combine user and assistant messages for vertex models (#199)

Co-authored-by: aisi-inspect <[email protected]>

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Improved metrics `value_to_float` string conversion (handle numbers, "true", "false", etc.)
 - Log viewer: Ctrl/Cmd+F to find text when running in VS Code.
 - Set Claude default `max_tokens` to 4096
+- Combine user and assistant messages for Vertex models.
 
 ## v0.3.20 (03 August 2024)
 

src/inspect_ai/model/_providers/vertex.py

@@ -140,6 +140,14 @@ def connection_key(self) -> str:
         """Scope for enforcing max_connections (could also use endpoint)."""
         return self.model_name
 
+    @override
+    def collapse_user_messages(self) -> bool:
+        return True
+
+    @override
+    def collapse_assistant_messages(self) -> bool:
+        return True
+
 
 async def as_chat_messages(messages: list[ChatMessage]) -> list[Content]:
     # google does not support system messages so filter them out to start with