feat(maestro): route maestro send through ACP for structured sessions

Structured sessions were rejected by `send_input` with NotTerminal.
Now `run_send` checks the session view and routes to
`send_structured_prompt` for structured sessions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/maestro-cli/src/cli.rs

@@ -41,8 +41,8 @@ pub enum Command {
     Attach(AttachArgs),
     /// Kill a session by ID.
     Kill(KillArgs),
-    /// Type text into a running session, as if it had been typed on an
-    /// attached terminal.
+    /// Send text to a running session. Terminal sessions receive raw
+    /// keystrokes; structured sessions receive an ACP prompt.
     Send(SendArgs),
     /// Install or update the agent activity hook (#106).
     Hooks(HooksArgs),

crates/maestro-cli/src/sessions.rs

@@ -130,9 +130,12 @@ pub fn resolve_session(sessions: &[Session], needle: &str) -> Result<uuid::Uuid,
 /// `maestro send`. Answers with the session that was typed into, so the
 /// caller can name it once the daemon has accepted the text.
 ///
-/// A bare ID skips the catalog fetch; anything else needs the list to match
-/// against. Text comes from the arguments, or from stdin when there is none —
-/// the shape a heredoc or a pipe wants.
+/// Terminal sessions get raw keystrokes via `send_input`; structured sessions
+/// get an ACP prompt via `send_structured_prompt` (`--no-enter` is ignored
+/// there — ACP prompts are always complete messages).
+///
+/// Text comes from the arguments, or from stdin when there is none — the
+/// shape a heredoc or a pipe wants.
 #[allow(clippy::result_large_err)]
 pub async fn run_send(
     client: &DaemonClient,
@@ -155,19 +158,28 @@ pub async fn run_send(
         return Err(CliError::NothingToSend);
     }
 
-    let id = match uuid::Uuid::parse_str(args.session.trim()) {
-        Ok(id) => id,
-        Err(_) => {
-            let sessions = client.list_sessions().await?;
-            resolve_session(&sessions, &args.session)?
-        }
-    };
+    // We always need the session list: even a bare UUID needs the view field
+    // to decide which endpoint to hit.
+    let sessions = client.list_sessions().await?;
+    let id = resolve_session(&sessions, &args.session)?;
+    let view = sessions
+        .iter()
+        .find(|s| s.id == id)
+        .map(|s| s.view)
+        .unwrap_or(SessionView::Terminal);
 
-    let req = SendInputRequest {
-        text,
-        submit: !args.no_enter,
-    };
-    client.send_input(id, &req).await?;
+    match view {
+        SessionView::Structured => {
+            client.send_structured_prompt(id, &text).await?;
+        }
+        SessionView::Terminal => {
+            let req = SendInputRequest {
+                text,
+                submit: !args.no_enter,
+            };
+            client.send_input(id, &req).await?;
+        }
+    }
     Ok(id)
 }
 
@@ -216,6 +228,7 @@ fn print_session_table(out: &mut impl Write, sessions: &[Session], info: &Daemon
             ActivityState::Idle => "idle",
             ActivityState::AwaitingInput => "awaiting",
             ActivityState::Error => "error",
+            ActivityState::Starting => "starting",
         };
         // Show the live foreground command alongside the spawn command when
         // the daemon has observed one that differs (NAP-340).

crates/maestro-cli/tests/against_mock_daemon.rs

@@ -2,7 +2,7 @@
 //! was unit-tested, but nothing exercised the client, the error decoding, or
 //! the unreachable-daemon path without compiling and forking a real daemon.
 
-use maestro_protocol::{DaemonClient, DaemonInfo};
+use maestro_protocol::{DaemonClient, DaemonInfo, SessionView};
 use maestro_testing::{session, MockDaemon};
 use uuid::Uuid;
 
@@ -202,6 +202,35 @@ async fn send_resolves_a_session_by_name() {
     assert_eq!(sent, id);
 }
 
+/// A structured session routes through the ACP prompt endpoint, not the
+/// terminal input one — `--no-enter` is irrelevant (ACP prompts are
+/// complete messages).
+#[tokio::test]
+async fn send_to_structured_session_uses_acp_prompt() {
+    let mock = MockDaemon::start().await;
+    let id = Uuid::from_u128(13);
+    let mut s = session(id, "/tmp", "claude");
+    s.view = SessionView::Structured;
+    mock.add_session(s);
+
+    let args = maestro_cli::cli::SendArgs {
+        session: id.to_string(),
+        text: vec!["fix".into(), "the".into(), "tests".into()],
+        no_enter: false,
+    };
+    let sent = maestro_cli::sessions::run_send(&mock.client(), &args, &mut std::io::empty())
+        .await
+        .expect("send");
+
+    assert_eq!(sent, id);
+    // Terminal input must stay empty — the message went through ACP.
+    assert!(mock.inputs().is_empty());
+    let prompts = mock.structured_prompts();
+    assert_eq!(prompts.len(), 1);
+    assert_eq!(prompts[0].0, id);
+    assert_eq!(prompts[0].1.prompt, "fix the tests");
+}
+
 #[tokio::test]
 async fn send_to_an_unknown_session_fails_without_typing_anything() {
     let mock = MockDaemon::start().await;

crates/maestro-daemon/src/local_api.rs

@@ -180,7 +180,7 @@ fn dir_error_status(code: &str) -> StatusCode {
 fn session_error_status(code: &str) -> StatusCode {
     match code {
         "not_found" => StatusCode::NOT_FOUND,
-        "invalid_env" => StatusCode::BAD_REQUEST,
+        "invalid_env" | "bad_request" => StatusCode::BAD_REQUEST,
         // A guard refusal is the daemon doing its job, not a failure (#79).
         "kill_guarded" => StatusCode::CONFLICT,
         // The session outlived its pane: nothing to type into, and nothing
@@ -483,7 +483,9 @@ async fn structured_prompt(
     Json(body): Json<StructuredPromptRequest>,
 ) -> Response {
     match s.manager.queue_acp_prompt(id, body.prompt).await {
-        Ok(QueueAcpPrompt::Queued) => StatusCode::NO_CONTENT.into_response(),
+        Ok(QueueAcpPrompt::Queued) | Ok(QueueAcpPrompt::Pending) => {
+            StatusCode::NO_CONTENT.into_response()
+        }
         Ok(QueueAcpPrompt::InFlight) => error_response(
             StatusCode::CONFLICT,
             "turn_in_flight",

crates/maestro-daemon/src/session.rs

@@ -6,12 +6,9 @@
 //! handler interact with tmux.
 
 use std::collections::{HashMap, HashSet};
-use std::future::Future;
 use std::path::PathBuf;
-use std::pin::Pin;
 use std::sync::atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering};
 use std::sync::{Arc, Weak};
-use std::task::{Context, Poll};
 use std::time::Duration;
 
 use chrono::Utc;
@@ -125,6 +122,9 @@ pub struct SessionRecord {
     /// When `true`, the permission pump auto-responds `AllowAlways` to every
     /// ACP permission request without surfacing it to clients.
     pub auto_approve: bool,
+    /// A prompt submitted while the adapter was still booting (`Starting`).
+    /// The background handshake task drains this on success.
+    pub pending_prompt: Option<String>,
 }
 
 impl SessionRecord {
@@ -134,6 +134,13 @@ impl SessionRecord {
             && self.acp.is_some()
             && self.acp_events.is_some()
     }
+
+    /// The session is structured and still booting its adapter.
+    fn is_starting_structured(&self) -> bool {
+        self.session.view == SessionView::Structured
+            && self.session.activity == ActivityState::Starting
+            && self.acp.is_none()
+    }
 }
 
 #[derive(Debug)]
@@ -208,6 +215,8 @@ pub enum SessionError {
     NotTerminal(Uuid),
     #[error("daemon is shutting down")]
     ShuttingDown,
+    #[error("bad request: {0}")]
+    BadRequest(String),
     /// The kill was refused (#79): the session's worktree holds unsaved work.
     /// Nothing happened — the session keeps running and the tree is untouched,
     /// so it stays the operator's handle on their own unfinished work.
@@ -227,6 +236,8 @@ pub enum BeginAcpTurn {
 #[derive(Debug)]
 pub enum QueueAcpPrompt {
     Queued,
+    /// The adapter is still booting; the prompt is held until it is ready.
+    Pending,
     InFlight,
     Unavailable,
     Failed(String),
@@ -253,6 +264,7 @@ impl SessionError {
             SessionError::NotRunning(_) => "not_running",
             SessionError::NotTerminal(_) => "not_terminal",
             SessionError::ShuttingDown => "shutting_down",
+            SessionError::BadRequest(_) => "bad_request",
             SessionError::KillGuarded(_) => "kill_guarded",
         };
         let unsaved_work = match self {
@@ -320,18 +332,6 @@ struct StructuredLifecycle {
 }
 
 impl StructuredLifecycle {
-    fn admit<'a>(
-        &'a self,
-        shutting_down: &AtomicBool,
-    ) -> Result<StructuredCreate<'a>, SessionError> {
-        let _gate = self.gate.lock().expect("structured lifecycle gate");
-        if shutting_down.load(Ordering::Acquire) {
-            return Err(SessionError::ShuttingDown);
-        }
-        self.in_flight.fetch_add(1, Ordering::AcqRel);
-        Ok(StructuredCreate { lifecycle: self })
-    }
-
     async fn wait_until_settled(&self) {
         loop {
             let settled = self.settled.notified();
@@ -343,30 +343,18 @@ impl StructuredLifecycle {
     }
 }
 
-struct StructuredCreate<'a> {
-    lifecycle: &'a StructuredLifecycle,
-}
-
-impl Drop for StructuredCreate<'_> {
-    fn drop(&mut self) {
-        if self.lifecycle.in_flight.fetch_sub(1, Ordering::AcqRel) == 1 {
-            self.lifecycle.settled.notify_one();
-        }
-    }
-}
-
-struct AdmittedStructuredCreate<'a> {
-    create: Pin<Box<dyn Future<Output = Result<Session, SessionError>> + Send + 'a>>,
-    /// Field order matters: dropping a cancelled create rolls back its inner
-    /// future before this permit releases shutdown's in-flight barrier.
-    _permit: StructuredCreate<'a>,
-}
-
-impl Future for AdmittedStructuredCreate<'_> {
-    type Output = Result<Session, SessionError>;
-
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        self.create.as_mut().poll(cx)
+/// Release the structured-lifecycle in-flight counter that `create` acquires
+/// before spawning the background ACP handshake task. Called when the task
+/// finishes (success or failure) or when `create_inner` fails before the task
+/// is spawned.
+fn drop_structured_lifecycle_permit(inner: &Inner) {
+    if inner
+        .structured_lifecycle
+        .in_flight
+        .fetch_sub(1, Ordering::AcqRel)
+        == 1
+    {
+        inner.structured_lifecycle.settled.notify_one();
     }
 }
 
@@ -660,7 +648,9 @@ impl SessionManager {
         let stream = {
             let sessions = self.inner.sessions.lock().await;
             let record = sessions.get(&id).ok_or(SessionError::NotFound(id))?;
-            if !record.is_live_structured() {
+            // Allow connecting while the adapter is still booting
+            // (`Starting`) — the event stream exists, it is just empty.
+            if !record.is_live_structured() && !record.is_starting_structured() {
                 return Ok(None);
             }
             let Some(stream) = &record.acp_events else {
@@ -745,8 +735,14 @@ impl SessionManager {
         text: String,
     ) -> Result<QueueAcpPrompt, SessionError> {
         let (acp, stream) = {
-            let sessions = self.inner.sessions.lock().await;
-            let record = sessions.get(&id).ok_or(SessionError::NotFound(id))?;
+            let mut sessions = self.inner.sessions.lock().await;
+            let record = sessions.get_mut(&id).ok_or(SessionError::NotFound(id))?;
+            // While the adapter is booting, stash the prompt for the
+            // background handshake task to drain on success.
+            if record.is_starting_structured() {
+                record.pending_prompt = Some(text);
+                return Ok(QueueAcpPrompt::Pending);
+            }
             if !record.is_live_structured() {
                 return Ok(QueueAcpPrompt::Unavailable);
             }
@@ -1217,17 +1213,42 @@ impl SessionManager {
     }
 
     /// Spawn a new session. On success returns the freshly-created `Session`.
+    ///
+    /// For structured sessions, the ACP handshake runs in a background task
+    /// after the session is registered — the HTTP caller gets an instant
+    /// response with `activity: Starting`. The `StructuredLifecycle` gate is
+    /// held across the background task so `shutdown()` waits for it.
     pub async fn create(&self, req: CreateSessionRequest) -> Result<Session, SessionError> {
         if req.view == SessionView::Structured {
-            let permit = self
+            // Acquire the lifecycle gate synchronously (rejects if shutting
+            // down). The background handshake task calls
+            // `drop_structured_lifecycle_permit` when it finishes; we must
+            // not use the RAII `StructuredCreate` because it would drop at
+            // the end of `create_inner`, before the handshake completes.
+            let _gate = self
                 .inner
                 .structured_lifecycle
-                .admit(&self.inner.shutting_down)?;
-            return AdmittedStructuredCreate {
-                create: Box::pin(self.create_inner(req)),
-                _permit: permit,
+                .gate
+                .lock()
+                .expect("structured lifecycle gate");
+            if self.inner.shutting_down.load(Ordering::Acquire) {
+                return Err(SessionError::ShuttingDown);
             }
-            .await;
+            self.inner
+                .structured_lifecycle
+                .in_flight
+                .fetch_add(1, Ordering::AcqRel);
+            drop(_gate);
+
+            return match self.create_inner(req).await {
+                Ok(session) => Ok(session),
+                Err(e) => {
+                    // create_inner failed before spawning the background
+                    // task, so release the permit here.
+                    drop_structured_lifecycle_permit(&self.inner);
+                    Err(e)
+                }
+            };
         }
         self.create_inner(req).await
     }
@@ -1289,32 +1310,39 @@ impl SessionManager {
         {
             session_env.insert("MAESTRO_URL".into(), url);
         }
-        // A structured session (#134) gets no tmux pane: the agent is a
-        // child of the daemon, driven over ACP. An adapter that cannot come
-        // up still yields a session — Dead, with the reason on it — so the
-        // operator sees what to fix instead of a silently missing session.
-        let (acp, acp_failure) = match req.view {
-            SessionView::Structured => match structured_adapter(&req.command) {
-                Err(error) => (None, Some(error)),
-                Ok(adapter) => match maestro_acp::spawn(
-                    SpawnConfig::new(
-                        &effective_cwd,
-                        session_env
-                            .iter()
-                            .map(|(k, v)| (k.clone(), v.clone()))
-                            .collect(),
-                    )
-                    .adapter(adapter),
-                )
-                .await
-                {
-                    Ok(acp) => (Some(Arc::new(acp)), None),
-                    Err(e) => {
-                        tracing::warn!(%id, error = %e, "structured session: adapter failed to start");
-                        (None, Some(e.to_string()))
+        // ── Structured path: validate adapter, open event log, register
+        // the session immediately with `Starting`, then handshake in the
+        // background so the HTTP caller gets an instant response.
+        //
+        // ── Terminal path: unchanged — tmux spawn is fast enough to stay
+        // synchronous.
+        // Structured: validate adapter, open event log eagerly. Terminal:
+        // spawn the tmux pane synchronously (it is fast).
+        let structured_spawn = match req.view {
+            SessionView::Structured => {
+                // Fail fast on an unsupported command before touching disk.
+                let adapter = structured_adapter(&req.command).map_err(SessionError::BadRequest)?;
+                // Open the event log eagerly so the structured WS can
+                // connect before the adapter is up.
+                let acp_events = match self.inner.sidecar.open_events(id) {
+                    Ok(log) => {
+                        let (tx, _) = broadcast::channel(EVENTS_CAPACITY);
+                        let (projected_tx, _) = broadcast::channel(EVENTS_CAPACITY);
+                        Arc::new(Mutex::new(AcpEventStream {
+                            log,
+                            live: tx,
+                            projection: Projection::default(),
+                            projected_live: projected_tx,
+                            pending_approvals: HashMap::new(),
+                            operation: Arc::new(Mutex::new(())),
+                            dispatch: AcpDispatchState::default(),
+                            activity_sequence: 0,
+                        }))
                     }
-                },
-            },
+                    Err(e) => return Err(SessionError::Sidecar(e)),
+                };
+                Some((adapter, acp_events))
+            }
             SessionView::Terminal => {
                 let spawned = {
                     let tmux = self.inner.tmux.clone();
@@ -1328,53 +1356,10 @@ impl SessionManager {
                 if let Err(e) = spawned {
                     return Err(SessionError::Tmux(e));
                 }
-                (None, None)
+                None
             }
         };
 
-        let acp_events = if let Some(acp) = &acp {
-            let persisted =
-                match self
-                    .inner
-                    .sidecar
-                    .read_events(id, EventCursor::Since(0), usize::MAX)
-                {
-                    Ok(events) => events,
-                    Err(error) => {
-                        acp.terminate(maestro_acp::CANCEL_GRACE, maestro_acp::TERM_GRACE)
-                            .await;
-                        return Err(SessionError::Sidecar(error));
-                    }
-                };
-            match self.inner.sidecar.open_events(id) {
-                Ok(log) => {
-                    let (tx, _) = broadcast::channel(EVENTS_CAPACITY);
-                    let (projected_tx, _) = broadcast::channel(EVENTS_CAPACITY);
-                    let mut projection = Projection::default();
-                    for event in &persisted {
-                        apply_persisted_event(&mut projection, event);
-                    }
-                    Some(Arc::new(Mutex::new(AcpEventStream {
-                        log,
-                        live: tx,
-                        projection,
-                        projected_live: projected_tx,
-                        pending_approvals: HashMap::new(),
-                        operation: Arc::new(Mutex::new(())),
-                        dispatch: AcpDispatchState::default(),
-                        activity_sequence: 0,
-                    })))
-                }
-                Err(e) => {
-                    acp.terminate(maestro_acp::CANCEL_GRACE, maestro_acp::TERM_GRACE)
-                        .await;
-                    return Err(SessionError::Sidecar(e));
-                }
-            }
-        } else {
-            None
-        };
-
         // Capture spawn-history inputs before `req` is partially moved into
         // `session`. `history_cwd` is the *chosen* working dir (the request
         // `cwd`), not a generated worktree checkout path — that's what the
@@ -1384,10 +1369,13 @@ impl SessionManager {
         resolve_name(&mut metadata);
         let worktree_branch = req.worktree.as_ref().map(|w| w.branch.clone());
 
+        let is_structured = structured_spawn.is_some();
+        let events_arc = structured_spawn.as_ref().map(|(_, e)| e.clone());
+
         let session = Session {
             id,
-            cwd: effective_cwd,
-            command: req.command,
+            cwd: effective_cwd.clone(),
+            command: req.command.clone(),
             env: req.env,
             metadata,
             worktree: worktree_path.as_ref().zip(worktree_base_repo.as_ref()).map(
@@ -1396,67 +1384,41 @@ impl SessionManager {
                     base_repo: base_repo.clone(),
                 },
             ),
-            status: if acp_failure.is_some() {
-                SessionStatus::Dead
-            } else {
-                SessionStatus::Running
-            },
+            status: SessionStatus::Running,
             created_at: Utc::now(),
-            // A terminal spawn begins active until its watcher sees otherwise;
-            // a structured spawn has no turn yet and begins idle.
             foreground: None,
-            activity: match (req.view, acp_failure.is_some()) {
-                (_, true) => ActivityState::Error,
-                (SessionView::Structured, false) => ActivityState::Idle,
-                (SessionView::Terminal, false) => ActivityState::Active,
+            activity: if is_structured {
+                ActivityState::Starting
+            } else {
+                ActivityState::Active
             },
-            activity_detail: acp_failure,
+            activity_detail: None,
             last_activity_at: Utc::now(),
             activity_since: chrono::Utc::now(),
-
             current_cwd: None,
-            // The watcher fills this in on its first blocked-work pass; a
-            // fresh tree has nothing in the way anyway.
             blocked_work: None,
             last_focused_at: None,
-            acp_session_id: acp.as_ref().map(|a| a.session_id().to_string()),
+            acp_session_id: None,
             view: req.view,
         };
 
         if let Err(e) = self.inner.sidecar.write(&session) {
-            // The process already started; end it so no ghost survives a
-            // failed sidecar write, then unwind the FIFO + worktree.
-            match &acp {
-                Some(acp) => {
-                    acp.terminate(maestro_acp::CANCEL_GRACE, maestro_acp::TERM_GRACE)
-                        .await
-                }
-                None => {
-                    let tmux = self.inner.tmux.clone();
-                    let _ = tmux_blocking(move || tmux.kill_session(id)).await;
-                }
+            if !is_structured {
+                let tmux = self.inner.tmux.clone();
+                let _ = tmux_blocking(move || tmux.kill_session(id)).await;
             }
             return Err(SessionError::Sidecar(e));
         }
 
-        let event_pump = acp
-            .as_ref()
-            .zip(acp_events.as_ref())
-            .map(|(acp, events)| (acp.clone(), events.clone()));
         {
             let mut sessions = self.inner.sessions.lock().await;
-            let event_pump = event_pump.map(|(acp, events)| {
-                let done = start_acp_event_pump(&self.inner, id, &acp, events.clone());
-                start_acp_permission_pump(&self.inner, id, &acp, events, req.auto_approve);
-                done
-            });
             sessions.insert(
                 id,
                 SessionRecord {
                     session: session.clone(),
                     fifo_path,
-                    worktree_path,
-                    worktree_base_repo,
+                    worktree_path: worktree_path.clone(),
+                    worktree_base_repo: worktree_base_repo.clone(),
                     bridge,
                     reported_activity: None,
                     settled: false,
@@ -1464,11 +1426,12 @@ impl SessionManager {
                     naming: false,
                     focused_since: None,
                     awaiting_suppressed: false,
-                    acp,
-                    acp_events,
+                    acp: None,
+                    acp_events: events_arc,
                     structured_activity_watermark: None,
-                    acp_event_pump: event_pump,
+                    acp_event_pump: None,
                     auto_approve: req.auto_approve,
+                    pending_prompt: None,
                 },
             );
         }
@@ -1497,6 +1460,78 @@ impl SessionManager {
         }
 
         pending.commit();
+
+        // ── Background ACP handshake for structured sessions ──
+        //
+        // The session is registered and visible to clients. The adapter
+        // spawn + handshake runs in a background task; on completion it
+        // fills in `acp`, starts the event/permission pumps, and
+        // transitions activity from `Starting` to `Idle` (or to `Error`
+        // on failure). The `StructuredLifecycle` permit is held until the
+        // task finishes so `shutdown()` waits for it.
+        if let Some((adapter, events)) = structured_spawn {
+            let inner = self.inner.clone();
+            let env: HashMap<String, String> = session_env
+                .iter()
+                .map(|(k, v)| (k.clone(), v.clone()))
+                .collect();
+            let cwd = effective_cwd;
+            let auto_approve = req.auto_approve;
+            tokio::spawn(async move {
+                let result = maestro_acp::spawn(SpawnConfig::new(&cwd, env).adapter(adapter)).await;
+
+                match result {
+                    Ok(acp_session) => {
+                        let acp = Arc::new(acp_session);
+                        let done = start_acp_event_pump(&inner, id, &acp, events.clone());
+                        start_acp_permission_pump(&inner, id, &acp, events.clone(), auto_approve);
+                        // Drain any prompt submitted while Starting.
+                        let pending_prompt = {
+                            let mut sessions = inner.sessions.lock().await;
+                            let Some(record) = sessions.get_mut(&id) else {
+                                // Session was killed while we were booting.
+                                acp.terminate(maestro_acp::CANCEL_GRACE, maestro_acp::TERM_GRACE)
+                                    .await;
+                                drop_structured_lifecycle_permit(&inner);
+                                return;
+                            };
+                            record.acp = Some(acp.clone());
+                            record.acp_event_pump = Some(done);
+                            record.session.acp_session_id = Some(acp.session_id().to_string());
+                            record.session.activity = ActivityState::Idle;
+                            record.session.activity_since = Utc::now();
+                            let _ = inner.sidecar.write(&record.session);
+                            let _ = inner.events.send(CatalogEvent::SessionUpdated {
+                                session: record.session.clone(),
+                            });
+                            record.pending_prompt.take()
+                        };
+                        if let Some(prompt) = pending_prompt {
+                            let manager = SessionManager {
+                                inner: inner.clone(),
+                            };
+                            let _ = manager.queue_acp_prompt(id, prompt).await;
+                        }
+                    }
+                    Err(e) => {
+                        tracing::warn!(%id, error = %e, "structured session: adapter failed to start");
+                        let mut sessions = inner.sessions.lock().await;
+                        if let Some(record) = sessions.get_mut(&id) {
+                            record.session.status = SessionStatus::Dead;
+                            record.session.activity = ActivityState::Error;
+                            record.session.activity_detail = Some(e.to_string());
+                            record.session.activity_since = Utc::now();
+                            let _ = inner.sidecar.write(&record.session);
+                            let _ = inner.events.send(CatalogEvent::SessionUpdated {
+                                session: record.session.clone(),
+                            });
+                        }
+                    }
+                }
+                drop_structured_lifecycle_permit(&inner);
+            });
+        }
+
         Ok(session)
     }
 
@@ -1682,6 +1717,7 @@ impl SessionManager {
                     structured_activity_watermark: None,
                     acp_event_pump: None,
                     auto_approve: false,
+                    pending_prompt: None,
                 },
             );
             let _ = self
@@ -1862,6 +1898,7 @@ impl SessionManager {
                     // Recovery cannot know the original preset's flag; the
                     // operator re-enables it by restarting with the preset.
                     auto_approve: false,
+                    pending_prompt: None,
                 },
             );
             if let Some((acp, events)) = event_pump {
@@ -2321,6 +2358,11 @@ async fn apply_structured_activity(
     if record.session.view != SessionView::Structured {
         return;
     }
+    // While the adapter is still booting, the background handshake task
+    // owns the activity state — the activity pass must not overwrite it.
+    if record.session.activity == ActivityState::Starting {
+        return;
+    }
     let current_events = record.acp_events.as_ref();
     match (expected_events, current_events) {
         (Some((expected, sequence)), Some(current)) if Arc::ptr_eq(expected, current) => {
@@ -2586,6 +2628,12 @@ async fn run_liveness_pass(inner: &Arc<Inner>) {
         let mut tmux_backed = Vec::new();
         let mut acp_backed = Vec::new();
         for (id, record) in running {
+            if record.is_starting_structured() {
+                // The adapter hasn't finished its handshake yet — no ACP
+                // handle and no tmux pane. Skip; the background task owns
+                // this session's lifecycle until the handshake settles.
+                continue;
+            }
             match &record.acp {
                 Some(acp) => acp_backed.push((*id, acp.clone())),
                 None => tmux_backed.push(*id),

crates/maestro-daemon/tests/acp.rs

@@ -130,6 +130,25 @@ async fn wait_for_exit(pid: u32) {
     assert!(!pid_alive(pid), "pid {pid} still alive");
 }
 
+/// Wait for a session's background ACP handshake to complete (activity
+/// transitions out of `Starting`). Returns the refreshed session.
+async fn wait_for_ready(manager: &SessionManager, id: uuid::Uuid) -> maestro_protocol::Session {
+    let deadline = Instant::now() + Duration::from_secs(10);
+    loop {
+        let session = manager
+            .snapshot()
+            .await
+            .into_iter()
+            .find(|s| s.id == id)
+            .expect("session exists");
+        if session.activity != ActivityState::Starting {
+            return session;
+        }
+        assert!(Instant::now() < deadline, "handshake timed out");
+        tokio::time::sleep(Duration::from_millis(20)).await;
+    }
+}
+
 #[tokio::test]
 async fn structured_spawn_starts_the_adapter_in_cwd_with_session_env() {
     let fx = DaemonFixture::new();
@@ -138,7 +157,7 @@ async fn structured_spawn_starts_the_adapter_in_cwd_with_session_env() {
     let mut env = fake.env();
     env.insert("FAKE_ACP_ECHO_ENV".into(), "MAESTRO_SESSION_ID".into());
 
-    let session = fx
+    let created = fx
         .manager
         .create(structured_command(
             cwd.path(),
@@ -148,8 +167,12 @@ async fn structured_spawn_starts_the_adapter_in_cwd_with_session_env() {
         .await
         .expect("create");
 
-    assert_eq!(session.view, SessionView::Structured);
-    assert_eq!(session.status, SessionStatus::Running);
+    assert_eq!(created.view, SessionView::Structured);
+    assert_eq!(created.status, SessionStatus::Running);
+    assert_eq!(created.activity, ActivityState::Starting);
+    assert!(created.acp_session_id.is_none());
+
+    let session = wait_for_ready(&fx.manager, created.id).await;
     assert_eq!(session.activity, ActivityState::Idle);
     let acp_id = session.acp_session_id.clone().expect("acp session id");
     assert!(acp_id.starts_with("fake-"), "{acp_id}");
@@ -164,7 +187,7 @@ async fn structured_spawn_starts_the_adapter_in_cwd_with_session_env() {
         "{log}"
     );
     assert!(
-        log.contains(&format!("env MAESTRO_SESSION_ID={}", session.id)),
+        log.contains(&format!("env MAESTRO_SESSION_ID={}", created.id)),
         "{log}"
     );
 
@@ -232,6 +255,7 @@ async fn structured_activity_tracks_turn_completion_and_failure() {
         .create(structured_command(cwd.path(), env, "codex"))
         .await
         .unwrap();
+    let session = wait_for_ready(&fx.manager, session.id).await;
 
     assert!(matches!(
         fx.manager
@@ -295,11 +319,12 @@ async fn projection_snapshot_and_live_stream_share_one_fold() {
     let fx = DaemonFixture::new();
     let fake = Fake::new();
     let cwd = TempDir::new().unwrap();
-    let session = fx
+    let created = fx
         .manager
         .create(structured(cwd.path(), fake.env()))
         .await
         .expect("create");
+    let session = wait_for_ready(&fx.manager, created.id).await;
 
     wait_for_async(Duration::from_secs(5), || async {
         fx.manager
@@ -397,6 +422,7 @@ async fn queued_prompt_is_a_durable_user_transcript_row() {
         .create(structured(cwd.path(), fake.env()))
         .await
         .expect("create");
+    let session = wait_for_ready(&fx.manager, session.id).await;
 
     assert!(matches!(
         fx.manager
@@ -442,6 +468,7 @@ async fn stale_turn_completion_cannot_end_the_next_turn() {
         .create(structured(cwd.path(), fake.env()))
         .await
         .unwrap();
+    wait_for_ready(&fx.manager, session.id).await;
 
     let maestro_daemon::session::BeginAcpTurn::Started(_, first) =
         fx.manager.begin_acp_turn(session.id).await.unwrap()
@@ -485,6 +512,7 @@ async fn cancelled_prompt_that_never_settles_fails_the_session() {
         .create(structured(cwd.path(), env))
         .await
         .unwrap();
+    wait_for_ready(&fx.manager, session.id).await;
 
     assert!(matches!(
         fx.manager
@@ -523,6 +551,7 @@ async fn cancellation_settlement_allows_the_next_prompt_permission() {
         .create(structured(cwd.path(), env))
         .await
         .unwrap();
+    wait_for_ready(&fx.manager, session.id).await;
 
     assert!(matches!(
         fx.manager
@@ -582,11 +611,12 @@ async fn recovery_loads_the_acp_session_without_duplicating_history() {
     let mut env = fake.env();
     env.insert("FAKE_ACP_LOAD_REPLAY".into(), "2".into());
 
-    let session = fx
+    let created = fx
         .manager
         .create(structured_command(cwd.path(), env, "codex"))
         .await
         .expect("create");
+    let session = wait_for_ready(&fx.manager, created.id).await;
     let acp_id = session.acp_session_id.clone().expect("acp id");
     wait_for_async(Duration::from_secs(5), || async {
         fx.manager
@@ -711,6 +741,7 @@ async fn shutdown_preserves_a_pristine_structured_worktree_for_recovery() {
         .await
         .expect("create");
     assert_eq!(session.cwd, worktree);
+    wait_for_ready(&fx.manager, session.id).await;
     push_all_to_origin(repo.path(), origin.path());
 
     fx.manager.shutdown().await;
@@ -759,6 +790,7 @@ async fn failed_recovery_cleans_its_fifo() {
         .create(structured(cwd.path(), fake.env()))
         .await
         .expect("create");
+    wait_for_ready(&fx.manager, session.id).await;
     let old_pid = fake.pid();
     fx.manager.shutdown().await;
     wait_for_exit(old_pid).await;
@@ -792,12 +824,15 @@ async fn missing_adapter_yields_a_failed_session_naming_the_install_command() {
         empty.path().to_string_lossy().into_owned(),
     )]);
 
-    let session = fx
+    let created = fx
         .manager
         .create(structured_command(cwd.path(), env, "codex"))
         .await
-        .expect("a failed session, not an error");
+        .expect("create registers a Starting session");
+    assert_eq!(created.activity, ActivityState::Starting);
 
+    // The background handshake fails because the adapter binary is missing.
+    let session = wait_for_ready(&fx.manager, created.id).await;
     assert_eq!(session.status, SessionStatus::Dead);
     assert_eq!(session.activity, ActivityState::Error);
     let detail = session.activity_detail.clone().expect("actionable detail");
@@ -810,13 +845,13 @@ async fn missing_adapter_yields_a_failed_session_naming_the_install_command() {
 
     // It is a real session: listed, on disk, and dismissable like any other
     // dead one.
-    assert!(fx.manager.has(session.id).await);
+    assert!(fx.manager.has(created.id).await);
     assert!(fx
         .sidecar_dir()
-        .join(format!("{}.json", session.id))
+        .join(format!("{}.json", created.id))
         .exists());
-    fx.manager.kill(session.id, false).await.expect("dismiss");
-    assert!(!fx.manager.has(session.id).await);
+    fx.manager.kill(created.id, false).await.expect("dismiss");
+    assert!(!fx.manager.has(created.id).await);
 }
 
 #[tokio::test]
@@ -825,20 +860,20 @@ async fn unsupported_structured_command_fails_without_launching_claude() {
     let fake = Fake::new();
     let cwd = TempDir::new().unwrap();
 
-    let session = fx
+    let err = fx
         .manager
         .create(structured_command(cwd.path(), fake.env(), "opencode"))
         .await
-        .expect("failed structured session is persisted");
+        .expect_err("unsupported command is rejected at request validation");
 
-    assert_eq!(session.status, SessionStatus::Dead);
-    let detail = session.activity_detail.expect("selection error");
-    assert!(detail.contains("Claude Code or Codex"), "{detail}");
+    assert!(
+        matches!(err, maestro_daemon::SessionError::BadRequest(ref msg) if msg.contains("Claude Code or Codex")),
+        "{err:?}"
+    );
     assert!(
         fake.log().is_empty(),
         "unsupported command launched an adapter"
     );
-    fx.manager.kill(session.id, false).await.expect("dismiss");
 }
 
 #[tokio::test]
@@ -853,6 +888,7 @@ async fn kill_sends_cancel_then_sigterm_and_removes_the_sidecar() {
         .create(structured(cwd.path(), fake.env()))
         .await
         .expect("create");
+    wait_for_ready(&fx.manager, session.id).await;
     let pid = fake.pid();
     assert!(pid_alive(pid));
 
@@ -895,6 +931,8 @@ async fn shutdown_reaps_every_adapter_child() {
         .create(structured(cwd.path(), b.env()))
         .await
         .expect("create b");
+    wait_for_ready(&fx.manager, sa.id).await;
+    wait_for_ready(&fx.manager, sb.id).await;
     let (pa, pb) = (a.pid(), b.pid());
     assert!(pid_alive(pa) && pid_alive(pb));
 
@@ -929,10 +967,13 @@ async fn dismissal_during_shutdown_does_not_restore_recovery_artifacts() {
         .create(structured(cwd.path(), env))
         .await
         .expect("create");
-    fx.manager
+    let blocker_session = fx
+        .manager
         .create(structured(cwd.path(), blocker.env()))
         .await
         .expect("create blocker");
+    wait_for_ready(&fx.manager, session.id).await;
+    wait_for_ready(&fx.manager, blocker_session.id).await;
 
     let manager = fx.manager.clone();
     let shutdown = tokio::spawn(async move { manager.shutdown().await });
@@ -984,6 +1025,7 @@ async fn shutdown_does_not_recover_an_adapter_that_already_exited() {
         .create(structured(cwd.path(), env))
         .await
         .expect("create");
+    wait_for_ready(&fx.manager, session.id).await;
     wait_for_exit(fake.pid()).await;
 
     fx.manager.shutdown().await;
@@ -1017,23 +1059,31 @@ async fn shutdown_waits_for_structured_creation_and_rejects_new_creates() {
     let mut env = fake.env();
     env.insert("FAKE_ACP_DELAY_SESSION_NEW_MS".into(), "500".into());
 
-    let create_cwd = cwd.path().to_path_buf();
-    let manager = fx.manager.clone();
-    let create = tokio::spawn(async move { manager.create(structured(&create_cwd, env)).await });
+    // create() returns immediately; the handshake runs in the background
+    // and holds a lifecycle permit.
+    let session = fx
+        .manager
+        .create(structured(cwd.path(), env))
+        .await
+        .expect("create");
+
+    // Wait until the adapter has received session/new (handshake in progress).
     wait_for_async(Duration::from_secs(5), || async {
         fake.log().contains("recv session/new")
     })
     .await;
 
+    // Shutdown must wait for the in-flight background handshake.
     let manager = fx.manager.clone();
     let shutdown = tokio::spawn(async move { manager.shutdown().await });
     tokio::time::sleep(Duration::from_millis(50)).await;
     assert!(
         !shutdown.is_finished(),
-        "shutdown returned before create finished"
+        "shutdown returned before handshake finished"
     );
 
-    let session = create.await.expect("create task").expect("create");
+    // The handshake completes in the background (500ms delay).
+    wait_for_ready(&fx.manager, session.id).await;
     let pid = fake.pid();
     shutdown.await.expect("shutdown task");
 
@@ -1066,27 +1116,37 @@ async fn structured_handshakes_run_independently() {
         gate.to_string_lossy().into_owned(),
     );
 
-    let first_cwd = cwd.path().to_path_buf();
-    let manager = fx.manager.clone();
-    let first =
-        tokio::spawn(async move { manager.create(structured(&first_cwd, blocked_env)).await });
-    wait_for_async(Duration::from_secs(5), || async {
-        blocked.log().contains("recv session/new")
-    })
-    .await;
+    // Both create() calls return immediately with Starting; the first
+    // adapter's handshake is gated while the second runs freely.
+    let first = fx
+        .manager
+        .create(structured(cwd.path(), blocked_env))
+        .await
+        .expect("first create");
+    let second = fx
+        .manager
+        .create(structured(cwd.path(), ready.env()))
+        .await
+        .expect("second create");
 
-    let second = tokio::time::timeout(
-        Duration::from_secs(5),
-        fx.manager.create(structured(cwd.path(), ready.env())),
-    )
-    .await
-    .expect("second handshake was blocked by the first")
-    .expect("second create");
-    assert_eq!(second.status, SessionStatus::Running);
-    assert!(!first.is_finished(), "the gate must still block the first");
+    // The second handshake completes independently of the first.
+    let second_ready = wait_for_ready(&fx.manager, second.id).await;
+    assert_eq!(second_ready.activity, ActivityState::Idle);
+
+    // The first handshake is still blocked.
+    let first_snap = fx
+        .manager
+        .snapshot()
+        .await
+        .into_iter()
+        .find(|s| s.id == first.id)
+        .unwrap();
+    assert_eq!(first_snap.activity, ActivityState::Starting);
 
     std::fs::write(&gate, b"release").unwrap();
-    let first = first.await.expect("first task").expect("first create");
+    let first_ready = wait_for_ready(&fx.manager, first.id).await;
+    assert_eq!(first_ready.activity, ActivityState::Idle);
+
     fx.manager.kill(first.id, false).await.expect("kill first");
     fx.manager
         .kill(second.id, false)
@@ -1114,16 +1174,18 @@ async fn shutdown_waits_for_every_admitted_structured_create() {
         gate_b.to_string_lossy().into_owned(),
     );
 
-    let create_a = {
-        let manager = fx.manager.clone();
-        let cwd = cwd.path().to_path_buf();
-        tokio::spawn(async move { manager.create(structured(&cwd, env_a)).await })
-    };
-    let create_b = {
-        let manager = fx.manager.clone();
-        let cwd = cwd.path().to_path_buf();
-        tokio::spawn(async move { manager.create(structured(&cwd, env_b)).await })
-    };
+    // Both create() calls return immediately; the background handshake
+    // tasks hold lifecycle permits and are blocked on their gates.
+    let session_a = fx
+        .manager
+        .create(structured(cwd.path(), env_a))
+        .await
+        .expect("create a");
+    let session_b = fx
+        .manager
+        .create(structured(cwd.path(), env_b))
+        .await
+        .expect("create b");
     wait_for_async(Duration::from_secs(5), || async {
         a.log().contains("recv session/new") && b.log().contains("recv session/new")
     })
@@ -1143,14 +1205,14 @@ async fn shutdown_waits_for_every_admitted_structured_create() {
     assert!(!shutdown.is_finished());
 
     std::fs::write(&gate_a, b"release").unwrap();
-    let session_a = create_a.await.expect("create a task").expect("create a");
+    wait_for_ready(&fx.manager, session_a.id).await;
     assert!(
         !shutdown.is_finished(),
         "shutdown ignored the second create"
     );
 
     std::fs::write(&gate_b, b"release").unwrap();
-    let session_b = create_b.await.expect("create b task").expect("create b");
+    wait_for_ready(&fx.manager, session_b.id).await;
     shutdown.await.expect("shutdown task");
 
     wait_for_exit(a.pid()).await;
@@ -1166,7 +1228,7 @@ async fn shutdown_waits_for_every_admitted_structured_create() {
 }
 
 #[tokio::test]
-async fn cancelling_a_structured_handshake_rolls_back_and_settles_admission() {
+async fn killing_a_starting_session_rolls_back_and_settles_admission() {
     let fx = DaemonFixture::new();
     let fake = Fake::new();
     let repo = TempDir::new().unwrap();
@@ -1192,40 +1254,30 @@ async fn cancelling_a_structured_handshake_rolls_back_and_settles_admission() {
         auto_approve: false,
     };
 
-    let create = {
-        let manager = fx.manager.clone();
-        tokio::spawn(async move { manager.create(request).await })
-    };
+    // create() returns immediately with Starting; the handshake is gated.
+    let session = fx.manager.create(request).await.expect("create");
+    assert_eq!(session.activity, ActivityState::Starting);
     wait_for_async(Duration::from_secs(5), || async {
         fake.log().contains("recv session/new")
     })
     .await;
-    let id = fake
-        .log()
-        .lines()
-        .find_map(|line| line.strip_prefix("env MAESTRO_SESSION_ID="))
-        .and_then(|id| uuid::Uuid::parse_str(id).ok())
-        .expect("session id in adapter log");
     let pid = fake.pid();
 
-    create.abort();
-    let shutdown = {
-        let manager = fx.manager.clone();
-        tokio::spawn(async move { manager.shutdown().await })
-    };
-    assert!(create.await.unwrap_err().is_cancelled());
-    tokio::time::timeout(Duration::from_secs(5), shutdown)
+    // Kill the session while its handshake is still in progress.
+    // force=true because the worktree has an unpushed branch commit.
+    fx.manager.kill(session.id, true).await.expect("kill");
+
+    // Release the gate so the background task can finish and settle.
+    std::fs::write(&gate, b"release").unwrap();
+
+    // Shutdown must not hang — the lifecycle permit is settled.
+    tokio::time::timeout(Duration::from_secs(5), fx.manager.shutdown())
         .await
-        .expect("cancelled admission kept shutdown waiting")
-        .expect("shutdown task");
+        .expect("shutdown hung on a settled permit");
+
     wait_for_exit(pid).await;
-    wait_for_async(Duration::from_secs(5), || async {
-        !fx.fifo_dir().join(format!("{id}.fifo")).exists()
-            && !repo.path().join("cancelled-create").exists()
-    })
-    .await;
     assert!(fx.manager.snapshot().await.is_empty());
-    let id = id.to_string();
+    let id = session.id.to_string();
     assert!(
         std::fs::read_dir(fx.sidecar_dir())
             .into_iter()
@@ -1235,7 +1287,7 @@ async fn cancelling_a_structured_handshake_rolls_back_and_settles_admission() {
                 .file_name()
                 .to_string_lossy()
                 .starts_with(&id)),
-        "cancelled create left a sidecar artifact"
+        "killed Starting session left a sidecar artifact"
     );
 }
 
@@ -1252,6 +1304,7 @@ async fn shutdown_drains_final_notifications_to_the_log() {
         .create(structured(cwd.path(), env))
         .await
         .expect("create");
+    wait_for_ready(&fx.manager, session.id).await;
     wait_for_async(Duration::from_secs(5), || async {
         fx.manager
             .read_acp_events(session.id, EventCursor::Since(0), 10)
@@ -1282,6 +1335,7 @@ async fn adapter_exit_marks_the_session_dead_and_keeps_it_listed() {
         .create(structured(cwd.path(), fake.env()))
         .await
         .expect("create");
+    wait_for_ready(&fx.manager, session.id).await;
     fx.manager.start_liveness_watcher(Duration::from_millis(50));
 
     // The agent dies out from under the daemon: the liveness pass, not tmux,

crates/maestro-daemon/tests/local_api.rs

@@ -154,7 +154,8 @@ async fn structured_session(h: &Harness, fake: &FakeAcp) -> Uuid {
 }
 
 async fn structured_session_with_env(h: &Harness, env: HashMap<String, String>) -> Uuid {
-    h.manager
+    let id = h
+        .manager
         .create(CreateSessionRequest {
             view: SessionView::Structured,
             cwd: "/tmp".into(),
@@ -166,7 +167,9 @@ async fn structured_session_with_env(h: &Harness, env: HashMap<String, String>)
         })
         .await
         .unwrap()
-        .id
+        .id;
+    wait_for_session_activity(h, id, ActivityState::Idle).await;
+    id
 }
 
 async fn wait_for_session_activity(h: &Harness, id: Uuid, expected: ActivityState) {
@@ -1494,6 +1497,12 @@ async fn events_ws_streams_structured_activity_without_hook_overrides() {
     let maestro_protocol::CatalogEvent::SessionAdded { session } = next_event(&mut ws).await else {
         panic!("expected structured SessionAdded")
     };
+    assert_eq!(session.activity, ActivityState::Starting);
+    // The background handshake completes and sends SessionUpdated → Idle.
+    let maestro_protocol::CatalogEvent::SessionUpdated { session } = next_event(&mut ws).await
+    else {
+        panic!("expected SessionUpdated after handshake")
+    };
     assert_eq!(session.activity, ActivityState::Idle);
 
     let client = reqwest::Client::new();

crates/maestro-protocol/src/lib.rs

@@ -175,6 +175,10 @@ pub enum ActivityState {
     AwaitingInput,
     /// An agent reported a failure, or a structured session/turn failed.
     Error,
+    /// The ACP adapter is booting; the session is registered but cannot accept
+    /// prompts yet. Older clients that do not know this variant degrade it to
+    /// `Idle` via the lenient deserializer — acceptable.
+    Starting,
 }
 
 impl<'de> Deserialize<'de> for ActivityState {
@@ -187,6 +191,7 @@ impl<'de> Deserialize<'de> for ActivityState {
             "Active" => Self::Active,
             "AwaitingInput" => Self::AwaitingInput,
             "Error" => Self::Error,
+            "Starting" => Self::Starting,
             // Known or not, any other spelling degrades to the neutral default
             _ => Self::Idle,
         })
@@ -225,9 +230,10 @@ where
         "Idle" => Ok(ActivityState::Idle),
         "AwaitingInput" => Ok(ActivityState::AwaitingInput),
         "Error" => Ok(ActivityState::Error),
+        "Starting" => Ok(ActivityState::Starting),
         other => Err(D::Error::unknown_variant(
             other,
-            &["Active", "Idle", "AwaitingInput", "Error"],
+            &["Active", "Idle", "AwaitingInput", "Error", "Starting"],
         )),
     }
 }

crates/maestro-testing/src/lib.rs

@@ -22,7 +22,8 @@ use chrono::Utc;
 use futures_util::{SinkExt, StreamExt};
 use maestro_protocol::{
     routes, ApiError, CatalogEvent, CreateSessionRequest, DaemonClient, DaemonInfo, DirListing,
-    GitRoot, RecentDirs, SendInputRequest, Session, SessionStatus, PROTOCOL_VERSION,
+    GitRoot, RecentDirs, SendInputRequest, Session, SessionStatus, StructuredPromptRequest,
+    PROTOCOL_VERSION,
 };
 use tokio::net::TcpListener;
 use tokio::sync::{broadcast, oneshot};
@@ -60,6 +61,8 @@ struct Inner {
     forced_error: Option<(u16, ApiError)>,
     /// Everything `POST /api/sessions/:id/input` was asked to type, in order.
     inputs: Vec<(Uuid, SendInputRequest)>,
+    /// Every ACP prompt sent to a structured session, in order.
+    structured_prompts: Vec<(Uuid, StructuredPromptRequest)>,
 }
 
 #[derive(Clone)]
@@ -92,6 +95,10 @@ impl MockDaemon {
             .route(routes::SESSIONS, get(list_sessions).post(create_session))
             .route(routes::patterns::SESSION, delete(kill_session))
             .route(routes::patterns::SESSION_INPUT, post(send_input))
+            .route(
+                routes::patterns::STRUCTURED_PROMPT,
+                post(structured_prompt),
+            )
             .route(routes::INFO, get(daemon_info))
             .route(routes::DIRS, get(list_dir))
             .route(routes::RECENT_DIRS, get(recent_dirs))
@@ -178,6 +185,16 @@ impl MockDaemon {
         self.state.inner.lock().expect("poisoned").inputs.clone()
     }
 
+    /// Every ACP prompt this daemon received, oldest first.
+    pub fn structured_prompts(&self) -> Vec<(Uuid, StructuredPromptRequest)> {
+        self.state
+            .inner
+            .lock()
+            .expect("poisoned")
+            .structured_prompts
+            .clone()
+    }
+
     pub fn session_count(&self) -> usize {
         self.state.inner.lock().expect("poisoned").sessions.len()
     }
@@ -266,6 +283,26 @@ async fn send_input(
     StatusCode::NO_CONTENT.into_response()
 }
 
+async fn structured_prompt(
+    State(s): State<AppState>,
+    Path(id): Path<Uuid>,
+    Json(req): Json<StructuredPromptRequest>,
+) -> Response {
+    if let Some(r) = forced(&s) {
+        return r;
+    }
+    let mut guard = s.inner.lock().expect("poisoned");
+    if !guard.sessions.iter().any(|x| x.id == id) {
+        return (
+            StatusCode::NOT_FOUND,
+            Json(ApiError::new("not_found", "no such session on this daemon")),
+        )
+            .into_response();
+    }
+    guard.structured_prompts.push((id, req));
+    StatusCode::NO_CONTENT.into_response()
+}
+
 async fn daemon_info(State(s): State<AppState>) -> Response {
     if let Some(r) = forced(&s) {
         return r;

crates/maestro-tui/src/palette.rs

@@ -82,7 +82,7 @@ impl Surface {
     pub fn activity(&self, state: ActivityState) -> Color {
         match state {
             ActivityState::Active => self.active,
-            ActivityState::Idle => self.idle,
+            ActivityState::Idle | ActivityState::Starting => self.idle,
             ActivityState::AwaitingInput => self.awaiting,
             ActivityState::Error => self.error,
         }
@@ -928,9 +928,10 @@ pub fn contrast_ratio(a: Color, b: Color) -> Option<f64> {
 mod tests {
     use super::*;
 
-    const STATES: [ActivityState; 4] = [
+    const STATES: [ActivityState; 5] = [
         ActivityState::Active,
         ActivityState::Idle,
+        ActivityState::Starting,
         ActivityState::AwaitingInput,
         ActivityState::Error,
     ];

crates/maestro-tui/src/sidebar.rs

@@ -979,6 +979,7 @@ mod tests {
         for state in [
             ActivityState::Active,
             ActivityState::Idle,
+            ActivityState::Starting,
             ActivityState::AwaitingInput,
             ActivityState::Error,
         ] {
@@ -1009,6 +1010,7 @@ mod tests {
         for state in [
             ActivityState::Active,
             ActivityState::Idle,
+            ActivityState::Starting,
             ActivityState::AwaitingInput,
             ActivityState::Error,
         ] {

docs/SIDEBAR.md

@@ -160,6 +160,7 @@ The state word is never spelled out — the colour carries it.
 | ---------------- | --------- | ---------------- |
 | `Active`         | `--live`  | `active`         |
 | `Idle`           | `--muted` | `idle`           |
+| `Starting`       | `--muted` | `idle`           |
 | `AwaitingInput`  | `--warn`  | `awaiting`       |
 | `Error`          | `--danger`| `error`          |
 

web/src/types.ts

@@ -11,7 +11,7 @@ export type SessionStatus = "Running" | "Dead";
 /** Daemon-inferred activity dimension, orthogonal to `SessionStatus` (NAP-340).
  * Absent on payloads from daemons that predate the field. `Error` is only set
  * when an agent reports failure (#105); the daemon never infers it. */
-export type ActivityState = "Active" | "Idle" | "AwaitingInput" | "Error";
+export type ActivityState = "Active" | "Idle" | "AwaitingInput" | "Error" | "Starting";
 
 export interface Session {
   id: Uuid;