diff --git a/run_agent.py b/run_agent.py
index 4f50cb06e4d..590742b2da0 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -10049,11 +10049,12 @@ class AIAgent:
 
         DeepSeek v4 thinking and Kimi / Moonshot thinking both reject replays
         of assistant tool-call messages that omit ``reasoning_content`` (refs
-        #15250, #17400).
+        #15250, #17400). Xiaomi MiMo thinking mode has the same requirement.
         """
         return (
             self._needs_deepseek_tool_reasoning()
             or self._needs_kimi_tool_reasoning()
+            or self._needs_mimo_tool_reasoning()
         )
 
     def _needs_kimi_tool_reasoning(self) -> bool:
@@ -10085,6 +10086,22 @@ class AIAgent:
             or base_url_host_matches(self.base_url, "api.deepseek.com")
         )
 
+    def _needs_mimo_tool_reasoning(self) -> bool:
+        """Return True when the current provider is Xiaomi MiMo thinking mode.
+
+        MiMo thinking mode requires ``reasoning_content`` on every assistant
+        tool-call message when replaying history; omitting it causes HTTP 400.
+        Refs: https://platform.xiaomimimo.com/docs/zh-CN/usage-guide/passing-back-reasoning_content
+        """
+        provider = (self.provider or "").lower()
+        model = (self.model or "").lower()
+        return (
+            provider == "xiaomi"
+            or "mimo" in model
+            or base_url_host_matches(self.base_url, "api.xiaomimimo.com")
+            or base_url_host_matches(self.base_url, "xiaomimimo.com")
+        )
+
     def _copy_reasoning_content_for_api(self, source_msg: dict, api_msg: dict) -> None:
         """Copy provider-facing reasoning fields onto an API replay message."""
         if source_msg.get("role") != "assistant":