Vercel custom IDN domain returns HTTP 200 but response body stalls during download

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6

Hi team hope this helps!

Behavior

  • 200 OK returned

  • Response stalls at ~21 KB (expected ~154 KB)

  • No redirect loop

  • Reproducible by user (browser + curl)

  • .vercel.app works normally

Verification

  • When successful, both domains return identical content (same size, hash, headers)

  • Range requests work

  • DNS and deployment appear correct

  • Issue not globally reproducible

Interpretation

Likely edge-specific issue (region/POP/protocol), possibly:

  • HTTP/2 or HTTP/3 handling

  • cache inconsistency across edge nodes

  • punycode hostname routing/SNI differences

Helpful debugging data

  • Failing x-vercel-id

  • HAR file

  • Affected region/ISP

  • Whether HTTP/1.1 avoids the issue

Conclusion: not a project/config issue; likely isolated to specific edge nodes serving the custom IDN hostname.