diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index c753ef72f2462..10e4324721ba7 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -995,7 +995,7 @@ declare module 'vscode' {
 		 * [Pseudoterminal.onDidClose](#Pseudoterminal.onDidClose).
 		 * @param callback The callback that will be called when the task is started by a user.
 		 */
-		constructor(callback: (resolvedDefinition?: TaskDefinition) => Thenable<Pseudoterminal>);
+		constructor(callback: (resolvedDefinition: TaskDefinition) => Thenable<Pseudoterminal>);
 	}
 	//#endregion
 
diff --git a/src/vs/workbench/api/browser/mainThreadTask.ts b/src/vs/workbench/api/browser/mainThreadTask.ts
index 586acc3ab8d42..d94b7f3dfcb4b 100644
--- a/src/vs/workbench/api/browser/mainThreadTask.ts
+++ b/src/vs/workbench/api/browser/mainThreadTask.ts
@@ -414,10 +414,16 @@ export class MainThreadTask implements MainThreadTaskShape {
 	) {
 		this._proxy = extHostContext.getProxy(ExtHostContext.ExtHostTask);
 		this._providers = new Map();
-		this._taskService.onDidStateChange((event: TaskEvent) => {
+		this._taskService.onDidStateChange(async (event: TaskEvent) => {
 			const task = event.__task!;
 			if (event.kind === TaskEventKind.Start) {
-				this._proxy.$onDidStartTask(TaskExecutionDTO.from(task.getTaskExecution()), event.terminalId!);
+				const execution = TaskExecutionDTO.from(task.getTaskExecution());
+				let resolvedDefinition: TaskDefinitionDTO | undefined;
+				if (execution.task && execution.task.execution && CustomExecutionDTO.is(execution.task.execution)) {
+					resolvedDefinition = await this._configurationResolverService.resolveWithInteractionReplace(task.getWorkspaceFolder(),
+						execution.task.definition, 'tasks');
+				}
+				this._proxy.$onDidStartTask(execution, event.terminalId!, resolvedDefinition);
 			} else if (event.kind === TaskEventKind.ProcessStarted) {
 				this._proxy.$onDidStartTaskProcess(TaskProcessStartedDTO.from(task.getTaskExecution(), event.processId!));
 			} else if (event.kind === TaskEventKind.ProcessEnded) {
diff --git a/src/vs/workbench/api/common/extHost.protocol.ts b/src/vs/workbench/api/common/extHost.protocol.ts
index 1c7e49f5c97f4..fcee75d3127fd 100644
--- a/src/vs/workbench/api/common/extHost.protocol.ts
+++ b/src/vs/workbench/api/common/extHost.protocol.ts
@@ -1448,7 +1448,7 @@ export interface ExtHostSCMShape {
 export interface ExtHostTaskShape {
 	$provideTasks(handle: number, validTypes: { [key: string]: boolean; }): Thenable<tasks.TaskSetDTO>;
 	$resolveTask(handle: number, taskDTO: tasks.TaskDTO): Thenable<tasks.TaskDTO | undefined>;
-	$onDidStartTask(execution: tasks.TaskExecutionDTO, terminalId: number): void;
+	$onDidStartTask(execution: tasks.TaskExecutionDTO, terminalId: number, resolvedDefinition?: tasks.TaskDefinitionDTO): void;
 	$onDidStartTaskProcess(value: tasks.TaskProcessStartedDTO): void;
 	$onDidEndTaskProcess(value: tasks.TaskProcessEndedDTO): void;
 	$OnDidEndTask(execution: tasks.TaskExecutionDTO): void;
diff --git a/src/vs/workbench/api/common/extHostTask.ts b/src/vs/workbench/api/common/extHostTask.ts
index 610e10ec65e22..f77a862606742 100644
--- a/src/vs/workbench/api/common/extHostTask.ts
+++ b/src/vs/workbench/api/common/extHostTask.ts
@@ -475,11 +475,7 @@ export abstract class ExtHostTaskBase implements ExtHostTaskShape, IExtHostTask
 		return this._onDidExecuteTask.event;
 	}
 
-	protected async resolveDefinition(uri: number | UriComponents | undefined, definition: vscode.TaskDefinition | undefined): Promise<vscode.TaskDefinition | undefined> {
-		return definition;
-	}
-
-	public async $onDidStartTask(execution: tasks.TaskExecutionDTO, terminalId: number): Promise<void> {
+	public async $onDidStartTask(execution: tasks.TaskExecutionDTO, terminalId: number, resolvedDefinition?: tasks.TaskDefinitionDTO): Promise<void> {
 		const customExecution: types.CustomExecution | undefined = this._providedCustomExecutions2.get(execution.id);
 		if (customExecution) {
 			if (this._activeCustomExecutions2.get(execution.id) !== undefined) {
@@ -488,7 +484,7 @@ export abstract class ExtHostTaskBase implements ExtHostTaskShape, IExtHostTask
 
 			// Clone the custom execution to keep the original untouched. This is important for multiple runs of the same task.
 			this._activeCustomExecutions2.set(execution.id, customExecution);
-			this._terminalService.attachPtyToTerminal(terminalId, await customExecution.callback(await this.resolveDefinition(execution.task?.source.scope, execution.task?.definition)));
+			this._terminalService.attachPtyToTerminal(terminalId, await customExecution.callback(resolvedDefinition));
 		}
 		this._lastStartedTask = execution.id;
 
diff --git a/src/vs/workbench/api/node/extHostTask.ts b/src/vs/workbench/api/node/extHostTask.ts
index 311a85fa2b284..0715f6affdb42 100644
--- a/src/vs/workbench/api/node/extHostTask.ts
+++ b/src/vs/workbench/api/node/extHostTask.ts
@@ -11,7 +11,6 @@ import * as types from 'vs/workbench/api/common/extHostTypes';
 import { IExtHostWorkspace } from 'vs/workbench/api/common/extHostWorkspace';
 import type * as vscode from 'vscode';
 import * as tasks from '../common/shared/tasks';
-import * as Objects from 'vs/base/common/objects';
 import { ExtHostVariableResolverService } from 'vs/workbench/api/common/extHostDebugService';
 import { IExtHostDocumentsAndEditors } from 'vs/workbench/api/common/extHostDocumentsAndEditors';
 import { IExtHostConfiguration } from 'vs/workbench/api/common/extHostConfiguration';
@@ -123,32 +122,6 @@ export class ExtHostTask extends ExtHostTaskBase {
 		return this._variableResolver;
 	}
 
-	protected async resolveDefinition(uri: number | UriComponents | undefined, definition: vscode.TaskDefinition | undefined): Promise<vscode.TaskDefinition | undefined> {
-		if (!uri || (typeof uri === 'number') || !definition) {
-			return definition;
-		}
-		const workspaceFolder = await this._workspaceProvider.resolveWorkspaceFolder(URI.revive(uri));
-		const workspaceFolders = await this._workspaceProvider.getWorkspaceFolders2();
-		if (!workspaceFolders || !workspaceFolder) {
-			return definition;
-		}
-		const resolver = await this.getVariableResolver(workspaceFolders);
-		const ws: IWorkspaceFolder = {
-			uri: workspaceFolder.uri,
-			name: workspaceFolder.name,
-			index: workspaceFolder.index,
-			toResource: () => {
-				throw new Error('Not implemented');
-			}
-		};
-		const resolvedDefinition = Objects.deepClone(definition);
-		for (const key in resolvedDefinition) {
-			resolvedDefinition[key] = resolver.resolve(ws, resolvedDefinition[key]);
-		}
-
-		return resolvedDefinition;
-	}
-
 	public async $resolveVariables(uriComponents: UriComponents, toResolve: { process?: { name: string; cwd?: string; path?: string }, variables: string[] }): Promise<{ process?: string, variables: { [key: string]: string; } }> {
 		const uri: URI = URI.revive(uriComponents);
 		const result = {