linebreak-gate — the LineBreak security gate at the git/CI boundary

Blocks merges that carry known vulnerabilities. One tool, two detectors — dependency scanning is free; the AI review is the Pro upgrade:

• Dependency CVE scan — free, no key — osv-scanner across every ecosystem (npm, PyPI, Go, Cargo, Maven, …), with an npm audit fallback for npm projects (npm-only coverage and no installed-version data — the GitHub Action fails closed if osv-scanner can't be installed instead of degrading to it).
• AI SAST — Pro — an LLM security review of first-party source (injection, broken auth, secret exposure, SSRF, unsafe deserialization, crypto misuse) with adversarial verification, enabled by LINEBREAK_LICENSE_KEY (hosted, uses credits) or ANTHROPIC_API_KEY (your own key, takes precedence). Without a key the dependency scan still runs and this pass is skipped with a notice.

The gate blocks and can propose; it never auto-clears on an agent's say-so. A human approves the fix or records an override — with a reason and an approver — in a git-committed audit file.

This is the same scanner core that powers the LineBreak desktop app's in-app security gate (the desktop backend imports this package), but it is fully standalone: a team that has never opened the desktop app can add the gate to their repo and get real enforcement.

Where this code lives. Development happens in the LineBreak monorepo (packages/gate); every green change to it is automatically mirrored to Baktun-Studio/linebreak-gate (the public repo the Action snippet uses) and published to PyPI as linebreak-gate. Never edit the mirror directly — the next sync overwrites it. Licensed Apache-2.0.

Quickstart — GitHub Actions

# .github/workflows/security-gate.yml
name: Security gate
on:
  pull_request:

permissions:
  contents: read
  pull-requests: write # for the summary comment

jobs:
  gate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v5
      - uses: Baktun-Studio/linebreak-gate@v1
        with:
          # fail-on: high # blocking floor; default: critical
          # Optional today; required once license enforcement is enabled.
          license-key: ${{ secrets.LINEBREAK_LICENSE_KEY }}
          # Enables the AI code review; leave unset for dependency scan only.
          anthropic-api-key: ${{ secrets.ANTHROPIC_API_KEY }}

The action runs linebreak-gate scan, always runs report, posts one PR comment (updated in place on every push, never spammed), uploads the JSON report + audit artifacts as a workflow artifact, and fails the check per the scan's exit code.

Make it a real boundary: require the check

A CI job that can be ignored is a dashboard, not a gate. In your repo:

Settings → Branches → Branch protection rules → your default branch → "Require status checks to pass before merging" → add the gate job (the name of the job that runs this action). From then on a PR carrying a critical CVE cannot be merged through the GitHub UI.

Quickstart — any other CI (GitLab example)

The CLI is a plain Python package with strict exit codes — 0 pass, 1 blocking findings, 2 tool/config error (fail closed: a scanner crash fails the pipeline, it is never a clean pass). Any CI that respects exit codes gets the same enforcement:

# .gitlab-ci.yml
security-gate:
  image: python:3.11
  script:
    - pip install linebreak-gate
    - curl -fsSL -o /usr/local/bin/osv-scanner
      "$(curl -fsSL https://api.github.com/repos/google/osv-scanner/releases/latest
      | python -c "import json,sys;print(next(a['browser_download_url'] for a in json.load(sys.stdin)['assets'] if a['name'].endswith('linux_amd64')))")"
    - chmod +x /usr/local/bin/osv-scanner
    - linebreak-gate scan
    - linebreak-gate report

Mark the job as required (no allow_failure) and protect the branch.

The spec loop — author, approve, serve over MCP, enforce

The gate also enforces approved acceptance criteria, and the whole loop is tool-agnostic — no LineBreak account, no desktop app, no server:

linebreak-gate spec new        # scaffold a draft — fill it with any tool (your
                               # editor, Claude Code, ChatGPT), or distill it
                               # from the PRD you already have in Notion/Jira
linebreak-gate spec approve .linebreak/spec-draft.yml \
  --approver "Ana Lopez <ana@example.com>"   # a human on the record; commits
linebreak-gate mcp install --editor claude-code   # or: cursor · codex

linebreak-gate mcp serves the approved bundle (.linebreak/spec/) over MCP (stdio) to Claude Code, Cursor, Codex, or any MCP client. Six tools: list_stories, get_story (criteria as agent context BEFORE code is written), next_story, set_story_status, check_story (the same evaluation engine CI runs, scoped to one story), and spec_status (approval + offline signature state). Git is the transport — no network, no account, works on a bare clone — and nothing in the bridge can write, edit, or invalidate an approved criterion: criteria change only by editing the draft and re-approving, with a human on the record.

Then linebreak-gate check enforces the same criteria in CI: machine checks run for real, manual criteria block until a recorded sign-off. Guided first run with the why of every step: linebreakapp.com/en/start.

CLI

linebreak-gate init     [--path .] [--fail-on critical|high|medium|low] [--force] [--non-interactive]
linebreak-gate scan     [--path .] [--fail-on critical|high|medium|low] [--format summary|json]
linebreak-gate report   [--path .] [--format summary|json]
linebreak-gate override --finding <id> --reason "…" --approver <name/email> [--path .]
linebreak-gate override --criterion <id> --reason "…" --approver <name/email> [--path .]
linebreak-gate check    [--path .] [--format summary|json]
linebreak-gate signoff  --criterion <id> --approver <name/email> --note "…" [--path .]
linebreak-gate spec new     [--path .] [--out <file>] [--force]
linebreak-gate spec approve <draft> --approver <name/email> [--role architect] [--path .]
linebreak-gate spec list|next [--path .]
linebreak-gate spec show|check <story-id> [--path .]
linebreak-gate mcp      [--path .]            # serve the approved spec over stdio
linebreak-gate mcp install [--editor claude-code|cursor|codex] [--print]

• init sets a repo up in one command: writes the workflow file (never clobbers an existing one without --force), optionally writes .linebreak/gate.yml, offers to store the secrets via the GitHub CLI and to require the gate check — and prints the exact settings links for anything it can't do for you.

• scan runs both detectors, writes git-native audit artifacts under .linebreak/audit/, and exits 0/1/2.

• report renders the recorded scan: counts by severity and every finding with CVE id, CVSS, advisory link, and override status. --format json for machines.

• override records a human-approved acknowledgment of one exact finding — the package + installed version + CVE tuple. A different CVE, a bumped version, or a new finding still blocks. --reason and --approver are required; the record lands in the artifact's approval trail. Commit the updated .linebreak/audit/*.json so CI sees it.

• check evaluates the approved acceptance criteria (.linebreak/spec/, landed by spec approve — or by the desktop app's gate approval) against the working tree: build/tests/command run for real, manual requires a recorded sign-off. Exit 0 all satisfied (or no bundle — a clean no-op), 1 blocking (fail or needs-signoff), 2 tool/config/bundle error (fail closed). Writes .linebreak/audit/criteria.json.

• signoff records an attributed human sign-off for one manual criterion under .linebreak/spec/signoffs/ (additive; --approver and --note required). It binds to the criterion as approved — editing the criterion and re-approving the spec makes prior sign-offs stale. Commit the record.

• override --criterion records a human-approved override for one failed machine criterion in .linebreak/audit/criteria.json — same philosophy as CVE overrides: possible, always attributed, stale once the criterion is edited. Other blocking criteria still block.

• spec new / spec approve — the tool-agnostic authoring path (see the spec-loop section above): scaffold a draft, fill it with any tool, land it as the approved bundle with an attributed human approval, committed. Unsigned local approvals are marked identity_source: client; cryptographic signatures come from the governance service (license key).

• spec list prints the approved acceptance criteria bundle: each story, its criteria with check types, and the approver attribution. Read-only. Exit 0 on a valid bundle or when none exists; exit 2 on a malformed bundle (fail closed on structure). spec next / show / check are the CLI twins of the MCP bridge tools.

Configuration — .linebreak/gate.yml

The gate's strictness is governance, so it lives in the repo — changing the threshold is itself a PR: visible, reviewable, attributable in git history.

# .linebreak/gate.yml
fail_on: critical # critical (default) | high | medium | low
exclude_paths: # optional: root-relative globs excluded from scanning
  - fixtures
  - "sandbox/*"
code_scan: auto # auto (run when model credentials are set) | on (required) | off
criteria:
  enforce: true # default: true whenever a spec bundle exists; false disables
  # criteria checking only (the security scan is unaffected)

Precedence: explicit --fail-on flag / Action input → .linebreak/gate.yml → built-in default (critical). An invalid config is a tool error (exit 2) — a broken governance file never silently falls back to a default.

Audit records

Every scan and every override is recorded in .linebreak/audit/security.json (dependencies) and .linebreak/audit/code.json (AI SAST) — the same versioned document format the LineBreak desktop app writes, carrying findings (CVE id, CVSS, advisory link), scanner engine, timestamp, actor, and the approval trail with each override's reason + approver. Who relaxed the gate, and when, is itself auditable.

Pricing

Freemium. The dependency CVE scan is free — no key, no account; it's the whole gate for teams that only want dependency coverage. The AI review is Pro, unlocked by LINEBREAK_LICENSE_KEY (the Action's license-key input; hosted on credits, or bring ANTHROPIC_API_KEY). Generate the key in the LineBreak desktop app (Settings → Security).

The gate runs open by default: it works without a key and prints a notice when no LINEBREAK_LICENSE_KEY is set (suppressed for BYOK users). That's freemium — the dependency scan runs free. Teams that want to require a valid Pro key for the gate to run at all can opt into LINEBREAK_ENTITLEMENTS_PROVIDER=remote, which checks the entitlement before any scan and fails closed on a missing/invalid/revoked key, wrong plan, or unreachable service — blocking the whole gate, dependency scan included.