swift-concurrency

Swift Concurrency patterns — async/await, actors, tasks, Sendable conformance. Use when writing async/await code, implementing actors, working with structured concurrency, or ensuring data race safety.

Install with Tessl CLI

npx tessl i github:ravnhq/ai-toolkit --skill swift-concurrency

What are skills?

1.02x

Quality

78%

Does it follow best practices?

Impact

97%

1.02x

Average score across 3 eval scenarios

Optimize this skill with Tessl

npx tessl skill review --optimize ./skills/framework/swift-concurrency/SKILL.md

SKILL.md

Review

Evals

Evaluation results

100%

Shared Resource Registry for a Media Pipeline

Actor isolation and Sendable conformance

Criteria

Without context

With context

Actor for registry

100%

No NSLock/manual locks

100%

No @unchecked Sendable on registry

100%

Sendable JobRecord

100%

Explicit Sendable on public/struct

100%

Structured parallel workers

100%

No nested Task in task group

100%

Await required for actor access

100%

No Task.detached for workers

100%

Design notes explain actor choice

100%

Correct concurrency boundary

100%

Without context: $0.2524 · 1m 25s · 13 turns · 17 in / 4,731 out tokens

With context: $0.4337 · 1m 39s · 21 turns · 373 in / 4,323 out tokens

96%

-3%

Batch Data Import Pipeline

Task cancellation and structured concurrency

Criteria

Without context

With context

Structured parallelism

100%

No Task.detached

100%

No nested Task in group

100%

Cancellation check before stages

100%

Cancellation check in loop

87%

50%

CancellationError propagates

100%

Automatic child cancellation

100%

Sendable types

100%

Design doc explains cancellation

100%

No unstructured task leaks

100%

Without context: $0.3713 · 1m 28s · 20 turns · 27 in / 4,807 out tokens

With context: $0.4724 · 1m 36s · 25 turns · 2,767 in / 4,968 out tokens

96%

10%

Notification Dispatcher Test Suite

Async test patterns and dummy suspension avoidance

Criteria

Without context

With context

No dummy Task.yield in queue

100%

Correct async on queue

100%

No dummy yield in isDispatching

100%

Actor not @unchecked Sendable class

100%

No manual locking

100%

Swift Testing preferred

100%

No blocking wait(for:)

100%

Correct async fulfillment or direct await

100%

isDispatching test deterministic

60%

Cancellation test present

100%

Review notes explain dummy suspension fix

100%

Review notes explain test fix

100%

Without context: $0.4418 · 2m 15s · 20 turns · 26 in / 7,753 out tokens

With context: $0.8631 · 3m 16s · 29 turns · 8,287 in / 10,909 out tokens

Evaluated: 4 days ago
Agent: Claude Code
Model: Claude Sonnet 4.6

Table of Contents

Shared Resource Registry for a Media Pipeline Batch Data Import Pipeline Notification Dispatcher Test Suite

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