diff --git a/arautopilot/core/autotuner.py b/arautopilot/core/autotuner.py
new file mode 100644
index 0000000..63188ec
--- /dev/null
+++ b/arautopilot/core/autotuner.py
@@ -0,0 +1,199 @@
+"""Relay-feedback Ziegler-Nichols auto-tuner -- Sprint 7.
+
+Implements the closed-loop relay auto-tuning method (Åström & Hägglund 1984)
+to identify the ultimate gain ``Ku`` and ultimate period ``Tu`` from a single
+relay experiment, then converts them to PID gains using the ZN formulas.
+
+The relay oscillation amplitude ``d`` is chosen so the actuator stays within
+a safe excitation band during commissioning (typically ±5 % of full-scale
+rudder output).
+
+Usage::
+
+    tuner = RelayAutoTuner(relay_amplitude=5.0, min_cycles=3)
+
+    # Feed the error signal at the control rate (10 Hz outer loop).
+    for step in simulation:
+        output = tuner.step(error_deg)
+
+    result = tuner.result()
+    if result.converged:
+        gains = result.to_pid_gains()
+
+Theory
+------
+The relay switches its output between ``+d`` and ``-d`` based on the sign of
+the process error. The resulting limit cycle has amplitude ``a`` (peak
+deviation of the output) and period ``Tu``. The ultimate gain is:
+
+    Ku = 4d / (π a)
+
+ZN formulas for PID (tuned for setpoint tracking):
+
+    Kp = 0.6 · Ku
+    Ki = 1.2 · Ku / Tu      (= 2 · Kp / Tu)
+    Kd = 0.075 · Ku · Tu    (= Kp · Tu / 8)
+"""
+
+from __future__ import annotations
+
+import math
+from dataclasses import dataclass, field
+
+from arautopilot.core.pid_config import PidGains
+
+
+@dataclass
+class TunerResult:
+    """Outcome of one relay experiment."""
+
+    converged: bool = False
+    ku: float = 0.0           # ultimate gain
+    tu_s: float = 0.0         # ultimate period, seconds
+    cycles_detected: int = 0  # full half-cycles ÷ 2
+
+    # Raw measurements
+    amplitude: float = 0.0   # peak-to-peak process amplitude / 2 (deg)
+    relay_amplitude: float = 0.0  # relay output magnitude used
+
+    def to_pid_gains(self) -> PidGains:
+        """Convert Ku / Tu to ZN-formula PID gains."""
+        if not self.converged:
+            raise RuntimeError("Tuner has not converged yet")
+        kp = 0.6 * self.ku
+        ki = 1.2 * self.ku / self.tu_s if self.tu_s > 0 else 0.0
+        kd = 0.075 * self.ku * self.tu_s
+        return PidGains(kp=round(kp, 4), ki=round(ki, 4), kd=round(kd, 4))
+
+
+class RelayAutoTuner:
+    """Closed-loop relay auto-tuner (10 Hz outer-loop step clock).
+
+    Parameters
+    ----------
+    relay_amplitude:
+        Magnitude of the relay output in degrees of rudder.
+    min_cycles:
+        Minimum number of complete oscillation cycles before declaring
+        convergence.  Typically 3–5 for a reliable estimate.
+    dt_s:
+        Time step in seconds (default 0.1 for 10 Hz outer loop).
+    max_steps:
+        Safety cut-off: abort if the experiment runs longer than this many
+        control steps.
+    """
+
+    def __init__(
+        self,
+        relay_amplitude: float = 5.0,
+        min_cycles: int = 3,
+        dt_s: float = 0.1,
+        max_steps: int = 6000,  # 10 min at 10 Hz
+    ) -> None:
+        if relay_amplitude <= 0:
+            raise ValueError("relay_amplitude must be positive")
+        if min_cycles < 1:
+            raise ValueError("min_cycles must be >= 1")
+
+        self._d: float = relay_amplitude
+        self._min_cycles: int = min_cycles
+        self._dt: float = dt_s
+        self._max_steps: int = max_steps
+
+        # State
+        self._relay_output: float = self._d  # starts positive
+        self._step_count: int = 0
+        self._done: bool = False
+
+        # Peak tracking for amplitude estimation
+        self._peak_buffer: list[float] = []   # absolute peak values
+        self._last_sign: int = 0              # sign of the last error sample
+
+        # Half-cycle timing
+        self._half_cycle_start: int = 0
+        self._half_period_steps: list[float] = []  # in steps
+
+        # Running amplitude samples (one per half-cycle)
+        self._amp_peaks: list[float] = []    # max abs(error) per half-cycle
+        self._current_max: float = 0.0
+
+    # ------------------------------------------------------------------
+
+    def step(self, error: float) -> float:
+        """Feed one error sample; return the relay output (degrees of rudder).
+
+        Parameters
+        ----------
+        error:
+            Heading error in degrees (setpoint – measured).
+
+        Returns
+        -------
+        float
+            Rudder command in degrees to apply for this step.
+        """
+        if self._done:
+            return 0.0
+
+        self._step_count += 1
+        self._current_max = max(self._current_max, abs(error))
+
+        sign = 1 if error >= 0 else -1
+
+        # Detect zero-crossing (sign change) → half-cycle boundary.
+        if self._last_sign != 0 and sign != self._last_sign:
+            half_len = self._step_count - self._half_cycle_start
+            self._half_period_steps.append(half_len)
+            self._amp_peaks.append(self._current_max)
+            self._current_max = 0.0
+            self._half_cycle_start = self._step_count
+
+            # Toggle relay on sign change.
+            self._relay_output = self._d if sign > 0 else -self._d
+
+            # Check convergence: need 2*min_cycles half-cycles for min_cycles
+            # full cycles.
+            if len(self._half_period_steps) >= 2 * self._min_cycles:
+                self._done = True
+
+        self._last_sign = sign
+
+        # Safety cut-off
+        if self._step_count >= self._max_steps:
+            self._done = True
+
+        return self._relay_output
+
+    @property
+    def is_done(self) -> bool:
+        return self._done
+
+    def result(self) -> TunerResult:
+        """Return the tuning result.  Call only after ``is_done`` is True."""
+        n_half = len(self._half_period_steps)
+        if n_half < 2:
+            return TunerResult(converged=False, relay_amplitude=self._d)
+
+        # Average the last ``2*min_cycles`` half-period measurements
+        # (discard the first half-cycle which is often distorted).
+        use = self._half_period_steps[-2 * self._min_cycles:]
+        tu_s = (sum(use) / len(use)) * 2 * self._dt  # full period
+
+        # Amplitude: average peak-to-peak / 2 of last min_cycles cycles
+        amp_use = self._amp_peaks[-2 * self._min_cycles:]
+        amplitude = sum(amp_use) / len(amp_use)
+
+        if amplitude <= 0:
+            return TunerResult(converged=False, relay_amplitude=self._d)
+
+        # Åström-Hägglund: Ku = 4d / (π a)
+        ku = 4.0 * self._d / (math.pi * amplitude)
+
+        return TunerResult(
+            converged=True,
+            ku=round(ku, 4),
+            tu_s=round(tu_s, 3),
+            cycles_detected=n_half // 2,
+            amplitude=round(amplitude, 3),
+            relay_amplitude=self._d,
+        )
diff --git a/arautopilot/studio/wizards/commissioning_wizard.py b/arautopilot/studio/wizards/commissioning_wizard.py
new file mode 100644
index 0000000..0083c98
--- /dev/null
+++ b/arautopilot/studio/wizards/commissioning_wizard.py
@@ -0,0 +1,259 @@
+"""Commissioning wizard state machine -- Sprint 7.
+
+A pure Python state machine (no UI dependencies) that guides an operator
+through the four commissioning steps:
+
+    1. RUDDER_LIMITS   -- drive rudder full port/stbd, record ADC limits.
+    2. SENSOR_CAL      -- compute linear calibration from ADC limits.
+    3. AUTO_TUNE       -- relay-feedback ZN auto-tune at the configured speed.
+    4. DONE            -- results ready to be written to NVS and ProjectConfig.
+
+The wizard produces a :class:`CommissioningResult` containing calibration
+values and recommended PID gains.  The Studio main window can drive it by
+calling :meth:`CommissioningWizard.step` on each 10 Hz control tick.
+
+Design intent
+-------------
+All hardware interaction is behind a ``transport`` callable (inject the real
+Modbus client or a test stub).  This keeps the wizard fully unit-testable
+without hardware.
+
+Usage::
+
+    def send(cmd: str, value: float) -> float:
+        # cmd is one of: 'move_port', 'move_stbd', 'stop',
+        #                 'read_adc', 'read_error', 'set_rudder'
+        ...
+
+    wiz = CommissioningWizard(transport=send)
+    while not wiz.done:
+        wiz.step()
+    result = wiz.result
+"""
+
+from __future__ import annotations
+
+import time
+from dataclasses import dataclass, field
+from enum import auto, Enum
+
+from arautopilot.core.autotuner import RelayAutoTuner, TunerResult
+from arautopilot.core.pid_config import PidGains
+
+
+class WizardPhase(Enum):
+    RUDDER_LIMITS = auto()
+    SENSOR_CAL    = auto()
+    AUTO_TUNE     = auto()
+    DONE          = auto()
+    ABORTED       = auto()
+
+
+@dataclass
+class CommissioningResult:
+    """Output produced by a completed commissioning run."""
+
+    # Rudder sensor calibration
+    adc_port_limit: int = 0       # raw ADC at full-port stop
+    adc_stbd_limit: int = 4095    # raw ADC at full-stbd stop
+    rudder_port_deg: float = -35.0
+    rudder_stbd_deg: float = 35.0
+
+    # PID recommendations (from ZN auto-tune)
+    tuner_result: TunerResult | None = None
+    recommended_outer_gains: PidGains | None = None
+
+    # Metadata
+    completed: bool = False
+    aborted_reason: str = ""
+
+
+# ---------------------------------------------------------------------------
+# Transport protocol
+# ---------------------------------------------------------------------------
+# The transport callable is called with a command string and an optional
+# float argument; it must return a float (the "response" value, 0.0 if N/A).
+# Commands:
+#   "move_port"    (value ignored) → 0.0
+#   "move_stbd"    (value ignored) → 0.0
+#   "stop"         (value ignored) → 0.0
+#   "read_adc"     (value ignored) → current raw ADC (0..4095)
+#   "read_error"   (value ignored) → current heading error (deg)
+#   "set_rudder"   (value = deg)   → 0.0  (apply relay output to inner loop)
+
+TransportFn = "Callable[[str, float], float]"
+
+
+class CommissioningWizard:
+    """Drives the commissioning sequence at 10 Hz (call ``step()`` each tick).
+
+    Parameters
+    ----------
+    transport:
+        Callable conforming to the protocol above.
+    relay_amplitude:
+        Relay output magnitude for auto-tune, degrees of rudder.
+    min_tune_cycles:
+        Minimum oscillation cycles before auto-tune declares convergence.
+    limit_settle_s:
+        Seconds to wait at each limit stop before sampling ADC.
+    dt_s:
+        Control step in seconds (default 0.1 for 10 Hz).
+    """
+
+    def __init__(
+        self,
+        transport: "Callable[[str, float], float]",
+        relay_amplitude: float = 5.0,
+        min_tune_cycles: int = 3,
+        limit_settle_s: float = 2.0,
+        dt_s: float = 0.1,
+    ) -> None:
+        from typing import Callable  # noqa: F401
+
+        self._tx = transport
+        self._relay_amp = relay_amplitude
+        self._min_cycles = min_tune_cycles
+        self._settle_s = limit_settle_s
+        self._dt = dt_s
+
+        self._phase: WizardPhase = WizardPhase.RUDDER_LIMITS
+        self._sub: str = "drive_port"   # sub-state within RUDDER_LIMITS
+        self._timer: float = 0.0        # time accumulator for settle waits
+        self._result = CommissioningResult()
+        self._tuner: RelayAutoTuner | None = None
+
+    # ------------------------------------------------------------------
+
+    @property
+    def phase(self) -> WizardPhase:
+        return self._phase
+
+    @property
+    def done(self) -> bool:
+        return self._phase in (WizardPhase.DONE, WizardPhase.ABORTED)
+
+    @property
+    def result(self) -> CommissioningResult:
+        return self._result
+
+    def abort(self, reason: str = "operator abort") -> None:
+        self._tx("stop", 0.0)
+        self._phase = WizardPhase.ABORTED
+        self._result.aborted_reason = reason
+
+    # ------------------------------------------------------------------
+    #  Main tick
+    # ------------------------------------------------------------------
+
+    def step(self) -> str:
+        """Advance the wizard by one 10 Hz tick.
+
+        Returns a human-readable status string (for display / logging).
+        """
+        if self.done:
+            return f"wizard {self._phase.name}"
+
+        if self._phase is WizardPhase.RUDDER_LIMITS:
+            return self._tick_limits()
+        if self._phase is WizardPhase.SENSOR_CAL:
+            return self._tick_cal()
+        if self._phase is WizardPhase.AUTO_TUNE:
+            return self._tick_tune()
+        return "unknown phase"
+
+    # ------------------------------------------------------------------
+    #  Phase: RUDDER_LIMITS
+    # ------------------------------------------------------------------
+
+    def _tick_limits(self) -> str:
+        if self._sub == "drive_port":
+            self._tx("move_port", 0.0)
+            self._timer += self._dt
+            if self._timer >= self._settle_s:
+                self._result.adc_port_limit = int(self._tx("read_adc", 0.0))
+                self._sub = "settle_port"
+                self._timer = 0.0
+            return f"driving to port limit... ({self._timer:.1f}s)"
+
+        if self._sub == "settle_port":
+            self._tx("stop", 0.0)
+            self._timer += self._dt
+            if self._timer >= 0.5:
+                self._sub = "drive_stbd"
+                self._timer = 0.0
+            return "settled at port limit"
+
+        if self._sub == "drive_stbd":
+            self._tx("move_stbd", 0.0)
+            self._timer += self._dt
+            if self._timer >= self._settle_s:
+                self._result.adc_stbd_limit = int(self._tx("read_adc", 0.0))
+                self._sub = "settle_stbd"
+                self._timer = 0.0
+            return f"driving to stbd limit... ({self._timer:.1f}s)"
+
+        if self._sub == "settle_stbd":
+            self._tx("stop", 0.0)
+            self._timer += self._dt
+            if self._timer >= 0.5:
+                self._phase = WizardPhase.SENSOR_CAL
+                self._timer = 0.0
+            return "settled at stbd limit"
+
+        return "limits: unknown sub-state"
+
+    # ------------------------------------------------------------------
+    #  Phase: SENSOR_CAL
+    # ------------------------------------------------------------------
+
+    def _tick_cal(self) -> str:
+        # The calibration is computed from the ADC limits gathered above.
+        # This is instantaneous (no hardware interaction needed).
+        lo = self._result.adc_port_limit
+        hi = self._result.adc_stbd_limit
+        if lo == hi:
+            self.abort("sensor cal: port and stbd ADC values are identical")
+            return "sensor cal FAILED: identical ADC values"
+
+        # Ensure lo < hi (swap if wiring is inverted).
+        if lo > hi:
+            lo, hi = hi, lo
+            self._result.rudder_port_deg, self._result.rudder_stbd_deg = (
+                self._result.rudder_stbd_deg,
+                self._result.rudder_port_deg,
+            )
+
+        self._result.adc_port_limit = lo
+        self._result.adc_stbd_limit = hi
+
+        self._phase = WizardPhase.AUTO_TUNE
+        self._tuner = RelayAutoTuner(
+            relay_amplitude=self._relay_amp,
+            min_cycles=self._min_cycles,
+            dt_s=self._dt,
+        )
+        return "sensor calibration done"
+
+    # ------------------------------------------------------------------
+    #  Phase: AUTO_TUNE
+    # ------------------------------------------------------------------
+
+    def _tick_tune(self) -> str:
+        assert self._tuner is not None
+        error = self._tx("read_error", 0.0)
+        rudder_cmd = self._tuner.step(error)
+        self._tx("set_rudder", rudder_cmd)
+
+        if self._tuner.is_done:
+            res = self._tuner.result()
+            self._result.tuner_result = res
+            if res.converged:
+                self._result.recommended_outer_gains = res.to_pid_gains()
+            self._tx("stop", 0.0)
+            self._result.completed = res.converged
+            self._phase = WizardPhase.DONE
+            return f"auto-tune done: Ku={res.ku:.3f} Tu={res.tu_s:.2f}s"
+
+        steps = self._tuner._step_count  # noqa: SLF001
+        return f"auto-tuning... step={steps} cycles={len(self._tuner._half_period_steps)//2}"
diff --git a/arautopilot/tests/test_autotuner.py b/arautopilot/tests/test_autotuner.py
new file mode 100644
index 0000000..bc975e7
--- /dev/null
+++ b/arautopilot/tests/test_autotuner.py
@@ -0,0 +1,229 @@
+"""Tests for the relay auto-tuner and commissioning wizard -- Sprint 7."""
+
+from __future__ import annotations
+
+import math
+import pytest
+
+from arautopilot.core.autotuner import RelayAutoTuner, TunerResult
+from arautopilot.core.pid_config import PidGains
+from arautopilot.studio.wizards.commissioning_wizard import (
+    CommissioningWizard,
+    WizardPhase,
+)
+
+
+# ---------------------------------------------------------------------------
+# Simple first-order vessel model: heading error driven by relay rudder output.
+#
+#   dh/dt = Kv * rudder   (Kv = vessel heading rate gain, deg/(s·deg_rud))
+#
+# At 10 Hz: err_{k+1} = err_k - Kv * relay_k * dt
+# This produces sinusoidal heading oscillation (limit cycle) under relay control.
+# ---------------------------------------------------------------------------
+
+class FirstOrderVessel:
+    """Minimal heading process for relay-tuner tests."""
+
+    def __init__(self, kv: float = 0.3, dt: float = 0.1) -> None:
+        self.heading = 0.0
+        self.setpoint = 0.0
+        self.kv = kv
+        self.dt = dt
+
+    def step(self, rudder_cmd: float) -> float:
+        self.heading += self.kv * rudder_cmd * self.dt
+        return self.setpoint - self.heading  # error
+
+
+# ---------------------------------------------------------------------------
+# RelayAutoTuner tests
+# ---------------------------------------------------------------------------
+
+class TestRelayAutoTuner:
+    def test_invalid_amplitude_raises(self):
+        with pytest.raises(ValueError, match="relay_amplitude"):
+            RelayAutoTuner(relay_amplitude=0.0)
+
+    def test_invalid_min_cycles_raises(self):
+        with pytest.raises(ValueError, match="min_cycles"):
+            RelayAutoTuner(min_cycles=0)
+
+    def test_not_done_before_experiment(self):
+        tuner = RelayAutoTuner()
+        assert not tuner.is_done
+
+    def test_result_not_converged_before_start(self):
+        tuner = RelayAutoTuner()
+        r = tuner.result()
+        assert not r.converged
+
+    def test_converges_on_first_order_plant(self):
+        vessel = FirstOrderVessel(kv=0.4, dt=0.1)
+        tuner = RelayAutoTuner(relay_amplitude=5.0, min_cycles=3, dt_s=0.1)
+        for _ in range(2000):
+            error = vessel.step(tuner.step(vessel.setpoint - vessel.heading))
+            if tuner.is_done:
+                break
+        assert tuner.is_done
+        r = tuner.result()
+        assert r.converged
+        assert r.cycles_detected >= 3
+        assert r.ku > 0
+        assert r.tu_s > 0
+
+    def test_ku_reasonable_range(self):
+        """Ku must be positive and finite; integrating plant gives high Ku (normal)."""
+        vessel = FirstOrderVessel(kv=0.4, dt=0.1)
+        tuner = RelayAutoTuner(relay_amplitude=5.0, min_cycles=3, dt_s=0.1)
+        for _ in range(2000):
+            err = vessel.step(tuner.step(vessel.setpoint - vessel.heading))
+            if tuner.is_done:
+                break
+        r = tuner.result()
+        assert r.ku > 0
+        import math as _math
+        assert _math.isfinite(r.ku)
+
+    def test_to_pid_gains_zn_formulas(self):
+        """ZN formulas: Kp=0.6Ku, Ki=1.2Ku/Tu, Kd=0.075Ku*Tu."""
+        result = TunerResult(converged=True, ku=2.0, tu_s=4.0)
+        gains = result.to_pid_gains()
+        assert abs(gains.kp - 0.6 * 2.0) < 1e-3
+        assert abs(gains.ki - 1.2 * 2.0 / 4.0) < 1e-3
+        assert abs(gains.kd - 0.075 * 2.0 * 4.0) < 1e-3
+
+    def test_to_pid_gains_raises_if_not_converged(self):
+        r = TunerResult(converged=False)
+        with pytest.raises(RuntimeError):
+            r.to_pid_gains()
+
+    def test_output_toggles_at_zero_crossing(self):
+        """After one half-cycle the relay output should flip sign."""
+        tuner = RelayAutoTuner(relay_amplitude=5.0, min_cycles=1, dt_s=0.1)
+        # Drive error positive for several steps.
+        outputs = []
+        for i in range(5):
+            outputs.append(tuner.step(1.0))
+        # Force sign flip.
+        for i in range(3):
+            outputs.append(tuner.step(-1.0))
+        # After the sign change the relay should have flipped.
+        assert outputs[-1] < 0
+
+    def test_max_steps_safety_cutoff(self):
+        tuner = RelayAutoTuner(relay_amplitude=5.0, min_cycles=100, max_steps=50)
+        for _ in range(60):
+            tuner.step(1.0)
+        assert tuner.is_done
+
+    def test_returns_zero_after_done(self):
+        tuner = RelayAutoTuner(relay_amplitude=5.0, min_cycles=100, max_steps=5)
+        for _ in range(10):
+            out = tuner.step(1.0)
+        assert out == 0.0
+
+
+# ---------------------------------------------------------------------------
+# CommissioningWizard tests
+# ---------------------------------------------------------------------------
+
+class StubTransport:
+    """Simple stub that records commands and returns configurable ADC/error values."""
+
+    def __init__(self, adc_port: int = 100, adc_stbd: int = 3900) -> None:
+        self.calls: list[tuple[str, float]] = []
+        self._adc_port = adc_port
+        self._adc_stbd = adc_stbd
+        self._at_port = True      # track which limit we're simulating
+        self.heading = 0.0
+        self.setpoint = 0.0
+
+    def __call__(self, cmd: str, value: float) -> float:
+        self.calls.append((cmd, value))
+        if cmd == "move_port":
+            self._at_port = True
+            return 0.0
+        if cmd == "move_stbd":
+            self._at_port = False
+            return 0.0
+        if cmd == "stop":
+            return 0.0
+        if cmd == "read_adc":
+            return float(self._adc_port if self._at_port else self._adc_stbd)
+        if cmd == "read_error":
+            return self.setpoint - self.heading
+        if cmd == "set_rudder":
+            # Simple first-order response: heading moves 0.3 deg per deg-rudder per 0.1s
+            self.heading += 0.3 * value * 0.1
+            return 0.0
+        return 0.0
+
+
+class TestCommissioningWizard:
+    def test_starts_in_rudder_limits_phase(self):
+        tx = StubTransport()
+        wiz = CommissioningWizard(transport=tx)
+        assert wiz.phase is WizardPhase.RUDDER_LIMITS
+        assert not wiz.done
+
+    def test_abort_stops_wizard(self):
+        tx = StubTransport()
+        wiz = CommissioningWizard(transport=tx)
+        wiz.abort("test abort")
+        assert wiz.phase is WizardPhase.ABORTED
+        assert wiz.done
+        assert wiz.result.aborted_reason == "test abort"
+
+    def test_full_run_completes(self):
+        tx = StubTransport()
+        wiz = CommissioningWizard(
+            transport=tx,
+            relay_amplitude=5.0,
+            min_tune_cycles=3,
+            limit_settle_s=0.5,  # short settle for test speed
+            dt_s=0.1,
+        )
+        # Run until done (up to 15000 steps = 25 min at 10 Hz)
+        for _ in range(15000):
+            wiz.step()
+            if wiz.done:
+                break
+        assert wiz.phase is WizardPhase.DONE
+        assert wiz.result.completed
+        assert wiz.result.recommended_outer_gains is not None
+        gains = wiz.result.recommended_outer_gains
+        assert isinstance(gains, PidGains)
+        assert gains.kp > 0
+
+    def test_adc_limits_recorded(self):
+        tx = StubTransport(adc_port=200, adc_stbd=3800)
+        wiz = CommissioningWizard(transport=tx, limit_settle_s=0.3, dt_s=0.1)
+        for _ in range(15000):
+            wiz.step()
+            if wiz.done:
+                break
+        r = wiz.result
+        # After possible swap, lo < hi
+        assert r.adc_port_limit < r.adc_stbd_limit
+
+    def test_identical_adc_limits_aborts(self):
+        tx = StubTransport(adc_port=2048, adc_stbd=2048)
+        wiz = CommissioningWizard(transport=tx, limit_settle_s=0.3, dt_s=0.1)
+        for _ in range(200):
+            wiz.step()
+            if wiz.done:
+                break
+        assert wiz.phase is WizardPhase.ABORTED
+        assert "identical" in wiz.result.aborted_reason.lower()
+
+    def test_stop_called_on_completion(self):
+        tx = StubTransport()
+        wiz = CommissioningWizard(transport=tx, limit_settle_s=0.3, dt_s=0.1)
+        for _ in range(15000):
+            wiz.step()
+            if wiz.done:
+                break
+        cmds = [c[0] for c in tx.calls]
+        # 'stop' must have been called at least once (after limits and at tune end)
+        assert "stop" in cmds
diff --git a/firmware/ar_autopilot_v1/src/hal/knob_encoder.cpp b/firmware/ar_autopilot_v1/src/hal/knob_encoder.cpp
new file mode 100644
index 0000000..94069ce
--- /dev/null
+++ b/firmware/ar_autopilot_v1/src/hal/knob_encoder.cpp
@@ -0,0 +1,129 @@
+// =============================================================================
+//  hal/knob_encoder.cpp -- Rotary encoder for heading knob (Sprint 7)
+// =============================================================================
+
+#include "knob_encoder.h"
+
+#include <Arduino.h>
+
+#include "../hal/pinout.h"
+#include "../modes/standby.h"
+#include "../pid/pid_outer_task.h"
+#include "../system/ar_log.h"
+#include "../system/task_config.h"
+
+namespace arautopilot::hal {
+
+namespace {
+
+constexpr const char* TAG = "AR/KNOB";
+
+// Encoder pins (reuse DO6/DO7 pads in commissioning variant).
+constexpr uint8_t PIN_A = PIN_DO6_RESERVED;  // GPIO 16
+constexpr uint8_t PIN_B = PIN_DO7_RESERVED;  // GPIO 17
+
+// ----- Quadrature state machine (Gray-code decode) -------------------------
+//
+// State transitions: 4 states × 2 new pins → delta
+// Table index: (prev_state << 2) | new_ab
+// Value: +1 (CW), -1 (CCW), 0 (no move or invalid)
+//
+static const int8_t QEM[16] = {
+//  AB=00  01  10  11
+      0,  -1,  +1,  0,   // prev=00
+     +1,   0,   0, -1,   // prev=01
+     -1,   0,   0, +1,   // prev=10
+      0,  +1,  -1,  0,   // prev=11
+};
+
+volatile int32_t g_pulse_count = 0;
+volatile uint8_t g_prev_state  = 0;
+
+portMUX_TYPE g_mux = portMUX_INITIALIZER_UNLOCKED;
+
+// Armed state
+volatile bool    g_armed        = false;
+volatile uint32_t g_arm_time_ms = 0;
+
+void IRAM_ATTR encoder_isr() {
+    uint8_t a = (uint8_t)digitalRead(PIN_A);
+    uint8_t b = (uint8_t)digitalRead(PIN_B);
+    uint8_t state = (a << 1) | b;
+    int8_t delta = QEM[(g_prev_state << 2) | state];
+    if (delta != 0) {
+        portENTER_CRITICAL_ISR(&g_mux);
+        g_pulse_count += delta;
+        portEXIT_CRITICAL_ISR(&g_mux);
+    }
+    g_prev_state = state;
+}
+
+void KnobTask(void* /*pv*/) {
+    AR_LOGI(TAG, "knob_encoder task started on core %d", xPortGetCoreID());
+
+    int32_t last_count = 0;
+
+    for (;;) {
+        const uint32_t now = millis();
+
+        // Auto-disarm after timeout.
+        portENTER_CRITICAL(&g_mux);
+        bool armed = g_armed;
+        if (armed && (now - g_arm_time_ms) > KNOB_ARM_TIMEOUT_MS) {
+            g_armed = false;
+            armed = false;
+            AR_LOGI(TAG, "knob auto-disarmed (timeout)");
+        }
+        portEXIT_CRITICAL(&g_mux);
+
+        portENTER_CRITICAL(&g_mux);
+        int32_t count = g_pulse_count;
+        portEXIT_CRITICAL(&g_mux);
+
+        int32_t delta = count - last_count;
+        last_count = count;
+
+        if (delta != 0 && armed && !modes::is_standby()) {
+            // Apply ±KNOB_STEP_DEG per pulse, normalised to 0..360.
+            float sp = pid::pid_outer_heading_setpoint_deg();
+            sp = fmodf(sp + (float)delta * KNOB_STEP_DEG + 360.0f, 360.0f);
+            pid::pid_outer_set_heading_setpoint_deg(sp);
+            AR_LOGD(TAG, "knob: delta=%d new_sp=%.1f", delta, sp);
+        }
+
+        vTaskDelay(pdMS_TO_TICKS(20));  // 50 Hz check rate
+    }
+}
+
+}  // namespace
+
+void knob_encoder_init() {
+    pinMode(PIN_A, INPUT_PULLUP);
+    pinMode(PIN_B, INPUT_PULLUP);
+    g_prev_state = (uint8_t)((digitalRead(PIN_A) << 1) | digitalRead(PIN_B));
+    attachInterrupt(digitalPinToInterrupt(PIN_A), encoder_isr, CHANGE);
+    attachInterrupt(digitalPinToInterrupt(PIN_B), encoder_isr, CHANGE);
+    AR_LOGI(TAG, "knob encoder on GPIO A=%d B=%d", PIN_A, PIN_B);
+}
+
+void knob_encoder_start_task() {
+    xTaskCreatePinnedToCore(KnobTask, "knob_enc",
+                            2048, nullptr,
+                            1,    // low priority
+                            nullptr,
+                            AR_TASK_CORE_COMMS);
+}
+
+void knob_encoder_set_armed(bool armed) {
+    portENTER_CRITICAL(&g_mux);
+    g_armed       = armed;
+    g_arm_time_ms = millis();
+    portEXIT_CRITICAL(&g_mux);
+    AR_LOGI(TAG, "knob %s", armed ? "ARMED" : "disarmed");
+}
+
+bool knob_encoder_is_armed() {
+    return g_armed;
+}
+
+}  // namespace arautopilot::hal
diff --git a/firmware/ar_autopilot_v1/src/hal/knob_encoder.h b/firmware/ar_autopilot_v1/src/hal/knob_encoder.h
new file mode 100644
index 0000000..7cf99f7
--- /dev/null
+++ b/firmware/ar_autopilot_v1/src/hal/knob_encoder.h
@@ -0,0 +1,49 @@
+// =============================================================================
+//  hal/knob_encoder.h -- Rotary encoder for heading knob (Sprint 7)
+// =============================================================================
+//
+//  A quadrature rotary encoder connected to GPIO pins drives heading setpoint
+//  changes. Clockwise rotation increases the setpoint by STEP_DEG per detent;
+//  counter-clockwise decreases it.
+//
+//  The encoder is only active when the pilot is engaged (any mode other than
+//  STANDBY). While disengaged, pulses are silently discarded.
+//
+//  The "knob arm" coil (COIL_CMD_KNOB_ARM via Modbus, addr 3) enables the
+//  knob for one KNOB_ARM_TIMEOUT_MS window. If no edge arrives within that
+//  window, the coil auto-clears.  This prevents unintended heading changes
+//  from vibration noise.
+//
+//  GPIO assignment (not on AR-NMEA-IO v1.0 main header -- uses DO6/DO7 pads
+//  repurposed as inputs in the commissioning firmware variant):
+//    PIN_KNOB_A = PIN_DO6_RESERVED (GPIO 16)
+//    PIN_KNOB_B = PIN_DO7_RESERVED (GPIO 17)
+//
+//  The interrupt handler uses a 4-state Gray-code decode table for noise
+//  immunity.
+// =============================================================================
+
+#pragma once
+
+#include <cstdint>
+
+namespace arautopilot::hal {
+
+constexpr float KNOB_STEP_DEG       = 1.0f;    ///< heading change per detent
+constexpr uint32_t KNOB_ARM_TIMEOUT_MS = 5000; ///< arm window before auto-disarm
+
+/// Initialise encoder GPIO and attach interrupts.
+/// Must be called from setup() after do_init().
+void knob_encoder_init();
+
+/// Start the knob processing task (low priority, Core 0).
+void knob_encoder_start_task();
+
+/// Set the armed state.  While armed the knob updates the heading setpoint.
+/// The coil write handler calls this.
+void knob_encoder_set_armed(bool armed);
+
+/// Return current armed state.
+bool knob_encoder_is_armed();
+
+}  // namespace arautopilot::hal
diff --git a/firmware/ar_autopilot_v1/src/hal/nvs_config.cpp b/firmware/ar_autopilot_v1/src/hal/nvs_config.cpp
new file mode 100644
index 0000000..c1629c3
--- /dev/null
+++ b/firmware/ar_autopilot_v1/src/hal/nvs_config.cpp
@@ -0,0 +1,121 @@
+// =============================================================================
+//  hal/nvs_config.cpp -- NVS-backed calibration store (Sprint 7)
+// =============================================================================
+
+#include "nvs_config.h"
+
+#include <nvs.h>
+#include <nvs_flash.h>
+#include <Arduino.h>
+
+#include "../system/ar_log.h"
+
+namespace arautopilot::hal {
+
+namespace {
+constexpr const char* TAG      = "AR/NVS";
+constexpr const char* NS       = "ar_cal";
+}  // namespace
+
+bool nvs_config_init() {
+    esp_err_t err = nvs_flash_init();
+    if (err == ESP_ERR_NVS_NO_FREE_PAGES ||
+        err == ESP_ERR_NVS_NEW_VERSION_FOUND) {
+        AR_LOGW(TAG, "NVS partition needs erase (err=0x%x) -- factory-resetting", err);
+        nvs_flash_erase();
+        err = nvs_flash_init();
+    }
+    if (err != ESP_OK) {
+        AR_LOGE(TAG, "nvs_flash_init failed: 0x%x", err);
+        return false;
+    }
+    AR_LOGI(TAG, "NVS initialised (namespace: %s)", NS);
+    return true;
+}
+
+CalibrationData nvs_config_load() {
+    CalibrationData cal;  // defaults in struct definition
+
+    nvs_handle_t h;
+    if (nvs_open(NS, NVS_READONLY, &h) != ESP_OK) {
+        AR_LOGI(TAG, "No calibration in NVS -- using factory defaults");
+        return cal;
+    }
+
+    // Helper lambdas: read or keep default on missing key.
+    auto get_i16 = [&](const char* key, int16_t& out) {
+        int16_t v;
+        if (nvs_get_i16(h, key, &v) == ESP_OK) out = v;
+    };
+    auto get_float = [&](const char* key, float& out) {
+        // NVS has no native float; store as uint32 via memcpy.
+        uint32_t raw;
+        if (nvs_get_u32(h, key, &raw) == ESP_OK) {
+            memcpy(&out, &raw, sizeof(float));
+        }
+    };
+    auto get_u8 = [&](const char* key, uint8_t& out) {
+        uint8_t v;
+        if (nvs_get_u8(h, key, &v) == ESP_OK) out = v;
+    };
+
+    get_i16("adc_port",  cal.adc_port);
+    get_i16("adc_stbd",  cal.adc_stbd);
+    get_float("rud_port", cal.rudder_port_deg);
+    get_float("rud_stbd", cal.rudder_stbd_deg);
+    get_float("ou_kp",    cal.outer_kp);
+    get_float("ou_ki",    cal.outer_ki);
+    get_float("ou_kd",    cal.outer_kd);
+    uint8_t comm = 0;
+    get_u8("commissioned", comm);
+    cal.commissioned = (comm == 1);
+
+    nvs_close(h);
+    AR_LOGI(TAG, "Calibration loaded (commissioned=%d adc=%d..%d)",
+            (int)cal.commissioned, cal.adc_port, cal.adc_stbd);
+    return cal;
+}
+
+bool nvs_config_save(const CalibrationData& cal) {
+    nvs_handle_t h;
+    if (nvs_open(NS, NVS_READWRITE, &h) != ESP_OK) {
+        AR_LOGE(TAG, "nvs_open for write failed");
+        return false;
+    }
+
+    auto put_float = [&](const char* key, float v) {
+        uint32_t raw;
+        memcpy(&raw, &v, sizeof(float));
+        nvs_set_u32(h, key, raw);
+    };
+
+    nvs_set_i16(h, "adc_port",  cal.adc_port);
+    nvs_set_i16(h, "adc_stbd",  cal.adc_stbd);
+    put_float("rud_port", cal.rudder_port_deg);
+    put_float("rud_stbd", cal.rudder_stbd_deg);
+    put_float("ou_kp",    cal.outer_kp);
+    put_float("ou_ki",    cal.outer_ki);
+    put_float("ou_kd",    cal.outer_kd);
+    nvs_set_u8(h, "commissioned", cal.commissioned ? 1u : 0u);
+
+    esp_err_t err = nvs_commit(h);
+    nvs_close(h);
+    if (err != ESP_OK) {
+        AR_LOGE(TAG, "nvs_commit failed: 0x%x", err);
+        return false;
+    }
+    AR_LOGI(TAG, "Calibration saved to NVS");
+    return true;
+}
+
+bool nvs_config_erase() {
+    nvs_handle_t h;
+    if (nvs_open(NS, NVS_READWRITE, &h) != ESP_OK) return false;
+    esp_err_t err = nvs_erase_all(h);
+    nvs_commit(h);
+    nvs_close(h);
+    AR_LOGW(TAG, "NVS namespace '%s' erased (factory reset)", NS);
+    return err == ESP_OK;
+}
+
+}  // namespace arautopilot::hal
diff --git a/firmware/ar_autopilot_v1/src/hal/nvs_config.h b/firmware/ar_autopilot_v1/src/hal/nvs_config.h
new file mode 100644
index 0000000..628a5a6
--- /dev/null
+++ b/firmware/ar_autopilot_v1/src/hal/nvs_config.h
@@ -0,0 +1,54 @@
+// =============================================================================
+//  hal/nvs_config.h -- NVS-backed calibration store (Sprint 7)
+// =============================================================================
+//
+//  Persists commissioning data to the ESP32 NVS (Non-Volatile Storage) under
+//  the namespace "ar_cal".
+//
+//  Keys written:
+//    "adc_port"   -- int16_t  raw ADC at full-port rudder limit
+//    "adc_stbd"   -- int16_t  raw ADC at full-stbd rudder limit
+//    "rud_port"   -- float    physical angle at port limit (deg, default -35)
+//    "rud_stbd"   -- float    physical angle at stbd limit (deg, default +35)
+//    "ou_kp"      -- float    outer-loop recommended Kp from commissioning
+//    "ou_ki"      -- float    outer-loop recommended Ki
+//    "ou_kd"      -- float    outer-loop recommended Kd
+//    "commissioned"-- uint8_t 1 if the unit has been commissioned
+//
+//  All reads/writes are synchronous and should only be called at startup or
+//  from a low-priority task (not the 50 Hz safety task).
+// =============================================================================
+
+#pragma once
+
+#include <cstdint>
+
+namespace arautopilot::hal {
+
+struct CalibrationData {
+    int16_t adc_port         = 0;       ///< raw ADC at port limit
+    int16_t adc_stbd         = 4095;    ///< raw ADC at stbd limit
+    float   rudder_port_deg  = -35.0f;  ///< physical port angle
+    float   rudder_stbd_deg  =  35.0f;  ///< physical stbd angle
+    float   outer_kp         = 1.0f;    ///< recommended outer Kp
+    float   outer_ki         = 0.0f;    ///< recommended outer Ki
+    float   outer_kd         = 0.0f;    ///< recommended outer Kd
+    bool    commissioned     = false;   ///< true once commissioning ran
+};
+
+/// Initialise the NVS namespace.  Must be called from setup() before any
+/// other nvs_config function.  Returns false if NVS flash is unrecoverable
+/// (factory reset required).
+bool nvs_config_init();
+
+/// Read calibration data from NVS.  Returns default values if the key is
+/// absent (first boot or factory-reset).
+CalibrationData nvs_config_load();
+
+/// Write calibration data to NVS.
+bool nvs_config_save(const CalibrationData& cal);
+
+/// Erase the entire "ar_cal" namespace (factory reset).
+bool nvs_config_erase();
+
+}  // namespace arautopilot::hal
diff --git a/firmware/ar_autopilot_v1/src/main.cpp b/firmware/ar_autopilot_v1/src/main.cpp
index 412948e..432dd74 100644
--- a/firmware/ar_autopilot_v1/src/main.cpp
+++ b/firmware/ar_autopilot_v1/src/main.cpp
@@ -23,6 +23,8 @@
 #include <esp_system.h>
 
 #include "hal/di_do.h"
+#include "hal/knob_encoder.h"
+#include "hal/nvs_config.h"
 #include "hal/pinout.h"
 #include "hal/rudder_actuator.h"
 #include "hal/rudder_sensor.h"
@@ -66,11 +68,27 @@ void setup() {
     // Initialise the pilot mode state machine (boots in STANDBY).
     arautopilot::modes::mode_init();
 
+    // NVS (non-volatile config + calibration).  Must be first HAL call.
+    arautopilot::hal::nvs_config_init();
+    const auto cal = arautopilot::hal::nvs_config_load();
+    if (cal.commissioned) {
+        AR_LOGI(TAG, "commissioned unit: adc %d..%d  outer Kp=%.3f",
+                cal.adc_port, cal.adc_stbd, cal.outer_kp);
+    } else {
+        AR_LOGW(TAG, "not commissioned -- using factory defaults");
+    }
+
     // Initialise hardware abstraction layer.
     arautopilot::hal::di_init();
     arautopilot::hal::do_init();
     arautopilot::hal::rudder_sensor_init();
+    if (cal.commissioned) {
+        arautopilot::hal::rudder_sensor_set_calibration(
+            cal.adc_port, cal.adc_stbd,
+            cal.rudder_port_deg, cal.rudder_stbd_deg);
+    }
     arautopilot::hal::rudder_actuator_init();
+    arautopilot::hal::knob_encoder_init();
 
     // Safety: watchdog + DI override task. Initialised first so the
     // watchdog is armed before slower subsystems come up.
@@ -86,15 +104,21 @@ void setup() {
 
     arautopilot::safety::safety_monitor_start_task();
     arautopilot::hal::rudder_sensor_start_task();
+    arautopilot::hal::knob_encoder_start_task();
 
     // PID inner loop (Sprint 2). Active only when not in STANDBY and
     // rudder sensor reading is valid; refuses internally otherwise.
     arautopilot::pid::pid_inner_task_init();
     arautopilot::pid::pid_inner_task_start();
 
-    // PID outer loop (Sprint 3) -- Heading Hold. Only writes to the inner
-    // loop's setpoint when current mode == HEADING_HOLD.
+    // PID outer loop (Sprint 3) -- Heading Hold.
     arautopilot::pid::pid_outer_task_init();
+    if (cal.commissioned && cal.outer_kp > 0.0f) {
+        arautopilot::pid::pid_outer_update_gains(
+            cal.outer_kp, cal.outer_ki, cal.outer_kd);
+        AR_LOGI(TAG, "applied commissioned outer gains Kp=%.3f Ki=%.3f Kd=%.3f",
+                cal.outer_kp, cal.outer_ki, cal.outer_kd);
+    }
     arautopilot::pid::pid_outer_task_start();
 
     ar_start_heartbeat_task();
diff --git a/firmware/ar_autopilot_v1/src/protocols/modbus_slave.cpp b/firmware/ar_autopilot_v1/src/protocols/modbus_slave.cpp
index 0ca7304..70038a6 100644
--- a/firmware/ar_autopilot_v1/src/protocols/modbus_slave.cpp
+++ b/firmware/ar_autopilot_v1/src/protocols/modbus_slave.cpp
@@ -33,6 +33,7 @@
 #include "../system/task_config.h"
 #include "modbus_registers.h"
 #include "nmea2000_consumer.h"
+#include "../hal/knob_encoder.h"
 #include "../safety/safety_monitor.h"
 
 namespace arautopilot::protocols::modbus {
@@ -461,6 +462,7 @@ Modbus::Error write_coil(uint16_t addr, bool value) {
             return Modbus::Error::SUCCESS;
         case COIL_CMD_KNOB_ARM:
             g_coils.knob_arm = value;
+            hal::knob_encoder_set_armed(value);
             return Modbus::Error::SUCCESS;
         default:
             return Modbus::Error::ILLEGAL_DATA_ADDRESS;