kotlin-concurrency-expert

What the source does

• FilesystemNone observedNo reads or writes in the source
• NetworkNone observedNo outbound calls in the source
• ShellNone observedNo commands run in the source
• DependenciesPinnedNothing floats
• SecretsNone foundNo keys in source

Five audit layers

Gates applied: no behavioural pass.

Audit 0.4.1 · source sha 4bc96bf96aac · 31 Oct 2026Report an issue or request a re-scan

• Publishernew-silvermoon GitHub userOwner of the repository this skill is read from
• Source foldernew-silvermoon/awesome-android-agent-skills/.github/skills/concurrency_and_networking/kotlin-concurrency-expertThe exact folder we audited
• LicenceApache-2.0As the repository states it
• Commit pinned for this verdict4bc96bf96aacA new audit runs when the source changes
• Repository statusNot archivedLast push 95 days ago
• Sandboxed runNot runSkills are read, not executed; layer L4 is skipped

Its description: Kotlin Coroutines review and remediation for Android. Use when asked to review concurrency usage, fix coroutine-related bugs, improve thread safety, or resolve lifecycle issues in Kotlin/Android code.

---
name: kotlin-concurrency-expert
description: Kotlin Coroutines review and remediation for Android. Use when asked to review concurrency usage, fix coroutine-related bugs, improve thread safety, or resolve lifecycle issues in Kotlin/Android code.
---

# Kotlin Concurrency Expert

## Overview

Review and fix Kotlin Coroutines issues in Android codebases by applying structured concurrency, lifecycle safety, proper scoping, and modern best practices with minimal behavior changes.

## Workflow

### 1. Triage the Issue

- Capture the exact error, crash, or symptom (ANR, memory leak, race condition, incorrect state).
- Check project coroutines setup: `kotlinx-coroutines-android` version, `lifecycle-runtime-ktx` version.
- Identify the current scope context (`viewModelScope`, `lifecycleScope`, custom scope, or none).
- Confirm whether the code is UI-bound (`Dispatchers.Main`) or intended to run off the main thread (`Dispatchers.IO`, `Dispatchers.Default`).
- Verify Dispatcher injection patterns for testability.

### 2. Apply the Smallest Safe Fix

Prefer edits that preserve existing behavior while satisfying structured concurrency and lifecycle safety.

Common fixes:

- **ANR / Main thread blocking**: Move heavy work to `withContext(Dispatchers.IO)` or `Dispatchers.Default`; ensure suspend functions are main-safe.
- **Memory leaks / zombie coroutines**: Replace `GlobalScope` with a lifecycle-bound scope (`viewModelScope`, `lifecycleScope`, or injected `applicationScope`).
- **Lifecycle collection issues**: Replace deprecated `launchWhenStarted` with `repeatOnLifecycle(Lifecycle.State.STARTED)`.
- **State exposure**: Encapsulate `MutableStateFlow` / `MutableSharedFlow`; expose read-only `StateFlow` or `Flow`.
- **CancellationException swallowing**: Ensure generic `catch (e: Exception)` blocks rethrow `CancellationException`.
- **Non-cooperative cancellation**: Add `ensureActive()` or `yield()` in tight loops for cooperative cancellation.
- **Callback APIs**: Convert listeners to `callbackFlow` with proper `awaitClose` cleanup.
- **Hardcoded Dispatchers**: Inject `CoroutineDispatcher` via constructor for testability.

## Critical Rules

### Dispatcher Injection (Testability)

```kotlin
// CORRECT: Inject dispatcher
class UserRepository(
    private val ioDispatcher: CoroutineDispatcher = Dispatchers.IO
) {
    suspend fun fetchUser() = withContext(ioDispatcher) { ... }
}

// INCORRECT: Hardcoded dispatcher
class UserRepository {
    suspend fun fetchUser() = withContext(Dispatchers.IO) { ... }
}
```

### Lifecycle-Aware Collection

```kotlin
// CORRECT: Use repeatOnLifecycle
viewLifecycleOwner.lifecycleScope.launch {
    viewLifecycleOwner.repeatOnLifecycle(Lifecycle.State.STARTED) {
        viewModel.uiState.collect { state -> updateUI(state) }
    }
}

// INCORRECT: Direct collection (unsafe, deprecated)
lifecycleScope.launchWhenStarted {
    viewModel.uiState.collect { state -> updateUI(state) }
}
```

### State Encapsulation

```kotlin
// CORRECT: Expose read-only StateFlow
class MyViewModel : ViewModel() {
    private val _uiState = MutableStateFlow(UiState())
    val uiState: StateFlow<UiState> = _uiState.asStateFlow()
}

// INCORRECT: Exposed mutable state
class MyViewModel : ViewModel() {
    val uiState = MutableStateFlow(UiState()) // Leaks mutability
}
```

### Exception Handling

```kotlin
// CORRECT: Rethrow CancellationException
try {
    doSuspendWork()
} catch (e: CancellationException) {
    throw e // Must rethrow!
} catch (e: Exception) {
    handleError(e)
}

// INCORRECT: Swallows cancellation
try {
    doSuspendWork()
} catch (e: Exception) {
    handleError(e) // CancellationException swallowed!
}
```

### Cooperative Cancellation

```kotlin
// CORRECT: Check for cancellation in tight loops
suspend fun processLargeList(items: List<Item>) {
    items.forEach { item ->
        ensureActive() // Check cancellation
        processItem(item)
    }
}

// INCORRECT: Non-cooperative (ignores cancellation)
suspend fun processLargeList(items: List<Item>) {
    items.forEach { item ->
        processItem(item) // Never checks cancellation
    }
}
```

### Callback Conversion

```kotlin
// CORRECT: callbackFlow with awaitClose
fun locationUpdates(): Flow<Location> = callbackFlow {
    val listener = LocationListener { location ->
        trySend(location)
    }
    locationManager.requestLocationUpdates(listener)
    
    awaitClose { locationManager.removeUpdates(listener) }
}
```

## Scope Guidelines

| Scope | Use When | Lifecycle |
|-------|----------|-----------|
| `viewModelScope` | ViewModel operations | Cleared with ViewModel |
| `lifecycleScope` | UI operations in Activity/Fragment | Destroyed with lifecycle owner |
| `repeatOnLifecycle` | Flow collection in UI | Started/Stopped with lifecycle state |
| `applicationScope` (injected) | App-wide background work | Application lifetime |
| `GlobalScope` | **NEVER USE** | Breaks structured concurrency |

## Testing Pattern

```kotlin
@Test
fun `loading data updates state`() = runTest {
    val testDispatcher = StandardTestDispatcher(testScheduler)
    val repository = FakeRepository()
    val viewModel = MyViewModel(repository, testDispatcher)
    
    viewModel.loadData()
    advanceUntilIdle()
    
    assertEquals(UiState.Success(data), viewModel.uiState.value)
}
```

## Reference Material

- [Kotlin Coroutines Best Practices](https://developer.android.com/kotlin/coroutines/coroutines-best-practices)
- [StateFlow and SharedFlow](https://developer.android.com/kotlin/flow/stateflow-and-sharedflow)
- [repeatOnLifecycle API](https://developer.android.com/topic/libraries/architecture/coroutines#repeatOnLifecycle)

Excerpt, first 5,676 characters of SKILL.md, verbatim from the audited commit. It is text from someone else’s repository, quoted so you can judge it before your agent reads it.

git clone https://github.com/new-silvermoon/awesome-android-agent-skills
git -C awesome-android-agent-skills checkout 4bc96bf96aac

Works in

1. 2026-10-31
   ✓SAFE B 89 / 100

   first audit · source 4bc96bf96aac

Questions about kotlin-concurrency-expert

• github.com/new-silvermoon/awesome-android-agent-skills/tree/main — the audited source at commit 4bc96bf96aac and every finding aboveObserved · 31 Oct 2026

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