diff --git a/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js b/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js
index 2ad221d5fbcb6..91f6e8f022727 100644
--- a/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js
+++ b/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js
@@ -18,6 +18,11 @@ let Suspense;
 let SuspenseList;
 let act;
 
+// Copied from ReactFiberLanes. Don't do this!
+// This is hard coded directly to avoid needing to import, and
+// we'll remove this as we replace runWithPriority with React APIs.
+export const IdleLanePriority = 2;
+
 function dispatchMouseEvent(to, from) {
   if (!to) {
     to = null;
@@ -623,7 +628,7 @@ describe('ReactDOMServerPartialHydration', () => {
     expect(span.textContent).toBe('Hello');
 
     // Schedule an update at idle priority
-    Scheduler.unstable_runWithPriority(Scheduler.unstable_IdlePriority, () => {
+    ReactDOM.unstable_runWithPriority(IdleLanePriority, () => {
       root.render(<App text="Hi" className="hi" />);
     });
 
diff --git a/packages/react-dom/src/__tests__/ReactDOMServerSelectiveHydration-test.internal.js b/packages/react-dom/src/__tests__/ReactDOMServerSelectiveHydration-test.internal.js
index 19cf6065e6b9d..96adf85ba35a8 100644
--- a/packages/react-dom/src/__tests__/ReactDOMServerSelectiveHydration-test.internal.js
+++ b/packages/react-dom/src/__tests__/ReactDOMServerSelectiveHydration-test.internal.js
@@ -19,6 +19,11 @@ let Scheduler;
 let Suspense;
 let act;
 
+// Copied from ReactFiberLanes. Don't do this!
+// This is hard coded directly to avoid needing to import, and
+// we'll remove this as we replace runWithPriority with React APIs.
+export const IdleLanePriority = 2;
+
 function dispatchMouseHoverEvent(to, from) {
   if (!to) {
     to = null;
@@ -96,7 +101,7 @@ function dispatchClickEvent(target) {
 // and there's no native DOM event that maps to idle priority, so this is a
 // temporary workaround. Need something like ReactDOM.unstable_IdleUpdates.
 function TODO_scheduleIdleDOMSchedulerTask(fn) {
-  Scheduler.unstable_runWithPriority(Scheduler.unstable_IdlePriority, () => {
+  ReactDOM.unstable_runWithPriority(IdleLanePriority, () => {
     const prevEvent = window.event;
     window.event = {type: 'message'};
     try {
diff --git a/packages/react-reconciler/src/__tests__/ReactExpiration-test.js b/packages/react-reconciler/src/__tests__/ReactExpiration-test.js
index 48ff50880f943..ed49965318212 100644
--- a/packages/react-reconciler/src/__tests__/ReactExpiration-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactExpiration-test.js
@@ -550,11 +550,7 @@ describe('ReactExpiration', () => {
     function App() {
       const [highPri, setHighPri] = useState(0);
       const [normalPri, setNormalPri] = useState(0);
-      updateHighPri = () =>
-        Scheduler.unstable_runWithPriority(
-          Scheduler.unstable_UserBlockingPriority,
-          () => setHighPri(n => n + 1),
-        );
+      updateHighPri = () => ReactNoop.flushSync(() => setHighPri(n => n + 1));
       updateNormalPri = () => setNormalPri(n => n + 1);
       return (
         <>
diff --git a/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.js b/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.js
index 4c7d308a9c909..cf4e4a3f3b619 100644
--- a/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.js
@@ -3166,10 +3166,7 @@ describe('ReactHooksWithNoopRenderer', () => {
       ]);
 
       await act(async () => {
-        Scheduler.unstable_runWithPriority(
-          Scheduler.unstable_UserBlockingPriority,
-          transition,
-        );
+        transition();
 
         expect(Scheduler).toFlushAndYield([
           'Before... Pending: true',
diff --git a/packages/react-reconciler/src/__tests__/ReactIncrementalUpdates-test.js b/packages/react-reconciler/src/__tests__/ReactIncrementalUpdates-test.js
index e24e2576dde2f..95acb7d8fc778 100644
--- a/packages/react-reconciler/src/__tests__/ReactIncrementalUpdates-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactIncrementalUpdates-test.js
@@ -530,14 +530,8 @@ describe('ReactIncrementalUpdates', () => {
         Scheduler.unstable_yieldValue('Committed: ' + log);
         if (log === 'B') {
           // Right after B commits, schedule additional updates.
-          // TODO: Double wrapping is temporary while we remove Scheduler runWithPriority.
           ReactNoop.unstable_runWithPriority(InputContinuousLanePriority, () =>
-            Scheduler.unstable_runWithPriority(
-              Scheduler.unstable_UserBlockingPriority,
-              () => {
-                pushToLog('C');
-              },
-            ),
+            pushToLog('C'),
           );
           setLog(prevLog => prevLog + 'D');
         }
@@ -556,14 +550,8 @@ describe('ReactIncrementalUpdates', () => {
     await ReactNoop.act(async () => {
       pushToLog('A');
 
-      // TODO: Double wrapping is temporary while we remove Scheduler runWithPriority.
       ReactNoop.unstable_runWithPriority(InputContinuousLanePriority, () =>
-        Scheduler.unstable_runWithPriority(
-          Scheduler.unstable_UserBlockingPriority,
-          () => {
-            pushToLog('B');
-          },
-        ),
+        pushToLog('B'),
       );
     });
     expect(Scheduler).toHaveYielded([
@@ -595,14 +583,8 @@ describe('ReactIncrementalUpdates', () => {
         Scheduler.unstable_yieldValue('Committed: ' + this.state.log);
         if (this.state.log === 'B') {
           // Right after B commits, schedule additional updates.
-          // TODO: Double wrapping is temporary while we remove Scheduler runWithPriority.
           ReactNoop.unstable_runWithPriority(InputContinuousLanePriority, () =>
-            Scheduler.unstable_runWithPriority(
-              Scheduler.unstable_UserBlockingPriority,
-              () => {
-                this.pushToLog('C');
-              },
-            ),
+            this.pushToLog('C'),
           );
           this.pushToLog('D');
         }
@@ -622,14 +604,8 @@ describe('ReactIncrementalUpdates', () => {
 
     await ReactNoop.act(async () => {
       pushToLog('A');
-      // TODO: Double wrapping is temporary while we remove Scheduler runWithPriority.
       ReactNoop.unstable_runWithPriority(InputContinuousLanePriority, () =>
-        Scheduler.unstable_runWithPriority(
-          Scheduler.unstable_UserBlockingPriority,
-          () => {
-            pushToLog('B');
-          },
-        ),
+        pushToLog('B'),
       );
     });
     expect(Scheduler).toHaveYielded([
diff --git a/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js b/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js
index 8ec621be0d015..d7da84e67b752 100644
--- a/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js
@@ -1929,10 +1929,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     // TODO: assert toErrorDev() when the warning is implemented again.
     ReactNoop.act(() => {
-      Scheduler.unstable_runWithPriority(
-        Scheduler.unstable_UserBlockingPriority,
-        () => _setShow(true),
-      );
+      ReactNoop.flushSync(() => _setShow(true));
     });
   });
 
@@ -1959,10 +1956,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
     // TODO: assert toErrorDev() when the warning is implemented again.
     ReactNoop.act(() => {
-      Scheduler.unstable_runWithPriority(
-        Scheduler.unstable_UserBlockingPriority,
-        () => show(),
-      );
+      ReactNoop.flushSync(() => show());
     });
   });
 
@@ -1991,10 +1985,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     expect(ReactNoop).toMatchRenderedOutput('Loading...');
 
     ReactNoop.act(() => {
-      Scheduler.unstable_runWithPriority(
-        Scheduler.unstable_UserBlockingPriority,
-        () => showB(),
-      );
+      ReactNoop.flushSync(() => showB());
     });
 
     expect(Scheduler).toHaveYielded(['Suspend! [A]', 'Suspend! [B]']);
@@ -2025,10 +2016,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
       // TODO: assert toErrorDev() when the warning is implemented again.
       ReactNoop.act(() => {
-        Scheduler.unstable_runWithPriority(
-          Scheduler.unstable_UserBlockingPriority,
-          () => _setShow(true),
-        );
+        ReactNoop.flushSync(() => _setShow(true));
       });
     },
   );
diff --git a/packages/react-reconciler/src/__tests__/useMutableSource-test.internal.js b/packages/react-reconciler/src/__tests__/useMutableSource-test.internal.js
index cf1db2891e11d..e9fc689850233 100644
--- a/packages/react-reconciler/src/__tests__/useMutableSource-test.internal.js
+++ b/packages/react-reconciler/src/__tests__/useMutableSource-test.internal.js
@@ -1476,13 +1476,10 @@ describe('useMutableSource', () => {
         // read during render will happen to match the latest value. But it should
         // still entangle the updates to prevent the previous update (a1) from
         // rendering by itself.
-        Scheduler.unstable_runWithPriority(
-          Scheduler.unstable_IdlePriority,
-          () => {
-            mutateA('a0');
-            mutateB('b0');
-          },
-        );
+        React.unstable_startTransition(() => {
+          mutateA('a0');
+          mutateB('b0');
+        });
         // Finish the current render
         expect(Scheduler).toFlushUntilNextPaint(['c']);
         // a0 will re-render because of the mutation update. But it should show
@@ -1601,12 +1598,9 @@ describe('useMutableSource', () => {
       // Mutate the config. This is at lower priority so that 1) to make sure
       // it doesn't happen to get batched with the in-progress render, and 2)
       // so it doesn't interrupt the in-progress render.
-      Scheduler.unstable_runWithPriority(
-        Scheduler.unstable_IdlePriority,
-        () => {
-          source.valueB = '3';
-        },
-      );
+      React.unstable_startTransition(() => {
+        source.valueB = '3';
+      });
 
       expect(Scheduler).toFlushAndYieldThrough([
         // The partial render completes
@@ -1698,12 +1692,9 @@ describe('useMutableSource', () => {
       expect(source.listenerCount).toBe(1);
 
       // Mutate -> schedule update for ComponentA
-      Scheduler.unstable_runWithPriority(
-        Scheduler.unstable_IdlePriority,
-        () => {
-          source.value = 'two';
-        },
-      );
+      React.unstable_startTransition(() => {
+        source.value = 'two';
+      });
 
       // Commit ComponentB -> notice the change and schedule an update for ComponentB
       expect(Scheduler).toFlushAndYield(['a:two', 'b:two']);
diff --git a/packages/react/src/__tests__/ReactDOMTracing-test.internal.js b/packages/react/src/__tests__/ReactDOMTracing-test.internal.js
index 114b0cfffee53..479e229d91153 100644
--- a/packages/react/src/__tests__/ReactDOMTracing-test.internal.js
+++ b/packages/react/src/__tests__/ReactDOMTracing-test.internal.js
@@ -246,12 +246,8 @@ describe('ReactDOMTracing', () => {
               Scheduler.unstable_yieldValue('Child:update');
             } else {
               Scheduler.unstable_yieldValue('Child:mount');
-              // TODO: Double wrapping is temporary while we remove Scheduler runWithPriority.
               ReactDOM.unstable_runWithPriority(IdleLanePriority, () =>
-                Scheduler.unstable_runWithPriority(
-                  Scheduler.unstable_IdlePriority,
-                  () => setDidMount(true),
-                ),
+                setDidMount(true),
               );
             }
           }, [didMount]);
diff --git a/packages/react/src/__tests__/ReactProfiler-test.internal.js b/packages/react/src/__tests__/ReactProfiler-test.internal.js
index d6e44ab820960..93347b1ac2f9f 100644
--- a/packages/react/src/__tests__/ReactProfiler-test.internal.js
+++ b/packages/react/src/__tests__/ReactProfiler-test.internal.js
@@ -748,6 +748,7 @@ describe('Profiler', () => {
         expect(onRender.mock.calls[2][1]).toBe('update');
       });
 
+      // @gate experimental
       it('is properly distinguish updates and nested-updates when there is more than sync remaining work', () => {
         loadModules({
           enableSchedulerTracing,
@@ -767,15 +768,12 @@ describe('Profiler', () => {
         const onRender = jest.fn();
 
         // Schedule low-priority work.
-        Scheduler.unstable_runWithPriority(
-          Scheduler.unstable_LowPriority,
-          () => {
-            ReactNoop.render(
-              <React.Profiler id="root" onRender={onRender}>
-                <Component />
-              </React.Profiler>,
-            );
-          },
+        React.unstable_startTransition(() =>
+          ReactNoop.render(
+            <React.Profiler id="root" onRender={onRender}>
+              <Component />
+            </React.Profiler>,
+          ),
         );
 
         // Flush sync work with a nested update