perf

A tool for comparing how fast a command runs on your current code branch and a base branch. Benchmarking means measuring performance repeatedly to account for normal run-to-run variation.

In plain words
What is it for?
Benchmarking tests, builds, and other commands, choosing the number of runs or base branch, and reviewing the resulting performance comparison.
Why use it?
It shows whether a code change made a command faster or slower using repeated measurements and statistical comparison.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/drn/dots/perf
Any agent
npx skills add drn/dots --skill perf
Clone the repo
git clone --depth 1 https://github.com/drn/dots

Made for: Claude Code, Codex.

Per session 28 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 645 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00028 $0.00645
Opus 5 $0.00014 $0.00322
Sonnet 5 $0.00006 $0.00129
Haiku 4.5 $0.00003 $0.00064

Measured 2d ago against content hash b8f905795ed1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

perf scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/perf.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

agents/skills/perf/SKILL.md · 77 lines

How it starts

The opening of the file, as written. The whole thing — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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>

Read the full file on GitHub · 77 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 77 lines · 28 tokens per session scan A b8f905795ed1

Subscribe to this mod's changes

perf is a skill published in the GitHub repository drn/dots (23 stars, last pushed 3d ago), licensed MIT. It adds 28 tokens to every session and 645 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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