diff --git a/exercises/06.rerenders/01.problem.memo/tests/memoized.test.ts b/exercises/06.rerenders/01.problem.memo/tests/memoized.test.ts
index 8f5ee8f83..6000aea52 100644
--- a/exercises/06.rerenders/01.problem.memo/tests/memoized.test.ts
+++ b/exercises/06.rerenders/01.problem.memo/tests/memoized.test.ts
@@ -12,9 +12,70 @@ test('Only ListItem should not rerender when clicking force rerender', async ({
 		const scriptToInject = `
 			<script>
 				let internals
+				const PerformedWorkFlag = 0b000000000000000000000000001
+				const UserCodeFiberTags = new Set([0, 1, 9, 11, 15])
+
+				let activeFallbackComponentNames = null
+
+				function isUserCodeFiberTag(tag) {
+					return UserCodeFiberTags.has(tag)
+				}
+
+				function getDisplayNameFromType(type) {
+					if (!type) return null
+
+					if (typeof type === 'function') {
+						return type.displayName || type.name || null
+					}
+
+					if (typeof type === 'object') {
+						if (typeof type.displayName === 'string' && type.displayName) {
+							return type.displayName
+						}
+
+						if (typeof type.render === 'function') {
+							return type.render.displayName || type.render.name || null
+						}
+
+						if (type.type) {
+							return getDisplayNameFromType(type.type)
+						}
+					}
+
+					return null
+				}
+
+				function getFiberDisplayName(fiber) {
+					return getDisplayNameFromType(fiber.type) || getDisplayNameFromType(fiber.elementType)
+				}
+
+				function didFiberRender(previousFiber, nextFiber) {
+					if (!previousFiber) return true
+					return (nextFiber.flags & PerformedWorkFlag) === PerformedWorkFlag
+				}
+
+				function collectRenderedComponentsFromCommit(root) {
+					if (!activeFallbackComponentNames || !root?.current) return
+
+					const stack = [root.current]
+					while (stack.length > 0) {
+						const fiber = stack.pop()
+						if (!fiber) continue
+
+						if (fiber.sibling) stack.push(fiber.sibling)
+						if (fiber.child) stack.push(fiber.child)
+
+						if (!isUserCodeFiberTag(fiber.tag)) continue
+						if (!didFiberRender(fiber.alternate, fiber)) continue
+
+						const componentName = getFiberDisplayName(fiber) ?? 'Anonymous'
+						activeFallbackComponentNames.push(componentName)
+					}
+				}
 
 				function enhanceExistingHook(existingHook) {
 					const originalInject = existingHook.inject
+					const originalCommitFiberRoot = existingHook.onCommitFiberRoot
 
 					existingHook.inject = (injectedInternals) => {
 						internals = injectedInternals
@@ -23,6 +84,12 @@ test('Only ListItem should not rerender when clicking force rerender', async ({
 						return originalInject?.call(existingHook, injectedInternals) ?? 1
 					}
 
+					existingHook.onCommitFiberRoot = (...args) => {
+						const [, root] = args
+						collectRenderedComponentsFromCommit(root)
+						return originalCommitFiberRoot?.apply(existingHook, args)
+					}
+
 					return existingHook
 				}
 
@@ -34,7 +101,9 @@ test('Only ListItem should not rerender when clicking force rerender', async ({
 							internals = injectedInternals
 							return 1 // Returning a number as React expects a renderer ID
 						},
-						onCommitFiberRoot: () => {},
+						onCommitFiberRoot: (_rendererId, root) => {
+							collectRenderedComponentsFromCommit(root)
+						},
 						onCommitFiberUnmount: () => {},
 					}
 				}
@@ -45,19 +114,32 @@ test('Only ListItem should not rerender when clicking force rerender', async ({
 						throw new Error('🚨 React DevTools is not available')
 					}
 
-					internals.enableProfilerTimer = true
-					internals.enableProfilerCommitHooks = true
-					internals.injectProfilingHooks({
-						markComponentRenderStarted: (fiber) => {
-							componentNames.push(fiber.type.name || 'Anonymous')
-						},
-					})
-
-					await cb()
+					const supportsInjectedProfilingHooks =
+						typeof internals.injectProfilingHooks === 'function'
+
+					if (supportsInjectedProfilingHooks) {
+						internals.enableProfilerTimer = true
+						internals.enableProfilerCommitHooks = true
+						internals.injectProfilingHooks({
+							markComponentRenderStarted: (fiber) => {
+								componentNames.push(fiber.type.name || 'Anonymous')
+							},
+						})
+					} else {
+						activeFallbackComponentNames = componentNames
+					}
 
-					internals.enableProfilerTimer = false
-					internals.enableProfilerCommitHooks = false
-					internals.injectProfilingHooks(null)
+					try {
+						await cb()
+					} finally {
+						if (supportsInjectedProfilingHooks) {
+							internals.enableProfilerTimer = false
+							internals.enableProfilerCommitHooks = false
+							internals.injectProfilingHooks(null)
+						} else {
+							activeFallbackComponentNames = null
+						}
+					}
 
 					return componentNames
 				}
diff --git a/exercises/06.rerenders/01.solution.memo/tests/memoized.test.ts b/exercises/06.rerenders/01.solution.memo/tests/memoized.test.ts
index 8f5ee8f83..6000aea52 100644
--- a/exercises/06.rerenders/01.solution.memo/tests/memoized.test.ts
+++ b/exercises/06.rerenders/01.solution.memo/tests/memoized.test.ts
@@ -12,9 +12,70 @@ test('Only ListItem should not rerender when clicking force rerender', async ({
 		const scriptToInject = `
 			<script>
 				let internals
+				const PerformedWorkFlag = 0b000000000000000000000000001
+				const UserCodeFiberTags = new Set([0, 1, 9, 11, 15])
+
+				let activeFallbackComponentNames = null
+
+				function isUserCodeFiberTag(tag) {
+					return UserCodeFiberTags.has(tag)
+				}
+
+				function getDisplayNameFromType(type) {
+					if (!type) return null
+
+					if (typeof type === 'function') {
+						return type.displayName || type.name || null
+					}
+
+					if (typeof type === 'object') {
+						if (typeof type.displayName === 'string' && type.displayName) {
+							return type.displayName
+						}
+
+						if (typeof type.render === 'function') {
+							return type.render.displayName || type.render.name || null
+						}
+
+						if (type.type) {
+							return getDisplayNameFromType(type.type)
+						}
+					}
+
+					return null
+				}
+
+				function getFiberDisplayName(fiber) {
+					return getDisplayNameFromType(fiber.type) || getDisplayNameFromType(fiber.elementType)
+				}
+
+				function didFiberRender(previousFiber, nextFiber) {
+					if (!previousFiber) return true
+					return (nextFiber.flags & PerformedWorkFlag) === PerformedWorkFlag
+				}
+
+				function collectRenderedComponentsFromCommit(root) {
+					if (!activeFallbackComponentNames || !root?.current) return
+
+					const stack = [root.current]
+					while (stack.length > 0) {
+						const fiber = stack.pop()
+						if (!fiber) continue
+
+						if (fiber.sibling) stack.push(fiber.sibling)
+						if (fiber.child) stack.push(fiber.child)
+
+						if (!isUserCodeFiberTag(fiber.tag)) continue
+						if (!didFiberRender(fiber.alternate, fiber)) continue
+
+						const componentName = getFiberDisplayName(fiber) ?? 'Anonymous'
+						activeFallbackComponentNames.push(componentName)
+					}
+				}
 
 				function enhanceExistingHook(existingHook) {
 					const originalInject = existingHook.inject
+					const originalCommitFiberRoot = existingHook.onCommitFiberRoot
 
 					existingHook.inject = (injectedInternals) => {
 						internals = injectedInternals
@@ -23,6 +84,12 @@ test('Only ListItem should not rerender when clicking force rerender', async ({
 						return originalInject?.call(existingHook, injectedInternals) ?? 1
 					}
 
+					existingHook.onCommitFiberRoot = (...args) => {
+						const [, root] = args
+						collectRenderedComponentsFromCommit(root)
+						return originalCommitFiberRoot?.apply(existingHook, args)
+					}
+
 					return existingHook
 				}
 
@@ -34,7 +101,9 @@ test('Only ListItem should not rerender when clicking force rerender', async ({
 							internals = injectedInternals
 							return 1 // Returning a number as React expects a renderer ID
 						},
-						onCommitFiberRoot: () => {},
+						onCommitFiberRoot: (_rendererId, root) => {
+							collectRenderedComponentsFromCommit(root)
+						},
 						onCommitFiberUnmount: () => {},
 					}
 				}
@@ -45,19 +114,32 @@ test('Only ListItem should not rerender when clicking force rerender', async ({
 						throw new Error('🚨 React DevTools is not available')
 					}
 
-					internals.enableProfilerTimer = true
-					internals.enableProfilerCommitHooks = true
-					internals.injectProfilingHooks({
-						markComponentRenderStarted: (fiber) => {
-							componentNames.push(fiber.type.name || 'Anonymous')
-						},
-					})
-
-					await cb()
+					const supportsInjectedProfilingHooks =
+						typeof internals.injectProfilingHooks === 'function'
+
+					if (supportsInjectedProfilingHooks) {
+						internals.enableProfilerTimer = true
+						internals.enableProfilerCommitHooks = true
+						internals.injectProfilingHooks({
+							markComponentRenderStarted: (fiber) => {
+								componentNames.push(fiber.type.name || 'Anonymous')
+							},
+						})
+					} else {
+						activeFallbackComponentNames = componentNames
+					}
 
-					internals.enableProfilerTimer = false
-					internals.enableProfilerCommitHooks = false
-					internals.injectProfilingHooks(null)
+					try {
+						await cb()
+					} finally {
+						if (supportsInjectedProfilingHooks) {
+							internals.enableProfilerTimer = false
+							internals.enableProfilerCommitHooks = false
+							internals.injectProfilingHooks(null)
+						} else {
+							activeFallbackComponentNames = null
+						}
+					}
 
 					return componentNames
 				}
diff --git a/exercises/06.rerenders/02.problem.comparator/tests/memoized.test.ts b/exercises/06.rerenders/02.problem.comparator/tests/memoized.test.ts
index a1025d863..4e267d303 100644
--- a/exercises/06.rerenders/02.problem.comparator/tests/memoized.test.ts
+++ b/exercises/06.rerenders/02.problem.comparator/tests/memoized.test.ts
@@ -12,9 +12,70 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 		const scriptToInject = `
 			<script>
 				let internals
+				const PerformedWorkFlag = 0b000000000000000000000000001
+				const UserCodeFiberTags = new Set([0, 1, 9, 11, 15])
+
+				let activeFallbackComponentNames = null
+
+				function isUserCodeFiberTag(tag) {
+					return UserCodeFiberTags.has(tag)
+				}
+
+				function getDisplayNameFromType(type) {
+					if (!type) return null
+
+					if (typeof type === 'function') {
+						return type.displayName || type.name || null
+					}
+
+					if (typeof type === 'object') {
+						if (typeof type.displayName === 'string' && type.displayName) {
+							return type.displayName
+						}
+
+						if (typeof type.render === 'function') {
+							return type.render.displayName || type.render.name || null
+						}
+
+						if (type.type) {
+							return getDisplayNameFromType(type.type)
+						}
+					}
+
+					return null
+				}
+
+				function getFiberDisplayName(fiber) {
+					return getDisplayNameFromType(fiber.type) || getDisplayNameFromType(fiber.elementType)
+				}
+
+				function didFiberRender(previousFiber, nextFiber) {
+					if (!previousFiber) return true
+					return (nextFiber.flags & PerformedWorkFlag) === PerformedWorkFlag
+				}
+
+				function collectRenderedComponentsFromCommit(root) {
+					if (!activeFallbackComponentNames || !root?.current) return
+
+					const stack = [root.current]
+					while (stack.length > 0) {
+						const fiber = stack.pop()
+						if (!fiber) continue
+
+						if (fiber.sibling) stack.push(fiber.sibling)
+						if (fiber.child) stack.push(fiber.child)
+
+						if (!isUserCodeFiberTag(fiber.tag)) continue
+						if (!didFiberRender(fiber.alternate, fiber)) continue
+
+						const componentName = getFiberDisplayName(fiber) ?? 'Anonymous'
+						activeFallbackComponentNames.push(componentName)
+					}
+				}
 
 				function enhanceExistingHook(existingHook) {
 					const originalInject = existingHook.inject
+					const originalCommitFiberRoot = existingHook.onCommitFiberRoot
 
 					existingHook.inject = (injectedInternals) => {
 						internals = injectedInternals
@@ -23,6 +84,12 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 						return originalInject?.call(existingHook, injectedInternals) ?? 1
 					}
 
+					existingHook.onCommitFiberRoot = (...args) => {
+						const [, root] = args
+						collectRenderedComponentsFromCommit(root)
+						return originalCommitFiberRoot?.apply(existingHook, args)
+					}
+
 					return existingHook
 				}
 
@@ -34,7 +101,9 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 							internals = injectedInternals
 							return 1 // Returning a number as React expects a renderer ID
 						},
-						onCommitFiberRoot: () => {},
+						onCommitFiberRoot: (_rendererId, root) => {
+							collectRenderedComponentsFromCommit(root)
+						},
 						onCommitFiberUnmount: () => {},
 					}
 				}
@@ -45,19 +114,32 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 						throw new Error('🚨 React DevTools is not available')
 					}
 
-					internals.enableProfilerTimer = true
-					internals.enableProfilerCommitHooks = true
-					internals.injectProfilingHooks({
-						markComponentRenderStarted: (fiber) => {
-							componentNames.push(fiber.type.name || 'Anonymous')
-						},
-					})
-
-					await cb()
+					const supportsInjectedProfilingHooks =
+						typeof internals.injectProfilingHooks === 'function'
+
+					if (supportsInjectedProfilingHooks) {
+						internals.enableProfilerTimer = true
+						internals.enableProfilerCommitHooks = true
+						internals.injectProfilingHooks({
+							markComponentRenderStarted: (fiber) => {
+								componentNames.push(fiber.type.name || 'Anonymous')
+							},
+						})
+					} else {
+						activeFallbackComponentNames = componentNames
+					}
 
-					internals.enableProfilerTimer = false
-					internals.enableProfilerCommitHooks = false
-					internals.injectProfilingHooks(null)
+					try {
+						await cb()
+					} finally {
+						if (supportsInjectedProfilingHooks) {
+							internals.enableProfilerTimer = false
+							internals.enableProfilerCommitHooks = false
+							internals.injectProfilingHooks(null)
+						} else {
+							activeFallbackComponentNames = null
+						}
+					}
 
 					return componentNames
 				}
diff --git a/exercises/06.rerenders/02.solution.comparator/tests/memoized.test.ts b/exercises/06.rerenders/02.solution.comparator/tests/memoized.test.ts
index a1025d863..4e267d303 100644
--- a/exercises/06.rerenders/02.solution.comparator/tests/memoized.test.ts
+++ b/exercises/06.rerenders/02.solution.comparator/tests/memoized.test.ts
@@ -12,9 +12,70 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 		const scriptToInject = `
 			<script>
 				let internals
+				const PerformedWorkFlag = 0b000000000000000000000000001
+				const UserCodeFiberTags = new Set([0, 1, 9, 11, 15])
+
+				let activeFallbackComponentNames = null
+
+				function isUserCodeFiberTag(tag) {
+					return UserCodeFiberTags.has(tag)
+				}
+
+				function getDisplayNameFromType(type) {
+					if (!type) return null
+
+					if (typeof type === 'function') {
+						return type.displayName || type.name || null
+					}
+
+					if (typeof type === 'object') {
+						if (typeof type.displayName === 'string' && type.displayName) {
+							return type.displayName
+						}
+
+						if (typeof type.render === 'function') {
+							return type.render.displayName || type.render.name || null
+						}
+
+						if (type.type) {
+							return getDisplayNameFromType(type.type)
+						}
+					}
+
+					return null
+				}
+
+				function getFiberDisplayName(fiber) {
+					return getDisplayNameFromType(fiber.type) || getDisplayNameFromType(fiber.elementType)
+				}
+
+				function didFiberRender(previousFiber, nextFiber) {
+					if (!previousFiber) return true
+					return (nextFiber.flags & PerformedWorkFlag) === PerformedWorkFlag
+				}
+
+				function collectRenderedComponentsFromCommit(root) {
+					if (!activeFallbackComponentNames || !root?.current) return
+
+					const stack = [root.current]
+					while (stack.length > 0) {
+						const fiber = stack.pop()
+						if (!fiber) continue
+
+						if (fiber.sibling) stack.push(fiber.sibling)
+						if (fiber.child) stack.push(fiber.child)
+
+						if (!isUserCodeFiberTag(fiber.tag)) continue
+						if (!didFiberRender(fiber.alternate, fiber)) continue
+
+						const componentName = getFiberDisplayName(fiber) ?? 'Anonymous'
+						activeFallbackComponentNames.push(componentName)
+					}
+				}
 
 				function enhanceExistingHook(existingHook) {
 					const originalInject = existingHook.inject
+					const originalCommitFiberRoot = existingHook.onCommitFiberRoot
 
 					existingHook.inject = (injectedInternals) => {
 						internals = injectedInternals
@@ -23,6 +84,12 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 						return originalInject?.call(existingHook, injectedInternals) ?? 1
 					}
 
+					existingHook.onCommitFiberRoot = (...args) => {
+						const [, root] = args
+						collectRenderedComponentsFromCommit(root)
+						return originalCommitFiberRoot?.apply(existingHook, args)
+					}
+
 					return existingHook
 				}
 
@@ -34,7 +101,9 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 							internals = injectedInternals
 							return 1 // Returning a number as React expects a renderer ID
 						},
-						onCommitFiberRoot: () => {},
+						onCommitFiberRoot: (_rendererId, root) => {
+							collectRenderedComponentsFromCommit(root)
+						},
 						onCommitFiberUnmount: () => {},
 					}
 				}
@@ -45,19 +114,32 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 						throw new Error('🚨 React DevTools is not available')
 					}
 
-					internals.enableProfilerTimer = true
-					internals.enableProfilerCommitHooks = true
-					internals.injectProfilingHooks({
-						markComponentRenderStarted: (fiber) => {
-							componentNames.push(fiber.type.name || 'Anonymous')
-						},
-					})
-
-					await cb()
+					const supportsInjectedProfilingHooks =
+						typeof internals.injectProfilingHooks === 'function'
+
+					if (supportsInjectedProfilingHooks) {
+						internals.enableProfilerTimer = true
+						internals.enableProfilerCommitHooks = true
+						internals.injectProfilingHooks({
+							markComponentRenderStarted: (fiber) => {
+								componentNames.push(fiber.type.name || 'Anonymous')
+							},
+						})
+					} else {
+						activeFallbackComponentNames = componentNames
+					}
 
-					internals.enableProfilerTimer = false
-					internals.enableProfilerCommitHooks = false
-					internals.injectProfilingHooks(null)
+					try {
+						await cb()
+					} finally {
+						if (supportsInjectedProfilingHooks) {
+							internals.enableProfilerTimer = false
+							internals.enableProfilerCommitHooks = false
+							internals.injectProfilingHooks(null)
+						} else {
+							activeFallbackComponentNames = null
+						}
+					}
 
 					return componentNames
 				}
diff --git a/exercises/06.rerenders/03.problem.primitives/tests/memoized.test.ts b/exercises/06.rerenders/03.problem.primitives/tests/memoized.test.ts
index a1025d863..4e267d303 100644
--- a/exercises/06.rerenders/03.problem.primitives/tests/memoized.test.ts
+++ b/exercises/06.rerenders/03.problem.primitives/tests/memoized.test.ts
@@ -12,9 +12,70 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 		const scriptToInject = `
 			<script>
 				let internals
+				const PerformedWorkFlag = 0b000000000000000000000000001
+				const UserCodeFiberTags = new Set([0, 1, 9, 11, 15])
+
+				let activeFallbackComponentNames = null
+
+				function isUserCodeFiberTag(tag) {
+					return UserCodeFiberTags.has(tag)
+				}
+
+				function getDisplayNameFromType(type) {
+					if (!type) return null
+
+					if (typeof type === 'function') {
+						return type.displayName || type.name || null
+					}
+
+					if (typeof type === 'object') {
+						if (typeof type.displayName === 'string' && type.displayName) {
+							return type.displayName
+						}
+
+						if (typeof type.render === 'function') {
+							return type.render.displayName || type.render.name || null
+						}
+
+						if (type.type) {
+							return getDisplayNameFromType(type.type)
+						}
+					}
+
+					return null
+				}
+
+				function getFiberDisplayName(fiber) {
+					return getDisplayNameFromType(fiber.type) || getDisplayNameFromType(fiber.elementType)
+				}
+
+				function didFiberRender(previousFiber, nextFiber) {
+					if (!previousFiber) return true
+					return (nextFiber.flags & PerformedWorkFlag) === PerformedWorkFlag
+				}
+
+				function collectRenderedComponentsFromCommit(root) {
+					if (!activeFallbackComponentNames || !root?.current) return
+
+					const stack = [root.current]
+					while (stack.length > 0) {
+						const fiber = stack.pop()
+						if (!fiber) continue
+
+						if (fiber.sibling) stack.push(fiber.sibling)
+						if (fiber.child) stack.push(fiber.child)
+
+						if (!isUserCodeFiberTag(fiber.tag)) continue
+						if (!didFiberRender(fiber.alternate, fiber)) continue
+
+						const componentName = getFiberDisplayName(fiber) ?? 'Anonymous'
+						activeFallbackComponentNames.push(componentName)
+					}
+				}
 
 				function enhanceExistingHook(existingHook) {
 					const originalInject = existingHook.inject
+					const originalCommitFiberRoot = existingHook.onCommitFiberRoot
 
 					existingHook.inject = (injectedInternals) => {
 						internals = injectedInternals
@@ -23,6 +84,12 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 						return originalInject?.call(existingHook, injectedInternals) ?? 1
 					}
 
+					existingHook.onCommitFiberRoot = (...args) => {
+						const [, root] = args
+						collectRenderedComponentsFromCommit(root)
+						return originalCommitFiberRoot?.apply(existingHook, args)
+					}
+
 					return existingHook
 				}
 
@@ -34,7 +101,9 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 							internals = injectedInternals
 							return 1 // Returning a number as React expects a renderer ID
 						},
-						onCommitFiberRoot: () => {},
+						onCommitFiberRoot: (_rendererId, root) => {
+							collectRenderedComponentsFromCommit(root)
+						},
 						onCommitFiberUnmount: () => {},
 					}
 				}
@@ -45,19 +114,32 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 						throw new Error('🚨 React DevTools is not available')
 					}
 
-					internals.enableProfilerTimer = true
-					internals.enableProfilerCommitHooks = true
-					internals.injectProfilingHooks({
-						markComponentRenderStarted: (fiber) => {
-							componentNames.push(fiber.type.name || 'Anonymous')
-						},
-					})
-
-					await cb()
+					const supportsInjectedProfilingHooks =
+						typeof internals.injectProfilingHooks === 'function'
+
+					if (supportsInjectedProfilingHooks) {
+						internals.enableProfilerTimer = true
+						internals.enableProfilerCommitHooks = true
+						internals.injectProfilingHooks({
+							markComponentRenderStarted: (fiber) => {
+								componentNames.push(fiber.type.name || 'Anonymous')
+							},
+						})
+					} else {
+						activeFallbackComponentNames = componentNames
+					}
 
-					internals.enableProfilerTimer = false
-					internals.enableProfilerCommitHooks = false
-					internals.injectProfilingHooks(null)
+					try {
+						await cb()
+					} finally {
+						if (supportsInjectedProfilingHooks) {
+							internals.enableProfilerTimer = false
+							internals.enableProfilerCommitHooks = false
+							internals.injectProfilingHooks(null)
+						} else {
+							activeFallbackComponentNames = null
+						}
+					}
 
 					return componentNames
 				}
diff --git a/exercises/06.rerenders/03.solution.primitives/tests/memoized.test.ts b/exercises/06.rerenders/03.solution.primitives/tests/memoized.test.ts
index a1025d863..4e267d303 100644
--- a/exercises/06.rerenders/03.solution.primitives/tests/memoized.test.ts
+++ b/exercises/06.rerenders/03.solution.primitives/tests/memoized.test.ts
@@ -12,9 +12,70 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 		const scriptToInject = `
 			<script>
 				let internals
+				const PerformedWorkFlag = 0b000000000000000000000000001
+				const UserCodeFiberTags = new Set([0, 1, 9, 11, 15])
+
+				let activeFallbackComponentNames = null
+
+				function isUserCodeFiberTag(tag) {
+					return UserCodeFiberTags.has(tag)
+				}
+
+				function getDisplayNameFromType(type) {
+					if (!type) return null
+
+					if (typeof type === 'function') {
+						return type.displayName || type.name || null
+					}
+
+					if (typeof type === 'object') {
+						if (typeof type.displayName === 'string' && type.displayName) {
+							return type.displayName
+						}
+
+						if (typeof type.render === 'function') {
+							return type.render.displayName || type.render.name || null
+						}
+
+						if (type.type) {
+							return getDisplayNameFromType(type.type)
+						}
+					}
+
+					return null
+				}
+
+				function getFiberDisplayName(fiber) {
+					return getDisplayNameFromType(fiber.type) || getDisplayNameFromType(fiber.elementType)
+				}
+
+				function didFiberRender(previousFiber, nextFiber) {
+					if (!previousFiber) return true
+					return (nextFiber.flags & PerformedWorkFlag) === PerformedWorkFlag
+				}
+
+				function collectRenderedComponentsFromCommit(root) {
+					if (!activeFallbackComponentNames || !root?.current) return
+
+					const stack = [root.current]
+					while (stack.length > 0) {
+						const fiber = stack.pop()
+						if (!fiber) continue
+
+						if (fiber.sibling) stack.push(fiber.sibling)
+						if (fiber.child) stack.push(fiber.child)
+
+						if (!isUserCodeFiberTag(fiber.tag)) continue
+						if (!didFiberRender(fiber.alternate, fiber)) continue
+
+						const componentName = getFiberDisplayName(fiber) ?? 'Anonymous'
+						activeFallbackComponentNames.push(componentName)
+					}
+				}
 
 				function enhanceExistingHook(existingHook) {
 					const originalInject = existingHook.inject
+					const originalCommitFiberRoot = existingHook.onCommitFiberRoot
 
 					existingHook.inject = (injectedInternals) => {
 						internals = injectedInternals
@@ -23,6 +84,12 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 						return originalInject?.call(existingHook, injectedInternals) ?? 1
 					}
 
+					existingHook.onCommitFiberRoot = (...args) => {
+						const [, root] = args
+						collectRenderedComponentsFromCommit(root)
+						return originalCommitFiberRoot?.apply(existingHook, args)
+					}
+
 					return existingHook
 				}
 
@@ -34,7 +101,9 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 							internals = injectedInternals
 							return 1 // Returning a number as React expects a renderer ID
 						},
-						onCommitFiberRoot: () => {},
+						onCommitFiberRoot: (_rendererId, root) => {
+							collectRenderedComponentsFromCommit(root)
+						},
 						onCommitFiberUnmount: () => {},
 					}
 				}
@@ -45,19 +114,32 @@ test('Only two ListItems should not rerender when the highlighted item changes',
 						throw new Error('🚨 React DevTools is not available')
 					}
 
-					internals.enableProfilerTimer = true
-					internals.enableProfilerCommitHooks = true
-					internals.injectProfilingHooks({
-						markComponentRenderStarted: (fiber) => {
-							componentNames.push(fiber.type.name || 'Anonymous')
-						},
-					})
-
-					await cb()
+					const supportsInjectedProfilingHooks =
+						typeof internals.injectProfilingHooks === 'function'
+
+					if (supportsInjectedProfilingHooks) {
+						internals.enableProfilerTimer = true
+						internals.enableProfilerCommitHooks = true
+						internals.injectProfilingHooks({
+							markComponentRenderStarted: (fiber) => {
+								componentNames.push(fiber.type.name || 'Anonymous')
+							},
+						})
+					} else {
+						activeFallbackComponentNames = componentNames
+					}
 
-					internals.enableProfilerTimer = false
-					internals.enableProfilerCommitHooks = false
-					internals.injectProfilingHooks(null)
+					try {
+						await cb()
+					} finally {
+						if (supportsInjectedProfilingHooks) {
+							internals.enableProfilerTimer = false
+							internals.enableProfilerCommitHooks = false
+							internals.injectProfilingHooks(null)
+						} else {
+							activeFallbackComponentNames = null
+						}
+					}
 
 					return componentNames
 				}
diff --git a/shared/get-component-calls.tsx b/shared/get-component-calls.tsx
index c2b17afbf..4079a2113 100644
--- a/shared/get-component-calls.tsx
+++ b/shared/get-component-calls.tsx
@@ -6,8 +6,80 @@ declare global {
 
 let internals: any
 
+const PerformedWorkFlag = 0b000000000000000000000000001
+const FunctionComponentTag = 0
+const ClassComponentTag = 1
+const ContextConsumerTag = 9
+const ForwardRefTag = 11
+const SimpleMemoComponentTag = 15
+
+let activeFallbackComponentNames: Array<string> | null = null
+
+function isUserCodeFiberTag(tag: number) {
+	return (
+		tag === FunctionComponentTag ||
+		tag === ClassComponentTag ||
+		tag === ContextConsumerTag ||
+		tag === ForwardRefTag ||
+		tag === SimpleMemoComponentTag
+	)
+}
+
+function getDisplayNameFromType(type: any): string | null {
+	if (!type) return null
+
+	if (typeof type === 'function') {
+		return type.displayName || type.name || null
+	}
+
+	if (typeof type === 'object') {
+		if (typeof type.displayName === 'string' && type.displayName) {
+			return type.displayName
+		}
+
+		if (typeof type.render === 'function') {
+			return type.render.displayName || type.render.name || null
+		}
+
+		if (type.type) {
+			return getDisplayNameFromType(type.type)
+		}
+	}
+
+	return null
+}
+
+function getFiberDisplayName(fiber: any) {
+	return getDisplayNameFromType(fiber.type) || getDisplayNameFromType(fiber.elementType)
+}
+
+function didFiberRender(previousFiber: any, nextFiber: any) {
+	if (!previousFiber) return true
+	return (nextFiber.flags & PerformedWorkFlag) === PerformedWorkFlag
+}
+
+function collectRenderedComponentsFromCommit(root: any) {
+	if (!activeFallbackComponentNames || !root?.current) return
+
+	const stack = [root.current]
+	while (stack.length > 0) {
+		const fiber = stack.pop()
+		if (!fiber) continue
+
+		if (fiber.sibling) stack.push(fiber.sibling)
+		if (fiber.child) stack.push(fiber.child)
+
+		if (!isUserCodeFiberTag(fiber.tag)) continue
+		if (!didFiberRender(fiber.alternate, fiber)) continue
+
+		const componentName = getFiberDisplayName(fiber) ?? 'Anonymous'
+		activeFallbackComponentNames.push(componentName)
+	}
+}
+
 function enhanceExistingHook(existingHook: any) {
 	const originalInject = existingHook.inject
+	const originalCommitFiberRoot = existingHook.onCommitFiberRoot
 
 	existingHook.inject = (injectedInternals: any) => {
 		internals = injectedInternals
@@ -16,6 +88,12 @@ function enhanceExistingHook(existingHook: any) {
 		return originalInject?.call(existingHook, injectedInternals) ?? 1
 	}
 
+	existingHook.onCommitFiberRoot = (...args: Array<any>) => {
+		const [, root] = args
+		collectRenderedComponentsFromCommit(root)
+		return originalCommitFiberRoot?.apply(existingHook, args)
+	}
+
 	return existingHook
 }
 
@@ -26,7 +104,9 @@ function createMinimalHook() {
 			internals = injectedInternals
 			return 1 // Returning a number as React expects a renderer ID
 		},
-		onCommitFiberRoot: () => {},
+		onCommitFiberRoot: (_rendererId: number, root: any) => {
+			collectRenderedComponentsFromCommit(root)
+		},
 		onCommitFiberUnmount: () => {},
 	}
 }
@@ -37,19 +117,32 @@ export async function getComponentCalls(cb: () => void | Promise<void>) {
 		throw new Error('🚨 React DevTools is not available')
 	}
 
-	internals.enableProfilerTimer = true
-	internals.enableProfilerCommitHooks = true
-	internals.injectProfilingHooks({
-		markComponentRenderStarted: (fiber: any) => {
-			componentNames.push(fiber.type.name || 'Anonymous')
-		},
-	})
+	const supportsInjectedProfilingHooks =
+		typeof internals.injectProfilingHooks === 'function'
 
-	await cb()
+	if (supportsInjectedProfilingHooks) {
+		internals.enableProfilerTimer = true
+		internals.enableProfilerCommitHooks = true
+		internals.injectProfilingHooks({
+			markComponentRenderStarted: (fiber: any) => {
+				componentNames.push(fiber.type.name || 'Anonymous')
+			},
+		})
+	} else {
+		activeFallbackComponentNames = componentNames
+	}
 
-	internals.enableProfilerTimer = false
-	internals.enableProfilerCommitHooks = false
-	internals.injectProfilingHooks(null)
+	try {
+		await cb()
+	} finally {
+		if (supportsInjectedProfilingHooks) {
+			internals.enableProfilerTimer = false
+			internals.enableProfilerCommitHooks = false
+			internals.injectProfilingHooks(null)
+		} else {
+			activeFallbackComponentNames = null
+		}
+	}
 
 	return componentNames
 }