fix(agent): keep reset generation out of external conversation ID (#2818)

Fixes #2814

After a session reset, keep the reset generation marker out of provider-facing external conversation state so Runner plugins start a new remote conversation.

src/langbot/pkg/agent/runner/persistent_state_store.py

@@ -188,7 +188,7 @@ class PersistentStateStore:
                         except json.JSONDecodeError:
                             pass  # Skip invalid JSON
 
-        # Seed external.conversation_id from event.conversation_id if not set
+        # Seed the host conversation ID only before the conversation is reset.
         if self._check_scope_enabled('conversation', binding) and event.conversation_id:
             if 'external.conversation_id' not in snapshot['conversation']:
                 from .context_reset import get_reset_generation
@@ -196,7 +196,8 @@ class PersistentStateStore:
                 generation = await get_reset_generation(
                     self._db_engine, event.workspace_id, event.bot_id, event.conversation_id
                 )
-                snapshot['conversation']['external.conversation_id'] = generation or event.conversation_id
+                if generation is None:
+                    snapshot['conversation']['external.conversation_id'] = event.conversation_id
 
         return snapshot
 

tests/unit_tests/api/service/test_session_context_reset.py

@@ -153,7 +153,7 @@ async def test_reset_starts_new_external_runner_conversation(context_service):
     snapshot = await store.build_snapshot_from_event(event, binding, descriptor)
     generation = await get_reset_generation(engine, 'w', 'b', 'person_u')
     assert isinstance(generation, str) and generation and generation not in {'remote-old', 'person_u'}
-    assert snapshot['conversation']['external.conversation_id'] == generation
+    assert 'external.conversation_id' not in snapshot['conversation']
 
 
 @pytest.mark.asyncio