lefthook

A standard setup for Lefthook, a tool that runs commands automatically during Git actions such as commit and push. It connects those hooks to mise tasks, which define the actual checks.

In plain words
What is it for?
Use it to configure or debug formatting, static checks, secret scans, tests, and optional post-commit rebuilds.
Why use it?
It keeps local Git checks and continuous-integration checks aligned while separating when checks run from what they do.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/fmind/dotfiles/lefthook
Any agent
npx skills add fmind/dotfiles --skill lefthook
Clone the repo
git clone --depth 1 https://github.com/fmind/dotfiles

Made for: Claude Code, Codex.

Per session 48 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,059 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00048 $0.01059
Opus 5 $0.00024 $0.00530
Sonnet 5 $0.00010 $0.00212
Haiku 4.5 $0.00005 $0.00106

Measured yesterday against content hash 05da562fa067, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

lefthook scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/lefthook/SKILL.md · 72 lines

How it starts

The opening of the file, as written. The whole thing — 72 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Lefthook Git Hooks Standard

Canonical git-hooks setup using lefthook. Keep hooks thin by delegating every command to a mise run task, so local hooks and CI run the exact same checks. Lefthook decides when to run; mise owns what each command does.

Principles

  • pre-commit (fast): format staged files, then run the static checks and secret scan.
  • pre-push (slower): the test suite.
  • post-commit (optional): repair state the commit itself invalidated — for a repo that deploys a binary built from its own sources, rebuild and redeploy it here, guarded so it only fires when the commit touched a real build input. Git ignores this hook's exit status, so it reports without ever blocking a commit.
  • Delegate, don't duplicate: every command is a thin mise run <task>; the command name mirrors the task (format:gomise run format:go). Tasks are owned by the language stack (go-stack, python-stack) — see the mise skill.
  • Staged formatters, whole-tree checks: formatters take {staged_files} and restage their fixes (stage_fixed: true); check/test take no files so they always run on the whole tree — "run everything before commit/push".
  • Clean output: suppress version headers and successful commands to keep commits quiet and distraction-free.

Setup

  1. Add lefthook using mise (Go: go-stack; Python: python-stack).
  2. Create lefthook.yml at the repo root (template below).
  3. Install the hooks: lefthook install (wired into mise run install).

Template

pre-commit:
  parallel: false
  commands:
    format:dprint:
      glob: "*.{json,md,toml,yaml,yml}"
      priority: 10
      run: mise run format:dprint {staged_files}
      stage_fixed: true
    format:<lang>: # one per language: format:go / format:python / format:templ ...
      glob: "*.<ext>"
      priority: 10
      run: mise run format:<lang> {staged_files}
      stage_fixed: true
    check:leaks: # staged secret scan — history-mode gitleaks in `check` can't gate the incoming commit
      priority: 20
      run: mise run check:leaks --staged
    check:
      priority: 30
      run: mise run check
pre-push:
  commands:
    test:
      run: mise run test

Read the full file on GitHub · 72 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 72 lines · 48 tokens per session scan A 05da562fa067

Subscribe to this mod's changes

lefthook is a skill published in the GitHub repository fmind/dotfiles (4 stars, last pushed 2d ago), licensed MIT. It adds 48 tokens to every session and 1,059 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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