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zen/go: mimo-v2.5 tool calls return 400 (Provider returned error) #43481
Description
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 = truefor 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).
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github-actions commentedon Aug 19, 2026
This issue might be a duplicate of existing issues. Please check:
toolsfrom the request fixes the error for MiMo on zen/go, which matches exactlygithub-actions commentedon Oct 19, 2026
To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.