From 2925d654d14167ff8f8dad8b79be8ea0be8eddfc Mon Sep 17 00:00:00 2001
From: oleg <me@olegivaniv.com>
Date: Fri, 5 Jun 2026 15:15:45 +0200
Subject: [PATCH] fix: Use UUID thread IDs for Instance AI evals (no-changelog)
 (#31830)

---
 .../__tests__/runner-thread-id.test.ts        | 40 +++++++++++++++++++
 .../evaluations/computer-use/chat.ts          |  2 +-
 .../instance-ai/evaluations/harness/runner.ts |  2 +-
 3 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 packages/@n8n/instance-ai/evaluations/__tests__/runner-thread-id.test.ts

diff --git a/packages/@n8n/instance-ai/evaluations/__tests__/runner-thread-id.test.ts b/packages/@n8n/instance-ai/evaluations/__tests__/runner-thread-id.test.ts
new file mode 100644
index 00000000000..722ebc69037
--- /dev/null
+++ b/packages/@n8n/instance-ai/evaluations/__tests__/runner-thread-id.test.ts
@@ -0,0 +1,40 @@
+import { vi } from 'vitest';
+
+import type { N8nClient } from '../clients/n8n-client';
+import type { EvalLogger } from '../harness/logger';
+import { buildWorkflow } from '../harness/runner';
+
+const silentLogger: EvalLogger = {
+	info: () => {},
+	verbose: () => {},
+	success: () => {},
+	warn: () => {},
+	error: () => {},
+	isVerbose: false,
+};
+
+const uuidV4Pattern = /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/;
+
+describe('buildWorkflow thread IDs', () => {
+	it('uses UUID thread IDs accepted by the instance-ai thread endpoint', async () => {
+		let capturedThreadId = '';
+		const client = {
+			ensureThread: vi.fn(async (threadId: string) => {
+				capturedThreadId = threadId;
+				await Promise.resolve();
+				throw new Error('stop after ensureThread');
+			}),
+		} as unknown as N8nClient;
+
+		await buildWorkflow({
+			client,
+			conversation: [{ role: 'user', text: 'build a workflow' }],
+			preRunWorkflowIds: new Set(),
+			claimedWorkflowIds: new Set(),
+			logger: silentLogger,
+		});
+
+		expect(client.ensureThread).toHaveBeenCalledTimes(1);
+		expect(capturedThreadId).toMatch(uuidV4Pattern);
+	});
+});
diff --git a/packages/@n8n/instance-ai/evaluations/computer-use/chat.ts b/packages/@n8n/instance-ai/evaluations/computer-use/chat.ts
index 1242181231e..e107d613aaf 100644
--- a/packages/@n8n/instance-ai/evaluations/computer-use/chat.ts
+++ b/packages/@n8n/instance-ai/evaluations/computer-use/chat.ts
@@ -42,7 +42,7 @@ export interface RunChatOptions {
  */
 export async function runChat(options: RunChatOptions): Promise<ScenarioTrace> {
 	const { client, prompt, timeoutMs, logger } = options;
-	const threadId = `cu-eval-${crypto.randomUUID()}`;
+	const threadId = crypto.randomUUID();
 	const startTime = Date.now();
 
 	const abortController = new AbortController();
diff --git a/packages/@n8n/instance-ai/evaluations/harness/runner.ts b/packages/@n8n/instance-ai/evaluations/harness/runner.ts
index 0f8a5010a11..5ac2d390433 100644
--- a/packages/@n8n/instance-ai/evaluations/harness/runner.ts
+++ b/packages/@n8n/instance-ai/evaluations/harness/runner.ts
@@ -299,7 +299,7 @@ function isMultiTurnConversation(conversation: ConversationTurn[]): boolean {
 export async function buildWorkflow(config: BuildWorkflowConfig): Promise<BuildResult> {
 	const { client, conversation, logger } = config;
 	const openingMessage = conversation[0]?.text ?? '';
-	const threadId = `eval-${crypto.randomUUID()}`;
+	const threadId = crypto.randomUUID();
 	const startTime = Date.now();
 	const timeoutMs = config.timeoutMs ?? DEFAULT_TIMEOUT_MS;