diff --git a/astrbot/core/provider/sources/openai_source.py b/astrbot/core/provider/sources/openai_source.py
index 117cfb4922..c578e26d28 100644
--- a/astrbot/core/provider/sources/openai_source.py
+++ b/astrbot/core/provider/sources/openai_source.py
@@ -560,7 +560,36 @@ def _is_empty(content: Any) -> bool:
 
             cleaned.append(msg)
 
-        payloads["messages"] = cleaned
+        # Drop orphaned tool messages whose assistant(tool_calls) was
+        # removed by context truncation / compression, preventing
+        # 400 "unexpected tool_use_id in tool_result" from the API.
+        valid_tc_ids = set()
+        final: list = []
+        _orphan_count = 0
+        for msg in cleaned:
+            if not isinstance(msg, dict):
+                final.append(msg)
+                continue
+            role = msg.get("role")
+            if role == "assistant" and msg.get("tool_calls"):
+                valid_tc_ids = {
+                    tc["id"]
+                    for tc in msg["tool_calls"]
+                    if isinstance(tc, dict) and "id" in tc
+                }
+                final.append(msg)
+            elif role == "tool":
+                if msg.get("tool_call_id") in valid_tc_ids:
+                    final.append(msg)
+                    valid_tc_ids.discard(msg.get("tool_call_id"))
+                else:
+                    _orphan_count += 1
+            else:
+                valid_tc_ids = set()
+                final.append(msg)
+        if _orphan_count:
+            logger.debug("Filtered %d orphaned tool message(s)", _orphan_count)
+        payloads["messages"] = final
 
     async def _query(self, payloads: dict, tools: ToolSet | None) -> LLMResponse:
         if tools: