I tried setting up glm-5.2 as a model via the openrouter provider but was unable to get it to work.

Steps to reproduce

1. Launch coder with CODER_AI_GATEWAY_DUMP_DIR=/tmp/aibridge-dumps
2. Configure an OpenRouter provider
3. Configure z-ai/glm-5.2 as a model with the OpenRouter provider
4. Enable experimental chat debug logging for deployment
5. Enable experimental chat debug logging for user
6. Attempt to send a message via Coder Agents
7. Observe a somewhat useless error message from Coder Agents
8. Click into "Debug" tab
9. Click into one of the failed steps
10. Observe error bad gateway: unknown stream error: unexpected end of JSON input
11. Also observe the dump from AI Gateway

(some fields removed for brevity)

HTTP/2.0 200 OK
Content-Type: text/event-stream

: OPENROUTER PROCESSING

Possible Root cause

Based on the AI Gateway dump, we can assume the follow steps occur:

• We skip over the comment line : OPENROUTER PROCESSING
• An empty event is produced for the blank line
• Stream.Next() then attempts to unmarshal the empty bytes
• Somewhere in AI Gateway we hit this error branch

Impact

Any provider that emits SSE comment-only events (comment lines followed by blank lines with no data: field) will trigger this bug.