Keep unrelated environment changes out of cache keys

Include inputs that can change the output while excluding branch identity and unrelated environment churn.

Prompt

Evaluate and apply this CI technique to my repository: Keep unrelated environment changes out of cache keys.

Include inputs that can change the output while excluding branch identity and unrelated environment churn.

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

Keep runtime API keys out of unrelated build hashes

The build task stopped hashing RAPID_API_KEY and ANTHROPIC_API_KEY, two task-level env entries. The transferable step is proving that the build reads no runtime-only credentials.

Use it when: Task hashes change with secrets that are consumed only when the application runs.
Before applying it: Keep credentials used by build-time code generation or embedded configuration. Review secret availability separately from cache hashing.

Remove branch identity from content cache keys

A branch-name global environment variable caused different keys between Prebuild and workflow_run consumers. Mastra removed this artificial cache scope.

Use it when: Identical source and tool inputs miss cache when jobs see different GitHub event environments.
Before applying it: Only remove variables proven irrelevant to output. Cache correctness still requires all output-affecting configuration and secure write permissions.

Remove unrelated environment churn from cache inputs

Codex traced different remote cache keys for the same source tree to an unrelated tool version in the hosted Windows PATH. It now computes an explicit PATH in PowerShell and passes it to all three Bazel environments, keeping the tools the build uses.

Bazel actions see one explicit PATH across all three environments Source

Use it when: Identical source trees miss remote build caches after a runner image update.
Before applying it: A PATH allow-list can hide a required tool. Keep real tool versions in the cache inputs so a toolchain change still invalidates results.

How companies used this technique

Keep runtime API keys out of unrelated build hashes

Remove branch identity from content cache keys

Remove unrelated environment churn from cache inputs

Related techniques

Remove caches that cost more than they save

Bake stable dependencies into runner images

Cache package downloads and dependency stores

Company Playbooks

Related guides

Cache workflow dependencies

Cut repeated test setup

Share setup steps across jobs

Optimize npm installs

Optimize pnpm installs