diff --git a/tests/unit/player-start-interaction-reach-serialization.test.ts b/tests/unit/player-start-interaction-reach-serialization.test.ts
new file mode 100644
index 00000000..1c95540b
--- /dev/null
+++ b/tests/unit/player-start-interaction-reach-serialization.test.ts
@@ -0,0 +1,61 @@
+import { describe, expect, it } from "vitest";
+
+import { migrateSceneDocument } from "../../src/document/migrate-scene-document";
+import {
+  createEmptySceneDocument,
+  SHADER_SKY_AURORA_SCENE_DOCUMENT_VERSION
+} from "../../src/document/scene-document";
+import {
+  DEFAULT_PLAYER_START_INTERACTION_REACH_METERS,
+  createPlayerStartEntity
+} from "../../src/entities/entity-instances";
+import {
+  parseSceneDocumentJson,
+  serializeSceneDocument
+} from "../../src/serialization/scene-document-json";
+
+describe("Player Start interaction reach persistence", () => {
+  it("migrates legacy player starts without an authored interaction reach", () => {
+    const playerStart = createPlayerStartEntity({
+      id: "entity-player-start-legacy"
+    });
+    const legacyPlayerStart = {
+      ...playerStart
+    } as Record<string, unknown>;
+
+    delete legacyPlayerStart.interactionReachMeters;
+
+    const migrated = migrateSceneDocument({
+      ...createEmptySceneDocument({ name: "Legacy Reach Scene" }),
+      version: SHADER_SKY_AURORA_SCENE_DOCUMENT_VERSION,
+      entities: {
+        [playerStart.id]: legacyPlayerStart
+      }
+    });
+
+    expect(migrated.entities[playerStart.id]).toMatchObject({
+      kind: "playerStart",
+      interactionReachMeters: DEFAULT_PLAYER_START_INTERACTION_REACH_METERS
+    });
+  });
+
+  it("round-trips an authored interaction reach through scene JSON", () => {
+    const playerStart = createPlayerStartEntity({
+      id: "entity-player-start-round-trip",
+      interactionReachMeters: 3.4
+    });
+    const document = {
+      ...createEmptySceneDocument({ name: "Round Trip Reach Scene" }),
+      entities: {
+        [playerStart.id]: playerStart
+      }
+    };
+
+    const parsed = parseSceneDocumentJson(serializeSceneDocument(document));
+
+    expect(parsed.entities[playerStart.id]).toMatchObject({
+      kind: "playerStart",
+      interactionReachMeters: 3.4
+    });
+  });
+});