# Mobile Debug

> Diagnoses build and runtime failures across Flutter, native Android, native iOS, React Native and Kotlin Multiplatform. Covers pub/Dart, Gradle/AGP, Xcode/CocoaPods, Metro, KMP source sets and iOS frameworks, crashes and deep links. Use for failing builds, app launches, stack traces or /reis-mobile:debug.

- Skill: `wrsilva/mobile-debug` (Agent Skill, multi-file: 17 files)
- Install (CLI): `npx skillmds@latest add wrsilva/mobile-debug`
- Raw SKILL.md: https://api.skillmd.com/api/skills/wrsilva/mobile-debug/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- Author: wrsilva (https://skillmd.com/u/wrsilva)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/wrsilva/mobile-debug

---


# Mobile Debug

One debugging process for every mobile stack. This file holds how to find a cause; each platform's error signatures and fixes live in its reference.

## 1. Pick the reference

Choose by the stack **and** by the layer the error comes from — a Flutter or React Native build often fails inside Gradle or Xcode:

| The failure is in | Read |
|---|---|
| A Flutter app: pub, Dart compilation, generated code, widgets, runtime exceptions | [references/flutter.md](references/flutter.md) |
| Gradle, the Android build, logcat crashes or ANRs (native Android, or the `android/` folder of any app) | [references/android.md](references/android.md) |
| Xcode, signing, CocoaPods, Swift packages or iOS crash logs (native iOS, or the `ios/` folder of any app) | [references/ios.md](references/ios.md) |
| A React Native or Expo app: Metro, native modules, JavaScript errors | [references/react-native.md](references/react-native.md) |
| Kotlin Multiplatform compilation, source-set or framework integration | [references/kotlin-multiplatform.md](references/kotlin-multiplatform.md) |
| A deep link, App Link or Universal Link that opens the browser, the wrong screen or crashes (any stack) | [references/deep-links.md](references/deep-links.md) |

When `reis-mobile debug` (or `/reis-mobile:debug`) ran, its `area` line points at the layer: `gradle`, `manifest`, `proguard` → Android; `xcode`, `signing`, `cocoapods`, `spm` → iOS; `pub` → Flutter; `metro` → React Native.

## 2. Find the first real error

Build and crash logs bury the cause under cascading failures. Quote the line that starts the failure — the first `error:`, the `What went wrong` block, the top of the exception with its `Caused by` — not the final `BUILD FAILED` or the last frame. Ask for the full output when the user pasted only the end.

## 3. Collect versions before theorizing

Most build failures after an upgrade are toolchain mismatches. Read the versions that decide the behavior — the SDK and toolchain versions (the doctor report shows them), wrapper and lock files, build scripts, deployment targets — and quote them in the diagnosis. Check compatibility against the official tables named in the reference; do not state compatibility ranges from memory.

## 4. Reproduce safely

Read-only commands can run: version checks, dependency trees, `flutter doctor -v`, `./gradlew --version`, `pod --version`, `xcodebuild -version`. A build that only compiles can run when the user already ran it or agrees, since it takes time and writes build outputs.

## 5. Confirm the cause

Tie the cause to evidence: `file:line`, a version, a build setting or a log line. If two causes are plausible, say what evidence would separate them instead of picking one.

## 6. Propose, then wait

Answer with:

- **Cause** — one or two sentences, with the evidence.
- **Fix** — the minimal change, as a diff or exact commands, in order.
- **Side effects** — what else the fix changes: a higher minimum Android or iOS version, a Gradle or Kotlin upgrade that CI needs too, pods changing version.
- **Verify** — the command that failed, run again.

Do not edit files, upgrade dependencies or run commands that change the project, the caches or the machine — `flutter clean`, `pod install`, `pod repo update`, `npx expo prebuild --clean`, deleting `DerivedData`, `~/.gradle` caches or `node_modules` — until the user asks you to apply the fix. Then apply it, run the verification and report the result.