GitHub Copilot provider fails silently on Linux (v1.18.13) — OAuth token missing copilot scope, no models registered

Description

Description
On Linux (Kali, ARM64, via npm install -g opencode-ai), the GitHub Copilot login flow (/connect → github) completes without any visible error, but the resulting OAuth token is never exchanged for a valid Copilot session token. As a result, opencode models lists zero github-copilot/* models, and forcing a model explicitly with -m github-copilot/ fails with a generic UnknownError.
The exact same GitHub account works correctly with OpenCode v1.14.33 on macOS — same account, same Copilot Student entitlement, fully functional. Downgrading to v1.14.33 on the same Linux machine fixes the issue completely, strongly suggesting a regression introduced between 1.14.33 and 1.18.13 specifically affecting the github-copilot provider's OAuth flow.

Environment
Broken: OpenCode v1.18.13, Kali Linux (ARM64, UTM/QEMU VM), installed via npm install -g opencode-ai
Working: OpenCode v1.14.33, macOS
Same GitHub account (Copilot Individual, Student educational quota) in both cases

Steps to reproduce (on v1.18.13 / Linux)
opencode → /connect → select GitHub → complete device flow in browser
Login appears to succeed (no error shown)
opencode models → no github-copilot/* entries appear in the list
opencode run -m github-copilot/claude-sonnet-4.5 "hi" → fails
Root cause (confirmed via manual diagnosis)
Inspecting ~/.local/share/opencode/auth.json after login:
json
"github-copilot": {
"type": "oauth",
"access": "gho_...",
"refresh": "gho_...", // identical to access
"expires": 0
}
access and refresh are identical — the raw GitHub OAuth token from the device flow, never exchanged for a real Copilot session token.
expires: 0 — no real expiry was ever set, confirming the exchange step never completed.
Checking the token's scope directly:
curl -sI -H "Authorization: token gho_..." https://api.github.com/user | grep -i scope
→ x-oauth-scopes: read:user
The device flow only requests read:user. It appears to never request whatever scope/authorization is needed for GitHub to allow the client_id used by OpenCode to call the Copilot token-exchange endpoint.
Confirmed the token itself is otherwise valid (/user returns correct account info, Copilot entitlement confirmed via /copilot_internal/user with a separately-generated fine-grained PAT — chat_enabled: true, cli_enabled: true, plan individual).
Calling the actual exchange endpoint manually with this token always returns 404:
curl -s -H "Authorization: token gho_..." https://api.github.com/copilot_internal/v2/token
→ {"message":"Not Found","documentation_url":"https://docs.github.com/rest","status":"404"}
This reproduced identically across two separate fresh logins (including after fully revoking the OAuth grant from GitHub's side and reconnecting from scratch) — not a one-off token issue.
For comparison, the official GitHub copilot CLI (installed via gh copilot) authenticates successfully and works out of the box on the same machine, same account — so this is not an account/entitlement/network problem, it's specific to how OpenCode's github-copilot provider performs its OAuth handshake in this version.
Fix / workaround

Downgrading resolves it completely:
bash
npm install -g opencode-ai@1.14.33
After re-running /connect, opencode models correctly lists the full github-copilot/* catalog (Claude Sonnet/Opus, GPT-5.x, Gemini, etc.) and inference works.
Expected behavior
The device-flow OAuth login for the github-copilot provider should request whatever scope/authorization GitHub requires, complete the token exchange automatically after login, and populate opencode models with the available Copilot models — as it does correctly in v1.14.33.

Plugins

No response

OpenCode version

1.18.13

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response