feat(web): pasting a huge screenshot now compresses it instead of erroring

[t3dotgg]

Pasting or dropping an image over 10MB into the composer just failed with "exceeds the 10MB attachment limit" — annoying for big retina screenshots that would survive compression with no meaningful quality loss.

Now oversized images are downscaled and re-encoded (WebP, JPEG fallback) to fit under the 10MB wire cap, reusing the same pipeline that already compresses images for the prompt stash. stashImageCompression.ts became the shared imageCompression.ts with a new compressImageToByteLimit entry point; stash behavior is unchanged. Images already under the cap still pass through byte-for-byte.

Sources over 50MB are refused outright — file size is a proxy for pixel count, and decoding something that large into an ImageBitmap risks OOMing the tab.

Web only: mobile's paste path has no canvas and keeps its existing 10MB reject.

Written by Claude Fable 5 via Claude Code.

🤖 Generated with Claude Code

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Note

Medium Risk
Changes user-facing send/attach behavior and runs canvas decode/re-encode on large pastes in the main composer path; failures are handled but wrong timing could still strand attachments or block send unexpectedly.

Overview
Pasting or dropping images larger than the provider wire cap no longer fails with a size error — they are downscaled and re-encoded (WebP/JPEG) to fit under PROVIDER_SEND_TURN_MAX_IMAGE_BYTES, while files already under the cap still attach byte-for-byte.

stashImageCompression is consolidated into shared imageCompression.ts: stash behavior stays on compressImageForStash, and compressImageToByteLimit returns a re-encoded File for the composer. A shared reencodeWithinBudget loop handles both paths; sources above MAX_COMPRESSIBLE_SOURCE_BYTES (50MB) are refused without decoding to avoid tab OOM.

addComposerImages is now async: it reserves attachment slots via a per-thread pending compression counter (so concurrent pastes respect the limit), compresses each accepted file, then updates preview/name/type from the result. submitComposer blocks send while compression is in flight and shows an info toast so a turn snapshot cannot miss an in-progress paste.

^{Reviewed by Cursor Bugbot for commit e765e2c. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Compress oversized pasted or dropped images instead of rejecting them

• Adds compressImageToByteLimit in imageCompression.ts that downscales and re-encodes image files to WebP/JPEG to fit the provider wire cap (PROVIDER_SEND_TURN_MAX_IMAGE_BYTES); files already within the limit pass through unchanged.
• Updates ChatComposer.tsx to compress pasted/dropped images asynchronously rather than hard-rejecting oversized ones.
• While compression is in progress, sending is blocked and an info toast prompts the user to send again once the thumbnail appears.
• Attachment slot reservation accounts for in-flight compressions so concurrent pastes cannot exceed the per-turn attachment cap.
• Sources above MAX_COMPRESSIBLE_SOURCE_BYTES are refused without decoding to avoid memory issues. Risk: users who previously received an error for large images will now see a delay before the compressed image appears.

^{Macroscope summarized e765e2c.}

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Approvability

Verdict: Needs human review

This PR introduces new feature behavior (compressing oversized images instead of rejecting them) with async state management and race condition handling. Additionally, there are two unresolved medium-severity review comments identifying potential bugs in the error clearing and slot reservation logic.

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Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

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