diff --git a/src/plyngent/agent/responses_bridge.py b/src/plyngent/agent/responses_bridge.py
index 7c130a3..15c0022 100644
--- a/src/plyngent/agent/responses_bridge.py
+++ b/src/plyngent/agent/responses_bridge.py
@@ -83,6 +83,49 @@ def _assistant_to_input_items(
     return items
 
 
+def _item_call_id(
+    item: dict[str, Any] | ResponseEasyInputMessage | ResponseFunctionToolCallOutput,
+) -> str | None:
+    """Return the call id for a ``function_call`` input item, else ``None``."""
+    if isinstance(item, ResponseFunctionToolCallOutput):
+        return item.call_id
+    if isinstance(item, dict) and item.get("type") == "function_call":
+        call_id = item.get("call_id")
+        return call_id if isinstance(call_id, str) else None
+    return None
+
+
+def _interleave_tool_outputs(
+    items: list[dict[str, Any] | ResponseEasyInputMessage | ResponseFunctionToolCallOutput],
+) -> list[dict[str, Any] | ResponseEasyInputMessage | ResponseFunctionToolCallOutput]:
+    """Place each ``function_call_output`` immediately after its ``function_call``.
+
+    OpenAI matches outputs to calls by ``call_id`` anywhere in ``input``, but
+    DeepSeek's Responses implementation expects each ``function_call`` to be
+    directly followed by its ``function_call_output`` — a parallel batch sent
+    as ``call, call, output, output`` is rejected with "No tool output found
+    for tool call …". Interleaving is a no-op for single-call rounds and stays
+    valid for OpenAI (outputs still follow their calls).
+    """
+    outputs_by_call: dict[str, list[ResponseFunctionToolCallOutput]] = {}
+    for item in items:
+        if isinstance(item, ResponseFunctionToolCallOutput):
+            outputs_by_call.setdefault(item.call_id, []).append(item)
+
+    out: list[dict[str, Any] | ResponseEasyInputMessage | ResponseFunctionToolCallOutput] = []
+    for item in items:
+        if isinstance(item, ResponseFunctionToolCallOutput):
+            continue  # re-added right after their call below
+        out.append(item)
+        call_id = _item_call_id(item)
+        if call_id is not None and call_id in outputs_by_call:
+            out.extend(outputs_by_call.pop(call_id))
+    # Defensive: outputs whose call was not seen keep stream order at the end.
+    for pending in outputs_by_call.values():
+        out.extend(pending)
+    return out
+
+
 def chat_messages_to_responses_input(
     messages: Sequence[AnyChatMessage],
 ) -> tuple[str | None, list[dict[str, Any] | ResponseEasyInputMessage | ResponseFunctionToolCallOutput]]:
@@ -112,7 +155,7 @@ def chat_messages_to_responses_input(
             )
 
     instructions = "\n\n".join(instructions_parts) if instructions_parts else None
-    return instructions, items
+    return instructions, _interleave_tool_outputs(items)
 
 
 def response_to_assistant_message(response: Response) -> AssistantChatMessage:
diff --git a/tests/test_agent/test_responses_bridge.py b/tests/test_agent/test_responses_bridge.py
index eb0a069..104e1ab 100644
--- a/tests/test_agent/test_responses_bridge.py
+++ b/tests/test_agent/test_responses_bridge.py
@@ -8,7 +8,7 @@ from plyngent.agent.responses_bridge import (
     responses_status_to_finish_reason,
     tool_items_to_response_tools,
 )
-from plyngent.lmproto.openai.model import Response
+from plyngent.lmproto.openai.model import Response, ResponseFunctionToolCallOutput
 from plyngent.lmproto.openai_compatible.model import (
     AssistantChatMessage,
     AssistantFunctionTool,
@@ -57,6 +57,51 @@ def test_chat_messages_to_input_and_instructions() -> None:
     assert len(items) == 3  # user, function_call, function_call_output
 
 
+def test_parallel_tool_outputs_interleaved_after_calls() -> None:
+    """Regression: DeepSeek Responses rejects call, call, output, output batches.
+
+    Each ``function_call_output`` must directly follow its ``function_call`` so
+    strict/adjacency-matching servers (DeepSeek) accept parallel tool rounds.
+    """
+    messages = [
+        UserChatMessage(content="run both"),
+        AssistantChatMessage(
+            content=None,
+            tool_calls=[
+                AssistantFunctionToolCall(
+                    id="call_01_LPBuUG3KTaMDIwUoLwTE9127",
+                    function=AssistantFunctionTool(name="read_file", arguments='{"path":"a"}'),
+                ),
+                AssistantFunctionToolCall(
+                    id="call_02_ABCD",
+                    function=AssistantFunctionTool(name="grep_files", arguments='{"pattern":"todo"}'),
+                ),
+            ],
+        ),
+        ToolChatMessage(content="file body", tool_call_id="call_01_LPBuUG3KTaMDIwUoLwTE9127"),
+        ToolChatMessage(content="grep hit", tool_call_id="call_02_ABCD"),
+    ]
+    _, items = chat_messages_to_responses_input(messages)
+    types = [item.get("type") if isinstance(item, dict) else item.__struct_config__.tag for item in items]
+    assert types == [
+        "message",
+        "function_call",
+        "function_call_output",
+        "function_call",
+        "function_call_output",
+    ]
+    # Each output is paired with its own call, in stream order.
+    call_a = items[1]
+    out_a = items[2]
+    call_b = items[3]
+    out_b = items[4]
+    assert isinstance(call_a, dict) and isinstance(call_b, dict)
+    assert isinstance(out_a, ResponseFunctionToolCallOutput)
+    assert isinstance(out_b, ResponseFunctionToolCallOutput)
+    assert out_a.call_id == call_a["call_id"]
+    assert out_b.call_id == call_b["call_id"]
+
+
 def test_response_to_assistant_with_tools() -> None:
     raw = {
         "id": "resp_1",