diff --git a/AGENTS.md b/AGENTS.md
index 539a784..7e50fa6 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -28,14 +28,27 @@ Single-file Python application for managing LXST Channel connections via Reticul
 
 ## Whisplay GUI Controls
 
+  ### Channel list (STATE_READY)
+
   Short press (<1s)     Cycle to next channel in list
   Long press (>=1s)     Call the selected channel
-  Press (while in call) Hang up
 
-  RGB LED indicates state:
+  ### In call (STATE_IN_CALL) — Push-to-Talk mode (default)
+
+  Press & hold           Talk (unmute microphone)
+  Release                Stop talking (mute microphone)
+  Double-press           Toggle to always-on mode
+
+  ### In call — Always-on mode (toggled)
+
+  Press                  Hang up
+  Double-press           Toggle to push-to-talk mode
+
+  ### RGB LED indicates state:
     Blue   = ready, showing channels
     Orange = calling
     Green  = in call
+    Yellow = transmitting (PTT mode, mic active)
 
 ## Initial Setup Order
 
diff --git a/client.py b/client.py
index a9e37bb..62e8a25 100644
--- a/client.py
+++ b/client.py
@@ -36,6 +36,7 @@ if _WHISPLAY_AVAILABLE:
         pass
 
 LONG_PRESS_THRESHOLD = 1.0
+DOUBLE_PRESS_THRESHOLD = 0.4
 
 
 class Terminal:
@@ -71,6 +72,10 @@ class ChannelClient:
         self.selected_index = 0
         self._press_time = 0.0
         self._wm8960_device = None
+        self._ptt_enabled = True
+        self._ptt_active = False
+        self._last_release_time = 0.0
+        self._double_pressed = False
         if use_whisplay and _WHISPLAY_AVAILABLE and _HAS_PIL:
             try:
                 self._init_whisplay()
@@ -304,8 +309,13 @@ class ChannelClient:
         lines = [f"Channel {self.selected_index + 1}"]
         if ch:
             lines.append(ch["hash"][:16] + "..")
-        lines += ["", "Press to hang up"]
-        fb = self._render("In Call", lines, accent=(60, 220, 120), footer="Press button to end")
+        if self._ptt_enabled:
+            lines += ["", "PTT: hold to talk", "Release to mute"]
+            footer = "Double-press: toggle"
+        else:
+            lines += ["", "Mic always-on", "Press to hang up"]
+            footer = "Double-press: toggle"
+        fb = self._render("In Call", lines, accent=(60, 220, 120), footer=footer)
         self.board.draw_image(0, 0, self.board.LCD_WIDTH, self.board.LCD_HEIGHT, fb)
 
     def _show_status(self, title, detail="", accent=(255, 180, 60)):
@@ -317,14 +327,41 @@ class ChannelClient:
 
     def _on_button_press(self):
         self._press_time = time.time()
+        if self.state == self.STATE_IN_CALL:
+            if time.time() - self._last_release_time < DOUBLE_PRESS_THRESHOLD:
+                self._double_pressed = True
+                self._ptt_enabled = not self._ptt_enabled
+                if self._ptt_enabled:
+                    self.telephone.mute_transmit()
+                else:
+                    self.telephone.unmute_transmit()
+                if self.board:
+                    self._show_in_call()
+                return
+            if self._ptt_enabled:
+                self._ptt_active = True
+                self.telephone.unmute_transmit()
+                if self.board:
+                    self.board.set_rgb(255, 255, 0)
 
     def _on_button_release(self):
-        elapsed = time.time() - self._press_time
+        self._last_release_time = time.time()
         if self.state == self.STATE_IN_CALL:
-            self.telephone.hangup()
-            return
+            if self._double_pressed:
+                self._double_pressed = False
+                return
+            if self._ptt_enabled:
+                self._ptt_active = False
+                self.telephone.mute_transmit()
+                if self.board:
+                    self.board.set_rgb(0, 255, 80)
+                return
+            else:
+                self.telephone.hangup()
+                return
         if self.state != self.STATE_READY:
             return
+        elapsed = time.time() - self._press_time
         if elapsed >= LONG_PRESS_THRESHOLD:
             if self.channels:
                 self.board.set_rgb(255, 180, 0)
@@ -457,6 +494,8 @@ class ChannelClient:
             f"\nCall established with "
             f"{RNS.prettyhexrep(remote_identity.hash)}"
         )
+        if self._ptt_enabled:
+            self.telephone.mute_transmit()
         if self.board:
             self.board.set_rgb(0, 255, 80)
             self._show_in_call()
@@ -465,6 +504,8 @@ class ChannelClient:
         was_in_call = self.state == self.STATE_IN_CALL
         was_calling = self.state == self.STATE_CALLING
         self.state = self.STATE_READY
+        self._ptt_active = False
+        self._double_pressed = False
         if was_in_call:
             print(f"\nCall ended")
         elif was_calling: