diff --git a/src/AcDream.App/Input/PlayerMovementController.cs b/src/AcDream.App/Input/PlayerMovementController.cs
index 0c638a7..205f35e 100644
--- a/src/AcDream.App/Input/PlayerMovementController.cs
+++ b/src/AcDream.App/Input/PlayerMovementController.cs
@@ -31,7 +31,8 @@ public readonly record struct MovementResult(
     uint? TurnCommand,
     float? ForwardSpeed,
     float? SidestepSpeed,
-    float? TurnSpeed);
+    float? TurnSpeed,
+    float? JumpExtent = null);  // non-null when a jump was triggered this frame
 
 /// <summary>
 /// Portal-space state for the player movement controller.
@@ -94,6 +95,11 @@ public sealed class PlayerMovementController
     /// </summary>
     public float VerticalVelocity => _body.Velocity.Z;
 
+    // Jump charge state.
+    private bool _jumpCharging;
+    private float _jumpExtent;
+    private const float JumpChargeRate = 1.0f; // 0→1 over 1 second
+
     // Previous frame's motion commands for change detection.
     private uint? _prevForwardCmd;
     private uint? _prevSidestepCmd;
@@ -246,15 +252,33 @@ public sealed class PlayerMovementController
         // Rotation about Z does not affect the Z component, so world Vz == local Vz.
         _body.set_local_velocity(new Vector3(localX, localY, savedWorldVz));
 
-        // ── 3. Jump ───────────────────────────────────────────────────────────
-        if (input.Jump)
+        // ── 3. Jump (charged) ─────────────────────────────────────────────────
+        // Hold spacebar to charge (0→1 over JumpChargeRate seconds).
+        // Release to execute: jump(extent) validates + sets JumpExtent,
+        // then LeaveGround() applies the scaled velocity via get_leave_ground_velocity.
+        float? outJumpExtent = null;
+
+        if (input.Jump && _body.OnWalkable)
         {
-            var jumpResult = _motion.jump(1.0f);
+            // Spacebar held and on the ground — accumulate charge.
+            if (!_jumpCharging)
+            {
+                _jumpCharging = true;
+                _jumpExtent   = 0f;
+            }
+            _jumpExtent = MathF.Min(_jumpExtent + dt * JumpChargeRate, 1.0f);
+        }
+        else if (_jumpCharging)
+        {
+            // Spacebar released (or left ground during charge) — fire jump.
+            var jumpResult = _motion.jump(_jumpExtent);
             if (jumpResult == WeenieError.None)
             {
-                // jump() set_on_walkable(false); now apply the launch velocity.
                 _motion.LeaveGround();
+                outJumpExtent = _jumpExtent;
             }
+            _jumpCharging = false;
+            _jumpExtent   = 0f;
         }
 
         // ── 4. Integrate physics (gravity, friction, sub-stepping) ────────────
@@ -384,6 +408,7 @@ public sealed class PlayerMovementController
             TurnCommand: outTurnCmd,
             ForwardSpeed: outForwardSpeed,
             SidestepSpeed: outSidestepSpeed,
-            TurnSpeed: outTurnSpeed);
+            TurnSpeed: outTurnSpeed,
+            JumpExtent: outJumpExtent);
     }
 }
diff --git a/src/AcDream.App/Rendering/GameWindow.cs b/src/AcDream.App/Rendering/GameWindow.cs
index a634772..28a7a7b 100644
--- a/src/AcDream.App/Rendering/GameWindow.cs
+++ b/src/AcDream.App/Rendering/GameWindow.cs
@@ -1912,6 +1912,13 @@ public sealed class GameWindow : IDisposable
                         forcePositionSequence:  _liveSession.ForcePositionSequence);
                     _liveSession.SendGameAction(body);
                 }
+
+                if (result.JumpExtent.HasValue)
+                {
+                    // TODO: send jump packet to server (format needs research from holtburger).
+                    // Local jump physics work without server acknowledgment for now.
+                    Console.WriteLine($"jump: extent={result.JumpExtent.Value:F2}");
+                }
             }
 
             // Update the player entity's animation cycle to match current motion.
diff --git a/tests/AcDream.Core.Tests/Input/PlayerMovementControllerTests.cs b/tests/AcDream.Core.Tests/Input/PlayerMovementControllerTests.cs
index 44c55c4..fe1e859 100644
--- a/tests/AcDream.Core.Tests/Input/PlayerMovementControllerTests.cs
+++ b/tests/AcDream.Core.Tests/Input/PlayerMovementControllerTests.cs
@@ -108,8 +108,11 @@ public class PlayerMovementControllerTests
         var controller = new PlayerMovementController(engine);
         controller.SetPosition(new Vector3(96f, 96f, 50f), 0x0001);
 
-        var input = new MovementInput(Jump: true);
-        controller.Update(0.016f, input);
+        // Charged jump: hold for a full charge (1s dt), then release to fire.
+        // A full charge gives enough Vz that the player clears the 0.05-unit
+        // ground-snap threshold within the same integration frame.
+        controller.Update(1.0f, new MovementInput(Jump: true));    // full charge
+        controller.Update(0.016f, new MovementInput(Jump: false)); // release → jump fires
 
         Assert.True(controller.IsAirborne);
         Assert.True(controller.VerticalVelocity > 0f);
@@ -122,8 +125,9 @@ public class PlayerMovementControllerTests
         var controller = new PlayerMovementController(engine);
         controller.SetPosition(new Vector3(96f, 96f, 50f), 0x0001);
 
-        // Jump
-        controller.Update(0.016f, new MovementInput(Jump: true));
+        // Charged jump: hold for a full charge, then release.
+        controller.Update(1.0f, new MovementInput(Jump: true));    // full charge
+        controller.Update(0.016f, new MovementInput(Jump: false)); // release → jump fires
         float z1 = controller.Position.Z;
 
         // A few frames of rising