---
title: "Scope capacities for build-tool scopes, patterns and serial queues"
date: 2026-10-28
tags:
  - "Merge Queue"
description: "Give a capacity to the scopes Bazel, Pants or Turborepo report, cap every scope a pattern such as `@acme/*` matches, and use scope capacities in a serial queue."
---

`scopes.capacities` only accepted letters, digits, `-` and `_` in its keys, so the scope names Bazel (`//lib/core`), Pants (`lib/util`) and Turborepo (`@acme/web`) report could not be given a capacity. A capacity key now accepts any scope name you send through the scopes API.

A key can also be a glob pattern, such as `//lib/**` or `@acme/*`. Every scope it matches gets its own capacity, so a whole family of lanes can be capped without listing each one. A key naming the scope exactly wins over a pattern, the lowest capacity applies when several patterns match, and `default_capacity` still covers every scope no key matches.

Scope capacities also work in a serial queue, the default mode, which used to refuse them. A serial queue still runs up to `max_parallel_checks` speculative checks, so you can keep an expensive scope, such as an end-to-end suite, to one check at a time while the rest of the queue uses the other slots. A pull request whose scope is full waits for a slot there while later pull requests that fit go ahead, and it is still tested on top of everything that merges before it.