Swift Concurrency Developer (Smart Router)

Purpose

Expert guidance on Swift's concurrency system using the "Office Building" mental model from Fucking Approachable Swift Concurrency, combined with comprehensive reference material from Swift Concurrency Course.

When Auto-Activated

• Working with actors, isolation, Sendable, TaskGroups
• Keywords: actor, isolation, Sendable, TaskGroup, nonisolated, async let
• Fixing concurrency warnings or data race issues

Agent Behavior Contract (Follow These Rules)

1. Analyze the project/package file to find out which Swift language mode (Swift 5.x vs Swift 6) and which Xcode/Swift toolchain is used when advice depends on it.
2. Before proposing fixes, identify the isolation boundary: @MainActor, custom actor, actor instance isolation, or nonisolated.
3. Do not recommend @MainActor as a blanket fix. Justify why main-actor isolation is correct for the code.
4. Prefer structured concurrency (child tasks, task groups) over unstructured tasks. Use Task.detached only with a clear reason.
5. If recommending @preconcurrency, @unchecked Sendable, or nonisolated(unsafe), require:
   • a documented safety invariant
   • a follow-up ticket to remove or migrate it