--- title: "Split independent work off the longest job" description: "Run independent suites in parallel jobs when the overlap saves more than the repeated setup costs." url: https://starsling.dev/ci-playbooks/techniques/split-long-lanes canonicalUrl: https://starsling.dev/ci-playbooks/techniques/split-long-lanes --- # Split independent work off the longest job Run independent suites in parallel jobs when the overlap saves more than the repeated setup costs. ## How to choose an approach This technique currently has one documented company example. Validate its prerequisites, tradeoffs and original CI environment against your repository before adapting it. - **[Stripe](https://starsling.dev/ci-playbooks/stripe#split-long-lanes)**: Use it when Two independent suites run one after another in the job that holds up the pull request. Check before adopting: Each new job repeats setup and may queue. Keep every test variant and simulator version, and keep one stable required check that reports every job’s result. ## Apply this technique ````text Evaluate and apply this CI technique to my repository: Split independent work off the longest job. Run independent suites in parallel jobs when the overlap saves more than the repeated setup costs. Read the technique and its source-backed company examples: https://starsling.dev/ci-playbooks/techniques/split-long-lanes.md Inspect this repository’s CI workflows, build and test commands, dependencies, and recent run timings. Identify where this technique applies and explain the expected benefit using this repository’s evidence. Measure a baseline from recent comparable runs: elapsed time, queue time, runner minutes and failures where available. If data is unavailable, say what cannot be measured. Compare relevant company approaches, checking prerequisites, platform differences and tradeoffs. Rank applicable options by evidence, fit and measurable opportunity; do not present company results as predictions for this repo. Recommend the smallest safe change, show what checks and fallback paths remain, and ASK ME WHICH CHANGE TO APPROVE BEFORE EDITING ANY FILES. Only after approval, work on a new feature branch, make one reversible change, and open a reviewable pull request. Never merge or push to a default or protected branch. Keep required checks, test coverage, deployment and release behavior intact. Validate the change and compare equivalent runs where possible; report limitations and what should be monitored after merge. ```` ## How Stripe used this technique Read what Stripe changed and follow the original sources. ### Stripe: Split independent work off the longest job Stripe iOS split installation and integration tests into separate jobs, keeping all five installation variants together so they share setup. Earlier, it moved one measured slow test class into its own job. Evidence: Source PR/commit evidence The combined job took about 27 minutes; after the split, installation took about 11 to 12 minutes and integration about 13 minutes, running in parallel, in Stripe’s combined CI runs. ([Source](https://github.com/stripe/stripe-ios/pull/7334)) Use it when: Two independent suites run one after another in the job that holds up the pull request. Before applying it: Each new job repeats setup and may queue. Keep every test variant and simulator version, and keep one stable required check that reports every job’s result. [Read more in the Stripe playbook](https://starsling.dev/ci-playbooks/stripe#split-long-lanes) [Primary source](https://github.com/stripe/stripe-ios/pull/7334) ## CI optimization is continuous work. Apply this technique yourself, or use StarSling Runners for faster GitHub Actions and optional agent-driven optimization PRs, which teams on eligible paid plans can turn on. [Get self-improving CI](https://starsling.dev/products/runners) ## Related techniques ### [Balance test work across shards](https://starsling.dev/ci-playbooks/techniques/balance-test-shards) Use measured runtimes or smaller test files to reduce the slowest shard, which determines when the suite finishes. 4 implementations · 4 companies (Linear, OpenAI, Ramp, Stripe) ### [Split long test suites across runners](https://starsling.dev/ci-playbooks/techniques/shard-test-suites) Distribute a suite across CI jobs while keeping complete test discovery and collecting the results from every shard. 7 implementations · 7 companies (Anthropic, DoorDash, Mastra, OpenAI, Shopify, Spotify, Stripe) ### [Test supported runtimes concurrently](https://starsling.dev/ci-playbooks/techniques/matrix-by-supported-runtime) Give each target framework its own job that installs only what it needs. 1 implementation · 1 company (Stripe) ## Company Playbooks ### [Anthropic](https://starsling.dev/ci-playbooks/anthropic) Run only affected tests ### [DoorDash](https://starsling.dev/ci-playbooks/doordash) Run build and test in parallel, sharded across CI agents ### [Linear](https://starsling.dev/ci-playbooks/linear) Benchmark the same job on faster hardware ### [Mastra](https://starsling.dev/ci-playbooks/mastra) StarSling runners for the slowest test workflow ### [OpenAI](https://starsling.dev/ci-playbooks/openai) Rank CI fixes by the minutes they save ### [Ramp](https://starsling.dev/ci-playbooks/ramp) Move a CPU-bound test suite to a faster CPU ### [Shopify](https://starsling.dev/ci-playbooks/shopify) Let an agent iterate against one CI metric ### [Spotify](https://starsling.dev/ci-playbooks/spotify) Build arm64 on native arm64 runners ### [Stripe](https://starsling.dev/ci-playbooks/stripe) Run only the tests a change can reach ### [Uber](https://starsling.dev/ci-playbooks/uber) Build the merge-queue speculations most likely to be needed ## Related guides Implementation guides for this technique. ### [Shard tests across parallel jobs](https://starsling.dev/best-practices/github-actions/shard-tests) Split a long suite with a matrix and your test framework’s sharding support. ### [Cut repeated test setup](https://starsling.dev/best-practices/github-actions/cut-repeated-test-setup) Move shared fixture work out of individual test cases and keep necessary cleanup. ### [Diagnose slow tests in CI](https://starsling.dev/github-actions/problems/slow-tests) Check common causes in order and confirm each with workflow evidence. ### [Optimize Playwright tests](https://starsling.dev/github-actions/optimizations/optimize-playwright) Choose trace and video retention and install the browsers your suite uses. ### [Make Vitest run mode explicit](https://starsling.dev/github-actions/optimizations/optimize-vitest) Pin run mode to the test command and bound the job with a timeout. ### [Parallelize independent jobs](https://starsling.dev/github-actions/optimizations/parallelize-independent-jobs) Run independent validation lanes concurrently and keep genuine job dependencies.