[codex] Always enable agent prose streaming

Sources/Mobile/AgentChat/AgentChatProseStreamer.swift

@@ -12,9 +12,9 @@ import Foundation
 /// instant the authoritative JSONL line lands (``authoritativeProseArrived``) or
 /// the turn ends (``turnEnded``), so it never duplicates a committed message.
 ///
-/// Gating keeps it off the keystroke hot path: a surface is only snapshotted
-/// while the feature flag is on, a chat client is subscribed, and a turn is
-/// actively streaming for that session. Idle sessions are never polled.
+/// It stays off the keystroke hot path: a surface is only snapshotted while a
+/// chat client is subscribed and a turn is actively streaming for that session.
+/// Idle sessions are never polled.
 @MainActor
 final class AgentChatProseStreamer {
     /// Per-session live-turn bookkeeping.
@@ -34,7 +34,6 @@ final class AgentChatProseStreamer {
 
     private let emit: @MainActor (ChatSessionEventFrame) -> Void
     private let snapshot: @MainActor (UUID) -> [String]?
-    private let isEnabled: @MainActor () -> Bool
     private let hasSubscribers: @MainActor () -> Bool
     private let now: @MainActor () -> Date
     private let pollInterval: Duration
@@ -46,23 +45,20 @@ final class AgentChatProseStreamer {
     ///   - emit: Publishes a wire frame to subscribed chat clients.
     ///   - snapshot: Maps a surface id to its rendered screen rows (top to
     ///     bottom), or `nil` when the surface is gone.
-    ///   - isEnabled: The live feature-flag read (default-off).
     ///   - hasSubscribers: Whether any chat client is currently listening.
     ///   - now: Clock seam for the preview message timestamp.
     ///   - pollInterval: Snapshot cadence while a turn streams.
     ///   - sleep: Cancellable sleep seam for the poll loop.
     init(
         emit: @escaping @MainActor (ChatSessionEventFrame) -> Void,
         snapshot: @escaping @MainActor (UUID) -> [String]?,
-        isEnabled: @escaping @MainActor () -> Bool = { AgentChatProseStreamingFlag.isEnabled },
         hasSubscribers: @escaping @MainActor () -> Bool,
         now: @escaping @MainActor () -> Date = { Date() },
         pollInterval: Duration = .milliseconds(150),
         sleep: @escaping @Sendable (Duration) async -> Void = { try? await Task.sleep(for: $0) }
     ) {
         self.emit = emit
         self.snapshot = snapshot
-        self.isEnabled = isEnabled
         self.hasSubscribers = hasSubscribers
         self.now = now
         self.pollInterval = pollInterval
@@ -118,7 +114,7 @@ final class AgentChatProseStreamer {
 
     private func emitPreviewIfChanged(sessionID: String) {
         guard let turn = turns[sessionID], !turn.settled else { return }
-        guard isEnabled(), hasSubscribers() else { return }
+        guard hasSubscribers() else { return }
         guard let lines = snapshot(turn.surfaceID) else { return }
         guard let prose = extractor.extract(lines: lines, agentKind: turn.agentKind) else { return }
         guard prose != turn.lastEmitted else { return }

Sources/Mobile/AgentChat/AgentChatTranscriptService.swift

@@ -15,7 +15,7 @@ final class AgentChatTranscriptService {
     let resolver: AgentChatTranscriptResolver
     private let coding = ChatWireCoding()
     private var tailers: [String: AgentChatTranscriptTailer] = [:]
-    /// Drives the live agent-prose streaming preview (default-off feature flag).
+    /// Drives the live agent-prose streaming preview.
     private var proseStreamer: AgentChatProseStreamer!
     /// Sessions whose transcript could not be resolved; skipped until an
     /// explicit history request retries, so per-hook-event resolution
@@ -155,12 +155,10 @@ final class AgentChatTranscriptService {
             ensureTailer(for: record)
         }
         // Drive the live prose-streaming preview off the turn lifecycle: a
-        // prompt starts the in-flight turn, Stop ends it. Gated by the
-        // default-off flag here so a turn loop is never spawned otherwise.
+        // prompt starts the in-flight turn, Stop ends it.
         switch event.hookEventName {
         case .userPromptSubmit:
-            if AgentChatProseStreamingFlag.isEnabled,
-               record.state != .ended,
+            if record.state != .ended,
                let surfaceID = record.surfaceID.flatMap(UUID.init(uuidString:)) {
                 proseStreamer.turnStarted(
                     sessionID: record.sessionID,

cmux.xcodeproj/project.pbxproj

@@ -11,7 +11,7 @@
 		A9E020000000000000000007 /* agent-session-solid in Resources */ = {isa = PBXBuildFile; fileRef = A9E010000000000000000007 /* agent-session-solid */; };
 		ACA7C4A70000000000000003 /* AgentChatHookSessionStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = ACA7C4A70000000000000004 /* AgentChatHookSessionStore.swift */; };
 		CDFE000000000000000000A1 /* AgentChatProseStreamer.swift in Sources */ = {isa = PBXBuildFile; fileRef = CDFE000000000000000000A2 /* AgentChatProseStreamer.swift */; };
-		CDFE000000000000000000B1 /* AgentChatProseStreamingFlag.swift in Sources */ = {isa = PBXBuildFile; fileRef = CDFE000000000000000000B2 /* AgentChatProseStreamingFlag.swift */; };
+		CDFE000000000000000000C1 /* AgentChatProseStreamerTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = CDFE000000000000000000C2 /* AgentChatProseStreamerTests.swift */; };
 		ACA7C4A70000000000000001 /* AgentChatSessionRecord.swift in Sources */ = {isa = PBXBuildFile; fileRef = ACA7C4A70000000000000002 /* AgentChatSessionRecord.swift */; };
 		ACA7C4A70000000000000007 /* AgentChatSessionRegistry.swift in Sources */ = {isa = PBXBuildFile; fileRef = ACA7C4A70000000000000008 /* AgentChatSessionRegistry.swift */; };
 		ACA7C4A70000000000000005 /* AgentChatTranscriptResolver.swift in Sources */ = {isa = PBXBuildFile; fileRef = ACA7C4A70000000000000006 /* AgentChatTranscriptResolver.swift */; };
@@ -1277,7 +1277,7 @@
 		A9E010000000000000000007 /* agent-session-solid */ = {isa = PBXFileReference; lastKnownFileType = folder; path = "agent-session-solid"; sourceTree = "<group>"; };
 		ACA7C4A70000000000000004 /* AgentChatHookSessionStore.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = "AgentChatHookSessionStore.swift"; sourceTree = "<group>"; };
 		CDFE000000000000000000A2 /* AgentChatProseStreamer.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = "AgentChatProseStreamer.swift"; sourceTree = "<group>"; };
-		CDFE000000000000000000B2 /* AgentChatProseStreamingFlag.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = "AgentChatProseStreamingFlag.swift"; sourceTree = "<group>"; };
+		CDFE000000000000000000C2 /* AgentChatProseStreamerTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AgentChatProseStreamerTests.swift; sourceTree = "<group>"; };
 		ACA7C4A70000000000000002 /* AgentChatSessionRecord.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = "AgentChatSessionRecord.swift"; sourceTree = "<group>"; };
 		ACA7C4A70000000000000008 /* AgentChatSessionRegistry.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = "AgentChatSessionRegistry.swift"; sourceTree = "<group>"; };
 		ACA7C4A70000000000000006 /* AgentChatTranscriptResolver.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = "AgentChatTranscriptResolver.swift"; sourceTree = "<group>"; };
@@ -2590,7 +2590,6 @@
 				ACA7C4A7000000000000000A /* AgentChatTranscriptTailer.swift */,
 				ACA7C4A7000000000000000C /* AgentChatTranscriptService.swift */,
 				CDFE000000000000000000A2 /* AgentChatProseStreamer.swift */,
-				CDFE000000000000000000B2 /* AgentChatProseStreamingFlag.swift */,
 			);
 			name = AgentChat;
 			path = AgentChat;
@@ -3445,6 +3444,7 @@
 					F6572003A1B2C3D4E5F60718 /* SessionPersistenceResumeBindingTests.swift */,
 					F5000001A1B2C3D4E5F60718 /* SessionPersistenceTests.swift */,
 				B35750000000000000000009 /* PiVaultAgentPersistenceTests.swift */,
+				CDFE000000000000000000C2 /* AgentChatProseStreamerTests.swift */,
 				D3610B010000000000000002 /* AgentSessionAutoResumeSettingsTests.swift */,
 				D3610B020000000000000002 /* AgentSessionAutoResumeSwiftTests.swift */,
 				A9E010000000000000000005 /* AgentExecutableResolverTests.swift */,
@@ -4149,7 +4149,6 @@
 
 				ACA7C4A70000000000000003 /* AgentChatHookSessionStore.swift in Sources */,
 				CDFE000000000000000000A1 /* AgentChatProseStreamer.swift in Sources */,
-				CDFE000000000000000000B1 /* AgentChatProseStreamingFlag.swift in Sources */,
 				ACA7C4A70000000000000001 /* AgentChatSessionRecord.swift in Sources */,
 				ACA7C4A70000000000000007 /* AgentChatSessionRegistry.swift in Sources */,
 				ACA7C4A70000000000000005 /* AgentChatTranscriptResolver.swift in Sources */,
@@ -4978,6 +4977,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				CDFE000000000000000000C1 /* AgentChatProseStreamerTests.swift in Sources */,
 				A9E020000000000000000005 /* AgentExecutableResolverTests.swift in Sources */,
 				D36A00020000000000000001 /* AgentHibernationTests.swift in Sources */,
 				D3610B010000000000000001 /* AgentSessionAutoResumeSettingsTests.swift in Sources */,

cmuxTests/AgentChatProseStreamerTests.swift

@@ -0,0 +1,88 @@
+import CmuxAgentChat
+import Foundation
+import XCTest
+
+#if canImport(cmux_DEV)
+@testable import cmux_DEV
+#elseif canImport(cmux)
+@testable import cmux
+#endif
+
+@MainActor
+final class AgentChatProseStreamerTests: XCTestCase {
+    private actor SleepGate {
+        private var continuation: CheckedContinuation<Void, Never>?
+
+        func wait() async {
+            await withCheckedContinuation { continuation in
+                self.continuation = continuation
+            }
+        }
+
+        func resume() {
+            continuation?.resume()
+            continuation = nil
+        }
+    }
+
+    func testStreamsWhenLegacyUserDefaultsFlagIsFalse() async throws {
+        let legacyDefaultsKey = "CMUXAgentChatProseStreaming"
+        let previousLegacyValue = UserDefaults.standard.object(forKey: legacyDefaultsKey)
+        UserDefaults.standard.set(false, forKey: legacyDefaultsKey)
+        defer {
+            if let previousLegacyValue {
+                UserDefaults.standard.set(previousLegacyValue, forKey: legacyDefaultsKey)
+            } else {
+                UserDefaults.standard.removeObject(forKey: legacyDefaultsKey)
+            }
+        }
+
+        let surfaceID = UUID()
+        let sessionID = "session-with-always-on-streaming"
+        let expectedText = "The sky is blue."
+        let screenRows = [
+            "> Reply with one short sentence about blue.",
+            "",
+            expectedText,
+            "",
+            "Working (3s Esc to interrupt)",
+            "> ",
+        ]
+
+        let emittedFrame = expectation(description: "streaming prose frame emitted")
+        let sleepGate = SleepGate()
+        var emittedFrames: [ChatSessionEventFrame] = []
+        let streamer = AgentChatProseStreamer(
+            emit: { frame in
+                if emittedFrames.isEmpty {
+                    emittedFrame.fulfill()
+                }
+                emittedFrames.append(frame)
+            },
+            snapshot: { requestedSurfaceID in
+                requestedSurfaceID == surfaceID ? screenRows : nil
+            },
+            hasSubscribers: { true },
+            now: { Date(timeIntervalSince1970: 1_711_111_111) },
+            pollInterval: .seconds(60),
+            sleep: { _ in await sleepGate.wait() }
+        )
+
+        streamer.turnStarted(sessionID: sessionID, surfaceID: surfaceID, agentKind: .codex)
+        await fulfillment(of: [emittedFrame], timeout: 1.0)
+        streamer.turnEnded(sessionID: sessionID)
+        await sleepGate.resume()
+
+        let frame = try XCTUnwrap(emittedFrames.first)
+        XCTAssertEqual(frame.sessionID, sessionID)
+        guard case .streamingProse(let message?) = frame.event else {
+            return XCTFail("Expected a streaming prose preview frame")
+        }
+        XCTAssertEqual(message.id, "stream:\(sessionID)")
+        XCTAssertEqual(message.role, .agent)
+        guard case .prose(let prose) = message.kind else {
+            return XCTFail("Expected prose preview content")
+        }
+        XCTAssertEqual(prose.text, expectedText)
+    }
+}