OpenCode Go: "socket connection was closed unexpectedly" / "unknown certificate verification error" on all models

Description

I'm currently unable to use any model through the OpenCode Go provider.

The issue affects multiple models, not just DeepSeek. For example:

• deepseek-v4-flash → socket connection was closed unexpectedly
• gpt-5.6-luna → socket connection was closed unexpectedly
• gpt-5.6-luna also intermittently returns "unknown certificate verification error"

The relevant error from the OpenCode log is:

AI_APICallError: Cannot connect to API: The socket connection was closed unexpectedly. For more information, pass verbose: true in the second argument to fetch()

I also got this more specific error:

Error: unknown certificate verification error

This happens consistently with the opencode-go provider.

I tested HTTPS connectivity to opencode.ai directly using curl, and the connection succeeds with HTTP/2 200, so general HTTPS/TLS connectivity from my Mac appears to be working.

There are also no proxy-related environment variables configured.

Plugins

None

OpenCode version

1.18.18

Steps to reproduce

1. Open OpenCode 1.18.18.
2. Use the OpenCode Go provider.
3. Select any available model (tested with deepseek-v4-flash and gpt-5.6-luna).
4. Send any prompt.
5. The request fails with:
   "Cannot connect to API: The socket connection was closed unexpectedly"
6. Retrying eventually produces:
   "unknown certificate verification error"

Screenshot and/or share link

No response

Operating System

macOS (Apple Silicon)

Terminal

vsc extension