zen/go: mimo-v2.5 tool calls return 400 (Provider returned error)

Problem

mimo-v2.5 on the zen/go endpoint fails when the request includes tools. Any request with a tools array → 400:

{"error":{"type":"server_error","message":"Error from provider (Console Go): Upstream request failed: [400] Provider returned error"}}

Without tools, the same request succeeds.

Repro

POST https://opencode.ai/zen/go/v1/messages with x-api-key:

{
  "model": "mimo-v2.5",
  "max_tokens": 1024,
  "messages": [{"role": "user", "content": [{"type": "text", "text": "hi"}]}],
  "tools": [{
    "name": "bash",
    "description": "Run a shell command",
    "input_schema": {"type": "object", "properties": {"cmd": {"type": "string"}}, "required": ["cmd"]}
  }]
}

→ 400. Remove tools → 200.

Confirmed independent of streaming, thinking, system prompt, and message shape (string or array content). The failure is triggered solely by the presence of tools.

Notes

• models.dev lists tool_call = true for opencode-go/mimo-v2.5, so this looks like an upstream Console Go deployment issue, not a model limitation.
• Other zen/go models (deepseek-v4-flash, etc.) handle tools fine on the same endpoint.
• This makes mimo-v2.5 unusable as an agent model (Hermes / Claude Code / any tool-using client).