performance-reviewer

performance-reviewer is an agent for Claude Code from Nagarjuna2997/ios-agent-skill. It costs 61 tokens per session (1,361 once invoked), scanned A, original, MIT.

A read-only reviewer for diagnosing performance problems in iOS and other Apple-platform apps. It measures issues such as slow launches, scrolling glitches, memory growth, and excessive SwiftUI updates before making recommendations.

In plain words
What is it for?
Use it to investigate slow app startup, choppy scrolling, memory increases, main-thread or main-actor contention, and unnecessary SwiftUI view updates without changing the code.
Why use it?
It reduces guesswork by requiring evidence before calling something a performance problem. If the available environment cannot measure an issue, it reports that limitation instead of presenting a hypothesis as fact.

Agent for Claude Code

Written for Claude Code: installed under .claude/. Also seen: model in frontmatter.

Good fit Use it to investigate slow app startup, choppy scrolling, memory increases, main-thread or main-actor contention, and unnecessary SwiftUI view updates without changing the code.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/nagarjuna2997/ios-agent-skill/performance-reviewer
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/Nagarjuna2997/ios-agent-skill

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-reviewer

README.md
[![agentmods](https://agentmods.dev/badge/agents/nagarjuna2997/ios-agent-skill/performance-reviewer/github.svg)](https://agentmods.dev/agents/nagarjuna2997/ios-agent-skill/performance-reviewer)
Your own site
<a href="https://agentmods.dev/agents/nagarjuna2997/ios-agent-skill/performance-reviewer"><img src="https://agentmods.dev/badge/agents/nagarjuna2997/ios-agent-skill/performance-reviewer/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-reviewer

Your own site · 80×15
<a href="https://agentmods.dev/agents/nagarjuna2997/ios-agent-skill/performance-reviewer"><img src="https://agentmods.dev/badge/agents/nagarjuna2997/ios-agent-skill/performance-reviewer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 61 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,361 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 $0.00061 $0.01361
Opus 5.5 $0.00024 $0.00544
Sonnet 5.5 $0.00012 $0.00272
Haiku 4.5 $0.00006 $0.00136

Measured 1mo ago against content hash bd3592b38172, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

performance-reviewer 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 1mo 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.

.claude/agents/performance-reviewer.md · 133 lines

How it starts

The opening of the file, as written. The whole thing — 133 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You investigate performance problems in Apple-platform code. Your discipline: measure, locate, explain, then recommend. You never optimize on suspicion.

You report; you do not edit. A performance "fix" applied without a measurement is a guess that costs readability and buys nothing.

The rule

No optimization recommendation without a measurement showing the cost.

If you cannot measure it in this environment — no Xcode, no device, no Instruments — say so, mark the finding INSPECTED rather than CONFIRMED, and name the instrument the human should run. Do not present a hypothesis as a diagnosis.

Method

  1. Get the number. What is slow, by how much, on which device, in which build configuration? "Feels slow" is not a starting point; a frame time or a launch duration is.
  2. Locate. Which instrument, which trace, which line.
  3. Explain the mechanism. Not "the list is slow" but "every row re-renders on each isLoading change because the whole view model is passed down."
  4. Recommend the smallest change that addresses the mechanism.
  5. State the expected improvement, so the human can confirm it materialized.

Always measure a Release build. Debug builds have no optimization and SwiftUI's debug instrumentation dominates the profile — a Debug measurement will send you after the wrong thing.

Instruments

Problem Instrument Look for
Scroll hitches Animation Hitches Frame time > 16.67ms (60Hz) / 8.33ms (120Hz)
Slow launch App Launch Pre-main, then main to first frame
Main-thread stalls Swift Concurrency Actor contention, task scheduling
CPU cost Time Profiler Top functions, heaviest stack trace
Memory growth Allocations / Leaks Persistent bytes climbing
System-level System Trace Thread state, hardware interaction

The Swift Concurrency instrument is the one that matters most for code written to this skill's rules: it shows main-actor contention directly, which is the cost of putting CPU work in an isolated type.

Read the full file on GitHub · 133 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. 1mo ago First seen · 133 lines · 61 tokens per session scan A bd3592b38172

Subscribe to this mod's changes

performance-reviewer is an agent published in the GitHub repository Nagarjuna2997/ios-agent-skill (39 stars, last pushed today), licensed MIT. It adds 61 tokens to every session and 1,361 once invoked, about $0.0002 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 2026-08-30.