diff --git a/agor-pty/src/daemon.rs b/agor-pty/src/daemon.rs
index 502b38d..cbf9d81 100644
--- a/agor-pty/src/daemon.rs
+++ b/agor-pty/src/daemon.rs
@@ -314,7 +314,9 @@ async fn handle_message(
             let mut st = state.lock().await;
             match st.sessions.get_mut(&session_id) {
                 Some(sess) => {
-                    sess.note_resize(cols, rows);
+                    if let Err(e) = sess.resize(cols, rows).await {
+                        log::warn!("resize {session_id}: {e}");
+                    }
                 }
                 None => {
                     let _ = out_tx.try_send(DaemonMessage::Error {
diff --git a/agor-pty/src/session.rs b/agor-pty/src/session.rs
index 0529c94..9abbe2a 100644
--- a/agor-pty/src/session.rs
+++ b/agor-pty/src/session.rs
@@ -4,7 +4,7 @@ use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
 use std::time::{SystemTime, UNIX_EPOCH};
 
-use portable_pty::{native_pty_system, CommandBuilder, PtySize};
+use portable_pty::{native_pty_system, CommandBuilder, MasterPty, PtySize};
 use tokio::sync::{broadcast, Mutex};
 
 use crate::protocol::SessionInfo;
@@ -12,9 +12,6 @@ use crate::protocol::SessionInfo;
 const OUTPUT_CHANNEL_CAP: usize = 256;
 
 /// A live (or recently exited) PTY session.
-///
-/// All fields that cross await points are either `Send + Sync` or wrapped in
-/// `Arc<Mutex<_>>` so the Session itself is `Send`.
 pub struct Session {
     pub id: String,
     pub pid: u32,
@@ -23,14 +20,11 @@ pub struct Session {
     pub cols: u16,
     pub rows: u16,
     pub created_at: u64,
-    /// Used to write input into the PTY master. `Box<dyn Write + Send>`.
     writer: Arc<Mutex<Box<dyn IoWrite + Send>>>,
-    /// Broadcast channel — all subscribers receive raw output chunks.
+    /// Master PTY handle — needed for resize (TIOCSWINSZ).
+    master: Arc<Mutex<Box<dyn MasterPty + Send>>>,
     pub tx: broadcast::Sender<Vec<u8>>,
-    /// false once the child process exits.
     pub alive: Arc<AtomicBool>,
-    /// Last known exit code (set by the reader task on child exit).
-    /// Public for callers that poll exit state after SessionClosed is received.
     #[allow(dead_code)]
     pub exit_code: Arc<Mutex<Option<i32>>>,
 }
@@ -57,11 +51,14 @@ impl Session {
             .map_err(|e| format!("PTY write for {}: {e}", self.id))
     }
 
-    /// Update cached dimensions after a resize. The actual TIOCSWINSZ is issued
-    /// by the daemon before calling this.
-    pub fn note_resize(&mut self, cols: u16, rows: u16) {
+    /// Resize the PTY (issues TIOCSWINSZ) and update cached dimensions.
+    pub async fn resize(&mut self, cols: u16, rows: u16) -> Result<(), String> {
+        let master = self.master.lock().await;
+        master.resize(PtySize { rows, cols, pixel_width: 0, pixel_height: 0 })
+            .map_err(|e| format!("PTY resize for {}: {e}", self.id))?;
         self.cols = cols;
         self.rows = rows;
+        Ok(())
     }
 
     /// Return a new receiver subscribed to this session's broadcast output.
@@ -157,13 +154,15 @@ impl SessionManager {
         let alive = Arc::new(AtomicBool::new(true));
         let exit_code = Arc::new(Mutex::new(None::<i32>));
 
-        // Spawn the blocking reader task. It takes ownership of `pair.master`
-        // (via `_master`) so the PTY file descriptor stays open.
+        // Keep a reference to the master for resize operations.
+        // The reader task gets the master handle to keep the PTY fd alive.
+        let master_for_session: Box<dyn MasterPty + Send> = pair.master;
+
+        // Spawn the blocking reader task.
         let tx_clone = tx.clone();
         let alive_clone = alive.clone();
         let exit_code_clone = exit_code.clone();
         let id_clone = id.clone();
-        let _master = pair.master; // keep PTY fd alive inside the task
         tokio::task::spawn_blocking(move || {
             read_pty_output(
                 reader,
@@ -173,7 +172,6 @@ impl SessionManager {
                 id_clone,
                 on_exit,
                 child,
-                _master,
             );
         });
 
@@ -186,6 +184,7 @@ impl SessionManager {
             rows,
             created_at: unix_now(),
             writer: Arc::new(Mutex::new(writer)),
+            master: Arc::new(Mutex::new(master_for_session)),
             tx,
             alive,
             exit_code,
@@ -244,7 +243,6 @@ fn read_pty_output(
     id: String,
     on_exit: impl FnOnce(String, Option<i32>),
     mut child: Box<dyn portable_pty::Child + Send>,
-    _master: Box<dyn portable_pty::MasterPty + Send>,
 ) {
     let mut buf = [0u8; 4096];
     loop {