--- title: "Build on one machine when the long pole leaves it idle" description: "Put the compile steps that waited on separate machines onto the box the long pole underuses." url: https://starsling.dev/ci-playbooks/techniques/one-machine-build canonicalUrl: https://starsling.dev/ci-playbooks/techniques/one-machine-build --- # Build on one machine when the long pole leaves it idle Put the compile steps that waited on separate machines onto the box the long pole underuses. ## 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. - **[Anthropic](https://starsling.dev/ci-playbooks/anthropic#one-machine-build)**: Use it when Two build jobs run on separate machines and one of them leaves its machine mostly idle while the other sets the critical path. Check before adopting: The combined job runs on a machine with the cores and memory both compiles need. ## Apply this technique ````text Evaluate and apply this CI technique to my repository: Build on one machine when the long pole leaves it idle. Put the compile steps that waited on separate machines onto the box the long pole underuses. Read the technique and its source-backed company examples: https://starsling.dev/ci-playbooks/techniques/one-machine-build.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 Anthropic used this technique Read what Anthropic changed and follow the original sources. ### Anthropic: Build on one machine when the long pole leaves it idle Bun's Rust build is the long pole and leaves its machine underused, so Bun builds C++, Rust and the link in one step on one machine. The C++ compile overlaps cargo there, and the separate C++ build agent and its archive download are gone. Evidence: Single-run demonstration 26 to 13 build agents per build and about 93 to 69 agent-minutes, with one r8g.4xlarge build step replacing the c8g.4xlarge C++ and r8g.2xlarge build agents; every ThinLTO lane 23 to 43 seconds faster than the old build step alone (one build per lane), and the non-LTO lanes flat to about a minute slower. ([Source](https://github.com/oven-sh/bun/pull/37733)) Use it when: Two build jobs run on separate machines and one of them leaves its machine mostly idle while the other sets the critical path. Before applying it: The combined job runs on a machine with the cores and memory both compiles need. [Read more in the Anthropic playbook](https://starsling.dev/ci-playbooks/anthropic#one-machine-build) [Primary source](https://github.com/oven-sh/bun/pull/37733) ## 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) ## 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