diff --git a/Packages/CmuxAgentChat/Sources/CmuxAgentChat/Parsing/OSC133CommandParser.swift b/Packages/CmuxAgentChat/Sources/CmuxAgentChat/Parsing/OSC133CommandParser.swift
index 06c170f567ab..5d4989a3fa2b 100644
--- a/Packages/CmuxAgentChat/Sources/CmuxAgentChat/Parsing/OSC133CommandParser.swift
+++ b/Packages/CmuxAgentChat/Sources/CmuxAgentChat/Parsing/OSC133CommandParser.swift
@@ -15,7 +15,7 @@ import Foundation
 /// Pure and incremental: ``consume(_:)`` may be fed arbitrary chunk
 /// boundaries, including ones that split an escape sequence (the tail is
 /// carried over). Read ``blocks`` after feeding.
-public final class OSC133CommandParser {
+public struct OSC133CommandParser {
     /// The command blocks parsed so far, oldest first.
     public private(set) var blocks: [TerminalCommandBlock] = []
 
@@ -48,7 +48,7 @@ public final class OSC133CommandParser {
     /// Feeds a chunk of raw terminal output through the state machine.
     ///
     /// - Parameter text: A slice of the PTY stream, any length.
-    public func consume(_ text: String) {
+    public mutating func consume(_ text: String) {
         let stream = pending + text
         pending = ""
         var index = stream.startIndex
@@ -78,7 +78,7 @@ public final class OSC133CommandParser {
 
     /// Publishes the running block's output: the already-folded completed
     /// lines plus the open line folded on its own (O(open line), not O(total)).
-    private func flushOpenOutput() {
+    private mutating func flushOpenOutput() {
         guard phase == .output, let openIndex else { return }
         blocks[openIndex].output = foldedOutput + Self.foldLine(openLine)
     }
@@ -206,7 +206,7 @@ public final class OSC133CommandParser {
 
     // MARK: - State transitions
 
-    private func apply(_ action: EscapeAction) {
+    private mutating func apply(_ action: EscapeAction) {
         switch action {
         case .promptStart:
             finalizeOpenOutput()
@@ -231,7 +231,7 @@ public final class OSC133CommandParser {
         }
     }
 
-    private func appendText(_ char: Character) {
+    private mutating func appendText(_ char: Character) {
         switch phase {
         case .command:
             commandBuffer.append(char)
@@ -251,7 +251,7 @@ public final class OSC133CommandParser {
         }
     }
 
-    private func openBlock() {
+    private mutating func openBlock() {
         let block = TerminalCommandBlock(
             id: nextID,
             command: commandBuffer.trimmingCharacters(in: .whitespacesAndNewlines),
@@ -264,7 +264,7 @@ public final class OSC133CommandParser {
         openIndex = blocks.count - 1
     }
 
-    private func closeBlock(exitCode: Int?) {
+    private mutating func closeBlock(exitCode: Int?) {
         guard let openIndex else { return }
         blocks[openIndex].output = foldedOutput + Self.foldLine(openLine)
         blocks[openIndex].exitCode = exitCode
@@ -274,7 +274,7 @@ public final class OSC133CommandParser {
         openLine = ""
     }
 
-    private func finalizeOpenOutput() {
+    private mutating func finalizeOpenOutput() {
         // A new prompt without a D mark (e.g. Ctrl-C, or a shell that skipped
         // D): close the open block with an unknown exit code.
         if openIndex != nil { closeBlock(exitCode: nil) }
diff --git a/Packages/CmuxAgentChat/Tests/CmuxAgentChatTests/OSC133CommandParserTests.swift b/Packages/CmuxAgentChat/Tests/CmuxAgentChatTests/OSC133CommandParserTests.swift
index 826f45764f13..122716ebd3ff 100644
--- a/Packages/CmuxAgentChat/Tests/CmuxAgentChatTests/OSC133CommandParserTests.swift
+++ b/Packages/CmuxAgentChat/Tests/CmuxAgentChatTests/OSC133CommandParserTests.swift
@@ -12,7 +12,7 @@ struct OSC133CommandParserTests {
 
     @Test("a complete command/output/exit cycle yields one finished block")
     func happyPath() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + "user@host$ " + mark("B") + "echo hi" + mark("C") + "hi\n" + mark("D;0"))
         #expect(parser.blocks.count == 1)
         let block = parser.blocks[0]
@@ -25,7 +25,7 @@ struct OSC133CommandParserTests {
 
     @Test("a nonzero exit code marks the block failed")
     func failure() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "false" + mark("C") + mark("D;1"))
         #expect(parser.blocks[0].exitCode == 1)
         #expect(parser.blocks[0].failed)
@@ -33,7 +33,7 @@ struct OSC133CommandParserTests {
 
     @Test("a block with no D mark stays running until the next prompt closes it")
     func runningUntilNextPrompt() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "sleep 5" + mark("C") + "working")
         #expect(parser.blocks.count == 1)
         #expect(parser.blocks[0].isRunning)
@@ -46,7 +46,7 @@ struct OSC133CommandParserTests {
 
     @Test("two commands produce two blocks with distinct ids")
     func twoCommands() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "ls" + mark("C") + "a b\n" + mark("D;0"))
         parser.consume(mark("A") + mark("B") + "pwd" + mark("C") + "/tmp\n" + mark("D;0"))
         #expect(parser.blocks.count == 2)
@@ -57,7 +57,7 @@ struct OSC133CommandParserTests {
 
     @Test("an escape sequence split across chunks is parsed once completed")
     func splitEscape() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         let full = mark("A") + mark("B") + "id" + mark("C") + "uid=0\n" + mark("D;0")
         let mid = full.index(full.startIndex, offsetBy: 3)
         parser.consume(String(full[..<mid]))
@@ -70,7 +70,7 @@ struct OSC133CommandParserTests {
 
     @Test("streaming output updates the running block incrementally")
     func streaming() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "build" + mark("C"))
         parser.consume("step 1\n")
         #expect(parser.blocks[0].output == "step 1\n")
@@ -83,21 +83,21 @@ struct OSC133CommandParserTests {
 
     @Test("carriage-return progress redraws fold to the final per-line state")
     func carriageReturnFold() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "dl" + mark("C") + "10%\r50%\r100%\n" + mark("D;0"))
         #expect(parser.blocks[0].output == "100%\n")
     }
 
     @Test("entering the alt screen flags the running block interactive")
     func altScreen() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "vim" + mark("C") + "\u{1b}[?1049h")
         #expect(parser.blocks[0].isInteractive)
     }
 
     @Test("non-133 OSC and CSI sequences are stripped from output")
     func stripsOtherSequences() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         // OSC 0 (window title) + SGR color around the text.
         let noise = "\u{1b}]0;my title\u{07}" + "\u{1b}[31mred\u{1b}[0m"
         parser.consume(mark("A") + mark("B") + "x" + mark("C") + noise + "\n" + mark("D;0"))
@@ -106,28 +106,28 @@ struct OSC133CommandParserTests {
 
     @Test("CRLF line endings are preserved, not blanked")
     func crlfPreserved() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "x" + mark("C") + "line1\r\nline2\r\n" + mark("D;0"))
         #expect(parser.blocks[0].output == "line1\nline2\n")
     }
 
     @Test("a CR progress redraw still folds even with surrounding CRLF lines")
     func crlfAndProgressMix() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "x" + mark("C") + "start\r\n10%\r99%\r100%\r\ndone\r\n" + mark("D;0"))
         #expect(parser.blocks[0].output == "start\n100%\ndone\n")
     }
 
     @Test("alt screen batched with other private modes is still detected")
     func batchedAltScreen() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "tmux" + mark("C") + "\u{1b}[?1049;2004h")
         #expect(parser.blocks[0].isInteractive)
     }
 
     @Test("an unterminated OSC does not hang and the parser resyncs after it")
     func unterminatedOSCResyncs() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         // A title OSC with no terminator, far longer than the escape cap.
         let junk = "\u{1b}]0;" + String(repeating: "x", count: 9000)
         parser.consume(mark("A") + mark("B") + "echo" + mark("C") + junk)
@@ -140,7 +140,7 @@ struct OSC133CommandParserTests {
 
     @Test("large output is folded once and parses correctly")
     func largeOutput() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         let big = (1...2000).map { "line \($0)" }.joined(separator: "\n")
         parser.consume(mark("A") + mark("B") + "seq" + mark("C") + big + "\n" + mark("D;0"))
         #expect(parser.blocks[0].output == big + "\n")
@@ -149,7 +149,7 @@ struct OSC133CommandParserTests {
 
     @Test("a CRLF split across consume chunks is not blanked")
     func crlfSplitAcrossChunks() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + "x" + mark("C") + "ab\r")
         // mid-stream the open line looks cleared, but the bytes are retained
         parser.consume("\ncd\r\n" + mark("D;0"))
@@ -158,7 +158,7 @@ struct OSC133CommandParserTests {
 
     @Test("output fed one character at a time parses identically (incremental fold)")
     func byteAtATimeStreaming() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         let full = mark("A") + mark("B") + "run" + mark("C")
             + "start\r\n10%\r99%\r100%\r\ndone\r\n" + mark("D;0")
         for char in full {
@@ -172,7 +172,7 @@ struct OSC133CommandParserTests {
 
     @Test("a bare prompt with no command yields an empty command string")
     func bareCommand() {
-        let parser = OSC133CommandParser()
+        var parser = OSC133CommandParser()
         parser.consume(mark("A") + mark("B") + mark("C") + mark("D;0"))
         #expect(parser.blocks[0].command.isEmpty)
         #expect(parser.blocks[0].output.isEmpty)
diff --git a/Resources/Localizable.xcstrings b/Resources/Localizable.xcstrings
index 31c1c8cf643e..df82cf4aabcb 100644
--- a/Resources/Localizable.xcstrings
+++ b/Resources/Localizable.xcstrings
@@ -201790,6 +201790,23 @@
         }
       }
     },
+    "mobile.chat.error.serviceUnavailable": {
+      "extractionState": "manual",
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Agent chat transcript service is not configured"
+          }
+        },
+        "ja": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "エージェントチャットのトランスクリプトサービスが設定されていません"
+          }
+        }
+      }
+    },
     "mobile.chat.error.transcriptNotReadable": {
       "extractionState": "manual",
       "localizations": {
diff --git a/Sources/AppDelegate.swift b/Sources/AppDelegate.swift
index db50b9b1c43d..3b2865c9d950 100644
--- a/Sources/AppDelegate.swift
+++ b/Sources/AppDelegate.swift
@@ -790,7 +790,7 @@ final class AppDelegate: NSObject, NSApplicationDelegate, UNUserNotificationCent
     /// Strongly-held observers for every active TabManager. Each observer owns
     /// Combine subscriptions that publish workspace.updated to mobile clients.
     private var mobileWorkspaceListObservers: [ObjectIdentifier: MobileWorkspaceListObserver] = [:]
-
+    private let agentChatTranscriptService = AgentChatTranscriptService()
     /// The app's settings dependency container, handed over by `cmuxApp` via
     /// `configure(...)` before any main window is created. AppKit builds the
     /// main window's `NSHostingView` itself, so it injects this into the
@@ -1986,14 +1986,12 @@ final class AppDelegate: NSObject, NSApplicationDelegate, UNUserNotificationCent
         MobileHostService.shared.configure(auth: auth.coordinator)
         DeviceRegistryClient.shared.configure(auth: auth.coordinator)
         PresenceHeartbeatClient.shared.configure(auth: auth.coordinator)
-        TerminalController.shared.attachAuth(
-            coordinator: auth.coordinator,
-            browserSignIn: auth.browserSignIn
-        )
+        TerminalController.shared.attachAuth(coordinator: auth.coordinator, browserSignIn: auth.browserSignIn)
+        TerminalController.shared.agentChatTranscriptService = agentChatTranscriptService
         auth.start()
         ensureMobileWorkspaceListObserver(for: tabManager)
         MobileTerminalRenderObserver.shared.start()
-        AgentChatTranscriptService.shared.start()
+        agentChatTranscriptService.start { TerminalController.shared.adoptDetectedAgentSessions(workspaceID: $0) }
         installMobileHostSettingsObserver()
         scheduleGhosttyCrashBreadcrumbIfNeeded(notificationStore: notificationStore)
         disableSuddenTerminationIfNeeded()
diff --git a/Sources/ContentView.swift b/Sources/ContentView.swift
index 918b19e1b507..85d476ff9ad9 100644
--- a/Sources/ContentView.swift
+++ b/Sources/ContentView.swift
@@ -2647,8 +2647,7 @@ struct ContentView: View {
         })
 
         view = AnyView(view.onReceive(NotificationCenter.default.publisher(for: .ghosttyDidSetTitle)) { notification in
-            guard let tabId = notification.userInfo?[GhosttyNotificationKey.tabId] as? UUID,
-                  tabId == tabManager.selectedTabId else { return }
+            guard GhosttyTitleChange(notification: notification)?.tabId == tabManager.selectedTabId else { return }
             scheduleTitlebarTextRefresh()
         })
 
diff --git a/Sources/GhosttyTerminalView.swift b/Sources/GhosttyTerminalView.swift
index a40dd735ebc9..9e1132168a30 100644
--- a/Sources/GhosttyTerminalView.swift
+++ b/Sources/GhosttyTerminalView.swift
@@ -3279,15 +3279,12 @@ class GhosttyApp {
                 .flatMap { String(cString: $0) } ?? ""
             if let tabId = surfaceView.tabId,
                let surfaceId = surfaceView.terminalSurface?.id {
+                let change = GhosttyTitleChange(tabId: tabId, surfaceId: surfaceId, title: title)
                 DispatchQueue.main.async {
                     NotificationCenter.default.post(
                         name: .ghosttyDidSetTitle,
                         object: surfaceView,
-                        userInfo: [
-                            GhosttyNotificationKey.tabId: tabId,
-                            GhosttyNotificationKey.surfaceId: surfaceId,
-                            GhosttyNotificationKey.title: title,
-                        ]
+                        userInfo: change.userInfo
                     )
                 }
             }
diff --git a/Sources/GhosttyTitleChange.swift b/Sources/GhosttyTitleChange.swift
new file mode 100644
index 000000000000..b42f63ffcf41
--- /dev/null
+++ b/Sources/GhosttyTitleChange.swift
@@ -0,0 +1,31 @@
+import Foundation
+
+/// Typed payload for `.ghosttyDidSetTitle` notifications.
+struct GhosttyTitleChange: Equatable, Sendable {
+    let tabId: UUID
+    let surfaceId: UUID
+    let title: String
+
+    init(tabId: UUID, surfaceId: UUID, title: String) {
+        self.tabId = tabId
+        self.surfaceId = surfaceId
+        self.title = title
+    }
+
+    init?(notification: Notification) {
+        guard let tabId = notification.userInfo?[GhosttyNotificationKey.tabId] as? UUID,
+              let surfaceId = notification.userInfo?[GhosttyNotificationKey.surfaceId] as? UUID,
+              let title = notification.userInfo?[GhosttyNotificationKey.title] as? String else {
+            return nil
+        }
+        self.init(tabId: tabId, surfaceId: surfaceId, title: title)
+    }
+
+    var userInfo: [String: Any] {
+        [
+            GhosttyNotificationKey.tabId: tabId,
+            GhosttyNotificationKey.surfaceId: surfaceId,
+            GhosttyNotificationKey.title: title,
+        ]
+    }
+}
diff --git a/Sources/GhosttyTitleChangeSubscription.swift b/Sources/GhosttyTitleChangeSubscription.swift
new file mode 100644
index 000000000000..fac1b9c530ae
--- /dev/null
+++ b/Sources/GhosttyTitleChangeSubscription.swift
@@ -0,0 +1,28 @@
+import Foundation
+
+/// Owns a `.ghosttyDidSetTitle` observer and delivers typed title changes.
+final class GhosttyTitleChangeSubscription {
+    private let center: NotificationCenter
+    private let observer: NSObjectProtocol
+
+    init(
+        center: NotificationCenter = .default,
+        handler: @escaping @MainActor (GhosttyTitleChange) -> Void
+    ) {
+        self.center = center
+        observer = center.addObserver(
+            forName: Notification.Name.ghosttyDidSetTitle,
+            object: nil,
+            queue: .main
+        ) { notification in
+            guard let change = GhosttyTitleChange(notification: notification) else { return }
+            Task { @MainActor in
+                handler(change)
+            }
+        }
+    }
+
+    deinit {
+        center.removeObserver(observer)
+    }
+}
diff --git a/Sources/Mobile/AgentChat/AgentChatTranscriptService.swift b/Sources/Mobile/AgentChat/AgentChatTranscriptService.swift
index 636c7a17b156..fcd19f3c2591 100644
--- a/Sources/Mobile/AgentChat/AgentChatTranscriptService.swift
+++ b/Sources/Mobile/AgentChat/AgentChatTranscriptService.swift
@@ -7,14 +7,6 @@ import Foundation
 /// `chat.message` events to subscribed mobile clients.
 @MainActor
 final class AgentChatTranscriptService {
-    /// Process-wide instance, mirroring the sibling mobile host services
-    /// (`MobileHostService.shared`, `MobileTerminalRenderObserver.shared`)
-    /// that the socket dispatch reaches statically. lint:allow
-    static let shared = AgentChatTranscriptService(
-        registry: AgentChatSessionRegistry(),
-        resolver: AgentChatTranscriptResolver()
-    )
-
     /// The push topic chat clients subscribe to.
     static let eventTopic = "chat.message"
 
@@ -32,17 +24,25 @@ final class AgentChatTranscriptService {
     /// title-detected claude has not yet written its transcript; a successful
     /// adoption removes the entry.
     private var detectionScanAt: [String: Date] = [:]
+    private var ghosttyTitleSubscription: GhosttyTitleChangeSubscription?
     private static let detectionScanThrottle: TimeInterval = 4
     private static let provisionalClaudeSessionIDPrefix = "detected-claude-surface-"
 
-    /// Creates the service.
+    /// Creates the service with a hook-store-backed registry.
+    ///
+    /// - Parameter resolver: Transcript path resolver.
+    convenience init(resolver: AgentChatTranscriptResolver = AgentChatTranscriptResolver()) {
+        self.init(registry: AgentChatSessionRegistry(), resolver: resolver)
+    }
+
+    /// Creates the service with explicit dependencies.
     ///
     /// - Parameters:
-    ///   - registry: Session registry; defaults to a hook-store-backed one.
+    ///   - registry: Session registry.
     ///   - resolver: Transcript path resolver.
     init(
         registry: AgentChatSessionRegistry,
-        resolver: AgentChatTranscriptResolver
+        resolver: AgentChatTranscriptResolver = AgentChatTranscriptResolver()
     ) {
         self.registry = registry
         self.resolver = resolver
@@ -53,9 +53,13 @@ final class AgentChatTranscriptService {
 
     /// Seeds the session registry from the on-disk hook stores. Call once
     /// at app startup.
-    func start() {
+    ///
+    /// - Parameter adoptDetectedAgentSessions: Composition-root callback that
+    ///   adopts a title-detected agent for the workspace whose title changed.
+    func start(adoptDetectedAgentSessions: @escaping @MainActor (String) -> Void) {
+        guard ghosttyTitleSubscription == nil else { return }
         registry.seedFromHookStores()
-        observeAgentTitleChanges()
+        observeAgentTitleChanges(adoptDetectedAgentSessions: adoptDetectedAgentSessions)
     }
 
     /// Watches terminal title changes so a coding agent launched without a
@@ -63,20 +67,12 @@ final class AgentChatTranscriptService {
     /// adopted the instant its terminal title becomes the agent's (e.g.
     /// "✳ Claude Code"), not only when the workspace is next opened. Adoption
     /// emits a descriptor change, which pushes the toggle to listening phones.
-    private func observeAgentTitleChanges() {
-        NotificationCenter.default.addObserver(
-            forName: .ghosttyDidSetTitle,
-            object: nil,
-            queue: .main
-        ) { notification in
-            guard let tabId = notification.userInfo?[GhosttyNotificationKey.tabId] as? UUID,
-                  let title = notification.userInfo?[GhosttyNotificationKey.title] as? String,
-                  title.lowercased().contains("claude") else {
+    private func observeAgentTitleChanges(adoptDetectedAgentSessions: @escaping @MainActor (String) -> Void) {
+        ghosttyTitleSubscription = GhosttyTitleChangeSubscription { change in
+            guard change.title.lowercased().contains("claude") else {
                 return
             }
-            MainActor.assumeIsolated {
-                TerminalController.shared.adoptDetectedAgentSessions(workspaceID: tabId.uuidString)
-            }
+            adoptDetectedAgentSessions(change.tabId.uuidString)
         }
     }
 
diff --git a/Sources/TabManager.swift b/Sources/TabManager.swift
index 93a0c3918329..bd50044d32f6 100644
--- a/Sources/TabManager.swift
+++ b/Sources/TabManager.swift
@@ -560,10 +560,8 @@ class TabManager: ObservableObject {
         ) { [weak self] notification in
             MainActor.assumeIsolated { [weak self] in
                 guard let self else { return }
-                guard let tabId = notification.userInfo?[GhosttyNotificationKey.tabId] as? UUID else { return }
-                guard let surfaceId = notification.userInfo?[GhosttyNotificationKey.surfaceId] as? UUID else { return }
-                guard let title = notification.userInfo?[GhosttyNotificationKey.title] as? String else { return }
-                enqueuePanelTitleUpdate(tabId: tabId, panelId: surfaceId, title: title)
+                guard let change = GhosttyTitleChange(notification: notification) else { return }
+                enqueuePanelTitleUpdate(tabId: change.tabId, panelId: change.surfaceId, title: change.title)
             }
         })
         observers.append(NotificationCenter.default.addObserver(
diff --git a/Sources/TerminalController+MobileChat.swift b/Sources/TerminalController+MobileChat.swift
index 0e0c9d9477f9..d17efc273c06 100644
--- a/Sources/TerminalController+MobileChat.swift
+++ b/Sources/TerminalController+MobileChat.swift
@@ -18,6 +18,15 @@ extension TerminalController {
         )
     }
 
+    /// Error shown when the Mac-side chat service is not wired into this
+    /// process. Surfaces in mobile RPC error banners and debug responses.
+    static var chatServiceUnavailableErrorMessage: String {
+        String(
+            localized: "mobile.chat.error.serviceUnavailable",
+            defaultValue: "Agent chat transcript service is not configured"
+        )
+    }
+
     /// Routes one `mobile.chat.*` method to its handler (single dispatch
     /// case in `mobileHostHandleRPC` keeps the god-file growth flat).
     func v2MobileChatDispatch(method: String, params: [String: Any]) async -> V2CallResult {
@@ -43,14 +52,19 @@ extension TerminalController {
     /// full chat-session registry state, for diagnosing inconsistent
     /// phone-side states.
     func v2ChatSessionsDump() -> V2CallResult {
-        .ok(["sessions": AgentChatTranscriptService.shared.debugSessionDump()])
+        guard let service = agentChatTranscriptService else {
+            return .err(code: "unavailable", message: Self.chatServiceUnavailableErrorMessage, data: nil)
+        }
+        return .ok(["sessions": service.debugSessionDump()])
     }
 
     /// `mobile.chat.sessions`: list chat-capable coding-agent sessions,
     /// optionally scoped to one workspace.
     func v2MobileChatSessions(params: [String: Any]) -> V2CallResult {
         let workspaceID = v2String(params, "workspace_id")
-        let service = AgentChatTranscriptService.shared
+        guard let service = agentChatTranscriptService else {
+            return .err(code: "unavailable", message: Self.chatServiceUnavailableErrorMessage, data: nil)
+        }
         // Register coding agents cmux detects by terminal title but that never
         // ran a hook (e.g. launched through a shell wrapper that bypasses
         // cmux's hook injection), so they get a chat session and toggle like
@@ -89,7 +103,7 @@ extension TerminalController {
     /// workspace touches no filesystem.
     func adoptDetectedAgentSessions(workspace: Workspace) {
         let workspaceID = workspace.id.uuidString
-        let service = AgentChatTranscriptService.shared
+        guard let service = agentChatTranscriptService else { return }
         for panel in workspace.panels.values.compactMap({ $0 as? TerminalPanel }) {
             let context = WorkspaceContentView.terminalAgentContext(panel: panel, workspace: workspace)
             let title = workspace.panelTitle(panelId: panel.id) ?? panel.displayTitle
@@ -121,7 +135,9 @@ extension TerminalController {
         }
         let limit = min(max(v2Int(params, "limit") ?? 100, 1), 200)
         let beforeSeq = v2Int(params, "before_seq")
-        let service = AgentChatTranscriptService.shared
+        guard let service = agentChatTranscriptService else {
+            return .err(code: "unavailable", message: Self.chatServiceUnavailableErrorMessage, data: nil)
+        }
         var page = await service.history(sessionID: sessionID, beforeSeq: beforeSeq, limit: limit)
         if page == nil, let staleRecord = service.sessionRecord(sessionID: sessionID) {
             // The record exists but its transcript didn't resolve — the
@@ -132,7 +148,7 @@ extension TerminalController {
             #if DEBUG
             cmuxDebugLog("mobile.chat.history transcript unresolved session=\(sessionID.prefix(8)); refreshing bindings")
             #endif
-            let refreshed = AgentChatTranscriptService.shared.refreshSessionBindings(sessionID: sessionID)
+            let refreshed = service.refreshSessionBindings(sessionID: sessionID)
             if refreshed?.transcriptPath != staleRecord.transcriptPath
                 || refreshed?.workingDirectory != staleRecord.workingDirectory {
                 page = await service.history(sessionID: sessionID, beforeSeq: beforeSeq, limit: limit)
@@ -294,7 +310,7 @@ extension TerminalController {
     /// retried. If it still doesn't resolve we fail with an actionable error
     /// rather than redirect the prompt to some other terminal.
     private func mobileChatTerminalParams(sessionID: String) -> [String: Any]? {
-        let service = AgentChatTranscriptService.shared
+        guard let service = agentChatTranscriptService else { return nil }
         guard let record = service.sessionRecord(sessionID: sessionID),
               let workspaceID = record.workspaceID else {
             return nil
diff --git a/Sources/TerminalController.swift b/Sources/TerminalController.swift
index 6ea874349bb2..8f4bd117744d 100644
--- a/Sources/TerminalController.swift
+++ b/Sources/TerminalController.swift
@@ -108,6 +108,7 @@ class TerminalController {
     /// listener starts. Socket auth commands read these on the main actor.
     @MainActor private(set) var authCoordinator: AuthCoordinator?
     @MainActor private(set) var browserSignInFlow: HostBrowserSignInFlow?
+    @MainActor var agentChatTranscriptService: AgentChatTranscriptService?
     // Sendable value type; injected at construction so socket auth never reaches a global.
     private nonisolated let passwordStore: SocketControlPasswordStore
     /// Process-wide proxy-tunnel broker (one shared tunnel per remote transport across all
@@ -329,7 +330,6 @@ class TerminalController {
             }
         }
     }
-
     nonisolated func currentSocketPathForRemoteRestore() -> String? {
         socketServer.currentSocketPathForRemoteRestore()
     }
@@ -5312,7 +5312,7 @@ class TerminalController {
 
         CmuxEventBus.shared.publishWorkstreamEvent(event, phase: "received")
         v2ApplyIMessageModeSideEffects(for: event)
-        Task { @MainActor in AgentChatTranscriptService.shared.noteHookEvent(event) }
+        Task { @MainActor in self.agentChatTranscriptService?.noteHookEvent(event) }
 
         let result = FeedCoordinator.shared.ingestBlocking(
             event: event,
diff --git a/cmux.xcodeproj/project.pbxproj b/cmux.xcodeproj/project.pbxproj
index ba74ee689ced..599bbaeb6c79 100644
--- a/cmux.xcodeproj/project.pbxproj
+++ b/cmux.xcodeproj/project.pbxproj
@@ -457,6 +457,8 @@
 		D0B1000AA1B2C3D4E5F60001 /* GhosttyTerminalViewSupport.swift in Sources */ = {isa = PBXBuildFile; fileRef = D0B1000BA1B2C3D4E5F60001 /* GhosttyTerminalViewSupport.swift */; };
 		D7AB34400000000000000003 /* GhosttyTerminalViewVisibilityPolicyTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D7AB34400000000000000004 /* GhosttyTerminalViewVisibilityPolicyTests.swift */; };
 		D3284101A1B2C3D4E5F60718 /* GhosttyTextInputSupport.swift in Sources */ = {isa = PBXBuildFile; fileRef = D3284102A1B2C3D4E5F60718 /* GhosttyTextInputSupport.swift */; };
+		D7C6F5000000000000000000 /* GhosttyTitleChange.swift in Sources */ = {isa = PBXBuildFile; fileRef = D7C6F5000000000000000001 /* GhosttyTitleChange.swift */; };
+		D7C6F5010000000000000000 /* GhosttyTitleChangeSubscription.swift in Sources */ = {isa = PBXBuildFile; fileRef = D7C6F5010000000000000001 /* GhosttyTitleChangeSubscription.swift */; };
 		3865A0023865A0023865A002 /* GlobalSearchCoordinator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3865B0023865B0023865B002 /* GlobalSearchCoordinator.swift */; };
 		3865A0073865A0073865A007 /* GlobalSearchDocuments.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3865B0073865B0073865B007 /* GlobalSearchDocuments.swift */; };
 		3865A0083865A0083865A008 /* GlobalSearchPanelCaptureManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3865B0083865B0083865B008 /* GlobalSearchPanelCaptureManager.swift */; };
@@ -1399,6 +1401,8 @@
 		D0B1000BA1B2C3D4E5F60001 /* GhosttyTerminalViewSupport.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GhosttyTerminalViewSupport.swift; sourceTree = "<group>"; };
 		D7AB34400000000000000004 /* GhosttyTerminalViewVisibilityPolicyTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GhosttyTerminalViewVisibilityPolicyTests.swift; sourceTree = "<group>"; };
 		D3284102A1B2C3D4E5F60718 /* GhosttyTextInputSupport.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GhosttyTextInputSupport.swift; sourceTree = "<group>"; };
+		D7C6F5000000000000000001 /* GhosttyTitleChange.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GhosttyTitleChange.swift; sourceTree = "<group>"; };
+		D7C6F5010000000000000001 /* GhosttyTitleChangeSubscription.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GhosttyTitleChangeSubscription.swift; sourceTree = "<group>"; };
 		3865B0023865B0023865B002 /* GlobalSearchCoordinator.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Search/GlobalSearchCoordinator.swift; sourceTree = "<group>"; };
 		3865B0073865B0073865B007 /* GlobalSearchDocuments.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Search/GlobalSearchDocuments.swift; sourceTree = "<group>"; };
 		3865B0083865B0083865B008 /* GlobalSearchPanelCaptureManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Search/GlobalSearchPanelCaptureManager.swift; sourceTree = "<group>"; };
@@ -2168,6 +2172,8 @@
 				3023B1013023B1013023B101 /* ConfigSettingsView.swift */,
 				A11EAB000000000000000001 /* AppearanceSettings.swift */,
 				A11EAC000000000000000001 /* GhosttyTerminalAppearance.swift */,
+				D7C6F5000000000000000001 /* GhosttyTitleChange.swift */,
+				D7C6F5010000000000000001 /* GhosttyTitleChangeSubscription.swift */,
 				A11EAD000000000000000001 /* WorkspaceAppearanceResolution.swift */,
 				A5001011 /* cmuxApp.swift */,
 				C46790000000000000000004 /* CLIForwardingLaunchRouter.swift */,
@@ -3641,6 +3647,8 @@
 				A5001005 /* GhosttyTerminalView.swift in Sources */,
 				D0B1000AA1B2C3D4E5F60001 /* GhosttyTerminalViewSupport.swift in Sources */,
 				D3284101A1B2C3D4E5F60718 /* GhosttyTextInputSupport.swift in Sources */,
+				D7C6F5000000000000000000 /* GhosttyTitleChange.swift in Sources */,
+				D7C6F5010000000000000000 /* GhosttyTitleChangeSubscription.swift in Sources */,
 					3865A0023865A0023865A002 /* GlobalSearchCoordinator.swift in Sources */,
 				3865A0073865A0073865A007 /* GlobalSearchDocuments.swift in Sources */,
 				3865A0083865A0083865A008 /* GlobalSearchPanelCaptureManager.swift in Sources */,