feat(maestro): add maestro send for typing into a session

Adds POST /api/sessions/:id/input and a CLI command on top of it, so a
script (or another agent) can hand an instruction to a running session
without attaching to it.

The text goes in as one write and the Enter follows 150ms later: agents
that run a full-screen prompt coalesce a burst of input into a paste, and
a newline inside that burst becomes a line break instead of sending the
message. `--no-enter` skips the Enter and leaves the text in the prompt.

The session argument takes an ID, a unique ID prefix, or a session name;
names win over prefixes. A session whose pane has exited is refused (409)
rather than silently accepted — unlike a stray keystroke on an attach
socket, a send that goes nowhere is worth hearing about.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -11,6 +11,7 @@ persistence, WebSocket for transport.
 maestro daemon            tmux wrapper + session API on 127.0.0.1:7070
   ├── GET/POST /api/sessions        list / spawn
   ├── DELETE   /api/sessions/:id    kill
+  ├── POST     /api/sessions/:id/input  type text into a session
   ├── GET      /api/info            hostname, version, home dir, spawn presets
   ├── GET      /api/dirs            directory listing (spawn autocomplete)
   ├── GET      /api/recent-dirs     spawn history
@@ -18,7 +19,7 @@ maestro daemon            tmux wrapper + session API on 127.0.0.1:7070
   ├── WS       /api/events          Snapshot + session deltas
   └── WS       /api/attach/:id      raw PTY bytes
 
-maestro list/spawn/attach/kill      CLI client
+maestro list/spawn/attach/kill/send  CLI client
 maestro tui                         ratatui client
 maestro-web                         serves the SPA, reverse-proxies /api/* to the daemon
 ```

crates/maestro-cli/src/cli.rs

@@ -41,6 +41,9 @@ 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(SendArgs),
     /// Install or update the agent activity hook (#106).
     Hooks(HooksArgs),
 }
@@ -103,6 +106,20 @@ pub struct AttachArgs {
     pub detach_key: String,
 }
 
+/// `maestro send <session> <text...>`
+#[derive(Debug, clap::Args)]
+pub struct SendArgs {
+    /// Session to type into: its ID, a unique ID prefix, or its name.
+    pub session: String,
+    /// Text to send. Omit it to read the text from stdin.
+    #[arg(trailing_var_arg = true, allow_hyphen_values = true)]
+    pub text: Vec<String>,
+    /// Leave the text sitting in the session's prompt instead of pressing
+    /// Enter after it.
+    #[arg(long)]
+    pub no_enter: bool,
+}
+
 #[derive(Debug, clap::Args)]
 pub struct KillArgs {
     /// Session ID to kill.
@@ -245,6 +262,40 @@ mod tests {
         }
     }
 
+    #[test]
+    fn parses_send_joining_the_message_words() {
+        let cli =
+            Cli::try_parse_from(["maestro", "send", "planner", "run", "the", "tests"]).unwrap();
+        let Command::Send(a) = cli.command else {
+            panic!("expected send")
+        };
+        assert_eq!(a.session, "planner");
+        assert_eq!(a.text, vec!["run", "the", "tests"]);
+        assert!(!a.no_enter);
+    }
+
+    /// The message is trailing_var_arg, so a word starting with `-` inside it
+    /// is text, not a flag clap should reject.
+    #[test]
+    fn send_message_may_start_with_a_dash() {
+        let cli =
+            Cli::try_parse_from(["maestro", "send", "--no-enter", "planner", "--force"]).unwrap();
+        let Command::Send(a) = cli.command else {
+            panic!("expected send")
+        };
+        assert!(a.no_enter);
+        assert_eq!(a.text, vec!["--force"]);
+    }
+
+    #[test]
+    fn send_text_may_be_omitted_for_stdin() {
+        let cli = Cli::try_parse_from(["maestro", "send", "planner"]).unwrap();
+        let Command::Send(a) = cli.command else {
+            panic!("expected send")
+        };
+        assert!(a.text.is_empty());
+    }
+
     #[test]
     fn rejects_env_without_equals() {
         let err = Cli::try_parse_from([

crates/maestro-cli/src/dispatch.rs

@@ -10,7 +10,7 @@ use maestro_protocol::DaemonClient;
 
 use crate::attach::{parse_detach_key, run_attach_url};
 use crate::cli::Command;
-use crate::sessions::{run_kill, run_list, run_spawn};
+use crate::sessions::{run_kill, run_list, run_send, run_spawn};
 use maestro_config::{default_config_path, MaestroConfigFile};
 
 #[derive(Debug, thiserror::Error)]
@@ -24,6 +24,10 @@ pub enum CliError {
     Attach(#[from] crate::attach::AttachError),
     #[error("{0}")]
     Hooks(#[from] maestro_hooks::HooksError),
+    #[error("{0}")]
+    Resolve(#[from] crate::sessions::ResolveError),
+    #[error("nothing to send: pass the text as arguments or pipe it on stdin")]
+    NothingToSend,
     #[error("could not determine the home directory ($HOME unset?)")]
     NoHome,
     #[error("{0}")]
@@ -82,6 +86,10 @@ pub async fn dispatch(
             run_kill(&daemon, &args).await?;
             println!("killed {}", args.session_id);
         }
+        Command::Send(args) => {
+            let id = run_send(&daemon, &args, &mut std::io::stdin()).await?;
+            println!("sent to {id}");
+        }
         Command::Hooks(_) => unreachable!("hooks handled before the daemon client exists"),
     }
     Ok(())

crates/maestro-cli/src/sessions.rs

@@ -5,12 +5,13 @@ use std::io::Write;
 
 use maestro_protocol::display::abbreviate_dir;
 use maestro_protocol::{
-    ActivityState, ClientError, CreateSessionRequest, DaemonClient, DaemonInfo, Session,
-    SessionStatus, WorktreeSpec,
+    ActivityState, ClientError, CreateSessionRequest, DaemonClient, DaemonInfo, SendInputRequest,
+    Session, SessionStatus, WorktreeSpec,
 };
 use serde_json::Value;
 
-use crate::cli::{KillArgs, ListArgs, SpawnArgs};
+use crate::cli::{KillArgs, ListArgs, SendArgs, SpawnArgs};
+use crate::dispatch::CliError;
 
 /// `maestro list`
 pub async fn run_list(
@@ -66,6 +67,92 @@ pub async fn run_kill(client: &DaemonClient, args: &KillArgs) -> Result<(), Clie
     client.kill_session(args.session_id, args.force).await
 }
 
+/// Nothing on the daemon answers to what the operator named.
+#[derive(Debug, thiserror::Error)]
+pub enum ResolveError {
+    #[error("no session matches {0:?} — run `maestro list` to see what is running")]
+    NoMatch(String),
+    #[error("{0:?} matches {1} sessions; use a session id instead")]
+    Ambiguous(String, usize),
+}
+
+/// Turn what the operator typed into a session id: a full ID, a unique ID
+/// prefix, or a session's name (#125), matched case-insensitively. Names come
+/// first — an operator who named a session after a hex string meant the name.
+pub fn resolve_session(sessions: &[Session], needle: &str) -> Result<uuid::Uuid, ResolveError> {
+    let needle = needle.trim();
+    let by_name: Vec<&Session> = sessions
+        .iter()
+        .filter(|s| {
+            maestro_protocol::display::custom_name(s)
+                .is_some_and(|n| n.eq_ignore_ascii_case(needle))
+        })
+        .collect();
+    match by_name.len() {
+        1 => return Ok(by_name[0].id),
+        0 => {}
+        n => return Err(ResolveError::Ambiguous(needle.to_string(), n)),
+    }
+
+    let by_id: Vec<&Session> = sessions
+        .iter()
+        .filter(|s| {
+            s.id.to_string()
+                .to_ascii_lowercase()
+                .starts_with(&needle.to_ascii_lowercase())
+        })
+        .collect();
+    match by_id.len() {
+        1 => Ok(by_id[0].id),
+        0 => Err(ResolveError::NoMatch(needle.to_string())),
+        n => Err(ResolveError::Ambiguous(needle.to_string(), n)),
+    }
+}
+
+/// `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.
+#[allow(clippy::result_large_err)]
+pub async fn run_send(
+    client: &DaemonClient,
+    args: &SendArgs,
+    stdin: &mut impl std::io::Read,
+) -> Result<uuid::Uuid, CliError> {
+    let text = if args.text.is_empty() {
+        let mut buf = String::new();
+        stdin.read_to_string(&mut buf)?;
+        // One trailing newline is how a pipe ends, not part of the message —
+        // keeping it would submit the text twice.
+        buf.strip_suffix('\n')
+            .map(|t| t.strip_suffix('\r').unwrap_or(t))
+            .unwrap_or(&buf)
+            .to_string()
+    } else {
+        args.text.join(" ")
+    };
+    if text.is_empty() {
+        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)?
+        }
+    };
+
+    let req = SendInputRequest {
+        text,
+        submit: !args.no_enter,
+    };
+    client.send_input(id, &req).await?;
+    Ok(id)
+}
+
 #[allow(clippy::write_literal)]
 fn print_session_table(out: &mut impl Write, sessions: &[Session], info: &DaemonInfo) {
     if sessions.is_empty() {
@@ -218,6 +305,63 @@ mod tests {
         assert!(out.contains("bash [claude]"), "{out}");
     }
 
+    fn named(id: u128, name: &str) -> Session {
+        let mut s = session("/tmp", "claude", id);
+        s.metadata
+            .insert("name".into(), serde_json::Value::String(name.into()));
+        s
+    }
+
+    #[test]
+    fn resolves_by_name_id_prefix_and_reports_what_it_cannot() {
+        use super::{resolve_session, ResolveError};
+
+        // Ids that differ in their first characters, so a short prefix is
+        // enough to pick one — the ergonomics the prefix match exists for.
+        let (a, b) = (1u128 << 124, 2u128 << 124);
+        let sessions = vec![named(a, "planner"), named(b, "builder")];
+        let one = Uuid::from_u128(a);
+
+        assert_eq!(resolve_session(&sessions, "planner").unwrap(), one);
+        // Names match case-insensitively and ignore surrounding space.
+        assert_eq!(resolve_session(&sessions, " Planner ").unwrap(), one);
+        // An id prefix works when it picks exactly one session.
+        let prefix = &one.to_string()[..8];
+        assert_eq!(resolve_session(&sessions, prefix).unwrap(), one);
+        assert!(matches!(
+            resolve_session(&sessions, "nope"),
+            Err(ResolveError::NoMatch(_))
+        ));
+    }
+
+    /// Two sessions sharing a name is legal — the daemon never enforced
+    /// uniqueness — so `send` must refuse rather than pick one.
+    #[test]
+    fn an_ambiguous_name_is_refused() {
+        use super::{resolve_session, ResolveError};
+
+        let sessions = vec![named(1 << 124, "worker"), named(2 << 124, "worker")];
+        assert!(matches!(
+            resolve_session(&sessions, "worker"),
+            Err(ResolveError::Ambiguous(_, 2))
+        ));
+    }
+
+    /// A session named after its own id prefix means the name: an operator
+    /// who typed a name they chose should not be routed by hex coincidence.
+    #[test]
+    fn names_win_over_id_prefixes() {
+        use super::resolve_session;
+
+        let two = Uuid::from_u128(2 << 124);
+        let prefix = two.to_string()[..8].to_string();
+        let sessions = vec![named(1 << 124, &prefix), session("/tmp", "bash", 2 << 124)];
+        assert_eq!(
+            resolve_session(&sessions, &prefix).unwrap(),
+            Uuid::from_u128(1 << 124)
+        );
+    }
+
     #[test]
     fn empty_sessions() {
         let mut buf = Vec::new();

crates/maestro-cli/tests/against_mock_daemon.rs

@@ -108,3 +108,110 @@ async fn spawn_round_trips_through_the_daemon() {
         .expect("kill");
     assert_eq!(mock.session_count(), 0);
 }
+
+#[tokio::test]
+async fn send_types_text_and_submits_by_default() {
+    let mock = MockDaemon::start().await;
+    let id = Uuid::from_u128(7);
+    mock.add_session(session(id, "/home/mock/work", "claude"));
+
+    let args = maestro_cli::cli::SendArgs {
+        session: id.to_string(),
+        text: vec!["run".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);
+    let inputs = mock.inputs();
+    assert_eq!(inputs.len(), 1);
+    assert_eq!(inputs[0].0, id);
+    assert_eq!(inputs[0].1.text, "run the tests");
+    assert!(inputs[0].1.submit, "Enter is the default");
+}
+
+/// `--no-enter` leaves the text in the prompt; the flag has to survive the
+/// whole way to the daemon or the message is sent anyway.
+#[tokio::test]
+async fn send_without_enter_leaves_the_text_unsubmitted() {
+    let mock = MockDaemon::start().await;
+    let id = Uuid::from_u128(8);
+    mock.add_session(session(id, "/tmp", "bash"));
+
+    let args = maestro_cli::cli::SendArgs {
+        session: id.to_string(),
+        text: vec!["ls".into()],
+        no_enter: true,
+    };
+    maestro_cli::sessions::run_send(&mock.client(), &args, &mut std::io::empty())
+        .await
+        .expect("send");
+
+    assert!(!mock.inputs()[0].1.submit);
+}
+
+/// No text arguments → the message comes from stdin, minus the trailing
+/// newline a pipe or heredoc adds.
+#[tokio::test]
+async fn send_reads_stdin_and_drops_its_trailing_newline() {
+    let mock = MockDaemon::start().await;
+    let id = Uuid::from_u128(9);
+    mock.add_session(session(id, "/tmp", "bash"));
+
+    let args = maestro_cli::cli::SendArgs {
+        session: id.to_string(),
+        text: Vec::new(),
+        no_enter: false,
+    };
+    let mut stdin = std::io::Cursor::new(b"multi\nline\n".to_vec());
+    maestro_cli::sessions::run_send(&mock.client(), &args, &mut stdin)
+        .await
+        .expect("send");
+
+    assert_eq!(mock.inputs()[0].1.text, "multi\nline");
+}
+
+/// A session named through `PATCH /api/sessions/:id` is addressable by that
+/// name, so scripts don't have to carry a UUID around.
+#[tokio::test]
+async fn send_resolves_a_session_by_name() {
+    let mock = MockDaemon::start().await;
+    let id = Uuid::from_u128(10);
+    let mut named = session(id, "/tmp", "claude");
+    named
+        .metadata
+        .insert("name".into(), serde_json::Value::String("planner".into()));
+    mock.add_session(named);
+    mock.add_session(session(Uuid::from_u128(11), "/tmp", "bash"));
+
+    let args = maestro_cli::cli::SendArgs {
+        session: "Planner".into(),
+        text: vec!["go".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);
+}
+
+#[tokio::test]
+async fn send_to_an_unknown_session_fails_without_typing_anything() {
+    let mock = MockDaemon::start().await;
+    mock.add_session(session(Uuid::from_u128(12), "/tmp", "bash"));
+
+    let args = maestro_cli::cli::SendArgs {
+        session: "nope".into(),
+        text: vec!["hi".into()],
+        no_enter: false,
+    };
+    let err = maestro_cli::sessions::run_send(&mock.client(), &args, &mut std::io::empty())
+        .await
+        .expect_err("should not resolve");
+
+    assert!(err.to_string().contains("no session matches"), "{err}");
+    assert!(mock.inputs().is_empty());
+}

crates/maestro-daemon/src/local_api.rs

@@ -20,7 +20,7 @@ use axum::{Json, Router};
 use maestro_config::SpawnPreset;
 use maestro_protocol::{
     routes, ApiError, CatalogEvent, CreateSessionRequest, DaemonInfo, GitRoot, NameBatch,
-    RenameSessionRequest, ReportActivityRequest, Session, PROTOCOL_VERSION,
+    RenameSessionRequest, ReportActivityRequest, SendInputRequest, Session, PROTOCOL_VERSION,
 };
 use serde::Deserialize;
 use uuid::Uuid;
@@ -44,6 +44,7 @@ pub fn router(state: LocalApiState) -> Router {
     Router::new()
         .route(routes::SESSIONS, get(list_sessions).post(create_session))
         .route(routes::patterns::SESSION_ACTIVITY, post(report_activity))
+        .route(routes::patterns::SESSION_INPUT, post(send_input))
         .route(
             routes::patterns::SESSION,
             delete(kill_session).patch(rename_session),
@@ -100,6 +101,9 @@ fn session_error_status(code: &str) -> StatusCode {
         "invalid_env" => 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
+        // the daemon can do about it.
+        "not_running" => StatusCode::CONFLICT,
         _ => StatusCode::BAD_GATEWAY,
     }
 }
@@ -247,6 +251,28 @@ async fn report_activity(
     }
 }
 
+/// `POST /api/sessions/:id/input`: type text into a session's pane, then
+/// press Enter unless the request turns `submit` off. Answers `204 No
+/// Content`. A session that has exited is refused (409) rather than accepted
+/// into nowhere.
+async fn send_input(
+    State(s): State<LocalApiState>,
+    Path(id): Path<Uuid>,
+    Json(body): Json<SendInputRequest>,
+) -> Response {
+    match s.manager.send_input(id, &body.text, body.submit).await {
+        Ok(()) => StatusCode::NO_CONTENT.into_response(),
+        Err(e) => {
+            let info = e.to_error_info();
+            error_response(
+                session_error_status(&info.code),
+                info.code.as_str(),
+                info.message.as_str(),
+            )
+        }
+    }
+}
+
 fn error_response(status: StatusCode, code: &str, message: &str) -> Response {
     (status, Json(ApiError::new(code, message))).into_response()
 }

crates/maestro-daemon/src/session.rs

@@ -40,6 +40,15 @@ pub const DEFAULT_LIVENESS_INTERVAL: Duration = Duration::from_secs(2);
 /// attempt, which is all #83 needs.
 pub const DEFAULT_BLOCKED_WORK_INTERVAL: Duration = Duration::from_secs(15);
 
+/// Gap between the text of a `send` and the Enter that submits it.
+///
+/// Agents that run a full-screen prompt (Claude Code, opencode) coalesce a
+/// burst of input into one paste; a newline inside that burst becomes a line
+/// break in the message instead of sending it. Landing the Enter as its own
+/// write, after the reader has drained the text, is what makes the message
+/// actually go.
+const SUBMIT_DELAY: Duration = Duration::from_millis(150);
+
 /// Per-session daemon-local bookkeeping that complements the public `Session`.
 #[derive(Debug)]
 pub struct SessionRecord {
@@ -78,6 +87,11 @@ pub enum SessionError {
     NotFound(Uuid),
     #[error("invalid environment variable name: {0:?}")]
     InvalidEnv(String),
+    /// The session exists but its pane is gone, so there is nothing to type
+    /// into. Writing to a dead session is a client bug worth reporting, unlike
+    /// a stray keystroke on an attach socket, which is dropped.
+    #[error("session is no longer running: {0}")]
+    NotRunning(Uuid),
     /// 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.
@@ -94,6 +108,7 @@ impl SessionError {
             SessionError::Io(_) => "io_failed",
             SessionError::NotFound(_) => "not_found",
             SessionError::InvalidEnv(_) => "invalid_env",
+            SessionError::NotRunning(_) => "not_running",
             SessionError::KillGuarded(_) => "kill_guarded",
         };
         let unsaved_work = match self {
@@ -671,6 +686,33 @@ impl SessionManager {
             .map_err(SessionError::Tmux)
     }
 
+    /// Type `text` into a session's pane, with an Enter after it when
+    /// `submit` is set.
+    ///
+    /// Unlike [`Self::send_keys`], a dead session is an error: the caller
+    /// asked for text to land somewhere, and a silent success would let a
+    /// script believe an agent had been told something it never heard.
+    pub async fn send_input(&self, id: Uuid, text: &str, submit: bool) -> Result<(), SessionError> {
+        match self.status(id).await {
+            None => return Err(SessionError::NotFound(id)),
+            Some(SessionStatus::Dead) => return Err(SessionError::NotRunning(id)),
+            Some(SessionStatus::Running) => {}
+        }
+        let tmux = self.inner.tmux.clone();
+        let bytes = text.as_bytes().to_vec();
+        tmux_blocking(move || tmux.send_keys(id, &bytes))
+            .await
+            .map_err(SessionError::Tmux)?;
+        if submit {
+            tokio::time::sleep(SUBMIT_DELAY).await;
+            let tmux = self.inner.tmux.clone();
+            tmux_blocking(move || tmux.send_keys(id, b"\r"))
+                .await
+                .map_err(SessionError::Tmux)?;
+        }
+        Ok(())
+    }
+
     /// Resize a session's window. No-op for a dead session, as with
     /// [`Self::send_keys`].
     pub async fn resize(&self, id: Uuid, cols: u16, rows: u16) -> Result<(), SessionError> {

crates/maestro-e2e/tests/e2e.rs

@@ -1250,6 +1250,143 @@ async fn cli_list_reads_from_daemon() {
     );
 }
 
+/// `maestro send` end to end: the shipped binary, a real daemon, a real tmux
+/// pane. The shell only runs the command if the Enter arrived as its own
+/// write after the text, so the file appearing is the whole path working.
+#[tokio::test(flavor = "multi_thread")]
+async fn cli_send_types_a_command_into_a_live_shell() {
+    let (daemon, client) = bring_up().await;
+    let cwd = TempDir::new().unwrap();
+    let sess = client
+        .spawn_session(&create_req(cwd.path(), "bash --norc --noprofile"))
+        .await
+        .expect("spawn bash");
+
+    let home = TempDir::new().unwrap();
+    let cfg_path = home.path().join("config.toml");
+    let out = run_cli(
+        &["send", &sess.id.to_string(), "touch", "marker.txt"],
+        &[
+            ("HOME", home.path().to_str().unwrap()),
+            ("MAESTRO_CONFIG", cfg_path.to_str().unwrap()),
+            ("MAESTRO_DAEMON_URL", &daemon.http_base()),
+        ],
+    );
+    assert!(
+        out.status.success(),
+        "send failed: {}",
+        String::from_utf8_lossy(&out.stderr)
+    );
+
+    let marker = cwd.path().join("marker.txt");
+    wait_for_async(
+        "the shell runs the sent command",
+        Duration::from_secs(10),
+        || {
+            let marker = marker.clone();
+            async move { marker.exists() }
+        },
+    )
+    .await;
+
+    client.kill_session(sess.id).await.expect("kill");
+}
+
+/// `--no-enter` fills the prompt without submitting: the command must sit
+/// there unrun. Same setup as the test above, so the only difference is the
+/// flag.
+#[tokio::test(flavor = "multi_thread")]
+async fn send_without_enter_does_not_run_the_command() {
+    let (daemon, client) = bring_up().await;
+    let cwd = TempDir::new().unwrap();
+    let sess = client
+        .spawn_session(&create_req(cwd.path(), "bash --norc --noprofile"))
+        .await
+        .expect("spawn bash");
+
+    let home = TempDir::new().unwrap();
+    let out = run_cli(
+        &[
+            "send",
+            "--no-enter",
+            &sess.id.to_string(),
+            "touch",
+            "unsubmitted.txt",
+        ],
+        &[
+            ("HOME", home.path().to_str().unwrap()),
+            (
+                "MAESTRO_CONFIG",
+                home.path().join("c.toml").to_str().unwrap(),
+            ),
+            ("MAESTRO_DAEMON_URL", &daemon.http_base()),
+        ],
+    );
+    assert!(
+        out.status.success(),
+        "send failed: {}",
+        String::from_utf8_lossy(&out.stderr)
+    );
+
+    tokio::time::sleep(Duration::from_secs(2)).await;
+    assert!(
+        !cwd.path().join("unsubmitted.txt").exists(),
+        "the command ran despite --no-enter"
+    );
+
+    client.kill_session(sess.id).await.expect("kill");
+}
+
+/// A session whose command exited still exists in the catalog, but its pane
+/// is gone. Typing into it is refused instead of being swallowed — a script
+/// that sends an instruction to a dead agent has to hear about it.
+#[tokio::test(flavor = "multi_thread")]
+async fn send_to_a_dead_session_is_refused() {
+    use maestro_protocol::{SendInputRequest, SessionStatus};
+    let (_daemon, client) = bring_up().await;
+    let cwd = TempDir::new().unwrap();
+    let sess = client
+        .spawn_session(&create_req(cwd.path(), "true"))
+        .await
+        .expect("spawn true");
+
+    wait_for_async(
+        "the session to be seen dead",
+        Duration::from_secs(15),
+        || {
+            let client = client.clone();
+            let id = sess.id;
+            async move {
+                client
+                    .list_sessions()
+                    .await
+                    .map(|ss| {
+                        ss.iter()
+                            .any(|s| s.id == id && s.status == SessionStatus::Dead)
+                    })
+                    .unwrap_or(false)
+            }
+        },
+    )
+    .await;
+
+    let err = client
+        .daemon()
+        .send_input(
+            sess.id,
+            &SendInputRequest {
+                text: "hello".into(),
+                submit: true,
+            },
+        )
+        .await
+        .expect_err("a dead session cannot be typed into");
+    assert!(
+        err.to_string().contains("no longer running"),
+        "unexpected error: {err}"
+    );
+}
+
 #[tokio::test(flavor = "multi_thread")]
 async fn cli_list_fails_when_daemon_is_down() {
     let dead_daemon = format!("http://127.0.0.1:{}", maestro_e2e::util::free_port());

crates/maestro-protocol/src/client.rs

@@ -16,7 +16,7 @@ use uuid::Uuid;
 use crate::routes::{self, UrlError};
 use crate::{
     ApiError, BranchInfo, CreateSessionRequest, DaemonInfo, DirListing, ErrorInfo, GitRoot,
-    Project, RecentDirs, RenameSessionRequest, ReportActivityRequest, Session,
+    Project, RecentDirs, RenameSessionRequest, ReportActivityRequest, SendInputRequest, Session,
 };
 
 /// Time budget for establishing a TCP connection to the daemon.
@@ -155,6 +155,17 @@ impl DaemonClient {
         Ok(())
     }
 
+    /// `POST /api/sessions/:id/input`: type text into a session's pane, with
+    /// an Enter after it unless `submit` is off. Answers `204 No Content`; a
+    /// session that has exited is refused rather than silently accepted.
+    pub async fn send_input(&self, id: Uuid, req: &SendInputRequest) -> Result<(), ClientError> {
+        let resp = self
+            .send(Method::POST, &routes::session_input(id), &[], Some(req))
+            .await?;
+        check(resp).await?;
+        Ok(())
+    }
+
     pub async fn daemon_info(&self) -> Result<DaemonInfo, ClientError> {
         self.get(routes::INFO, &[]).await
     }

crates/maestro-protocol/src/display.rs

@@ -7,6 +7,15 @@ use std::path::{Path, PathBuf};
 
 use crate::Session;
 
+/// The name a session was given (#125), if any. `None` for one that was never
+/// renamed — clients fall back to the command.
+pub fn custom_name(s: &Session) -> Option<&str> {
+    match s.metadata.get("name") {
+        Some(serde_json::Value::String(name)) => Some(name.as_str()),
+        _ => None,
+    }
+}
+
 /// Collapse a daemon's home dir to `~`. `home` empty leaves the path
 /// untouched. Mirrors the web's `abbreviateCwd`.
 pub fn abbreviate_dir(path: &Path, home: &str) -> String {

crates/maestro-protocol/src/lib.rs

@@ -512,6 +512,24 @@ pub struct NameBatch {
     pub names: Vec<String>,
 }
 
+/// HTTP `POST /api/sessions/:id/input` body: text typed into a session's
+/// pane, as if the operator had typed it on an attached terminal.
+///
+/// `submit` presses Enter after the text — what makes `maestro send` a way to
+/// give an agent an instruction rather than only to fill its prompt. It goes
+/// out as its own write a beat later, because a TUI agent that reads the text
+/// as one paste would otherwise swallow the newline into the message.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct SendInputRequest {
+    pub text: String,
+    #[serde(default = "submit_default")]
+    pub submit: bool,
+}
+
+fn submit_default() -> bool {
+    true
+}
+
 /// Longest session name the daemon stores (#125), in characters. A name is a
 /// sidebar card's line 1; past this it only truncates on every client anyway.
 pub const MAX_SESSION_NAME_LEN: usize = 64;

crates/maestro-protocol/src/routes.rs

@@ -49,6 +49,11 @@ pub fn session_activity(id: Uuid) -> String {
     format!("{SESSIONS}/{id}/activity")
 }
 
+/// `POST /api/sessions/:id/input`: type text into a session's pane.
+pub fn session_input(id: Uuid) -> String {
+    format!("{SESSIONS}/{id}/input")
+}
+
 /// `WS /api/attach/:id` — raw PTY bytes.
 pub fn attach(id: Uuid) -> String {
     format!("{API_PREFIX}/attach/{id}")
@@ -59,6 +64,7 @@ pub fn attach(id: Uuid) -> String {
 pub mod patterns {
     pub const SESSION: &str = "/api/sessions/:id";
     pub const SESSION_ACTIVITY: &str = "/api/sessions/:id/activity";
+    pub const SESSION_INPUT: &str = "/api/sessions/:id/input";
     pub const ATTACH: &str = "/api/attach/:id";
 }
 
@@ -170,6 +176,10 @@ mod tests {
             session_activity(id()),
             "/api/sessions/6f1a7c0e-0f5e-4a2b-9a3d-6b1c2d3e4f50/activity"
         );
+        assert_eq!(
+            session_input(id()),
+            "/api/sessions/6f1a7c0e-0f5e-4a2b-9a3d-6b1c2d3e4f50/input"
+        );
         assert_eq!(
             attach(id()),
             "/api/attach/6f1a7c0e-0f5e-4a2b-9a3d-6b1c2d3e4f50"
@@ -192,6 +202,10 @@ mod tests {
             patterns::SESSION_ACTIVITY.trim_end_matches(":id/activity"),
             session(id()).trim_end_matches(&id().to_string())
         );
+        assert_eq!(
+            patterns::SESSION_INPUT.trim_end_matches(":id/input"),
+            session(id()).trim_end_matches(&id().to_string())
+        );
         assert_eq!(
             patterns::ATTACH.trim_end_matches(":id"),
             attach(id()).trim_end_matches(&id().to_string())

crates/maestro-testing/src/lib.rs

@@ -16,13 +16,13 @@ use axum::extract::ws::{Message, WebSocket, WebSocketUpgrade};
 use axum::extract::{Path, Query, State};
 use axum::http::StatusCode;
 use axum::response::{IntoResponse, Response};
-use axum::routing::{any, delete, get};
+use axum::routing::{any, delete, get, post};
 use axum::{Json, Router};
 use chrono::Utc;
 use futures_util::{SinkExt, StreamExt};
 use maestro_protocol::{
     routes, ApiError, CatalogEvent, CreateSessionRequest, DaemonClient, DaemonInfo, DirListing,
-    GitRoot, RecentDirs, Session, SessionStatus, PROTOCOL_VERSION,
+    GitRoot, RecentDirs, SendInputRequest, Session, SessionStatus, PROTOCOL_VERSION,
 };
 use tokio::net::TcpListener;
 use tokio::sync::{broadcast, oneshot};
@@ -55,6 +55,8 @@ struct Inner {
     info: Option<DaemonInfo>,
     /// When set, every route answers with this instead of its normal response.
     forced_error: Option<(u16, ApiError)>,
+    /// Everything `POST /api/sessions/:id/input` was asked to type, in order.
+    inputs: Vec<(Uuid, SendInputRequest)>,
 }
 
 #[derive(Clone)]
@@ -86,6 +88,7 @@ impl MockDaemon {
         let app = Router::new()
             .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::INFO, get(daemon_info))
             .route(routes::DIRS, get(list_dir))
             .route(routes::RECENT_DIRS, get(recent_dirs))
@@ -167,6 +170,11 @@ impl MockDaemon {
         self.state.inner.lock().expect("poisoned").forced_error = None;
     }
 
+    /// Every `send` this daemon received, oldest first.
+    pub fn inputs(&self) -> Vec<(Uuid, SendInputRequest)> {
+        self.state.inner.lock().expect("poisoned").inputs.clone()
+    }
+
     pub fn session_count(&self) -> usize {
         self.state.inner.lock().expect("poisoned").sessions.len()
     }
@@ -233,6 +241,28 @@ async fn kill_session(State(s): State<AppState>, Path(id): Path<Uuid>) -> Respon
     StatusCode::NO_CONTENT.into_response()
 }
 
+/// Records the text instead of typing it — the subject under test is the
+/// client's request, not tmux.
+async fn send_input(
+    State(s): State<AppState>,
+    Path(id): Path<Uuid>,
+    Json(req): Json<SendInputRequest>,
+) -> 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.inputs.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/src/main.rs

@@ -57,6 +57,10 @@ enum Command {
     /// Kill a session by ID.
     #[cfg(feature = "cli")]
     Kill(maestro_cli::cli::KillArgs),
+    /// Type text into a running session, as if it had been typed on an
+    /// attached terminal.
+    #[cfg(feature = "cli")]
+    Send(maestro_cli::cli::SendArgs),
     /// Install or update the agent activity hook (#106).
     #[cfg(feature = "cli")]
     Hooks(maestro_cli::cli::HooksArgs),
@@ -144,6 +148,15 @@ async fn dispatch(cli: Cli) -> Result<(), Box<dyn std::error::Error>> {
             .await?
         }
         #[cfg(feature = "cli")]
+        Command::Send(args) => {
+            maestro_cli::dispatch(
+                maestro_cli::cli::Command::Send(args),
+                cli.config,
+                cli.daemon_url,
+            )
+            .await?
+        }
+        #[cfg(feature = "cli")]
         Command::Hooks(args) => {
             maestro_cli::dispatch(
                 maestro_cli::cli::Command::Hooks(args),
@@ -190,6 +203,7 @@ fn is_cli_subcommand(command: &Option<Command>) -> bool {
             | Some(Command::Spawn(_))
             | Some(Command::Attach(_))
             | Some(Command::Kill(_))
+            | Some(Command::Send(_))
             | Some(Command::Hooks(_))
     )
 }