Persist compiler output between runs

Restore compatible compiler outputs and intermediate objects instead of recompiling unchanged inputs.

Prompt

Evaluate and apply this CI technique to my repository: Persist compiler output between runs.

Restore compatible compiler outputs and intermediate objects instead of recompiling unchanged inputs.

Read the technique and its source-backed company examples: https://starsling.dev/ci-playbooks/techniques/persist-compiler-cache.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.

View all playbooks

How companies used this technique

Read what each company changed and follow the original sources.

Cache the cross-compile producer’s objects

Codex's archive refactor moved the Windows ARM64 build onto a Windows x64 producer and turned on sccache for it, keying the producer's caches by the archive runner so the cross-compile reuses the Windows x64 cache.

sccache on for the Windows ARM64 archive producer Source

Use it when: One producer job compiles the same Rust or C++ inputs on every run before handing test binaries to native runners.
Before applying it: Compiler caches need the toolchain, target and flags in their identity, and trusted writers only. Cached compilation leaves native test execution in place.

Persist the compiler cache and warm it from the default branch

Ramp's CLI release workflow compiles the Python CLI to native binaries with Nuitka on every version tag. Ramp rooted Nuitka's caches (ccache on Linux and macOS, clcache on Windows) in the workspace through NUITKA_CACHE_DIR and saved them with actions/cache, keyed on the lockfile with restore prefixes. Caches are scoped per ref, so a new release tag starts from the default branch's caches and shares nothing with other tags; the workflow therefore also runs on every push to main to warm the cache; those runs build but skip packaging, artifact upload and the release jobs. A rerun of the same tag can also reuse that tag's own cache.

In the commit Release v0.2.26, the release workflow restores the Nuitka compiler cache on every build and warms it on each push to main. Source

The commit's workflow comments describe the change; the quote is from the diff. GitHub's cache rules let a run restore caches from its own ref and the default branch, so the quoted comment is narrower than that rule.

Use it when: A build job compiles the same native outputs from scratch on every run, and release builds run on tags.
Before applying it: A new tag build starts from the default branch's caches, so the warming run on main must use the same cache key prefix as the tag build.

How companies used this technique

Cache the cross-compile producer’s objects

Persist the compiler cache and warm it from the default branch

Related techniques

Cache package downloads and dependency stores

Bake stable dependencies into runner images

Cache the directories the build actually uses

Company Playbooks

Related guides

Cache workflow dependencies

Cut repeated test setup

Share setup steps across jobs

Optimize npm installs

Optimize pnpm installs