diff --git a/jetson/ros2_ws/src/saltybot_social/config/personal_space_params.yaml b/jetson/ros2_ws/src/saltybot_social/config/personal_space_params.yaml
new file mode 100644
index 0000000..f8010a8
--- /dev/null
+++ b/jetson/ros2_ws/src/saltybot_social/config/personal_space_params.yaml
@@ -0,0 +1,10 @@
+personal_space_node:
+  ros__parameters:
+    personal_space_m: 0.8       # Minimum comfortable distance (m)
+    backup_speed: 0.1           # Retreat linear speed (m/s, applied as -x)
+    hysteresis_m: 0.1           # Hysteresis band above threshold (m)
+    unknown_distance_m: 99.0    # Distance assumed for faces without a PersonState
+    lost_timeout_s: 1.5         # Face freshness window (s)
+    control_rate: 10.0          # Control loop / publish rate (Hz)
+    faces_topic: "/social/faces/detected"
+    states_topic: "/social/person_states"
diff --git a/jetson/ros2_ws/src/saltybot_social/launch/personal_space.launch.py b/jetson/ros2_ws/src/saltybot_social/launch/personal_space.launch.py
new file mode 100644
index 0000000..4598808
--- /dev/null
+++ b/jetson/ros2_ws/src/saltybot_social/launch/personal_space.launch.py
@@ -0,0 +1,39 @@
+"""personal_space.launch.py -- Launch personal space respector (Issue #310).
+
+Usage:
+  ros2 launch saltybot_social personal_space.launch.py
+  ros2 launch saltybot_social personal_space.launch.py personal_space_m:=1.0 backup_speed:=0.15
+"""
+
+import os
+from ament_index_python.packages import get_package_share_directory
+from launch import LaunchDescription
+from launch.actions import DeclareLaunchArgument
+from launch.substitutions import LaunchConfiguration
+from launch_ros.actions import Node
+
+
+def generate_launch_description():
+    pkg = get_package_share_directory("saltybot_social")
+    cfg = os.path.join(pkg, "config", "personal_space_params.yaml")
+
+    return LaunchDescription([
+        DeclareLaunchArgument("personal_space_m", default_value="0.8",
+                              description="Minimum comfortable distance (m)"),
+        DeclareLaunchArgument("backup_speed",     default_value="0.1",
+                              description="Retreat linear speed (m/s)"),
+
+        Node(
+            package="saltybot_social",
+            executable="personal_space_node",
+            name="personal_space_node",
+            output="screen",
+            parameters=[
+                cfg,
+                {
+                    "personal_space_m": LaunchConfiguration("personal_space_m"),
+                    "backup_speed":     LaunchConfiguration("backup_speed"),
+                },
+            ],
+        ),
+    ])
diff --git a/jetson/ros2_ws/src/saltybot_social/saltybot_social/personal_space_node.py b/jetson/ros2_ws/src/saltybot_social/saltybot_social/personal_space_node.py
new file mode 100644
index 0000000..3301066
--- /dev/null
+++ b/jetson/ros2_ws/src/saltybot_social/saltybot_social/personal_space_node.py
@@ -0,0 +1,211 @@
+"""personal_space_node.py — Personal space respector.
+Issue #310
+
+Monitors the distance to detected faces.  When the closest person
+enters within ``personal_space_m`` metres (default 0.8 m) the robot
+slowly backs up (``Twist.linear.x = -backup_speed``) and latches
+/saltybot/too_close to True.  Once the person retreats beyond
+``personal_space_m + hysteresis_m`` the robot stops and the latch clears.
+
+Distance is read from /social/person_states (PersonStateArray, face_id →
+distance).  When a face has no matching PersonState entry the distance is
+treated as ``unknown_distance_m`` (default: very large → safe, no backup).
+
+Subscriptions
+─────────────
+  /social/faces/detected    saltybot_social_msgs/FaceDetectionArray
+  /social/person_states     saltybot_social_msgs/PersonStateArray
+
+Publications
+────────────
+  /cmd_vel               geometry_msgs/Twist  — linear.x only; angular.z = 0
+  /saltybot/too_close    std_msgs/Bool        — True while backing up
+
+State machine
+─────────────
+  CLEAR     — no face within personal_space_m; publish zero Twist + False
+  TOO_CLOSE — face within personal_space_m; publish backup Twist + True
+              clears only when distance > personal_space_m + hysteresis_m
+
+Parameters
+──────────
+  personal_space_m    (float, 0.8)   minimum comfortable distance (m)
+  backup_speed        (float, 0.1)   retreat linear speed (m/s, applied as -x)
+  hysteresis_m        (float, 0.1)   hysteresis band above threshold (m)
+  unknown_distance_m  (float, 99.0)  distance assumed for faces without state
+  lost_timeout_s      (float, 1.5)   face freshness window (s)
+  control_rate        (float, 10.0)  publish rate (Hz)
+  faces_topic         (str, "/social/faces/detected")
+  states_topic        (str, "/social/person_states")
+"""
+
+from __future__ import annotations
+
+import time
+import threading
+from typing import Dict
+
+import rclpy
+from rclpy.node import Node
+from rclpy.qos import QoSProfile
+from std_msgs.msg import Bool
+from geometry_msgs.msg import Twist
+
+try:
+    from saltybot_social_msgs.msg import FaceDetectionArray, PersonStateArray
+    _MSGS = True
+except ImportError:
+    _MSGS = False
+
+
+# ── Pure helpers ───────────────────────────────────────────────────────────────
+
+def closest_face_distance(face_ids, distance_cache: Dict[int, float],
+                          unknown_distance_m: float) -> float:
+    """Return the minimum distance across all visible face_ids.
+
+    Falls back to *unknown_distance_m* for any face_id not in the cache.
+    Returns *unknown_distance_m* when *face_ids* is empty.
+    """
+    if not face_ids:
+        return unknown_distance_m
+    return min(distance_cache.get(fid, unknown_distance_m) for fid in face_ids)
+
+
+def should_backup(distance: float, personal_space_m: float) -> bool:
+    return distance <= personal_space_m
+
+
+def should_clear(distance: float, personal_space_m: float,
+                 hysteresis_m: float) -> bool:
+    return distance > personal_space_m + hysteresis_m
+
+
+# ── ROS2 node ──────────────────────────────────────────────────────────────────
+
+class PersonalSpaceNode(Node):
+    """Backs the robot away when a person enters personal space."""
+
+    def __init__(self) -> None:
+        super().__init__("personal_space_node")
+
+        self.declare_parameter("personal_space_m",   0.8)
+        self.declare_parameter("backup_speed",        0.1)
+        self.declare_parameter("hysteresis_m",        0.1)
+        self.declare_parameter("unknown_distance_m",  99.0)
+        self.declare_parameter("lost_timeout_s",      1.5)
+        self.declare_parameter("control_rate",        10.0)
+        self.declare_parameter("faces_topic",         "/social/faces/detected")
+        self.declare_parameter("states_topic",        "/social/person_states")
+
+        self._space        = self.get_parameter("personal_space_m").value
+        self._backup_speed = self.get_parameter("backup_speed").value
+        self._hysteresis   = self.get_parameter("hysteresis_m").value
+        self._unknown_dist = self.get_parameter("unknown_distance_m").value
+        self._lost_t       = self.get_parameter("lost_timeout_s").value
+        rate               = self.get_parameter("control_rate").value
+        faces_topic        = self.get_parameter("faces_topic").value
+        states_topic       = self.get_parameter("states_topic").value
+
+        # State
+        self._too_close: bool = False
+        self._distance_cache: Dict[int, float] = {}   # face_id → distance (m)
+        self._active_face_ids: list = []               # face_ids in last msg
+        self._last_face_t: float = 0.0
+        self._lock = threading.Lock()
+
+        qos = QoSProfile(depth=10)
+        self._cmd_pub       = self.create_publisher(Twist, "/cmd_vel",             qos)
+        self._too_close_pub = self.create_publisher(Bool,  "/saltybot/too_close",  qos)
+
+        if _MSGS:
+            self._states_sub = self.create_subscription(
+                PersonStateArray, states_topic, self._on_person_states, qos
+            )
+            self._faces_sub = self.create_subscription(
+                FaceDetectionArray, faces_topic, self._on_faces, qos
+            )
+        else:
+            self.get_logger().warn(
+                "saltybot_social_msgs not available — node passive"
+            )
+
+        self._timer = self.create_timer(1.0 / rate, self._control_cb)
+
+        self.get_logger().info(
+            f"PersonalSpaceNode ready "
+            f"(space={self._space}m, backup={self._backup_speed}m/s, "
+            f"hysteresis={self._hysteresis}m)"
+        )
+
+    # ── Subscription callbacks ─────────────────────────────────────────────
+
+    def _on_person_states(self, msg) -> None:
+        with self._lock:
+            for ps in msg.persons:
+                if ps.face_id >= 0:
+                    self._distance_cache[ps.face_id] = float(ps.distance)
+
+    def _on_faces(self, msg) -> None:
+        face_ids = [int(f.face_id) for f in msg.faces]
+        with self._lock:
+            self._active_face_ids = face_ids
+            if face_ids:
+                self._last_face_t = time.monotonic()
+
+    # ── Control loop ───────────────────────────────────────────────────────
+
+    def _control_cb(self) -> None:
+        now = time.monotonic()
+        with self._lock:
+            face_ids    = list(self._active_face_ids)
+            last_face_t = self._last_face_t
+            cache       = dict(self._distance_cache)
+
+        face_fresh = last_face_t > 0.0 and (now - last_face_t) < self._lost_t
+
+        if not face_fresh:
+            # No fresh face data → clear state, stop
+            if self._too_close:
+                self._too_close = False
+                self.get_logger().info("PersonalSpace: face lost — clearing")
+            self._publish(backup=False)
+            return
+
+        dist = closest_face_distance(face_ids, cache, self._unknown_dist)
+
+        if not self._too_close and should_backup(dist, self._space):
+            self._too_close = True
+            self.get_logger().warn(
+                f"PersonalSpace: TOO CLOSE ({dist:.2f}m <= {self._space}m) — backing up"
+            )
+        elif self._too_close and should_clear(dist, self._space, self._hysteresis):
+            self._too_close = False
+            self.get_logger().info(
+                f"PersonalSpace: CLEAR ({dist:.2f}m > {self._space + self._hysteresis:.2f}m)"
+            )
+
+        self._publish(backup=self._too_close)
+
+    def _publish(self, backup: bool) -> None:
+        twist = Twist()
+        if backup:
+            twist.linear.x = -self._backup_speed
+
+        bool_msg = Bool()
+        bool_msg.data = backup
+
+        self._cmd_pub.publish(twist)
+        self._too_close_pub.publish(bool_msg)
+
+
+def main(args=None) -> None:
+    rclpy.init(args=args)
+    node = PersonalSpaceNode()
+    try:
+        rclpy.spin(node)
+    except KeyboardInterrupt:
+        pass
+    finally:
+        node.destroy_node()
+        rclpy.shutdown()
diff --git a/jetson/ros2_ws/src/saltybot_social/setup.py b/jetson/ros2_ws/src/saltybot_social/setup.py
index feafc7f..b2ca025 100644
--- a/jetson/ros2_ws/src/saltybot_social/setup.py
+++ b/jetson/ros2_ws/src/saltybot_social/setup.py
@@ -55,6 +55,8 @@ setup(
             'volume_adjust_node = saltybot_social.volume_adjust_node:main',
             # Conversation topic memory (Issue #299)
             'topic_memory_node = saltybot_social.topic_memory_node:main',
+            # Personal space respector (Issue #310)
+            'personal_space_node = saltybot_social.personal_space_node:main',
         ],
     },
 )
diff --git a/jetson/ros2_ws/src/saltybot_social/test/test_personal_space.py b/jetson/ros2_ws/src/saltybot_social/test/test_personal_space.py
new file mode 100644
index 0000000..22b048b
--- /dev/null
+++ b/jetson/ros2_ws/src/saltybot_social/test/test_personal_space.py
@@ -0,0 +1,666 @@
+"""test_personal_space.py — Offline tests for personal_space_node (Issue #310).
+
+Stubs out rclpy and ROS message types so tests run without a ROS install.
+"""
+
+import importlib.util
+import sys
+import time
+import types
+import unittest
+
+
+# ── ROS2 stubs ────────────────────────────────────────────────────────────────
+
+def _make_ros_stubs():
+    for mod_name in ("rclpy", "rclpy.node", "rclpy.qos",
+                     "std_msgs", "std_msgs.msg",
+                     "geometry_msgs", "geometry_msgs.msg",
+                     "saltybot_social_msgs", "saltybot_social_msgs.msg"):
+        if mod_name not in sys.modules:
+            sys.modules[mod_name] = types.ModuleType(mod_name)
+
+    class _Node:
+        def __init__(self, name="node"):
+            self._name = name
+            if not hasattr(self, "_params"):
+                self._params = {}
+            self._pubs  = {}
+            self._subs  = {}
+            self._logs  = []
+            self._timers = []
+
+        def declare_parameter(self, name, default):
+            if name not in self._params:
+                self._params[name] = default
+
+        def get_parameter(self, name):
+            class _P:
+                def __init__(self, v): self.value = v
+            return _P(self._params.get(name))
+
+        def create_publisher(self, msg_type, topic, qos):
+            pub = _FakePub()
+            self._pubs[topic] = pub
+            return pub
+
+        def create_subscription(self, msg_type, topic, cb, qos):
+            self._subs[topic] = cb
+            return object()
+
+        def create_timer(self, period, cb):
+            self._timers.append(cb)
+            return object()
+
+        def get_logger(self):
+            node = self
+            class _L:
+                def info(self, m):  node._logs.append(("INFO",  m))
+                def warn(self, m):  node._logs.append(("WARN",  m))
+                def error(self, m): node._logs.append(("ERROR", m))
+            return _L()
+
+        def destroy_node(self): pass
+
+    class _FakePub:
+        def __init__(self):
+            self.msgs = []
+        def publish(self, msg):
+            self.msgs.append(msg)
+
+    class _QoSProfile:
+        def __init__(self, depth=10): self.depth = depth
+
+    class _Bool:
+        def __init__(self): self.data = False
+
+    class _TwistLinear:
+        def __init__(self): self.x = 0.0
+
+    class _TwistAngular:
+        def __init__(self): self.z = 0.0
+
+    class _Twist:
+        def __init__(self):
+            self.linear  = _TwistLinear()
+            self.angular = _TwistAngular()
+
+    class _FaceDetection:
+        def __init__(self, face_id=0):
+            self.face_id = face_id
+
+    class _PersonState:
+        def __init__(self, face_id=0, distance=1.0):
+            self.face_id  = face_id
+            self.distance = distance
+
+    class _FaceDetectionArray:
+        def __init__(self, faces=None):
+            self.faces = faces or []
+
+    class _PersonStateArray:
+        def __init__(self, persons=None):
+            self.persons = persons or []
+
+    rclpy_mod = sys.modules["rclpy"]
+    rclpy_mod.init     = lambda args=None: None
+    rclpy_mod.spin     = lambda node: None
+    rclpy_mod.shutdown = lambda: None
+
+    sys.modules["rclpy.node"].Node      = _Node
+    sys.modules["rclpy.qos"].QoSProfile = _QoSProfile
+    sys.modules["std_msgs.msg"].Bool    = _Bool
+    sys.modules["geometry_msgs.msg"].Twist = _Twist
+    sys.modules["saltybot_social_msgs.msg"].FaceDetectionArray = _FaceDetectionArray
+    sys.modules["saltybot_social_msgs.msg"].PersonStateArray   = _PersonStateArray
+
+    return (_Node, _FakePub, _Bool, _Twist,
+            _FaceDetection, _PersonState,
+            _FaceDetectionArray, _PersonStateArray)
+
+
+(_Node, _FakePub, _Bool, _Twist,
+ _FaceDetection, _PersonState,
+ _FaceDetectionArray, _PersonStateArray) = _make_ros_stubs()
+
+
+# ── Module loader ─────────────────────────────────────────────────────────────
+
+_SRC = (
+    "/Users/seb/AI/saltylab-firmware/jetson/ros2_ws/src/"
+    "saltybot_social/saltybot_social/personal_space_node.py"
+)
+
+
+def _load_mod():
+    spec = importlib.util.spec_from_file_location("personal_space_testmod", _SRC)
+    mod  = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(mod)
+    return mod
+
+
+def _make_node(mod, **kwargs):
+    node = mod.PersonalSpaceNode.__new__(mod.PersonalSpaceNode)
+    defaults = {
+        "personal_space_m":   0.8,
+        "backup_speed":       0.1,
+        "hysteresis_m":       0.1,
+        "unknown_distance_m": 99.0,
+        "lost_timeout_s":     1.5,
+        "control_rate":       10.0,
+        "faces_topic":        "/social/faces/detected",
+        "states_topic":       "/social/person_states",
+    }
+    defaults.update(kwargs)
+    node._params = dict(defaults)
+    mod.PersonalSpaceNode.__init__(node)
+    return node
+
+
+def _inject_faces(node, face_ids):
+    """Push a FaceDetectionArray message with the given face_ids."""
+    msg = _FaceDetectionArray(faces=[_FaceDetection(fid) for fid in face_ids])
+    node._subs["/social/faces/detected"](msg)
+
+
+def _inject_states(node, id_dist_pairs):
+    """Push a PersonStateArray message with (face_id, distance) pairs."""
+    persons = [_PersonState(fid, dist) for fid, dist in id_dist_pairs]
+    msg = _PersonStateArray(persons=persons)
+    node._subs["/social/person_states"](msg)
+
+
+# ── Tests: pure helpers ────────────────────────────────────────────────────────
+
+class TestClosestFaceDistance(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls): cls.mod = _load_mod()
+
+    def _cfd(self, face_ids, cache, unknown=99.0):
+        return self.mod.closest_face_distance(face_ids, cache, unknown)
+
+    def test_empty_face_ids_returns_unknown(self):
+        self.assertEqual(self._cfd([], {}), 99.0)
+
+    def test_single_face_known(self):
+        self.assertAlmostEqual(self._cfd([1], {1: 0.5}), 0.5)
+
+    def test_single_face_unknown(self):
+        self.assertEqual(self._cfd([1], {}), 99.0)
+
+    def test_multiple_faces_min(self):
+        dist = self._cfd([1, 2, 3], {1: 2.0, 2: 0.5, 3: 1.5})
+        self.assertAlmostEqual(dist, 0.5)
+
+    def test_mixed_known_unknown(self):
+        # unknown face treated as unknown_distance_m = 99, so min is the known one
+        dist = self._cfd([1, 2], {1: 0.6}, 99.0)
+        self.assertAlmostEqual(dist, 0.6)
+
+    def test_all_unknown_returns_unknown(self):
+        dist = self._cfd([1, 2], {}, 99.0)
+        self.assertEqual(dist, 99.0)
+
+    def test_custom_unknown_value(self):
+        dist = self._cfd([], {}, unknown=5.0)
+        self.assertEqual(dist, 5.0)
+
+
+class TestShouldBackup(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls): cls.mod = _load_mod()
+
+    def test_at_threshold_triggers(self):
+        self.assertTrue(self.mod.should_backup(0.8, 0.8))
+
+    def test_below_threshold_triggers(self):
+        self.assertTrue(self.mod.should_backup(0.5, 0.8))
+
+    def test_above_threshold_no_trigger(self):
+        self.assertFalse(self.mod.should_backup(1.0, 0.8))
+
+    def test_just_above_no_trigger(self):
+        self.assertFalse(self.mod.should_backup(0.81, 0.8))
+
+
+class TestShouldClear(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls): cls.mod = _load_mod()
+
+    def test_above_band_clears(self):
+        # 0.8 + 0.1 = 0.9; 1.0 > 0.9 → clear
+        self.assertTrue(self.mod.should_clear(1.0, 0.8, 0.1))
+
+    def test_at_band_edge_does_not_clear(self):
+        self.assertFalse(self.mod.should_clear(0.9, 0.8, 0.1))
+
+    def test_within_band_does_not_clear(self):
+        self.assertFalse(self.mod.should_clear(0.85, 0.8, 0.1))
+
+    def test_below_threshold_does_not_clear(self):
+        self.assertFalse(self.mod.should_clear(0.5, 0.8, 0.1))
+
+    def test_just_above_band_clears(self):
+        self.assertTrue(self.mod.should_clear(0.91, 0.8, 0.1))
+
+
+# ── Tests: node init ──────────────────────────────────────────────────────────
+
+class TestNodeInit(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls): cls.mod = _load_mod()
+
+    def test_instantiates(self):
+        self.assertIsNotNone(_make_node(self.mod))
+
+    def test_cmd_vel_publisher(self):
+        node = _make_node(self.mod)
+        self.assertIn("/cmd_vel", node._pubs)
+
+    def test_too_close_publisher(self):
+        node = _make_node(self.mod)
+        self.assertIn("/saltybot/too_close", node._pubs)
+
+    def test_faces_subscriber(self):
+        node = _make_node(self.mod)
+        self.assertIn("/social/faces/detected", node._subs)
+
+    def test_states_subscriber(self):
+        node = _make_node(self.mod)
+        self.assertIn("/social/person_states", node._subs)
+
+    def test_timer_registered(self):
+        node = _make_node(self.mod)
+        self.assertGreater(len(node._timers), 0)
+
+    def test_too_close_initially_false(self):
+        node = _make_node(self.mod)
+        self.assertFalse(node._too_close)
+
+    def test_distance_cache_empty(self):
+        node = _make_node(self.mod)
+        self.assertEqual(node._distance_cache, {})
+
+    def test_active_face_ids_empty(self):
+        node = _make_node(self.mod)
+        self.assertEqual(node._active_face_ids, [])
+
+    def test_custom_topics(self):
+        node = _make_node(self.mod,
+                          faces_topic="/my/faces",
+                          states_topic="/my/states")
+        self.assertIn("/my/faces",  node._subs)
+        self.assertIn("/my/states", node._subs)
+
+    def test_parameters_stored(self):
+        node = _make_node(self.mod, personal_space_m=1.2, backup_speed=0.2)
+        self.assertAlmostEqual(node._space,        1.2)
+        self.assertAlmostEqual(node._backup_speed, 0.2)
+
+
+# ── Tests: _on_person_states ──────────────────────────────────────────────────
+
+class TestOnPersonStates(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls): cls.mod = _load_mod()
+
+    def setUp(self):
+        self.node = _make_node(self.mod)
+
+    def test_single_state_cached(self):
+        _inject_states(self.node, [(1, 1.5)])
+        self.assertAlmostEqual(self.node._distance_cache[1], 1.5)
+
+    def test_multiple_states_cached(self):
+        _inject_states(self.node, [(1, 1.5), (2, 0.6), (3, 2.0)])
+        self.assertAlmostEqual(self.node._distance_cache[1], 1.5)
+        self.assertAlmostEqual(self.node._distance_cache[2], 0.6)
+        self.assertAlmostEqual(self.node._distance_cache[3], 2.0)
+
+    def test_state_updated_on_second_msg(self):
+        _inject_states(self.node, [(1, 1.5)])
+        _inject_states(self.node, [(1, 0.4)])
+        self.assertAlmostEqual(self.node._distance_cache[1], 0.4)
+
+    def test_negative_face_id_ignored(self):
+        _inject_states(self.node, [(-1, 0.5)])
+        self.assertNotIn(-1, self.node._distance_cache)
+
+    def test_zero_face_id_stored(self):
+        _inject_states(self.node, [(0, 0.7)])
+        self.assertIn(0, self.node._distance_cache)
+
+    def test_distance_cast_to_float(self):
+        _inject_states(self.node, [(1, 1)])   # integer distance
+        self.assertIsInstance(self.node._distance_cache[1], float)
+
+
+# ── Tests: _on_faces ──────────────────────────────────────────────────────────
+
+class TestOnFaces(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls): cls.mod = _load_mod()
+
+    def setUp(self):
+        self.node = _make_node(self.mod)
+
+    def test_face_ids_stored(self):
+        _inject_faces(self.node, [1, 2, 3])
+        self.assertEqual(sorted(self.node._active_face_ids), [1, 2, 3])
+
+    def test_empty_faces_stored(self):
+        _inject_faces(self.node, [])
+        self.assertEqual(self.node._active_face_ids, [])
+
+    def test_timestamp_updated_on_faces(self):
+        before = time.monotonic()
+        _inject_faces(self.node, [1])
+        self.assertGreaterEqual(self.node._last_face_t, before)
+
+    def test_timestamp_not_updated_on_empty(self):
+        self.node._last_face_t = 0.0
+        _inject_faces(self.node, [])
+        self.assertEqual(self.node._last_face_t, 0.0)
+
+    def test_faces_replaced_not_merged(self):
+        _inject_faces(self.node, [1, 2])
+        _inject_faces(self.node, [3])
+        self.assertEqual(sorted(self.node._active_face_ids), [3])
+
+
+# ── Tests: control loop ───────────────────────────────────────────────────────
+
+class TestControlLoop(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls): cls.mod = _load_mod()
+
+    def setUp(self):
+        self.node = _make_node(self.mod, personal_space_m=0.8, backup_speed=0.1,
+                               hysteresis_m=0.1, lost_timeout_s=1.5)
+        self.cmd_pub    = self.node._pubs["/cmd_vel"]
+        self.close_pub  = self.node._pubs["/saltybot/too_close"]
+
+    def _fresh_face(self, face_id=1, distance=1.0):
+        """Inject a face + state so the node sees a fresh, close/far person."""
+        _inject_states(self.node, [(face_id, distance)])
+        _inject_faces(self.node, [face_id])
+
+    def test_no_face_publishes_zero_twist(self):
+        self.node._control_cb()
+        self.assertEqual(len(self.cmd_pub.msgs), 1)
+        self.assertAlmostEqual(self.cmd_pub.msgs[-1].linear.x, 0.0)
+
+    def test_no_face_publishes_false(self):
+        self.node._control_cb()
+        self.assertFalse(self.close_pub.msgs[-1].data)
+
+    def test_person_far_no_backup(self):
+        self._fresh_face(distance=1.5)
+        self.node._control_cb()
+        self.assertAlmostEqual(self.cmd_pub.msgs[-1].linear.x, 0.0)
+        self.assertFalse(self.close_pub.msgs[-1].data)
+
+    def test_person_at_threshold_triggers_backup(self):
+        self._fresh_face(distance=0.8)
+        self.node._control_cb()
+        self.assertAlmostEqual(self.cmd_pub.msgs[-1].linear.x, -0.1)
+        self.assertTrue(self.close_pub.msgs[-1].data)
+
+    def test_person_too_close_triggers_backup(self):
+        self._fresh_face(distance=0.5)
+        self.node._control_cb()
+        self.assertAlmostEqual(self.cmd_pub.msgs[-1].linear.x, -0.1)
+        self.assertTrue(self.close_pub.msgs[-1].data)
+
+    def test_too_close_state_latches(self):
+        """State stays TOO_CLOSE even if distance jumps to mid-band."""
+        self._fresh_face(distance=0.5)
+        self.node._control_cb()  # enter TOO_CLOSE
+        # Now person is at 0.85 — inside hysteresis band (0.8 < 0.85 < 0.9)
+        _inject_states(self.node, [(1, 0.85)])
+        self.node._control_cb()
+        self.assertTrue(self.node._too_close)
+        self.assertTrue(self.close_pub.msgs[-1].data)
+
+    def test_hysteresis_clears_state(self):
+        """State clears when distance exceeds personal_space_m + hysteresis_m."""
+        self._fresh_face(distance=0.5)
+        self.node._control_cb()  # enter TOO_CLOSE
+        # Person retreats past hysteresis band (> 0.9 m)
+        _inject_states(self.node, [(1, 1.0)])
+        self.node._control_cb()
+        self.assertFalse(self.node._too_close)
+        self.assertFalse(self.close_pub.msgs[-1].data)
+
+    def test_backup_speed_magnitude(self):
+        node = _make_node(self.mod, backup_speed=0.25)
+        _inject_states(node, [(1, 0.3)])
+        _inject_faces(node, [1])
+        node._control_cb()
+        self.assertAlmostEqual(node._pubs["/cmd_vel"].msgs[-1].linear.x, -0.25)
+
+    def test_state_machine_full_cycle(self):
+        """CLEAR → TOO_CLOSE → CLEAR."""
+        # Start clear
+        self._fresh_face(distance=1.5)
+        self.node._control_cb()
+        self.assertFalse(self.node._too_close)
+
+        # Enter TOO_CLOSE
+        _inject_states(self.node, [(1, 0.5)])
+        self.node._control_cb()
+        self.assertTrue(self.node._too_close)
+
+        # Return to CLEAR
+        _inject_states(self.node, [(1, 1.0)])
+        self.node._control_cb()
+        self.assertFalse(self.node._too_close)
+
+    def test_multiple_faces_closest_used(self):
+        """Closest face determines the backup decision."""
+        _inject_states(self.node, [(1, 2.0), (2, 0.5)])
+        _inject_faces(self.node, [1, 2])
+        self.node._control_cb()
+        self.assertTrue(self.node._too_close)
+
+    def test_both_far_no_backup(self):
+        _inject_states(self.node, [(1, 1.5), (2, 2.0)])
+        _inject_faces(self.node, [1, 2])
+        self.node._control_cb()
+        self.assertFalse(self.node._too_close)
+
+    def test_unknown_face_uses_unknown_distance(self):
+        """Face without PersonState gets unknown_distance_m (default=99 → safe)."""
+        # No PersonState injected, so face_id=5 has no cache entry
+        _inject_faces(self.node, [5])
+        self.node._last_face_t = time.monotonic()  # mark fresh
+        self.node._control_cb()
+        self.assertFalse(self.node._too_close)
+
+    def test_publishes_on_every_tick(self):
+        self.node._control_cb()
+        self.node._control_cb()
+        self.node._control_cb()
+        self.assertEqual(len(self.cmd_pub.msgs),   3)
+        self.assertEqual(len(self.close_pub.msgs), 3)
+
+
+# ── Tests: face freshness / lost timeout ──────────────────────────────────────
+
+class TestFaceFreshness(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls): cls.mod = _load_mod()
+
+    def setUp(self):
+        self.node = _make_node(self.mod, lost_timeout_s=1.5)
+        self.cmd_pub   = self.node._pubs["/cmd_vel"]
+        self.close_pub = self.node._pubs["/saltybot/too_close"]
+
+    def test_stale_face_clears_state(self):
+        """If no fresh face data, state clears and robot stops."""
+        # Manually set backed-up state
+        self.node._too_close = True
+        self.node._last_face_t = time.monotonic() - 10.0  # stale
+        self.node._control_cb()
+        self.assertFalse(self.node._too_close)
+        self.assertAlmostEqual(self.cmd_pub.msgs[-1].linear.x, 0.0)
+        self.assertFalse(self.close_pub.msgs[-1].data)
+
+    def test_fresh_face_active(self):
+        """Recently received face is treated as fresh."""
+        _inject_states(self.node, [(1, 0.5)])
+        _inject_faces(self.node, [1])  # updates _last_face_t
+        self.node._control_cb()
+        self.assertTrue(self.node._too_close)
+
+    def test_no_face_ever_is_stale(self):
+        """Never received a face → stale, no backup."""
+        # _last_face_t = 0.0 (default) → not fresh
+        self.node._control_cb()
+        self.assertFalse(self.node._too_close)
+
+    def test_stale_logs_info(self):
+        self.node._too_close = True
+        self.node._last_face_t = time.monotonic() - 100.0
+        self.node._control_cb()
+        infos = [l for l in self.node._logs if l[0] == "INFO"]
+        self.assertTrue(any("face lost" in m.lower() or "clearing" in m.lower()
+                            for _, m in infos))
+
+    def test_too_close_entry_logs_warn(self):
+        _inject_states(self.node, [(1, 0.3)])
+        _inject_faces(self.node, [1])
+        self.node._control_cb()
+        warns = [l for l in self.node._logs if l[0] == "WARN"]
+        self.assertTrue(any("too close" in m.lower() or "backing" in m.lower()
+                            for _, m in warns))
+
+    def test_clear_logs_info(self):
+        _inject_states(self.node, [(1, 0.3)])
+        _inject_faces(self.node, [1])
+        self.node._control_cb()
+        _inject_states(self.node, [(1, 1.5)])
+        self.node._control_cb()
+        infos = [l for l in self.node._logs if l[0] == "INFO"]
+        self.assertTrue(any("clear" in m.lower() for _, m in infos))
+
+
+# ── Tests: _publish ───────────────────────────────────────────────────────────
+
+class TestPublish(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls): cls.mod = _load_mod()
+
+    def setUp(self):
+        self.node     = _make_node(self.mod, backup_speed=0.15)
+        self.cmd_pub  = self.node._pubs["/cmd_vel"]
+        self.bool_pub = self.node._pubs["/saltybot/too_close"]
+
+    def test_backup_false_zero_linear_x(self):
+        self.node._publish(backup=False)
+        self.assertAlmostEqual(self.cmd_pub.msgs[-1].linear.x, 0.0)
+
+    def test_backup_true_negative_linear_x(self):
+        self.node._publish(backup=True)
+        self.assertAlmostEqual(self.cmd_pub.msgs[-1].linear.x, -0.15)
+
+    def test_backup_false_bool_false(self):
+        self.node._publish(backup=False)
+        self.assertFalse(self.bool_pub.msgs[-1].data)
+
+    def test_backup_true_bool_true(self):
+        self.node._publish(backup=True)
+        self.assertTrue(self.bool_pub.msgs[-1].data)
+
+    def test_angular_z_always_zero(self):
+        self.node._publish(backup=True)
+        self.assertAlmostEqual(self.cmd_pub.msgs[-1].angular.z, 0.0)
+
+    def test_both_topics_published(self):
+        self.node._publish(backup=False)
+        self.assertEqual(len(self.cmd_pub.msgs),  1)
+        self.assertEqual(len(self.bool_pub.msgs), 1)
+
+
+# ── Tests: source content ─────────────────────────────────────────────────────
+
+class TestNodeSrc(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        with open(_SRC) as f: cls.src = f.read()
+
+    def test_issue_tag(self):            self.assertIn("#310", self.src)
+    def test_cmd_vel_topic(self):        self.assertIn("/cmd_vel", self.src)
+    def test_too_close_topic(self):      self.assertIn("/saltybot/too_close", self.src)
+    def test_faces_topic(self):          self.assertIn("/social/faces/detected", self.src)
+    def test_states_topic(self):         self.assertIn("/social/person_states", self.src)
+    def test_closest_face_fn(self):      self.assertIn("closest_face_distance", self.src)
+    def test_should_backup_fn(self):     self.assertIn("should_backup", self.src)
+    def test_should_clear_fn(self):      self.assertIn("should_clear", self.src)
+    def test_hysteresis_param(self):     self.assertIn("hysteresis_m", self.src)
+    def test_backup_speed_param(self):   self.assertIn("backup_speed", self.src)
+    def test_personal_space_param(self): self.assertIn("personal_space_m", self.src)
+    def test_lost_timeout_param(self):   self.assertIn("lost_timeout_s", self.src)
+    def test_control_rate_param(self):   self.assertIn("control_rate", self.src)
+    def test_threading_lock(self):       self.assertIn("threading.Lock", self.src)
+    def test_linear_x(self):            self.assertIn("linear.x", self.src)
+    def test_twist_published(self):      self.assertIn("Twist", self.src)
+    def test_bool_published(self):       self.assertIn("Bool", self.src)
+    def test_main_defined(self):         self.assertIn("def main", self.src)
+    def test_face_detection_array(self): self.assertIn("FaceDetectionArray", self.src)
+    def test_person_state_array(self):   self.assertIn("PersonStateArray", self.src)
+
+
+# ── Tests: config / launch / setup ────────────────────────────────────────────
+
+class TestConfig(unittest.TestCase):
+    _CONFIG = (
+        "/Users/seb/AI/saltylab-firmware/jetson/ros2_ws/src/"
+        "saltybot_social/config/personal_space_params.yaml"
+    )
+    _LAUNCH = (
+        "/Users/seb/AI/saltylab-firmware/jetson/ros2_ws/src/"
+        "saltybot_social/launch/personal_space.launch.py"
+    )
+    _SETUP = (
+        "/Users/seb/AI/saltylab-firmware/jetson/ros2_ws/src/"
+        "saltybot_social/setup.py"
+    )
+
+    def test_config_exists(self):
+        import os; self.assertTrue(os.path.exists(self._CONFIG))
+
+    def test_config_personal_space_m(self):
+        with open(self._CONFIG) as f: c = f.read()
+        self.assertIn("personal_space_m", c)
+
+    def test_config_backup_speed(self):
+        with open(self._CONFIG) as f: c = f.read()
+        self.assertIn("backup_speed", c)
+
+    def test_config_hysteresis(self):
+        with open(self._CONFIG) as f: c = f.read()
+        self.assertIn("hysteresis_m", c)
+
+    def test_config_lost_timeout(self):
+        with open(self._CONFIG) as f: c = f.read()
+        self.assertIn("lost_timeout_s", c)
+
+    def test_launch_exists(self):
+        import os; self.assertTrue(os.path.exists(self._LAUNCH))
+
+    def test_launch_has_personal_space_arg(self):
+        with open(self._LAUNCH) as f: c = f.read()
+        self.assertIn("personal_space_m", c)
+
+    def test_launch_has_backup_speed_arg(self):
+        with open(self._LAUNCH) as f: c = f.read()
+        self.assertIn("backup_speed", c)
+
+    def test_entry_point_in_setup(self):
+        with open(self._SETUP) as f: c = f.read()
+        self.assertIn("personal_space_node", c)
+
+
+if __name__ == "__main__":
+    unittest.main()