diff --git a/packages/physics/__tests__/plugin.spec.ts b/packages/physics/__tests__/plugin.spec.ts
index be84e3054a..223729bdd1 100644
--- a/packages/physics/__tests__/plugin.spec.ts
+++ b/packages/physics/__tests__/plugin.spec.ts
@@ -70,6 +70,36 @@ describe("rapier plugin", () => {
     plugin.dispose?.(ctx);
   });
 
+  it("resolves a setup whose game was disposed first, installing nothing and reporting it", async () => {
+    await RAPIER.init();
+    const plugin = rapier();
+    const ctx = { physics: undefined } as unknown as ICtx<Record<string, unknown>, IPhysicsContext>;
+    const gates: Promise<void>[] = [];
+    const runtime = {
+      fixedStep: () => 0,
+      holdStart: (gate: Promise<void>) => {
+        gates.push(gate);
+        return gate;
+      },
+      observations: { contribute: () => () => undefined, contributions: () => [] },
+      rapier: null,
+      seed: 1,
+      step: 1 / 60,
+      tick: () => 0,
+    } satisfies IGamePluginRuntime;
+    const warn = vi.spyOn(console, "warn").mockImplementation(() => undefined);
+
+    plugin.setup?.(ctx, runtime);
+    plugin.dispose?.(ctx);
+
+    // A reload during the Wasm load must not become a boot failure on the page.
+    await expect(Promise.all(gates)).resolves.toBeDefined();
+    expect(ctx.physics).toBeUndefined();
+    expect(runtime.rapier).toBeNull();
+    expect(warn).toHaveBeenCalledWith(expect.stringMatching(/TN_PHYSICS_SETUP_SUPERSEDED/u));
+    warn.mockRestore();
+  });
+
   it("should register the actual Rapier runtime version", async () => {
     await RAPIER.init();
     const plugin = rapier();
diff --git a/packages/physics/src/navigation/index.ts b/packages/physics/src/navigation/index.ts
index ce9cead67f..2ee98d4d1c 100644
--- a/packages/physics/src/navigation/index.ts
+++ b/packages/physics/src/navigation/index.ts
@@ -57,13 +57,16 @@ export function recast(): NavigationPlugin {
     // Like rapier(), Recast initializes while the scene loads and holds `enter()` until it is up.
     setup: (ctx: ICtx<Record<string, unknown>, IPhysicsContext>, runtime) => {
       // rapier() leaves its readiness here (`plugin.ts` PHYSICS_READY); this bundle has no copy of it.
-      const physics: Promise<IPhysicsContext> | undefined = Reflect.get(
+      const physics: Promise<IPhysicsContext | undefined> | undefined = Reflect.get(
         ctx,
         Symbol.for("threenative.physics.ready"),
       );
       if (physics === undefined)
         throw new Error("recast() requires rapier() earlier in the plugins array.");
       const ready = Promise.all([physics, initialize()]).then(([context]) => {
+        // The page that asked for navigation is gone; installing into it would leak, and rejecting
+        // would report a boot failure the disposed game never had.
+        if (context === undefined) return;
         const empty = emptyNavigation();
         navigation = {
           agents: new Set(),
diff --git a/packages/physics/src/plugin.ts b/packages/physics/src/plugin.ts
index ceb5b1c9b7..9252ab5e7b 100644
--- a/packages/physics/src/plugin.ts
+++ b/packages/physics/src/plugin.ts
@@ -213,9 +213,17 @@ export function rapier(options: IPhysicsOptions = {}): PhysicsPlugin {
     setup: (ctx: ICtx<Record<string, unknown>, IPhysicsContext>, runtime) => {
       gameContext = ctx;
       const generation = ++generations;
-      const ready = backend.initialize().then(() => {
-        if (generation !== generations)
-          throw new Error("rapier() was disposed before it initialized.");
+      const ready = backend.initialize().then((): IPhysicsContext | undefined => {
+        // A reload or a stop raced Rapier's Wasm. The generation that asked is gone, so nothing is
+        // installed — and nothing rejects: with the start gate, nothing awaits `ready` any more, so
+        // a rejection here reached the page as a boot failure it never had (the 0.3.13 release proof
+        // stopped on exactly that, PRD-860).
+        if (generation !== generations) {
+          console.warn(
+            "TN_PHYSICS_SETUP_SUPERSEDED: rapier initialized after its game was disposed; nothing was installed.",
+          );
+          return undefined;
+        }
         const selected = backend.createSimulation(options);
         simulation = selected;
         if (runtime !== undefined) runtime.rapier = selected.version;