5 files changed, 32 insertions, 12 deletions

diff --git a/internal/net/conn.go b/internal/net/conn.go
index ca40354..a4be83a 100644
--- a/internal/net/conn.go
+++ b/internal/net/conn.go
@@ -23,6 +23,10 @@ type Conn interface {
 	// instead of a hung writer goroutine. Implementations without deadline
 	// support return nil (deadlines are best-effort).
 	SetWriteDeadline(t time.Time) error
+	// SetReadDeadline is the read-side counterpart: transports implement it so
+	// a silent peer cannot pin a goroutine and a connection slot forever.
+	// Implementations without deadline support return nil.
+	SetReadDeadline(t time.Time) error
 	SetEcho(bool) error
 }
 
@@ -114,6 +118,10 @@ func (t *tcpConn) SetWriteDeadline(ts time.Time) error {
 	return t.conn.SetWriteDeadline(ts)
 }
 
+func (t *tcpConn) SetReadDeadline(ts time.Time) error {
+	return t.conn.SetReadDeadline(ts)
+}
+
 func (t *tcpConn) Close() error {
 	return t.conn.Close()
 }
diff --git a/internal/net/remote_host_test.go b/internal/net/remote_host_test.go
index 690e758..bfd10f5 100644
--- a/internal/net/remote_host_test.go
+++ b/internal/net/remote_host_test.go
@@ -13,6 +13,7 @@ func (c remoteAddrConn) ReadMessage() (string, error)     { return "", nil }
 func (c remoteAddrConn) Write(b []byte) (int, error)      { return len(b), nil }
 func (c remoteAddrConn) Close() error                     { return nil }
 func (c remoteAddrConn) SetWriteDeadline(time.Time) error { return nil }
+func (c remoteAddrConn) SetReadDeadline(time.Time) error  { return nil }
 func (c remoteAddrConn) SetEcho(bool) error               { return nil }
 func (c remoteAddrConn) RemoteAddr() string               { return c.addr }
 
diff --git a/internal/net/server.go b/internal/net/server.go
index 6367419..71e34c8 100644
--- a/internal/net/server.go
+++ b/internal/net/server.go
@@ -331,17 +331,11 @@ func sessionIdleTimeout(sess *Session) time.Duration {
 	}
 }
 
-// armReadDeadline sets an idle read deadline on the session's transport when
-// it supports one. tcpConn and wsConn (both in this package) expose their
-// underlying connection, so telnet, telnet-TLS, and websocket are all covered.
+// armReadDeadline sets an idle read deadline on the session's transport. The
+// Conn interface requires SetReadDeadline, so every transport (telnet,
+// telnet-TLS, websocket) is covered and a new one cannot silently miss it.
 func armReadDeadline(sess *Session, d time.Duration) {
-	deadline := time.Now().Add(d)
-	switch c := sess.Conn.(type) {
-	case *tcpConn:
-		_ = c.conn.SetReadDeadline(deadline)
-	case *wsConn:
-		_ = c.conn.SetReadDeadline(deadline)
-	}
+	_ = sess.Conn.SetReadDeadline(time.Now().Add(d))
 }
 
 // StartWriter puts the session into queued mode: writes are enqueued and a
@@ -559,8 +553,11 @@ func (h *Hub) LeaveRoom(s *Session) {
 }
 
 func (h *Hub) leaveRoomLocked(s *Session) {
-	for _, room := range h.rooms {
+	for id, room := range h.rooms {
 		delete(room, s)
+		if len(room) == 0 {
+			delete(h.rooms, id)
+		}
 	}
 }
 
@@ -582,7 +579,15 @@ func (h *Hub) RekeyRooms(idMap map[int]int) {
 		}
 	}
 	for newID, set := range moved {
-		h.rooms[newID] = set
+		if existing := h.rooms[newID]; existing != nil {
+			// Merge instead of clobbering a target bucket that exists but is
+			// not itself in idMap; assigning would drop its sessions.
+			for s := range set {
+				existing[s] = true
+			}
+		} else {
+			h.rooms[newID] = set
+		}
 	}
 }
 
diff --git a/internal/net/server_test.go b/internal/net/server_test.go
index 6a3b376..b540704 100644
--- a/internal/net/server_test.go
+++ b/internal/net/server_test.go
@@ -47,6 +47,7 @@ type testConn struct{ data []byte }
 func (c *testConn) ReadMessage() (string, error)     { return "", nil }
 func (c *testConn) Write(b []byte) (int, error)      { c.data = append(c.data, b...); return len(b), nil }
 func (c *testConn) SetWriteDeadline(time.Time) error { return nil }
+func (c *testConn) SetReadDeadline(time.Time) error  { return nil }
 
 func (c *testConn) Close() error       { return nil }
 func (c *testConn) SetEcho(bool) error { return nil }
diff --git a/internal/net/wsconn.go b/internal/net/wsconn.go
index 95f714c..e7763aa 100644
--- a/internal/net/wsconn.go
+++ b/internal/net/wsconn.go
@@ -41,6 +41,11 @@ func (w *wsConn) SetWriteDeadline(ts time.Time) error {
 	return w.conn.SetWriteDeadline(ts)
 }
 
+// SetReadDeadline delegates to the underlying websocket connection.
+func (w *wsConn) SetReadDeadline(ts time.Time) error {
+	return w.conn.SetReadDeadline(ts)
+}
+
 func (w *wsConn) Close() error {
 	return w.conn.Close()
 }