OpenAI ChatGPT Plus OAuth Token Exchange Failed with 403

[mumudog-16]

Description

When trying to connect ChatGPT Plus subscription via OAuth in OpenCode, the browser authentication succeeds and redirects to http://localhost:1455/auth/callback?code=...&state=..., but OpenCode fails to save the credentials. The log shows Token exchange failed: 403 failed. After restarting OpenCode, no OpenAI models appear in the model list.

Additional Context

• Browser shows successful redirect to http://localhost:1455/auth/callback?code=...
• OAuth server on port 1455 is running correctly
• The issue persists even with proxy completely disabled (unset ALL_PROXY)
• auth.json only contains other providers (zenmux, opencode, streamlake, google) but no OpenAI entry

Plugins

No response

OpenCode version

1.2.10

Steps to reproduce

1. Run /connect in OpenCode TUI
2. Select OpenAI provider
3. Select ChatGPT Plus/Pro option
4. Complete browser authentication (login succeeds, redirect to localhost callback URL)
5. OpenCode shows no success message, no "✓ Login successful" popup
6. Check ~/.local/share/opencode/auth.json - no OpenAI credentials saved
7. Restart OpenCode, run /models - no OpenAI models available

Screenshot and/or share link

No response

Operating System

macOS

Terminal

Terminal

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• opencode connect OpenAI fails!!! #7992: Same symptom — browser authentication completes but OpenCode fails to save credentials / no models appear after reconnect
• OpenAI ChatGPT Pro/Plus (browser) cant be connected, Failed to start server. #14276: Related — ChatGPT Plus/Pro OAuth flow via /connect fails at the port 1455 callback stage

If your issue is distinct (specifically the 403 token exchange error rather than a server startup or silent auth failure), please add details clarifying the difference.

[mumudog-16]

Just turn on the enhanced mode of the agent.