POC: Action to invoke Claude Code reviews

.github/workflows/claude-review.yml

@@ -0,0 +1,116 @@
+name: Claude PR Review
+
+# Read-only PR review by Claude Code.
+#
+# ┌─────────────────────────────────────────────────────────────────────────┐
+# │ TEMPORARY TEST TRIGGER — remove before merging to main.                   │
+# │                                                                           │
+# │ The intended trigger is `issue_comment` (comment "/claude-review" on a    │
+# │ PR). But `issue_comment` ONLY runs the workflow version on the DEFAULT    │
+# │ branch, so it cannot be tested from this feature branch. `pull_request`   │
+# │ runs the workflow from the PR branch itself, so we use it here to         │
+# │ validate the action end-to-end before merge. Scoped to `branches: [main]` │
+# │ so it only fires for PRs targeting main. Swap back to the commented-out   │
+# │ `issue_comment` block below before merging.                               │
+# └─────────────────────────────────────────────────────────────────────────┘
+#
+# Scope is deliberately minimal (constraint: Claude may READ the repo + PR and
+# ADD comments, but must NEVER write, commit, or push):
+#   * The job `permissions:` block grants only `pull-requests: write` and
+#     `contents: read`. Because `contents: write` is absent, the GITHUB_TOKEN
+#     itself is physically incapable of pushing a commit — this is the hard
+#     enforcement boundary, independent of anything Claude decides to do.
+#   * `--allowedTools` is defense-in-depth on top: Claude is only handed
+#     read + comment tools, so it never even attempts a write.
+#
+# Minutes budget (3000/mo action limit): `timeout-minutes` caps a runaway run,
+# and `concurrency` cancels a superseded review so repeat pushes don't stack.
+# See .github/CLAUDE_REVIEW.md for the automation notes.
+
+on:
+    # TEMPORARY test trigger — see banner above. Remove before merge.
+    pull_request:
+        types: [opened, reopened, synchronize]
+        branches: [main]
+
+    # INTENDED trigger — uncomment before merge, and re-enable the
+    # `github.event.issue.pull_request` guard + `issue.number` references below.
+    # issue_comment:
+    #     types: [created]
+
+# Only one review per PR at a time; a newer trigger cancels the older run
+# instead of burning minutes on both.
+concurrency:
+    group: claude-review-${{ github.event.pull_request.number }}
+    cancel-in-progress: true
+
+jobs:
+    review:
+        # TEMPORARY guard for the pull_request test trigger: skip drafts and
+        # Dependabot so we don't waste minutes on WIP/bot PRs.
+        # For the intended issue_comment trigger, replace with:
+        #   github.event.issue.pull_request &&
+        #   contains(github.event.comment.body, '/claude-review')
+        if: >
+            github.event.pull_request.draft == false &&
+            github.actor != 'dependabot[bot]'
+        runs-on: ubuntu-latest
+        timeout-minutes: 15
+
+        # Gate 2 (the real enforcement): least-privilege token.
+        # No `contents: write` => no ability to commit or push, ever.
+        permissions:
+            contents: read # read the repo/diff; NOT write
+            pull-requests: write # post the review comment
+            issues: write # sticky comment lives on the issue timeline
+
+        steps:
+            - name: Checkout PR head
+              uses: actions/checkout@v5
+              with:
+                  fetch-depth: 0
+
+            - name: Run Claude review
+              uses: anthropics/claude-code-action@v1
+              with:
+                  # Subscription OAuth token (not API-billed). Generate locally
+                  # with `claude setup-token` and store as a repo/environment
+                  # secret named CLAUDE_CODE_OAUTH_TOKEN.
+                  claude_code_oauth_token: ${{ secrets.CLAUDE_CODE_OAUTH_TOKEN }}
+
+                  # Ephemeral, least-privilege token from the permissions block
+                  # above. This is what actually caps Claude's GitHub reach.
+                  github_token: ${{ secrets.GITHUB_TOKEN }}
+
+                  # TEMPORARY: required for the pull_request test trigger so the
+                  # action runs in tracking-comment mode and posts a review
+                  # (without a @mention to react to). Not needed for the
+                  # issue_comment trigger — remove when reverting.
+                  track_progress: true
+
+                  prompt: |
+                      REPO: ${{ github.repository }}
+                      PR NUMBER: ${{ github.event.pull_request.number }}
+
+                      You are reviewing this pull request. You have READ-ONLY
+                      access: you may read the repository and PR diff and post a
+                      single review comment. You cannot and must not attempt to
+                      commit, push, edit files, or approve/merge.
+
+                      Use the GitHub tools to fetch the PR diff and changed
+                      files, then post ONE structured review comment covering:
+                        - Correctness bugs and edge cases
+                        - Security concerns
+                        - Maintainability / readability
+                        - Test coverage gaps
+                      Reference specific files and line numbers. If the PR looks
+                      good, say so briefly rather than inventing nits.
+
+                  # Defense-in-depth allowlist: read + comment only.
+                  # Read: local files, ripgrep, and read-only GitHub API calls.
+                  # Write surface is limited to posting PR/issue comments.
+                  # No Edit/Write/Bash(git ...)/create_or_update tools are listed,
+                  # so Claude cannot modify the tree even in-runner.
+                  claude_args: |
+                      --allowedTools "Read,Grep,Glob,mcp__github__get_pull_request,mcp__github__get_pull_request_files,mcp__github__get_pull_request_diff,mcp__github__list_pull_requests,mcp__github__get_issue,mcp__github__get_issue_comments,mcp__github__get_file_contents,mcp__github__search_code,mcp__github_comment__update_claude_comment"
+                      --max-turns 20