core: per-profile ViGEm axis routing with unipolar output mode

RioProfile gains a nullable AxisRouting section mapping each calibrated
axis (X/Y/Z/Rx/Ry/Rz) to a pad target (thumbs, triggers, or None) with a
Centered or UnipolarPositive conversion; the default reproduces the old
hardcoded routing exactly, so existing profiles are untouched. Routing
resolution lives in a pure, ViGEm-free AxisRouter for testability; the
sink neutralizes the pad on routing change so stale trigger state cannot
leak across profile switches.

Motivation: Descent reads the pad via SDL GameController, where the
triggers are its stock fire axis-buttons - the old fixed routing put
throttle on LeftTrigger (fires) and detent would have read as full
reverse. descent-d1x.json now routes Z->RightThumbY (UnipolarPositive,
detent = center) and Rz->RightThumbX, triggers untargeted; guarded by
tests that parse the shipped JSON through the real deserializer and
byte-compare the dxx-rebirth reference copy.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/PLAN.md

@@ -206,6 +206,21 @@ Core logic in `src/RioJoy.Core/Profiles` + `RioRuntime`; UI/OS in `src/RioJoy.Tr
 - Joystick output now uses the real `HidFeederJoystickSink` when the driver is
   present (verified end-to-end); `NullJoystickSink` remains only as the
   no-driver fallback.
+- **Per-profile ViGEm axis routing — code-complete ✅.** `RioProfile.AxisRouting`
+  (`Output/AxisRoutingConfig`: one route per calibrated axis = pad target —
+  four thumbs, two triggers, or None — + output mode; shared types with no
+  ViGEm references, so net40 keeps compiling) re-routes the six axes on the
+  Xbox 360 pad. Modes: `Centered` (legacy bipolar) and `UnipolarPositive`
+  (calibrated 0 → thumb center — for the ratcheted unipolar throttle). Null/
+  absent = the historical fixed routing, so existing profiles are untouched.
+  Resolution + conversion is the pure unit-tested `AxisRouter`;
+  `ViGEmJoystickSink.SetRouting` applies it thread-safely and neutralizes all
+  thumbs/triggers each profile switch (no stale axes); wired in
+  `RioCoordinator.Activate` beside the calibrator config. First consumer:
+  `profiles/descent-d1x.json` (throttle→RightThumbY unipolar, rudder→
+  RightThumbX, triggers untouched — DXX fires on the LT/RT axis-buttons).
+  The HID feeder (native 6-axis report) intentionally ignores routing.
+  ⏳ Remaining: on-cabinet throttle/rudder feel check (first Descent flight).
 - ⏳ **Remaining:** full on-cabinet verification of the auto-switch +
   acquire/release lifecycle against real RIO hardware.
 

profiles/descent-d1x.json

@@ -15,6 +15,32 @@
     "InvertZR": false,
     "EnableZR": true
   },
+  "AxisRouting": {
+    "X": {
+      "Target": "LeftThumbX",
+      "Mode": "Centered"
+    },
+    "Y": {
+      "Target": "LeftThumbY",
+      "Mode": "Centered"
+    },
+    "Z": {
+      "Target": "RightThumbY",
+      "Mode": "UnipolarPositive"
+    },
+    "Rx": {
+      "Target": "None",
+      "Mode": "Centered"
+    },
+    "Ry": {
+      "Target": "None",
+      "Mode": "Centered"
+    },
+    "Rz": {
+      "Target": "RightThumbX",
+      "Mode": "Centered"
+    }
+  },
   "Buttons": {
     "16": 32822,
     "17": 32823,

src/RioJoy.Core/Output/AxisRouter.cs

@@ -0,0 +1,67 @@
+using RioJoy.Core.Calibration;
+
+namespace RioJoy.Core.Output;
+
+/// <summary>
+/// A resolved axis write: which pad control to drive and the converted value.
+/// <see cref="Value"/> is in the thumb range (<c>-32768..32767</c>) for thumb
+/// targets, the trigger range (<c>0..255</c>) for trigger targets, and 0 for
+/// <see cref="PadTarget.None"/> (nothing is written).
+/// </summary>
+public readonly struct ResolvedAxis
+{
+    public PadTarget Target { get; }
+
+    public int Value { get; }
+
+    public ResolvedAxis(PadTarget target, int value)
+    {
+        Target = target;
+        Value = value;
+    }
+
+    public override string ToString() => $"{Target}:{Value}";
+}
+
+/// <summary>
+/// Pure route-resolution + value-conversion for the ViGEm sink — no ViGEm types,
+/// so the decision logic is unit-testable without the bus driver.
+/// <see cref="ViGEmJoystickSink"/> translates the result into ViGEm calls.
+/// </summary>
+public static class AxisRouter
+{
+    /// <summary>
+    /// Resolve where the calibrated <paramref name="value"/> (<c>0..32766</c>,
+    /// center 16383) of <paramref name="axis"/> lands under
+    /// <paramref name="config"/>, and convert it for that target.
+    /// </summary>
+    public static ResolvedAxis Resolve(AxisRoutingConfig config, JoyAxis axis, int value)
+    {
+        if (config is null) throw new ArgumentNullException(nameof(config));
+
+        AxisRoute route = config.RouteFor(axis);
+        return route.Target switch
+        {
+            PadTarget.None => new ResolvedAxis(PadTarget.None, 0),
+            PadTarget.LeftTrigger or PadTarget.RightTrigger =>
+                new ResolvedAxis(route.Target, ToTrigger(value)),
+            _ => new ResolvedAxis(
+                route.Target,
+                route.Mode == AxisOutputMode.UnipolarPositive
+                    ? ToUnipolarThumb(value)
+                    : ToCenteredThumb(value)),
+        };
+    }
+
+    // RIO axis 0..32766 (centre 16383) -> Xbox thumb short -32768..32767 (legacy math).
+    private static int ToCenteredThumb(int value) =>
+        Compat.Net48Math.Clamp((value - AxisOutputs.Center) * 2, (int)short.MinValue, short.MaxValue);
+
+    // Unipolar RIO axis (rest = 0) -> upper thumb half: 0 -> center 0, 32766 -> max.
+    private static int ToUnipolarThumb(int value) =>
+        Compat.Net48Math.Clamp(value, 0, (int)short.MaxValue);
+
+    // RIO axis 0..32766 -> Xbox trigger byte 0..255 (legacy math).
+    private static int ToTrigger(int value) =>
+        Compat.Net48Math.Clamp(value * 255 / AxisOutputs.Max, 0, 255);
+}

src/RioJoy.Core/Output/AxisRoutingConfig.cs

@@ -0,0 +1,82 @@
+using RioJoy.Core.Calibration;
+
+namespace RioJoy.Core.Output;
+
+/// <summary>
+/// Where a calibrated axis lands on the virtual Xbox 360 pad. Our own enum (no
+/// ViGEm types — these are shared config types, serialized into profiles and
+/// compiled for net40 too); <see cref="ViGEmJoystickSink"/> translates to the
+/// ViGEm equivalents. <see cref="None"/> = the axis is not emitted at all.
+/// </summary>
+public enum PadTarget
+{
+    LeftThumbX,
+    LeftThumbY,
+    RightThumbX,
+    RightThumbY,
+    LeftTrigger,
+    RightTrigger,
+    None,
+}
+
+/// <summary>
+/// How a calibrated axis value (<c>0..32766</c>, center 16383) converts to a
+/// thumb-stick value. Meaningless for trigger targets (triggers always use the
+/// legacy <c>value*255/32766</c> byte conversion).
+/// </summary>
+public enum AxisOutputMode
+{
+    /// <summary>Legacy bipolar mapping: <c>(value - 16383) * 2</c> → center 16383 = thumb 0.</summary>
+    Centered,
+
+    /// <summary>
+    /// Unipolar mapping for axes whose calibrated rest is 0 (the ratcheted
+    /// throttle): <c>clamp(value, 0, 32767)</c> → calibrated 0 = thumb center 0,
+    /// 32766 = thumb max. Only the upper half of the thumb range is used.
+    /// </summary>
+    UnipolarPositive,
+}
+
+/// <summary>One axis route: which pad control it drives, and how the value converts.</summary>
+public sealed record AxisRoute
+{
+    public PadTarget Target { get; init; } = PadTarget.None;
+
+    public AxisOutputMode Mode { get; init; } = AxisOutputMode.Centered;
+}
+
+/// <summary>
+/// Per-profile routing of the six calibrated axes onto the ViGEm Xbox 360 pad
+/// (<see cref="RioJoy.Core.Profiles.RioProfile.AxisRouting"/>; null there = this
+/// default). The defaults reproduce the historical hardcoded sink routing
+/// exactly — X→LeftThumbX, Y→LeftThumbY, Rx→RightThumbX, Ry→RightThumbY,
+/// Z→LeftTrigger, Rz→RightTrigger, all <see cref="AxisOutputMode.Centered"/> —
+/// so existing profiles behave identically. Two axes routed to the same target
+/// are not arbitrated: the last <c>SetAxis</c> write wins.
+/// </summary>
+public sealed record AxisRoutingConfig
+{
+    public AxisRoute X { get; init; } = new() { Target = PadTarget.LeftThumbX };
+
+    public AxisRoute Y { get; init; } = new() { Target = PadTarget.LeftThumbY };
+
+    public AxisRoute Z { get; init; } = new() { Target = PadTarget.LeftTrigger };
+
+    public AxisRoute Rx { get; init; } = new() { Target = PadTarget.RightThumbX };
+
+    public AxisRoute Ry { get; init; } = new() { Target = PadTarget.RightThumbY };
+
+    public AxisRoute Rz { get; init; } = new() { Target = PadTarget.RightTrigger };
+
+    /// <summary>The route for <paramref name="axis"/>.</summary>
+    public AxisRoute RouteFor(JoyAxis axis) => axis switch
+    {
+        JoyAxis.X => X,
+        JoyAxis.Y => Y,
+        JoyAxis.Z => Z,
+        JoyAxis.Rx => Rx,
+        JoyAxis.Ry => Ry,
+        JoyAxis.Rz => Rz,
+        _ => new AxisRoute(), // unknown axis → None (not emitted)
+    };
+}

src/RioJoy.Core/Output/ViGEmJoystickSink.cs

@@ -38,6 +38,7 @@ public sealed class ViGEmJoystickSink : IJoystickSink, IDisposable
     private readonly ViGEmClient _client;
     private readonly IXbox360Controller _pad;
     private readonly object _gate = new();
+    private AxisRoutingConfig _routing = new();
 
     private ViGEmJoystickSink(ViGEmClient client, IXbox360Controller pad)
     {
@@ -45,6 +46,28 @@ public sealed class ViGEmJoystickSink : IJoystickSink, IDisposable
         _pad = pad;
     }
 
+    /// <summary>
+    /// Apply a per-profile axis routing (<see langword="null"/> = the default
+    /// legacy routing) and neutralize the pad's axis state — all four thumb axes
+    /// to 0 and both triggers to 0 in one report — so values written under the
+    /// previous routing cannot persist across a profile switch. Thread-safe.
+    /// Two axes routed to the same target are not arbitrated: last writer wins.
+    /// </summary>
+    public void SetRouting(AxisRoutingConfig? routing)
+    {
+        lock (_gate)
+        {
+            _routing = routing ?? new AxisRoutingConfig();
+            _pad.SetAxisValue(Xbox360Axis.LeftThumbX, 0);
+            _pad.SetAxisValue(Xbox360Axis.LeftThumbY, 0);
+            _pad.SetAxisValue(Xbox360Axis.RightThumbX, 0);
+            _pad.SetAxisValue(Xbox360Axis.RightThumbY, 0);
+            _pad.SetSliderValue(Xbox360Slider.LeftTrigger, 0);
+            _pad.SetSliderValue(Xbox360Slider.RightTrigger, 0);
+            _pad.SubmitReport();
+        }
+    }
+
     /// <summary>
     /// Try to connect to ViGEmBus and create a virtual Xbox 360 controller. Returns
     /// <see langword="false"/> if ViGEmBus is not installed, so callers can fall back
@@ -94,32 +117,27 @@ public sealed class ViGEmJoystickSink : IJoystickSink, IDisposable
         }
     }
 
+    // Routing + conversion live in the pure AxisRouter (unit-tested without the
+    // bus); this method only translates the resolved target into ViGEm calls.
     public void SetAxis(JoyAxis axis, int value)
     {
         lock (_gate)
         {
-            switch (axis)
+            ResolvedAxis resolved = AxisRouter.Resolve(_routing, axis, value);
+            switch (resolved.Target)
             {
-                case JoyAxis.X: _pad.SetAxisValue(Xbox360Axis.LeftThumbX, ToThumb(value)); break;
-                case JoyAxis.Y: _pad.SetAxisValue(Xbox360Axis.LeftThumbY, ToThumb(value)); break;
-                case JoyAxis.Rx: _pad.SetAxisValue(Xbox360Axis.RightThumbX, ToThumb(value)); break;
-                case JoyAxis.Ry: _pad.SetAxisValue(Xbox360Axis.RightThumbY, ToThumb(value)); break;
-                case JoyAxis.Z: _pad.SetSliderValue(Xbox360Slider.LeftTrigger, ToTrigger(value)); break;
-                case JoyAxis.Rz: _pad.SetSliderValue(Xbox360Slider.RightTrigger, ToTrigger(value)); break;
-                default: return;
+                case PadTarget.LeftThumbX: _pad.SetAxisValue(Xbox360Axis.LeftThumbX, (short)resolved.Value); break;
+                case PadTarget.LeftThumbY: _pad.SetAxisValue(Xbox360Axis.LeftThumbY, (short)resolved.Value); break;
+                case PadTarget.RightThumbX: _pad.SetAxisValue(Xbox360Axis.RightThumbX, (short)resolved.Value); break;
+                case PadTarget.RightThumbY: _pad.SetAxisValue(Xbox360Axis.RightThumbY, (short)resolved.Value); break;
+                case PadTarget.LeftTrigger: _pad.SetSliderValue(Xbox360Slider.LeftTrigger, (byte)resolved.Value); break;
+                case PadTarget.RightTrigger: _pad.SetSliderValue(Xbox360Slider.RightTrigger, (byte)resolved.Value); break;
+                default: return; // PadTarget.None — the axis is not emitted
             }
             _pad.SubmitReport();
         }
     }
 
-    // RIO axis 0..32766 (centre 16383) -> Xbox thumb short -32768..32767.
-    private static short ToThumb(int value) =>
-        (short)RioJoy.Core.Compat.Net48Math.Clamp((value - AxisOutputs.Center) * 2, short.MinValue, short.MaxValue);
-
-    // RIO axis 0..32766 -> Xbox trigger byte 0..255.
-    private static byte ToTrigger(int value) =>
-        (byte)RioJoy.Core.Compat.Net48Math.Clamp(value * 255 / AxisOutputs.Max, 0, 255);
-
     public void Dispose()
     {
         try { _pad.Disconnect(); } catch { /* already disconnected / bus gone */ }

src/RioJoy.Core/Profiles/RioProfile.cs

@@ -1,5 +1,6 @@
 using RioJoy.Core.Calibration;
 using RioJoy.Core.Mapping;
+using RioJoy.Core.Output;
 
 namespace RioJoy.Core.Profiles;
 
@@ -29,6 +30,14 @@ public sealed class RioProfile
     /// <summary>Axis calibration / invert options.</summary>
     public AxisCalibrationConfig Calibration { get; set; } = new();
 
+    /// <summary>
+    /// How the six calibrated axes route onto the ViGEm Xbox 360 pad; null =
+    /// the default <see cref="AxisRoutingConfig"/> (the historical fixed
+    /// routing). Ignored by the RioGamepad HID feeder, whose native 6-axis
+    /// report needs no routing.
+    /// </summary>
+    public AxisRoutingConfig? AxisRouting { get; set; }
+
     /// <summary>Plasma greeting text shown on load (null = leave display as-is).</summary>
     public string? PlasmaGreeting { get; set; }
 

src/RioJoy.Tray/RioCoordinator.cs

@@ -199,6 +199,13 @@ public sealed class RioCoordinator : IDisposable
             IJoystickSink joystick;
             string note;
             IJoystickSink realJoystick = CreateJoystickSink(out string joystickNote);
+#if !NET40
+            // Per-profile ViGEm axis routing, applied the same way the profile's
+            // Calibration reaches the AxisCalibrator below (null = default legacy
+            // routing). Also neutralizes the pad so nothing persists across a switch.
+            if (realJoystick is ViGEmJoystickSink vigemPad)
+                vigemPad.SetRouting(profile.AxisRouting);
+#endif
             if (!routeInput)
             {
                 // Keyboard/mouse + joystick are gated off while editing so the RIO can

tests/RioJoy.Core.Tests/Output/AxisRouterTests.cs

@@ -0,0 +1,130 @@
+using RioJoy.Core.Calibration;
+using RioJoy.Core.Output;
+using Xunit;
+
+namespace RioJoy.Core.Tests.Output;
+
+public class AxisRouterTests
+{
+    // --- Default routing reproduces the legacy hardcoded sink exactly --------
+
+    [Theory]
+    [InlineData(JoyAxis.X, PadTarget.LeftThumbX)]
+    [InlineData(JoyAxis.Y, PadTarget.LeftThumbY)]
+    [InlineData(JoyAxis.Rx, PadTarget.RightThumbX)]
+    [InlineData(JoyAxis.Ry, PadTarget.RightThumbY)]
+    public void Default_ThumbAxes_UseLegacyCenteredMath(JoyAxis axis, PadTarget expected)
+    {
+        var config = new AxisRoutingConfig();
+
+        // Legacy ToThumb: (value - 16383) * 2, clamped to the short range.
+        ResolvedAxis min = AxisRouter.Resolve(config, axis, 0);
+        Assert.Equal(expected, min.Target);
+        Assert.Equal(-32766, min.Value);
+
+        Assert.Equal(0, AxisRouter.Resolve(config, axis, AxisOutputs.Center).Value);
+        Assert.Equal(32766, AxisRouter.Resolve(config, axis, AxisOutputs.Max).Value);
+    }
+
+    [Theory]
+    [InlineData(JoyAxis.Z, PadTarget.LeftTrigger)]
+    [InlineData(JoyAxis.Rz, PadTarget.RightTrigger)]
+    public void Default_TriggerAxes_UseLegacyTriggerMath(JoyAxis axis, PadTarget expected)
+    {
+        var config = new AxisRoutingConfig();
+
+        // Legacy ToTrigger: value * 255 / 32766, clamped to the byte range.
+        ResolvedAxis rest = AxisRouter.Resolve(config, axis, 0);
+        Assert.Equal(expected, rest.Target);
+        Assert.Equal(0, rest.Value);
+
+        Assert.Equal(127, AxisRouter.Resolve(config, axis, AxisOutputs.Center).Value);
+        Assert.Equal(255, AxisRouter.Resolve(config, axis, AxisOutputs.Max).Value);
+    }
+
+    [Fact]
+    public void Default_CenteredThumb_ClampsToShortRange()
+    {
+        var config = new AxisRoutingConfig();
+
+        // (40000 - 16383) * 2 = 47234 → clamped to short.MaxValue.
+        Assert.Equal(32767, AxisRouter.Resolve(config, JoyAxis.X, 40000).Value);
+        // (-2000 - 16383) * 2 = -36766 → clamped to short.MinValue.
+        Assert.Equal(-32768, AxisRouter.Resolve(config, JoyAxis.X, -2000).Value);
+    }
+
+    // --- UnipolarPositive: clamp(value, 0, 32767) ----------------------------
+
+    [Fact]
+    public void UnipolarPositive_MapsCalibratedZeroToThumbCenter()
+    {
+        var config = new AxisRoutingConfig
+        {
+            Z = new AxisRoute { Target = PadTarget.RightThumbY, Mode = AxisOutputMode.UnipolarPositive },
+        };
+
+        Assert.Equal(0, AxisRouter.Resolve(config, JoyAxis.Z, 0).Value);          // detent → center
+        Assert.Equal(16383, AxisRouter.Resolve(config, JoyAxis.Z, 16383).Value);  // half → half up
+        Assert.Equal(32766, AxisRouter.Resolve(config, JoyAxis.Z, AxisOutputs.Max).Value); // full → max (32766 of 32767)
+        Assert.Equal(0, AxisRouter.Resolve(config, JoyAxis.Z, -5).Value);         // clamps below
+        Assert.Equal(32767, AxisRouter.Resolve(config, JoyAxis.Z, 40000).Value);  // clamps above
+    }
+
+    [Fact]
+    public void UnipolarPositive_OnTriggerTarget_IsIgnored_TriggerMathApplies()
+    {
+        // Mode is meaningless for trigger targets — they keep the trigger byte math.
+        var config = new AxisRoutingConfig
+        {
+            Z = new AxisRoute { Target = PadTarget.LeftTrigger, Mode = AxisOutputMode.UnipolarPositive },
+        };
+
+        Assert.Equal(255, AxisRouter.Resolve(config, JoyAxis.Z, AxisOutputs.Max).Value);
+    }
+
+    // --- None: the axis is not emitted ---------------------------------------
+
+    [Fact]
+    public void NoneTarget_EmitsNothing()
+    {
+        var config = new AxisRoutingConfig
+        {
+            Rx = new AxisRoute { Target = PadTarget.None },
+        };
+
+        ResolvedAxis r = AxisRouter.Resolve(config, JoyAxis.Rx, 12345);
+        Assert.Equal(PadTarget.None, r.Target);
+        Assert.Equal(0, r.Value);
+    }
+
+    // --- The Descent shape ----------------------------------------------------
+
+    [Fact]
+    public void DescentConfig_ThrottleToRightThumbY_TriggersUntargeted()
+    {
+        // profiles/descent-d1x.json: DXX's stock GameController defaults fire on
+        // the LT/RT axis-buttons, so no axis may land on a trigger.
+        var config = new AxisRoutingConfig
+        {
+            Z = new AxisRoute { Target = PadTarget.RightThumbY, Mode = AxisOutputMode.UnipolarPositive },
+            Rz = new AxisRoute { Target = PadTarget.RightThumbX },
+            Rx = new AxisRoute { Target = PadTarget.None },
+            Ry = new AxisRoute { Target = PadTarget.None },
+        };
+
+        ResolvedAxis z = AxisRouter.Resolve(config, JoyAxis.Z, 16383);
+        Assert.Equal(PadTarget.RightThumbY, z.Target);
+        Assert.Equal(16383, z.Value); // unipolar: half throttle → half deflection up
+
+        ResolvedAxis rz = AxisRouter.Resolve(config, JoyAxis.Rz, AxisOutputs.Center);
+        Assert.Equal(PadTarget.RightThumbX, rz.Target);
+        Assert.Equal(0, rz.Value); // rudder stays bipolar: center → thumb 0
+
+        foreach (JoyAxis axis in new[] { JoyAxis.X, JoyAxis.Y, JoyAxis.Z, JoyAxis.Rx, JoyAxis.Ry, JoyAxis.Rz })
+        {
+            PadTarget target = AxisRouter.Resolve(config, axis, AxisOutputs.Center).Target;
+            Assert.NotEqual(PadTarget.LeftTrigger, target);
+            Assert.NotEqual(PadTarget.RightTrigger, target);
+        }
+    }
+}

tests/RioJoy.Core.Tests/Profiles/ConfigStoreTests.cs

@@ -1,4 +1,5 @@
 using RioJoy.Core.Calibration;
+using RioJoy.Core.Output;
 using RioJoy.Core.Profiles;
 using Xunit;
 
@@ -45,6 +46,98 @@ public class ConfigStoreTests
         Assert.Equal(new[] { "doom.exe" }, p.MatchExecutables);
     }
 
+    [Fact]
+    public void RoundTrips_AxisRouting_WithStringEnums()
+    {
+        var config = new AppConfig
+        {
+            Profiles =
+            {
+                new RioProfile
+                {
+                    Name = "Descent",
+                    AxisRouting = new AxisRoutingConfig
+                    {
+                        Z = new AxisRoute { Target = PadTarget.RightThumbY, Mode = AxisOutputMode.UnipolarPositive },
+                        Rz = new AxisRoute { Target = PadTarget.RightThumbX },
+                        Rx = new AxisRoute { Target = PadTarget.None },
+                        Ry = new AxisRoute { Target = PadTarget.None },
+                    },
+                },
+            },
+        };
+
+        string json = ConfigStore.Serialize(config);
+        Assert.Contains("\"RightThumbY\"", json);       // enums serialize as strings
+        Assert.Contains("\"UnipolarPositive\"", json);  // (house StringEnumConverter convention)
+
+        RioProfile back = Assert.Single(ConfigStore.Deserialize(json).Profiles);
+        Assert.Equal(config.Profiles[0].AxisRouting, back.AxisRouting); // record value equality
+        Assert.Equal(PadTarget.LeftThumbX, back.AxisRouting!.X.Target); // untouched routes keep defaults
+    }
+
+    [Fact]
+    public void AxisRouting_Unset_StaysNull_AndOffJson()
+    {
+        // null = default routing; NullValueHandling.Ignore keeps it out of the JSON,
+        // so pre-existing profiles on disk are byte-compatible.
+        string json = ConfigStore.Serialize(new AppConfig { Profiles = { new RioProfile { Name = "P" } } });
+        Assert.DoesNotContain("AxisRouting", json);
+        Assert.Null(Assert.Single(ConfigStore.Deserialize(json).Profiles).AxisRouting);
+    }
+
+    [Fact]
+    public void ShippedDescentProfile_ParsesWithDescentRouting_NoTriggerTargets()
+    {
+        // Guards the shipped fixture itself: Newtonsoft's default
+        // MissingMemberHandling.Ignore silently drops a misspelled property or axis
+        // name, which would fall back to the default routing and put the throttle
+        // back on LeftTrigger — the stock fire button in Descent's SDL
+        // GameController mapping. So parse the real file, not a C#-built config.
+        string json = File.ReadAllText(Path.Combine(TestRepo.Root(), "profiles", "descent-d1x.json"));
+
+        // The shipped file is a single-profile document users paste into the
+        // config's Profiles list; wrap it so it flows through the exact
+        // ConfigStore serializer settings.
+        RioProfile p = Assert.Single(ConfigStore.Deserialize($"{{\"Profiles\":[{json}]}}").Profiles);
+
+        Assert.Equal("Descent", p.Name);
+        Assert.True(p.Calibration.EnableZR); // pedal-differential rudder feeds Rz
+
+        Assert.NotNull(p.AxisRouting);
+        AxisRoutingConfig routing = p.AxisRouting!;
+        Assert.Equal(new AxisRoute { Target = PadTarget.LeftThumbX }, routing.X);
+        Assert.Equal(new AxisRoute { Target = PadTarget.LeftThumbY }, routing.Y);
+        Assert.Equal(new AxisRoute { Target = PadTarget.RightThumbY, Mode = AxisOutputMode.UnipolarPositive }, routing.Z);
+        Assert.Equal(new AxisRoute { Target = PadTarget.RightThumbX }, routing.Rz);
+        Assert.Equal(new AxisRoute { Target = PadTarget.None }, routing.Rx);
+        Assert.Equal(new AxisRoute { Target = PadTarget.None }, routing.Ry);
+
+        // No axis may resolve onto a trigger — triggers are Descent's fire buttons.
+        foreach (JoyAxis axis in new[] { JoyAxis.X, JoyAxis.Y, JoyAxis.Z, JoyAxis.Rx, JoyAxis.Ry, JoyAxis.Rz })
+        {
+            PadTarget target = AxisRouter.Resolve(routing, axis, AxisOutputs.Center).Target;
+            Assert.NotEqual(PadTarget.LeftTrigger, target);
+            Assert.NotEqual(PadTarget.RightTrigger, target);
+        }
+    }
+
+    [Fact]
+    public void ShippedDescentProfile_MatchesDxxRebirthReferenceCopy()
+    {
+        // The dxx-rebirth docs keep a reference copy of the Descent profile that
+        // must stay byte-identical to ours. The sibling checkout is a cabinet-
+        // machine convention, not a repo guarantee, so no-op quietly when the
+        // second repo is not checked out next to this one.
+        string reference = Path.GetFullPath(Path.Combine(
+            TestRepo.Root(), "..", "dxx-rebirth", "docs", "reference", "descent-riojoy-profile.json"));
+        if (!File.Exists(reference))
+            return;
+
+        string shipped = Path.Combine(TestRepo.Root(), "profiles", "descent-d1x.json");
+        Assert.Equal(File.ReadAllBytes(shipped), File.ReadAllBytes(reference));
+    }
+
     [Fact]
     public void Load_MissingFile_ReturnsDefaults()
     {