n8n - 💡(How to fix) Fix `POST /rest/ai/sessions` returns 500 when loading code-builder sessions (`invalid input syntax for type uuid`) [1 pull requests]

Bug Description

Loading AI Workflow Builder chat sessions fails with HTTP 500 when the backend uses a code-builder thread ID.

SessionManagerService.generateThreadId() appends a -code suffix for code-builder sessions:

// packages/@n8n/ai-workflow-builder.ee/src/utils/thread-id.ts
return agentType === 'code-builder' ? `${baseId}-code` : baseId;

Example thread ID:

workflow-RuZf36C7AWRmbiux-user-3162e4af-2f84-4fc0-84a1-ab892333a9d0-code

WorkflowBuilderSessionRepository.parseThreadId() does not strip that suffix. It parses userId as:

3162e4af-2f84-4fc0-84a1-ab892333a9d0-code

The workflow_builder_session.userId column is type uuid, so PostgreSQL rejects the query:

invalid input syntax for type uuid: "3162e4af-2f84-4fc0-84a1-ab892333a9d0-code"

AiWorkflowBuilderAgentService.getSessions() always passes agentType: 'code-builder', so this path is hit whenever sessions are loaded from persistent storage (not only when the UI experiment flag is on).

To Reproduce

1. Run n8n with PostgreSQL and AI Builder enabled (feat:aiBuilder).

2. Ensure workflow builder session persistence is active (default when workflow_builder_session table exists).

3. Open a workflow in the editor and open the AI Workflow Builder panel (or trigger session load).

4. In the browser, observe:

POST /rest/ai/sessions

Request body:

{
  "workflowId": "<workflow-id>",
  "codeBuilder": false
}

Response is 500 with a message similar to:

{
  "code": 500,
  "message": "invalid input syntax for type uuid: \"<user-uuid>-code\""
}

Note: codeBuilder: false in the request does not prevent the backend from using a code-builder thread ID today; see related notes in Debug Info.

Expected behavior

• POST /rest/ai/sessions should return 200 with { sessions: [...] } (or an empty list if no session exists).
• userId parsed from the thread ID must be a valid UUID matching the authenticated user.
• Code-builder thread IDs (…-code) should be handled consistently between session ID generation and DB lookup.

Debug Info

Affected code

Thread ID format

• Standard: workflow-{workflowId}-user-{userId}
• Code-builder: workflow-{workflowId}-user-{userId}-code

Repository parse logic (current)

const match = threadId.match(/^workflow-(.+)-user-(.+)$/);
// userId capture group incorrectly includes "-code"

Entity

• WorkflowBuilderSession.userId → @Column({ type: 'uuid' })
  (packages/cli/src/modules/workflow-builder/workflow-builder-session.entity.ts)

Suggested fix

Strip -code before parsing, e.g.:

const normalized = threadId.endsWith('-code') ? threadId.slice(0, -5) : threadId;
const match = normalized.match(/^workflow-(.+)-user-(.+)$/);

Operating System

Ubuntu

n8n Version

2.21.4

Node.js Version

24.15.0

Database

PostgreSQL

Execution mode

main (default)

Hosting

self hosted