Parallel Scopes

By default, Mergify’s merge queue operates in serial mode: every pull request is tested on top of the previous one, forming a single ordered pipeline. This guarantees correctness but means unrelated changes wait for each other.

Parallel mode removes that constraint. When two pull requests touch different areas of the codebase — different scopes — Mergify tests and merges them independently, at the same time. Pull requests that do share a scope are still queued together so they are tested as a group, preventing semantic conflicts.

Isolated mode goes one step further. Every batch runs as a fully independent unit with no dependency on any other batch — even when their changes overlap. Scopes become optional: when set, Mergify groups similar pull requests into the same batch; when omitted, it batches by priority and arrival order. See Isolated Mode below.

In serial mode, every batch depends on the one before it. Even if PR #3 (docs) has nothing in common with PR #1 (api) or PR #2 (frontend), it still waits:

In parallel mode, Mergify groups pull requests by scope. Batches that share no scope run at the same time:

When scopes do overlap, Mergify preserves ordering within that scope to guarantee the changes are tested together:

Here PR #4 touches the api scope, just like PR #1 — so it must wait for PR #1 to merge first. Meanwhile PR #3 (docs) proceeds independently.

In isolated mode, there are no dependencies at all. Every batch runs on its own, even when two batches touch the same code, so an overlap like the one above never creates a wait:

Parallel mode requires two things: switching the queue mode and configuring scopes so Mergify knows which areas of the codebase each pull request touches.

Scopes can come from file patterns declared directly in .mergify.yml, or from an external build system (Nx, Bazel, Turborepo, …) via the gha-mergify-ci GitHub Action.

scopes:
  source:
    files:
      api:
        include:
          - services/api/**/*
      frontend:
        include:
          - apps/web/**/*
      docs:
        include:
          - docs/**/*

See Scopes for all configuration options and build-tool integrations.

Add mode: parallel under merge_queue:

merge_queue:
  mode: parallel
  max_parallel_checks: 5

scopes:
  source:
    files:
      api:
        include:
          - services/api/**/*
      frontend:
        include:
          - apps/web/**/*
      docs:
        include:
          - docs/**/*

queue_rules:
  - name: default
    batch_size: 3
    queue_conditions:
      - check-success = ci

The max_parallel_checks setting controls how many batches Mergify tests at the same time across all scope queues. Tune it to match your CI capacity.

Once parallel mode is active, the merge queue follows these steps whenever it processes pull requests:

1. Scope assignment. Each pull request is tagged with the scopes it affects, either automatically from file patterns or via an external upload.

2. Batch formation. Mergify groups pull requests that share exactly the same set of scopes into batches (respecting batch_size). Pull requests with different scopes form separate batches.

3. Dependency tracking. Batches that share at least one scope are linked as parent → child in a dependency graph. A child batch cannot merge until all its parents have merged.

4. Parallel execution. Batches with no shared scopes — and therefore no dependency — are tested by CI at the same time, up to max_parallel_checks.

5. Merge. As soon as a batch’s CI passes and all its parent batches are merged, Mergify merges the pull requests in that batch.

The failure handling works the same way as in serial mode: Mergify splits the failed batch and retests the parts to isolate the problematic pull request. See Handling Batch Failures for details.

Because batches in parallel mode are scoped, a failure in one scope queue does not block unrelated scope queues. Only batches that depend on the failed one (via shared scopes) are affected.

Parallel mode is built for the reality of monorepos: most pull requests are independent, but some do interact.

The net effect: pull requests merge faster when their scopes don’t collide, while pull requests that do collide are still tested in the right order to avoid semantic conflicts reaching your main branch.

Parallel mode keeps dependencies between batches that share a scope. Isolated mode drops them entirely: every batch is a self-contained unit that is tested and merged on its own, with no parent batch and no child batch. A failure in one batch never blocks any other.

Use isolated mode when your pull requests are genuinely independent and you want maximum throughput without maintaining a scope map — for example when each pull request targets its own service or package and you don’t need Mergify to serialize overlapping changes.

Set mode: isolated under merge_queue. Unlike parallel mode, scopes are optional:

merge_queue:
  mode: isolated
  max_parallel_checks: 5

queue_rules:
  - name: default
    batch_size: 5
    queue_conditions:
      - check-success = ci

How Mergify fills a batch depends on whether you configure scopes:

• With scopes. Mergify groups the most similar pull requests — those sharing the most scopes — into the same batch, using the same scope-aware batching as the other modes. This keeps related changes tested together and maximizes CI reuse.

• Without scopes. Mergify fills batches by queue priority and arrival order, up to batch_size.

Either way, the batches that result are fully independent. They run concurrently up to max_parallel_checks, and Mergify merges each one as soon as its own CI passes — there is never a parent batch to wait for.

Batch failure handling is the same as in the other modes: Mergify splits the failed batch and retests the parts to isolate the culprit. See Handling Batch Failures.

Parallel and isolated modes change how the queue operates. Some features that rely on strict single-queue ordering are not available:

• Scopes are required in parallel mode. You must configure scopes.source (either files or manual) so Mergify can tell which pull requests are independent. Isolated mode does not require scopes — see Isolated Mode.

• fast-forward merge is not supported. Because batches merge independently, Mergify needs to rebase them. Use merge or rebase as your merge_method.

• skip_intermediate_results is not available. This feature depends on the strict cumulative ordering of serial mode.

• partition_rules are not supported. Partitions rely on serial ordering; use scopes instead.

• Scopes: learn how to define and manage scopes for your repository.

• Batches: understand batch formation, sizing, and failure handling.

• Performance: tune your queue for the right balance of speed, cost, and reliability.

• Monorepo: broader guidance on using Mergify in monorepo setups.