
id: pr-mergeability
purpose: Keep non-draft pull requests mergeable and CI-green without changing PR intent/scope, while staying anchored to one trigger context per run.
watch:
- Branch sync and update events on non-draft PRs.
- Check-status signals on non-draft PRs for checks that affect mergeability.
routines:
- Resolve mechanical merge conflicts when the safe resolution is clear and preserves PR intent/scope.
- 'Apply low-risk mergeability fixes: snapshot updates, lockfile drift fixes, lint autofix, and flaky-test retries when tied to the trigger context.'
- Escalate semantic/intention conflicts between base and branch instead of auto-resolving.
deny:
- When triggered by a check-status signal, do not fix or comment on unrelated failing checks.
- Do not open new pull requests or new issues.
- Do not review, approve, or request changes on pull requests.
- Do not implement review-comment suggestion patches.
- Avoid force-push by default; if force is absolutely required, use `--force-with-lease` only after fresh remote verification.
- Do not make changes beyond mergeability maintenance.
---
Note the lack of any code or required knowledge of GitHub webhooks.
Seems the markdown input, code output is a very common theme, I use OpenSoucreContracts(https://github.com/s1ugh34d/osc) to have LLM's build software, but building the harness into the contracts is elegant. Combined with prose I sort of have this. With LLM's and the sandbox life, software generation is coming.
But pardon my ignorance, but one could quite easily roll this themselves? Script the hooks and fire off a headless agent with a hook specific prompt.