[LUM-782] Fix hang in performHealthCheck by caching active assistant

clients/shared/Network/GatewayConnectionManager.swift

@@ -53,14 +53,21 @@ public final class GatewayConnectionManager: ObservableObject {
 
     // MARK: - Connection State (internal)
 
+    #if os(macOS)
+    /// Cached snapshot of the active assistant from the lockfile.
+    /// Refreshed on connect, reconfigure, and when the active assistant changes
+    /// externally (e.g. CLI `vellum use`). Reads from this cache replace the
+    /// synchronous `LockfileAssistant.loadAll()` calls that previously blocked
+    /// the main thread on every health check cycle.
+    private var cachedAssistant: LockfileAssistant?
+    private var assistantChangeObserver: NSObjectProtocol?
+    #endif
+
     /// Whether auto-wake should be attempted on disconnect.
     /// Applies to local and Docker assistants (not remote or managed).
     private var isLocal: Bool {
         #if os(macOS)
-        guard let id = LockfileAssistant.loadActiveAssistantId(),
-              let assistant = LockfileAssistant.loadByName(id) else {
-            return false
-        }
+        guard let assistant = cachedAssistant else { return false }
         return (!assistant.isRemote || assistant.isDocker) && !assistant.isManaged
         #else
         return false
@@ -70,11 +77,7 @@ public final class GatewayConnectionManager: ObservableObject {
     /// Whether the connected assistant is a managed (platform-hosted) assistant.
     private var isManaged: Bool {
         #if os(macOS)
-        guard let id = LockfileAssistant.loadActiveAssistantId(),
-              let assistant = LockfileAssistant.loadByName(id) else {
-            return false
-        }
-        return assistant.isManaged
+        return cachedAssistant?.isManaged ?? false
         #else
         return false
         #endif
@@ -146,6 +149,16 @@ public final class GatewayConnectionManager: ObservableObject {
             // macOS re-reads from disk on each request; no persistence needed here.
             #endif
         }
+
+        #if os(macOS)
+        assistantChangeObserver = NotificationCenter.default.addObserver(
+            forName: LockfileAssistant.activeAssistantDidChange,
+            object: nil,
+            queue: .main
+        ) { [weak self] _ in
+            self?.refreshCachedAssistant()
+        }
+        #endif
     }
 
     // MARK: - Connect
@@ -161,6 +174,11 @@ public final class GatewayConnectionManager: ObservableObject {
         #endif
         disconnectInternal(cancelAutoWake: cancelAutoWake)
 
+        #if os(macOS)
+        refreshCachedAssistant()
+        LockfileAssistant.startWatching()
+        #endif
+
         isConnecting = true
 
         if let conversationKey, !conversationKey.isEmpty {
@@ -255,6 +273,9 @@ public final class GatewayConnectionManager: ObservableObject {
         autoWakeTask?.cancel()
         autoWakeTask = nil
         #endif
+        #if os(macOS)
+        cachedAssistant = nil
+        #endif
         disconnect()
         isAuthenticated = false
         refreshTask?.cancel()
@@ -288,8 +309,12 @@ public final class GatewayConnectionManager: ObservableObject {
 
     private func performHealthCheck() async throws {
         do {
-            let isManaged = (try? GatewayHTTPClient.isConnectionManaged()) ?? false
-            let healthPath = isManaged ? "assistants/{assistantId}/health" : "health"
+            let healthPath: String
+            #if os(macOS)
+            healthPath = (cachedAssistant?.isManaged ?? false) ? "assistants/{assistantId}/health" : "health"
+            #else
+            healthPath = ((try? GatewayHTTPClient.isConnectionManaged()) ?? false) ? "assistants/{assistantId}/health" : "health"
+            #endif
             let response = try await GatewayHTTPClient.get(
                 path: healthPath,
                 timeout: 10,
@@ -307,7 +332,7 @@ public final class GatewayConnectionManager: ObservableObject {
                 if let newVersion = decoded.version, newVersion != assistantVersion {
                     assistantVersion = newVersion
                     #if os(macOS)
-                    if let id = LockfileAssistant.loadActiveAssistantId(), !id.isEmpty {
+                    if let id = cachedAssistant?.assistantId, !id.isEmpty {
                         LockfilePaths.updateServiceGroupVersion(assistantId: id, version: newVersion)
                     }
                     #endif
@@ -498,8 +523,12 @@ public final class GatewayConnectionManager: ObservableObject {
     // MARK: - 401 Recovery
 
     private func handleAuthenticationFailure() {
-        let isManaged = (try? GatewayHTTPClient.isConnectionManaged()) ?? false
-        if isManaged {
+        #if os(macOS)
+        let managedConnection = cachedAssistant?.isManaged ?? false
+        #else
+        let managedConnection = (try? GatewayHTTPClient.isConnectionManaged()) ?? false
+        #endif
+        if managedConnection {
             log.warning("401 in managed mode — session token may be expired")
             eventStreamClient.broadcastMessage(.conversationError(ConversationErrorMessage(
                 conversationId: "",
@@ -704,7 +733,7 @@ public final class GatewayConnectionManager: ObservableObject {
         // Single CLI call replaces direct HTTP calls for broadcast + workspace commit
         Task {
             guard let handler = postSparkleUpdateHandler,
-                  let name = LockfileAssistant.loadActiveAssistantId() else { return }
+                  let name = cachedAssistant?.assistantId ?? LockfileAssistant.loadActiveAssistantId() else { return }
             await handler(name, preUpdateVersion)
         }
     }
@@ -793,10 +822,36 @@ public final class GatewayConnectionManager: ObservableObject {
         }
     }
 
+    // MARK: - Cached Assistant
+
+    #if os(macOS)
+    /// Synchronously refreshes the cached assistant snapshot from the lockfile.
+    /// Called during connect and when `activeAssistantDidChange` fires.
+    private func refreshCachedAssistant() {
+        let id: String?
+        if let activeId = LockfileAssistant.loadActiveAssistantId(), !activeId.isEmpty {
+            id = activeId
+        } else if let legacyId = UserDefaults.standard.string(forKey: "connectedAssistantId"), !legacyId.isEmpty {
+            id = legacyId
+        } else {
+            id = nil
+        }
+        guard let id else {
+            cachedAssistant = nil
+            return
+        }
+        cachedAssistant = LockfileAssistant.loadByName(id)
+    }
+    #endif
+
     deinit {
         #if os(macOS)
         autoWakeTask?.cancel()
         reconnectionTask?.cancel()
+        if let observer = assistantChangeObserver {
+            NotificationCenter.default.removeObserver(observer)
+        }
+        LockfileAssistant.stopWatching()
         #endif
     }
 }