Compare Generations

Quick Start

You'll typically receive two generation identifiers. Follow these steps:

1. Run tuist generate list --json to find generations on each branch.
2. Run tuist generate show <id> --json for both base and head generations.
3. Compare duration, status, and cache hit rates.
4. Summarize cache changes with root cause analysis.

Step 1: Resolve Generations

If base/head are generation IDs or dashboard URLs

Fetch each directly:

tuist generate show <base-id> --json
tuist generate show <head-id> --json

If base/head are branch names

List recent generations on each branch:

tuist generate list --git-branch <base-branch> --json --page-size 1
tuist generate list --git-branch <head-branch> --json --page-size 1

Then fetch full details with tuist generate 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.

Step 2: Compare Top-Level Metrics

After fetching both generations, compare:

Metric	What to check
duration	Flag if head is >10% slower
status	Flag if base succeeded but head failed
cacheable_targets	Note if target count changed
local_cache_target_hits	Compare local hit counts
remote_cache_target_hits	Compare remote hit counts
is_ci	Note if one is CI and the other local

Compute cache hit rates:

• Base: (local_hits + remote_hits) / cacheable_targets * 100
• Head: same formula
• Delta: head_rate - base_rate

Step 3: Analyze Cache Invalidation

If cache hit rate dropped, the key question is: which target(s) caused the invalidation cascade?