Compact session feature

crates/code_assistant/resources/compaction_prompt.md

@@ -0,0 +1,8 @@
+<system-compaction>
+The conversation history is nearing the model's context window limit. Provide a thorough summary that allows resuming the task without the earlier messages. Include:
+- The current objectives or tasks.
+- Key actions taken so far and their outcomes.
+- Important files, commands, or decisions that matter for continuing.
+- Outstanding questions or follow-up work that still needs attention.
+Respond with plain text only.
+</system-compaction>

crates/code_assistant/src/acp/agent.rs

@@ -1,4 +1,6 @@
 use agent_client_protocol as acp;
+#[allow(unused_imports)]
+use anyhow::Context;
 use anyhow::Result;
 use serde_json::{json, Map as JsonMap, Value as JsonValue};
 use std::collections::{HashMap, HashSet};
@@ -321,14 +323,12 @@ impl acp::Agent for ACPAgentImpl {
 
             let session_id = {
                 let mut manager = session_manager.lock().await;
+                let session_model_config = SessionModelConfig::new(model_name.clone());
                 manager
                     .create_session_with_config(
                         None,
                         Some(session_config),
-                        Some(SessionModelConfig {
-                            model_name: model_name.clone(),
-                            record_path: None,
-                        }),
+                        Some(session_model_config),
                     )
                     .map_err(|e| {
                         tracing::error!("Failed to create session: {}", e);
@@ -344,13 +344,11 @@ impl acp::Agent for ACPAgentImpl {
             {
                 if model_info.selection_changed {
                     let mut manager = session_manager.lock().await;
-                    if let Err(err) = manager.set_session_model_config(
-                        &session_id,
-                        Some(SessionModelConfig {
-                            model_name: model_info.selected_model_name.clone(),
-                            record_path: None,
-                        }),
-                    ) {
+                    let fallback_model_config =
+                        SessionModelConfig::new(model_info.selected_model_name.clone());
+                    if let Err(err) =
+                        manager.set_session_model_config(&session_id, Some(fallback_model_config))
+                    {
                         tracing::error!(
                             error = ?err,
                             "ACP: Failed to persist fallback model selection for session {}",
@@ -446,16 +444,12 @@ impl acp::Agent for ACPAgentImpl {
                     .map(|config| config.model_name.as_str()),
             ) {
                 if model_info.selection_changed {
-                    let record_path = stored_model_config
-                        .as_ref()
-                        .and_then(|config| config.record_path.clone());
                     let mut manager = session_manager.lock().await;
+                    let fallback_model_config =
+                        SessionModelConfig::new(model_info.selected_model_name.clone());
                     if let Err(err) = manager.set_session_model_config(
                         &arguments.session_id.0,
-                        Some(SessionModelConfig {
-                            model_name: model_info.selected_model_name.clone(),
-                            record_path,
-                        }),
+                        Some(fallback_model_config),
                     ) {
                         tracing::error!(
                             error = ?err,
@@ -541,10 +535,7 @@ impl acp::Agent for ACPAgentImpl {
 
             let session_model_config = match config_result {
                 Ok(Some(config)) => config,
-                Ok(None) => SessionModelConfig {
-                    model_name: model_name.clone(),
-                    record_path: None,
-                },
+                Ok(None) => SessionModelConfig::new(model_name.clone()),
                 Err(e) => {
                     let error_msg = format!(
                         "Failed to load session model configuration for session {}: {e}",
@@ -565,6 +556,7 @@ impl acp::Agent for ACPAgentImpl {
                 &model_name_for_prompt,
                 playback_path,
                 fast_playback,
+                None,
             )
             .await
             {
@@ -813,27 +805,20 @@ impl acp::Agent for ACPAgentImpl {
                 manager.get_session_model_config(&session_id.0)
             };
 
-            let record_path = match existing_config {
-                Ok(Some(config)) => config.record_path,
-                Ok(None) => None,
-                Err(err) => {
-                    tracing::error!(
-                        error = ?err,
-                        "ACP: Failed to read existing session model configuration"
-                    );
-                    return Err(acp::Error::internal_error());
-                }
-            };
+            if let Err(err) = existing_config {
+                tracing::error!(
+                    error = ?err,
+                    "ACP: Failed to read existing session model configuration"
+                );
+                return Err(acp::Error::internal_error());
+            }
 
             {
                 let mut manager = session_manager.lock().await;
-                if let Err(err) = manager.set_session_model_config(
-                    &session_id.0,
-                    Some(SessionModelConfig {
-                        model_name: display_name.clone(),
-                        record_path,
-                    }),
-                ) {
+                let new_model_config = SessionModelConfig::new(display_name.clone());
+                if let Err(err) =
+                    manager.set_session_model_config(&session_id.0, Some(new_model_config))
+                {
                     tracing::error!(
                         error = ?err,
                         "ACP: Failed to persist session model selection"

crates/code_assistant/src/acp/types.rs

@@ -15,6 +15,13 @@ pub fn fragment_to_content_block(fragment: &DisplayFragment) -> acp::ContentBloc
             text: text.clone(),
             meta: None,
         }),
+        DisplayFragment::CompactionDivider { summary } => {
+            acp::ContentBlock::Text(acp::TextContent {
+                annotations: None,
+                text: format!("Conversation compacted:\n{summary}"),
+                meta: None,
+            })
+        }
         DisplayFragment::Image { media_type, data } => {
             acp::ContentBlock::Image(acp::ImageContent {
                 annotations: None,

crates/code_assistant/src/acp/ui.rs

@@ -622,6 +622,7 @@ impl UserInterface for ACPUserUI {
             // Events that don't translate to ACP
             UiEvent::UpdateMemory { .. }
             | UiEvent::SetMessages { .. }
+            | UiEvent::DisplayCompactionSummary { .. }
             | UiEvent::StreamingStarted(_)
             | UiEvent::StreamingStopped { .. }
             | UiEvent::RefreshChatList
@@ -653,6 +654,10 @@ impl UserInterface for ACPUserUI {
                 let content = fragment_to_content_block(fragment);
                 self.queue_session_update(acp::SessionUpdate::AgentMessageChunk { content });
             }
+            DisplayFragment::CompactionDivider { .. } => {
+                let content = fragment_to_content_block(fragment);
+                self.queue_session_update(acp::SessionUpdate::AgentMessageChunk { content });
+            }
             DisplayFragment::ThinkingText(_) => {
                 let content = fragment_to_content_block(fragment);
                 self.queue_session_update(acp::SessionUpdate::AgentThoughtChunk { content });

crates/code_assistant/src/agent/persistence.rs

@@ -118,7 +118,7 @@ impl FileStatePersistence {
         );
         let json = std::fs::read_to_string(&self.state_file_path)?;
         let mut session: ChatSession = serde_json::from_str(&json)?;
-        session.ensure_config();
+        session.ensure_config()?;
 
         info!(
             "Loaded agent state with {} messages",