grok-4.5 on opencode go not working since 2 Aug

### Description

grok-4.5 has been returning errors since 2 Aug.

### Plugins

NA

### OpenCode version

v1.18.11

### Steps to reproduce

Call grok-4.5 on opencode go via openai chat completions api, response is always 500.

### Screenshot and/or share link

NA

### Operating System

Windows 11

### Terminal

Windows Terminal