What it does

On every pull request, it:

1. Finds issues with a deterministic scanner over the diff — introduced secrets, dangerous CI permission / OIDC changes, pull_request_target + curl|sh footguns, unpinned third-party actions, prompt-injection surfaces in instruction files (README/CLAUDE.md/…), dynamic-exec / disabled-TLS smells, and changes to protected paths.
2. Cross-verifies those findings against deterministic gates: the repo's required status check (looked up from the GitHub API), a clean secret scan, and no forbidden permission change.
3. Recommends a verdict — 🟢 safe · 🟡 needs_human · 🟣 third_party (escalate to a code owner) · 🔴 block — and posts one PR comment.
4. Optionally, enables auto-merge — opt-in, off by default, and only ever on a safe verdict whose eligibility came from green deterministic gates (see the safety model).

The safety model (why it won't rubber-stamp your repo)

This mirrors Umbra's own principle: an agent must not approve its own authority.

• The reviewer is advisory. Its findings never grant mergeability.
• The authority to merge is the deterministic gate — a required status check + a clean secret scan + no forbidden permission change — plus a human.
• A model finding (if you wire one in) is recorded but can never be blocking and can never flip a gated-clean PR away from safe on its own.
• Auto-merge is opt-in and, even then, uses GitHub's native auto-merge (the PR merges only when branch-protection required checks pass). The bot never force-merges; the platform does, only if your rules allow.
• A blocking finding or a failed/absent required check → block / needs_human. Sensitive surface (workflows, Dockerfiles, auth, secrets) → third_party, always escalated to a human.
• A green verdict is not a guarantee — deterministic scanners have false negatives. It's defense-in-depth, not a proof.

Use it (GitHub Action)

# .github/workflows/review.yml
name: Umbra Reviewer
on: { pull_request: {} }
permissions:
  contents: read
  pull-requests: write     # to post the review comment (+ enable auto-merge if opted in)
  checks: read
jobs:
  review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with: { fetch-depth: 0 }
      - uses: bkd-dotcom/umbra-reviewer@v1
        with:
          required-check: "Umbra Admission"   # cross-verify your merge gate (optional)
          protected-paths: "infra/**,src/auth/**"
          # auto-merge: "true"                 # opt in; still needs green branch-protection checks

Use it (CLI)

pip install umbra-reviewer

git diff origin/main...HEAD | umbra-reviewer review --repo owner/name --pr 12 \
  --required-check success --comment-out comment.md
# exit 1 on a BLOCK verdict, so it gates CI. Add --fail-on-needs-human for a stricter gate.

Pairs with the rest of Umbra

• umbra-action is the hard gate (the required check + signed receipt). umbra-reviewer is the advisory layer on top; point required-check at the Umbra Admission check to cross-verify.
• umbra-core is the governance kernel.

License

MIT © 2026 Binay Dalai.