Make compaction transitions recoverable

src/app/generation.rs

@@ -20,13 +20,14 @@ pub(super) struct TitleRequest {
 
 #[cfg(target_os = "macos")]
 pub(super) enum PendingContinuation {
+    None,
     User(String),
     Tool(String),
 }
 
 #[cfg(target_os = "macos")]
 pub(super) struct CompactionRequest {
-    active: ActiveGeneration,
+    pub(super) active: ActiveGeneration,
     pending: PendingContinuation,
 }
 
@@ -92,6 +93,16 @@ impl App {
             return;
         }
         #[cfg(target_os = "macos")]
+        if prompt == "/compact" {
+            self.composer.clear();
+            if let Err(error) =
+                self.start_compaction(PendingContinuation::None, "manual /compact request")
+            {
+                self.error = Some(error);
+            }
+            return;
+        }
+        #[cfg(target_os = "macos")]
         if !std::mem::take(&mut self.skip_compaction_once)
             && crate::compaction::should_compact(self.context_used, self.context_limit)
         {
@@ -466,7 +477,7 @@ impl App {
     }
 
     #[cfg(target_os = "macos")]
-    fn start_compaction(
+    pub(super) fn start_compaction(
         &mut self,
         pending: PendingContinuation,
         reason: &str,
@@ -506,6 +517,10 @@ impl App {
                 effective.turn,
                 messages,
                 reason,
+                session_compaction_checkpoint_path(
+                    self.selected_session
+                        .ok_or_else(|| "The active session is unavailable.".to_owned())?,
+                ),
                 idle_timeout,
             )?;
         self.active_compaction = Some(CompactionRequest { active, pending });
@@ -537,6 +552,7 @@ impl App {
                     match result {
                         Ok(compacted) => {
                             if let Err(error) = self.apply_compaction(&compacted) {
+                                let _ = fs::remove_file(&compacted.checkpoint);
                                 self.generating = false;
                                 self.activity = None;
                                 self.error = Some(error);
@@ -546,6 +562,7 @@ impl App {
                             self.generating = false;
                             self.activity = None;
                             match request.pending {
+                                PendingContinuation::None => {}
                                 PendingContinuation::User(prompt) => {
                                     self.composer = prompt;
                                     self.skip_compaction_once = true;
@@ -595,7 +612,7 @@ impl App {
         let session_id = self
             .selected_session
             .ok_or_else(|| "The active session is unavailable.".to_owned())?;
-        let tail = compacted
+        let mut tail = compacted
             .tail
             .iter()
             .map(|message| crate::database::MessageDraft {
@@ -606,11 +623,32 @@ impl App {
                 content: message.content.clone(),
             })
             .collect::<Vec<_>>();
+        if let Some((tools_session, tools)) = &self.agent_tools
+            && *tools_session == session_id
+            && let Some(observation) = tools
+                .lock()
+                .unwrap_or_else(|poisoned| poisoned.into_inner())
+                .compaction_observation()
+        {
+            tail.push(crate::database::MessageDraft {
+                user: false,
+                tool: true,
+                reasoning: None,
+                reasoning_complete: true,
+                content: observation,
+            });
+        }
         let messages = self
             .database
             .as_mut()
             .ok_or_else(|| "The project database is unavailable.".to_owned())?
-            .replace_with_compacted_transcript(session_id, &compacted.summary, &tail)
+            .replace_with_compacted_transcript(
+                session_id,
+                &compacted.summary,
+                &tail,
+                compacted.context_tokens,
+                self.context_limit,
+            )
             .map_err(|error| format!("Could not save compacted conversation: {error}"))?;
         self.conversation = messages.into_iter().map(ChatMessage::from).collect();
         if let Some(session) = self
@@ -620,8 +658,16 @@ impl App {
             .find(|session| session.id == session_id)
         {
             session.compacted_summary = Some(compacted.summary.clone());
+            session.context_used = compacted.context_tokens as i32;
+            session.context_limit = self.context_limit as i32;
+            session.last_tokens_per_second = None;
         }
-        let _ = fs::remove_file(session_checkpoint_path(session_id));
+        let final_checkpoint = session_checkpoint_path(session_id);
+        fs::rename(&compacted.checkpoint, &final_checkpoint).map_err(|error| {
+            format!(
+                "The compacted conversation was saved, but its checkpoint could not be promoted: {error}. It will rebuild on next use."
+            )
+        })?;
         Ok(())
     }
 

src/app/projects.rs

@@ -196,7 +196,14 @@ mod tests {
         let directory =
             std::env::temp_dir().join(format!("ds4-server-sweep-{}", std::process::id()));
         std::fs::create_dir_all(&directory).unwrap();
-        for name in ["1.bin", "2.bin", "notes.bin", "7.bin"] {
+        for name in [
+            "1.bin",
+            "2.bin",
+            "notes.bin",
+            "7.bin",
+            "1.compacting",
+            "2.tmp",
+        ] {
             std::fs::write(directory.join(name), b"payload").unwrap();
         }
         let projects = vec![ProjectWithSessions {
@@ -213,6 +220,8 @@ mod tests {
         // Not a session checkpoint, so not ours to delete.
         assert!(directory.join("notes.bin").exists());
         assert!(!directory.join("7.bin").exists());
+        assert!(!directory.join("1.compacting").exists());
+        assert!(!directory.join("2.tmp").exists());
         // Nothing left to sweep on the next pass.
         assert!(!super::super::sweep_orphan_checkpoints(
             &directory, &projects

src/app/view.rs

@@ -446,6 +446,10 @@ impl App {
                 .on_press(Message::StartRenameSession(session.id)),
             menu_action(ICON_SPARK, "Retitle with AI")
                 .on_press(Message::RetitleSession(session.id)),
+            menu_action(ICON_SPARK, "Compact context")
+                .on_press(Message::CompactSession(session.id)),
+            menu_action(ICON_ARCHIVE, "Rebuild context on next use")
+                .on_press(Message::RebuildSessionContext(session.id)),
         ]
         .spacing(4);
         actions = match state {