Problem

Multi-turn MiMo (Xiaomi) reasoning-model conversations fail with HTTP 400:

The reasoning_content in the thinking mode must be passed back to the API.

Hermes already handles this requirement for DeepSeek and Kimi, but MiMo (api.xiaomimimo.com, model names containing mimo) was absent from the predicate, so _copy_reasoning_content_for_api never injected the required reasoning_content placeholder on replayed assistant turns.

Root cause

_needs_thinking_reasoning_pad() at line ~10101 only ORs DeepSeek and Kimi:

def _needs_thinking_reasoning_pad(self) -> bool:
    return (
        self._needs_deepseek_tool_reasoning()
        or self._needs_kimi_tool_reasoning()
    )

MiMo was never included.

Fix

Add _needs_mimo_tool_reasoning() and include it in the combined predicate.

flowchart TD
    A[_needs_thinking_reasoning_pad] --> B[_needs_deepseek_tool_reasoning]
    A --> C[_needs_kimi_tool_reasoning]
    A --> D[_needs_mimo_tool_reasoning]
    D --> E{base_url matches xiaomimimo.com?}
    E -- yes --> TRUE[return True]
    D --> F{"'mimo' in model.lower()?"}
    F -- yes --> TRUE
    E -- no --> F
    F -- no --> FALSE[return False]

Detection mirrors the DeepSeek/Kimi pattern: match on base URL hostname OR model name substring, covering both direct API access and custom-provider setups.

Tests

New tests/run_agent/test_mimo_reasoning_content_echo.py — 8 cases:

• Base URL api.xiaomimimo.com detected
• mimo-7b-thinking model name detected
• MiMo-VL-7B-RL (mixed-case) detected
• Unrelated provider not detected
• DeepSeek not detected as MiMo
• MiMo URL triggers _needs_thinking_reasoning_pad
• MiMo model name triggers _needs_thinking_reasoning_pad
• Unrelated provider skips pad

All 8 pass.

Closes #24443