xcode-build-strategist

Xcode Build Strategist

Entry point for end-to-end Xcode build optimization. Phase 1 recommends only; Phase 2 executes only after explicit approval.

Non-Negotiables

• Wall-clock wait time is the primary metric.
• Benchmark before changing project/source/package/script files.
• Preserve evidence in .build-benchmark/.
• Do not implement without explicit developer approval.
• Re-benchmark approved changes and report deltas.

Phase 1: Analyze

1. Resolve project/workspace, scheme, configuration, destination, and pain point. If both workspace and project exist, prefer the project unless the workspace is required.
2. Run or reuse a fresh baseline:

   python3 ../../shared/build-optimization/scripts/benchmark_builds.py \
     --project App.xcodeproj --scheme MyApp --configuration Debug \
     --destination "platform=iOS Simulator,name=<latest available iPhone simulator>,OS=latest" \
     --output-dir .build-benchmark
   

   Add --touch-file path/to/File.swift for real incremental rebuilds.
3. Verify artifact quality: non-empty timing_summary_categories; cached_clean runs when COMPILATION_CACHE_ENABLE_CACHING=YES; variance noted when max-min exceeds 20% of median.
4. If incremental builds are the pain and Xcode 16.4+ is available, recommend Task Backtraces and include any evidence.
5. Decide whether compile work is on the critical path. If category totals are 2x+ wall-clock median, many fixes reduce CPU work but not wait time.
6. Run relevant specialists:
   • xcode-compile-profiler
   • xcode-project-auditor
   • swiftpm-build-inspector
7. Generate .build-benchmark/optimization-plan.md:

   python3 scripts/generate_optimization_report.py \
     --benchmark .build-benchmark/<artifact>.json \
     --project-path App.xcodeproj \
     --diagnostics .build-benchmark/<diagnostics>.json \
     --output .build-benchmark/optimization-plan.md
   

8. Stop and ask the developer to approve checklist items.

Phase 2: Execute

After approval, read checked items from .build-benchmark/optimization-plan.md, delegate to xcode-build-tuner, append verification medians/deltas to the plan, and report before/after results.

Prioritization

• Rank by likely wall-clock savings for the user's primary pain: clean, cached clean, incremental, or CI.
• Serial bottlenecks such as PhaseScriptExecution, CompileAssetCatalog, CodeSign, planning, or emit-module work can outrank individual Swift file hotspots.
• Source-level compile fixes should not outrank project/graph/config fixes unless evidence says they block wall-clock.
• Every recommendation must include expected wait-time impact, evidence, affected files/settings, and risk.

Use these impact phrases:

• "Expected to reduce your [clean/incremental] build by approximately X seconds."
• "Reduces parallel compile work but is unlikely to reduce build wait time because other tasks take equally long."
• "Impact on wait time is uncertain; re-benchmark after applying."
• "No wait-time improvement expected. The benefit is [deterministic builds/faster branch switching/reduced CI cost]."
• For COMPILATION_CACHE_ENABLE_CACHING: "Measured 5-14% faster clean builds across tested projects; benefits compound with persistent DerivedData."

Destination Notes

For iOS simulator benchmarks, resolve an installed iPhone/iOS pair first and prefer OS=latest when accepted. For macOS use --destination "platform=macOS". For watchOS/tvOS use an installed simulator. If local runtime inspection fails, ask or note the fallback.

Report

Lead with wall-clock before/after. Include baseline/post medians, absolute and percentage deltas, changes made or intentionally skipped, confidence/noise notes, and a plain warning when workload improved but wait time did not.

References: references/orchestration-report-template.md, ../../shared/build-optimization/references/benchmark-artifacts.md, recommendation-format.md, and build-settings-best-practices.md.