diff --git a/Makefile.am b/Makefile.am
index a19a7613..f77c9abd 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -26,13 +26,15 @@ endif
 if IS_GCC
 CFLAGS += -std=c99
 if IS_DEBUG
-CFLAGS += -g -ggdb -O0
+CFLAGS += -O0 -g
 CFLAGS += -Wno-long-long -Wall -W -Wnested-externs -Wformat=2
 CFLAGS += -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations
 CFLAGS += -Wwrite-strings -Wshadow -Wpointer-arith -Wsign-compare
 CFLAGS += -Wundef -Wbad-function-cast -Winline -Wcast-align
 CFLAGS += -Wdeclaration-after-statement
 CPPFLAGS += -DDEBUG
+else
+CFLAGS += -O2
 endif
 if IS_GCC4
 CPPFLAGS += -iquote. -I/usr/local/include
diff --git a/cmd-break-pane.c b/cmd-break-pane.c
index a4350fe6..c270ca07 100644
--- a/cmd-break-pane.c
+++ b/cmd-break-pane.c
@@ -97,7 +97,7 @@ cmd_break_pane_exec(struct cmd *self, struct cmd_ctx *ctx)
 			template = BREAK_PANE_TEMPLATE;
 
 		ft = format_create();
-		if ((c = cmd_find_client(ctx, NULL)) != NULL)
+		if ((c = cmd_find_client(ctx, NULL, 1)) != NULL)
 			format_client(ft, c);
 		format_session(ft, s);
 		format_winlink(ft, s, wl);
diff --git a/cmd-command-prompt.c b/cmd-command-prompt.c
index e1db3dd4..97284898 100644
--- a/cmd-command-prompt.c
+++ b/cmd-command-prompt.c
@@ -94,7 +94,7 @@ cmd_command_prompt_exec(struct cmd *self, struct cmd_ctx *ctx)
 	char				*prompt, *ptr, *input = NULL;
 	size_t				 n;
 
-	if ((c = cmd_find_client(ctx, args_get(args, 't'))) == NULL)
+	if ((c = cmd_find_client(ctx, args_get(args, 't'), 0)) == NULL)
 		return (CMD_RETURN_ERROR);
 
 	if (c->prompt_string != NULL)
diff --git a/cmd-confirm-before.c b/cmd-confirm-before.c
index 0b41592b..30db5bd2 100644
--- a/cmd-confirm-before.c
+++ b/cmd-confirm-before.c
@@ -79,7 +79,7 @@ cmd_confirm_before_exec(struct cmd *self, struct cmd_ctx *ctx)
 		return (CMD_RETURN_ERROR);
 	}
 
-	if ((c = cmd_find_client(ctx, args_get(args, 't'))) == NULL)
+	if ((c = cmd_find_client(ctx, args_get(args, 't'), 0)) == NULL)
 		return (CMD_RETURN_ERROR);
 
 	if ((prompt = args_get(args, 'p')) != NULL)
diff --git a/cmd-detach-client.c b/cmd-detach-client.c
index f75b37a3..4b447e1a 100644
--- a/cmd-detach-client.c
+++ b/cmd-detach-client.c
@@ -61,7 +61,7 @@ cmd_detach_client_exec(struct cmd *self, struct cmd_ctx *ctx)
 				server_write_client(c, msgtype, NULL, 0);
 		}
 	} else {
-		c = cmd_find_client(ctx, args_get(args, 't'));
+		c = cmd_find_client(ctx, args_get(args, 't'), 0);
 		if (c == NULL)
 			return (CMD_RETURN_ERROR);
 
diff --git a/cmd-display-message.c b/cmd-display-message.c
index 244c557c..f0cd66c0 100644
--- a/cmd-display-message.c
+++ b/cmd-display-message.c
@@ -55,9 +55,6 @@ cmd_display_message_exec(struct cmd *self, struct cmd_ctx *ctx)
 	time_t			 t;
 	size_t			 len;
 
-	if ((c = cmd_find_client(ctx, args_get(args, 'c'))) == NULL)
-		return (CMD_RETURN_ERROR);
-
 	if (args_has(args, 't')) {
 		wl = cmd_find_pane(ctx, args_get(args, 't'), &s, &wp);
 		if (wl == NULL)
@@ -80,7 +77,8 @@ cmd_display_message_exec(struct cmd *self, struct cmd_ctx *ctx)
 		template = DISPLAY_MESSAGE_TEMPLATE;
 
 	ft = format_create();
-	format_client(ft, c);
+	if ((c = cmd_find_client(ctx, args_get(args, 'c'), 1)) != NULL)
+		format_client(ft, c);
 	format_session(ft, s);
 	format_winlink(ft, s, wl);
 	format_window_pane(ft, wp);
diff --git a/cmd-display-panes.c b/cmd-display-panes.c
index 2745ac59..dd4a333e 100644
--- a/cmd-display-panes.c
+++ b/cmd-display-panes.c
@@ -42,7 +42,7 @@ cmd_display_panes_exec(struct cmd *self, struct cmd_ctx *ctx)
 	struct args	*args = self->args;
 	struct client	*c;
 
-	if ((c = cmd_find_client(ctx, args_get(args, 't'))) == NULL)
+	if ((c = cmd_find_client(ctx, args_get(args, 't'), 0)) == NULL)
 		return (CMD_RETURN_ERROR);
 
 	server_set_identify(c);
diff --git a/cmd-lock-server.c b/cmd-lock-server.c
index db0b7dc4..4eb0b700 100644
--- a/cmd-lock-server.c
+++ b/cmd-lock-server.c
@@ -74,7 +74,7 @@ cmd_lock_server_exec(struct cmd *self, unused struct cmd_ctx *ctx)
 			return (CMD_RETURN_ERROR);
 		server_lock_session(s);
 	} else {
-		if ((c = cmd_find_client(ctx, args_get(args, 't'))) == NULL)
+		if ((c = cmd_find_client(ctx, args_get(args, 't'), 0)) == NULL)
 			return (CMD_RETURN_ERROR);
 		server_lock_client(c);
 	}
diff --git a/cmd-new-window.c b/cmd-new-window.c
index d8c576af..e50b234a 100644
--- a/cmd-new-window.c
+++ b/cmd-new-window.c
@@ -126,7 +126,7 @@ cmd_new_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 			template = NEW_WINDOW_TEMPLATE;
 
 		ft = format_create();
-		if ((c = cmd_find_client(ctx, NULL)) != NULL)
+		if ((c = cmd_find_client(ctx, NULL, 1)) != NULL)
 		    format_client(ft, c);
 		format_session(ft, s);
 		format_winlink(ft, s, wl);
diff --git a/cmd-pipe-pane.c b/cmd-pipe-pane.c
index 8f53b6ee..3c6211d9 100644
--- a/cmd-pipe-pane.c
+++ b/cmd-pipe-pane.c
@@ -56,7 +56,7 @@ cmd_pipe_pane_exec(struct cmd *self, struct cmd_ctx *ctx)
 
 	if (cmd_find_pane(ctx, args_get(args, 't'), NULL, &wp) == NULL)
 		return (CMD_RETURN_ERROR);
-	c = cmd_find_client(ctx, NULL);
+	c = cmd_find_client(ctx, NULL, 1);
 
 	/* Destroy the old pipe. */
 	old_fd = wp->pipe_fd;
diff --git a/cmd-refresh-client.c b/cmd-refresh-client.c
index 849154d9..7bec5205 100644
--- a/cmd-refresh-client.c
+++ b/cmd-refresh-client.c
@@ -44,7 +44,7 @@ cmd_refresh_client_exec(struct cmd *self, struct cmd_ctx *ctx)
 	const char	*size;
 	u_int		 w, h;
 
-	if ((c = cmd_find_client(ctx, args_get(args, 't'))) == NULL)
+	if ((c = cmd_find_client(ctx, args_get(args, 't'), 0)) == NULL)
 		return (CMD_RETURN_ERROR);
 
 	if (args_has(args, 'C')) {
diff --git a/cmd-show-messages.c b/cmd-show-messages.c
index d8c18519..728e170d 100644
--- a/cmd-show-messages.c
+++ b/cmd-show-messages.c
@@ -48,7 +48,7 @@ cmd_show_messages_exec(struct cmd *self, struct cmd_ctx *ctx)
 	char			*tim;
 	u_int			 i;
 
-	if ((c = cmd_find_client(ctx, args_get(args, 't'))) == NULL)
+	if ((c = cmd_find_client(ctx, args_get(args, 't'), 0)) == NULL)
 		return (CMD_RETURN_ERROR);
 
 	for (i = 0; i < ARRAY_LENGTH(&c->message_log); i++) {
diff --git a/cmd-split-window.c b/cmd-split-window.c
index 859d5fd1..54d5bcde 100644
--- a/cmd-split-window.c
+++ b/cmd-split-window.c
@@ -151,7 +151,7 @@ cmd_split_window_exec(struct cmd *self, struct cmd_ctx *ctx)
 			template = SPLIT_WINDOW_TEMPLATE;
 
 		ft = format_create();
-		if ((c = cmd_find_client(ctx, NULL)) != NULL)
+		if ((c = cmd_find_client(ctx, NULL, 1)) != NULL)
 		    format_client(ft, c);
 		format_session(ft, s);
 		format_winlink(ft, s, wl);
diff --git a/cmd-suspend-client.c b/cmd-suspend-client.c
index 95278f98..68affac4 100644
--- a/cmd-suspend-client.c
+++ b/cmd-suspend-client.c
@@ -45,7 +45,7 @@ cmd_suspend_client_exec(struct cmd *self, struct cmd_ctx *ctx)
 	struct args	*args = self->args;
 	struct client	*c;
 
-	if ((c = cmd_find_client(ctx, args_get(args, 't'))) == NULL)
+	if ((c = cmd_find_client(ctx, args_get(args, 't'), 0)) == NULL)
 		return (CMD_RETURN_ERROR);
 
 	tty_stop_tty(&c->tty);
diff --git a/cmd-switch-client.c b/cmd-switch-client.c
index 1ca0c41d..29a3d788 100644
--- a/cmd-switch-client.c
+++ b/cmd-switch-client.c
@@ -64,7 +64,7 @@ cmd_switch_client_exec(struct cmd *self, struct cmd_ctx *ctx)
 	struct client	*c;
 	struct session	*s;
 
-	if ((c = cmd_find_client(ctx, args_get(args, 'c'))) == NULL)
+	if ((c = cmd_find_client(ctx, args_get(args, 'c'), 0)) == NULL)
 		return (CMD_RETURN_ERROR);
 
 	if (args_has(args, 'r')) {
diff --git a/cmd.c b/cmd.c
index 5c02314f..461d39f6 100644
--- a/cmd.c
+++ b/cmd.c
@@ -516,15 +516,19 @@ cmd_choose_client(struct clients *cc)
 
 /* Find the target client or report an error and return NULL. */
 struct client *
-cmd_find_client(struct cmd_ctx *ctx, const char *arg)
+cmd_find_client(struct cmd_ctx *ctx, const char *arg, int quiet)
 {
 	struct client	*c;
 	char		*tmparg;
 	size_t		 arglen;
 
 	/* A NULL argument means the current client. */
-	if (arg == NULL)
-		return (cmd_current_client(ctx));
+	if (arg == NULL) {
+		c = cmd_current_client(ctx);
+		if (c == NULL && !quiet)
+			ctx->error(ctx, "no clients");
+		return (c);
+	}
 	tmparg = xstrdup(arg);
 
 	/* Trim a single trailing colon if any. */
@@ -536,7 +540,7 @@ cmd_find_client(struct cmd_ctx *ctx, const char *arg)
 	c = cmd_lookup_client(tmparg);
 
 	/* If no client found, report an error. */
-	if (c == NULL)
+	if (c == NULL && !quiet)
 		ctx->error(ctx, "client not found: %s", tmparg);
 
 	free(tmparg);
diff --git a/server-client.c b/server-client.c
index 3c14ff87..9ac6088b 100644
--- a/server-client.c
+++ b/server-client.c
@@ -17,6 +17,7 @@
  */
 
 #include <sys/types.h>
+#include <sys/ioctl.h>
 
 #include <event.h>
 #include <fcntl.h>
@@ -95,6 +96,8 @@ server_client_create(int fd)
 	c->tty.mouse.event = MOUSE_EVENT_UP;
 	c->tty.mouse.flags = 0;
 
+	c->flags |= CLIENT_FOCUSED;
+
 	evtimer_set(&c->repeat_timer, server_client_repeat_timer, c);
 
 	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
@@ -545,7 +548,8 @@ server_client_check_resize(struct window_pane *wp)
 void
 server_client_check_focus(struct window_pane *wp)
 {
-	struct session	*s;
+	u_int		 i;
+	struct client	*c;
 
 	/* If we don't care about focus, forget it. */
 	if (!(wp->base.mode & MODE_FOCUSON))
@@ -560,13 +564,20 @@ server_client_check_focus(struct window_pane *wp)
 		goto not_focused;
 
 	/*
-	 * If our window is the current window in any attached sessions, we're
-	 * focused.
+	 * If our window is the current window in any focused clients with an
+	 * attached session, we're focused.
 	 */
-	RB_FOREACH(s, sessions, &sessions) {
-		if (s->flags & SESSION_UNATTACHED)
+	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
+		c = ARRAY_ITEM(&clients, i);
+		if (c == NULL || c->session == NULL)
 			continue;
-		if (s->curw->window == wp->window)
+
+		if (!(c->flags & CLIENT_FOCUSED))
+			continue;
+		if (c->session->flags & SESSION_UNATTACHED)
+			continue;
+
+		if (c->session->curw->window == wp->window)
 			goto focused;
 	}
 
diff --git a/tmux.h b/tmux.h
index b80face5..966588cc 100644
--- a/tmux.h
+++ b/tmux.h
@@ -237,6 +237,9 @@ enum key_code {
 	KEYC_KP_ENTER,
 	KEYC_KP_ZERO,
 	KEYC_KP_PERIOD,
+
+	KEYC_FOCUS_IN,
+	KEYC_FOCUS_OUT,
 };
 
 /* Termcap codes. */
@@ -1316,6 +1319,7 @@ struct client {
 #define CLIENT_READONLY 0x800
 #define CLIENT_REDRAWWINDOW 0x1000
 #define CLIENT_CONTROL 0x2000
+#define CLIENT_FOCUSED 0x4000
 	int		 flags;
 
 	struct event	 identify_timer;
@@ -1728,7 +1732,7 @@ struct cmd	*cmd_parse(int, char **, char **);
 size_t		 cmd_print(struct cmd *, char *, size_t);
 struct session	*cmd_current_session(struct cmd_ctx *, int);
 struct client	*cmd_current_client(struct cmd_ctx *);
-struct client	*cmd_find_client(struct cmd_ctx *, const char *);
+struct client	*cmd_find_client(struct cmd_ctx *, const char *, int);
 struct session	*cmd_find_session(struct cmd_ctx *, const char *, int);
 struct winlink	*cmd_find_window(
 		     struct cmd_ctx *, const char *, struct session **);
diff --git a/tty-keys.c b/tty-keys.c
index 00327bb2..575920e6 100644
--- a/tty-keys.c
+++ b/tty-keys.c
@@ -174,6 +174,10 @@ const struct tty_default_key_raw tty_default_raw_keys[] = {
 	{ "\033[8@", KEYC_END|KEYC_CTRL|KEYC_SHIFT },
 	{ "\033[6@", KEYC_NPAGE|KEYC_CTRL|KEYC_SHIFT },
 	{ "\033[5@", KEYC_PPAGE|KEYC_CTRL|KEYC_SHIFT },
+
+	/* Focus tracking. */
+	{ "\033[I", KEYC_FOCUS_IN },
+	{ "\033[O", KEYC_FOCUS_OUT },
 };
 
 /* Default terminfo(5) keys. */
@@ -559,6 +563,15 @@ complete_key:
 		evtimer_del(&tty->key_timer);
 	tty->flags &= ~TTY_TIMER;
 
+	/* Check for focus events. */
+	if (key == KEYC_FOCUS_OUT) {
+		tty->client->flags &= ~CLIENT_FOCUSED;
+		return (1);
+	} else if (key == KEYC_FOCUS_IN) {
+		tty->client->flags |= CLIENT_FOCUSED;
+		return (1);
+	}
+
 	/* Fire the key. */
 	if (key != KEYC_NONE)
 		server_client_handle_key(tty->client, key);
diff --git a/tty.c b/tty.c
index b5dcf6d3..ab75d948 100644
--- a/tty.c
+++ b/tty.c
@@ -221,7 +221,7 @@ tty_start_tty(struct tty *tty)
 		tty_puts(tty, "\033[?1000l\033[?1006l\033[?1005l");
 
 	if (tty_term_has(tty->term, TTYC_XT))
-		tty_puts(tty, "\033[c\033[>4;1m\033[?1004l");
+		tty_puts(tty, "\033[c\033[>4;1m\033[?1004h");
 
 	tty->cx = UINT_MAX;
 	tty->cy = UINT_MAX;
@@ -284,7 +284,7 @@ tty_stop_tty(struct tty *tty)
 		tty_raw(tty, "\033[?1000l\033[?1006l\033[?1005l");
 
 	if (tty_term_has(tty->term, TTYC_XT))
-		tty_raw(tty, "\033[>4m");
+		tty_raw(tty, "\033[>4m\033[?1004l");
 
 	tty_raw(tty, tty_term_string(tty->term, TTYC_RMCUP));