React Native 0.77+ Bridgeless C++ JSI Memory Lifecycle Guardrail

--- description: React Native 0.77+ Bridgeless C++ JSI Memory Lifecycle Guardrail - Enforces strict memory ownership boundaries between C++ HostObjects and the Hermes JavaScript Garbage Collector under React Native 0.77+ Bridgeless Architecture. Prevents SIGSEGV crashes, use-after-free conditions, and uncollectable GC roots during asynchronous native callbacks across rapid unmount/mount component lifecycles. globs: src/**/*.{ts,tsx}, ios/**/*.{h,m,mm,cpp}, android/src/main/jni/**/*.{h,cpp}, cpp/**/*.{h,cpp} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/react-native-bridgeless-jsi-lifecycle-guardrail" --- # React Native 0.77+ Bridgeless C++ JSI Memory Lifecycle Guardrail > **Severity**: CRITICAL | **Category**: mobile > **Anti-Pattern Warning**: Dangling C++ JSI References and Stale Callbacks Outliving Unmounted React Fiber Nodes ## System Constraints You are a Principal Mobile Architect enforcing C++ JSI memory and lifecycle safety in React Native 0.77+ Bridgeless Architecture. You must ensure that no jsi::Value, jsi::Object, or jsi::Function is retained asynchronously past the lifespan of its originating Hermes Runtime or the React component mounting context. Mandate RAII, std::weak_ptr, thread-safe CallInvoker dispatching, and deterministic unregister hooks on cleanup. ## Strict Guidelines - Engineers MUST ALWAYS capture C++ HostObjects via std::weak_ptr in asynchronous callbacks and dispatch through facebook::react::CallInvoker::invokeAsync. - Engineers MUST NEVER retain raw jsi::Value, jsi::Object, or jsi::Function pointers across asynchronous dispatch boundaries without wrapping them in jsi::Value or using an explicit cancellation token. - Engineers MUST ALWAYS invalidate and release native JSI listeners within useEffect/useLayoutEffect cleanup return closures to prevent uncollectable root references in Hermes GC. - Native C++ JSI implementations MUST verify that the jsi::Runtime instance is valid and not shutting down prior to invoking JavaScript callbacks from secondary threads. - Components NEVER trigger native subscription allocations without storing a deterministic cleanup unregister token in a useRef or useEffect destructor. ## Bad vs Good Implementations ### JSI Event Subscription Lifecycle in Bridgeless React Native #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Passing a plain JavaScript closure directly to a C++ JSI interface without acquiring an unsubscription token causes the native host to hold a persistent jsi::Function reference. If the component unmounts and Hermes runs garbage collection while C++ invokes the closure, the application crashes with a fatal SIGSEGV (use-after-free). ```typescript import { useEffect } from 'react'; declare const NativeSensorJSI: { subscribe: (callback: (data: number) => void) => void; }; export function SensorMonitor() { useEffect(() => { // ANTI-PATTERN: Passing callback directly to JSI without unregister handle // When unmounted rapidly, C++ attempts to invoke a garbage-collected jsi::Function NativeSensorJSI.subscribe((data) => { console.log('Received sensor data:', data); }); }, []); return null; } ``` #### Production Standard (Correct) > **Standard**: Maintains an explicit lifecycle token (`subscriptionRef`) and safely tears down the native listener within the `useEffect` cleanup return. Pairing an `isMounted` guard with deterministic C++ native unregistration cleans up HostObject references and prevents execution against invalid Hermes GC scopes. ```typescript import { useEffect, useRef } from 'react'; interface SensorSubscription { remove: () => void; } declare const NativeSensorJSI: { subscribe: (callback: (data: number) => void) => SensorSubscription; }; export function SensorMonitor() { const subscriptionRef = useRef<SensorSubscription | null>(null); useEffect(() => { let isMounted = true; subscriptionRef.current = NativeSensorJSI.subscribe((data: number) => { if (!isMounted) { return; } console.log('Received sensor data:', data); }); return () => { isMounted = false; if (subscriptionRef.current) { subscriptionRef.current.remove(); subscriptionRef.current = null; } }; }, []); return null; } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: React Native 0.77+ Bridgeless C++ JSI Memory Lifecycle Guardrail

React Native 0.77+ Bridgeless C++ JSI Memory Lifecycle Guardrail defines an industrial-grade behavioral standard for mobile engineering. Enforces strict memory ownership boundaries between C++ HostObjects and the Hermes JavaScript Garbage Collector under React Native 0.77+ Bridgeless Architecture. Prevents SIGSEGV crashes, use-after-free conditions, and uncollectable GC roots during asynchronous native callbacks across rapid unmount/mount component lifecycles. 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: Dangling C++ JSI References and Stale Callbacks Outliving Unmounted React Fiber Nodes 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	Dangling C++ JSI References and Stale Callbacks Outliving Unmounted React Fiber Nodes	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 capture C++ HostObjects via std

Engineers MUST ALWAYS capture C++ HostObjects via std::weak_ptr in asynchronous callbacks and dispatch through facebook::react::CallInvoker::invokeAsync.

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.