diff --git a/src/app/pages/algorithms/fluid/fluid-simulation.spec.ts b/src/app/pages/algorithms/fluid/fluid-simulation.spec.ts
index ecf2e2a..dc362a1 100644
--- a/src/app/pages/algorithms/fluid/fluid-simulation.spec.ts
+++ b/src/app/pages/algorithms/fluid/fluid-simulation.spec.ts
@@ -1,4 +1,4 @@
-import {FluidParams, FluidSimulation} from './fluid-simulation';
+import type {FluidParams} from './fluid-simulation';
 import {DEFAULT_SETTINGS, MAX_PRESSURE_ITERATIONS, Splat} from './fluid.model';
 
 const renderCalls: string[] = [];
@@ -62,7 +62,11 @@ function params(pressureIterations: number, splats: Splat[] = []): FluidParams {
   return {settings: {...DEFAULT_SETTINGS, pressureIterations}, splats};
 }
 
-function start(readParams: () => FluidParams) {
+// gpu-state.ts is shared between specs and keeps the @babylonjs/core of whichever spec loaded it first (the real
+// one, or another spec's mock). A fresh module graph per test makes it use this spec's mock.
+async function start(readParams: () => FluidParams) {
+  vi.resetModules();
+  const {FluidSimulation} = await import('./fluid-simulation');
   renderCalls.length = 0;
   disposedTargets = 0;
   disposedWrappers = 0;
@@ -78,9 +82,9 @@ function count(name: string): number {
 }
 
 describe('FluidSimulation', () => {
-  it('drawsNothingUntilAllShadersReady', () => {
+  it('drawsNothingUntilAllShadersReady', async () => {
     const readParams = vi.fn(() => params(1, [splat]));
-    const {scene} = start(readParams);
+    const {scene} = await start(readParams);
     ready['fluidAdvect'] = false;
 
     scene.frame();
@@ -93,9 +97,9 @@ describe('FluidSimulation', () => {
     expect(renderCalls).toContain('fluidSplat');
   });
 
-  it('readsParamsAtFrameStart', () => {
+  it('readsParamsAtFrameStart', async () => {
     let iterations = 5;
-    const {scene} = start(() => params(iterations));
+    const {scene} = await start(() => params(iterations));
     scene.frame();
     expect(count('fluidPressure')).toBe(5);
 
@@ -105,14 +109,14 @@ describe('FluidSimulation', () => {
     expect(count('fluidPressure')).toBe(12);
   });
 
-  it('clampsPressureIterations', () => {
-    const {scene} = start(() => params(1000));
+  it('clampsPressureIterations', async () => {
+    const {scene} = await start(() => params(1000));
     scene.frame();
     expect(count('fluidPressure')).toBe(MAX_PRESSURE_ITERATIONS);
   });
 
-  it('passOrder', () => {
-    const {scene} = start(() => params(2, [splat]));
+  it('passOrder', async () => {
+    const {scene} = await start(() => params(2, [splat]));
     scene.frame();
     renderCalls.length = 0;
     scene.frame();
@@ -123,8 +127,8 @@ describe('FluidSimulation', () => {
     ]);
   });
 
-  it('resetClearsBeforeSplats', () => {
-    const {scene, simulation} = start(() => params(1, [splat]));
+  it('resetClearsBeforeSplats', async () => {
+    const {scene, simulation} = await start(() => params(1, [splat]));
     scene.frame();
     renderCalls.length = 0;
     scene.frame();
@@ -136,8 +140,8 @@ describe('FluidSimulation', () => {
     expect(renderCalls.slice(0, 4)).toEqual(['fluidClear', 'fluidClear', 'fluidClear', 'fluidSplat']);
   });
 
-  it('disposeFreesAllTargets', () => {
-    const {simulation} = start(() => params(1));
+  it('disposeFreesAllTargets', async () => {
+    const {simulation} = await start(() => params(1));
     simulation.dispose();
     expect(disposedTargets).toBe(8);
     expect(disposedWrappers).toBe(8);
diff --git a/src/app/pages/algorithms/gray-scott/gray-scott-simulation.spec.ts b/src/app/pages/algorithms/gray-scott/gray-scott-simulation.spec.ts
index 79e671a..c1a941f 100644
--- a/src/app/pages/algorithms/gray-scott/gray-scott-simulation.spec.ts
+++ b/src/app/pages/algorithms/gray-scott/gray-scott-simulation.spec.ts
@@ -1,4 +1,4 @@
-import {GrayScottParams, GrayScottSimulation} from './gray-scott-simulation';
+import type {GrayScottParams} from './gray-scott-simulation';
 import {DEFAULT_SETTINGS} from './gray-scott.model';
 
 const renderCalls: string[] = [];
@@ -55,9 +55,13 @@ function paramsWithSteps(stepsPerFrame: number): GrayScottParams {
 }
 
 describe('GrayScottSimulation', () => {
-  it('readsParamsAtFrameStart', () => {
+  it('readsParamsAtFrameStart', async () => {
     let stepsPerFrame = 1;
     const scene = fakeScene();
+    // gpu-state.ts is shared between specs and keeps the @babylonjs/core of whichever spec loaded it first; a fresh
+    // module graph makes it use this spec's mock.
+    vi.resetModules();
+    const {GrayScottSimulation} = await import('./gray-scott-simulation');
     const simulation = new GrayScottSimulation();
     simulation.init(scene as never, {} as never, 'float', () => paramsWithSteps(stepsPerFrame));
     scene.frame();
diff --git a/src/app/pages/algorithms/lenia/lenia-simulation.spec.ts b/src/app/pages/algorithms/lenia/lenia-simulation.spec.ts
index cbd95f7..f6c3f15 100644
--- a/src/app/pages/algorithms/lenia/lenia-simulation.spec.ts
+++ b/src/app/pages/algorithms/lenia/lenia-simulation.spec.ts
@@ -1,4 +1,4 @@
-import {LeniaParams, LeniaSimulation} from './lenia-simulation';
+import type {LeniaParams} from './lenia-simulation';
 import {DEFAULT_SETTINGS} from './lenia.model';
 
 const renderCalls: {name: string; target: unknown}[] = [];
@@ -64,11 +64,15 @@ function paramsWithSteps(stepsPerFrame: number): LeniaParams {
 }
 
 describe('LeniaSimulation', () => {
-  it('keepsSeedWhileStepShaderCompiles', () => {
+  it('keepsSeedWhileStepShaderCompiles', async () => {
     renderCalls.length = 0;
     ready['leniaCopy'] = true;
     ready['leniaStep'] = false;
     const scene = fakeScene();
+    // gpu-state.ts is shared between specs and keeps the @babylonjs/core of whichever spec loaded it first; a fresh
+    // module graph makes it use this spec's mock.
+    vi.resetModules();
+    const {LeniaSimulation} = await import('./lenia-simulation');
     const simulation = new LeniaSimulation();
     simulation.init(scene as never, {} as never, 'float', () => paramsWithSteps(1));
     simulation.seed(new Uint8Array(4));
@@ -85,12 +89,16 @@ describe('LeniaSimulation', () => {
     expect(firstStep.target).not.toBe(seededTarget);
   });
 
-  it('readsParamsAtFrameStart', () => {
+  it('readsParamsAtFrameStart', async () => {
     renderCalls.length = 0;
     ready['leniaCopy'] = true;
     ready['leniaStep'] = true;
     let stepsPerFrame = 1;
     const scene = fakeScene();
+    // gpu-state.ts is shared between specs and keeps the @babylonjs/core of whichever spec loaded it first; a fresh
+    // module graph makes it use this spec's mock.
+    vi.resetModules();
+    const {LeniaSimulation} = await import('./lenia-simulation');
     const simulation = new LeniaSimulation();
     simulation.init(scene as never, {} as never, 'float', () => paramsWithSteps(stepsPerFrame));
     simulation.seed(new Uint8Array(4));