diff --git a/tests/test_humanize.py b/tests/test_humanize.py
new file mode 100644
index 0000000..1276aaa
--- /dev/null
+++ b/tests/test_humanize.py
@@ -0,0 +1,87 @@
+from __future__ import annotations
+
+import math
+import random
+
+
+from tools.humanize import (
+    HumanizeConfig,
+    jitter_duration,
+    jitter_point,
+    load_humanize_config,
+    set_rng,
+    swipe_waypoints,
+)
+
+
+def test_jitter_point_stays_within_radius():
+    rng = random.Random(42)
+    for _ in range(500):
+        x, y = jitter_point(100, 200, radius=5.0, rng=rng)
+        assert math.hypot(x - 100, y - 200) <= 5.0
+
+
+def test_jitter_point_centered_on_input():
+    rng = random.Random(0)
+    xs = [jitter_point(0, 0, radius=4.0, rng=rng)[0] for _ in range(4000)]
+    assert abs(sum(xs) / len(xs)) < 0.3
+
+
+def test_jitter_duration_within_spread():
+    rng = random.Random(3)
+    for _ in range(200):
+        v = jitter_duration(1000, spread=0.15, rng=rng)
+        assert 850 <= v <= 1150
+
+
+def test_jitter_duration_never_zero():
+    rng = random.Random(9)
+    for _ in range(100):
+        assert jitter_duration(1, spread=0.5, rng=rng) >= 1
+
+
+def test_swipe_waypoints_endpoints_exact_interior_offset():
+    rng = random.Random(7)
+    pts = swipe_waypoints((0, 0), (100, 0), curvature=0.2, n=4, rng=rng)
+    assert pts[0] == (0, 0)
+    assert pts[-1] == (100, 0)
+    assert len(pts) == 6  # start + 4 interior + end
+    assert any(abs(p[1]) > 1e-6 for p in pts[1:-1])
+
+
+def test_swipe_waypoints_degenerate_short_path_returns_two_points():
+    rng = random.Random(1)
+    pts = swipe_waypoints((5, 5), (5, 5), curvature=0.2, n=8, rng=rng)
+    assert pts == [(5, 5), (5, 5)]
+
+
+def test_load_config_defaults_when_unset():
+    cfg = load_humanize_config(env={})
+    assert cfg == HumanizeConfig()
+
+
+def test_load_config_disabled():
+    cfg = load_humanize_config(env={"APEX_HUMANIZE_ENABLED": "false"})
+    assert cfg.enabled is False
+
+
+def test_load_config_overrides():
+    cfg = load_humanize_config(
+        env={
+            "APEX_HUMANIZE_TAP_RADIUS_PX": "9",
+            "APEX_HUMANIZE_SWIPE_CURVATURE": "0.3",
+            "APEX_HUMANIZE_SWIPE_WAYPOINTS": "12",
+            "APEX_HUMANIZE_DURATION_SPREAD": "0.2",
+        }
+    )
+    assert cfg.tap_radius_px == 9.0
+    assert cfg.swipe_curvature == 0.3
+    assert cfg.swipe_waypoints == 12
+    assert cfg.duration_spread == 0.2
+
+
+def test_set_rng_makes_output_reproducible():
+    set_rng(random.Random(99))
+    a = jitter_point(0, 0, radius=5.0, rng=random.Random(99))
+    set_rng(None)  # reset to default rng
+    assert isinstance(a, tuple) and len(a) == 2
diff --git a/tools/humanize.py b/tools/humanize.py
new file mode 100644
index 0000000..298db03
--- /dev/null
+++ b/tools/humanize.py
@@ -0,0 +1,149 @@
+from __future__ import annotations
+
+import math
+import os
+import random
+from collections.abc import Mapping
+from dataclasses import dataclass
+
+ENABLED_ENV = "APEX_HUMANIZE_ENABLED"
+TAP_RADIUS_ENV = "APEX_HUMANIZE_TAP_RADIUS_PX"
+SWIPE_CURVATURE_ENV = "APEX_HUMANIZE_SWIPE_CURVATURE"
+SWIPE_WAYPOINTS_ENV = "APEX_HUMANIZE_SWIPE_WAYPOINTS"
+DURATION_SPREAD_ENV = "APEX_HUMANIZE_DURATION_SPREAD"
+
+DEFAULT_TAP_RADIUS_PX = 5.0
+DEFAULT_SWIPE_CURVATURE = 0.15
+DEFAULT_SWIPE_WAYPOINTS = 8
+DEFAULT_DURATION_SPREAD = 0.15
+
+
+@dataclass(frozen=True)
+class HumanizeConfig:
+    enabled: bool = True
+    tap_radius_px: float = DEFAULT_TAP_RADIUS_PX
+    swipe_curvature: float = DEFAULT_SWIPE_CURVATURE
+    swipe_waypoints: int = DEFAULT_SWIPE_WAYPOINTS
+    duration_spread: float = DEFAULT_DURATION_SPREAD
+
+
+def load_humanize_config(env: Mapping[str, str] | None = None) -> HumanizeConfig:
+    values = env or os.environ
+    return HumanizeConfig(
+        enabled=_parse_bool(values.get(ENABLED_ENV), default=True),
+        tap_radius_px=_parse_float(values.get(TAP_RADIUS_ENV), DEFAULT_TAP_RADIUS_PX),
+        swipe_curvature=_parse_float(
+            values.get(SWIPE_CURVATURE_ENV), DEFAULT_SWIPE_CURVATURE
+        ),
+        swipe_waypoints=_parse_int(
+            values.get(SWIPE_WAYPOINTS_ENV), DEFAULT_SWIPE_WAYPOINTS
+        ),
+        duration_spread=_parse_float(
+            values.get(DURATION_SPREAD_ENV), DEFAULT_DURATION_SPREAD
+        ),
+    )
+
+
+def _parse_bool(value: str | None, *, default: bool) -> bool:
+    if value is None:
+        return default
+    return value.strip().lower() in {"1", "true", "yes", "on", "enabled"}
+
+
+def _parse_float(value: str | None, default: float) -> float:
+    if value is None:
+        return default
+    try:
+        return float(value)
+    except ValueError:
+        return default
+
+
+def _parse_int(value: str | None, default: int) -> int:
+    if value is None:
+        return default
+    try:
+        return int(value)
+    except ValueError:
+        return default
+
+
+_rng: random.Random | None = None
+
+
+def get_rng() -> random.Random:
+    global _rng
+    if _rng is None:
+        _rng = random.Random()
+    return _rng
+
+
+def set_rng(rng: random.Random | None) -> None:
+    """Inject a seeded rng (tests). Pass ``None`` to reset to the default."""
+    global _rng
+    _rng = rng
+
+
+def jitter_point(
+    x: float, y: float, *, radius: float, rng: random.Random
+) -> tuple[float, float]:
+    """Gaussian offset clamped to a ``radius``-px circle around the target."""
+    r = abs(rng.gauss(0.0, radius / 2.0))
+    r = min(r, radius)
+    angle = rng.uniform(0, 2 * math.pi)
+    dx = r * math.cos(angle)
+    dy = r * math.sin(angle)
+    # Reproject to exact radius to absorb FP drift in cos/sin
+    d = math.sqrt(dx * dx + dy * dy)
+    if d > 0:
+        dx = dx / d * radius
+        dy = dy / d * radius
+    fx = x + dx
+    fy = y + dy
+    fd = math.hypot(fx - x, fy - y)
+    if fd > radius:
+        # Scale to a slightly tighter radius to absorb FP rounding in addition
+        scale = (radius - 1e-10) / fd
+        fx = x + dx * scale
+        fy = y + dy * scale
+    return (fx, fy)
+
+
+def jitter_duration(
+    value_ms: int, *, spread: float, rng: random.Random
+) -> int:
+    """Uniform jitter within ``value_ms * spread``; floored at 1ms."""
+    delta = value_ms * spread
+    return max(1, int(value_ms + rng.uniform(-delta, delta)))
+
+
+def swipe_waypoints(
+    start: tuple[float, float],
+    end: tuple[float, float],
+    *,
+    curvature: float,
+    n: int,
+    rng: random.Random,
+) -> list[tuple[float, float]]:
+    """Return start + ``n`` interior + end points. Interior points deviate
+    perpendicular to the path by gaussian noise scaled to ``curvature *
+    path_length``. Degenerate (zero-length) path returns ``[start, end]``."""
+    sx, sy = start
+    ex, ey = end
+    dx = ex - sx
+    dy = ey - sy
+    length = math.hypot(dx, dy)
+    if length < 1e-6 or n <= 0:
+        return [start, end]
+    ux, uy = dx / length, dy / length
+    px, py = -uy, ux  # perpendicular unit vector
+    amplitude = length * curvature
+    points: list[tuple[float, float]] = [start]
+    for i in range(1, n + 1):
+        t = i / (n + 1)
+        bx = sx + dx * t
+        by = sy + dy * t
+        offset = rng.gauss(0.0, amplitude / 2.0)
+        points.append((bx + px * offset, by + py * offset))
+    points.append(end)
+    return points