LintPal

Turn your freeform engineering rules into PR checks.

Use System One models like Jev through compatible Decisions APIs. LintPal checks Git changes against your team's Markdown rules and reports findings on changed lines. Gate CI by severity, run locally, or publish reviews directly to GitHub.

LintPal is part of the DiffPal family. It checks explicit repository rules; DiffPal provides broader AI pull-request review across GitHub, GitLab, and Azure DevOps.

Website · Quickstart · Documentation · Rule packs · Demo PR (v0.5.0)

For example, a Go error-handling rule can flag a violating changed line in a pull request; the configured severity gate can then fail the check.

Features

• Provider choice: use TypeSafe/Jev, OpenRouter, OpenAI, or your own compatible Decisions service with the same repository rules and CI workflow.
• Freeform rules: write one clear requirement per Markdown file, with optional severity and decision-threshold policy in frontmatter.
• Rule packs: import a local directory or a versioned GitHub catalog, then review and commit the rules with your code.
• Gating: choose which finding severities block CI while retaining the complete findings artifact after each successful evaluation.
• Platform feedback: publish a GitHub review summary and inline comments, or consume the same findings as JSON or Markdown in CI.

Supported Providers

Choose the provider that fits your account and deployment. Your Markdown rules, findings, and severity gate work the same way across providers.

| Provider | Choose it for | CLI option | Credential | | --- | --- | --- | --- | | TypeSafe / Jev | Direct access to Jev; the default setup | --provider jev | TYPESAFE_API_KEY | | OpenRouter | Decisions through your OpenRouter account | --provider openrouter | OPENROUTER_API_KEY | | OpenAI | Native OpenAI Decisions API support | --provider openai --model gpt-6-luna | OPENAI_API_KEY | | Custom | Your own compatible service, including a local endpoint | --provider custom --base-url <url> --api-path <path> | LINTPAL_TOKEN or your chosen token variable |

All four provider options are included. The OpenAI preset uses the official POST /v1/decisions schema. As of October 6, 2026, OpenAI describes Decisions API as a limited preview, so access may depend on the API account. See provider setup and commands for all four options. The quickstart below uses TypeSafe/Jev.

How It Works

| Stage | What LintPal does | | --- | --- | | Rules | Loads the repository's .lintpal/rules/**/*.md requirements | | Diff | Reads changed lines from the unique merge base through head, or from HEAD to the working tree with --uncommitted | | Evaluation | Evaluates each applicable rule through the selected AI provider | | Findings | Writes findings tied to changed lines as JSON or Markdown | | Feedback (optional) | feedback github publishes GitHub comments; --gate applies the stored severity gate after publication |

Your repository defines the rules. Review and update them alongside the code as your team's requirements change.

Minimal GitHub Quickstart

Use Git and Node.js 16 or newer. npm packages provide native binaries for Linux and macOS (x64 and arm64), and Windows (x64). Install the CLI globally and add a versioned rule pack in your repository:

npm install -g lintpal
lintpal rule import github:diffpal/lintpal-rules//[email protected] --prefix general
lintpal rule validate

Review and commit .lintpal/rules/ so the workflow can load the rules. The selected remote provider receives bounded source context and rule text. Check whether that transfer is permitted for your repository before adding TYPESAFE_API_KEY as an Actions secret; see privacy. Then create .github/workflows/lintpal.yml:

name: lintpal

on:
  pull_request:
    types: [opened, synchronize, reopened, ready_for_review]

jobs:
  lint:
    if: ${{ !github.event.pull_request.draft && github.event.pull_request.head.repo.full_name == github.repository }}
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: write
    steps:
      - uses: actions/checkout@v7
        with:
          fetch-depth: 0
      - uses: actions/setup-node@v6
        with:
          node-version: 24
      - run: npm install -g lintpal
      - name: Lint pull request
        run: |
          mkdir -p .artifacts/lintpal
          lintpal lint --no-env-file --provider jev \
            --base ${{ github.event.pull_request.base.sha }} \
            --head ${{ github.event.pull_request.head.sha }} \
            --block-on high --format json --out .artifacts/lintpal/findings.json
        env:
          TYPESAFE_API_KEY: ${{ secrets.TYPESAFE_API_KEY }}
      - name: Publish review and apply gate
        run: lintpal feedback github --in .artifacts/lintpal/findings.json --gate
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
      - uses: actions/upload-artifact@v4
        if: always()
        with:
          name: lintpal-findings
          path: .artifacts/lintpal/
          if-no-files-found: warn

Open a same-repository pull request. LintPal publishes a review with No blocking findings, 1 blocking finding, or N blocking findings, plus inline comments for eligible new or changed findings. Unchanged comments are deduplicated on later runs. The gate runs after publication; the workflow keeps .artifacts/lintpal/findings.json even when a blocking finding fails the job. Draft and fork pull requests are skipped. GitHub supplies the pull-request context to the feedback command.

See the CLI reference for provider selection, feedback commands, and exit codes. The LintPal Action is also available for workflows that prefer an Action wrapper.

Write Rules in Markdown

The file path beneath .lintpal/rules/ is the rule ID. The body is the requirement. Optional frontmatter controls its policy:

---
severity: high
threshold: 0.97
title: Unchecked error
---

Handle errors returned by calls when failure changes the result or behavior.

Save this rule as .lintpal/rules/go/unchecked-error.md. When the provider assigns a violation probability of at least 0.97, a finding identifies the changed file and line, the high severity, and rule ID go/unchecked-error.md. Its message is Changed code may violate go/unchecked-error.md. The default severity gate blocks on high or critical findings.

Rules are ordinary project files: review them, version them, and change them through the same pull-request process as code.

lintpal rule list
lintpal rule view general/authorization.md
lintpal rule validate
lintpal rule import github:diffpal/lintpal-rules//[email protected] --prefix go

Read rule authoring for the complete format and rule import for local and pinned GitHub sources.

Run Locally

Install the CLI and add rules using the getting started guide. Then run from your Git repository to check working-tree changes before committing or compare two committed revisions:

export TYPESAFE_API_KEY='your-provider-key'
lintpal doctor

# Lint uncommitted working-tree changes (staged, unstaged, and untracked regular files)
lintpal lint --uncommitted

# Or lint committed revisions
lintpal lint --base origin/main --head HEAD

Committed comparisons start at the unique merge base of base and head; changes found only on the base branch are excluded. See the CLI reference for report revision fields and uncommitted behavior.

Markdown findings go to stdout. Use --out to retain the complete JSON artifact, or --format json for JSON on stdout. The default gate returns exit code 10 when a high or critical finding blocks the run.

Choose TypeSafe/Jev, OpenRouter, OpenAI, or a custom compatible endpoint from Supported Providers. Configure credentials through environment variables or an uncommitted .env file. The selected remote provider receives bounded source context and rule text. See configuration and privacy.

Documentation by Goal

| Goal | Start here | | --- | --- | | Run the first check | Getting started | | Configure providers and policy | Configuration | | Write project rules | Rule authoring | | Import reusable rule packs | Rule import | | Understand findings and gates | Report reference | | Automate the CLI | CLI reference | | Review security and data flow | Privacy and architecture | | Ask a setup question | GitHub Discussions Q&A | | Suggest a workflow improvement | GitHub Discussions Ideas | | Report a bug or incorrect finding | GitHub Issues | | Contribute to LintPal | Contributing |

License

LintPal is released under the MIT License.