fix(terminal): prevent crash during resize with high-output programs #114
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Fixes a race condition that causes crashes when resizing the terminal while programs with high output (like cmatrix, htop) are running. The issue occurs because the render loop and write operations can access WASM memory buffers while resize() is reallocating them, causing SIGSEGV crashes. This fix implements three protections: 1. **Pause render loop during resize**: Cancel the animation frame before WASM resize and restart after, preventing concurrent buffer access. 2. **Invalidate cached buffer views**: Clear graphemeBuffer and graphemeBufferPtr when invalidating buffers, since TypedArray views become detached when underlying memory is reallocated. 3. **Queue writes during resize**: Buffer incoming PTY data during resize and flush after a frame, preventing writes from hitting WASM while buffers are being reallocated. All three protections are needed to fully prevent the race condition with rapidly-outputting programs.
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sreya
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Jan 13, 2026
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| private _isResizing = false; | ||
| private _writeQueue: Array<{ data: string | Uint8Array; callback?: () => void }> = []; | ||
| private _resizeFlushFrameId?: number; |
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Any specific reason why we're prefixing these with _?
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sry just used to prefixing private vars with _. i can remove it if u like
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Yeah if you could, just for consistency
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Summary
Fixes a race condition that causes crashes when resizing the terminal while programs with high output (like cmatrix, htop) are running.
The issue occurs because the render loop and write operations can access WASM memory buffers while
resize()is reallocating them, causing SIGSEGV crashes.Changes
This PR implements three protections:
Pause render loop during resize: Cancel the animation frame before WASM resize and restart after, preventing concurrent buffer access.
Invalidate cached buffer views: Clear
graphemeBufferandgraphemeBufferPtrwhen invalidating buffers, since TypedArray views become detached when underlying memory is reallocated.Queue writes during resize: Buffer incoming PTY data during resize and flush after a frame, preventing writes from hitting WASM while buffers are being reallocated.
All three protections are needed to fully prevent the race condition with rapidly-outputting programs.
Testing
cmatrix- no longer crashesFiles Changed
lib/terminal.ts- Main resize protection logiclib/ghostty.ts- Buffer invalidation for graphemeBuffer