After a WebSocket handler exits, flask-sock returns a Response to
Werkzeug which writes "HTTP/1.1 200 OK..." on the still-open socket.
Browsers see these HTTP bytes as a malformed WebSocket frame, causing
"Invalid frame header".
Now the handler explicitly closes the raw TCP socket after the
WebSocket close handshake, so Werkzeug's write harmlessly fails.
Applied to both waterfall and audio WebSocket handlers.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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