fix: handle CORS preflight requests for /api/metrics#2
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simonCatBot merged 6 commits intomasterfrom Apr 11, 2026
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April 11, 2026 10:40
The browser was sending a CORS preflight OPTIONS request before the GET request. In standalone mode, Next.js wasn't handling the preflight, causing 'NetworkError when attempting to fetch resource'. - Add OPTIONS handler that returns proper CORS headers - Add Access-Control headers to GET response - Add Access-Control headers to error response
The Image component had width=80 and height=32 but CSS set h-8 (32px), creating a mismatch. Added inline style 'width: auto' to maintain aspect ratio and suppress the browser warning.
- Add loading='eager' to logo.svg as it's above the fold (LCP element) - Change ROCm image from w-auto to w-8 to keep width/height symmetric
React Strict Mode double-invokes effects in development, causing concurrent fetches that can result in NetworkError. This change: - Uses useRef to track AbortController - Cancels any pending request before starting a new one - Adds 5s timeout for fetch to prevent hanging - Cleans up controller on unmount
Using relative URL '/api/metrics' may cause issues in some deployment configurations. Switch to absolute URL to ensure the fetch always goes to the correct origin. Also improved error logging to capture error name and message for better debugging.
Explicitly set fetch mode to same-origin to prevent any potential CORS preflight issues. Added cache: no-store to prevent response caching issues with streaming.
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Summary
Fixed the browser error:
NetworkError when attempting to fetch resourcethat appeared in the console when the dashboard tried to fetch metrics.Root Cause
The browser sends a CORS preflight OPTIONS request before the actual GET request. In Next.js standalone deployment mode, the preflight was not being handled, causing the fetch to fail with a NetworkError.
Fix
OPTIONShandler toapp/api/metrics/route.tsthat returns proper CORS headersAccess-Control-Allow-Origin: *,Access-Control-Allow-Methods: GET, OPTIONS, andAccess-Control-Allow-Headers: Content-Typeheaders to the GET responseTesting
Logs
Before (browser console):
Server logs showed 200 responses but browser still got errors due to failed preflight.