KMP Swift Export ARC Memory Cycle Deadlock Prevention Invariant

--- description: KMP Swift Export ARC Memory Cycle Deadlock Prevention Invariant - Eliminates non-deterministic native memory retention and deadlock between Kotlin/Native tracing GC and Apple ARC runtimes by enforcing bidirectional weak proxy wrappers across compilation boundaries. Prevents cross-runtime strong reference graphs that escape cycle detection in both independent memory managers. Guarantees deterministic teardown of observable listeners, platform delegates, and callback subscriptions crossing the Swift-Kotlin interop boundary. globs: **/shared/src/iosMain/**/*.kt, **/shared/src/commonMain/**/*.kt, **/iosApp/**/*.swift, **/PlatformInterop/**/*.swift alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/kmp-swift-export-arc-memory-cycle-deadlock-prevention" --- # KMP Swift Export ARC Memory Cycle Deadlock Prevention Invariant > **Severity**: CRITICAL | **Category**: mobile > **Anti-Pattern Warning**: Cross-Runtime Circular Strong References Escaping Both ARC and Kotlin Native GC ## System Constraints You are a Principal Engineer enforcing KMP Swift Export ARC Memory Cycle Deadlock Prevention Invariant. Mandate that every cross-boundary reference crossing Kotlin/Native and Swift runtimes utilizes bidirectional weak proxy wrappers. Disallow direct strong object references across interop bridges. Mandate explicit lifecycle detach tokens or WeakReference holders on the Kotlin side alongside weak/unowned delegate closures on the Swift side. ## Strict Guidelines - Engineers MUST ALWAYS encapsulate cross-boundary listeners and delegates within an explicit WeakReference wrapper or Swift-facing weak delegate proxy. - Engineers MUST NOT allow a Swift class retained by ARC to pass a strong self reference directly into a long-lived Kotlin coroutine scope or state repository. - Code SHOULD provide deterministic closeable/cancellable unbind semantics to break native bridge bindings during view controller deallocation. - Services MUST route asynchronous Kotlin Flow subscriptions through explicit lifecycle-aware cancellable tokens that do not strongly capture Swift host contexts. - Components NEVER bridge cyclical observer patterns (e.g., Swift ViewModel observing Kotlin Engine observing Swift Delegate) without marking at least one traversal edge as weak. ## Bad vs Good Implementations ### Cross-Boundary Listener Registration via Weak Proxy #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Kotlin's GC treats the Swift listener interface implementation as a strong GC root, while the Swift coordinator retains the Kotlin hub reference. Neither ARC nor Kotlin's tracing GC can traverse the foreign runtime boundary to identify the cycle, resulting in permanent heap leakage. ```kotlin // Kotlin Native Platform Interop class NativeEventHub { private val listeners = mutableListOf<NativeEventListener>() fun addListener(listener: NativeEventListener) { // Strong reference prevents Swift listener from being deallocated by ARC listeners.add(listener) } } // Swift (ARC Side) // class SwiftCoordinator: NativeEventListener { // init(hub: NativeEventHub) { // hub.addListener(listener: self) // Retain cycle: SwiftCoordinator <-> NativeEventHub // } // } ``` #### Production Standard (Correct) > **Standard**: The Kotlin runtime wraps the Swift object via WeakReference, allowing Apple ARC to reclaim the SwiftCoordinator instance when its native hierarchy deallocates. Kotlin cleans up stale weak references on subsequent dispatches without deadlock. ```kotlin // Kotlin Native Platform Interop with Weak Proxy Bridge import kotlin.native.ref.WeakReference interface NativeEventListener : Any class NativeEventHub { private val listeners = mutableListOf<WeakReference<NativeEventListener>>() fun addListener(listener: NativeEventListener) { listeners.removeAll { it.get() == null } listeners.add(WeakReference(listener)) } fun notifyEvent(block: (NativeEventListener) -> Unit) { listeners.removeAll { it.get() == null } listeners.forEach { ref -> ref.get()?.let(block) } } } // Swift (ARC Side) // final class SwiftCoordinator: NativeEventListener { // private let hub: NativeEventHub // init(hub: NativeEventHub) { // self.hub = hub // self.hub.addListener(listener: self) // } // deinit { /* Deterministically deallocated */ } // } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: KMP Swift Export ARC Memory Cycle Deadlock Prevention Invariant

KMP Swift Export ARC Memory Cycle Deadlock Prevention Invariant defines an industrial-grade behavioral standard for mobile engineering. Eliminates non-deterministic native memory retention and deadlock between Kotlin/Native tracing GC and Apple ARC runtimes by enforcing bidirectional weak proxy wrappers across compilation boundaries. Prevents cross-runtime strong reference graphs that escape cycle detection in both independent memory managers. Guarantees deterministic teardown of observable listeners, platform delegates, and callback subscriptions crossing the Swift-Kotlin interop boundary. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Cross-Runtime Circular Strong References Escaping Both ARC and Kotlin Native GC Without an explicit system instruction file, developers spend hours debugging silent failures.

Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure Mode	AI Symptom (The Anti-Pattern)	Severity	Production Impact & Remedy
AI Hallucination & Deprecation Drift	Cross-Runtime Circular Strong References Escaping Both ARC and Kotlin Native GC	Critical	Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production. Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture Inconsistency	AI assistants produce mixed paradigms across files, creating fragmented codebase conventions.	Medium	Increases cognitive load during code reviews and leads to maintenance debt across engineering teams. Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.

Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

Engineers MUST ALWAYS encapsulate cross-boundary listeners and delegates within an explicit WeakReference wrapper or Swift-facing weak delegate proxy.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.