bug(opencode-go): All subscription models return "Request blocked by upstream provider"

Description

Describe the bug

After logging in with opencode-go subscription, every model call uniformly throws error:
Request blocked by upstream provider.
No single model under opencode-go subscription can complete any chat/completion request.

Steps to reproduce

1. Install latest opencode release
2. Run opencode TUI, execute /login
3. Select opencode-go subscription auth flow, complete login normally
4. Switch any model under opencode-go provider
5. Send any prompt to trigger model inference
6. Error pops up immediately without any response content

Expected behavior

All subscribed opencode-go models should normally complete LLM inference requests without upstream block error.

Actual behavior

Every model request returns identical error message:
Request blocked by upstream provider.
No logs with detailed upstream status code, no retry logic takes effect.

Environment

• OS:
• OpenCode version: opencode --version
• Bun version: bun --version
• Network: Direct connection / proxy

Additional context

1. All models under opencode-go subscription are affected; no single model works.
2. No rate limit prompt, no API key expired reminder, only upstream block message.
3. Cleared local auth cache ~/.local/share/opencode and re-login multiple times, issue persists.
4. Other third-party API key providers (openai compatible) work fine, only opencode-go subscription auth is blocked upstream.
5. No custom modified config, default opencode.json with zero custom provider overrides.

Verification I've completed

• Searched existing open issues for identical Request blocked by upstream provider bug, no duplicate ticket found
• Cleared local auth storage and re-authenticated opencode-go subscription
• Tested multiple different opencode-go models to confirm full provider-wide block
• Confirmed network connectivity to other AI API providers works normally
• Did not use AI-generated bulk text, all descriptions written manually

Plugins

No response

OpenCode version

v1.18.4

Steps to reproduce

No response

Screenshot and/or share link

No response

Operating System

No response

Terminal

No response