diff --git a/packages/react-devtools-shared/src/__tests__/__serializers__/storeSerializer.js b/packages/react-devtools-shared/src/__tests__/__serializers__/storeSerializer.js
index ea5a402bdc..c7f19f1404 100644
--- a/packages/react-devtools-shared/src/__tests__/__serializers__/storeSerializer.js
+++ b/packages/react-devtools-shared/src/__tests__/__serializers__/storeSerializer.js
@@ -5,10 +5,7 @@ export function test(maybeStore) {
   // It's important to lazy-require the Store rather than imported at the head of the module.
   // Because we reset modules between tests, different Store implementations will be used for each test.
   // Unfortunately Jest does not reset its own serializer modules.
-  return (
-    maybeStore instanceof
-    require('react-devtools-shared/src/devtools/store').default
-  );
+  return maybeStore?.constructor?.name === 'Store';
 }
 
 // print() is part of Jest's serializer API
diff --git a/packages/react-devtools-shared/src/__tests__/store-test.js b/packages/react-devtools-shared/src/__tests__/store-test.js
index fad4622acc..3b60d5ae09 100644
--- a/packages/react-devtools-shared/src/__tests__/store-test.js
+++ b/packages/react-devtools-shared/src/__tests__/store-test.js
@@ -2489,7 +2489,7 @@ describe('Store', () => {
       withErrorsOrWarningsIgnored(['test-only:'], async () => {
         await act(() => render(<React.Fragment />));
       });
-      expect(store).toMatchInlineSnapshot(`[root]`);
+      expect(store).toMatchInlineSnapshot(``);
       expect(store.componentWithErrorCount).toBe(0);
       expect(store.componentWithWarningCount).toBe(0);
     });
@@ -3083,6 +3083,9 @@ describe('Store', () => {
 
   it('should handle an empty root', async () => {
     await actAsync(() => render(null));
+    expect(store).toMatchInlineSnapshot(``);
+
+    await actAsync(() => render(<span />));
     expect(store).toMatchInlineSnapshot(`[root]`);
   });
 });
diff --git a/packages/react-devtools-shared/src/backend/fiber/renderer.js b/packages/react-devtools-shared/src/backend/fiber/renderer.js
index 12e2ce31fb..17551f6211 100644
--- a/packages/react-devtools-shared/src/backend/fiber/renderer.js
+++ b/packages/react-devtools-shared/src/backend/fiber/renderer.js
@@ -4405,8 +4405,10 @@ export function attach(
                     traceNearestHostComponentUpdate,
                     virtualLevel,
                   );
-                  updateFlags |=
-                    ShouldResetChildren | ShouldResetSuspenseChildren;
+                  updateFlags |= ShouldResetSuspenseChildren;
+                  if (!isInDisconnectedSubtree) {
+                    updateFlags |= ShouldResetChildren;
+                  }
                 } else {
                   updateFlags |= updateVirtualInstanceRecursively(
                     previousVirtualInstance,
@@ -4459,7 +4461,10 @@ export function attach(
                 insertChild(newVirtualInstance);
                 previousVirtualInstance = newVirtualInstance;
                 previousVirtualInstanceWasMount = true;
-                updateFlags |= ShouldResetChildren;
+                updateFlags |= ShouldResetSuspenseChildren;
+                if (!isInDisconnectedSubtree) {
+                  updateFlags |= ShouldResetChildren;
+                }
               }
               // Existing children might be reparented into this new virtual instance.
               // TODO: This will cause the front end to error which needs to be fixed.
@@ -4486,7 +4491,10 @@ export function attach(
               traceNearestHostComponentUpdate,
               virtualLevel,
             );
-            updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+            updateFlags |= ShouldResetSuspenseChildren;
+            if (!isInDisconnectedSubtree) {
+              updateFlags |= ShouldResetChildren;
+            }
           } else {
             updateFlags |= updateVirtualInstanceRecursively(
               previousVirtualInstance,
@@ -4538,7 +4546,10 @@ export function attach(
           // They are always different referentially, but if the instances line up
           // conceptually we'll want to know that.
           if (prevChild !== prevChildAtSameIndex) {
-            updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+            updateFlags |= ShouldResetSuspenseChildren;
+            if (!isInDisconnectedSubtree) {
+              updateFlags |= ShouldResetChildren;
+            }
           }
 
           moveChild(fiberInstance, previousSiblingOfExistingInstance);
@@ -4555,7 +4566,10 @@ export function attach(
         } else if (prevChild !== null && shouldFilterFiber(nextChild)) {
           // The filtered instance could've reordered.
           if (prevChild !== prevChildAtSameIndex) {
-            updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+            updateFlags |= ShouldResetSuspenseChildren;
+            if (!isInDisconnectedSubtree) {
+              updateFlags |= ShouldResetChildren;
+            }
           }
 
           // If this Fiber should be filtered, we need to still update its children.
@@ -4579,7 +4593,10 @@ export function attach(
 
           mountFiberRecursively(nextChild, traceNearestHostComponentUpdate);
           // Need to mark the parent set to remount the new instance.
-          updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+          updateFlags |= ShouldResetSuspenseChildren;
+          if (!isInDisconnectedSubtree) {
+            updateFlags |= ShouldResetChildren;
+          }
         }
       }
       // Try the next child.
@@ -4602,7 +4619,10 @@ export function attach(
           traceNearestHostComponentUpdate,
           virtualLevel,
         );
-        updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+        updateFlags |= ShouldResetSuspenseChildren;
+        if (!isInDisconnectedSubtree) {
+          updateFlags |= ShouldResetChildren;
+        }
       } else {
         updateFlags |= updateVirtualInstanceRecursively(
           previousVirtualInstance,
@@ -4616,7 +4636,10 @@ export function attach(
     }
     // If we have no more children, but used to, they don't line up.
     if (prevChildAtSameIndex !== null) {
-      updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+      updateFlags |= ShouldResetSuspenseChildren;
+      if (!isInDisconnectedSubtree) {
+        updateFlags |= ShouldResetChildren;
+      }
     }
     return updateFlags;
   }
@@ -4628,7 +4651,9 @@ export function attach(
     traceNearestHostComponentUpdate: boolean,
   ): UpdateFlags {
     if (nextFirstChild === null) {
-      return prevFirstChild !== null ? ShouldResetChildren : NoUpdate;
+      return prevFirstChild !== null && !isInDisconnectedSubtree
+        ? ShouldResetChildren
+        : NoUpdate;
     }
     return updateVirtualChildrenRecursively(
       nextFirstChild,
@@ -4854,7 +4879,10 @@ export function attach(
             traceNearestHostComponentUpdate,
           );
 
-          updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+          updateFlags |= ShouldResetSuspenseChildren;
+          if (!isInDisconnectedSubtree) {
+            updateFlags |= ShouldResetChildren;
+          }
         }
 
         const childrenUpdateFlags =
@@ -4877,7 +4905,10 @@ export function attach(
             nextPrimaryChildSet,
             traceNearestHostComponentUpdate,
           );
-          updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+          updateFlags |= ShouldResetSuspenseChildren;
+          if (!isInDisconnectedSubtree) {
+            updateFlags |= ShouldResetChildren;
+          }
         }
       } else if (!prevDidTimeout && nextDidTimeOut) {
         // Primary -> Fallback:
@@ -4894,7 +4925,10 @@ export function attach(
             nextFallbackChildSet,
             traceNearestHostComponentUpdate,
           );
-          updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+          updateFlags |= ShouldResetSuspenseChildren;
+          if (!isInDisconnectedSubtree) {
+            updateFlags |= ShouldResetChildren;
+          }
         }
       } else if (nextIsHidden) {
         if (!prevWasHidden) {
@@ -4939,7 +4973,10 @@ export function attach(
         if (fiberInstance !== null && !isInDisconnectedSubtree) {
           reconnectChildrenRecursively(fiberInstance);
           // Children may have reordered while they were hidden.
-          updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
+          updateFlags |= ShouldResetSuspenseChildren;
+          if (!isInDisconnectedSubtree) {
+            updateFlags |= ShouldResetChildren;
+          }
         }
       } else if (
         nextFiber.tag === SuspenseComponent &&
@@ -5318,12 +5355,12 @@ export function attach(
     root: FiberRoot,
     priorityLevel: void | number,
   ) {
-    const current = root.current;
+    const nextFiber = root.current;
 
     let prevFiber: null | Fiber = null;
     let rootInstance = rootToFiberInstanceMap.get(root);
     if (!rootInstance) {
-      rootInstance = createFiberInstance(current);
+      rootInstance = createFiberInstance(nextFiber);
       rootToFiberInstanceMap.set(root, rootInstance);
       idToDevToolsInstanceMap.set(rootInstance.id, rootInstance);
     } else {
@@ -5362,30 +5399,25 @@ export function attach(
       };
     }
 
-    if (prevFiber !== null) {
-      // TODO: relying on this seems a bit fishy.
-      const wasMounted =
-        prevFiber.memoizedState != null &&
-        prevFiber.memoizedState.element != null;
-      const isMounted =
-        current.memoizedState != null && current.memoizedState.element != null;
-      if (!wasMounted && isMounted) {
-        // Mount a new root.
-        setRootPseudoKey(currentRoot.id, current);
-        mountFiberRecursively(current, false);
-      } else if (wasMounted && isMounted) {
-        // Update an existing root.
-        updateFiberRecursively(rootInstance, current, prevFiber, false);
-      } else if (wasMounted && !isMounted) {
-        // Unmount an existing root.
-        unmountInstanceRecursively(rootInstance);
-        removeRootPseudoKey(currentRoot.id);
-        rootToFiberInstanceMap.delete(root);
-      }
-    } else {
+    const isMounted = nextFiber.child !== null;
+    const wasMounted = prevFiber !== null && prevFiber.child !== null;
+    if (!wasMounted && isMounted) {
       // Mount a new root.
-      setRootPseudoKey(currentRoot.id, current);
-      mountFiberRecursively(current, false);
+      setRootPseudoKey(currentRoot.id, nextFiber);
+      mountFiberRecursively(nextFiber, false);
+    } else if (wasMounted && isMounted) {
+      if (prevFiber === null) {
+        throw new Error(
+          'Expected previous fiber when updating an existing root',
+        );
+      }
+      // Update an existing root.
+      updateFiberRecursively(rootInstance, nextFiber, prevFiber, false);
+    } else if (wasMounted && !isMounted) {
+      // Unmount an existing root.
+      unmountInstanceRecursively(rootInstance);
+      removeRootPseudoKey(currentRoot.id);
+      rootToFiberInstanceMap.delete(root);
     }
 
     if (isProfiling && isProfilingSupported) {
diff --git a/packages/react-dom/src/__tests__/ReactDOM-test.js b/packages/react-dom/src/__tests__/ReactDOM-test.js
index ff82965445..e80841c844 100644
--- a/packages/react-dom/src/__tests__/ReactDOM-test.js
+++ b/packages/react-dom/src/__tests__/ReactDOM-test.js
@@ -959,5 +959,15 @@ describe('ReactDOM', () => {
     expect(document.documentElement.outerHTML).toBe(
       '<html lang="en"><head><meta itemprop="" content="primary" style=""></head><body><div style="">goodbye!</div></body></html>',
     );
+
+    expect(window.store).toMatchInlineSnapshot(`
+      [root]
+        ▾ <App>
+          ▾ <Suspense>
+              <Comp>
+              <Message>
+      [suspense-root]  rects={[]}
+        <Suspense name="App" rects={[]}>
+    `);
   });
 });
diff --git a/scripts/jest/config.base.js b/scripts/jest/config.base.js
index ba001e165e..e36329cdf6 100644
--- a/scripts/jest/config.base.js
+++ b/scripts/jest/config.base.js
@@ -1,5 +1,10 @@
 'use strict';
 
+const moduleNameMapper = {};
+
+moduleNameMapper['react-devtools-feature-flags'] =
+  '<rootDir>/packages/react-devtools-shared/src/config/DevToolsFeatureFlags.default';
+
 module.exports = {
   globalSetup: require.resolve('./setupGlobal.js'),
   modulePathIgnorePatterns: [
@@ -26,6 +31,7 @@ module.exports = {
   // Only include files directly in __tests__, not in nested folders.
   testRegex: '/__tests__/[^/]*(\\.js|\\.coffee|[^d]\\.ts)$',
   moduleFileExtensions: ['js', 'json', 'node', 'coffee', 'ts'],
+  moduleNameMapper,
   rootDir: process.cwd(),
   roots: ['<rootDir>/packages', '<rootDir>/scripts'],
   collectCoverageFrom: ['packages/**/*.js'],
@@ -33,7 +39,12 @@ module.exports = {
     enableGlobally: true,
     legacyFakeTimers: true,
   },
-  snapshotSerializers: [require.resolve('jest-snapshot-serializer-raw')],
+  snapshotSerializers: [
+    require.resolve(
+      '../../packages/react-devtools-shared/src/__tests__/__serializers__/storeSerializer.js'
+    ),
+    require.resolve('jest-snapshot-serializer-raw'),
+  ],
 
   testEnvironment: '<rootDir>/scripts/jest/ReactJSDOMEnvironment',
 
diff --git a/scripts/jest/setupEnvironment.js b/scripts/jest/setupEnvironment.js
index 44acb04f18..c7ac16110f 100644
--- a/scripts/jest/setupEnvironment.js
+++ b/scripts/jest/setupEnvironment.js
@@ -8,6 +8,11 @@ global.__DEV__ = NODE_ENV === 'development';
 global.__EXTENSION__ = false;
 global.__TEST__ = NODE_ENV === 'test';
 global.__PROFILE__ = NODE_ENV === 'development';
+global.__IS_FIREFOX__ = false;
+global.__IS_CHROME__ = false;
+global.__IS_EDGE__ = false;
+global.__IS_NATIVE__ = false;
+global.__IS_INTERNAL_MCP_BUILD__ = false;
 
 const RELEASE_CHANNEL = process.env.RELEASE_CHANNEL;
 
diff --git a/scripts/jest/setupTests.js b/scripts/jest/setupTests.js
index 1e8d8e5276..563eeda5e7 100644
--- a/scripts/jest/setupTests.js
+++ b/scripts/jest/setupTests.js
@@ -67,6 +67,72 @@ if (process.env.REACT_CLASS_EQUIVALENCE_TEST) {
   beforeEach(resetAllUnexpectedConsoleCalls);
   afterEach(assertConsoleLogsCleared);
 
+  const devtoolsHookTarget = globalThis;
+  beforeEach(() => {
+    const Agent = require('react-devtools-shared/src/backend/agent').default;
+    const {initBackend} = require('react-devtools-shared/src/backend');
+    const Bridge = require('react-devtools-shared/src/bridge').default;
+    const Store = require('react-devtools-shared/src/devtools/store').default;
+    const {installHook} = require('react-devtools-shared/src/hook');
+    const {
+      getDefaultComponentFilters,
+      setSavedComponentFilters,
+    } = require('react-devtools-shared/src/utils');
+
+    // Initialize filters to a known good state.
+    setSavedComponentFilters(getDefaultComponentFilters());
+    devtoolsHookTarget.__REACT_DEVTOOLS_COMPONENT_FILTERS__ =
+      getDefaultComponentFilters();
+
+    // Also initialize inline warnings so that we can test them.
+    devtoolsHookTarget.__REACT_DEVTOOLS_SHOW_INLINE_WARNINGS_AND_ERRORS__ =
+      true;
+
+    installHook(devtoolsHookTarget, {
+      appendComponentStack: false,
+      breakOnConsoleErrors: false,
+      showInlineWarningsAndErrors: true,
+      hideConsoleLogsInStrictMode: false,
+    });
+
+    const bridgeListeners = [];
+    const bridge = new Bridge({
+      listen(callback) {
+        bridgeListeners.push(callback);
+        return () => {
+          const index = bridgeListeners.indexOf(callback);
+          if (index >= 0) {
+            bridgeListeners.splice(index, 1);
+          }
+        };
+      },
+      send(event: string, payload: any, transferable: Array<any>) {
+        bridgeListeners.forEach(callback =>
+          callback({event, payload, transferable})
+        );
+      },
+    });
+
+    const store = new Store(bridge, {
+      supportsTimeline: true,
+    });
+
+    const agent = new Agent(bridge);
+    const hook = devtoolsHookTarget.__REACT_DEVTOOLS_GLOBAL_HOOK__;
+    initBackend(hook, agent, devtoolsHookTarget);
+
+    devtoolsHookTarget.agent = agent;
+    devtoolsHookTarget.bridge = bridge;
+    devtoolsHookTarget.store = store;
+  });
+
+  afterEach(() => {
+    delete devtoolsHookTarget.__REACT_DEVTOOLS_GLOBAL_HOOK__;
+    delete devtoolsHookTarget.store;
+    delete devtoolsHookTarget.agent;
+    delete devtoolsHookTarget.bridge;
+  });
+
   // TODO: enable this check so we don't forget to reset spyOnX mocks.
   // afterEach(() => {
   //   if (