feat: AI Workflow Builder backend (no-changelog) (#14837)

packages/cli/package.json

@@ -100,6 +100,7 @@
     "@n8n/n8n-nodes-langchain": "workspace:*",
     "@n8n/permissions": "workspace:*",
     "@n8n/task-runner": "workspace:*",
+    "@n8n/ai-workflow-builder": "workspace:*",
     "@n8n/typeorm": "0.3.20-12",
     "@n8n_io/ai-assistant-sdk": "1.13.0",
     "@n8n_io/license-sdk": "2.20.0",

packages/cli/src/controllers/__tests__/ai.controller.test.ts

@@ -8,14 +8,15 @@ import { mock } from 'jest-mock-extended';
 
 import { InternalServerError } from '@/errors/response-errors/internal-server.error';
 import type { AuthenticatedRequest } from '@/requests';
+import type { WorkflowBuilderService } from '@/services/ai-workflow-builder.service';
 import type { AiService } from '@/services/ai.service';
 
 import { AiController, type FlushableResponse } from '../ai.controller';
 
 describe('AiController', () => {
 	const aiService = mock<AiService>();
-
-	const controller = new AiController(aiService, mock(), mock());
+	const workflowBuilderService = mock<WorkflowBuilderService>();
+	const controller = new AiController(aiService, workflowBuilderService, mock(), mock());
 
 	const request = mock<AuthenticatedRequest>({
 		user: { id: 'user123' },

packages/cli/src/controllers/ai.controller.ts

@@ -4,6 +4,7 @@ import {
 	AiApplySuggestionRequestDto,
 	AiAskRequestDto,
 	AiFreeCreditsRequestDto,
+	AiBuilderChatRequestDto,
 } from '@n8n/api-types';
 import { Body, Post, RestController } from '@n8n/decorators';
 import type { AiAssistantSDK } from '@n8n_io/ai-assistant-sdk';
@@ -16,6 +17,7 @@ import { FREE_AI_CREDITS_CREDENTIAL_NAME } from '@/constants';
 import { CredentialsService } from '@/credentials/credentials.service';
 import { InternalServerError } from '@/errors/response-errors/internal-server.error';
 import { AuthenticatedRequest } from '@/requests';
+import { WorkflowBuilderService } from '@/services/ai-workflow-builder.service';
 import { AiService } from '@/services/ai.service';
 import { UserService } from '@/services/user.service';
 
@@ -25,10 +27,40 @@ export type FlushableResponse = Response & { flush: () => void };
 export class AiController {
 	constructor(
 		private readonly aiService: AiService,
+		private readonly workflowBuilderService: WorkflowBuilderService,
 		private readonly credentialsService: CredentialsService,
 		private readonly userService: UserService,
 	) {}
 
+	@Post('/build', { rateLimit: { limit: 100 } })
+	async build(
+		req: AuthenticatedRequest,
+		res: FlushableResponse,
+		@Body payload: AiBuilderChatRequestDto,
+	) {
+		try {
+			const aiResponse = this.workflowBuilderService.chat(
+				{
+					question: payload.payload.question ?? '',
+				},
+				req.user,
+			);
+
+			res.header('Content-type', 'application/json-lines').flush();
+
+			// Handle the stream
+			for await (const chunk of aiResponse) {
+				res.flush();
+				res.write(JSON.stringify(chunk) + '⧉⇋⇋➽⌑⧉§§\n');
+			}
+
+			res.end();
+		} catch (e) {
+			assert(e instanceof Error);
+			throw new InternalServerError(e.message, e);
+		}
+	}
+
 	@Post('/chat', { rateLimit: { limit: 100 } })
 	async chat(req: AuthenticatedRequest, res: FlushableResponse, @Body payload: AiChatRequestDto) {
 		try {

packages/cli/src/services/ai-workflow-builder.service.ts

@@ -0,0 +1,40 @@
+import { AiWorkflowBuilderService } from '@n8n/ai-workflow-builder';
+import { GlobalConfig } from '@n8n/config';
+import { Service } from '@n8n/di';
+import type { IUser } from 'n8n-workflow';
+
+import { N8N_VERSION } from '@/constants';
+import { License } from '@/license';
+import { NodeTypes } from '@/node-types';
+
+/**
+ * This service wraps the actual AiWorkflowBuilderService to avoid circular dependencies.
+ * Instead of extending, we're delegating to the real service which is created on-demand.
+ */
+@Service()
+export class WorkflowBuilderService {
+	private service: AiWorkflowBuilderService | undefined;
+
+	constructor(
+		private readonly nodeTypes: NodeTypes,
+		private readonly license: License,
+		private readonly config: GlobalConfig,
+	) {}
+
+	private getService(): AiWorkflowBuilderService {
+		if (!this.service) {
+			this.service = new AiWorkflowBuilderService(
+				this.license,
+				this.nodeTypes,
+				this.config,
+				N8N_VERSION,
+			);
+		}
+		return this.service;
+	}
+
+	async *chat(payload: { question: string }, user: IUser) {
+		const service = this.getService();
+		yield* service.chat(payload, user);
+	}
+}