Open WebUI: Creating Custom Agents

Open WebUI is a powerful tool that can be used to create custom agents for various tasks. It evolved from a simple Ollama chat interface to a full-fledged agent interface for any OpenAI API endpoint. The agent interface can leverage custom knowledge bases, text, images, other chat references, memory, and even execute arbitrary code through a terminal feature.

The article focuses on creating a coding agent using Open WebUI version 0.9.6, which was published on June 1, 2026. The setup and configuration examples should also work with newer versions of the software.

To create a custom coding agent, you need to follow several steps. First, select a base model that is suitable for coding tasks. In this article, the model gpt-5.4-nano was chosen due to its good input and output token cost profile. The base model is configured in the Open WebUI GUI under Workspace, then Models.

Next, you need to define a custom prompt for the agent. In this case, a system prompt was used that describes a senior Python full-stack engineer with a structured and rigorous work method. The prompt emphasizes the use of Python, strong typing, clear abstractions, explicit trade-offs, and a pragmatic approach to problem-solving.

Once the base model and prompt are set, you can configure the tools and skills required for the agent. In this setup, no special tools were added, and the agent was configured to remember knowledge from previous sessions. The memory feature allows the agent to persist stack choices and other relevant information during the coding session.

To execute the agent's tasks, the Terminal feature is utilized. This feature connects to a Docker container, allowing the agent to run arbitrary code. The Terminal setup involves configuring web search access, which requires creating an account with a search provider and obtaining an API key. The Terminal configuration is more involved and is discussed in a separate section of the article.

After configuring the base model, prompt, tools, and memory settings, you can create the custom coding agent in Open WebUI. Once the agent is set up, you can initiate chats with it to generate updates to a codebase. The agent's responses will be presented in a concise, technically sharp manner, following the guidelines provided in the custom prompt.

The agent will strive to provide working code when implementation is requested, state assumptions before designing complex solutions, and explain trade-offs briefly and clearly.