Desktop: renderer unresponsive on startup — marked.js walkTokens synchronous Markdown AST traversal blocks UI thread #32452

Description

OpenCode Desktop v1.17.7 on Windows 10 x64 crashes immediately after startup. The renderer process becomes unresponsive within ~60 seconds of launch, even without any user interaction — just opening the app and entering an existing project triggers the freeze.
This is the same root cause as issue #30906 (renderer unresponsive due to synchronous CPU-intensive operations on the UI thread), but triggered through a different code path: Markdown AST traversal (marked.js walkTokens) rather than diff computation (Myers execEditLength).
The app was auto-updated from v1.15.13 → v1.17.3 → v1.17.7. v1.15.13 worked fine; the regression started with the v1.16.0 Electron update.
Key log evidence:
window.log (16:33:49):
renderer unresponsive { window: 'main', currentURL: 'oc://renderer/index.html' }
Unresponsive samples (9 total) — all stuck in synchronous Markdown rendering:
at B.walkTokens (main-BR8G9WSs.js:11645:5) ← marked.js sync AST walk
at session-composer-state-C0aC1gfR.js:3396:20 ← Promise.all waiting
→ Markdown → PacedMarkdown → Show component chain ← SolidJS reactive cascade
window.log (16:36:03) — second session, same pattern:
renderer unresponsive after only 57 seconds of uptime
at h → q → J → vn → heal → stream (session-composer-state)
→ Markdown component render via SolidJS createResource/createComputed
manifest.json: uptime=69.88s — app killed within ~70 seconds
server.log at crash time:
global event disconnected
Secondary (non-fatal) issues observed across all sessions:

• @opencode-ai/plugin@local install failure (every 30-120s retry loop)
• duplicate skill name: find-skills (3 locations)
• ghostty-vt warning: unimplemented mode: 25
• Occasional fetch terminated errors to siliconflow API

Plugins

None (default installation, no custom plugins)

OpenCode version

v1.17.7 (auto-updated from v1.17.3, originally v1.15.13) Electron 42.3.3 / Chrome 148.0.7778.218 / Node 24.15.0 Windows x64, NSIS installer at %LOCALAPPDATA%\Programs@opencode-aidesktop

Steps to reproduce

1. Install OpenCode Desktop v1.17.7 on Windows 10/11 x64
2. Open an existing project with chat history (any project with prior sessions)
3. Wait 30-60 seconds — no interaction needed
4. Renderer becomes unresponsive, window freezes, process killed after ~10s watchdog timeout
   This happens on EVERY launch, not intermittently. The app is unusable.

Screenshot and/or share link

window.log

window.log

Operating System

Windows 10 x64 (build 19045)

Terminal

N/A — using Desktop app, not TUI