Bug: Silent failure when uploading large files (>70) to workspace via browser

[AlanAAG]

Summary

When uploading large files (observed with videos >70MB) to the workspace via the browser interface, the upload silently fails — no error message, no toast, no feedback of any kind. Files under ~70MB upload successfully. Files above that threshold (e.g. 100MB+ video) appear to be accepted by the UI but never land in the workspace.

Steps to Reproduce

1. Open the Workspace tab in the browser interface
2. Upload a small file (<70MB video) → uploads successfully
3. Upload a large file (100MB+ video) → nothing happens — no error, no progress, no confirmation

Expected Behavior

• Large file upload should either:
  • Succeed with visible progress feedback and a confirmation once done, OR
  • Fail gracefully with a clear user-facing error (e.g. "File too large" or "Upload timed out")

Actual Behavior

• The UI accepts the file selection silently
• No upload progress is shown
• No error is displayed
• No file appears in the workspace
• The user has zero indication of what went wrong

Root Cause Analysis

The file_upload WebSocket message handler in browser_adapter.py passes the entire file as a base64-encoded string in a single WS message payload (content_b64). For large files this causes:

1. Browser-side OOM / silent abort — the browser must read the entire file into memory as a base64 DataURL before sending. For 100MB+ files this can silently fail before the WS send even happens.
2. No client-side size guard — there is no check before attempting to encode and send; the operation just goes quiet.
3. Swallowed exceptions — the _handle_file_upload method's except block does not broadcast a file_upload_error event back to the frontend, so the UI never learns of the failure.

The WebSocket is initialized with max_msg_size=100 * 1024 * 1024 server-side, but the frontend assembly and encoding step fails well before that limit is reached for very large files.

Suggested Fix

• Add a client-side file size check before attempting to read/encode (configurable hard limit, e.g. 200MB, with a clear error message returned immediately).
• Switch large file uploads to chunked HTTP POST via a dedicated endpoint (e.g. /api/workspace/upload) instead of embedding the entire file in a WS message. aiohttp supports multipart/streaming natively.
• Always broadcast a file_upload_error event in the _handle_file_upload except block so the UI can surface the failure to the user.
• Add upload progress feedback (percentage or spinner) so the user knows the operation is in-flight for large files.

Environment

• File type tested: .mp4 video
• Working threshold: ~70MB
• Failing threshold: ~100MB+
• Interface: Browser (WebSocket via browser_adapter.py)

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Labels: bug, workspace, file-upload, ux