feat(web): convert HEIC photo attachments to JPEG

[mweinbach]

HEIC and HEIF photos currently fail composer attachment validation, and Chromium-based clients cannot decode them natively.

Convert dropped and pasted HEIC/HEIF photos to JPEG before upload, recognize photos whose browser MIME type is missing, preserve JPEG output when oversized images need compression, and lazy-load a CSP-compatible decoder. Document the behavior for web and desktop users.

Verification:

• vp test run apps/web/src/lib/imageCompression.test.ts apps/web/src/components/chat/workspaceFileDrop.test.ts — 22 passing tests
• vp lint apps/web/src/lib/imageCompression.ts apps/web/src/lib/imageCompression.test.ts apps/web/src/components/chat/ChatComposer.tsx
• vp run --filter @t3tools/web typecheck
• vp run --filter @t3tools/web build

Model: gpt 5.6 sol
Harness: Codex

---

Note

Medium Risk
Changes the composer attachment pipeline and adds client-side HEIC decoding; existing size and unreadable-error behavior is preserved but new decoder failures surface as attachment errors.

Overview
Enables HEIC/HEIF photos in the message composer by converting them to JPEG before upload, since providers and many browsers cannot use those formats directly.

Composer drag-and-drop and paste now treat HEIC/HEIF as images (including files with empty or generic MIME types via .heic/.heif extension checks) and route attachments through new prepareImageForAttachment instead of compressImageToByteLimit alone. That path lazy-loads the heic-to/csp decoder, converts to JPEG, then applies the existing byte-cap compression; oversized intermediates stay JPEG via preferredMimeType, and the original HEIC size still gates the 50MB decode-safety limit even when conversion inflates the blob.

User-facing copy and docs now list HEIC/HEIF among supported formats and note automatic conversion on web/desktop.

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

Note

Convert HEIC photo attachments to JPEG in ChatComposer

• Adds isHeicImageFile to detect HEIC/HEIF by MIME type or extension, and prepareImageForAttachment to decode them to JPEG using the heic-to library.
• ChatComposer now accepts HEIC/HEIF files on paste and drag-and-drop, passing them through prepareImageForAttachment instead of compressImageToByteLimit.
• compressImageToByteLimit gains preferredMimeType and sourceSizeBytes options to force JPEG output and enforce the source size safety ceiling without loading the decoder.
• Risk: HEIC decoding failures surface as an unreadable attachment error; files larger than MAX_COMPRESSIBLE_SOURCE_BYTES are rejected before decoding.

^{Macroscope summarized ffcebad.}

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[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR adds a new browser-side HEIC/HEIF decoding dependency and changes attachment validation, preprocessing, previews, and uploaded payloads. The user-facing workflow and associated runtime processing are substantial enough to require human review.

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[t3dotgg]

Note

🤖 GPT-5.6 Sol responding on behalf of Theo

Closing in favor of merged #8161, which builds on this work and adds safe HEIC decoding and JPEG conversion for composer attachments. This PR is credited in #8161.