diff --git a/src/vs/workbench/api/browser/mainThreadTesting.ts b/src/vs/workbench/api/browser/mainThreadTesting.ts
index 3b127f10a7909753fd790231819ec329c6f25262..95fc3e9ae7f5cacb294be61a9b6fe186f8068e1f 100644
--- a/src/vs/workbench/api/browser/mainThreadTesting.ts
+++ b/src/vs/workbench/api/browser/mainThreadTesting.ts
@@ -51,6 +51,17 @@ export class MainThreadTesting extends Disposable implements MainThreadTestingSh
 		}
 	}
 
+	/**
+	 * @inheritdoc
+	 */
+	$retireTest(extId: string): void {
+		for (const result of this.resultService.results) {
+			if (result instanceof LiveTestResult) {
+				result.retire(extId);
+			}
+		}
+	}
+
 	/**
 	 * @inheritdoc
 	 */
diff --git a/src/vs/workbench/api/common/extHost.protocol.ts b/src/vs/workbench/api/common/extHost.protocol.ts
index c6f3bd834ac15a0dad475b25df9d65ed3e80275b..a169d48fd4fd25d5c0fea020280918792722786e 100644
--- a/src/vs/workbench/api/common/extHost.protocol.ts
+++ b/src/vs/workbench/api/common/extHost.protocol.ts
@@ -1843,6 +1843,7 @@ export interface MainThreadTestingShape {
 	$publishDiff(resource: ExtHostTestingResource, uri: UriComponents, diff: TestsDiff): void;
 	$updateTestStateInRun(runId: string, testId: string, state: ITestState): void;
 	$runTests(req: RunTestsRequest, token: CancellationToken): Promise<string>;
+	$retireTest(extId: string): void;
 }
 
 // --- proxy identifiers
diff --git a/src/vs/workbench/api/common/extHostTesting.ts b/src/vs/workbench/api/common/extHostTesting.ts
index bab357e004309c15e61763e4ef1d570ad8cc79b7..e1c86d4975cd684a776570b3f222a2b025dd12cc 100644
--- a/src/vs/workbench/api/common/extHostTesting.ts
+++ b/src/vs/workbench/api/common/extHostTesting.ts
@@ -170,6 +170,14 @@ export class ExtHostTesting implements ExtHostTestingShape {
 				collection.addRoot(hierarchy.root, id);
 				Promise.resolve(hierarchy.discoveredInitialTests).then(() => collection.pushDiff([TestDiffOpType.DeltaDiscoverComplete, -1]));
 				hierarchy.onDidChangeTest(e => collection.onItemChange(e, id));
+				hierarchy.onDidInvalidateTest?.(e => {
+					const internal = collection.getTestByReference(e);
+					if (!internal) {
+						console.warn(`Received a TestProvider.onDidInvalidateTest for a test that does not currently exist.`);
+					} else {
+						this.proxy.$retireTest(internal.item.extId);
+					}
+				});
 			} catch (e) {
 				console.error(e);
 			}
diff --git a/src/vs/workbench/contrib/testing/browser/explorerProjections/hierarchalByLocation.ts b/src/vs/workbench/contrib/testing/browser/explorerProjections/hierarchalByLocation.ts
index 42fdc4e2cdb2243ee32f316b3b61197f2144ae49..d785bf0de24d514d20c6a2305d72063d1eebe34e 100644
--- a/src/vs/workbench/contrib/testing/browser/explorerProjections/hierarchalByLocation.ts
+++ b/src/vs/workbench/contrib/testing/browser/explorerProjections/hierarchalByLocation.ts
@@ -80,11 +80,14 @@ export class HierarchicalByLocationProjection extends Disposable implements ITes
 		}));
 
 		// when test states change, reflect in the tree
-		this._register(results.onTestChanged(([, { item, state, computedState }]) => {
+		// todo: optimize this to avoid needing to iterate
+		this._register(results.onTestChanged(([, { item, state, retired, computedState }]) => {
 			for (const i of this.items.values()) {
 				if (i.test.item.extId === item.extId) {
 					i.ownState = state.state;
+					i.retired = retired;
 					refreshComputedState(computedStateAccessor, i, this.addUpdated, computedState);
+					this.addUpdated(i);
 					this.updateEmitter.fire();
 					return;
 				}
@@ -229,6 +232,7 @@ export class HierarchicalByLocationProjection extends Disposable implements ITes
 		const prevState = this.results.getStateByExtId(item.test.item.extId)?.[1];
 		if (prevState) {
 			item.ownState = prevState.state.state;
+			item.retired = prevState.retired;
 			refreshComputedState(computedStateAccessor, item, this.addUpdated, prevState.computedState);
 		}
 	}
diff --git a/src/vs/workbench/contrib/testing/browser/explorerProjections/hierarchalNodes.ts b/src/vs/workbench/contrib/testing/browser/explorerProjections/hierarchalNodes.ts
index fb1dc15352670933a0072e21e4eaec981a5f4917..4e4dc956bddede92e5eb56ae5ce02d0952e21230 100644
--- a/src/vs/workbench/contrib/testing/browser/explorerProjections/hierarchalNodes.ts
+++ b/src/vs/workbench/contrib/testing/browser/explorerProjections/hierarchalNodes.ts
@@ -41,6 +41,7 @@ export class HierarchicalElement implements ITestTreeElement {
 	}
 
 	public state = TestRunState.Unset;
+	public retired = false;
 	public ownState = TestRunState.Unset;
 
 	constructor(public readonly test: InternalTestItem, public readonly parentItem: HierarchicalFolder | HierarchicalElement) {
@@ -73,6 +74,7 @@ export class HierarchicalFolder implements ITestTreeElement {
 		return Iterable.concatNested(Iterable.map(this.children, c => c.debuggable));
 	}
 
+	public retired = false;
 	public state = TestRunState.Unset;
 	public ownState = TestRunState.Unset;
 
diff --git a/src/vs/workbench/contrib/testing/browser/explorerProjections/index.ts b/src/vs/workbench/contrib/testing/browser/explorerProjections/index.ts
index 092a4f3799ceb1673aaaea4997f77ba2b5c2f132..f4176f445e5fe976297cc7ba75ab80978d48d370 100644
--- a/src/vs/workbench/contrib/testing/browser/explorerProjections/index.ts
+++ b/src/vs/workbench/contrib/testing/browser/explorerProjections/index.ts
@@ -87,6 +87,11 @@ export interface ITestTreeElement {
 	 */
 	state: TestRunState;
 
+	/**
+	 * Whether the node's test result is 'retired' -- from an outdated test run.
+	 */
+	readonly retired: boolean;
+
 	readonly ownState: TestRunState;
 	readonly label: string;
 	readonly parentItem: ITestTreeElement | null;
diff --git a/src/vs/workbench/contrib/testing/browser/media/testing.css b/src/vs/workbench/contrib/testing/browser/media/testing.css
index 9f8e820b408b09707d6bcab54afc1a535097e638..3943b0bd98d05122c4dd7c9da5eadb32c8c57e9f 100644
--- a/src/vs/workbench/contrib/testing/browser/media/testing.css
+++ b/src/vs/workbench/contrib/testing/browser/media/testing.css
@@ -41,6 +41,10 @@
 	margin-right: 0.25em;
 }
 
+.test-explorer .computed-state.retired {
+	opacity: 0.7;
+}
+
 .test-explorer .test-explorer-messages {
 	padding: 0 12px 8px;
 }
diff --git a/src/vs/workbench/contrib/testing/browser/testingExplorerView.ts b/src/vs/workbench/contrib/testing/browser/testingExplorerView.ts
index f60571440b55f900904d66c297a0e4a28a9c3f63..b1a3c35be4369896cb382aa361210bc58bb46545 100644
--- a/src/vs/workbench/contrib/testing/browser/testingExplorerView.ts
+++ b/src/vs/workbench/contrib/testing/browser/testingExplorerView.ts
@@ -628,10 +628,19 @@ class ListAccessibilityProvider implements IListAccessibilityProvider<ITestTreeE
 	}
 
 	getAriaLabel(element: ITestTreeElement): string {
-		return localize({
+		let label = localize({
 			key: 'testing.treeElementLabel',
 			comment: ['label then the unit tests state, for example "Addition Tests (Running)"'],
 		}, '{0} ({1})', element.label, testStateNames[element.state]);
+
+		if (element.retired) {
+			label = localize({
+				key: 'testing.treeElementLabelOutdated',
+				comment: ['{0} is the original label in testing.treeElementLabel'],
+			}, '{0}, outdated result', label, testStateNames[element.state]);
+		}
+
+		return label;
 	}
 }
 
@@ -708,6 +717,10 @@ class TestsRenderer implements ITreeRenderer<ITestTreeElement, FuzzyScore, TestT
 
 		const icon = testingStatesToIcons.get(element.state);
 		data.icon.className = 'computed-state ' + (icon ? ThemeIcon.asClassName(icon) : '');
+		if (element.retired) {
+			data.icon.className += ' retired';
+		}
+
 		const test = element.test;
 		if (test) {
 			if (test.item.location) {
diff --git a/src/vs/workbench/contrib/testing/common/testResultService.ts b/src/vs/workbench/contrib/testing/common/testResultService.ts
index 702630e83906b74b6863e474f2b03e5ca9e02b81..be1377587a1f5aba4d2c633ab75f82dc9b522c45 100644
--- a/src/vs/workbench/contrib/testing/common/testResultService.ts
+++ b/src/vs/workbench/contrib/testing/common/testResultService.ts
@@ -93,6 +93,7 @@ const itemToNode = (
 		item: { ...item.item },
 		state: unsetState,
 		computedState: TestRunState.Unset,
+		retired: false,
 	};
 
 	byExtId.set(n.item.extId, n);
@@ -154,6 +155,7 @@ interface ISerializedResults {
 interface TestResultItem extends IncrementalTestCollectionItem {
 	state: ITestState;
 	computedState: TestRunState;
+	retired: boolean;
 }
 
 /**
@@ -300,6 +302,28 @@ export class LiveTestResult implements ITestResult {
 		}
 	}
 
+	/**
+	 * Marks a test as retired. This can trigger it to be re-run in live mode.
+	 */
+	public retire(extId: string) {
+		const root = this.testByExtId.get(extId);
+		if (!root || root.retired) {
+			return;
+		}
+
+		const queue: Iterable<string>[] = [[root.id]];
+		while (queue.length) {
+			for (const id of queue.pop()!) {
+				const entry = this.testByInternalId.get(id);
+				if (entry && !entry.retired) {
+					entry.retired = true;
+					queue.push(entry.children);
+					this.changeEmitter.fire(entry);
+				}
+			}
+		}
+	}
+
 	/**
 	 * Adds a test, by its ID, to the test run. This can end up being called
 	 * if tests were started while discovery was still happening, so initially
@@ -363,6 +387,7 @@ class HydratedTestResult implements ITestResult {
 		for (const [key, value] of serialized.items) {
 			this.map.set(key, value);
 
+			value.retired = true;
 			for (const message of value.state.messages) {
 				if (message.location) {
 					message.location.uri = URI.revive(message.location.uri);