Github Copilot Does not work

[DoraemonPanda]

After installing gihub copilot plugin it is not able to work

[msujew]

Hey @DoraemonPanda,

How did you even install the plugin, it's not available on open-vsx? Due to the terms of use of the Visual Studio marketplace, extensions downloaded from there cannot be legally installed into non-Microsoft products, i.e. everything aside from VS/VS Code/Codespaces cannot legally install the Copilot extension.

Since there is no legal way to install the plugin in Theia, we do not offer any support for it. Theia offers native AI integrations, see here. Alternatively, you can probably use other plugins, such as Tabnine or Cody.

[tmirza]

There is an extension on openvsx "copilot-for-vscode-oss" (https://open-vsx.org/extension/maxie-homrich/copilot-for-vscode-oss). Can I use that one?

[JonasHelming]

One more note: You can use the Github Copilot Subscription with the Theia native AI support, see: https://theia-ide.org/docs/user_ai/#github-copilot

[mireksobczak-bit]

Subject: GitHub Copilot Pro - "400 The requested model is not supported" for all models except GPT-4o in TheiaIDE

Description
I am currently on a GitHub Copilot Pro monthly trial and experiencing an issue where most available models fail to initialize in TheiaIDE, despite being active and visible in the configuration.

Environment
IDE: TheiaIDE
Subscription: GitHub Copilot Pro (Individual Trial)
Status: Correctly logged in (ID visible in the status bar), AI Support enabled in settings.

Steps to Reproduce
Navigate to AI Configuration [Beta] / Model Aliases.
Observe the list of available models (marked with ✓):
anthropic/claude-sonnet-4.5
copilot/claude-haiku-4.5
copilot/claude-opus-4.5
copilot/gemini-2.5-pro
copilot/gpt-5.2, etc.

Assign any of these models to a default alias (e.g., universal-system-default).
Attempt to use the AI features (Chat or Completion).

Expected Behavior
The assigned model should process the request, as they are all confirmed to work correctly under the same subscription in VS Code.

Actual Behavior
Every model except gpt-4o returns the following error:
400 The requested model is not supported.

This error persists regardless of which alias the model is assigned to. Only copilot/gpt-4o functions as expected.

Additional Context
I have verified that my subscription is active and all mentioned models are fully accessible when using the official GitHub Copilot extension in VS Code. It appears to be a specific compatibility or mapping issue within the TheiaIDE AI implementation or the way it handles Copilot Pro model permissions.

[ndoschek]

Hi @mireksobczak-bit,
We have an issue open here: eclipse-theia/theia-ide#675
We are currently investigating a better approach than providing a default list of models.

[mireksobczak-bit]

Thank you. I didn't found it.

[Pranav-0440]

Hi @ndoschek,

Thanks for pointing to #675 — I can confirm I’m experiencing the same behavior.

In my setup:

• GitHub Copilot Pro (Individual Trial) is active
• Login status is correct in Theia
• Models are visible under AI Configuration
• Only copilot/gpt-4o works successfully

All other models (e.g., claude-*, gemini-*, gpt-5.2) return:
400 The requested model is not supported

Since these models work correctly in VS Code under the same subscription, this does appear to be a model compatibility or mapping issue within Theia’s AI integration layer.

Happy to help test potential fixes if needed.