fix(web): include images when copying prompts

[StiensWout]

Copying a user prompt with an attached image only placed the text on the clipboard, so pasting into a new thread dropped the image.

The copy action now writes the prompt and first available attachment as one clipboard item. Images are normalized to PNG for browser clipboard support, while unsupported browsers keep the existing text-only fallback.

Proof

Testing

• vp test run on the message clipboard, copy hook, and message timeline tests
• Web package typecheck
• Targeted lint for the changed files
• Playwright copy and paste round trip in an isolated T3 environment

Implemented with GPT-5.6-Sol in the Codex harness inside T3 Code.

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Note

Low Risk
Client-only clipboard write with a text fallback. No auth, persistence, or server changes.

Overview
Copying a user prompt with an attachment now writes text and one image as a single clipboard item, so pasting into a new thread keeps the image.

writeMessageToClipboard fetches the preview, normalizes it to PNG, and uses navigator.clipboard.write. If there is no image, the browser lacks composite clipboard support, or the rich write fails, it still copies text.

The copy hook accepts an optional write override. User timeline copy uses the first attachment with a previewUrl (regular images first, then preview annotations). Assistant copy is unchanged.

^{Reviewed by Cursor Bugbot for commit 025f7ff. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Include images when copying chat prompts via MessageCopyButton

• Adds writeMessageToClipboard in messageClipboard.ts to write text plus a PNG image as a single ClipboardItem, falling back to text-only when unsupported or on error.
• Extends useCopyToClipboard in useCopyToClipboard.ts with an optional write override so callers can perform rich clipboard writes while keeping the hook's copied-state and callbacks.
• Passes a selected image (first regular image with a previewUrl, else first preview-annotation image) from UserTimelineRow in MessagesTimeline.tsx into MessageCopyButton, which uses the new path when an image is present.
• Risk: fetchClipboardImageAsPng relies on fetch + offscreen canvas conversion; if the preview URL is cross-origin without CORS headers, the canvas taints and the write fails, silently degrading to text-only copy.

^{Macroscope summarized 025f7ff.}

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[macroscopeapp]

One interaction regression found in the new clipboard path. See the inline comment.

^{Posted via Macroscope — UI Consistency}

[cursor]

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

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^{Reviewed by Cursor Bugbot for commit 2cd1af3. Configure here.}

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This change introduces a new rich-clipboard workflow that fetches and normalizes attached images before writing them alongside prompt text. Its browser API, asynchronous image-processing, and fallback behavior create meaningful runtime surface area beyond a simple copy bug fix.

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