[Desktop] Pasting a large HTML block into a new session freezes the app, renderer is OOM-killed and forces relaunch

Description

OpenCode Desktop freezes completely after pasting a large block of HTML (a full rendered page source) into the prompt of a brand-new tab/session. The UI becomes unresponsive, and after a while a dialog appears asking to relaunch the app. Debug export confirms the renderer process was killed by an out-of-memory condition (render-process-gone with reason: 'oom').

Expected: the app should handle large pastes gracefully — e.g. truncate with a notice, virtualize/lazy-render, or debounce syntax highlighting — never freeze and crash the whole window.

Environment

• OpenCode Desktop **

opencode-debug-20260831T110653.zip

** (packaged), Windows 11 x64

• Electron 42.3.3 / Chrome 148.0.7778.218 (from debug bundle manifest.json)
• Date of incident: 2026-08-31, session log dir desktop/20260831T073703

Log evidence (from debug export)

Renderer killed by OOM — desktop/20260831T073703/window.log:

[2026-08-31 14:06:15.318] [error] (window) app render process gone {
  url: 'oc://renderer/index.html',
  details: { reason: 'oom', exitCode: -536870904 }
}

(exitCode -536870904 = 0xE0000008)

Heavy layout-thrash storm right after the paste — renderer.log shows ~243
ResizeObserver loop completed with undelivered notifications errors, with the
densest burst running 13:46:47 → 13:47:33 (~140 events, one every ~200ms,
nonstop for ~46s) — consistent with the editor/message view re-measuring and
re-rendering the pasted content in a loop until memory exhaustion.

Meanwhile main.log shows the main process completely healthy (only routine
updater ticks) and the sidecar exited cleanly (code: 0) — so this is isolated
to the renderer/UI layer, not the server or the LLM stream.

Timeline: paste ≈ 13:46–13:47 → UI frozen (render thrash) → renderer OOM-killed at 14:06:15 → relaunch prompt; fresh session starts at 14:06:18.

Suspected cause

The composer / message renderer has no input-size guard: a very large paste is
fully inserted and processed by the editor (syntax highlighting, line
tokenization, ResizeObserver-driven re-layout of the oversized DOM), pushing the
renderer past its memory limit until Chromium kills it.

Suggested fixes (any of these would prevent the crash)

• Cap paste size in the composer (e.g. warn/truncate beyond N KB, offer "attach as file" instead).
• Virtualize rendering of oversized composer content; don't highlight/measure the whole paste at once.
• Debounce/chunk syntax highlighting for large buffers, or disable highlighting above a size threshold.
• Treat render-process-gone with reason: 'oom' defensively (already shows relaunch — good — but the underlying ballooning should be prevented).

Attachments

Debug bundle: opencode-debug-20260831T110653.zip (exported from the app right after the incident). Can attach on request.

Plugins

ponytail

OpenCode version

1.18.25

Steps to reproduce

1. Open OpenCode Desktop on Windows.
2. Open a new tab (new session).
3. Paste a large HTML page (several hundred KB of markup) into the composer input.
4. App freezes; after some time the "relaunch" dialog appears.

Screenshot and/or share link

No response

Operating System

Windows 11

Terminal

No response