High CPU after update: cpptools repeatedly retries LanguageModelProxy model resolution in Remote-WSL extension host

[ariesfans]

Environment

• VS Code Remote: WSL
• Host OS: Windows + WSL2 (Ubuntu)
• VS Code Server commit: 0870c2a0c7c0564e7631bfed2675573a94ba4455
• C/C++ extension version: ms-vscode.cpptools 1.30.5 (linux-x64)
• Workspace type: mixed monorepo (not primarily C/C++)

Bug Summary and Steps to Reproduce

Problem

After updating, VS Code extension host CPU became abnormally high.
The issue appears tied to cpptools repeatedly trying to resolve language models through LanguageModelProxy.

Observed behavior:

• extensionHost process CPU stays elevated (continuous activity, no idle)
• cpptools-related processes are active
• logs are flooded with repeated warnings:
• LanguageModelProxy](ms-vscode.cpptools) Could not find model 'copilot/...'. Trying to resolve model again.

Evidence

From remoteexthost.log:

• Repeated lines like:
• Could not find model 'copilot/claude-haiku-4.5' in local cache. Trying to resolve model again.
• Could not find model 'copilot/gpt-4.1' in local cache. Trying to resolve model again.
• Could not find model 'copilot/gpt-4o' in local cache. Trying to resolve model again.
• Could not find model 'copilot/auto' in local cache. Trying to resolve model again.

Frequency observed:

• ~30k+ total repeated warnings in one log session
• ~1.9k warnings in a short recent tail sample

Repro (what happened)

1. Update VS Code / Remote server.
2. Open Remote-WSL workspace.
3. cpptools activates.
4. extension host starts high-frequency model-resolution retries (warning spam + CPU increase).

Temporary Mitigation

Disabling cpptools in remote WSL immediately reduced CPU usage.

(renamed extension dir to disable and restarted extension host)

Expected

cpptools should not continuously retry model resolution in a tight loop when models are unavailable/unresolvable.
It should back off aggressively or stop retrying after bounded attempts.

Additional note

This looks like a retry/backoff regression or integration mismatch between cpptools LanguageModelProxy usage and current model cache/availability in Remote-WSL.

Configuration and Logs

/root/.vscode-server/extensions/ms-vscode.cpptools-1.30.5-linux-x64.disabled-20260305-174449

I disabled it

Other Extensions

No response

Additional context

No response

[sean-mcmanus]

@ariesfans I don't know what "LanguageModelProxy" is. If you search our open source repo, you won't find us calling it. I'm guessing the GitHub Copilot code might be calling it indirectly and then blaming our extension.

[sean-mcmanus]

@ariesfans Yeah, the "LanguageModelProxy" is from VS Code. Does setting C_Cpp.copilotHover to "disabled" fix it?

[ariesfans]

@sean-mcmanus Thanks for the clarification, Sean.
I actually did was disable the C/C++ extension by renaming its extension folder to:
ms-vscode.cpptools-1.30.5-linux-x64.disabled-20260305-174449
At the moment, CPU high usage is not reproducing.

[sean-mcmanus]

@ariesfans Yeah, but if you do that then we're not able to diagnose if the C_Cpp.copilotHover feature is the cause or not. We think this is a bug with the VS Code implementation of Copilot that just happens to repro due to our extension calling into that.

[ariesfans]

@sean-mcmanus Right, I suspect this is most likely an issue with VS Code itself too, as the extremely high CPU usage only started occurring after I updated the application yesterday. I will report this issue to the VS Code team.

Version: 1.110.0 (user setup)
Commit: 0870c2a0c7c0564e7631bfed2675573a94ba4455
Date: 2026-03-04T01:20:28.863Z
Electron: 39.6.0
ElectronBuildId: 13330601
Chromium: 142.0.7444.265
Node.js: 22.22.0
V8: 14.2.231.22-electron.0
OS: Windows_NT x64 10.0.26200

[sean-mcmanus]

@ariesfans You should probably add in your bug report that the C/C++ extension doesn't believe we're at fault, since they've been closing other similar issues as being caused by our extension.

[ariesfans]

@sean-mcmanus I will

[bdoyle8]

I have encountered this error, and it goes away when I disable GitHub Copilot Chat in the workspace.

[sean-mcmanus]

@bdoyle8 @ariesfans There is a VS Code bug open at microsoft/vscode#298401 .