diff --git a/kitty/boss.py b/kitty/boss.py
index 9a90df410..2ca136737 100644
--- a/kitty/boss.py
+++ b/kitty/boss.py
@@ -18,7 +18,8 @@ from .keys import get_key_map, get_shortcut
 from .session import create_session
 from .tabs import SpecialWindow, TabManager
 from .utils import (
-    get_primary_selection, open_url, safe_print, set_primary_selection
+    get_primary_selection, open_url, safe_print, set_primary_selection,
+    single_instance
 )
 
 
@@ -61,9 +62,13 @@ class Boss:
         self.os_window_map = {}
         self.cursor_blinking = True
         self.shutting_down = False
+        talk_fd = getattr(single_instance, 'socket', None)
+        talk_fd = -1 if talk_fd is None else talk_fd.fileno()
         self.child_monitor = ChildMonitor(
             self.on_child_death,
-            DumpCommands(args) if args.dump_commands or args.dump_bytes else None)
+            DumpCommands(args) if args.dump_commands or args.dump_bytes else None,
+            talk_fd
+        )
         set_boss(self)
         self.current_font_size = opts.font_size
         set_font_family(opts)
@@ -88,6 +93,12 @@ class Boss:
         self.child_monitor.add_child(window.id, window.child.pid, window.child.child_fd, window.screen)
         self.window_id_map[window.id] = window
 
+    def peer_msg_received(self, msg):
+        import json
+        msg = json.loads(msg.decode('utf-8'))
+        if msg.get('cmd') == 'new_instance':
+            print(msg['args'])
+
     def on_child_death(self, window_id):
         window = self.window_id_map.pop(window_id, None)
         if window is None:
diff --git a/kitty/child-monitor.c b/kitty/child-monitor.c
index 5c1672f45..d1b786ac6 100644
--- a/kitty/child-monitor.c
+++ b/kitty/child-monitor.c
@@ -223,9 +223,6 @@ join(ChildMonitor *self) {
 #define join_doc "join() -> Wait for the I/O thread to finish"
     int ret = pthread_join(self->io_thread, NULL);
     if (ret != 0) return PyErr_SetFromErrno(PyExc_OSError);
-    if (self->talk_fd > -1) {
-        if (pthread_join(self->talk_thread, NULL) != 0) return PyErr_SetFromErrno(PyExc_OSError);
-    }
     Py_RETURN_NONE;
 }
 
@@ -341,10 +338,10 @@ parse_input(ChildMonitor *self) {
     }
 
     if (UNLIKELY(self->messages_count)) {
-        while(self->messages_count--) {
-            Message *m = self->messages + self->messages_count;
+        while(self->messages_count) {
+            Message *m = self->messages + --self->messages_count;
             call_boss(peer_msg_received, "y#", m->data, m->sz);
-            free(m->data);
+            free(m->data); m->data = NULL; m->sz = 0;
         }
     }
 
@@ -928,14 +925,13 @@ io_loop(void *data) {
 
 static inline void
 handle_peer(ChildMonitor *self, int s) {
-    size_t bufsz = 1024;
+    size_t bufsz = 0;
     char *buf = NULL;
     size_t buf_used = 0;
-    if (buf == NULL) return;
 
     while(true) {
         if (buf_used >= bufsz) {
-            bufsz *= 2;
+            bufsz = MAX(1024, bufsz) * 2;
             if (bufsz > 1024 * 1024) return;
             buf = realloc(buf, bufsz);
             if (buf == NULL) return;
@@ -951,7 +947,7 @@ handle_peer(ChildMonitor *self, int s) {
     }
     if (buf_used) {
         children_mutex(lock);
-        ensure_space_for(self, messages, Message, self->messages_count + 1, messages_capacity, 16, false);
+        ensure_space_for(self, messages, Message, self->messages_count + 1, messages_capacity, 16, true);
         Message *m = self->messages + self->messages_count++;
         m->data = buf; m->sz = buf_used;
         children_mutex(unlock);
@@ -969,7 +965,7 @@ talk_loop(void *data) {
         int peer = accept(self->talk_fd, NULL, NULL);
         if (peer == -1) {
             if (errno == EINTR) continue;
-            perror("accept() on talk socket failed!");
+            if (!self->shutting_down) perror("accept() on talk socket failed!");
             break;
         }
         handle_peer(self, peer);
diff --git a/kitty/cli.py b/kitty/cli.py
index ed77795d0..c7df4fed5 100644
--- a/kitty/cli.py
+++ b/kitty/cli.py
@@ -101,6 +101,27 @@ def option_parser():
             'Path to a file containing the startup session (tabs, windows, layout, programs)'
         )
     )
+    a(
+        '-1', '--single-instance',
+        default=False,
+        action='store_true',
+        help=_(
+            'If specified only a single instance of {0} will run. New invocations will'
+            ' instead create a new top-level window in the existing {0} instance. This'
+            ' allows {0} to share a single sprite cache on the GPU and also reduces'
+            ' startup time. You can also have groups of {0} instances by using the'
+            ' {1} option.'
+        ).format(appname, '--instance-group')
+    )
+    a(
+        '--instance-group',
+        default=None,
+        help=_(
+            'Used in combination with the --single-instance option. All {0} invocations'
+            ' with the same --instance-group will result in new windows being created'
+            ' in the first {0} instance with that group.'
+        ).format(appname)
+    )
     a(
         'args',
         nargs=argparse.REMAINDER,
diff --git a/kitty/main.py b/kitty/main.py
index fe2bd6122..e693e3ec2 100644
--- a/kitty/main.py
+++ b/kitty/main.py
@@ -23,7 +23,7 @@ from .fast_data_types import (
 from .fonts.box_drawing import set_scale
 from .utils import (
     detach, end_startup_notification, get_logical_dpi,
-    init_startup_notification
+    init_startup_notification, single_instance
 )
 from .window import load_shader_programs
 
@@ -129,6 +129,14 @@ def main():
         from kitty.client import main
         main(args.replay_commands)
         return
+    if args.single_instance:
+        is_first = single_instance(args.instance_group)
+        if not is_first:
+            import json
+            data = {'cmd': 'new_instance', 'args': tuple(sys.argv)}
+            data = json.dumps(data, ensure_ascii=False).encode('utf-8')
+            single_instance.socket.sendall(data)
+            return
     config = args.config or (defconf, )
     overrides = (a.replace('=', ' ', 1) for a in args.override or ())
     opts = load_config(*config, overrides=overrides)