Summary

• Replace base64 DataTransfer injection with CDP DOM.setFileInputFiles for image upload in xiaohongshu publish
• Chrome reads files directly from local filesystem — no base64 encoding, no payload size limits
• Graceful fallback to legacy base64 method for older extension versions
• Clear warning message when base64 fallback encounters large payloads (>500KB)

Problem

When publishing with images larger than ~500KB, the base64-encoded payload sent through page.evaluate() → sendCommand('exec') exceeds the browser bridge message channel limits, causing a cryptic TypeError: fetch failed with no useful error context. Users have no idea the issue is image size.

Solution

Use CDP DOM.setFileInputFiles (the same mechanism Playwright/Puppeteer use internally) to set file paths directly on the <input type="file"> element. Chrome reads the files from disk — zero base64 overhead.

Files changed:

• extension/src/protocol.ts — add set-file-input action type
• extension/src/cdp.ts — add setFileInputFiles() using DOM.getDocument → DOM.querySelector → DOM.setFileInputFiles
• extension/src/background.ts — add handleSetFileInput dispatcher
• src/browser/daemon-client.ts — extend DaemonCommand with files and selector fields
• src/browser/page.ts — add Page.setFileInput() method
• src/types.ts — add optional setFileInput to IPage interface
• src/clis/xiaohongshu/publish.ts — rewrite uploadImages() with CDP primary + base64 fallback

Backward compatibility

• setFileInput is optional on IPage — no breaking change for other adapters
• If the extension returns "Unknown action", publish falls back to the original base64 method automatically
• The base64 fallback now warns when total payload exceeds 500KB

Test plan

• Publish with a large image (>500KB PNG) — should succeed without compression
• Publish with a small image (<100KB JPEG) — should also work via CDP path
• Publish with an older extension version — should fall back to base64 gracefully
• Publish with multiple images — verify all are uploaded
• Verify TypeScript compiles cleanly (npx tsc --noEmit passes)

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