Parallel Checks

Parallel Checks let Mergify test multiple queued pull requests together so you ship faster. Mergify creates temporary draft PRs that represent cumulative merges (PR#1), (PR#1+PR#2), (PR#1+PR#2+PR#3), runs CI on them in parallel, then merges the original PRs once checks pass.

Mergify groups PRs by their position in the queue and the max_parallel_checks value. It creates draft PRs that speculatively combine changes and runs your CI on each in parallel. For example, with PR #1–#5 and max_parallel_checks: 3, Mergify creates:

• Draft #1: PR #1
• Draft #2: PR #1 + PR #2
• Draft #3: PR #1 + PR #2 + PR #3

This validates the combined outcome ahead of time against your queue_rules. If a draft fails, Mergify removes the culprit PR from the queue and continues with the rest.

The result: fewer head-of-line stalls, faster merges, and earlier detection of incompatibilities.

Set merge_queue.max_parallel_checks to control how many speculative checks run at once:

merge_queue:
  max_parallel_checks: 3

This example runs up to 3 speculative checks simultaneously. Tune this number to match your CI capacity and typical PR size/complexity.

Parallel Checks adapt automatically as your code and rules evolve:

• Failed checks: Mergify removes the failing PR and continues with the rest.

• PR or rule changes: affected PRs are re-evaluated and re-embarked in order.

• Base branch updates: checks restart on the new base; configurable via reset_on_external_merge — see Lifecycle: Base Branch Updates.

Mergify runs checks directly on the original pull request (instead of using temporary draft PRs) only when of the following are true:

• queue_rules[*].batch_size = 1

• merge_queue.max_parallel_checks = 1

• No two‑step CI is configured (i.e., no separate merge_conditions beyond queue_conditions in your queue rules)

• Optionally, set update_bot_account to avoid in‑place updates blocked by GitHub for security reasons (e.g., PRs from forks that modify workflows, or PRs opened by other bots)

Example configuration enabling in‑place checks:

merge_queue:
  max_parallel_checks: 1

queue_rules:
  - name: default
    batch_size: 1
    # use a single set of checks (no two‑step split between queue vs merge)
    queue_conditions:
      - check-success = ci
    update_bot_account: my-org-bot

Parallel checks operate by creating temporary pull requests, which merge multiple PRs with the base branch. This process requires the branch protection setting Require branches to be up to date before merging to be disabled.

This does not mean that Mergify will test outdated PRs, but it will merge the original pull requests once its parallel checks is finished. The original PR won’t be up-to-date according to GitHub, which means using this setting would block the merge.

Adjust max_parallel_checks to balance throughput and CI usage. Higher values increase concurrency; choose a value your CI can handle reliably. For deeper guidance and trade‑offs (including batching), see Merge queue performance.