diff --git a/tests/unit/player-climbing.test.ts b/tests/unit/player-climbing.test.ts
new file mode 100644
index 00000000..54e0545b
--- /dev/null
+++ b/tests/unit/player-climbing.test.ts
@@ -0,0 +1,165 @@
+import { describe, expect, it } from "vitest";
+
+import { createBoxBrush } from "../../src/document/brushes";
+import { createEmptySceneDocument } from "../../src/document/scene-document";
+import { FIRST_PERSON_PLAYER_SHAPE } from "../../src/runtime-three/player-collision";
+import {
+  computeClimbPlaneMovement,
+  isClimbableWallNormal,
+  resolvePlayerClimbSurface,
+  shouldEnterClimbing,
+  shouldExitClimbing
+} from "../../src/runtime-three/player-climbing";
+import type { PlayerStartActionInputState } from "../../src/runtime-three/player-input-bindings";
+import { buildRuntimeSceneFromDocument } from "../../src/runtime-three/runtime-scene-build";
+
+function createInputState(
+  overrides: Partial<PlayerStartActionInputState> = {}
+): PlayerStartActionInputState {
+  return {
+    moveForward: 0,
+    moveBackward: 0,
+    moveLeft: 0,
+    moveRight: 0,
+    jump: 0,
+    sprint: 0,
+    crouch: 0,
+    interact: 0,
+    clearTarget: 0,
+    pauseTime: 0,
+    climb: 0,
+    ...overrides
+  };
+}
+
+describe("player climbing helpers", () => {
+  it("accepts wall-like normals and rejects floor or ceiling normals", () => {
+    expect(isClimbableWallNormal({ x: 0, y: 0, z: 1 })).toBe(true);
+    expect(isClimbableWallNormal({ x: 0, y: 1, z: 0 })).toBe(false);
+    expect(isClimbableWallNormal({ x: 0, y: -1, z: 0 })).toBe(false);
+  });
+
+  it("maps forward/back input vertically and strafe input along the climb face", () => {
+    const upward = computeClimbPlaneMovement({
+      normal: { x: 0, y: 0, z: 1 },
+      input: createInputState({ moveForward: 1 }),
+      speedMetersPerSecond: 2,
+      dt: 0.5
+    });
+    const rightward = computeClimbPlaneMovement({
+      normal: { x: 0, y: 0, z: 1 },
+      input: createInputState({ moveRight: 1 }),
+      speedMetersPerSecond: 2,
+      dt: 0.5
+    });
+
+    expect(upward.motion).toMatchObject({
+      x: 0,
+      y: 1,
+      z: 0
+    });
+    expect(upward.inputMagnitude).toBe(1);
+    expect(rightward.motion).toMatchObject({
+      x: 1,
+      y: 0,
+      z: 0
+    });
+    expect(rightward.inputMagnitude).toBe(1);
+  });
+
+  it("keeps climb entry and exit conditions explicit", () => {
+    const surface = {
+      brushId: "brush-wall",
+      faceId: "negZ",
+      point: { x: 0, y: 1, z: 0.75 },
+      normal: { x: 0, y: 0, z: -1 },
+      distance: 0.75
+    };
+
+    expect(
+      shouldEnterClimbing({
+        climbInput: 1,
+        surface,
+        jumpPressed: false
+      })
+    ).toBe(true);
+    expect(
+      shouldEnterClimbing({
+        climbInput: 0,
+        surface,
+        jumpPressed: false
+      })
+    ).toBe(false);
+    expect(
+      shouldExitClimbing({
+        climbInput: 1,
+        surface,
+        jumpPressed: true
+      })
+    ).toBe(true);
+    expect(
+      shouldExitClimbing({
+        climbInput: 0,
+        surface,
+        jumpPressed: false
+      })
+    ).toBe(true);
+  });
+
+  it("resolves only authored climbable whitebox faces in front of the player", () => {
+    const brush = createBoxBrush({
+      id: "brush-climbable-wall",
+      center: {
+        x: 0,
+        y: 1,
+        z: 0.9
+      },
+      size: {
+        x: 4,
+        y: 2,
+        z: 0.25
+      }
+    });
+    brush.faces.negZ.climbable = true;
+    const runtimeScene = buildRuntimeSceneFromDocument({
+      ...createEmptySceneDocument({ name: "Climb Surface Scene" }),
+      brushes: {
+        [brush.id]: brush
+      }
+    });
+
+    expect(
+      resolvePlayerClimbSurface({
+        runtimeScene,
+        feetPosition: { x: 0, y: 0, z: 0 },
+        facingDirection: { x: 0, y: 0, z: 1 },
+        shape: FIRST_PERSON_PLAYER_SHAPE
+      })
+    ).toMatchObject({
+      brushId: brush.id,
+      faceId: "negZ",
+      normal: {
+        x: 0,
+        y: 0,
+        z: -1
+      }
+    });
+
+    brush.faces.negZ.climbable = false;
+    const runtimeSceneWithoutClimbableFace = buildRuntimeSceneFromDocument({
+      ...createEmptySceneDocument({ name: "Non Climb Surface Scene" }),
+      brushes: {
+        [brush.id]: brush
+      }
+    });
+
+    expect(
+      resolvePlayerClimbSurface({
+        runtimeScene: runtimeSceneWithoutClimbableFace,
+        feetPosition: { x: 0, y: 0, z: 0 },
+        facingDirection: { x: 0, y: 0, z: 1 },
+        shape: FIRST_PERSON_PLAYER_SHAPE
+      })
+    ).toBeNull();
+  });
+});