diff --git a/server-client.c b/server-client.c
index 241e1bed..89a4faa6 100644
--- a/server-client.c
+++ b/server-client.c
@@ -491,6 +491,8 @@ server_client_loop(void)
 	struct window_pane	*wp;
 	u_int		 	 i;
 
+	int tmate_should_sync_layout = 0;
+
 	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
 		c = ARRAY_ITEM(&clients, i);
 		if (c == NULL)
@@ -513,7 +515,7 @@ server_client_loop(void)
 			continue;
 
 		if (w->flags & WINDOW_REDRAW)
-			tmate_sync_window(w);
+			tmate_should_sync_layout = 1;
 
 		w->flags &= ~WINDOW_REDRAW;
 		TAILQ_FOREACH(wp, &w->panes, entry) {
@@ -522,6 +524,9 @@ server_client_loop(void)
 			wp->flags &= ~PANE_REDRAW;
 		}
 	}
+
+	if (tmate_should_sync_layout)
+		tmate_sync_layout();
 }
 
 /* Check if pane should be resized. */
diff --git a/session.c b/session.c
index d3d82ea2..ebe1178d 100644
--- a/session.c
+++ b/session.c
@@ -91,10 +91,12 @@ session_create(const char *name, const char *cmd, const char *cwd,
 {
 	struct session	*s;
 
+#ifdef TMATE
 	if (next_session_id != 0) {
 		xasprintf(cause, "multi sessions is not supported with tmate");
 		return NULL;
 	}
+#endif
 
 	s = xmalloc(sizeof *s);
 	s->references = 0;
@@ -270,6 +272,11 @@ session_new(struct session *s,
 		options_set_number(&w->options, "remain-on-exit", 1);
 
 	session_group_synchronize_from(s);
+
+#ifdef TMATE
+	tmate_sync_layout();
+#endif
+
 	return (wl);
 }
 
@@ -423,6 +430,11 @@ session_set_current(struct session *s, struct winlink *wl)
 	winlink_stack_push(&s->lastw, s->curw);
 	s->curw = wl;
 	winlink_clear_flags(wl);
+
+#ifdef TMATE
+	tmate_sync_layout();
+#endif
+
 	return (0);
 }
 
diff --git a/tmate-encoder.c b/tmate-encoder.c
index 976edc36..57f6c110 100644
--- a/tmate-encoder.c
+++ b/tmate-encoder.c
@@ -35,36 +35,81 @@ void tmate_write_header(void)
 	pack(int, TMATE_PROTOCOL_VERSION);
 }
 
-void tmate_sync_window(struct window *w)
+void tmate_sync_layout(void)
 {
+	struct session *s;
+	struct winlink *wl;
+	struct window *w;
 	struct window_pane *wp;
 	int num_panes = 0;
+	int num_windows = 0;
 	int active_pane_id = -1;
+	int active_window_id = -1;
 
-	pack(array, 7);
-	pack(int, TMATE_SYNC_WINDOW);
+	/*
+	 * We only allow one session, it makes our lives easier.
+	 * Especially when the HTML5 client will come along.
+	 * We make no distinction between a winlink and its window.
+	 * TODO send the winlink in the current session stack order.
+	 */
 
-	pack(int, w->id);
-	pack(string, w->name);
-	pack(int, w->sx);
-	pack(int, w->sy);
+	s = RB_MIN(sessions, &sessions);
+	if (!s)
+		return;
 
-	TAILQ_FOREACH(wp, &w->panes, entry)
-		num_panes++;
-
-	pack(array, num_panes);
-	TAILQ_FOREACH(wp, &w->panes, entry) {
-		pack(array, 5);
-		pack(int, wp->id);
-		pack(int, wp->sx);
-		pack(int, wp->sy);
-		pack(int, wp->xoff);
-		pack(int, wp->yoff);
-
-		if (wp == w->active)
-			active_pane_id = wp->id;
+	num_windows = 0;
+	RB_FOREACH(wl, winlinks, &s->windows) {
+		if (wl->window)
+			num_windows++;
 	}
-	pack(int, active_pane_id);
+
+	if (!num_windows)
+		return;
+
+	pack(array, 5);
+	pack(int, TMATE_SYNC_LAYOUT);
+
+	pack(int, s->sx);
+	pack(int, s->sy);
+
+	pack(array, num_windows);
+	RB_FOREACH(wl, winlinks, &s->windows) {
+		w = wl->window;
+		if (!w)
+			continue;
+
+		pack(array, 4);
+		pack(int, w->id);
+		pack(string, w->name);
+
+		num_panes = 0;
+		TAILQ_FOREACH(wp, &w->panes, entry)
+			num_panes++;
+
+		pack(array, num_panes);
+		TAILQ_FOREACH(wp, &w->panes, entry) {
+			pack(array, 5);
+			pack(int, wp->id);
+			pack(int, wp->sx);
+			pack(int, wp->sy);
+			pack(int, wp->xoff);
+			pack(int, wp->yoff);
+
+			if (wp == w->active)
+				active_pane_id = wp->id;
+		}
+		pack(int, active_pane_id);
+
+		if (wl == s->curw)
+			active_window_id = w->id;
+	}
+
+	if (active_window_id == -1) {
+		wl = RB_MIN(winlinks, &s->windows);
+		active_window_id = wl->window->id;
+	}
+
+	pack(int, active_window_id);
 }
 
 void tmate_pty_data(struct window_pane *wp, const char *buf, size_t len)
diff --git a/tmate.h b/tmate.h
index 3acabed4..7a07facd 100644
--- a/tmate.h
+++ b/tmate.h
@@ -20,7 +20,7 @@
 
 enum tmate_commands {
 	TMATE_HEADER,
-	TMATE_SYNC_WINDOW,
+	TMATE_SYNC_LAYOUT,
 	TMATE_PTY_DATA,
 	TMATE_CMD,
 	TMATE_STATUS,
@@ -35,7 +35,7 @@ struct tmate_encoder {
 extern void tmate_encoder_init(struct tmate_encoder *encoder);
 
 extern void tmate_write_header(void);
-extern void tmate_sync_window(struct window *w);
+extern void tmate_sync_layout(void);
 extern void tmate_pty_data(struct window_pane *wp, const char *buf, size_t len);
 extern int tmate_should_replicate_cmd(const struct cmd_entry *cmd);
 extern void tmate_cmd(const char *cmd);
diff --git a/window.c b/window.c
index f4bccadb..10629042 100644
--- a/window.c
+++ b/window.c
@@ -329,8 +329,6 @@ window_create(const char *name, const char *cmd, const char *shell,
 	} else
 		w->name = default_window_name(w);
 
-	tmate_sync_window(w);
-
 	return (w);
 }
 
@@ -377,7 +375,7 @@ window_set_name(struct window *w, const char *new_name)
 	free(w->name);
 	w->name = xstrdup(new_name);
 	notify_window_renamed(w);
-	tmate_sync_window(w);
+	tmate_sync_layout();
 }
 
 void