diff --git a/acp_adapter/server.py b/acp_adapter/server.py
index 543d49cb..64a31063 100644
--- a/acp_adapter/server.py
+++ b/acp_adapter/server.py
@@ -6,7 +6,6 @@ import asyncio
 import contextvars
 import logging
 import os
-import uuid
 from collections import defaultdict, deque
 from concurrent.futures import ThreadPoolExecutor
 from typing import Any, Deque, Optional
@@ -403,25 +402,20 @@ class HermesACPAgent(acp.Agent):
     @staticmethod
     def _history_message_update(
         *,
-        session_id: str,
-        index: int,
         role: str,
         text: str,
     ) -> UserMessageChunk | AgentMessageChunk | None:
         """Build an ACP history replay update for a user/assistant message."""
-        message_id = str(uuid.uuid5(uuid.NAMESPACE_URL, f"hermes-acp:{session_id}:{index}:{role}"))
         block = TextContentBlock(type="text", text=text)
         if role == "user":
             return UserMessageChunk(
                 session_update="user_message_chunk",
                 content=block,
-                message_id=message_id,
             )
         if role == "assistant":
             return AgentMessageChunk(
                 session_update="agent_message_chunk",
                 content=block,
-                message_id=message_id,
             )
         return None
 
@@ -437,19 +431,14 @@ class HermesACPAgent(acp.Agent):
         if not self._conn or not state.history:
             return
 
-        for index, message in enumerate(state.history):
+        for message in state.history:
             role = str(message.get("role") or "")
             if role not in {"user", "assistant"}:
                 continue
             text = self._history_message_text(message)
             if not text:
                 continue
-            update = self._history_message_update(
-                session_id=state.session_id,
-                index=index,
-                role=role,
-                text=text,
-            )
+            update = self._history_message_update(role=role, text=text)
             if update is None:
                 continue
             try:
diff --git a/tests/acp/test_server.py b/tests/acp/test_server.py
index 2fee2bf1..6628f0da 100644
--- a/tests/acp/test_server.py
+++ b/tests/acp/test_server.py
@@ -254,10 +254,8 @@ class TestSessionOps:
         assert len(replay_calls) == 2
         assert isinstance(replay_calls[0].kwargs["update"], UserMessageChunk)
         assert replay_calls[0].kwargs["update"].content.text == "what controls the / slash commands?"
-        assert replay_calls[0].kwargs["update"].message_id
         assert isinstance(replay_calls[1].kwargs["update"], AgentMessageChunk)
         assert replay_calls[1].kwargs["update"].content.text.startswith("HermesACPAgent")
-        assert replay_calls[1].kwargs["update"].message_id
 
     @pytest.mark.asyncio
     async def test_resume_session_replays_persisted_history_to_client(self, agent):