Full-Stack n8n AI Agent Development

I am looking for a top-tier developer to perform a significant upgrade on my existing AI agent. The entire backend logic is built on n8n, so deep, demonstrable expertise with n8n is the most critical requirement for this project.

You will be responsible for debugging, optimizing, and adding major features to the n8n workflow, migrating the frontend from Durable to Squarespace, and implementing a new authentication system.

Required Skills & Expertise:

We are looking for a developer who can prove their ability in the following areas:

1. Expert-Level n8n Workflow Architecture:
• Must have extensive experience building, debugging, and scaling complex workflows in n8n.
• Proficiency with n8n's AI nodes and integrating external APIs
• Ability to confidently advise on and execute the migration from the OpenAI Assistants API to a more robust solution (like the Responses API or AI Agent node) while preserving our existing knowledge base (trained on multiple PDFs).
• Experience with solutions for making the AI "trainable" by easily adding new documents (PDFs) to its knowledge base.

2. Backend & Performance Optimization:
• Strong diagnostic skills to identify and solve critical bottlenecks. (e.g., current agent fails after 5 requests).
• Proven ability to refactor workflows for speed and stability, aiming for <2 second response times for initial acknowledgments.
• Must be able to implement scalable architecture that supports a high volume of queries (e.g., 100+ questions per user).

3. Frontend Development & UI/UX Implementation (HTML/CSS/JS):
• Ability to embed and customize a chat interface within a Squarespace website.
• Strong skills in responsive, mobile-first design to ensure the chat agent is perfectly usable in a vertical view on phones (currently users have to rotate their phone).
• Experience implementing specific UI/UX mockups, including:
o Repositioning the chat box to be "above the fold" (no scrolling required).
o Adding and styling interactive buttons ("Dry Skin," "Acne-prone," etc.) that trigger pre-set queries in the agent.

4. Third-Party API & Authentication Integration:
• Demonstrated experience integrating user authentication systems, specifically Clerk.
• Ability to build logic (within n8n and the frontend) to manage user states (guest vs. logged-in).
• Must be able to implement usage-based triggers (e.g., "show Clerk log-in pop-up after 3 guest messages") by creating a communication channel between n8n and Clerk.

5. System Migration & Integration:
• Experience migrating a live application/service from one platform (Durable) to Squarespace.
• Skill in configuring the n8n workflow to change its behavior based on the URL (e.g., sourcing links from specific UK or USA retailers).