Benchmark Xcode clean and incremental builds with repeatable inputs, timing summaries, and timestamped `.build-benchmark/` artifacts. Use when a developer wants a baseline, wants to compare before and after changes, asks to measure build performance, mentions build times, build duration, how long bu

Xcode Build Benchmark Use this skill to produce a repeatable Xcode build baseline before anyone tries to optimize build times. Core Rules Measure before recommending changes. Capture clean and incremental builds separately. Keep the command, destination, configuration, scheme, and warm up rules consistent across runs. Write a timestamped JSON artifact to .build benchmark/ . Do not change project files as part of benchmarking. Inputs To Collect Confirm or infer: workspace or project path scheme configuration destination whether the user wants simulator or device numbers whether a custom DerivedData path is needed If the project has both clean build and incremental build pain, benchmark both. That is the default. Worktree Considerations When benchmarking inside a git worktree, SPM packages with exclude: paths that reference gitignored directories (e.g., Snapshots ) will cause xcodebuild resolvePackageDependencies to crash. Create those missing directories before running any builds. Default Workflow 1. Normalize the build command and note every flag that affects caching or module reuse. 2. Run one warm up build if needed to validate that the command succeeds. 3. Run 3 clean builds. 4. If COMPILATION CACHE ENABLE CACHING = YES is detected, run 3 cached clean builds. These measure clean build time with a warm compilation cache the realistic scenario for branch switching, pulling changes, or Clean Build Folder. The script handles this automatically by building once to warm the cache, then deleting DerivedData (but not the compilation cache) before each measured run. Pass no cached clean to skip. 5. Run 3 zero change builds (build immediately after a successful build with no edits). This measures the fixed overhead floor: dependency computation, project description transfer, build description creation, script phases, codesigning, and validation. A zero change build that takes more than a few seconds indicates avoidable per build overhead. Use the default benchmark builds.py invocation (no touch file flag). 6. Optionally run 3 incremental builds with a file touch to measure a real edit rebuild loop. Use touch file path/to/SomeFile.swift to touch a representative source file before each build. 7. Save the raw results and summary into .build benchmark/ . 8. Report medians and spread, not just the single fastest run. Preferred Command Path Use the shared helper when possible: If you cannot use the helper script, run equivalent xcodebuild commands with showBuildTimingSummary and preserve the raw output. Required Output Return: clean build median, min, max cached clean build median, min, max (when COMPILATION CACHE ENABLE CACHING is enabled) zero change build median, min, max (fixed overhead floor) incremental build median, min, max (if touch file was used) biggest timing summary categories environment details that could affect comparisons path to the saved artifact If results are noisy, say so and recommend rerunning under calmer conditions. When To Stop Stop after measurement if the user only asked for benchmarking. If they want optimization guidance, hand off the artifact to the relevant specialist by reading its SKILL.md and applying its workflow to the same project context: [ xcode compilation analyzer ](../xcode compilation analyzer/SKILL.md) [ xcode project analyzer ](../xcode project analyzer/SKILL.md) [ spm build analysis ](../spm build analysis/SKILL.md) [ xcode build orchestrator ](../xcode build orchestrator/SKILL.md) for full orchestration Additional Resources For the benchmark contract, see [references/benchmarking workflow.md](references/benchmarking workflow.md) For the shared artifact format, see [references/benchmark artifacts.md](references/benchmark artifacts.md) For the JSON schema, see [schemas/build benchmark.schema.json](schemas/build benchmark.schema.json)

xcode-build-benchmark