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.
npx skills add kensaurus/cursor-kenji --skill mobile-rn-performancegit clone --depth 1 https://github.com/kensaurus/cursor-kenjiWrote 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.
[](https://agentmods.dev/skills/kensaurus/cursor-kenji/mobile-rn-performance)<a href="https://agentmods.dev/skills/kensaurus/cursor-kenji/mobile-rn-performance"><img src="https://agentmods.dev/badge/skills/kensaurus/cursor-kenji/mobile-rn-performance/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.
<a href="https://agentmods.dev/skills/kensaurus/cursor-kenji/mobile-rn-performance"><img src="https://agentmods.dev/badge/skills/kensaurus/cursor-kenji/mobile-rn-performance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00059 | $0.01500 |
| Opus 5.5 | $0.00024 | $0.00600 |
| Sonnet 5.5 | $0.00012 | $0.00300 |
| Haiku 4.5 | $0.00006 | $0.00150 |
Grade A, and why
mobile-rn-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 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.
How it starts
The opening of the file, as written. The whole thing — 108 lines — stays where its author put it; the contents beside it link to each section on GitHub.
React Native Performance & Build
Degree of freedom: MIXED. Which category and fix [HIGH freedom]; measure
before/after, 16KB alignment, and upgrade-helper diffs
[LOW freedom — run exactly].
The performance, bundling, and upgrade layer for React Native / Expo.
mobile-rn-screenhandles screen layout and native feel; this skill handles speed, size, and version moves.Distilled from Callstack's React Native best-practices skill (MIT) and the Ultimate Guide to RN Optimization.
How to reason
- Measure — RN perf monitor / profiler numbers first
- Category — FPS, bundle, TTI, native, memory, or animation
- Fix — the profiled hotspot only
- Re-measure — before/after on a real low-end device
Worked example
Measure: feed scroll drops to 38fps; React profiler shows every row re-rendering. Category: FPS & re-renders — not "add memo everywhere". Fix:
FlashList+ stablekeyExtractor; animation stays on Reanimated shared values. Re-measure: 56fps on a low-end Android; no new storm on the changed screen.
Self-critique before reporting
- Not vibes — a number existed before the patch
- Hotspot only — no unprofiled memo/lazy spray
- Both platforms — Android measured; iOS-affecting native changes verified on macOS CI
- Right owner — layout / safe-area / touch feel →
mobile-rn-screen; on-device walk →mobile-emulator-test; hybrid axes →enhance-capacitor-ui
Diagnose first, then fix [HIGH freedom]
Never optimize blind. Identify the symptom, then apply the matching category. Measure before/after.
| Symptom | Category | Impact |
|---|---|---|
| Janky scroll/animation, dropped frames | FPS & re-renders | CRITICAL |
| Large download / install size | Bundle size | CRITICAL |
| Slow cold start (high TTI) | TTI / startup | HIGH |
| Slow native operations | Native performance | HIGH |
| Memory grows over time / crashes | Memory management | MED-HIGH |
| Choppy gestures/transitions | Animations | MEDIUM |
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.
- 1mo ago First seen · 108 lines · 59 tokens per session scan A e885ec4f0322
mobile-rn-performance is a skill published in the GitHub repository kensaurus/cursor-kenji (9 stars, last pushed 25d ago), licensed MIT. It adds 59 tokens to every session and 1,500 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 2026-09-03.
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