---
status: accepted
date: 2026-04-29
decision-makers: R&D Lead
tags: [process]
---

# Pre-commit hooks and Conventional Commits

## Context and Problem Statement

Without local enforcement, trivial issues — unformatted code, lint errors, ill-formed commit messages — only surface in CI. Each round-trip costs minutes of feedback latency and pollutes the commit history with fixup noise. We need a lightweight, well-known mechanism that catches these issues at commit time and enforces a consistent commit message format, while staying fast enough not to discourage frequent commits.

Which tooling do we adopt for git pre-commit checks and commit message validation?

## Decision Drivers

* Fast feedback: catch trivial issues locally; CI is defense in depth, not the first line.
* Consistency of code style and commit history across contributors.
* Conventional commit history that machines can read (later automation: changelog, release notes, semver bumps).
* Mainstream tooling — no exotic shell hooks, no single-maintainer projects.
* Easy onboarding: no extra runtime to manage beyond Node/pnpm.

## Considered Options

* **Husky + lint-staged + commitlint with Conventional Commits.** (Chosen.)
* No git hooks — rely on CI.
* `pre-commit` (Python framework).
* `lefthook` (Go single-binary hook manager).
* Custom shell scripts in `.git/hooks/`.

## Decision Outcome

Chosen option: **Husky + lint-staged + commitlint, with [Conventional Commits](https://www.conventionalcommits.org/) as the commit-message specification**.

Hooks installed under `.husky/`:

| Hook | Action |
| --- | --- |
| `pre-commit` | `pnpm exec lint-staged` — runs lint and format on staged files only |
| `commit-msg` | `pnpm exec commitlint --edit "$1"` — validates the commit message against Conventional Commits |

Configuration:
- `package.json`: `"prepare": "husky"` script (Husky 9+ pattern), `lint-staged` config block.
- `commitlint.config.cjs`: `module.exports = { extends: ['@commitlint/config-conventional'] }`.

Scope of `lint-staged`: only fast checks on staged files (lint, format). Type-check and tests stay in `pnpm nx affected -t lint test build` in CI — running the full graph on every commit would slow commits unacceptably and discourage frequent commits.

CI re-runs the same checks (defense in depth — hooks can be bypassed with `--no-verify`).

### Consequences

* Good, because trivial issues are caught locally and don't pollute PR history.
* Good, because Conventional Commits gives us a machine-readable history — enables automated changelogs, semver inference, and release tooling without retroactive cleanup.
* Good, because Husky / lint-staged / commitlint are the de facto standard in JS/TS projects — wide community, abundant documentation, low surprise factor.
* Good, because lint-staged keeps commit time low (only changed files are checked).
* Bad, because hooks can be bypassed (`git commit --no-verify`); CI must remain authoritative.
* Bad, because Husky 9 changed its installation pattern (no `husky install`, just `husky`); contributors with stale instructions can be confused. Mitigated by the setup guide.
* Bad, because Conventional Commits adds a small learning curve; mitigated by IDE plugins, `commitlint` error messages, and a one-page contributor cheatsheet (future doc).

### Confirmation

* `package.json` declares `husky`, `lint-staged`, `@commitlint/cli`, `@commitlint/config-conventional` as `devDependencies`.
* `package.json` has a `"prepare": "husky"` script.
* `.husky/pre-commit` runs `pnpm exec lint-staged` and is executable.
* `.husky/commit-msg` runs `pnpm exec commitlint --edit "$1"` and is executable.
* `commitlint.config.cjs` exists at the workspace root and extends `@commitlint/config-conventional`.
* CI pipeline (future ADR) re-runs lint and format checks on every push, plus a Conventional Commits validation on the PR commit range.

## Pros and Cons of the Options

### Husky + lint-staged + commitlint (chosen)

* Good, because the trio is the de facto standard in the JS/TS ecosystem.
* Good, because each tool is single-purpose and composable.
* Good, because the configuration lives with the repo and is versioned with the code.
* Bad, because three packages instead of one — slightly more dependency surface.

### No git hooks

* Good, because zero local setup.
* Bad, because every trivial issue costs a CI round-trip. Wasteful and noisy.

### `pre-commit` (Python)

* Good, because language-agnostic, used in mixed-language repos (Python + JS + Go).
* Bad, because adds a Python runtime dependency to a Node-only project — extra setup for contributors, especially under WSL where Python toolchains are not always uniform.

### lefthook

* Good, because single Go binary, very fast, parallel hook execution, declarative YAML config.
* Bad, because smaller community than Husky in JS/TS land; less prior art and fewer answers when something breaks.
* Status: kept on the watch list for re-evaluation if commit performance becomes a pain.

### Custom shell scripts in `.git/hooks/`

* Good, because zero dependency.
* Bad, because hooks aren't versioned with the repo by default; a wrapper layer is needed anyway. Bricolage.

## More Information

* Husky: https://typicode.github.io/husky/
* lint-staged: https://github.com/lint-staged/lint-staged
* commitlint: https://commitlint.js.org/
* Conventional Commits: https://www.conventionalcommits.org/
* Related: future quality / CI ADR will re-run these checks as defense in depth.