Claude Opus 4.1 in VS Code Copilot Chat returns “Sorry, no response was returned” but differs from meta issue #253126 (Claude Sonnet 4 works fine in the same environment)

[Firstmeridian]

This issue appears related to #253126 (chat-no-response) but differs in the following ways:
Claude Sonnet 4 works fine in the same environment.
Quota is still deducted despite the failed response.

• Copilot Chat Extension Version: 0.31.2
• VS Code Version: 1.104.1
• OS Version: Windows 11 25H2
• Feature: ask mode
• Selected model: Claude Opus 4.1

Steps to Reproduce:

1. Open VS Code with GitHub Copilot Chat extension installed.
2. Sign in with a Copilot Pro+ account.
3. Select Claude Opus 4.1 from the model picker and confirm selection.
4. Enter a prompt that should return a multi‑paragraph answer.
5. Observe that the output is truncated and then displays “Sorry, no response was returned”.
6. Check quota usage — it decreases despite the failed response.

Expected Behavior:
Claude Opus 4.1 should return the full output without truncation or error, and failed responses should not consume quota.

Actual Behavior:
Output is truncated and then displays “Sorry, no response was returned”, and quota is still deducted.
But Claude Sonnet 4 works fine in the same environment.

[vs-code-engineering]

Please look at the following meta issue: #253126. Please refer to that issue for updates and discussions. Feel free to open a new issue if you think this is a different problem.

[Firstmeridian]

This issue appears to be different from the one the bot linked. It may be a false positive in the bot’s classification. It feels odd to open yet another issue, as the bot suggests.