Copilot Tab Breaks Pylance Function Annotations Until Reload

[bilgilendir]

Does this issue occur when all extensions are disabled?: No

• VS Code Version: 1.98.2
• OS Version: Darwin arm64 24.3.0

Steps to Reproduce:

1. Open a Python file in VS Code with the Pylance extension enabled.
2. Hover over a function to see its annotations (works as expected).
3. Open the GitHub Copilot tab and ask about the file.
4. Switch back to the Python file and try to see function annotations again.
5. Annotations no longer appear.
6. Reloading the window (Developer: Reload Window) restores functionality.

Expected Behavior:

Opening the Copilot tab should not break Pylance's function annotations in Python files.

Actual Behavior:

After opening the Copilot tab, Pylance stops displaying function annotations in the editor until the window is reloaded.

Logs:

[Info] Pylance language server started
[Info] Function annotations working...
[Info] Copilot tab opened
[Error] File or directory "vscode-chat-code-block://..." does not exist.
[Info] No source files found.

[rchiodo]

What's your version of Pylance? I can't reproduce the issue myself.

HoverInChat.mp4

Do you see this in your Python Language Server output?

TypeError: Cannot read properties of undefined (reading 'registerRelatedFilesProvider')

That was a bug fixed recently that might be causing your issue.

[bilgilendir]

I have updated both VS Code and all extensions to their latest versions. There are no available updates, and I am using the latest macOS version.

Pylance Version:
Version: 2025.4.1
Last Updated: 2025-04-05, 21:05:47

Reproducing the Issue:
I opened a simple Python file with multiple functions.

Hovering over a function, such as a print function, displays its annotation as expected.

I then opened the GitHub Copilot tab.

I selected a function and asked Copilot to reformat or rewrite it.

After Copilot completes the task, I hover over the code within the Copilot tab, and the annotation appears there.

However, once I switch back to the editor, the function annotations no longer appear in the code, and the language server seems to be inactive.

Expected Behavior:
Opening the Copilot tab should not break the function annotations in the editor. It seems like the language server in the editor is getting disrupted.

Annoying Workaround:
After closing the Copilot tab and reloading the window, the annotations return.

[rchiodo]

Can you include the log output as described here? I cannot reproduce your issue and the log should tell us what happened.

https://github.com/microsoft/pylance-release/blob/main/TROUBLESHOOTING.md#filing-an-issue

[mgrundie-r7]

I experienced this issue also. As @bilgilendir described 'Developer: reload window' worked for me. I should note I can't replicate it by reopening the copilot chat window. So I'm not sure what actually causes this.

I also see File or directory "vscode-chat-code-block://.../" does not exist. in the Python Language Service log