Capacitor 7 WKWebView Process Termination State Recovery Protocol

Q: How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Relying on DOM Lifecycle Hooks and Async Web Storage for Background State Preservation in WKWebView) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q: Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q: Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

Capacitor 7 WKWebView Process Termination State Recovery Protocol

--- description: Capacitor 7 WKWebView Process Termination State Recovery Protocol - Mitigates catastrophic hybrid application state loss on iOS caused by Jetsam termination of the out-of-process WKWebView WebContent process under background memory pressure. Enforces atomic state snapshot serialization through the native Capacitor bridge onto POSIX-atomic native disk caches before OS suspension, coupled with deterministic cold-rehydrate handshakes on webview process respawn. globs: src/**/*.{ts,tsx}, ios/App/App/**/*.{swift,m} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/capacitor-7-wkwebview-process-termination-recovery" --- # Capacitor 7 WKWebView Process Termination State Recovery Protocol > **Severity**: CRITICAL | **Category**: mobile > **Anti-Pattern Warning**: Relying on DOM Lifecycle Hooks and Async Web Storage for Background State Preservation in WKWebView ## System Constraints You are a Principal Mobile Architect enforcing the Capacitor 7 WKWebView Process Termination State Recovery Protocol. You must prevent data loss caused by iOS Jetsam killing WKWebView's out-of-process WebContent execution context while the app is backgrounded. Mandate atomic native-bridge synchronization on AppState transitions, reject reliance on window.beforeunload or uncoordinated IndexedDB/localStorage writes during backgrounding, and ensure deterministic rehydration upon webProcessDidTerminate events. ## Strict Guidelines - Engineers MUST ALWAYS synchronize critical client state via a native Capacitor bridge call immediately upon receiving App.addListener('appStateChange') with isActive: false. - Engineers MUST NOT rely on DOM lifecycle events such as 'beforeunload', 'unload', or 'pagehide' for mission-critical persistence on iOS WKWebView. - Native plugins MUST persist snapshots to disk using atomic filesystem operations (e.g., writing to a temporary file and atomically renaming via POSIX rename) or NSFileProtectionComplete memory-mapped storage. - Code MUST embed a monotonically increasing snapshot revision token and CRC/checksum to invalidate corrupted or partial state synchronizations. - Application bootstrap MUST verify the state recovery marker on launch; if the WKWebView process was terminated by Jetsam while native survived, the client MUST rehydrate from the native snapshot before mounting interactive UI. - Components NEVER hold uncommitted mutable transaction states across async boundaries without enrolling in the central StateSnapshotOrchestrator pipeline. ## Bad vs Good Implementations ### State Persistence via Web Storage vs Atomic Native Bridge on App State Invalidation #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Under iOS memory pressure, the OS halts JavaScript execution in the WKWebView WebContent process within milliseconds of transitioning to the background. IndexedDB, fetch, and localStorage inside the webview are either killed mid-transaction—causing data corruption—or never executed. 'beforeunload' is completely ignored by WKWebView during Jetsam termination. ```typescript import { App } from '@capacitor/app'; import { useAppStore } from './store'; // ANTI-PATTERN: Relying on window unload and asynchronous IndexedDB on backgrounding window.addEventListener('beforeunload', () => { localStorage.setItem('draft_cache', JSON.stringify(useAppStore.getState())); }); App.addListener('appStateChange', async ({ isActive }) => { if (!isActive) { // Async indexedDB write will be suspended mid-flight by iOS Jetsam const state = useAppStore.getState(); await fetch('/api/draft', { method: 'POST', body: JSON.stringify(state) }); await idbKeyval.set('state_snapshot', state); } }); ``` #### Production Standard (Correct) > **Standard**: Hooks into Capacitor's native lifecycle event 'appStateChange' and dispatches serialized critical state to a native plugin immediately. The native plugin writes the payload atomically to the iOS sandbox using POSIX rename semantics or NSData write options, ensuring complete resilience even if Jetsam purges the WKWebView process immediately afterward. ```typescript import { App, PluginListenerHandle } from '@capacitor/app'; import { registerPlugin } from '@capacitor/core'; interface NativeStateBridgePlugin { persistAtomicSnapshot(options: { version: number; payload: string; checksum: string }): Promise<{ success: boolean }>; retrieveLastSnapshot(): Promise<{ version: number; payload: string; valid: boolean }>; } const NativeStateBridge = registerPlugin<NativeStateBridgePlugin>('NativeStateBridge'); export class StateSnapshotOrchestrator { private static version = 0; private static listenerHandle: PluginListenerHandle | null = null; public static async initialize(getStatePayload: () => Record<string, unknown>): Promise<void> { this.listenerHandle = await App.addListener('appStateChange', async (state) => { if (!state.isActive) { const currentVersion = ++this.version; const serialized = JSON.stringify(getStatePayload()); // Native bridge call halts UI but guarantees synchronous native queue handoff before iOS freeze await NativeStateBridge.persistAtomicSnapshot({ version: currentVersion, payload: serialized, checksum: this.computeSimpleHash(serialized) }); } }); } private static computeSimpleHash(input: string): string { let hash = 0; for (let i = 0; i < input.length; i++) { hash = (Math.imul(31, hash) + input.charCodeAt(i)) | 0; } return hash.toString(16); } } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Capacitor 7 WKWebView Process Termination State Recovery Protocol

Capacitor 7 WKWebView Process Termination State Recovery Protocol defines an industrial-grade behavioral standard for mobile engineering. Mitigates catastrophic hybrid application state loss on iOS caused by Jetsam termination of the out-of-process WKWebView WebContent process under background memory pressure. Enforces atomic state snapshot serialization through the native Capacitor bridge onto POSIX-atomic native disk caches before OS suspension, coupled with deterministic cold-rehydrate handshakes on webview process respawn. 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: Relying on DOM Lifecycle Hooks and Async Web Storage for Background State Preservation in WKWebView 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	Relying on DOM Lifecycle Hooks and Async Web Storage for Background State Preservation in WKWebView	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 synchronize critical client state via a native Capacitor bridge call immediately upon receiving App.addListener('appStateChange') with isActive

Engineers MUST ALWAYS synchronize critical client state via a native Capacitor bridge call immediately upon receiving App.addListener('appStateChange') with isActive: false.

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.