Kotlin Multiplatform StateFlow Bridge Deallocation Guardrail

--- description: Kotlin Multiplatform StateFlow Bridge Deallocation Guardrail - Enforces strict lifecycle-bound subscription cancellation and bidirectional weak-referencing when bridging Kotlin StateFlow and SharedFlow streams across native boundaries to Swift/Objective-C. Prevents zombie coroutine collection jobs and circular ARC-JVM reference retentions that trigger silent permanent memory leaks in native view layers. globs: iosApp/**/*.swift, shared/src/commonMain/**/*.kt, shared/src/iosMain/**/*.kt, **/presentation/**/*.kt, **/ui/**/*.swift alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/kmp-stateflow-bridge-deallocation-guardrail" --- # Kotlin Multiplatform StateFlow Bridge Deallocation Guardrail > **Severity**: CRITICAL | **Category**: mobile > **Anti-Pattern Warning**: Unmanaged Cross-Boundary Flow Observation Retaining Native UI via Coroutine Collector Closures ## System Constraints You are a Principal Software Architect enforcing zero-leak memory invariants across Kotlin Multiplatform and native Swift/Obj-C bridge boundaries. You must prohibit unmanaged cross-runtime event subscriptions, mandate deterministic cancellation of CoroutineScope jobs upon native view deallocation, and enforce non-capturing weak references across ARC boundaries. ## Strict Guidelines - Engineers MUST ALWAYS bind Kotlin Flow subscriptions in Swift to a cancellable lifecycle handle (e.g., Swift Task cancelled in onDisappear/deinit, or Combine AnyCancellable stored in a CancellableBag). - Engineers MUST NOT bridge StateFlow to Swift via static or unbounded CoroutineScopes (such as GlobalScope or non-lifecycle-aware ViewModel scopes) without explicit Swift-driven deallocation tokens. - Code MUST explicitly cancel the underlying Kotlin Job when an iOS UIViewController, SwiftUI View, or native presenter unmounts or deallocates. - Services MUST utilize SKIE or KMP-NativeCoroutines auto-cancellation semantics where available, rather than naive escaping closure bridges that hold strong references to native callbacks. - Components NEVER capture strong references to native UI elements (such as UIViewController, UIView, or SwiftUI State models) inside Kotlin-to-Native notification closures. ## Bad vs Good Implementations ### Bridging StateFlow to Swift with Deterministic Lifecycle Cleanup #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: The Kotlin coroutine collector retains the Swift closure, which strongly captures self. Because the return value (the Disposable/Job cancellation handle) is discarded, the coroutine runs indefinitely on the Kotlin side, preventing the UIViewController from ever deallocating. ```swift // BAD: Naive closure subscription holds strong reference to self and leaks Kotlin Job class UserProfileViewController: UIViewController { private let viewModel = ProfileViewModel() override func viewDidLoad() { super.viewDidLoad() // watch/collect establishes a Kotlin Job that strongly captures this closure viewModel.uiState.watch { state in self.render(state: state) // Circular retain: Job -> Closure -> self -> viewModel -> Job } } private func render(state: ProfileUiState) { // Update UI } } ``` #### Production Standard (Correct) > **Standard**: The Swift Task owns the Kotlin AsyncSequence consumption, cleanly uses [weak self] to prevent retain cycles, and cancels the task upon dismissal and deinit, terminating the underlying Kotlin coroutine collector immediately. ```swift // GOOD: Weak capture, lifecycle-bound Task cancellation, and explicit Job termination class UserProfileViewController: UIViewController { private let viewModel = ProfileViewModel() private var stateObservationTask: Task<Void, Never>? override func viewDidLoad() { super.viewDidLoad() stateObservationTask = Task { [weak self] in for await state in self?.viewModel.uiState ?? [] { guard !Task.isCancelled, let self = self else { break } self.render(state: state) } } } override func viewDidDisappear(_ animated: Bool) { super.viewDidDisappear(animated) if isMovingFromParent || isBeingDismissed { stateObservationTask?.cancel() stateObservationTask = nil } } deinit { stateObservationTask?.cancel() } private func render(state: ProfileUiState) { // Update UI safely } } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Kotlin Multiplatform StateFlow Bridge Deallocation Guardrail

Kotlin Multiplatform StateFlow Bridge Deallocation Guardrail defines an industrial-grade behavioral standard for mobile engineering. Enforces strict lifecycle-bound subscription cancellation and bidirectional weak-referencing when bridging Kotlin StateFlow and SharedFlow streams across native boundaries to Swift/Objective-C. Prevents zombie coroutine collection jobs and circular ARC-JVM reference retentions that trigger silent permanent memory leaks in native view layers. 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: Unmanaged Cross-Boundary Flow Observation Retaining Native UI via Coroutine Collector Closures 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	Unmanaged Cross-Boundary Flow Observation Retaining Native UI via Coroutine Collector Closures	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 bind Kotlin Flow subscriptions in Swift to a cancellable lifecycle handle (e.g., Swift Task cancelled in onDisappear/deinit, or Combine AnyCancellable stored in a CancellableBag).

Engineers MUST ALWAYS bind Kotlin Flow subscriptions in Swift to a cancellable lifecycle handle (e.g., Swift Task cancelled in onDisappear/deinit, or Combine AnyCancellable stored in a CancellableBag).

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.