[Bug]: OpenCode 1.2.15 crashes on startup with panic: invalid enum value on Windows 11 (Bun 1.3.10) #15283

Description

OpenCode 1.2.15 crashes immediately on startup with a Bun panic invalid enum value. The TUI never renders — it exits with code 3 right after launch.

This is NOT the ThreadLock panic fixed in v1.2.15 (#15127). It's a different Bun crash (invalid enum value) that persists even after the ThreadLock fix.

Environment

• OpenCode version: 1.2.15 (latest via npm i -g opencode-ai@latest)
• Bun version: 1.3.10 (bundled with opencode-windows-x64)
• OS: Windows 11 Home (10.0.26200.7922)
• Architecture: x86_64
• Terminal: Windows Terminal / Git Bash (MSYS2)

Steps to Reproduce

1. Install OpenCode on Windows: npm i -g opencode-ai@latest (v1.2.15)
2. Create a minimal config at ~/.config/opencode/opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "model": "google/antigravity-gemini-3-flash",
  "provider": {
    "google": {
      "name": "Google",
      "models": {
        "antigravity-gemini-3-flash": {
          "name": "Gemini 3 Flash",
          "limit": { "context": 1048576, "output": 65536 }
        }
      }
    }
  },
  "plugin": ["opencode-antigravity-auth@latest"],
  "autoupdate": false
}

3. Run opencode in any directory
4. TUI crashes immediately — exits with code 3

Crash Output

The Bun panic output shows:

panic(thread): invalid enum value
Build ID: ea130e609e
OS: x86_64 windows msys

Full Bun crash report URL:

https://bun.report/1.3.10/ea130e609emxGz/3/9/Dkj2hKyn0sGgxiL0k54Jgi++MCY

Investigation

• Empty config also crashes: Tested with {} config — same crash.
• Piped output does NOT crash: opencode 2>&1 | cat does NOT crash because the TUI is disabled when stdout is not a terminal. This makes debugging misleading.
• Server mode works: The crash is specifically in the TUI rendering path, not in the server/core logic.
• This is a Bun bug: Related to oven-sh/bun#14844 — same invalid enum value panic on Windows. The underlying cause appears to be in Bun's terminal/TUI handling on Windows.
• Not the ThreadLock bug: Issue Bun crash when .env file contains any content (ThreadLock panic) #15127 reports a ThreadLock panic which was fixed in v1.2.15. This is a different crash signature (invalid enum value vs ThreadLock).

Expected Behavior

OpenCode TUI should start and render normally.

Actual Behavior

OpenCode exits immediately with code 3 and a Bun panic. No TUI is ever displayed.

Workaround

None currently. OpenCode is completely unusable on this Windows machine.

Additional Context

• Previous OpenCode versions (0.15.x) worked on this same machine with the same Bun setup.
• The crash happens with any model/provider configuration, even an empty config.
• The bundled opencode-windows-x64 binary includes Bun 1.3.10 which cannot be updated independently.