Compare Builds
Quick Start
You'll typically receive two build identifiers (IDs, dashboard URLs, or branch names). Follow these steps:
- Run
tuist build list --jsonto find builds on each branch. - Run
tuist build show <build-id> --jsonfor both base and head builds. - Fetch sub-resource details: targets (
tuist build xcode target list <id> --json), issues (tuist build xcode issue list <id> --json), and cache tasks (tuist build xcode cache-task list <id> --json). - Compare duration, status, cache hit rates, and other metrics.
- Summarize regressions, improvements, and recommendations.
If only one identifier is provided, use the project's default branch as the baseline.
Step 1: Resolve Builds
If base/head are build IDs or dashboard URLs
Fetch each directly:
tuist build show <base-id> --json
tuist build show <head-id> --jsonIf base/head are branch names
List recent builds on each branch and pick the latest:
tuist build list --git-branch <base-branch> --json --page-size 1
tuist build list --git-branch <head-branch> --json --page-size 1Then fetch full details with tuist build show <id> --json.
Defaults
- If no base is provided, use the project's default branch (usually
main). - If no head is provided, detect the current git branch with
git rev-parse --abbrev-ref HEAD.
Step 2: Fetch Sub-Resource Details
After fetching both builds with tuist build show <id> --json, drill down into sub-resources for a deeper comparison.
Compare targets
tuist build xcode target list <base-id> --json
tuist build xcode target list <head-id> --jsonLook for targets that changed status (e.g., success to failure) or had significant duration changes.
Compare issues
tuist build xcode issue list <base-id> --json
tuist build xcode issue list <head-id> --jsonLook for new warnings or errors introduced in the head build.
Compare cache tasks
tuist build xcode cache-task list <base-id> --json
tuist build xcode cache-task list <head-id> --jsonIdentify which specific targets had cache misses or hits and whether that changed between builds.
Step 3: Compare Top-Level Metrics
After fetching both builds, compare:
| Metric | What to check |
|---|---|
duration | Flag if head is >10% slower than base |
status | Flag if base succeeded but head failed |
cacheable_tasks_count | Note if task count changed |
cacheable_task_local_hits_count | Compare local hit counts |
cacheable_task_remote_hits_count | Compare remote hit counts |
| Cache hit rate | (local_hits + remote_hits) / cacheable_tasks_count * 100 |
category | Note if one is clean and the other incremental (makes duration comparison less meaningful) |
scheme / configuration | Ensure both builds used the same scheme and configuration for a fair comparison |
Compute the cache miss delta: base_misses - head_misses. Positive means head has fewer misses (improvement). Negative means regression.
Step 4: Investigate Duration Regressions
If the head build is significantly slower:
- Check if the
categorydiffers (clean vs incremental builds are not directly comparable). - Check if cache hit rate dropped, which would explain longer builds.
- If both are incremental with similar cache rates, the regression is likely in compilation time.
Step 5: Investigate Cache Changes
Compare cache statistics:
- Hit rate dropped: Possible causes include dependency changes, build setting changes, or Xcode version updates.
- Hit rate improved: Likely due to better cache warming or fewer source changes.
- Task count changed: New targets added or removed.
Step 6: Check Build Context
Compare environment details:
xcode_versionandmacos_version: Different versions can affect build times and cache validity.is_ci: CI vs local builds may have different performance characteristics.git_branchandgit_commit_sha: Verify the builds are from the expected commits.
Summary Format
Produce a summary with:
- Overall verdict: Better, worse, or neutral compared to base.
- Duration: Absolute and percentage change.
- Cache hit rate: Change in hit rate with explanation.
- Status: Any status changes (pass to fail or vice versa).
- Environment: Note any environment differences that affect comparability.
- Recommendations: Actionable next steps based on findings.
Example:
Build Comparison: base (abc123 on main) vs head (def456 on feature-x)
Duration: 45.2s -> 62.8s (+39%) -- REGRESSION
Cache hit rate: 85% -> 72% (-13%) -- 8 new cache misses
Status: success -> success
Root cause: Cache hit rate dropped due to 8 targets with invalidated caches.
The dependency hash changed for FeatureModule, cascading to 7 downstream targets.
Recommendations:
- Investigate why FeatureModule's cache was invalidated
- Consider splitting large targets to reduce cascade impactDone Checklist
- Resolved both base and head builds
- Fetched sub-resource details (targets, issues, cache tasks)
- Compared duration, cache, and status metrics
- Identified root causes for any regressions
- Provided actionable recommendations