diff --git a/tensorrt_llm/disaggregated_params.py b/tensorrt_llm/disaggregated_params.py
index 5c91dae3f5de..1c6970eac175 100644
--- a/tensorrt_llm/disaggregated_params.py
+++ b/tensorrt_llm/disaggregated_params.py
@@ -1,3 +1,18 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 from dataclasses import dataclass
 from enum import IntEnum
 from typing import Any, Dict, List, Optional
@@ -31,7 +46,6 @@ class DisaggregatedParams:
          Each entry is a torch.Tensor of shape [num_tokens, vocab_size] (one per beam/sequence).
         ctx_usage (Dict[str, Any]): The context usage payload to preserve exact
          usage accounting on the generation server.
-
         multimodal_embedding_handles (List[Dict[str, Any]]): The resulting multimodal embedding handles from ViT.
         multimodal_hashes (List[List[int]]): The multimodal hashes of each multimodal item in the request.
     """
@@ -50,10 +64,6 @@ class DisaggregatedParams:
     ctx_info_endpoint: Optional[str] = None
     schedule_style: Optional[DisaggScheduleStyle] = None
     ctx_usage: Optional[Dict[str, Any]] = None
-    # Multi-turn conversation id (from session headers such as X-Session-ID),
-    # carried through so worker-side consumers (e.g. the ADP router) can see
-    # the same id the disagg orchestrator routed on.
-    conversation_id: Optional[str] = None
 
     # E-P Disaggregated Params
     multimodal_embedding_handles: Optional[List[Dict[str, Any]]] = (
diff --git a/tensorrt_llm/serve/conversation_id.py b/tensorrt_llm/serve/conversation_id.py
index 2acfcad8012e..c4146d93e5d8 100644
--- a/tensorrt_llm/serve/conversation_id.py
+++ b/tensorrt_llm/serve/conversation_id.py
@@ -36,10 +36,7 @@ class RequestWithConversationParams(Protocol):
 
 def get_request_conversation_id(request: RequestWithConversationParams) -> Optional[str]:
     conversation_params = request.conversation_params
-    if conversation_params is not None:
-        return conversation_params.conversation_id
-    disaggregated_params = getattr(request, "disaggregated_params", None)
-    return None if disaggregated_params is None else disaggregated_params.conversation_id
+    return None if conversation_params is None else conversation_params.conversation_id
 
 
 def extract_conversation_id_from_headers(headers: Optional[Mapping[str, str]]) -> Optional[str]:
@@ -62,8 +59,7 @@ def resolve_request_conversation_id(
 ) -> Optional[str]:
     """Return conversation_params.conversation_id populated at the serve edge.
 
-    Body ``conversation_params.conversation_id`` is canonical. Headers are used
-    only when the body does not provide an id.
+    Body ``conversation_params.conversation_id`` takes precedence over headers.
     """
     conversation_params = request.conversation_params
     if conversation_params is not None:
diff --git a/tensorrt_llm/serve/openai_disagg_service.py b/tensorrt_llm/serve/openai_disagg_service.py
index 3d7b9e608ec5..f1ea3c45c5c8 100644
--- a/tensorrt_llm/serve/openai_disagg_service.py
+++ b/tensorrt_llm/serve/openai_disagg_service.py
@@ -192,25 +192,15 @@ def _need_gen(self, response: UCompletionResponse) -> bool:
             return False
         return True
 
-    @staticmethod
-    def _get_conversation_id(request: UCompletionRequest) -> Optional[str]:
-        if request.conversation_params is not None:
-            return request.conversation_params.conversation_id
-        if request.disaggregated_params is not None:
-            return request.disaggregated_params.conversation_id
-        return None
-
     def _get_ctx_request(
         self, request: UCompletionRequest, disagg_request_id: Optional[int]
     ) -> UCompletionRequest:
-        conversation_id = self._get_conversation_id(request)
         ctx_request = request.model_copy(
             update={
                 "disaggregated_params": DisaggregatedParams(
                     request_type="context_only",
                     disagg_request_id=disagg_request_id,
                     schedule_style=self._schedule_style,
-                    conversation_id=conversation_id,
                     return_prompt_token_ids_b64=self._tokids_ctxbytes,
                 ),
                 "stream": False,
@@ -226,12 +216,10 @@ def _get_gen_request(
         disagg_request_id: Optional[int],
         ctx_server_info: Optional[dict] = None,
     ) -> UCompletionRequest:
-        conversation_id = self._get_conversation_id(request)
         if ctx_response:
             request.disaggregated_params = ctx_response.choices[0].disaggregated_params
             request.disaggregated_params.request_type = "generation_only"
             request.disaggregated_params.schedule_style = self._schedule_style
-            request.disaggregated_params.conversation_id = conversation_id
             request.disaggregated_params.ctx_usage = ctx_response.usage
             # Replace the string prompt with prompt_tokens_ids
             if isinstance(request, CompletionRequest):
@@ -261,7 +249,6 @@ def _get_gen_request(
                 ctx_request_id=disagg_request_id,
                 disagg_request_id=disagg_request_id,
                 schedule_style=self._schedule_style,
-                conversation_id=conversation_id,
             )
         if ctx_server_info and "server_info" in ctx_server_info:
             disaggregated_params = ctx_server_info["server_info"].get("disaggregated_params", {})
diff --git a/tensorrt_llm/serve/openai_protocol.py b/tensorrt_llm/serve/openai_protocol.py
index ef5fd54cc875..a2608d4ae199 100644
--- a/tensorrt_llm/serve/openai_protocol.py
+++ b/tensorrt_llm/serve/openai_protocol.py
@@ -1,3 +1,18 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 # Adapted from
 # https://github.com/vllm-project/vllm/blob/4db5176d9758b720b05460c50ace3c01026eb158/vllm/entrypoints/openai/protocol.py
 import base64
@@ -222,7 +237,6 @@ class DisaggregatedParams(OpenAIBaseModel):
     ctx_dp_rank: Optional[int] = None
     ctx_info_endpoint: Optional[str] = None
     schedule_style: Optional[DisaggScheduleStyle] = None
-    conversation_id: Optional[str] = None
     ctx_usage: Optional[UsageInfo] = None
     # TODO(TRTLLM-12407): Multimodal E/PD over trtllm-serve needs these protocol fields too:
     # encoder embedding handles, multimodal hashes, and optional mRoPE handles.
@@ -1560,7 +1574,6 @@ def to_disaggregated_params(
         ctx_info_endpoint=tllm_disagg_params.ctx_info_endpoint,
         schedule_style=tllm_disagg_params.schedule_style,
         ctx_usage=ctx_usage,
-        conversation_id=tllm_disagg_params.conversation_id,
     )
 
 
@@ -1585,7 +1598,6 @@ def to_llm_disaggregated_params(
         ctx_info_endpoint=disaggregated_params.ctx_info_endpoint,
         schedule_style=disaggregated_params.schedule_style,
         ctx_usage=None if ctx_usage is None else ctx_usage.model_dump(),
-        conversation_id=disaggregated_params.conversation_id,
     )
 
 
diff --git a/tests/unittest/disaggregated/test_coordinator_worker.py b/tests/unittest/disaggregated/test_coordinator_worker.py
index 4ff67c58c465..6f6684bb6921 100644
--- a/tests/unittest/disaggregated/test_coordinator_worker.py
+++ b/tests/unittest/disaggregated/test_coordinator_worker.py
@@ -60,6 +60,7 @@
 from tensorrt_llm.serve.openai_protocol import (
     ChatCompletionRequest,
     CompletionRequest,
+    ConversationParams,
     DisaggregatedParams,
 )
 from tensorrt_llm.serve.router import (
@@ -535,10 +536,10 @@ def _req(conv_id, request_id):
                 return CompletionRequest(
                     model="m",
                     prompt="hi",
+                    conversation_params=ConversationParams(conversation_id=conv_id),
                     disaggregated_params=DisaggregatedParams(
                         request_type="generation_only",
                         ctx_request_id=request_id,
-                        conversation_id=conv_id,
                     ),
                 )
 
@@ -583,11 +584,11 @@ async def drive():
                 request = CompletionRequest(
                     model="m",
                     prompt="hello",
+                    conversation_params=ConversationParams(conversation_id="conv-A"),
                     disaggregated_params=DisaggregatedParams(
                         request_type="generation_only",
                         ctx_request_id=assigned_id,
                         disagg_request_id=None,
-                        conversation_id="conv-A",
                     ),
                 )
                 await remote.gen_router.get_next_server(request)
diff --git a/tests/unittest/disaggregated/test_disagg_internal_auth.py b/tests/unittest/disaggregated/test_disagg_internal_auth.py
index e409269597cd..6a35cd1e4990 100644
--- a/tests/unittest/disaggregated/test_disagg_internal_auth.py
+++ b/tests/unittest/disaggregated/test_disagg_internal_auth.py
@@ -21,7 +21,11 @@
     request_requires_internal_disagg_auth,
     validate_internal_disagg_request,
 )
-from tensorrt_llm.serve.openai_protocol import CompletionRequest, DisaggregatedParams
+from tensorrt_llm.serve.openai_protocol import (
+    CompletionRequest,
+    ConversationParams,
+    DisaggregatedParams,
+)
 from tensorrt_llm.serve.openai_server import OpenAIServer
 
 
@@ -114,7 +118,7 @@ def test_protected_fields_accept_valid_header_after_wire_roundtrip():
         encoded_opaque_state="b3BhcXVl",
         ctx_info_endpoint="tcp://10.0.0.1:5000",
     )
-    request.disaggregated_params.conversation_id = "conversation-1"
+    request.conversation_params = ConversationParams(conversation_id="conversation-1")
     headers = build_internal_disagg_auth_headers("secret", request)
 
     wire_request = CompletionRequest.model_validate_json(
@@ -139,10 +143,10 @@ def test_ctx_info_endpoint_list_sender_matches_validated_string_receiver():
     validate_internal_disagg_request("secret", wire_request, headers)
 
 
-def test_unprotected_disagg_fields_do_not_invalidate_internal_auth_header():
+def test_conversation_params_do_not_invalidate_internal_auth_header():
     request = _make_request(ctx_info_endpoint="tcp://10.0.0.1:5000")
     headers = build_internal_disagg_auth_headers("secret", request)
-    request.disaggregated_params.conversation_id = "conversation-1"
+    request.conversation_params = ConversationParams(conversation_id="conversation-1")
 
     validate_internal_disagg_request("secret", request, headers)
 
diff --git a/tests/unittest/disaggregated/test_disaggregated_params.py b/tests/unittest/disaggregated/test_disaggregated_params.py
index 75bdfdbe254e..ca13037e3af1 100644
--- a/tests/unittest/disaggregated/test_disaggregated_params.py
+++ b/tests/unittest/disaggregated/test_disaggregated_params.py
@@ -1,3 +1,18 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 from unittest.mock import MagicMock, patch
 
 import pytest
@@ -81,7 +96,6 @@ def test_to_disaggregated_params():
                 "cached_tokens": 4,
             },
         },
-        conversation_id="conv-abc",
     )
     openai_params = to_disaggregated_params(llm_params)
 
@@ -92,7 +106,6 @@ def test_to_disaggregated_params():
     assert openai_params.ctx_info_endpoint == "tcp://10.0.0.1:5000"
     assert openai_params.ctx_usage.prompt_tokens == 10
     assert openai_params.ctx_usage.prompt_tokens_details.cached_tokens == 4
-    assert openai_params.conversation_id == "conv-abc"
 
 
 def test_to_llm_disaggregated_params():
@@ -113,7 +126,6 @@ def test_to_llm_disaggregated_params():
             total_tokens=10,
             prompt_tokens_details=PromptTokensDetails(cached_tokens=4),
         ),
-        conversation_id="conv-xyz",
     )
     llm_params = to_llm_disaggregated_params(openai_params)
 
@@ -123,26 +135,6 @@ def test_to_llm_disaggregated_params():
     assert llm_params.ctx_info_endpoint == "tcp://10.0.0.1:5000"
     assert llm_params.ctx_usage["prompt_tokens"] == 10
     assert llm_params.ctx_usage["prompt_tokens_details"]["cached_tokens"] == 4
-    assert llm_params.conversation_id == "conv-xyz"
-
-
-def test_disaggregated_params_conversation_id():
-    """conversation_id defaults to None and survives the serve<->llm round-trip."""
-    from tensorrt_llm.serve.openai_protocol import DisaggregatedParams as OpenAIDisaggregatedParams
-    from tensorrt_llm.serve.openai_protocol import (
-        to_disaggregated_params,
-        to_llm_disaggregated_params,
-    )
-
-    assert DisaggregatedParams().conversation_id is None
-
-    # serve -> llm -> serve preserves the conversation id end to end.
-    openai_params = OpenAIDisaggregatedParams(
-        request_type="context_only", conversation_id="conv-roundtrip"
-    )
-    llm_params = to_llm_disaggregated_params(openai_params)
-    assert llm_params.conversation_id == "conv-roundtrip"
-    assert to_disaggregated_params(llm_params).conversation_id == "conv-roundtrip"
 
 
 def test_opaque_state_round_trips_through_openai_protocol():
diff --git a/tests/unittest/disaggregated/test_openai_disagg_server.py b/tests/unittest/disaggregated/test_openai_disagg_server.py
index 4f91ed302bdf..159060cacf7e 100644
--- a/tests/unittest/disaggregated/test_openai_disagg_server.py
+++ b/tests/unittest/disaggregated/test_openai_disagg_server.py
@@ -186,7 +186,6 @@ def test_extract_conversation_id_preserves_body_conversation_params():
     )
 
     assert request.conversation_params.conversation_id == "body-id"
-    assert request.disaggregated_params.conversation_id is None
 
 
 def test_extract_conversation_id_populates_conversation_params_with_existing_disaggregated_params():
@@ -202,7 +201,6 @@ def test_extract_conversation_id_populates_conversation_params_with_existing_dis
     )
 
     assert request.conversation_params.conversation_id == "multi-turn-session-id"
-    assert request.disaggregated_params.conversation_id is None
 
 
 def test_disagg_config_allows_request_chat_template_opt_in():
diff --git a/tests/unittest/disaggregated/test_openai_disagg_service.py b/tests/unittest/disaggregated/test_openai_disagg_service.py
index 5af2db0b4907..3297f547e27d 100644
--- a/tests/unittest/disaggregated/test_openai_disagg_service.py
+++ b/tests/unittest/disaggregated/test_openai_disagg_service.py
@@ -234,6 +234,20 @@ def test_get_gen_request_uses_ctx_response_prompt_token_ids_for_chat():
     assert gen_request.conversation_params.conversation_id == "conv-chat"
 
 
+def test_get_ctx_request_preserves_conversation_params_on_wire():
+    service = _make_service("context_first")
+    request = CompletionRequest(
+        model="test-model",
+        prompt="hello",
+        conversation_params=ConversationParams(conversation_id="conv-completion"),
+    )
+
+    ctx_request = service._get_ctx_request(request, 42)
+
+    wire_request = ctx_request.model_dump(exclude_unset=True)
+    assert wire_request["conversation_params"]["conversation_id"] == "conv-completion"
+
+
 @pytest.mark.asyncio
 async def test_create_chat_response_sets_prompt_token_ids_for_context_only():
     from tensorrt_llm.serve.openai_server import OpenAIServer