[EXP] Host interactive Claude agents over stream-json behind KCAP_CLAUDE_TRANSPORT

README.md

@@ -2007,6 +2007,18 @@ KCAP_CODEX_TRANSPORT=app-server kcap daemon   # opt in; default is `pty`
 - **`app-server`** takes effect only for review-flow (unattended) launches and only when the installed Codex meets the minimum version (**0.146.0**); a lower build falls back to `pty` automatically. Interactive launches always use `pty` in this release.
 - Rollback is a restart with the value flipped back to `pty`; it governs new launches only.
 
+##### Claude transport (`KCAP_CLAUDE_TRANSPORT`)
+
+Interactive hosted Claude agents can run as `claude -p` over Claude Code's stream-json protocol instead of the interactive PTY. The prompt is then sent as the session's first message, never on the command line, so the chat shows what you typed whatever its length. It is opt-in and env-only:
+
+```bash
+KCAP_CLAUDE_TRANSPORT=stream-json kcap daemon   # opt in; default is `pty`
+```
+
+- **Default `pty`** — the interactive-terminal path, unchanged.
+- **`stream-json`** applies to interactive launches in a daemon-owned worktree. Reviews, review flows and private agents stay on `pty`. A stream-json agent has no terminal view; permission prompts and questions arrive as cards as usual.
+- Rollback is a restart with the value flipped back to `pty`; it governs new launches only.
+
 The Cursor CLI path (`cursor-agent` by default, used to spawn the `cursor` hosted-agent vendor) is env-only for now — there is no `daemon.cursor_path` profile key yet, so set it per-launch:
 
 ```bash

src/Capacitor.App/App.axaml.cs

@@ -1584,7 +1584,7 @@ internal static MainWindow BuildAndShowMainWindow(
             service, appState,
             launch, new RepoPathStore(config, time).GetSortedPathsAsync, time, shutdownToken,
             navigationGeneration: () => vm?.NavigationGeneration ?? 0,
-            openSessionIfCurrent: (agentId, generation) => vm?.OpenSessionIfCurrent(agentId, generation),
+            openSessionIfCurrent: (agentId, generation, launchPrompt) => vm?.OpenSessionIfCurrent(agentId, generation, launchPrompt),
             requestSignIn: requestSignIn,
             daemons: remoteAgents?.Daemons, viewerId: viewerId, laneStatus: lane?.Status,
             localMachineId: localMachineId, launchFailures: lane?.LaunchFailures, directory: resolvedDirectory,

src/Capacitor.App/ViewModels/ChatTabViewModel.cs

@@ -51,6 +51,9 @@ public sealed class ChatTabViewModel : ReactiveObject, IAttachmentSink {
     // token it can ask without an ObjectDisposedException.
     readonly CancellationToken _lifetimeToken;
     readonly AvaloniaList<ChatItemViewModel> _items = new();
+    /// Stands in for the launch prompt until the transcript's own rows land. Never a queued send:
+    /// the transcript's first read is history, which cannot acknowledge one.
+    UserTurnItem? _launchTurn;
     readonly AvaloniaList<QueuedChatMessage> _queuedMessages = new();
     // Keep retired sends eligible for late echoes without letting them consume a later send's receipt.
     readonly List<(QueuedChatMessage Old, QueuedChatMessage Replacement)> _superseded = new();
@@ -1020,10 +1023,18 @@ async Task ChooseTerminalMenuAsync(byte[] keys) {
         SetTerminalMenuChoiceTaken(false);
     }
 
+    public void ShowLaunchPrompt(string text) {
+        if (_launchTurn is not null || _items.Count > 0) return;
+        _launchTurn = new UserTurnItem(text);
+        _items.Add(_launchTurn);
+        this.RaisePropertyChanged(nameof(PhaseNote));
+    }
+
     void SwitchFeed(string key, Func<string, IChatTranscriptFeed> open) {
         // A released tab's runs belong to the monitor that took its feed; this tab reads nothing more.
         if (_feedReleased) return;
         _items.Clear();
+        if (_launchTurn is not null) _items.Add(_launchTurn);
         _history.Clear();
         _literalInputHistory.Clear();
         _unechoed.Clear();
@@ -1339,6 +1350,7 @@ bool Prepare(int generation, FeedRead read) {
                 // names where that history ends — anything past it arrived after and can acknowledge.
                 RebaseQueuedMessages(read.SnapshotOffset ?? CurrentOffset ?? 0);
                 _items.Clear();
+                if (_launchTurn is not null) _items.Add(_launchTurn);
                 _history.ClearForReplay();
                 _pendingTools.Clear();
                 _settledTools.Clear();
@@ -1485,7 +1497,11 @@ void Finish(FeedRead read, LineCursor? cursor) {
             foreach (var projected in cursor.Restored)
                 foreach (var text in projected.SubmittedInputs)
                     _history.Observe(AttachmentTrailer.Strip(text));
-            if (cursor.Fresh.Count > 0) _items.AddRange(cursor.Fresh);
+            if (cursor.Fresh.Count > 0) {
+                if (_launchTurn is not null) _items.Remove(_launchTurn);
+                _launchTurn = null;
+                _items.AddRange(cursor.Fresh);
+            }
         }
         Phase = ChatTabPhase.Reading;
         ApplyFeedRuns(read);

src/Capacitor.App/ViewModels/HomeViewModel.cs

@@ -114,7 +114,7 @@ internal static string NoHarnessesNotice(string? remoteMachine) => remoteMachine
     readonly ILaunchClient _launch;
     readonly Func<Task<string[]>> _knownRepos;
     readonly Func<int>? _navigationGeneration;
-    readonly Action<string, int>? _openSessionIfCurrent;
+    readonly Action<string, int, string?>? _openSessionIfCurrent;
     readonly Action<string>? _launchFailed;
     readonly CompositeDisposable _disposables = new();
 
@@ -470,7 +470,7 @@ public HomeViewModel(
             IDaemonClientService daemon, IAppStateStore state, ILaunchClient launch,
             Func<Task<string[]>> knownRepos, TimeProvider time, CancellationToken shutdown = default,
             Func<int>? navigationGeneration = null,
-            Action<string, int>? openSessionIfCurrent = null, Action? requestSignIn = null,
+            Action<string, int, string?>? openSessionIfCurrent = null, Action? requestSignIn = null,
             IObservable<IReadOnlyList<DaemonInfo>>? daemons = null,
             Func<CancellationToken, Task<string?>>? viewerId = null,
             IObservable<ServerLaneStatus>? laneStatus = null, string? localMachineId = null,
@@ -1372,7 +1372,7 @@ async Task StartAsync() {
         // Untracked with no row is a failure that beat the call's own return: opening would cover
         // the launcher that has just worded it.
         if (!draft.Remote && (tracked || RowExists(agentId, AgentOrigin.Local)))
-            _openSessionIfCurrent?.Invoke(agentId, generation);
+            _openSessionIfCurrent?.Invoke(agentId, generation, draft.Goal);
     }
 
     async Task<bool> OwnsConnectedAsync(string machine) =>

src/Capacitor.App/ViewModels/MainWindowViewModel.cs

@@ -672,9 +672,10 @@ open is RemoteSessionViewModel remote
     /// arriving after any navigation (closing the workspace, another session, close-to-hide, the
     /// shutdown latch) opens nothing, rather than attaching an invisible terminal or replacing what
     /// the user opened while the launch was in flight.
-    public void OpenSessionIfCurrent(string agentId, int generation) {
+    public void OpenSessionIfCurrent(string agentId, int generation, string? launchPrompt = null) {
         if (generation != _navigation.Generation) return;
-        OpenSession(agentId);
+        if (OpenSession(agentId) && launchPrompt is { Length: > 0 } && CurrentWorkspace is WorkspaceViewModel workspace)
+            workspace.ShowLaunchPrompt(launchPrompt);
     }
 
     /// The launcher words a launch failure, and an open workspace covers the launcher. Only a

src/Capacitor.App/ViewModels/WorkspaceViewModel.cs

@@ -56,6 +56,13 @@ public sealed class WorkspaceViewModel : ReactiveObject, ISessionWorkspace {
 
     public IObservable<Unit> Ended { get; }
 
+    string? _launchPrompt;
+
+    public void ShowLaunchPrompt(string prompt) {
+        if (Chat is { } chat) chat.ShowLaunchPrompt(prompt);
+        else _launchPrompt = prompt;
+    }
+
     ChatTabViewModel? _chat;
     /// Built once, on the first dto; the reader comes from transcript_format and the input channel
     /// from has_terminal.
@@ -331,6 +338,7 @@ public WorkspaceViewModel(
                 };
                 if (PullRequests is { } fixHost)
                     Chat.WhenAnyValue(chat => chat.ShowsComposer).Subscribe(_ => fixHost.FixAvailabilityChanged()).DisposeWith(_disposables);
+                if (_launchPrompt is { } launchPrompt) Chat.ShowLaunchPrompt(launchPrompt);
             })
             .DisposeWith(_disposables);
 

src/Capacitor.Cli.Daemon/DaemonConfig.cs

@@ -216,6 +216,10 @@ public BinaryProbe Binaries {
     public string ClaudePath { get; set; } = Core.Harness.Claude.ClaudeHarness.CliBinary;
     public string CodexPath  { get; set; } = Core.Harness.Codex.CodexHarness.CliBinary;
 
+    /// <summary>Transport for interactive hosted Claude agents, from <c>KCAP_CLAUDE_TRANSPORT</c>:
+    /// <c>pty</c> (default) or <c>stream-json</c>. Any other value is <c>pty</c>.</summary>
+    public string ClaudeTransport { get; set; } = Harness.Claude.ClaudeHostedAgentRuntimeFactory.Pty;
+
     /// <summary>Transport for hosted Codex reviewers: <c>pty</c> (default) or <c>app-server</c>.
     /// Set via <c>KCAP_CODEX_TRANSPORT</c>. Governs NEW review-flow launches only; interactive
     /// launches always take the PTY path in this phase. The effective decision (this selection AND

src/Capacitor.Cli.Daemon/DaemonRunner.cs

@@ -209,6 +209,9 @@ public static async Task<int> RunAsync(string[] args) {
 
         Harness.Codex.CodexTransportDecision.BindFromEnvironment(config, Environment.GetEnvironmentVariable);
 
+        if (Environment.GetEnvironmentVariable("KCAP_CLAUDE_TRANSPORT") is { Length: > 0 } claudeTransport)
+            config.ClaudeTransport = claudeTransport.Trim();
+
         // One resolved fact for both the launch router and the certification advertisement.
         config.CodexAppServerActive = Harness.Codex.CodexTransportDecision.ResolveActive(
             config.CodexTransport, () => ProbeCliVersion(config.CodexPath));
@@ -457,15 +460,22 @@ await Console.Error.WriteLineAsync(
         // Prepare/BuildArgs/Spawn inline. PtyHostedAgentRuntimeFactory wraps each registered PTY
         // launcher (Claude, Codex); AcpHostedAgentRuntimeFactory speaks ACP JSON-RPC over stdio for
         // Cursor (no IHostedAgentLauncher — Cursor never went through the PTY launcher contract).
-        builder.Services.AddSingleton<IHostedAgentRuntimeFactory>(sp =>
-            new PtyHostedAgentRuntimeFactory(
-                sp.GetServices<IHostedAgentLauncher>().SingleOrDefault(l => l.Vendor == "claude")
-                    ?? throw new InvalidOperationException("No IHostedAgentLauncher registered for vendor 'claude'"),
+        builder.Services.AddSingleton<IHostedAgentRuntimeFactory>(sp => {
+            var claudeLauncher = sp.GetServices<IHostedAgentLauncher>().SingleOrDefault(l => l.Vendor == "claude")
+                ?? throw new InvalidOperationException("No IHostedAgentLauncher registered for vendor 'claude'");
+            var pty = new PtyHostedAgentRuntimeFactory(
+                claudeLauncher,
                 sp.GetRequiredService<IPtyProcessFactory>(),
                 sp.GetRequiredService<ILogger<PtyHostedAgentRuntimeFactory>>(),
-                sp.GetRequiredService<TimeProvider>()
-            )
-        );
+                sp.GetRequiredService<TimeProvider>());
+            return new Harness.Claude.ClaudeHostedAgentRuntimeFactory(
+                claudeLauncher, pty,
+                sp.GetRequiredService<DaemonConfig>(),
+                sp.GetRequiredService<LocalPermissionBridge>(),
+                harnesses.Of<Core.Harness.Claude.ClaudeHarness>().Paths,
+                sp.GetRequiredService<ILoggerFactory>(),
+                time);
+        });
         // Codex is the ONE vendor with two transports. The composite factory routes review-flow
         // launches to codex app-server when this daemon resolved it active (config.CodexAppServerActive),
         // and delegates everything else — every interactive launch, and all launches under the PTY