diff --git a/tests/models/test_openai_mixed_stream.py b/tests/models/test_openai_mixed_stream.py
new file mode 100644
index 000000000..42e5e39e5
--- /dev/null
+++ b/tests/models/test_openai_mixed_stream.py
@@ -0,0 +1,266 @@
+# Tencent is pleased to support the open source community by making tRPC-Agent-Python available.
+#
+# Copyright (C) 2026 Tencent. All rights reserved.
+#
+# tRPC-Agent-Python is licensed under Apache-2.0.
+
+import json
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, Mock, patch
+
+import pytest
+from trpc_agent_sdk.models import LlmRequest, OpenAIModel
+from trpc_agent_sdk.models._openai_model import const
+
+
+async def collect(deltas, streaming_names=None, usage_only=True):
+    chunks = [{"id": "synthetic-response", "choices": [{"delta": delta, "finish_reason": None}]} for delta in deltas]
+    usage = {"prompt_tokens": 4, "completion_tokens": 6, "total_tokens": 10}
+    chunks.append({"choices": [{"delta": {}, "finish_reason": "tool_calls"}]})
+    if usage_only:
+        chunks.append({"choices": [], "usage": usage})
+    else:
+        chunks[0]["usage"] = usage
+
+    async def stream():
+        for chunk in chunks:
+            yield Mock(model_dump=lambda value=chunk: value)
+
+    client = SimpleNamespace(chat=SimpleNamespace(completions=SimpleNamespace(create=AsyncMock(return_value=stream()))),
+                             close=AsyncMock())
+    model = OpenAIModel(model_name="synthetic", api_key="synthetic")
+    request = LlmRequest()
+    request.streaming_tool_names = streaming_names
+    with patch.object(OpenAIModel, "_create_async_client", return_value=client):
+        return [response async for response in model._generate_stream({}, request)]
+
+
+def tool_delta(index, arguments, first=True):
+    result = {"index": index, "function": {"arguments": arguments}}
+    if first:
+        result.update(id=f"call_{index}", type="function")
+        result["function"]["name"] = f"tool_{index}"
+    return result
+
+
+@pytest.mark.parametrize("text", [{}, {
+    "content": "text"
+}, {
+    "reasoning_content": "synthetic"
+}, {
+    "content": "text",
+    "reasoning_content": "synthetic"
+}, {
+    "content": "",
+    "reasoning_content": None
+}])
+@pytest.mark.parametrize("fragmented", [False, True])
+@pytest.mark.parametrize("tool_count", [1, 2])
+@pytest.mark.parametrize("streaming", [False, True])
+@pytest.mark.asyncio
+async def test_mixed_stream_preserves_calls_and_text(text, fragmented, tool_count, streaming):
+    arguments = json.dumps({"value": "中文", "count": 12}, ensure_ascii=False)
+    fragments = [arguments[:12], arguments[12:]] if fragmented else [arguments]
+    deltas = [
+        dict(text, tool_calls=[tool_delta(index, fragment, first=part == 0) for index in range(tool_count)])
+        for part, fragment in enumerate(fragments)
+    ]
+    responses = await collect(deltas, {"tool_0"} if streaming else set(), usage_only=fragmented)
+    final = responses[-1]
+    assert not final.partial
+    assert final.error_code is None
+    assert final.response_id == "synthetic-response"
+    assert final.usage_metadata.total_token_count == 10
+    calls = [part.function_call for part in final.content.parts if part.function_call]
+    assert [(call.id, call.name, call.args) for call in calls] == [(f"call_{index}", f"tool_{index}", {
+        "value": "中文",
+        "count": 12
+    }) for index in range(tool_count)]
+    for thought, field in [(False, "content"), (True, "reasoning_content")]:
+        expected = (text.get(field) or "") * len(fragments)
+        assert "".join(part.text for part in final.content.parts
+                       if part.text and bool(part.thought) == thought) == expected
+        assert "".join(part.text for response in responses[:-1] if response.content for part in response.content.parts
+                       if part.text and bool(part.thought) == thought) == expected
+    partial_calls = [
+        part.function_call for response in responses[:-1] if response.content for part in response.content.parts
+        if part.function_call
+    ]
+    assert [(call.id, call.name, call.args) for call in partial_calls] == ([("call_0", "tool_0", {
+        const.TOOL_STREAMING_ARGS: fragment
+    }) for fragment in fragments] if streaming else [])
+
+
+@pytest.mark.asyncio
+async def test_separate_text_and_tool_chunks():
+    responses = await collect([{"content": "text"}, {"tool_calls": [tool_delta(0, '{"ok": true}')]}])
+    parts = responses[-1].content.parts
+    assert parts[0].text == "text"
+    assert parts[1].function_call.args == {"ok": True}
+
+
+@pytest.mark.parametrize("mixed", [False, True])
+@pytest.mark.asyncio
+async def test_invalid_json_preserves_error_envelope(mixed):
+    delta = {"tool_calls": [tool_delta(0, 'not-json'), tool_delta(1, '{"ok": true}')]}
+    if mixed:
+        delta["content"] = "text"
+    responses = await collect([delta])
+    final = responses[-1]
+    calls = [part.function_call for part in final.content.parts if part.function_call]
+    assert [call.name for call in calls] == ["tool_0", "tool_1"]
+    assert const.TOOL_CALL_ARGUMENT_ERRORS in calls[0].args
+    assert calls[1].args == {"ok": True}
+    assert final.error_code is None
+
+
+@pytest.mark.parametrize("mixed_index", [0, 1, 2])
+@pytest.mark.asyncio
+async def test_one_mixed_fragment_cannot_silently_change_arguments(mixed_index):
+    fragments = ['{"count":1', '2', '}']
+    deltas = [{"tool_calls": [tool_delta(0, fragment, first=index == 0)]} for index, fragment in enumerate(fragments)]
+    deltas[mixed_index]["content"] = "text"
+    responses = await collect(deltas, {"tool_0"})
+    calls = [part.function_call for part in responses[-1].content.parts if part.function_call]
+    assert len(calls) == 1
+    assert calls[0].id == "call_0"
+    assert calls[0].args == {"count": 12}
+    streamed = [
+        part.function_call.args[const.TOOL_STREAMING_ARGS] for response in responses[:-1] if response.content
+        for part in response.content.parts if part.function_call
+    ]
+    assert streamed == fragments
+
+
+@pytest.mark.asyncio
+async def test_mixed_chunk_text_precedes_streaming_tool_event():
+    responses = await collect([{
+        "content": "Recording now.",
+        "tool_calls": [tool_delta(0, '{"count":12}')]
+    }], {"tool_0"})
+    assert responses[0].partial
+    assert responses[0].content.parts[0].text == "Recording now."
+    assert responses[1].partial
+    assert responses[1].content.parts[0].function_call.name == "tool_0"
+
+
+@pytest.mark.asyncio
+async def test_mixed_chunks_keep_text_through_anthropic_proxy():
+    pytest.importorskip("claude_agent_sdk")
+    from trpc_agent_sdk.server.agents.claude._proxy import AnthropicMessagesRequest, AnthropicProxyApp
+
+    responses = await collect([
+        {
+            "content": "Recording ",
+            "tool_calls": [tool_delta(0, '{"count":')]
+        },
+        {
+            "content": "now.",
+            "tool_calls": [tool_delta(0, '12}', first=False)]
+        },
+    ], {"tool_0"})
+
+    async def generate(request, stream=True):
+        for response in responses:
+            yield response
+
+    model = SimpleNamespace(generate_async=generate)
+    request = AnthropicMessagesRequest(model="synthetic", messages=[{"role": "user", "content": "record"}], stream=True)
+    events = [event async for event in AnthropicProxyApp()._handle_streaming(LlmRequest(), request, model)]
+    payloads = [
+        json.loads(line[6:]) for event in events for line in event.splitlines()
+        if line.startswith("data: ") and line != "data: [DONE]"
+    ]
+    deltas = [payload["delta"] for payload in payloads if payload["type"] == "content_block_delta"]
+    assert "".join(delta["text"] for delta in deltas if delta["type"] == "text_delta") == "Recording now."
+    assert "".join(delta["partial_json"] for delta in deltas if delta["type"] == "input_json_delta") == '{"count":12}'
+
+    starts = [payload["index"] for payload in payloads if payload["type"] == "content_block_start"]
+    stops = [payload["index"] for payload in payloads if payload["type"] == "content_block_stop"]
+    assert len(starts) == len(set(starts))
+    assert sorted(starts) == sorted(stops)
+
+
+@pytest.mark.parametrize("mixed", [False, True])
+@pytest.mark.asyncio
+async def test_streaming_tool_events_keep_response_identity_and_chunk_metadata(mixed):
+    deltas = [
+        {
+            "tool_calls": [tool_delta(0, '{"count":')]
+        },
+        {
+            "tool_calls": [tool_delta(0, '12}', first=False)]
+        },
+    ]
+    if mixed:
+        for delta in deltas:
+            delta["content"] = "text"
+    responses = await collect(deltas, {"tool_0"})
+    tool_events = [
+        response for response in responses[:-1] if any(part.function_call for part in response.content.parts)
+    ]
+    assert len(tool_events) == 2
+    for event, delta in zip(tool_events, deltas):
+        assert event.response_id == responses[-1].response_id == "synthetic-response"
+        assert event.custom_metadata[const.TOOL_STREAMING] is True
+        assert event.custom_metadata[const.CHUNK]["choices"][0]["delta"] == delta
+
+
+@pytest.mark.asyncio
+async def test_fragmented_invalid_json_in_mixed_chunks_keeps_error_envelope():
+    responses = await collect([
+        {
+            "content": "Recording ",
+            "tool_calls": [tool_delta(0, 'not-')]
+        },
+        {
+            "content": "now.",
+            "tool_calls": [tool_delta(0, 'json', first=False)]
+        },
+    ], {"tool_0"})
+    assert [bool(response.content.parts[0].text) for response in responses[:-1]] == [True, False, True, False]
+    call = next(part.function_call for part in responses[-1].content.parts if part.function_call)
+    assert call.name == "tool_0"
+    assert const.TOOL_CALL_ARGUMENT_ERRORS in call.args
+    assert responses[-1].error_code is None
+
+
+@pytest.mark.asyncio
+async def test_proxy_closes_open_blocks_when_interleaved_stream_fails():
+    pytest.importorskip("claude_agent_sdk")
+    from trpc_agent_sdk.server.agents.claude._proxy import AnthropicMessagesRequest, AnthropicProxyApp
+
+    responses = await collect([
+        {
+            "content": "Recording ",
+            "tool_calls": [tool_delta(0, '{"count":')]
+        },
+        {
+            "content": "now."
+        },
+    ], {"tool_0"})
+
+    async def generate(request, stream=True):
+        for response in responses[:-1]:
+            yield response
+        raise RuntimeError("test stream interrupted")
+
+    request = AnthropicMessagesRequest(model="synthetic", messages=[{"role": "user", "content": "record"}], stream=True)
+    model = SimpleNamespace(generate_async=generate)
+    events = [event async for event in AnthropicProxyApp()._handle_streaming(LlmRequest(), request, model)]
+    payloads = [
+        json.loads(line[6:]) for event in events for line in event.splitlines()
+        if line.startswith("data: ") and line != "data: [DONE]"
+    ]
+    open_blocks = set()
+    for payload in payloads:
+        if payload["type"] == "content_block_start":
+            assert payload["index"] not in open_blocks
+            open_blocks.add(payload["index"])
+        elif payload["type"] == "content_block_stop":
+            assert payload["index"] in open_blocks
+            open_blocks.remove(payload["index"])
+        elif payload["type"] in {"message_delta", "message_stop"}:
+            assert not open_blocks
+    assert not open_blocks
+    assert next(p for p in payloads if p["type"] == "message_delta")["delta"]["stop_reason"] == "error"
diff --git a/trpc_agent_sdk/models/_openai_model.py b/trpc_agent_sdk/models/_openai_model.py
index cbeaf6923..5d0351080 100644
--- a/trpc_agent_sdk/models/_openai_model.py
+++ b/trpc_agent_sdk/models/_openai_model.py
@@ -1118,7 +1118,7 @@ def _process_responses_usage(self, response_dict: dict) -> Optional[GenerateCont
     def _process_chunk_without_content(
         self, chunk_dict: dict, accumulated_tool_calls: list[dict]
     ) -> tuple[Optional[FinishReason], Optional[GenerateContentResponseUsageMetadata], dict[int, str]]:
-        """Process a chunk that doesn't contain content.
+        """Process tool calls and usage, including chunks that also contain text.
 
         Args:
             chunk_dict (`dict`): The chunk dictionary to process
@@ -1149,7 +1149,7 @@ def _process_chunk_without_content(
         # Handle usage
         usage = self._process_usage(chunk_dict)
 
-        # Handle tool calls in chunks without content (this is where streaming tool calls happen)
+        # Handle tool calls independently of text content.
         tool_calls_data = delta.get(const.TOOL_CALLS)
 
         # Track delta arguments from this chunk
@@ -2519,30 +2519,36 @@ async def _generate_stream(
                     # We can log them but don't need to yield them as content
                     continue
 
-                # Verify if the chunk contains valid text content
-                if not self._verify_text_content_in_delta_response(chunk_dict):
-                    # Process chunk without content (this is where tool calls are streamed)
-                    _, usage, delta_arguments = self._process_chunk_without_content(chunk_dict, accumulated_tool_calls)
-
-                    if usage:
-                        last_usage = usage
-
-                    # If streaming tool call arguments is enabled, yield partial tool call events
-                    # delta_arguments being non-empty means tool calls were processed
-                    if streaming_tool_names and delta_arguments and accumulated_tool_calls:
-                        # Yield streaming tool call event with delta arguments
-                        # Only for tools in streaming_tool_names
-                        streaming_event = self._create_streaming_tool_call_response(accumulated_tool_calls,
-                                                                                    delta_arguments,
-                                                                                    streaming_tool_names)
-                        if streaming_event:
-                            yield streaming_event
+                # Tool deltas and text can coexist in the same chunk.
+                _, usage, delta_arguments = self._process_chunk_without_content(chunk_dict, accumulated_tool_calls)
+
+                if usage:
+                    last_usage = usage
+
+                # Emit text before tool events from the same chunk for streaming consumers.
+                streaming_event = None
+                # If streaming tool call arguments is enabled, prepare partial tool call events
+                # delta_arguments being non-empty means tool calls were processed
+                if streaming_tool_names and delta_arguments and accumulated_tool_calls:
+                    # Yield streaming tool call event with delta arguments
+                    # Only for tools in streaming_tool_names
+                    streaming_event = self._create_streaming_tool_call_response(accumulated_tool_calls,
+                                                                                delta_arguments,
+                                                                                streaming_tool_names)
+                    if streaming_event:
+                        streaming_event.response_id = response_id
+                        streaming_event.custom_metadata = {const.CHUNK: chunk_dict, const.TOOL_STREAMING: True}
 
+                if not self._verify_text_content_in_delta_response(chunk_dict):
+                    if streaming_event:
+                        yield streaming_event
                     continue
 
                 # Process chunk with valid content
                 choices = chunk_dict.get(const.CHOICES, [])
                 if not choices:
+                    if streaming_event:
+                        yield streaming_event
                     continue  # Skip if no choices available
                 choice: dict[str, dict] = choices[0]
                 delta = choice[const.DELTA]
@@ -2558,6 +2564,8 @@ async def _generate_stream(
                             partial_text = self._adapter.filter_streaming_text(reasoning_content,
                                                                                reasoning_filter_state)
                         if not partial_text:
+                            if streaming_event:
+                                yield streaming_event
                             continue
 
                         # Reasoning content is always thinking content
@@ -2589,6 +2597,8 @@ async def _generate_stream(
                             content_filter_state = streaming_text_filter_state["content"]
                             partial_text = self._adapter.filter_streaming_text(content, content_filter_state)
                         if not partial_text:
+                            if streaming_event:
+                                yield streaming_event
                             continue
                         if not is_thinking:
                             visible_content += partial_text
@@ -2604,11 +2614,8 @@ async def _generate_stream(
                             response_id=response_id,
                             custom_metadata={const.CHUNK: chunk_dict},
                         )
-
-                # Handle usage
-                usage = self._process_usage(chunk_dict)
-                if usage:
-                    last_usage = usage
+                if streaming_event:
+                    yield streaming_event
 
             if tool_prompt and streaming_text_filter_state is not None:
                 if self._adapter.should_filter_reasoning_text():
diff --git a/trpc_agent_sdk/server/agents/claude/_proxy.py b/trpc_agent_sdk/server/agents/claude/_proxy.py
index a916ee019..6b7a1a643 100644
--- a/trpc_agent_sdk/server/agents/claude/_proxy.py
+++ b/trpc_agent_sdk/server/agents/claude/_proxy.py
@@ -705,6 +705,9 @@ async def _handle_streaming(self, llm_request: LlmRequest, original_request: Ant
         Yields:
             Server-sent events in Anthropic format
         """
+        text_block_closed = True
+        text_block_index = 0
+        streaming_tool_calls: Dict[str, Dict[str, Any]] = {}
         try:
             # Send message_start event
             message_id = f"msg_{uuid.uuid4().hex[:24]}"
@@ -746,10 +749,10 @@ async def _handle_streaming(self, llm_request: LlmRequest, original_request: Ant
 
             # Track state
             text_block_closed = False
+            text_block_index = 0
             last_usage = None
             # Track streaming tool calls: {tool_id: {"index": int, "name": str, "started": bool}}
-            streaming_tool_calls: Dict[str, Dict[str, Any]] = {}
-            next_tool_index = 0  # Next available tool block index (0 is text block)
+            next_tool_index = 0  # Shared index allocator for text and tool blocks
 
             # Call model with streaming
             response_generator = model.generate_async(llm_request, stream=True)
@@ -778,8 +781,9 @@ def _is_streaming_tool_call(resp) -> bool:
                             # Close text block if not already closed
                             if not text_block_closed:
                                 text_block_closed = True
+                                text_stop_event = {"type": "content_block_stop", "index": text_block_index}
                                 yield ("event: content_block_stop\n"
-                                       f'data: {json.dumps({"type": "content_block_stop", "index": 0})}\n\n')
+                                       f"data: {json.dumps(text_stop_event)}\n\n")
 
                             # Check if we need to start a new tool block
                             if tool_id not in streaming_tool_calls:
@@ -822,11 +826,23 @@ def _is_streaming_tool_call(resp) -> bool:
                 # Handle partial responses (streaming text only)
                 elif llm_response.partial and llm_response.content:
                     for part in llm_response.content.parts:
-                        if part.text and not text_block_closed:
+                        if part.text:
+                            if text_block_closed:
+                                # A model may emit more text after starting a tool call.
+                                next_tool_index += 1
+                                text_block_index = next_tool_index
+                                text_block_closed = False
+                                text_start_event = {
+                                    "type": "content_block_start",
+                                    "index": text_block_index,
+                                    "content_block": {"type": "text", "text": ""},
+                                }
+                                yield ("event: content_block_start\n"
+                                       f"data: {json.dumps(text_start_event)}\n\n")
                             # Stream text deltas
                             text_delta_event = {
                                 "type": "content_block_delta",
-                                "index": 0,
+                                "index": text_block_index,
                                 "delta": {
                                     "type": "text_delta",
                                     "text": part.text
@@ -841,7 +857,7 @@ def _is_streaming_tool_call(resp) -> bool:
                     if not text_block_closed:
                         text_block_closed = True
                         yield ("event: content_block_stop\n"
-                               f'data: {json.dumps({"type": "content_block_stop", "index": 0})}\n\n')
+                               f'data: {json.dumps({"type": "content_block_stop", "index": text_block_index})}\n\n')
 
                     # Close any streaming tool blocks that were started
                     for tool_id, tool_info in streaming_tool_calls.items():
@@ -938,6 +954,18 @@ def _is_streaming_tool_call(resp) -> bool:
 
         except Exception as ex:  # pylint: disable=broad-except
             self.logger.error("Error in streaming: %s", str(ex))
+            # Close started blocks before terminating the interrupted message.
+            open_indices = []
+            if not text_block_closed:
+                open_indices.append(text_block_index)
+                text_block_closed = True
+            for tool_info in streaming_tool_calls.values():
+                if tool_info.get("started") and not tool_info.get("closed"):
+                    open_indices.append(tool_info["index"])
+                    tool_info["closed"] = True
+            for index in sorted(open_indices):
+                stop_event = {"type": "content_block_stop", "index": index}
+                yield f"event: content_block_stop\ndata: {json.dumps(stop_event)}\n\n"
             # Send error response to client
             error_data = {
                 "type": "message_delta",