fix(input): Phase K live-test fixes pt3 — fly→chase round-trip, Shift coexists, run-speed for backward + strafe

Four issues from the K-fix2 launch (2026-04-26 user report):

1. Can't return from free-fly to player view.
   CameraController.ToggleFly only swaps Fly↔Orbit, so a user who
   flew out of player mode landed in orbit (Holtburg) on
   toggle-back instead of the chase camera. Added
   ToggleFlyOrChase() helper that prefers Fly→Chase /
   Chase→Fly when _playerMode is true and a chase camera is
   available; falls back to the original Fly↔Orbit toggle for
   offline / pre-login flows. Wired into all three free-fly
   entry points: keyboard shortcut (Ctrl+Shift+F), Camera menu
   item, and DebugPanel button.

2. Shift while moving STOPS instead of dropping to walk.
   Root cause: InputDispatcher.IsChordHeld required
   _keyboard.CurrentModifiers to match chord.Modifiers EXACTLY.
   So with W bound as (W, None), holding W and then pressing
   Shift made CurrentModifiers=Shift mismatch chord (None) →
   IsActionHeld(MovementForward) returned false → Forward flag
   dropped → player stopped. Fixed by relaxing IsChordHeld:
   when chord.Modifiers is None, Shift is allowed to coexist
   (it's the retail walk-modifier). Other modifiers
   (Ctrl, Alt, Win) still mismatch strictly so Ctrl+W stays a
   distinct chord from W.

   +2 tests pinning the new permissive-Shift / strict-Ctrl
   semantics.

3. Backwards too slow when running.
   forwardCmdSpeed for the WalkBackward branch was hardcoded
   to 1.0; localY was hardcoded to -(WalkAnimSpeed * 0.65).
   Neither honored input.Run. With Run=true (default),
   backward now scales by runRate (~2.4×) so X = "run
   backwards" matches the forward run pace × the 0.65
   backward animation cycle ratio.

4. Strafe too slow when running.
   localX for SideStepLeft / SideStepRight was hardcoded to
   ±SidestepAnimSpeed regardless of Run. Same fix: when Run
   is held, scale by runRate so strafe at default speed
   matches the run-forward pace.

Tests: 1220 → 1222 (the two new IsChordHeld tests).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.App/Input/PlayerMovementController.cs

@@ -272,8 +272,16 @@ public sealed class PlayerMovementController
         }
         else if (input.Backward)
         {
-            forwardCmd      = MotionCommand.WalkBackward;
-            forwardCmdSpeed = 1.0f;
+            forwardCmd = MotionCommand.WalkBackward;
+            // K-fix3 (2026-04-26): backward also honors Run. Without
+            // this, holding X with Run=true (default) still produced
+            // walk-tier backward speed because forwardCmdSpeed was
+            // hardcoded to 1.0. Now scale by runRate the same way
+            // RunForward does.
+            if (input.Run && _weenie.InqRunRate(out float runRateBack))
+                forwardCmdSpeed = runRateBack;
+            else
+                forwardCmdSpeed = 1.0f;
         }
         else
         {
@@ -307,16 +315,30 @@ public sealed class PlayerMovementController
             float localY = 0f;
             float localX = 0f;
 
+            // K-fix3 (2026-04-26): unified run-multiplier for backward
+            // + strafe. Forward already scales correctly because it uses
+            // stateVel.Y (which the motion state machine fed runRate
+            // into via DoMotion). Backward + strafe bypass the state
+            // machine and hardcoded speed; previously they capped at
+            // walk speed regardless of Run, which made the ~2.4×
+            // forward-vs-back/strafe ratio feel wrong. Now both scale
+            // with the same runRate the forward branch uses.
+            float runMul = 1.0f;
+            if (input.Run && _weenie.InqRunRate(out float vrr))
+                runMul = vrr;
+
             if (input.Forward)
                 localY =  stateVel.Y;
             else if (input.Backward)
-                localY = -(MotionInterpreter.WalkAnimSpeed * 0.65f);
+                localY = -(MotionInterpreter.WalkAnimSpeed * 0.65f * runMul);
 
-            // Full-speed strafe to match retail sidestep pace.
+            // Strafe scales with the same runMul so sidestep matches
+            // the forward pace at run speed (retail uses speed=1.0 for
+            // SideStep + the same hold-key-driven run/walk multiplier).
             if (input.StrafeRight)
-                localX =  MotionInterpreter.SidestepAnimSpeed;
+                localX =  MotionInterpreter.SidestepAnimSpeed * runMul;
             else if (input.StrafeLeft)
-                localX = -MotionInterpreter.SidestepAnimSpeed;
+                localX = -MotionInterpreter.SidestepAnimSpeed * runMul;
 
             _body.set_local_velocity(new Vector3(localX, localY, savedWorldVz));
         }

src/AcDream.App/Rendering/GameWindow.cs

@@ -885,14 +885,7 @@ public sealed class GameWindow : IDisposable
                 // auto-entry if the user opts out of player mode before
                 // it fires, so the chase camera doesn't snap on top of
                 // the fly camera mid-inspection.
-                _debugVm.ToggleFlyMode        = () =>
-                {
-                    // K.2: manual fly toggle pre-empts the auto-entry
-                    // trigger (user's choice wins). Cancel is no-op when
-                    // not yet armed.
-                    _playerModeAutoEntry?.Cancel();
-                    _cameraController?.ToggleFly();
-                };
+                _debugVm.ToggleFlyMode        = ToggleFlyOrChase;
                 _debugPanel = new AcDream.UI.Abstractions.Panels.Debug.DebugPanel(_debugVm);
                 _panelHost.Register(_debugPanel);
 
@@ -4348,10 +4341,7 @@ public sealed class GameWindow : IDisposable
                         string flyLabel = _cameraController.IsFlyMode
                             ? "Exit Free-Fly Mode" : "Enter Free-Fly Mode";
                         if (ImGuiNET.ImGui.MenuItem(flyLabel, "Ctrl+Shift+F"))
-                        {
-                            _playerModeAutoEntry?.Cancel();
-                            _cameraController.ToggleFly();
-                        }
+                            ToggleFlyOrChase();
                     }
                     ImGuiNET.ImGui.EndMenu();
                 }
@@ -5348,13 +5338,13 @@ public sealed class GameWindow : IDisposable
                 break;
 
             case AcDream.UI.Abstractions.Input.InputAction.AcdreamToggleFlyMode:
-                // K-fix2 (2026-04-26): manual fly toggle pre-empts the
-                // auto-entry trigger so the chase camera doesn't snap on
-                // top of the fly camera mid-inspection. Mirrors the
-                // DebugPanel "Toggle Free-Fly Mode" button + Camera menu
-                // entry.
-                _playerModeAutoEntry?.Cancel();
-                _cameraController?.ToggleFly();
+                // K-fix3 (2026-04-26): proper round-trip when player has
+                // an active chase camera. ToggleFly() only swaps
+                // Fly↔Orbit, so a user who flew out of player mode used
+                // to land in Holtburg-orbit on toggle-back. With a chase
+                // camera available, prefer Fly→Chase / Chase→Fly so the
+                // user round-trips back to the same player view.
+                ToggleFlyOrChase();
                 break;
 
             case AcDream.UI.Abstractions.Input.InputAction.AcdreamTogglePlayerMode:
@@ -5457,6 +5447,38 @@ public sealed class GameWindow : IDisposable
         }
     }
 
+    /// <summary>
+    /// K-fix3 (2026-04-26): the right "toggle free-fly mode" routine
+    /// when a chase camera is in play. <see cref="CameraController.ToggleFly"/>
+    /// only knows Fly↔Orbit and would strand a player-mode user in the
+    /// orbit camera (Holtburg view) when they exit fly. This wrapper
+    /// gives the round-trip the user actually wants:
+    /// <list type="bullet">
+    /// <item>Chase → Fly: cancel auto-entry (user's choice wins) and
+    /// switch to fly camera while keeping <c>_playerMode = true</c> +
+    /// the chase camera alive so we can return.</item>
+    /// <item>Fly → Chase: when <c>_playerMode</c> is still true and the
+    /// chase camera survived, re-enter chase via
+    /// <see cref="CameraController.EnterChaseMode"/>.</item>
+    /// <item>Otherwise (no chase available): the original Fly↔Orbit
+    /// toggle for offline / pre-login flows.</item>
+    /// </list>
+    /// </summary>
+    private void ToggleFlyOrChase()
+    {
+        if (_cameraController is null) return;
+        _playerModeAutoEntry?.Cancel();
+
+        if (_cameraController.IsFlyMode
+            && _playerMode
+            && _chaseCamera is not null)
+        {
+            _cameraController.EnterChaseMode(_chaseCamera);
+            return;
+        }
+        _cameraController.ToggleFly();
+    }
+
     /// <summary>
     /// K.2: shared "construct controller + chase camera + enter chase
     /// mode" body extracted from the on-enter branch of

src/AcDream.UI.Abstractions/Input/InputDispatcher.cs

@@ -142,8 +142,18 @@ public sealed class InputDispatcher
 
     /// <summary>True iff the given chord's primary key is currently down on
     /// the appropriate device AND the keyboard's current modifier mask
-    /// equals the chord's required modifier mask exactly. Modifiers must
-    /// match precisely — Ctrl+A held does NOT count Shift+Ctrl+A as held.</summary>
+    /// matches the chord's required modifier mask. Match semantics:
+    /// <list type="bullet">
+    /// <item>If <see cref="KeyChord.Modifiers"/> is <see cref="ModifierMask.None"/>,
+    /// any Shift state is allowed — Shift is the retail walk-modifier and
+    /// must coexist with movement chords (W held + Shift pressed = run
+    /// gracefully drops to walk, not "stop"). Other modifiers
+    /// (Ctrl, Alt, Win) still mismatch strictly so Ctrl+W stays a
+    /// distinct chord.</item>
+    /// <item>If <see cref="KeyChord.Modifiers"/> includes any non-Shift
+    /// modifier (or includes Shift explicitly), the match is exact —
+    /// Ctrl+A held does NOT count Shift+Ctrl+A as held.</item>
+    /// </list></summary>
     private bool IsChordHeld(KeyChord chord)
     {
         if (chord.Device == 0)
@@ -160,7 +170,14 @@ public sealed class InputDispatcher
             // Unknown device — never held.
             return false;
         }
-        return _keyboard.CurrentModifiers == chord.Modifiers;
+        var current = _keyboard.CurrentModifiers;
+        if (chord.Modifiers == ModifierMask.None)
+        {
+            // K-fix3 (2026-04-26): permissive Shift handling for bare-key
+            // chords. See the XML doc above for rationale.
+            current &= ~ModifierMask.Shift;
+        }
+        return current == chord.Modifiers;
     }
 
     /// <summary>Inverse of <see cref="MouseButtonToKey"/>: decode a chord

tests/AcDream.UI.Abstractions.Tests/Input/InputDispatcherIsActionHeldTests.cs

@@ -106,6 +106,47 @@ public class InputDispatcherIsActionHeldTests
         Assert.False(dispatcher.IsActionHeld(InputAction.None));
     }
 
+    [Fact]
+    public void IsActionHeld_None_chord_remains_held_when_user_adds_Shift()
+    {
+        // K-fix3 (2026-04-26): Shift is the walk modifier in retail AC.
+        // The user holding W (default = run) and then pressing Shift
+        // should drop them to walk speed, NOT stop forward motion. Prior
+        // to this fix, IsChordHeld required CurrentModifiers to match
+        // chord.Modifiers EXACTLY — so (W, None) failed to match while
+        // CurrentModifiers=Shift, and the player stopped on Shift-press.
+        // Now: when chord requires no modifiers, Shift is allowed to
+        // coexist (other modifiers — Ctrl, Alt, Win — still mismatch).
+        var (dispatcher, kb, _, bindings) = Build();
+        bindings.Add(new Binding(new KeyChord(Key.W, ModifierMask.None), InputAction.MovementForward));
+
+        kb.EmitKeyDown(Key.W, ModifierMask.None);
+        Assert.True(dispatcher.IsActionHeld(InputAction.MovementForward));
+
+        // User now holds Shift while still holding W. CurrentModifiers
+        // becomes Shift; W is still physically down.
+        kb.CurrentModifiers = ModifierMask.Shift;
+        Assert.True(dispatcher.IsActionHeld(InputAction.MovementForward));
+    }
+
+    [Fact]
+    public void IsActionHeld_None_chord_does_not_fire_when_user_adds_Ctrl()
+    {
+        // Counterpart to the Shift test above: Ctrl is NOT a movement
+        // modifier, so Ctrl+W should be a different chord. Without an
+        // explicit (W, Ctrl) binding the action stays inactive — that's
+        // what makes Ctrl+F* / Ctrl+1-9 / etc. distinct from the bare
+        // F* / 1-9 chords.
+        var (dispatcher, kb, _, bindings) = Build();
+        bindings.Add(new Binding(new KeyChord(Key.W, ModifierMask.None), InputAction.MovementForward));
+
+        kb.EmitKeyDown(Key.W, ModifierMask.None);
+        Assert.True(dispatcher.IsActionHeld(InputAction.MovementForward));
+
+        kb.CurrentModifiers = ModifierMask.Ctrl;
+        Assert.False(dispatcher.IsActionHeld(InputAction.MovementForward));
+    }
+
     [Fact]
     public void IsActionHeld_does_not_check_WantCaptureMouse()
     {