Claude Sonnet 4.5 Listed in "/models" but return 400 error

[Meredyk48]

Describe the bug

"Claude Sonnet 4.5 is listed in /model but returns 400 error when used"

I was using the model all day, then it simply stopped working and started displaying the following message after each request.

Full error Message:
"✗ Execution failed: CAPIError: 400 The requested model is not supported. (Request ID:EAA9:15725E:2CB259:3196D2:69D6A4D0)"

Affected version

v1.0.21

Steps to reproduce the behavior

1. Access the Copilot CLI.
2. /models to list the available models.
3. Select the Claude Sonnet 4.5 (default).
4. Make a request using the Claude Sonnet 4.5 model.
5. See the error.

Expected behavior

1. Access the Copilot CLI.
2. /models to list the available models.
3. Select the Claude Sonnet 4.5 (default).
4. Make a request using the Claude Sonnet 4.5 model.
5. Receive the Answer.

Additional context

No response

[daniloceano]

I’m seeing the same problem.

Environment:

• OS: Linux
• Client: VS Code
• Surface: Copilot CLI / Autopilot Preview
• copilot-cli version: 1.115

What I’m seeing:

• Claude Sonnet 4 -> fails with CAPIError: 400 The requested model is not supported
• Claude Sonnet 4.5 -> fails with the same error
• Claude Haiku 4.5 -> works normally in the same session

What I already tried:

• Sign out / sign in
• Reinstall Copilot extension
• Start a new session

This makes it look like the CLI is working, but Sonnet models are failing on this route/session.

[owenng71]

i am having the same issue now lmao. Are you using Copilot Student Pack?

[alfredoptarigan]

I am having the same issue, is it fixed now?

[xiaoshengyvlin]

一样，sonnet和opus模型用不了，学生包

[kaveendahelitha]

I'm also have same issues ,

[MrLogEN]

I have the same issue. I am on Github Education Plan

[rishbCLN]

same issue on the github education plan

[gmelvyn]

The weird thing is that it was working yesterday :(

[DimaFedor]

same issue on the github education plan

[Meredyk48]

I believe it's something related to the student plan.

After receiving access to the Organization, I only needed to execute the logout and login commands. After doing that, all the models displayed in the "/models" command listing are working normally.

[Uri-Tauber]

I also encounter this bug. I tried to logout/login like @Meredyk48 suggest, to no avail.
I also have student plan.

Full error message: ✗ Execution failed: CAPIError: 400 The requested model is not supported. (Request ID: 7EF8:147616:857B0D:925231:69D7A350

[hmorneau]

I think the answer is here: https://github.com/orgs/community/discussions/189268

"As part of this transition, however, some premium models, including GPT-5.4, and Claude Opus and Sonnet models, will no longer be available for self-selection under the GitHub Copilot Student Plan. "