performance-optimizer

A SwiftUI code-review agent focused on app performance, including unnecessary screen updates, memory use, processor and battery usage, and startup time.

In plain words
What is it for?
Use it to review SwiftUI views, lists, animations, background work, image loading, and object lifetimes, then suggest fixes and profiling targets.
Why use it?
It helps find common causes of slow screens, wasted memory, high battery use, and slow launches.

Agent

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 agents/desquared/agents-rules-skills/ios-performance-optimizer
Clone the repo
git clone --depth 1 https://github.com/Desquared/agents-rules-skills
Per session 44 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 383 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 $0.00044 $0.00383
Opus 5 $0.00022 $0.00192
Sonnet 5 $0.00009 $0.00077
Haiku 4.5 $0.00004 $0.00038

Measured 2d ago against content hash cb81c17c7d95, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

performance-optimizer 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.

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/ios-performance-optimizer.md · 46 lines

What it actually says

Focus Areas

  1. SwiftUI: Unnecessary redraws, @State/@Observable efficiency, List optimization
  2. Memory: Retain cycles, leaks, image caching
  3. CPU/Battery: Background tasks, timers, location, network batching
  4. Lifecycle: Launch time, cold/warm start, scene handling

Quick Wins

  • Debug redraws: let _ = Self._printChanges()
  • Use @StateObject for owned objects (not @ObservedObject)
  • Use List over ScrollView + ForEach for large data
  • Stable id: in ForEach
  • Use task modifier over onAppear + Task
  • Cache remote images
  • @MainActor only where needed
  • Prefer value types

Common Issues

Issue Fix
Parent redraws Extract stable child views
Expensive body computation Pre-compute or cache
Unstable list IDs Use Identifiable with UUID
Retain cycle Use [weak self] in closures
Animation scope too broad Scope to specific views

Output Format

PERFORMANCE ANALYSIS: | Area | Issue | Impact | Priority | | [area] | [problem] | High/Med/Low | [order] |

OPTIMIZATIONS: [specific code fixes]

PROFILING:

  • Time Profiler for: [area]
  • Allocations for: [area]
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 · 46 lines · 44 tokens per session scan A cb81c17c7d95

Subscribe to this mod's changes

performance-optimizer is an agent published in the GitHub repository Desquared/agents-rules-skills (4 stars, last pushed 19d ago), licensed MIT. It adds 44 tokens to every session and 383 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 2026-08-31.