Compaction overhaul (#5186)

Co-authored-by: Douwe Osinga <douwe@squareup.com>
Co-authored-by: David Katz <dkatz@squareup.com>
Co-authored-by: Alex Hancock <alexhancock@block.xyz>

crates/goose/tests/agent.rs

@@ -117,7 +117,7 @@ async fn run_truncate_test(
     agent.update_provider(provider).await?;
     let repeat_count = context_window + 10_000;
     let large_message_content = "hello ".repeat(repeat_count);
-    let messages = Conversation::new(vec![
+    let conversation = Conversation::new(vec![
         Message::user().with_text("hi there. what is 2 + 2?"),
         Message::assistant().with_text("hey! I think it's 4."),
         Message::user().with_text(&large_message_content),
@@ -130,7 +130,7 @@ async fn run_truncate_test(
     ])
     .unwrap();
 
-    let reply_stream = agent.reply(messages, None, None).await?;
+    let reply_stream = agent.reply(conversation, None, None).await?;
     tokio::pin!(reply_stream);
 
     let mut responses = Vec::new();
@@ -143,8 +143,8 @@ async fn run_truncate_test(
             Ok(AgentEvent::ModelChange { .. }) => {
                 // Model change events are informational, just continue
             }
-            Ok(AgentEvent::HistoryReplaced(_)) => {
-                // Handle history replacement events if needed
+            Ok(AgentEvent::HistoryReplaced(_updated_conversation)) => {
+                // Should update the conversation here, but we're not reading it
             }
             Err(e) => {
                 println!("Error: {:?}", e);
@@ -175,14 +175,6 @@ async fn run_truncate_test(
             assert!(text_content.text.to_lowercase().contains("no"));
             assert!(!text_content.text.to_lowercase().contains("yes"));
         }
-        goose::conversation::message::MessageContent::ContextLengthExceeded(_) => {
-            // This is an acceptable outcome for providers that don't truncate themselves
-            // and correctly report that the context length was exceeded.
-            println!(
-                "Received ContextLengthExceeded as expected for {:?}",
-                provider_type
-            );
-        }
         _ => {
             panic!(
                 "Unexpected message content type: {:?}",
@@ -1119,7 +1111,9 @@ mod max_turns_tests {
                 }
                 Ok(AgentEvent::McpNotification(_)) => {}
                 Ok(AgentEvent::ModelChange { .. }) => {}
-                Ok(AgentEvent::HistoryReplaced(_)) => {}
+                Ok(AgentEvent::HistoryReplaced(_updated_conversation)) => {
+                    // We should update the conversation here, but we're not reading it
+                }
                 Err(e) => {
                     return Err(e);
                 }