Browser trace showed fallback-dev cascade failing with 'Failed to
fetch' on the live site. dev.flow-master.ai OPTIONS preflight returns
HTTP 400 from foreign origins and the POST response lacks
Access-Control-Allow-Origin, so the browser blocks direct
cross-origin calls.
Add nginx location /api/llm-fallback/ that rewrites to
/api/v1/llm/ and proxies to dev.flow-master.ai (same DNS resolver
pattern as the demo proxy). Frontend now hits both gateways
same-origin via canvas.flow-master.ai, no CORS preflight needed.
The canvas-issued JWT is forwarded as-is and dev accepts it
(verified by curl).
