Use OpenRouter in n8n versions <1.78

What it is: In version 1.78, n8n introduced a dedicated node to use the OpenRouter service, which lets you to use a lot of different LLM models and providers and change models on the fly in an agentic workflow. For prior n8n versions, there's a workaround to make OpenRouter accessible, by using the OpenAI node with a OpenRouter-specific BaseURL. This trivial workflow demonstrates this for version before 1.78, so that you can use different LLM model dynamically with the available n8n nodes for OpenAI LLM and OpenAI credentials. What you can do: Use any of the OpenRouter models Have the model even dynamically configured or changing (by some external config, some rule, or some specific chat mes

Help me set up the n8n workflow "Use OpenRouter in n8n versions <1.78" (https://n8n.io/workflows/2897). It uses: AI Agent, OpenAI Chat Model, Simple Memory. Import the template JSON into my n8n instance, list every credential I need to create, and walk me through testing it.