performance

performance is a skill for Claude Code from krzysztofsurdy/code-virtuoso. It costs 84 tokens per session (2,098 once invoked), scanned A, original, MIT.

A method for making software use fewer resources or respond faster, based on measurements rather than guesses. It covers profiling, which shows where time or memory is being spent, along with targeted changes and follow-up measurements.

In plain words
What is it for?
Use it to investigate slow applications, high latency, slow database queries, repeated database requests, memory use, caching, lazy loading, and connection settings.
Why use it?
It helps focus on real bottlenecks instead of making unnecessary changes. It also makes trade-offs visible, such as using more memory to reduce response time.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Part of the knowledge-virtuoso plugin — 15 skills shipped together

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/krzysztofsurdy/code-virtuoso/performance
Any agent
npx skills add krzysztofsurdy/code-virtuoso --skill performance
Clone the repo
git clone --depth 1 https://github.com/krzysztofsurdy/code-virtuoso

Made for: Claude Code.

Or install knowledge-virtuoso, the plugin that ships this one along with the rest of its 15 skills.

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

README.md
[![agentmods](https://agentmods.dev/badge/skills/krzysztofsurdy/code-virtuoso/performance.svg)](https://agentmods.dev/skills/krzysztofsurdy/code-virtuoso/performance)
Your own site
<a href="https://agentmods.dev/skills/krzysztofsurdy/code-virtuoso/performance"><img src="https://agentmods.dev/badge/skills/krzysztofsurdy/code-virtuoso/performance.svg" alt="Measured on agentmods" height="20"></a>
Per session 84 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,098 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 5.1 $0.00084 $0.02098
Opus 5 $0.00042 $0.01049
Sonnet 5 $0.00017 $0.00420
Haiku 4.5 $0.00008 $0.00210

Measured 6d ago against content hash d2173ab3aec0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

performance 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 6d 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.

skills/knowledge/performance/SKILL.md · 197 lines

How it starts

The opening of the file, as written. The whole thing — 197 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Performance Optimization

Performance work follows one rule above all others: measure before you change anything. Intuition about bottlenecks is wrong more often than it is right. Every optimization should start with profiling, produce a hypothesis, apply a targeted fix, and verify with another measurement.

Core Principles

Principle Meaning
Measure first Never optimize without profiling data - gut feelings about bottlenecks are unreliable
Optimize the critical path Focus on the code that runs most frequently or blocks user-visible latency
Set budgets Define acceptable latency, throughput, and resource usage before you start
Avoid premature optimization Readable, correct code first - optimize only when measurements show a real problem
Know your tradeoffs Every optimization trades something (memory for speed, complexity for throughput, freshness for latency)

Profiling and Benchmarking

Profiling identifies where time and resources are spent. Without it, you are guessing.

Types of Profiling

Type What It Reveals When to Use
CPU profiling Hot functions, call frequency, execution time distribution Slow request handling, high CPU usage
Memory profiling Allocation rates, heap size, object retention, leaks Growing memory usage, OOM errors, GC pressure
I/O profiling Disk reads/writes, network calls, blocking waits Slow file operations, external service latency
Database profiling Query execution time, query count per request, slow queries High DB load, N+1 patterns, missing indexes

The Profiling Workflow

  1. Baseline - Capture metrics under normal conditions before any changes
  2. Identify - Find the hotspot consuming the most time or resources
  3. Hypothesize - Form a specific theory about why it is slow
  4. Fix - Apply a single, targeted change
  5. Verify - Measure again to confirm improvement and check for regressions

Read the full file on GitHub · 197 lines

Files

What ships with it

3 files 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. 6d ago First seen · 197 lines · 84 tokens per session scan A d2173ab3aec0

Subscribe to this mod's changes

performance is a skill published in the GitHub repository krzysztofsurdy/code-virtuoso (20 stars, last pushed 3mo ago), licensed MIT. It adds 84 tokens to every session and 2,098 once invoked, about $0.0004 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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