diff --git a/homeassistant/components/conversation/__init__.py b/homeassistant/components/conversation/__init__.py
index 5009530dc31..46a060f99bf 100644
--- a/homeassistant/components/conversation/__init__.py
+++ b/homeassistant/components/conversation/__init__.py
@@ -18,10 +18,12 @@ from homeassistant.helpers.typing import ConfigType
 from homeassistant.loader import bind_hass
 
 from .agent import AbstractConversationAgent, ConversationInput, ConversationResult
+from .const import HOME_ASSISTANT_AGENT
 from .default_agent import DefaultAgent
 
 __all__ = [
     "DOMAIN",
+    "HOME_ASSISTANT_AGENT",
     "async_converse",
     "async_get_agent_info",
     "async_set_agent",
@@ -333,8 +335,6 @@ async def async_converse(
 class AgentManager:
     """Class to manage conversation agents."""
 
-    HOME_ASSISTANT_AGENT = "homeassistant"
-
     default_agent: str = HOME_ASSISTANT_AGENT
     _builtin_agent: AbstractConversationAgent | None = None
 
@@ -351,7 +351,7 @@ class AgentManager:
         if agent_id is None:
             agent_id = self.default_agent
 
-        if agent_id == AgentManager.HOME_ASSISTANT_AGENT:
+        if agent_id == HOME_ASSISTANT_AGENT:
             if self._builtin_agent is not None:
                 return self._builtin_agent
 
@@ -376,7 +376,7 @@ class AgentManager:
         """List all agents."""
         agents: list[AgentInfo] = [
             {
-                "id": AgentManager.HOME_ASSISTANT_AGENT,
+                "id": HOME_ASSISTANT_AGENT,
                 "name": "Home Assistant",
             }
         ]
@@ -401,18 +401,18 @@ class AgentManager:
     @core.callback
     def async_is_valid_agent_id(self, agent_id: str) -> bool:
         """Check if the agent id is valid."""
-        return agent_id in self._agents or agent_id == AgentManager.HOME_ASSISTANT_AGENT
+        return agent_id in self._agents or agent_id == HOME_ASSISTANT_AGENT
 
     @core.callback
     def async_set_agent(self, agent_id: str, agent: AbstractConversationAgent) -> None:
         """Set the agent."""
         self._agents[agent_id] = agent
-        if self.default_agent == AgentManager.HOME_ASSISTANT_AGENT:
+        if self.default_agent == HOME_ASSISTANT_AGENT:
             self.default_agent = agent_id
 
     @core.callback
     def async_unset_agent(self, agent_id: str) -> None:
         """Unset the agent."""
         if self.default_agent == agent_id:
-            self.default_agent = AgentManager.HOME_ASSISTANT_AGENT
+            self.default_agent = HOME_ASSISTANT_AGENT
         self._agents.pop(agent_id, None)
diff --git a/homeassistant/components/conversation/const.py b/homeassistant/components/conversation/const.py
index 04bfa373061..7ba12ec830d 100644
--- a/homeassistant/components/conversation/const.py
+++ b/homeassistant/components/conversation/const.py
@@ -1,3 +1,4 @@
 """Const for conversation integration."""
 
 DOMAIN = "conversation"
+HOME_ASSISTANT_AGENT = "homeassistant"
diff --git a/homeassistant/components/voice_assistant/pipeline.py b/homeassistant/components/voice_assistant/pipeline.py
index b30e3b07474..c2eff90530b 100644
--- a/homeassistant/components/voice_assistant/pipeline.py
+++ b/homeassistant/components/voice_assistant/pipeline.py
@@ -289,7 +289,10 @@ class PipelineRun:
     async def prepare_recognize_intent(self) -> None:
         """Prepare recognizing an intent."""
         agent_info = conversation.async_get_agent_info(
-            self.hass, self.pipeline.conversation_engine
+            self.hass,
+            # If no conversation engine is set, use the Home Assistant agent
+            # (the conversation integration default is currently the last one set)
+            self.pipeline.conversation_engine or conversation.HOME_ASSISTANT_AGENT,
         )
 
         if agent_info is None:
diff --git a/tests/components/conversation/test_init.py b/tests/components/conversation/test_init.py
index 03f581b9aff..a4d6ea6c915 100644
--- a/tests/components/conversation/test_init.py
+++ b/tests/components/conversation/test_init.py
@@ -25,7 +25,7 @@ from . import expose_entity, expose_new
 from tests.common import MockConfigEntry, MockUser, async_mock_service
 from tests.typing import ClientSessionGenerator, WebSocketGenerator
 
-AGENT_ID_OPTIONS = [None, conversation.AgentManager.HOME_ASSISTANT_AGENT]
+AGENT_ID_OPTIONS = [None, conversation.HOME_ASSISTANT_AGENT]
 
 
 class OrderBeerIntentHandler(intent.IntentHandler):
@@ -1569,7 +1569,7 @@ async def test_agent_id_validator_invalid_agent(hass: HomeAssistant) -> None:
     with pytest.raises(vol.Invalid):
         conversation.agent_id_validator("invalid_agent")
 
-    conversation.agent_id_validator(conversation.AgentManager.HOME_ASSISTANT_AGENT)
+    conversation.agent_id_validator(conversation.HOME_ASSISTANT_AGENT)
 
 
 async def test_get_agent_list(