| name | analyze-ci-speed |
| description | Analyze compilation time and test durations from CI logs. Use when the user asks about slow builds, slow tests, or wants to optimize CI time. |
Analyze CI Speed
Analyze compilation time and test durations from CI logs to identify optimization opportunities.
Prerequisites
gh CLI installed and authenticated (gh auth login)
Instructions
Step 1: Get Recent Workflow Runs
Get latest successful run from dev branch:
gh run list --workflow=Rust --branch=dev --limit=1 --status=success --json databaseId,conclusion,headSha,createdAt
Step 2: Download Test Job Logs
Get test jobs (nextest, nextest_all_features, coverage):
gh run view <run-id> --json jobs --jq '.jobs[] | select(.name == "nextest" or .name == "nextest_all_features" or .name == "coverage") | {id: .databaseId, name: .name}'
Download logs, stripping ANSI codes:
mkdir -p ci-logs/speed-analysis/
gh run view --job <job-id> --log | perl -pe 's/\e\[[0-9;]*m//g' > ci-logs/speed-analysis/<job_name>.log
Step 3: Extract Compilation Time
Search for cargo build summary in logs:
Finished ... in Xm Ys
Also look for incremental compilation info and cache hit rates.
Step 4: Extract Test Durations
Parse nextest output for test durations. Look for patterns like:
PASS [ 1.234s] crate_name::module::test_name
SLOW [ 15.678s] crate_name::module::slow_test
Extract all test durations and sort to find top 10 slowest tests.
Step 5: Analyze and Report
Provide summary:
- Total compilation time
- Top 10 slowest tests with durations
- Any tests marked as SLOW by nextest
- Recommendations:
- Tests that could be optimized or parallelized
- Crates with long compilation times
- Potential for better caching
Notes
- Run on successful builds to get complete timing data
- Compare across runs to identify regressions
