feat: handle PostCompact hook event (#225)

Parses [PostCompact Hook] from stderr, emits claude:post-compact, shows
a toast notification, and briefly sets the character to success state.

src-tauri/src/types.rs

@@ -310,6 +310,14 @@ pub struct StopFailureEvent {
     pub conversation_id: Option<String>,
 }
 
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct PostCompactEvent {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub session_id: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub conversation_id: Option<String>,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct AgentStartEvent {
     pub tool_use_id: String,
@@ -697,4 +705,40 @@ mod tests {
         assert!(!serialized.contains("error_type"));
         assert!(!serialized.contains("conversation_id"));
     }
+
+    #[test]
+    fn test_post_compact_event_serialization() {
+        let event = PostCompactEvent {
+            session_id: Some("sess-abc".to_string()),
+            conversation_id: Some("conv-123".to_string()),
+        };
+
+        let serialized = serde_json::to_string(&event).unwrap();
+        assert!(serialized.contains("\"session_id\":\"sess-abc\""));
+        assert!(serialized.contains("\"conversation_id\":\"conv-123\""));
+    }
+
+    #[test]
+    fn test_post_compact_event_omits_none_fields() {
+        let event = PostCompactEvent {
+            session_id: None,
+            conversation_id: None,
+        };
+
+        let serialized = serde_json::to_string(&event).unwrap();
+        assert!(!serialized.contains("session_id"));
+        assert!(!serialized.contains("conversation_id"));
+    }
+
+    #[test]
+    fn test_post_compact_event_partial_fields() {
+        let event = PostCompactEvent {
+            session_id: Some("sess-xyz".to_string()),
+            conversation_id: None,
+        };
+
+        let serialized = serde_json::to_string(&event).unwrap();
+        assert!(serialized.contains("\"session_id\":\"sess-xyz\""));
+        assert!(!serialized.contains("conversation_id"));
+    }
 }

src-tauri/src/wsl_bridge.rs

@@ -17,8 +17,8 @@ use crate::types::{
     AgentEndEvent, AgentStartEvent, CharacterState, ClaudeMessage, ConnectionEvent,
     ConnectionStatus, ContentBlock, ElicitationEvent, ElicitationResultEvent, MessageCost,
     OutputEvent, PermissionPromptEvent, PermissionPromptEventItem, QuestionOption, SessionEvent,
-    StateChangeEvent, StopFailureEvent, TodoItem, TodoUpdateEvent, UserQuestionEvent,
+    PostCompactEvent, StateChangeEvent, StopFailureEvent, TodoItem, TodoUpdateEvent,
-    WorkingDirectoryEvent, WorktreeEvent, WorktreeInfo,
+    UserQuestionEvent, WorkingDirectoryEvent, WorktreeEvent, WorktreeInfo,
 };
 use parking_lot::RwLock;
 use std::cell::RefCell;
@@ -1055,6 +1055,7 @@ fn handle_stderr(
                 let is_elicitation = line.contains("[Elicitation Hook]");
                 let is_elicitation_result = line.contains("[ElicitationResult Hook]");
                 let is_stop_failure = line.contains("[StopFailure Hook]");
+                let is_post_compact = line.contains("[PostCompact Hook]");
 
                 let line_type = if is_worktree_create || is_worktree_remove {
                     "worktree"
@@ -1064,6 +1065,8 @@ fn handle_stderr(
                     "elicitation"
                 } else if is_stop_failure {
                     "error"
+                } else if is_post_compact {
+                    "compact-prompt"
                 } else {
                     "error"
                 };
@@ -1180,6 +1183,28 @@ fn handle_stderr(
                             parent_tool_use_id: None,
                         },
                     );
+                } else if is_post_compact {
+                    let data = parse_post_compact_hook(&line);
+
+                    let _ = app.emit(
+                        "claude:post-compact",
+                        PostCompactEvent {
+                            session_id: data.session_id,
+                            conversation_id: conversation_id.clone(),
+                        },
+                    );
+
+                    let _ = app.emit(
+                        "claude:output",
+                        OutputEvent {
+                            line_type: "compact-prompt".to_string(),
+                            content: "Context compacted — conversation history has been summarised to free up space.".to_string(),
+                            tool_name: None,
+                            conversation_id: conversation_id.clone(),
+                            cost: None,
+                            parent_tool_use_id: None,
+                        },
+                    );
                 } else {
                     let _ = app.emit(
                         "claude:output",
@@ -1383,6 +1408,16 @@ fn build_stop_failure_message(data: &StopFailureData) -> String {
     }
 }
 
+#[derive(Debug)]
+struct PostCompactData {
+    session_id: Option<String>,
+}
+
+fn parse_post_compact_hook(line: &str) -> PostCompactData {
+    let session_id = extract_debug_string_value(line, "session_id");
+    PostCompactData { session_id }
+}
+
 /// Extracts a double-quoted string value from a `key="value"` pair in a hook line.
 /// Handles escape sequences within the quoted value.
 fn extract_quoted_value(line: &str, key: &str) -> Option<String> {
@@ -3509,6 +3544,28 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_parse_post_compact_hook_with_session_id() {
+        let line =
+            r#"[PostCompact Hook] session_id=Some("sess-abc123"), conversation_id=Some("conv-xyz")"#;
+        let data = parse_post_compact_hook(line);
+        assert_eq!(data.session_id, Some("sess-abc123".to_string()));
+    }
+
+    #[test]
+    fn test_parse_post_compact_hook_without_session_id() {
+        let line = "[PostCompact Hook] session_id=None";
+        let data = parse_post_compact_hook(line);
+        assert_eq!(data.session_id, None);
+    }
+
+    #[test]
+    fn test_parse_post_compact_hook_empty_line() {
+        let line = "[PostCompact Hook]";
+        let data = parse_post_compact_hook(line);
+        assert_eq!(data.session_id, None);
+    }
+
     #[test]
     fn test_build_stop_failure_message_no_fields() {
         let data = StopFailureData {

src/lib/tauri.ts

@@ -10,6 +10,7 @@ import type {
   ConnectionStatus,
   ElicitationEvent,
   PermissionPromptEvent,
+  PostCompactEvent,
   StopFailureEvent,
   UserQuestionEvent,
 } from "$lib/types/messages";
@@ -659,6 +660,12 @@ export async function initializeTauriListeners() {
     toastStore.addError(message);
   });
   unlisteners.push(stopFailureUnlisten);
+
+  const postCompactUnlisten = await listen<PostCompactEvent>("claude:post-compact", () => {
+    toastStore.addInfo("Context compacted", "🗜️");
+    characterState.setTemporaryState("success", 2000);
+  });
+  unlisteners.push(postCompactUnlisten);
 }
 
 export function cleanupTauriListeners() {

src/lib/types/messages.ts

@@ -182,6 +182,11 @@ export interface StopFailureEvent {
   conversation_id?: string;
 }
 
+export interface PostCompactEvent {
+  session_id?: string;
+  conversation_id?: string;
+}
+
 export type ConnectionStatus = "disconnected" | "connecting" | "connected" | "error";
 
 export interface Attachment {