diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5b677c92cf925..334a8ab3eb2b4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,8 @@ Breaking changes:
 
 - [task] `TaskService.getConfiguredTasks()` returns `Promise<TaskConfiguration[]>` instead of `TaskConfiguration[]` [#5777](https://github.com/theia-ide/theia/pull/5777)
 - [plugin] files from 'plugin-ext/src/api' moved to 'plugin-ext/src/common', renamed 'model.ts' to 'plugin-api-rpc-model.ts', 'plugin-api.ts' to 'plugin-api-rpc.ts'
+- [task] ensure that plugin tasks are registered before accessing them [5869](https://github.com/theia-ide/theia/pull/5869)
+  - `TaskProviderRegistry` and `TaskResolverRegistry` are promisified
 
 Breaking changes:
   - [shell][plugin] integrated view containers and views [#5665](https://github.com/theia-ide/theia/pull/5665)
diff --git a/packages/cpp/src/browser/cpp-task-provider.ts b/packages/cpp/src/browser/cpp-task-provider.ts
index 7bc023c9fb0af..1754dd7e60351 100644
--- a/packages/cpp/src/browser/cpp-task-provider.ts
+++ b/packages/cpp/src/browser/cpp-task-provider.ts
@@ -78,7 +78,7 @@ export class CppTaskProvider implements TaskContribution, TaskProvider, TaskReso
     }
 
     async resolveTask(task: CppBuildTaskConfiguration): Promise<TaskConfiguration> {
-        const resolver = this.taskResolverRegistry.getResolver('shell');
+        const resolver = await this.taskResolverRegistry.getResolver('shell');
         if (!resolver) {
             throw new Error('No shell resolver found, cannot build.');
         }
diff --git a/packages/plugin-ext/src/hosted/browser/hosted-plugin.ts b/packages/plugin-ext/src/hosted/browser/hosted-plugin.ts
index 076a1a667eb87..bd4c86a261fe8 100644
--- a/packages/plugin-ext/src/hosted/browser/hosted-plugin.ts
+++ b/packages/plugin-ext/src/hosted/browser/hosted-plugin.ts
@@ -49,6 +49,7 @@ import { FileSearchService } from '@theia/file-search/lib/common/file-search-ser
 import { isCancelled } from '@theia/core';
 import { FrontendApplicationStateService } from '@theia/core/lib/browser/frontend-application-state';
 import { PluginViewRegistry } from '../../main/browser/view/plugin-view-registry';
+import { TaskProviderRegistry, TaskResolverRegistry } from '@theia/task/lib/browser/task-contribution';
 
 export type PluginHost = 'frontend' | string;
 export type DebugActivationEvent = 'onDebugResolve' | 'onDebugInitialConfigurations' | 'onDebugAdapterProtocolTracker';
@@ -112,6 +113,12 @@ export class HostedPluginSupport {
     @inject(PluginViewRegistry)
     protected readonly viewRegistry: PluginViewRegistry;
 
+    @inject(TaskProviderRegistry)
+    protected readonly taskProviderRegistry: TaskProviderRegistry;
+
+    @inject(TaskResolverRegistry)
+    protected readonly taskResolverRegistry: TaskResolverRegistry;
+
     private theiaReadyPromise: Promise<any>;
 
     protected readonly managers: PluginManagerExt[] = [];
@@ -135,6 +142,8 @@ export class HostedPluginSupport {
         this.debugSessionManager.onWillResolveDebugConfiguration(event => this.ensureDebugActivation(event, 'onDebugResolve', event.debugType));
         this.debugConfigurationManager.onWillProvideDebugConfiguration(event => this.ensureDebugActivation(event, 'onDebugInitialConfigurations'));
         this.viewRegistry.onDidExpandView(id => this.activateByView(id));
+        this.taskProviderRegistry.onWillProvideTaskProvider(event => this.ensureTaskActivation(event));
+        this.taskResolverRegistry.onWillProvideTaskResolver(event => this.ensureTaskActivation(event));
     }
 
     checkAndLoadPlugin(container: interfaces.Container): void {
@@ -290,6 +299,10 @@ export class HostedPluginSupport {
         event.waitUntil(p);
     }
 
+    protected ensureTaskActivation(event: WaitUntilEvent): void {
+        event.waitUntil(this.activateByCommand('workbench.action.tasks.runTask'));
+    }
+
     protected ensureDebugActivation(event: WaitUntilEvent, activationEvent?: DebugActivationEvent, debugType?: string): void {
         event.waitUntil(this.activateByDebug(activationEvent, debugType));
     }
diff --git a/packages/task/src/browser/provided-task-configurations.ts b/packages/task/src/browser/provided-task-configurations.ts
index 11dfee12c2432..cf40340081dc3 100644
--- a/packages/task/src/browser/provided-task-configurations.ts
+++ b/packages/task/src/browser/provided-task-configurations.ts
@@ -37,7 +37,7 @@ export class ProvidedTaskConfigurations {
 
     /** returns a list of provided tasks */
     async getTasks(): Promise<TaskConfiguration[]> {
-        const providers = this.taskProviderRegistry.getProviders();
+        const providers = await this.taskProviderRegistry.getProviders();
         const providedTasks: TaskConfiguration[] = (await Promise.all(providers.map(p => p.provideTasks())))
             .reduce((acc, taskArray) => acc.concat(taskArray), []);
         this.cacheTasks(providedTasks);
diff --git a/packages/task/src/browser/task-contribution.ts b/packages/task/src/browser/task-contribution.ts
index 7693e3119d644..8cd2df128857e 100644
--- a/packages/task/src/browser/task-contribution.ts
+++ b/packages/task/src/browser/task-contribution.ts
@@ -17,6 +17,7 @@
 import { injectable, postConstruct } from 'inversify';
 import { Disposable } from '@theia/core/lib/common/disposable';
 import { TaskConfiguration } from '../common/task-protocol';
+import { WaitUntilEvent, Emitter } from '@theia/core/lib/common/event';
 
 export const TaskContribution = Symbol('TaskContribution');
 
@@ -39,6 +40,9 @@ export interface TaskProvider {
 @injectable()
 export class TaskResolverRegistry {
 
+    protected readonly onWillProvideTaskResolverEmitter = new Emitter<WaitUntilEvent>();
+    readonly onWillProvideTaskResolver = this.onWillProvideTaskResolverEmitter.event;
+
     protected resolvers: Map<string, TaskResolver>;
 
     @postConstruct()
@@ -54,7 +58,8 @@ export class TaskResolverRegistry {
         };
     }
 
-    getResolver(type: string): TaskResolver | undefined {
+    async getResolver(type: string): Promise<TaskResolver | undefined> {
+        await WaitUntilEvent.fire(this.onWillProvideTaskResolverEmitter, {});
         return this.resolvers.get(type);
     }
 }
@@ -62,6 +67,9 @@ export class TaskResolverRegistry {
 @injectable()
 export class TaskProviderRegistry {
 
+    protected readonly onWillProvideTaskProviderEmitter = new Emitter<WaitUntilEvent>();
+    readonly onWillProvideTaskProvider = this.onWillProvideTaskProviderEmitter.event;
+
     protected providers: Map<string, TaskProvider>;
 
     @postConstruct()
@@ -78,12 +86,14 @@ export class TaskProviderRegistry {
         };
     }
 
-    getProvider(type: string): TaskProvider | undefined {
+    async getProvider(type: string): Promise<TaskProvider | undefined> {
+        await WaitUntilEvent.fire(this.onWillProvideTaskProviderEmitter, {});
         return this.providers.get(type);
     }
 
     /** Returns all registered Task Providers. */
-    getProviders(): TaskProvider[] {
+    async getProviders(): Promise<TaskProvider[]> {
+        await WaitUntilEvent.fire(this.onWillProvideTaskProviderEmitter, {});
         return [...this.providers.values()];
     }
 }
diff --git a/packages/task/src/browser/task-service.ts b/packages/task/src/browser/task-service.ts
index f98f6164ee02e..5ce0c6f31d288 100644
--- a/packages/task/src/browser/task-service.ts
+++ b/packages/task/src/browser/task-service.ts
@@ -366,7 +366,7 @@ export class TaskService implements TaskConfigurationClient {
             }
         }
 
-        const resolver = this.taskResolverRegistry.getResolver(task.type);
+        const resolver = await this.taskResolverRegistry.getResolver(task.type);
         let resolvedTask: TaskConfiguration;
         try {
             resolvedTask = resolver ? await resolver.resolveTask(task) : task;
diff --git a/tsconfig.json b/tsconfig.json
index 89626631288c6..fe54e5e4da180 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -126,6 +126,9 @@
       ],
       "@theia/userstorage/lib/*": [
         "packages/userstorage/src/*"
+      ],
+      "@theia/task/lib/*": [
+        "packages/task/src/*"
       ]
     },
     "plugins": [