performance-review

performance-review is a skill for Claude Code, Codex from tmj-90/gaffer. It costs 93 tokens per session (1,226 once invoked), scanned A, original, Apache-2.0.

A checklist for reviewing code changes for measurable slowdowns and excess resource use. It looks at how often work runs and whether its cost grows with user or data size.

In plain words
What is it for?
It helps inspect request handlers, background jobs, database access, loops, rendering, memory use, and bundle size for issues such as N+1 queries, blocking calls, needless rerenders, and unbounded work.
Why use it?
Performance problems can hide in reasonable-looking code, such as one database query per item or an unbounded loop. This review separates concrete regressions from unmeasured style concerns.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit It helps inspect request handlers, background jobs, database access, loops, rendering, memory use, and bundle size for issues such as N+1 queries, blocking calls, needless rerenders, and unbounded work.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/tmj-90/gaffer/performance-review
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.

Any agent
npx skills add tmj-90/gaffer --skill performance-review
Clone the repo
git clone --depth 1 https://github.com/tmj-90/gaffer

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for performance-review

README.md
[![agentmods](https://agentmods.dev/badge/skills/tmj-90/gaffer/performance-review/github.svg)](https://agentmods.dev/skills/tmj-90/gaffer/performance-review)
Your own site
<a href="https://agentmods.dev/skills/tmj-90/gaffer/performance-review"><img src="https://agentmods.dev/badge/skills/tmj-90/gaffer/performance-review/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for performance-review

Your own site · 80×15
<a href="https://agentmods.dev/skills/tmj-90/gaffer/performance-review"><img src="https://agentmods.dev/badge/skills/tmj-90/gaffer/performance-review.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 93 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,226 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00093 $0.01226
Opus 5.5 $0.00037 $0.00490
Sonnet 5.5 $0.00019 $0.00245
Haiku 4.5 $0.00009 $0.00123

Measured 16d ago against content hash f94f5a29c007, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

performance-review 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 16d ago.

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.

runner/skills/performance-review/SKILL.md · 80 lines

How it starts

The opening of the file, as written. The whole thing — 80 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Performance review lens

Performance regressions ship because each looks reasonable alone: one more query in a loop, one more sequential await, one more import. For every new hot-path line ask: how many times does this run, what does each run cost, and what bounds it? A finding is a concrete defect only when it is unbounded (grows with input an outside party controls), stalls an async server's request path (a synchronous I/O call, an outbound call with no timeout), or measurably breaks a budget the repo or an AC states; everything else is a note. Write the arithmetic into every finding.

Steps

  1. Find the hot paths in the diff: request and job handlers, loops over collections whose size is not fixed, render functions, anything called per item or per request. Skip one-off setup unless it runs at startup of a hot service. Call search_lore for known hot spots, budgets and the expected data sizes.
  2. Count and cost each path against the checklist: "this query runs once per order on the page; a page holds up to 200 orders; that is 201 queries per request". Use the largest size the code allows, not the size in the test fixture.
  3. Check the bound. Is the collection capped (pagination, LIMIT, a max upload size, a validated array length)? If a user, tenant or upstream can make it arbitrarily large, the work and memory are unbounded.
  4. Check performance claims. A ticket whose AC promises a speedup or a latency target needs before/after numbers under stated conditions with repeated runs (the performance-profiling skill); without them that AC is unevidenced.
  5. Rate each finding. Blocking: unbounded work or memory reachable from input; an N+1 on a list path whose size is unbounded; a blocking call on the request path of an async server; a missing timeout on an outbound call in a request path; a budget the repo or an AC enforces being broken. Note: a bounded regression that breaks no stated budget, or an optimisation opportunity. Only blocking findings justify RECOMMEND CHANGES.
  6. Record each finding with record_ac_evidence (evidence_type: manual_note, with the arithmetic and the fix), then let the review-ticket verdict carry the result.

Read the full file on GitHub · 80 lines

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. 16d ago Changed · +10 lines f94f5a29c007
  2. 19d ago First seen · 70 lines · 93 tokens per session scan A 55df743d064a

Subscribe to this mod's changes

performance-review is a skill published in the GitHub repository tmj-90/gaffer (2 stars, last pushed 17d ago), licensed Apache-2.0. It adds 93 tokens to every session and 1,226 once invoked, about $0.0004 per session on Opus 5.5. 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 2026-09-28.

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