🐛 What happened?

Sending a chat message with gemini-4-argon-contributor (OpenCode Go provider) fails immediately with a 400 error: "Model does not support this protocol." Every message to this model fails.

🔄 Steps to reproduce

1. Open Copilot Chat and select gemini-4-argon-contributor from the OpenCode Go models in the model picker.
2. Send any message.
3. Observe the error: OpenCode Go API request failed (400) model=gemini-4-argon-contributor payloadBytes=122820: Model does not support this protocol.

✅ What did you expect?

The request should stream a response. If the model cannot be used with this protocol, it should not appear in the model picker, or the error should say which protocol is expected.

🖥️ Environment

• Extension version: 0.7.9
• VS Code version: 1.141.1
• Provider: OpenCode Go
• Model: gemini-4-argon-contributor

📸 Logs or screenshots (optional)

OpenCode Go API request failed (400) model=gemini-4-argon-contributor payloadBytes=122820: Model does not support this protocol. OpenCodeRequestError: OpenCode Go API request failed (400) model=gemini-4-argon-contributor payloadBytes=122820: Model does not support this protocol. at buildOpenCodeRequestError (...\ltmoerdani.opencode-copilot-chat-0.7.9\out\errors.js:40:12) at streamOpenCodeResponse (...\out\transports\engine.js:320:73) at streamChatCompletions (...\out\transports\chatCompletions.js:26:9) at OpenCodeProvider.provideLanguageModelChatResponse (...\out\provider\OpenCodeProvider.js:388:13)

OpenCode Go Diagnostics

Runtime

• extensionVersion: 0.7.9
• vscodeVersion: 1.141.1
• appHost: desktop
• remoteName: local
• uiKind: desktop
• extensionMode: production
• workspaceTrusted: true
• platform: win32
• architecture: x64
• nodeVersion: v24.21.0
• windowsIntegrity: medium (not elevated)
• extensionPath: c:\Users\Test.vscode\extensions\ltmoerdani.opencode-copilot-chat-0.7.9
• executablePath: C:\Users\Test\AppData\Local\Programs\Microsoft VS Code\Code.exe
• credentialInSecretStorage: true
• modelSelectionError: none

Recent Requests

1. gemini-4-argon-contributor

• time: 2026-10-14T12:29:56.951Z
• endpoint: chat-completions
• initiator: github.copilot-chat
• metadataSource: models.dev
• status: 400
• durationMs: 406
• ttfbMs: n/a
• totalBytes: 110
• totalEvents: 0
• tokens: prompt=n/a, completion=n/a, total=n/a, cached=n/a
• cacheHitRatio: n/a
• finishReason: n/a
• requestId: req-c293b163
• sessionId: vscode-b0f6855f
• url: https://opencode.ai/zen/go/v1/chat/completions
• error: OpenCode Go API request failed (400) model=gemini-4-argon-contributor payloadBytes=101728: Model does not support this protocol.