GitHub Copilot models not appearing in /models after successful OAuth authentication #38812

Description

Description:

OS: Windows 11 (PowerShell)
OpenCode version: v1.18.5 (latest)
Steps to reproduce:

Run /connect in the TUI
Select "GitHub Copilot" and complete the device flow at github.com/login/device
Authentication succeeds — auth.json stores the OAuth token correctly
Run /models — only big-pickle appears, no copilot models listed
Tried re-authenticating, clearing auth.json, clearing models.json cache — same result
What I expected: Copilot models (e.g., copilot/claude-sonnet-4.6, copilot/gpt-5.3-codex) should appear in /models after authentication.

What happened: No copilot models appear in the model picker. Also tried setting "model": "copilot/claude-sonnet-4.6" directly in opencode.jsonc but it doesn't work (provider doesn't seem to initialize).

Evidence:

~/.local/share/opencode/auth.json contains valid OAuth token for github-copilot
~/.cache/opencode/models.json lists 27 copilot models under github-copilot key
The provider simply doesn't surface in the TUI
Additional context: GitHub Copilot subscription is active (Pro/Pro+). Authentication flow completes without errors. The issue appears to be that the copilot provider doesn't initialize or register in the TUI despite having valid credentials and model data.

Plugins

No response

OpenCode version

No response

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response