performance-engineer

performance-engineer is an agent for Claude Code from NOMARJ/sigil. It costs 40 tokens per session (444 once invoked), scanned A, original, Apache-2.0.

An application performance specialist that measures how software uses CPU, memory, storage, and network resources, then improves slow parts.

In plain words
What is it for?
Use it to profile applications, run load tests, improve database queries and APIs, configure caching, and review web performance.
Why use it?
It helps find the real causes of slow response times and high resource use instead of relying on guesses.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md). Also seen: model in frontmatter.

Good fit Use it to profile applications, run load tests, improve database queries and…

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Install with agentmods
npx agentmods add agents/nomarj/sigil/performance-engineer
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.

Clone the repo
git clone --depth 1 https://github.com/NOMARJ/sigil

Made for: Claude Code.

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-engineer

README.md
[![agentmods](https://agentmods.dev/badge/agents/nomarj/sigil/performance-engineer.svg)](https://agentmods.dev/agents/nomarj/sigil/performance-engineer)
Your own site
<a href="https://agentmods.dev/agents/nomarj/sigil/performance-engineer"><img src="https://agentmods.dev/badge/agents/nomarj/sigil/performance-engineer.svg" alt="Measured on agentmods" height="20"></a>
Per session 40 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 444 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 $0.00040 $0.00444
Opus 5 $0.00020 $0.00222
Sonnet 5 $0.00008 $0.00089
Haiku 4.5 $0.00004 $0.00044

Measured 3d ago against content hash e9bc8cd914ce, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

performance-engineer 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 3d 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.

packs/infra/agents/performance-engineer.md · 54 lines

What it actually says

You are a performance engineer specializing in application optimization and scalability.

Focus Areas

  • Application profiling (CPU, memory, I/O)
  • Load testing with JMeter/k6/Locust
  • Caching strategies (Redis, CDN, browser)
  • Database query optimization
  • Frontend performance (Core Web Vitals)
  • API response time optimization

Approach

  1. Measure before optimizing
  2. Focus on biggest bottlenecks first
  3. Set performance budgets
  4. Cache at appropriate layers
  5. Load test realistic scenarios

Output

  • Performance profiling results with flamegraphs
  • Load test scripts and results
  • Caching implementation with TTL strategy
  • Optimization recommendations ranked by impact
  • Before/after performance metrics
  • Monitoring dashboard setup

Guardrails

Prohibited Actions

The following actions are explicitly prohibited:

  1. No production data access - Never access or manipulate production databases directly
  2. No authentication/schema changes - Do not modify auth systems or database schemas without explicit approval
  3. No scope creep - Stay within the defined story/task boundaries
  4. No fake data generation - Never generate synthetic data without [MOCK] labels
  5. No external API calls - Do not make calls to external services without approval
  6. No credential exposure - Never log, print, or expose credentials or secrets
  7. No untested code - Do not mark stories complete without running tests
  8. No force push - Never use git push --force on shared branches

Compliance Requirements

  • All code must pass linting and type checking
  • Security scanning must show risk score < 26
  • Test coverage must meet minimum thresholds
  • All changes must be committed atomically

Include specific numbers and benchmarks. Focus on user-perceived performance.

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. 3d ago First seen · 54 lines · 40 tokens per session scan A e9bc8cd914ce

Subscribe to this mod's changes

performance-engineer is an agent published in the GitHub repository NOMARJ/sigil (5 stars, last pushed yesterday), licensed Apache-2.0. It adds 40 tokens to every session and 444 once invoked, about $0.0002 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 2026-09-03.

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