Perf

Performance Benchmark

Run a command multiple times on the current branch and the base branch, then compare with statistical analysis.

Arguments

• $ARGUMENTS - Required: the command to benchmark (e.g., "go test -bench=. ./pkg/..." or "npm run build"). Optional: --runs <count> for number of runs (default 5), --base <ref> to override base branch.

Context

• Current branch: !git branch --show-current
• Base ref: !git branch -r 2>/dev/null | grep -oE 'origin/(main|master)' | head -1
• Git status: !git status --short

Your task

Run before/after benchmarks comparing the current branch against the base branch.

Step 1: Parse arguments and run the benchmark script

Extract the benchmark command and optional flags (--runs N, --base <ref>) from $ARGUMENTS.

IF no command is provided, ask: "What command should I benchmark?"

Resolve the script path — use the first that exists:

1. ~/.claude/skills/perf/scripts/perf.sh (deployed via symlink)
2. agents/skills/perf/scripts/perf.sh (repo-relative, for development/workspaces)

bash <script-path> "<command>" [--runs N] [--base <ref>]

Handle the exit code:

• Exit 0 — Format the output as the report below and show it as your final response.
• Exit 1 — Report the error from stderr.
• Exit 2 — Report: "Benchmark command failed. Verify the command works: <command>"

Step 2: Format the report

Parse the script's structured output and present it as:

## Benchmark Results

**Command:** `<command>`
**Runs:** <N> (+ 1 warmup)

### Timing

| Metric | Base (<ref>) | Current (<branch>) | Delta |
|--------|-------------|-------------------|-------|
| Min | <X>s | <Y>s | <diff> |
| Max | <X>s | <Y>s | <diff> |
| Mean | <X>s | <Y>s | <diff> |
| Median | <X>s | <Y>s | <diff> |
| Stddev | <X>s | <Y>s | — |

### Raw Data

**Base:** <comma-separated times>
**Current:** <comma-separated times>

### Verdict: <REGRESSION / IMPROVEMENT / NEUTRAL>

<1-2 sentence explanation>

If the script output includes a high-variance warning, append it after the verdict.