🐛 Bugfix: Why does Chrome show 'Page Unresponsive' immediately after a...

Date: 2026-02-23
Time: 21:52:55 UTC
Session: gspace1-139.5
Agent: angular
Confidence: 95%
Status: ✅ Documented

📋 Decision Context

Question:

Why does Chrome show 'Page Unresponsive' immediately after all 7 generation phases complete at 100%?

Task: S138.7 fix Page Unresponsive at 100% completion

🎯 Decision Made

Chosen:

Two-layer fix: (1) In workflow-state.service.ts, deferred JSON.parse(manifestJSON) + generatedManifest.set() into timer(0) callback so the 500ms-2s parse doesn't block the SSE event handler. (2) In vibe-universe-generator, created deferPostCompletionWork() that chains persistGenerationState, registerGeneratedModuleManifest, and autoSyncModulesToCanvas with timer(50) gaps between each, spreading ~2-4.5s of synchronous work across 150ms+ of frame yields.

Options Considered:

1. Use Web Worker for JSON.parse off main thread
2. Break up completion work with RxJS timer() yields between heavy operations

💭 Reasoning

The root cause was 6 heavy synchronous operations running back-to-back in the SSE completion callback without yielding to the browser: JSON.parse on 5-10MB manifest (500ms-2s), computed signal cascades from generatedManifest.set() (300-800ms), sessionStorage persistence with JSON.stringify (300-500ms), buildGeneratedUniverseTree (200-500ms), and broadcastNodeCreate loop (100-300ms). Total 1.6-4.6s of main thread blocking triggers Chrome's 'Page Unresponsive' threshold. The timer(0) approach yields to the browser's event loop between operations, letting the UI paint and handle user input. Using RxJS timer() instead of setTimeout() to comply with workspace conventions.

📁 Files Involved

• libs/libs-ai/gograb-ai-lib/src/lib/services/workflow-state.service.ts
• libs/libs-structural/vibe-universe/src/lib/components/vibe-universe-generator/vibe-universe-generator.component.ts

🔗 Related

• Decision ID: dev_1771883575577_5y3sa32
• Session: 139
• Workspace: gspace1

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