auto-merge

name	auto-merge
description	Auto-merge a PR after it is marked ready-for-review, if the change is small, non-disruptive, and all checks pass.
license	Apache-2.0
metadata	{"audience":"autonomous-agents"}

Auto-merge

Merge a PR that was just promoted from draft to ready-for-review, only when the change is small, non-disruptive, and every required check is green. This skill is the natural successor to mark-pr-ready.

When to load this skill

Load after the mark-pr-ready skill has run (or after a pull_request.ready_for_review event). Do not load it for PRs that were created as ready-for-review from the start — only for PRs that transitioned from draft.

Preconditions (all must be true)

1. The PR is open and marked ready for review (not draft).
2. The PR targets the repo's default branch.
3. All CI checks have completed and passed.
4. The diff is small and non-disruptive (see size gate below).
5. No reviewer has requested changes.
6. No unresolved review threads.

If any precondition fails, stop — do not merge. Post a comment explaining which precondition was not met.

Size gate

Classify the PR as "small and non-disruptive" only when all of these hold:

• Total lines changed (additions + deletions) ≤ 150.
• No more than 5 files changed.
• No changes to CI/CD configuration (.github/workflows/, Dockerfile, docker-compose*, Makefile, Justfile, Terraform *.tf).
• No changes to dependency lockfiles (bun.lock, package-lock.json, yarn.lock, pnpm-lock.yaml, Cargo.lock, go.sum).
• No database migrations or schema changes.
• No changes to authentication, authorization, or secrets handling.
• No deletions of public API surface (exported functions, REST endpoints, GraphQL types).

If the PR exceeds the size gate, stop. Post a comment noting the PR needs human review and list which criteria it exceeded.

Workflow

1. Verify PR state and target branch:

   PR_JSON=$(gh pr view <N> --json state,isDraft,baseRefName)
   STATE=$(echo "$PR_JSON" | jq -r '.state')
   IS_DRAFT=$(echo "$PR_JSON" | jq -r '.isDraft')
   BASE=$(echo "$PR_JSON" | jq -r '.baseRefName')
   DEFAULT_BRANCH=$(gh repo view --json defaultBranchRef --jq .defaultBranchRef.name)
   

   • Expect STATE=OPEN, IS_DRAFT=false. If draft or closed, stop.
   • Expect BASE == DEFAULT_BRANCH. If the PR targets a release or other protected branch, stop — those need human review.

2. Verify all checks pass:

   CHECKS=$(gh pr view <N> --json statusCheckRollup \
     --jq '.statusCheckRollup')
   

   For each check, inspect status and conclusion:

   • If any check has status other than "COMPLETED" (e.g. "QUEUED", "IN_PROGRESS", "PENDING"), stop — checks haven't finished yet. Post a comment noting which checks are still running.
   • If any completed check has conclusion other than "SUCCESS", "SKIPPED", or "NEUTRAL", stop — checks are failing. Post a comment listing the failing checks.

   Quick jq filter for non-passing completed checks:

   FAILING=$(echo "$CHECKS" | jq '[.[] | select(
     .status == "COMPLETED" and
     .conclusion != "SUCCESS" and
     .conclusion != "SKIPPED" and
     .conclusion != "NEUTRAL"
   )]')
   

   Quick jq filter for still-running checks:

   PENDING=$(echo "$CHECKS" | jq '[.[] | select(.status != "COMPLETED")]')
   

3. Evaluate the size gate:

   PR_DATA=$(gh pr view <N> --json additions,deletions,files)
   ADDITIONS=$(echo "$PR_DATA" | jq '.additions')
   DELETIONS=$(echo "$PR_DATA" | jq '.deletions')
   TOTAL=$((ADDITIONS + DELETIONS))
   FILES_CHANGED=$(echo "$PR_DATA" | jq '.files | length')
   

   Check each criterion listed in the size gate section. Inspect the file list for CI/CD, lockfile, migration, auth, or public API changes:

   echo "$PR_DATA" | jq -r '.files[].path'
   

4. Check for review objections and unresolved threads:

   CHANGES_REQUESTED=$(gh pr view <N> --json reviews \
     --jq '[.reviews[] | select(.state == "CHANGES_REQUESTED")] | length')
   

   If CHANGES_REQUESTED > 0, stop — a reviewer has requested changes.

   Check for unresolved review threads via the GraphQL API:

   UNRESOLVED=$(gh api graphql -f query='
     query($owner: String!, $repo: String!, $pr: Int!) {
       repository(owner: $owner, name: $repo) {
         pullRequest(number: $pr) {
           reviewThreads(first: 100) {
             nodes { isResolved }
           }
         }
       }
     }' -f owner=<OWNER> -f repo=<REPO> -F pr=<N> \
     --jq '[.data.repository.pullRequest.reviewThreads.nodes[] | select(.isResolved == false)] | length')
   

   If UNRESOLVED > 0, stop — there are unresolved review threads.

5. Merge:

   gh pr merge <N> --squash --auto --delete-branch
   

   Use --squash to keep the main branch history clean. Use --auto so GitHub waits for branch protection rules. Use --delete-branch to clean up the feature branch.

6. Post a short comment confirming the merge was enabled. Mention the total diff size and that all checks passed. Write it naturally — vary the wording, don't use a canned phrase.

When NOT to merge

• The PR has "CHANGES_REQUESTED" reviews.
• The PR has unresolved review threads.
• The PR modifies security-sensitive code.
• The PR exceeds the size gate.
• Any required check is not green.
• Any check is still running (not yet completed).
• The PR targets a branch other than the repo's default branch.

In all these cases, leave a comment explaining why auto-merge was skipped, and let a human decide.

Notes

• This skill should be loaded by the coordinator after mark-pr-ready completes, or in response to a pull_request.ready_for_review webhook.
• The --auto flag on gh pr merge respects branch protection rules. If the repo requires approvals, the merge will wait until those are satisfied.
• Never force-merge or bypass branch protection.