diff --git a/astrbot/core/provider/sources/gemini_source.py b/astrbot/core/provider/sources/gemini_source.py
index 0c58174897..cf43fa2f38 100644
--- a/astrbot/core/provider/sources/gemini_source.py
+++ b/astrbot/core/provider/sources/gemini_source.py
@@ -377,11 +377,10 @@ def append_or_extend(
                 append_or_extend(gemini_contents, parts, types.UserContent)
 
             elif role == "assistant":
-                if isinstance(content, str):
-                    parts = [types.Part.from_text(text=content)]
-                    append_or_extend(gemini_contents, parts, types.ModelContent)
+                parts = []
+                if isinstance(content, str) and content:
+                    parts.append(types.Part.from_text(text=content))
                 elif isinstance(content, list):
-                    parts = []
                     thinking_signature = None
                     text = ""
                     for part in content:
@@ -406,11 +405,10 @@ def append_or_extend(
                             thought_signature=thinking_signature,
                         )
                     )
-                    append_or_extend(gemini_contents, parts, types.ModelContent)
 
-                elif not native_tool_enabled and "tool_calls" in message:
-                    parts = []
-                    for tool in message["tool_calls"]:
+                tool_calls = message.get("tool_calls") or []
+                if not native_tool_enabled and tool_calls:
+                    for tool in tool_calls:
                         part = types.Part.from_function_call(
                             name=tool["function"]["name"],
                             args=json.loads(tool["function"]["arguments"]),
@@ -427,15 +425,16 @@ def append_or_extend(
                             if ts_bs64:
                                 part.thought_signature = base64.b64decode(ts_bs64)
                         parts.append(part)
-                    append_or_extend(gemini_contents, parts, types.ModelContent)
-                else:
+
+                if not parts:
                     logger.warning("assistant 角色的消息内容为空，已添加空格占位")
                     if native_tool_enabled and "tool_calls" in message:
                         logger.warning(
                             "检测到启用Gemini原生工具，且上下文中存在函数调用，建议使用 /reset 重置上下文",
                         )
                     parts = [types.Part.from_text(text=" ")]
-                    append_or_extend(gemini_contents, parts, types.ModelContent)
+
+                append_or_extend(gemini_contents, parts, types.ModelContent)
 
             elif role == "tool" and not native_tool_enabled:
                 func_name = message.get("name", message["tool_call_id"])
diff --git a/tests/test_gemini_source.py b/tests/test_gemini_source.py
index 4db8e92bfe..a9a1ca9c15 100644
--- a/tests/test_gemini_source.py
+++ b/tests/test_gemini_source.py
@@ -1,3 +1,5 @@
+import base64
+
 import pytest
 
 from astrbot.core.exceptions import EmptyModelOutputError
@@ -27,3 +29,103 @@ def test_gemini_reasoning_only_output_is_allowed():
         response_id="resp_reasoning",
         finish_reason="STOP",
     )
+
+
+def _make_gemini_provider_for_conversation():
+    provider = object.__new__(ProviderGoogleGenAI)
+    provider.provider_config = {
+        "gm_native_coderunner": False,
+        "gm_native_search": False,
+    }
+    return provider
+
+
+def _assistant_tool_call_message(content):
+    return {
+        "role": "assistant",
+        "content": content,
+        "tool_calls": [
+            {
+                "id": "call_1",
+                "type": "function",
+                "function": {
+                    "name": "get_pull_request_files",
+                    "arguments": '{"owner":"AstrBotDevs","repo":"AstrBot","pull_number":8742}',
+                },
+            },
+        ],
+    }
+
+
+def _first_model_parts(gemini_contents):
+    model_content = next(
+        content
+        for content in gemini_contents
+        if content.__class__.__name__ == "ModelContent"
+    )
+    return model_content.parts or []
+
+
+def test_prepare_conversation_keeps_assistant_text_and_tool_calls():
+    provider = _make_gemini_provider_for_conversation()
+    payloads = {
+        "messages": [
+            {"role": "user", "content": "summarize this PR"},
+            _assistant_tool_call_message("I will inspect the changed files first."),
+        ]
+    }
+
+    parts = _first_model_parts(provider._prepare_conversation(payloads))
+
+    assert any(part.text == "I will inspect the changed files first." for part in parts)
+    assert [
+        part.function_call.name
+        for part in parts
+        if getattr(part, "function_call", None)
+    ] == ["get_pull_request_files"]
+
+
+def test_prepare_conversation_keeps_assistant_list_content_and_tool_calls():
+    provider = _make_gemini_provider_for_conversation()
+    payloads = {
+        "messages": [
+            {"role": "user", "content": "summarize this PR"},
+            _assistant_tool_call_message(
+                [
+                    {
+                        "type": "think",
+                        "encrypted": base64.b64encode(b"signature").decode("utf-8"),
+                    },
+                    {"type": "text", "text": "I will inspect the changed files first."},
+                ]
+            ),
+        ]
+    }
+
+    parts = _first_model_parts(provider._prepare_conversation(payloads))
+
+    assert any(part.text == "I will inspect the changed files first." for part in parts)
+    assert [
+        part.function_call.name
+        for part in parts
+        if getattr(part, "function_call", None)
+    ] == ["get_pull_request_files"]
+
+
+def test_prepare_conversation_ignores_null_tool_calls():
+    provider = _make_gemini_provider_for_conversation()
+    payloads = {
+        "messages": [
+            {"role": "user", "content": "hello"},
+            {
+                "role": "assistant",
+                "content": "hello back",
+                "tool_calls": None,
+            },
+        ]
+    }
+
+    parts = _first_model_parts(provider._prepare_conversation(payloads))
+
+    assert [part.text for part in parts] == ["hello back"]
+    assert not any(getattr(part, "function_call", None) for part in parts)