Stream agent prose to the iOS chat as it generates (default-off)

.github/swift-file-length-budget.tsv

@@ -102,8 +102,8 @@
 905	Sources/CmuxSSHURLRequest.swift
 899	Sources/Panels/MarkdownWebRenderer.swift
 885	Sources/Panels/TerminalPanel.swift
+948	Packages/Shared/CmuxAgentChat/Tests/CmuxAgentChatTests/ChatConversationStoreTests.swift
 885	cmuxTests/SidebarWorkspaceDropPlannerTests.swift
-877	Packages/Shared/CmuxAgentChat/Tests/CmuxAgentChatTests/ChatConversationStoreTests.swift
 871	cmuxTests/ClaudeHookSurfaceResolutionSwiftTests.swift
 868	Sources/Panels/BrowserScreenshotSnapshotter.swift
 859	Packages/macOS/CmuxControlSocket/Sources/CmuxControlSocket/Coordinator/Workspace/ControlCommandCoordinator+Workspace.swift
@@ -129,8 +129,8 @@
 752	cmuxUITests/CloseWorkspaceCmdDUITests.swift
 739	cmuxTests/CLICodexHookTimeoutRegressionTests.swift
 738	Packages/macOS/CMUXProjectModel/Sources/CMUXProjectModel/XcodeProjectAdapter.swift
-724	Sources/Panels/BrowserPopupWindowController.swift
-722	Packages/Shared/CmuxAgentChat/Sources/CmuxAgentChat/Store/ChatConversationStore.swift
+725	Sources/Panels/BrowserPopupWindowController.swift
+764	Packages/Shared/CmuxAgentChat/Sources/CmuxAgentChat/Store/ChatConversationStore.swift
 718	Packages/Shared/CmuxAuthRuntime/Sources/CmuxAuthRuntime/Coordinator/AuthCoordinator.swift
 716	Sources/TaskManagerSnapshot.swift
 715	Sources/AppleScriptSupport.swift
@@ -214,6 +214,7 @@
 526	Packages/macOS/CMUXAgentLaunch/Sources/CMUXAgentLaunch/Workstream/WorkstreamStore.swift
 525	Packages/macOS/CmuxSettings/Sources/CmuxSettings/SocketControl/SocketControlSettings.swift
 524	CLI/CMUXCLI+AutoNaming.swift
+524	Sources/Mobile/AgentChat/AgentChatTranscriptService.swift
 520	CLI/CMUXCLI+AmpExtension.swift
 520	cmuxTests/MainWindowVisibilityControllerTests.swift
 519	Packages/macOS/CmuxSwiftRender/Tests/CmuxSwiftRenderTests/Corpus/stress-two-column-cockpit-sidebar.swift
@@ -225,11 +226,11 @@
 509	Packages/macOS/CMUXAgentLaunch/Sources/CMUXAgentLaunch/AgentLaunchSanitizerAdditionalPolicies.swift
 507	Sources/TerminalControllerTopSupport.swift
 506	Sources/App/MainWindowVisibilityController.swift
+518	Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/CMUXMobileRootView.swift
 505	cmuxUITests/DisplayResolutionRegressionUITests.swift
 504	cmuxTests/TerminalNotificationSocketActionTests.swift
 503	Sources/Settings/ConfigSource.swift
 502	Sources/CmuxEventPublishing.swift
 502	Sources/RemoteTmuxSessionMirror.swift
-500	Packages/iOS/CmuxMobileShellUI/Sources/CmuxMobileShellUI/CMUXMobileRootView.swift
 500	Packages/macOS/CmuxControlSocket/Tests/CmuxControlSocketTests/ControlCommandContextTestStubs.swift
 500	Sources/KeyboardShortcutRecorder.swift

Packages/Shared/CmuxAgentChat/Sources/CmuxAgentChat/Source/FixtureChatEventSource.swift

@@ -147,6 +147,10 @@ public actor FixtureChatEventSource: ChatEventSource {
         case .reset:
             backlog = []
             terminalBacklog = []
+        case .streamingProse:
+            // A live preview is transient and not part of history; forward it to
+            // subscribers but never fold it into the backlog.
+            break
         case .unknown:
             break
         case .stateChanged, .descriptorChanged:

Packages/Shared/CmuxAgentChat/Sources/CmuxAgentChat/Store/ChatConversationStore.swift

@@ -60,6 +60,14 @@ public final class ChatConversationStore {
 
     @ObservationIgnored private var messages: [ChatMessage] = []
     @ObservationIgnored private var pending: [ChatPendingOutbound] = []
+    /// Live, not-yet-committed preview of the agent's in-progress prose for the
+    /// current turn, scraped from the rendered terminal screen. Held outside
+    /// ``messages`` (so it never collides with window dedup/paging/seq) and
+    /// rendered as a trailing agent bubble. Cleared the instant the authoritative
+    /// agent prose lands via ``ChatSessionEvent/appended`` or an explicit
+    /// ``ChatSessionEvent/streamingProse`` `nil`, so it never duplicates a real
+    /// message.
+    @ObservationIgnored private var streamingMessage: ChatMessage?
     @ObservationIgnored private var firstUnreadSeq: Int?
     /// Terminal command-blocks for a `.terminal`-kind session, upserted by
     /// id; `terminalBlockOrder` preserves arrival order. Unused (and the
@@ -458,6 +466,13 @@ public final class ChatConversationStore {
         switch event {
         case .appended(let newMessages):
             reconcilePending(against: newMessages)
+            // The authoritative agent prose for the in-flight turn just landed:
+            // drop the live preview so the committed message takes over with no
+            // duplicate, even if the host's explicit clear is delayed or lost.
+            if streamingMessage != nil,
+               newMessages.contains(where: { $0.role == .agent && Self.isProse($0) }) {
+                streamingMessage = nil
+            }
             // A live append whose seq regresses below the window tail means
             // the transcript was truncated/replaced and the tailer reset;
             // appending would corrupt window ordering. Re-anchor instead.
@@ -499,6 +514,14 @@ public final class ChatConversationStore {
             // optimistic pending row it came from so it doesn't linger or leak.
             reconcileTerminalPending(against: blocks)
             reproject()
+        case .streamingProse(let message):
+            // The preview is a whole-value replace; an agent session only. A
+            // terminal session has no agent prose, so ignore it there.
+            guard descriptor.kind != .terminal else { break }
+            let next = message.flatMap { Self.isProse($0) ? $0 : nil }
+            guard next != streamingMessage else { break }
+            streamingMessage = next
+            reproject()
         case .reset:
             // The transcript was truncated/replaced on the Mac (tailer
             // re-read from scratch). The window's seq space is void; clear
@@ -507,6 +530,8 @@ public final class ChatConversationStore {
             // their retry and in-flight sends may still land in the new
             // transcript and reconcile normally.
             messages = []
+            // The preview belongs to the old seq space; drop it on re-anchor.
+            streamingMessage = nil
             // Terminal blocks must clear here too: the terminal reproject()
             // does not consult `messages`, so without this the synchronous
             // reproject below would re-render stale blocks (and they'd persist
@@ -713,10 +738,27 @@ public final class ChatConversationStore {
                 + pending.map(ChatTranscriptRow.pendingOutbound)
             return
         }
+        // The live preview renders as a trailing agent bubble after the
+        // committed window. Appending it to the projector input lets it group
+        // with adjacent agent prose exactly like a real message; it carries no
+        // window identity (never paged, deduped, or reconciled by id).
+        let projected: [ChatMessage]
+        if let streamingMessage, !messages.contains(where: { $0.id == streamingMessage.id }) {
+            projected = messages + [streamingMessage]
+        } else {
+            projected = messages
+        }
         rows = projector.rows(
-            messages: messages,
+            messages: projected,
             pending: pending,
             firstUnreadSeq: firstUnreadSeq
         )
     }
+
+    /// Whether a message is renderable agent/user prose (used to settle the
+    /// live preview against the authoritative transcript line).
+    private static func isProse(_ message: ChatMessage) -> Bool {
+        if case .prose = message.kind { return true }
+        return false
+    }
 }

Packages/Shared/CmuxAgentChat/Sources/CmuxAgentChat/Store/ChatSessionListReducer.swift

@@ -67,7 +67,7 @@ public struct ChatSessionListReducer: Sendable {
             // conversation's `ChatConversationStore` still consumes `stateChanged`
             // directly for its own live state (it is not version-reconciled).
             return sessions
-        case .appended, .updated, .terminalBlocks, .reset, .unknown:
+        case .appended, .updated, .terminalBlocks, .streamingProse, .reset, .unknown:
             // Transcript-content frames don't affect the session list.
             return sessions
         }

Packages/Shared/CmuxAgentChat/Sources/CmuxAgentChat/Wire/ChatSessionEvent.swift

@@ -17,6 +17,14 @@ public enum ChatSessionEvent: Sendable, Equatable {
     /// reconnect is idempotent.
     case terminalBlocks([TerminalCommandBlock])
 
+    /// A live, not-yet-committed preview of the agent's in-progress prose for
+    /// the current turn, scraped from the terminal's rendered screen while the
+    /// authoritative JSONL line has not been written yet. The payload replaces
+    /// any prior preview wholesale; `nil` clears it. It lives outside the
+    /// message window and is superseded the instant the authoritative agent
+    /// prose lands via ``appended``, so it never duplicates a real message.
+    case streamingProse(ChatMessage?)
+
     /// The producing transcript was truncated or replaced; the session's
     /// seq space restarted and clients must re-anchor from history.
     case reset
@@ -30,6 +38,7 @@ extension ChatSessionEvent: Codable {
     private enum CodingKeys: String, CodingKey {
         case event
         case messages
+        case message
         case state
         case descriptor
         case blocks
@@ -41,6 +50,7 @@ extension ChatSessionEvent: Codable {
         case stateChanged = "state_changed"
         case descriptorChanged = "descriptor_changed"
         case terminalBlocks = "terminal_blocks"
+        case streamingProse = "streaming_prose"
         case reset
     }
 
@@ -58,6 +68,8 @@ extension ChatSessionEvent: Codable {
             self = .descriptorChanged(try container.decode(ChatSessionDescriptor.self, forKey: .descriptor))
         case .terminalBlocks:
             self = .terminalBlocks(try container.decode([TerminalCommandBlock].self, forKey: .blocks))
+        case .streamingProse:
+            self = .streamingProse(try container.decodeIfPresent(ChatMessage.self, forKey: .message))
         case .reset:
             self = .reset
         case .none:
@@ -86,6 +98,9 @@ extension ChatSessionEvent: Codable {
         case .terminalBlocks(let blocks):
             try container.encode(EventName.terminalBlocks.rawValue, forKey: .event)
             try container.encode(blocks, forKey: .blocks)
+        case .streamingProse(let message):
+            try container.encode(EventName.streamingProse.rawValue, forKey: .event)
+            try container.encodeIfPresent(message, forKey: .message)
         case .reset:
             try container.encode(EventName.reset.rawValue, forKey: .event)
         case .unknown(let raw):