Request failed due to a transient API error. Retrying... using the Claude Opus 4.6 model

[zhfrn-zzz]

Describe the bug

I'm using Claude Opus 4.6 (High) in Copilot CLI. I asked it to create a plan. When it explores the codebase using a subagent, everything works fine, but when it tries to write the plan to the /doc folder, an error always appears:
"Request failed due to a transient API error. Retrying..."

● Now I have a complete understanding. Let me write the detailed plan.

● Request failed due to a transient API error. Retrying...

● Request failed due to a transient API error. Retrying...

● Request failed due to a transient API error. Retrying...

● Request failed due to a transient API error. Retrying...

● Request failed due to a transient API error. Retrying...

✗ Execution failed: Error: Failed to get response from the AI model; retried 5 times (total retry 
wait
   time: 88.20631920058639 seconds) Last error: CAPIError: 503 {"error":{"message":"HTTP/2 GOAWAY 
  connection terminated","type":"connection_error"}} 

I’ve tried this four times now, and the error keeps happening. My premium requests are still being counted. I’ve tried running /update, using a new terminal, restarting Windows, and trying a different network, but the result is still the same.

Affected version

GitHub Copilot CLI 1.0.9.

Steps to reproduce the behavior

1. Open Copilot CLI in the terminal
2. /model
3. Select Claude Opus 4.6 (High)
4. Enter a prompt

Expected behavior

Claude Opus was supposed to write the plan.

Additional context

System Operation: Windows 11

[Lyve1981]

Same here, it started this week and gets worse every day

[MaxCHL]

The issue is the same when using other models as well, such as Claude Sonnet 4.6.

[Centurybbx]

I have encountered this issue as well. In my case, this scenario primarily occurs during write operations; the error appears specifically when writing, whereas reading and calling sub-agents work normally. Moreover, the issue is reproducible almost 100% of the time, which significantly degrades my experience.