Fix BYOK Quota exceeded caused by Intent Detection with Copilot model

[fvclaus]

Fixes microsoft/vscode#251944

Issue

Currently, the intent detection is hard-coded to use the copilot gpt-4o-mini model. This is an issue when you have exceeded your chat quota.

This will result in either one of the two errors

Sorry, your request failed. Reason: Canceled

This is caused after the BYOK Chat Request returns with a 200. The code will reset the copilot token, because it doesn't check that it originated from the Copilot API

if (response.status === 200 && authenticationService.copilotToken?.isFreeUser && authenticationService.copilotToken?.isChatQuotaExceeded) {
		authenticationService.resetCopilotToken();
}

This also causes unnecessary network requests

The second error I have seen (on possibly older versions of the plugin) is the Quota exceeded error

Solution

I have tried to fix it in a way that is extensible later on

• Decouple the intent models from the regular models (although they are currently the same, this leaves the option to change it later)
• Design the API of the new service in a way so that the intent detection model can be set per language model (currently it is only one intent detection model for all models)
• The simplest fix would have been to use the current model of the Chat Request for intent detection, but that is potentially wasteful with expensive models and this isn't transparent to the user that another API request is sent behind the scenes
• Not mix the BYOK Code with the other code, so I made the BYOK code register its models on startup at the new service
• For all copilot models gpt-4o-mini is still used. I incorporated this into the message of the quick pick for users who want to have the same behaviour as before
• I didn't want to mix intent detection with a copilot model with a chat request with a BYOK model, because this is makes it more complicate and hard to reason about the different states of the system

With this MR there is an error message the first time a BYOK model is used

The button opens a quick pick

[fvclaus]

I have moved the new service to common to fix the test. vscode dependencies are imported dynamically. Maybe there is a better way. The tests run fine in my repo now.

[fvclaus]

I have released the code. You can download it from here: https://github.com/fvclaus/vscode-copilot-chat/releases/tag/v0.29.0-byok-fix-v1

To install it, go to settings, click on the three dots and select "Install from VSIX..."