Add agent-approval-check composite action

agent-approval-check/README.md

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+# Agent Approval Check
+
+Require **N human approvals** on any pull request that contains commits
+authored by an AI agent (Claude, Claude Code, or any bot identity you
+configure). PRs without agent activity are unaffected.
+
+This is the same gate Anthropic runs internally on every agent-authored PR.
+
+## What it does
+
+When a PR is opened, pushed to, or commented on, this action:
+
+1. Scans the PR's commits, author, and reviews for the configured agent
+   identities (committer email, bot login, or an `APPROVED` review from a
+   bot). If none are found it posts `success: No agent activity` and stops.
+2. Counts distinct human approvals: the latest `APPROVED` review per login,
+   plus any `/approve <head-sha>` comment whose SHA matches the current
+   head. Only users with write access to the repo count (verified per-user
+   via the collaborators permission API); agent and excluded-bot logins
+   never count.
+3. Posts an `agent-approval-check` commit status (`success` once the count
+   reaches `required_approvals`, otherwise `pending`) and a sticky PR
+   comment explaining what's still needed.
+4. Re-evaluates on every new push or comment. A push moves the head SHA,
+   so earlier `/approve <old-sha>` comments are flagged stale. Approving
+   reviews still count toward the threshold — they're picked up the next
+   time the workflow runs (on push or `/approve`); they just don't trigger
+   a run on their own.
+
+Mark `agent-approval-check` as a **required status check** on your protected
+branches and GitHub will refuse to merge until it's green.
+
+## Setup
+
+Copy [`examples/agent-approval-check.yml`](../examples/agent-approval-check.yml)
+into `.github/workflows/` in your repo, then add `agent-approval-check` to the
+required status checks on your protected branch.
+
+This action is designed to run **alongside** GitHub's native branch
+protection, not replace it. On the same protected branch you should also:
+
+1. Require at least 1 approving review from someone with write access.
+2. Enable **Dismiss stale pull request approvals when new commits are pushed**.
+
+```yaml
+name: agent-approval-check
+on:
+  pull_request_target:
+    types: [opened, synchronize, reopened, ready_for_review]
+  issue_comment:
+    types: [created]
+permissions:
+  contents: read
+  pull-requests: write
+  statuses: write
+jobs:
+  check:
+    if: github.event_name != 'issue_comment' || github.event.issue.pull_request
+    runs-on: ubuntu-latest
+    steps:
+      - uses: anthropics/claude-code-action/agent-approval-check@main
+        with:
+          required_approvals: 2
+          agent_emails: noreply@anthropic.com
+          agent_logins: claude[bot],claude-code[bot]
+```
+
+## Inputs
+
+| Input                  | Default                        | Meaning                                                                                                                               |
+| ---------------------- | ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------- |
+| `required_approvals`   | `2`                            | Distinct human approvals needed.                                                                                                      |
+| `agent_emails`         | `noreply@anthropic.com`        | Committer emails that mark a commit agent-authored.                                                                                   |
+| `agent_logins`         | `claude[bot],claude-code[bot]` | Logins treated as agents (PR author or approving reviewer).                                                                           |
+| `excluded_approvers`   | _(empty)_                      | Logins whose approvals never count.                                                                                                   |
+| `exempt_head_branches` | _(empty)_                      | Head-branch globs that auto-pass. ⚠️ Leave empty — branch names are attacker-controlled, so this is not a safe place to encode trust. |
+| `exempt_path_prefixes` | _(empty)_                      | PRs touching only these prefixes auto-pass.                                                                                           |
+| `protected_bases`      | _(default branch)_             | Base branches this check gates (see threat model).                                                                                    |
+| `config_file`          | _(empty)_                      | Path to an [agent-identities YAML](./agent-identities.example.yaml) replacing the inline inputs. See the warning below.               |
+| `docs_url`             | this README                    | Link in the PR comment footer.                                                                                                        |
+| `github_token`         | `${{ github.token }}`          | Needs `statuses:write` + `pull-requests:write`.                                                                                       |
+
+> ⚠️ **`config_file` and checkout:** if you set `config_file`, your workflow
+> must check out the **base** branch to read it (the default behaviour of
+> `actions/checkout` under `pull_request_target`). Never check out the PR
+> head ref — doing so would let the PR author control the config and bypass
+> this check.
+
+## Approving
+
+A human counts as an approver by either:
+
+- submitting a normal GitHub **Approve** review, or
+- commenting `/approve <sha>` where `<sha>` is the current head commit
+  (12–40 hex chars). This path lets the PR author — who can't approve their
+  own PR in GitHub's UI — vouch for commits an agent pushed on their behalf.
+  The author's `/approve` is subject to the same write-access verification
+  as any other approver, so a fork-PR author without write access on the
+  base repository cannot self-count. The author counts as **one** approval;
+  the remaining approvals must come from other reviewers with write access.
+
+## Threat model
+
+- **Tamper-proof triggers.** `pull_request_target` and `issue_comment` run
+  the workflow file from the base/default branch, so the PR under review
+  cannot edit this check. `pull_request_review` does **not** share this
+  property — it runs from the merge ref — so the example workflow omits it;
+  native Approve reviews are picked up on the next synchronize or
+  `/approve` comment. This tamper-resistance assumes the workflow file
+  itself is protected: an actor who can push workflow changes to the
+  default branch can spoof any required status check, including this one,
+  so protect `.github/workflows/` via branch protection or CODEOWNERS.
+- **Fail-closed.** Any unhandled error exits non-zero; the required status
+  stays non-success and the PR stays blocked. PRs with >100 commits are
+  treated as agent-authored because the full commit list can't be verified.
+- **Sibling-PR guard.** Commit statuses attach to a SHA, not a PR. The
+  action refuses to post a status on a PR whose base isn't in
+  `protected_bases`, and withholds `success` while another open PR to a
+  protected base shares the same head commit — otherwise a green status on
+  one PR would also unblock the other.
+- **No checkout of PR code.** The action never checks out the PR's branch;
+  it reads PR metadata via the GitHub API, so the usual
+  `pull_request_target` code-execution risk does not apply.

agent-approval-check/action.yml

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+name: Agent Approval Check
+description: |
+  Require N human approvals on PRs that contain agent-authored commits
+  (Claude, Claude Code, or any configured bot identity). Posts an
+  `agent-approval-check` commit status — mark it as a required check on
+  protected branches to gate merges.
+
+inputs:
+  github_token:
+    description: Token with statuses:write and pull-requests:write on this repo.
+    default: ${{ github.token }}
+  required_approvals:
+    description: Number of distinct human approvals required. Must be >= 1.
+    default: "2"
+  agent_emails:
+    description: Comma-separated committer emails treated as agent-authored.
+    default: noreply@anthropic.com
+  agent_logins:
+    description: |
+      Comma-separated GitHub logins treated as agents — a PR opened by, or an
+      APPROVED review from, one of these triggers the check.
+    default: claude[bot],claude-code[bot]
+  excluded_approvers:
+    description: Comma-separated logins whose approvals never count (e.g. rubber-stamp bots).
+    default: ""
+  exempt_head_branches:
+    description: |
+      Comma-separated glob patterns; PRs from matching head branches auto-pass.
+      WARNING: leave empty — branch names are attacker-controlled, so this is
+      not a safe place to encode trust.
+    default: ""
+  exempt_path_prefixes:
+    description: Comma-separated path prefixes; PRs touching only these auto-pass.
+    default: ""
+  protected_bases:
+    description: |
+      Comma-separated base branches this check gates. Empty = the repo's
+      default branch only. PRs targeting any other base are refused (no
+      status posted) so a sibling PR sharing the head SHA can't get the
+      shared commit stamped green.
+    default: ""
+  config_file:
+    description: Optional path to an agent-identities YAML file (overrides the inline inputs).
+    default: ""
+  docs_url:
+    description: Link shown in the PR comment footer.
+    default: "https://github.com/anthropics/claude-code-action/tree/main/agent-approval-check"
+
+runs:
+  using: composite
+  steps:
+    - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
+      with:
+        python-version: "3.12"
+    - run: pip install 'httpx==0.28.1' 'pyyaml==6.0.3' 'tenacity==9.1.4'
+      shell: bash
+    - run: python "${{ github.action_path }}/agent_approval_check.py"
+      shell: bash
+      env:
+        GH_TOKEN: ${{ inputs.github_token }}
+        GH_REPOSITORY: ${{ github.repository }}
+        GH_EVENT_NAME: ${{ github.event_name }}
+        GH_EVENT_PATH: ${{ github.event_path }}
+        REQUIRED_APPROVALS: ${{ inputs.required_approvals }}
+        AGENT_EMAILS: ${{ inputs.agent_emails }}
+        AGENT_LOGINS: ${{ inputs.agent_logins }}
+        EXCLUDED_APPROVERS: ${{ inputs.excluded_approvers }}
+        EXEMPT_HEAD_BRANCHES: ${{ inputs.exempt_head_branches }}
+        EXEMPT_PATH_PREFIXES: ${{ inputs.exempt_path_prefixes }}
+        PROTECTED_BASES: ${{ inputs.protected_bases }}
+        CONFIG_FILE: ${{ inputs.config_file }}
+        DOCS_URL: ${{ inputs.docs_url }}

agent-approval-check/agent-identities.example.yaml

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+---
+# Optional config-file form of the agent-approval-check inputs.
+# Pass via `with: { config_file: .github/agent-identities.yaml }` instead of
+# the inline `agent_emails` / `agent_logins` / … inputs.
+
+# Committer emails that mark a commit as agent-authored.
+agent_emails:
+  - noreply@anthropic.com
+
+# GitHub logins treated as agents — a PR opened by, or an APPROVED review
+# from, one of these triggers the check.
+agent_app_logins:
+  - claude[bot]
+  - claude-code[bot]
+
+# Logins whose approvals never count toward the required total.
+excluded_approver_logins: []
+
+# Head-branch glob patterns that auto-pass. Leave empty: branch names are
+# attacker-controlled, so this is not a safe place to encode trust.
+exempt_head_branches: []
+
+# Per-repo path prefixes whose PRs auto-pass when ONLY those paths change.
+exempt_path_prefixes:
+  owner/repo:
+    - docs/
+
+# Per-repo base branches this check gates. A repo with no entry defaults to
+# its default branch only. Listing a repo here REPLACES that default.
+protected_bases:
+  owner/repo:
+    exact: [main]
+    prefixes: [release/]