fix(core): Resume tool calls for deferred tools that a skill loaded (backport to release-candidate/2.43.x) (#40746)

Co-authored-by: Raúl Gómez Morales <raul00gm@gmail.com>
Co-authored-by: Mutasem Aldmour <mutasem@n8n.io>

packages/@n8n/agents/src/runtime/__tests__/agent-runtime.test.ts

@@ -8753,6 +8753,55 @@ describe('AgentRuntime — mid-run observation', () => {
 		expect(JSON.stringify(capturedCall(2))).not.toContain('Old workflow policy.');
 	});
 
+	it('resumes a deferred tool that a skill dependency loaded', async () => {
+		const source = createRuntimeSkillSource([
+			{
+				id: 'planning',
+				name: 'planning',
+				description: 'Plan multi-step work.',
+				instructions: 'Ask the user to approve the plan.',
+				dependencies: { tools: ['approve'] },
+			},
+		]);
+		const checkpointStore = makeClaimingCheckpointStore();
+		const memory = new InMemoryMemory();
+		const options = {
+			skillSource: source,
+			tools: createRuntimeSkillTools(source),
+			deferredTools: [makeInterruptibleTool()],
+			checkpointStorage: checkpointStore,
+		};
+		const first = buildMidRunRuntime(memory, options);
+		generateText
+			.mockResolvedValueOnce(
+				makeGenerateWithToolCall('load-planning', 'load_skill', { skillId: 'planning' }),
+			)
+			.mockResolvedValueOnce(
+				makeGenerateWithToolCall('confirm', 'approve', { question: 'Run the plan?' }),
+			);
+		const result = await first.generate('Plan it', { persistence: PERSISTENCE });
+		await first.dispose();
+		const suspension = result.pendingSuspend?.[0];
+		if (!suspension) throw new Error('Expected a plan confirmation');
+
+		const resumed = buildMidRunRuntime(memory, options);
+		generateText.mockResolvedValueOnce(makeGenerateSuccess('Plan approved.'));
+		const resumeResult = await resumed.resume(
+			'generate',
+			{ approved: true },
+			{ runId: suspension.runId, toolCallId: suspension.toolCallId },
+		);
+		await resumed.dispose();
+
+		expect(resumeResult.error).toBeUndefined();
+		expect(resumeResult.toolCalls).toEqual(
+			expect.arrayContaining([
+				expect.objectContaining({ tool: 'approve', output: { approved: true } }),
+			]),
+		);
+		expect(capturedCall(2).tools).toHaveProperty('approve');
+	});
+
 	it('merges system messages after compaction for custom OpenAI-compatible endpoints', async () => {
 		const memory = new InMemoryMemory();
 		const runtime = buildMidRunRuntime(memory, {

packages/@n8n/agents/src/runtime/loop/agent-runtime.ts

@@ -509,9 +509,11 @@ export class AgentRuntime {
 
 		const list = await this.restoreCheckpointMessages(state);
 
-		const tool = this.context
-			.getCurrentTools(state.persistence)
-			.find((t) => t.name === toolCall.toolName);
+		// A skill dependency loads a deferred tool without a `load_tool` record, and
+		// skills restore only when the loop starts. Accept any registered deferred tool.
+		const tool =
+			this.context.getCurrentTools(state.persistence).find((t) => t.name === toolCall.toolName) ??
+			this.deferredToolManager?.getTool(toolCall.toolName);
 		if (!tool) throw new Error(`Tool ${toolCall.toolName} not found`);
 
 		const resumeSchema = toolCall.suspended ? toolCall.resumeSchema : tool.resumeSchema;

packages/@n8n/agents/src/runtime/tools/deferred-tool-manager.ts

@@ -136,6 +136,11 @@ export class DeferredToolManager {
 		return [this.searchTool, this.loadTool];
 	}
 
+	/** A registered deferred tool, loaded or not. */
+	getTool(name: string): BuiltTool | undefined {
+		return this.toolsByName.get(name);
+	}
+
 	getLoadedTools(): BuiltTool[] {
 		return Array.from(this.loadedToolNames)
 			.map((name) => this.toolsByName.get(name))