rn-debugging

A troubleshooting guide for React Native apps, which are mobile apps built with JavaScript and native phone code. It explains how to inspect app errors, device logs, screens, components, stored data, and network requests.

In plain words
What is it for?
Use it to check whether Metro is running, read JavaScript and native crash logs, inspect the current screen and component tree, examine app state, and review console or network activity.
Why use it?
It gives a structured way to find the cause of crashes, blank screens, connection problems, and failed requests instead of guessing.

Skill for Claude CodeCodex

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/lykhoyda/rn-dev-agent/rn-debugging
Any agent
npx skills add Lykhoyda/rn-dev-agent --skill rn-debugging
Clone the repo
git clone --depth 1 https://github.com/Lykhoyda/rn-dev-agent

Made for: Claude Code, Codex.

Per session 123 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,152 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 $0.00123 $0.03152
Opus 5 $0.00062 $0.01576
Sonnet 5 $0.00025 $0.00630
Haiku 4.5 $0.00012 $0.00315

Measured 2d ago against content hash e5585624e5ec, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

rn-debugging 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.

packages/claude-plugin/skills/rn-debugging/SKILL.md · 227 lines

How it starts

The opening of the file, as written. The whole thing — 227 lines — stays where its author put it; the contents beside it link to each section on GitHub.

rn-debugging — CDP Usage, Error Identification, and Connection Troubleshooting

How to diagnose problems in React Native apps using the CDP MCP server, native device logs, and bash tools.


CDP vs Bash Decision Table

What you need to know Tool Command / MCP call
Is Metro running? MCP cdp_status
Is app showing a crash (JS)? MCP cdp_error_log
Is app showing a crash (native)? MCP collect_logs(sources=["native_ios"]) or collect_logs(sources=["native_android"])
Unified JS + native logs? MCP collect_logs(sources=["js_console","native_ios"], durationMs=3000)
What screen is the user on? MCP cdp_navigation_state
What does the component render? MCP cdp_component_tree(filter="MyComponent")
What is in the store? MCP cdp_store_state(path="cart.items")
What API calls were made? MCP cdp_network_log(limit=10)
What did console.log output? MCP cdp_console_log(level="all")
Is there a RedBox overlay? MCP cdp_component_tree (auto-detects and warns)
Dismiss RedBox / toggle inspector MCP cdp_dev_settings(action="dismissRedBox")
Is Metro bundler alive? MCP cdp_status
Is a specific element on screen? MCP device_find(text="element") or Maestro assertVisible
Tap an element by text or ref MCP device_find(text="Login", action="click") or device_press(ref="@e3")
Fill a text input MCP device_fill(ref="@e5", text="hello")
What are all UI elements? MCP device_snapshot (cross-platform accessibility tree with @refs)
What are all UI elements' positions? bash adb shell uiautomator dump (Android only, raw XML)
Arbitrary runtime value MCP cdp_evaluate(expression="...")

Key rule: If cdp_error_log is empty but the app is visibly broken, the problem is native. CDP only sees JavaScript — check native logs as fallback.


Error Types Matrix

Error Type Where to Find It Tool
JS runtime error (throw, TypeError) cdp_error_log MCP
Unhandled promise rejection cdp_error_log MCP
Uncaught error overlay (RedBox) cdp_component_tree (APP_HAS_REDBOX warning) MCP
console.error() call cdp_console_log(level="error") MCP
Metro bundle syntax error cdp_metro_events MCP
Native crash (iOS) collect_logs(sources=["native_ios"], logLevel="error") MCP
Native crash (Android) collect_logs(sources=["native_android"], logLevel="error") MCP
Cross-layer crash diagnosis collect_logs(sources=["js_console","native_ios"], durationMs=3000, logLevel="error") MCP
Network failure cdp_network_log (look for status=0 or missing status) MCP

Read the full file on GitHub · 227 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. 2d ago First seen · 227 lines · 123 tokens per session scan A e5585624e5ec

Subscribe to this mod's changes

rn-debugging is a skill published in the GitHub repository Lykhoyda/rn-dev-agent (11 stars, last pushed 2d ago), licensed MIT. It adds 123 tokens to every session and 3,152 once invoked, about $0.0006 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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