Problem

The plugin's error handling doesn't follow the patterns used by OpenCode's official auth plugins (opencode-copilot-auth, opencode-anthropic-auth), causing errors to display incorrectly in the OpenCode UI.

Current behavior

1. Token refresh failures return a Response object instead of throwing an error:

   return {
     success: false,
     response: new Response(JSON.stringify({ error: "Token refresh failed" }), { status: 401 }),
   };

2. API error responses are consumed, enriched with custom JSON, and returned as a new Response - this interferes with OpenCode's AI SDK error handling:

Impact

• Error messages persist incorrectly in the UI
• Rate limit errors may display as raw JSON instead of user-friendly messages
• Errors don't integrate with OpenCode's retry logic (isRetryable flag)

Expected behavior

Based on opencode-copilot-auth (lines 88-89):

if (!response.ok) {
  throw new Error(`Token refresh failed: ${response.status}`);
}

• Token refresh failures should throw errors (OpenCode catches these and displays them properly)
• API error responses should be returned as-is (OpenCode's AI SDK converts HTTP errors to APICallError → MessageV2.APIError)

References

• OpenCode error handling: packages/opencode/src/session/message-v2.ts:fromError()
• Official plugin pattern: opencode-copilot-auth/index.mjs:88-89