diff --git a/src/behaviour_hello.py b/src/behaviour_hello.py
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+++ b/src/behaviour_hello.py
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+"""
+
+Behaviour node.
+
+When a face shows up on the camera, the robot says "Hello" through a .wav file.
+
+Also, when the face moves, the robot's head turns and follows it.
+
+"""
+
+import time
+import cv2
+import middleware as mw
+import threading
+
+
+COOLDOWN = 8.0
+CONFIRM_FRAMES = 3
+ABSENT_FRAMES = 3
+FRAME_W = 640
+FRAME_H = 480
+
+EYES_OPENED = 1
+EYES_CLOSED = 3
+
+VIDEO_MAP = {
+    EYES_OPENED: ("open_hello_open.mp4", 5.3),
+    EYES_CLOSED: ("dark_hello_open.mp4", 5.2),
+}
+
+
+class BehaviourHello:
+    """
+    Middleware behaviour that greets detected faces and tracks them with the robot's head.
+    Captures frames from an MJPEG stream, runs YuNet face detection, plays a greeting
+    sound on first detection (with a cooldown), and servo-tracks the face using pan/tilt.
+    Pauses automatically when the photographer behaviour is active.
+
+    > ## Attributes
+
+    ``speakers : mw.Speakers`` : Middleware speaker controller for playing greeting sounds.
+
+    ``behaviours : mw.Behaviours`` : Middleware behaviour configuration flags, used to check photographer state.
+
+    ``server : mw.Server`` : Middleware server helper for resolving image and sound resource URLs.
+
+    ``node : mw.Node`` : Middleware node used for logging and shutdown signalling.
+
+    ``pan : mw.Pan`` : Middleware pan servo controller for horizontal head movement.
+
+    ``tilt : mw.Tilt`` : Middleware tilt servo controller for vertical head movement.
+
+    ``detector : cv2.FaceDetectorYN`` : YuNet ONNX face detector configured for FRAME_W x FRAME_H input.
+
+    ``stream : cv2.VideoCapture`` : MJPEG video capture connected to the local camera stream.
+
+    ``latest_frame : numpy.ndarray or None`` : Most recent frame captured by the reader thread; None until first frame arrives.
+
+    ``onboard : mw.Onboard`` : Middleware onboard display controller for showing reaction images.
+
+    ``lock : threading.Lock`` : Mutex protecting access to latest_frame between the reader thread and main loop.
+
+    ``running : bool`` : Flag used to signal the reader thread to stop when the behaviour shuts down.
+
+    ``video_urls : dict`` : Pre-resolved URLs for each hello transition video, keyed by eye state.
+
+    ``video_durations : dict`` : Durations in seconds for each video, keyed by eye state.
+
+    ``smooth_cx : float`` : Exponentially smoothed horizontal face centre position (set on first track call).
+
+    ``smooth_cy : float`` : Exponentially smoothed vertical face centre position (set on first track call).
+
+    > ## Functions
+    """
+
+    def __init__(self):
+        self.speakers = mw.Speakers()
+        self.behaviours = mw.Behaviours()
+        self.server = mw.Server()
+        self.node = mw.Node("behaviour_hello")
+        self.pan = mw.Pan()
+        self.tilt = mw.Tilt()
+        self.onboard = mw.Onboard()
+        self.detector = cv2.FaceDetectorYN.create(
+            "/home/idmind/elmo-v2/src/yunet.onnx", "", (FRAME_W, FRAME_H)
+        )
+        self.stream = cv2.VideoCapture("http://localhost:8080/stream.mjpg")
+        self.latest_frame = None
+        self.lock = threading.Lock()
+        self.running = True
+        self.smooth_cx = None
+        self.smooth_cy = None
+
+        self.video_urls = {}
+        self.video_durations = {}
+        for eye_state, (filename, duration) in VIDEO_MAP.items():
+            self.video_urls[eye_state] = self.server.url_for_video(filename)
+            self.video_durations[eye_state] = duration
+
+        t = threading.Thread(target=self.reader, daemon=True)
+        t.start()
+        time.sleep(2)
+        self.node.loginfo("Camera ready.")
+
+    def reader(self):
+        """
+        Background thread target that continuously reads frames from the MJPEG stream
+        and stores the latest one for use by the detection loop.
+
+        Runs until ``self.running`` is set to False. Failed reads are silently skipped.
+
+        Parameters
+        ----------
+        None
+
+        Returns
+        -------
+        None
+        """
+        while self.running:
+            ret, frame = self.stream.read()
+            if ret:
+                with self.lock:
+                    self.latest_frame = frame
+
+    def detect_face(self):
+        """
+        Grab the latest frame and run YuNet face detection on it.
+
+        Only the highest-confidence (first) detected face is considered.
+        Returns the pixel coordinates of its centre.
+
+        Parameters
+        ----------
+        None
+
+        Returns
+        -------
+        detected : bool
+            True if at least one face was found in the latest frame, False otherwise.
+        cx : float or None
+            Horizontal pixel position of the face centre; None when no face is detected.
+        cy : float or None
+            Vertical pixel position of the face centre; None when no face is detected.
+        """
+        with self.lock:
+            frame = self.latest_frame
+        if frame is None:
+            return False, None, None
+        _, faces = self.detector.detect(frame)
+        if faces is None or len(faces) == 0:
+            return False, None, None
+        x, y, w, h = faces[0][:4]
+        cx = x + w / 2
+        cy = y + h / 2
+        return True, cx, cy
+
+    def track_face(self, cx, cy):
+        """
+        Update pan and tilt servo targets to keep the detected face centred in frame.
+
+        Applies exponential smoothing (alpha=0.4) to the raw face position before
+        computing the tracking error. Alpha is the smoothing factor for the exponential
+        moving average applied to the raw face position. With alpha = 0.4, each new frame
+        contributes 40% to the smoothed position, while the previous 60% carries over.
+        This means:
+        - Higher alpha (→ 1.0) — tracks faster, but jittery; the servos react sharply to
+        every detected position twitch.
+        - Lower alpha (→ 0.0) — very smooth, but sluggish; the servos lag behind a moving
+        face.
+        A dead-band of ±8 % of frame width/height suppresses small jitter. The resulting
+        angle adjustments are clamped to each servo's hardware limits before being written.
+
+        Parameters
+        ----------
+        cx : float
+            Horizontal pixel position of the face centre in the current frame.
+        cy : float
+            Vertical pixel position of the face centre in the current frame.
+
+        Returns
+        -------
+        None
+        """
+        alpha = 0.4
+        if self.smooth_cx is None:
+            self.smooth_cx = float(cx)
+            self.smooth_cy = float(cy)
+        self.smooth_cx = alpha * float(cx) + (1 - alpha) * self.smooth_cx
+        self.smooth_cy = alpha * float(cy) + (1 - alpha) * self.smooth_cy
+
+        error_x = (self.smooth_cx - FRAME_W / 2) / FRAME_W
+        error_y = (self.smooth_cy - FRAME_H / 2) / FRAME_H
+
+        if abs(error_x) < 0.08:
+            error_x = 0
+        if abs(error_y) < 0.08:
+            error_y = 0
+
+        pan_adjust = -error_x * 80
+        tilt_adjust = error_y * 60
+
+        new_pan = float(self.pan.current_angle) + pan_adjust
+        new_tilt = float(self.tilt.current_angle) + tilt_adjust
+
+        new_pan = max(self.pan.min_angle, min(self.pan.max_angle, new_pan))
+        new_tilt = max(self.tilt.min_angle, min(self.tilt.max_angle, new_tilt))
+
+        self.pan.angle = new_pan
+        self.tilt.angle = new_tilt
+
+    def sleep_mode_state(self):
+        """
+        Read the current eye state from sleep_mode's Redis semaphore.
+
+        Returns
+        -------
+        int
+            EYES_OPENED (1) or EYES_CLOSED (3).
+            Defaults to EYES_OPENED if the key is missing or unreadable.
+        """
+        try:
+            return int(mw.get_key("sleep_mode_eye_state"))
+        except (TypeError, ValueError):
+            return EYES_OPENED
+
+    def hello(self):
+        """
+        Execute the greeting animation.
+
+        Reads sleep_mode_eye_state to pick the correct transition video.
+        Sets behaviour_hello_active so sleep_mode yields the display,
+        plays the video and greeting sound, then restores open.png.
+        Signals sleep_mode_last_interaction on completion.
+        """
+        sounds = ["hello.wav", "hello2.wav", "hello3.wav"]
+        chosen = sounds[int(time.time()) % len(sounds)]
+        mw.set_key("behaviour_hello_active", True)
+        self.onboard.video = self.video_urls[self.sleep_mode_state()]
+        self.node.loginfo(f"Face detected - playing {chosen}")
+        self.speakers.url = self.server.url_for_sound(chosen)
+        time.sleep(self.video_durations[self.sleep_mode_state()])
+        self.onboard.image = self.server.url_for_image("open.png")
+        mw.set_key("behaviour_hello_active", False)
+        mw.set_key("sleep_mode_last_interaction", time.time())
+
+    def run(self):
+        """
+        Main behaviour loop.
+
+        Enables pan and tilt servos, then polls the camera at ~10 Hz. On each tick:
+        - Skips processing if the photographer behaviour is active.
+        - Accumulates consecutive detection frames; after CONFIRM_FRAMES a face is
+        considered present and a greeting sound is played (subject to COOLDOWN).
+        - Calls track_face() every tick while a face is confirmed present.
+        - After ABSENT_FRAMES consecutive misses the face is considered gone.
+
+        Releases the video stream and shuts down the middleware node on exit (including
+        on KeyboardInterrupt or any other exception).
+
+        Parameters
+        ----------
+        None
+
+        Returns
+        -------
+        None
+        """
+        self.node.loginfo("Behaviour started.")
+        face_detected = False
+        last_greeted = 0
+        consecutive = 0
+        absent = 0
+
+        # enable motors on startup
+        self.pan.enable = True
+        self.tilt.enable = True
+
+        try:
+            while not self.node.is_shutdown():
+                time.sleep(0.1)
+                now = time.time()
+
+                # pause when photographer is active
+                if self.behaviours.photographer:
+                    face_detected = False
+                    consecutive = 0
+                    time.sleep(0.5)
+                    continue
+
+                detected, cx, cy = self.detect_face()
+
+                if detected:
+                    consecutive += 1
+                    absent = 0
+                    if consecutive >= CONFIRM_FRAMES and not face_detected:
+                        face_detected = True
+                        if now - last_greeted > COOLDOWN:
+                            self.node.loginfo("Face detected.")
+                            self.hello()
+                            last_greeted = now
+                    if face_detected:
+                        self.track_face(cx, cy)
+                else:
+                    absent += 1
+                    consecutive = 0
+                    if absent >= ABSENT_FRAMES and face_detected:
+                        self.node.loginfo("Face gone.")
+                        face_detected = False
+        finally:
+            mw.set_key("behaviour_hello_active", False)
+            self.running = False
+            self.stream.release()
+            self.node.shutdown()
+
+
+if __name__ == "__main__":
+    node = BehaviourHello()
+    node.run()
diff --git a/src/static/sounds/hello.wav b/src/static/sounds/hello.wav
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diff --git a/src/static/sounds/hello3.wav b/src/static/sounds/hello3.wav
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diff --git a/src/static/videos/dark_hello_open.mp4 b/src/static/videos/dark_hello_open.mp4
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diff --git a/src/static/videos/open_hello_open.mp4 b/src/static/videos/open_hello_open.mp4
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