🐛 Bug Report — WebSocket Client Connection Hangs

[preschian]

What versions & operating system are you using?

wrangler@^4.42.2

Please provide a link to a minimal reproduction

https://github.com/preschian/test-workers-assethub-kusama

Describe the Bug

WebSocket Client Connection Hangs in Cloudflare Workers

Summary

WebSocket client connections hang indefinitely in Cloudflare Workers when connecting to certain endpoints (Kusama Asset Hub), while others work fine (Polkadot Asset Hub), despite using identical code and both endpoints being publicly accessible.

Important: This code has been working fine for years, but suddenly started hanging around October 6th, 2025. No changes were made to our code - this appears to be a Workers runtime regression.

Reproduction

git clone https://github.com/preschian/test-workers-assethub-kusama
cd test-workers-assethub-kusama
bun install
bun run dev

Then test:

• curl http://localhost:8787/polkadot ✅ Works fine
• curl http://localhost:8787/kusama ❌ Hangs indefinitely

Expected vs Actual

• Expected: Connection succeeds or throws clear error
• Actual: Hangs indefinitely with no error, no timeout, no response

Question

Why does one WebSocket endpoint work while structurally identical ones hang? Both Polkadot and Kusama use the same technology (Substrate framework).

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Repository: https://github.com/preschian/test-workers-assethub-kusama

Please provide any relevant error logs

No response