September 2025 | Vellum | Documentation

Custom Node Colors & Icons

September 17th, 2025

You can now customize the color and icon for any Node in your Workflows! Simply click on a Node’s icon to open the customization interface, where you can choose from a variety of colors and search through a comprehensive icon library to find the perfect visual representation for your Node’s functionality.

Custom inputs for Agent Node code tool

September 15th, 2025

You can now pass inputs to the code tool that will not be populated to the model.

In the example below, input_1 is passed as an input, and the model will only populate greet. During tool calling, both inputs will be passed into the function. Code Tool Input

Raw Data for Provider Errors

September 15th, 2025

You can now see the raw response for Provider Errors that might show up when executing a Prompt. This is particularly useful when you want more context as to why a particular Prompt request to a model provider failed. Raw Data for Provider Errors

Open Definition Button for Custom Nodes

September 11th, 2025

You can now open the Code Preview for your given Custom Node with this new button. Previously, you had to manually click the Code Preview button and navigate to the specific file for the Custom Node you are interested in. Now, you can save time clicking and searching with this button. Open Definition

First-Class Image and Document Input Variables

September 10th, 2025

Previously if you wanted to pass an image or document into an LLM in Vellum, say to use the Vision capabilities similar to GPT-4 or GPT-5, you had to pass it as a Chat History variable type. This is unintuitive and difficult to set up and use. Often, you don’t want to pass a Chat History, just a file.

Now, both Prompts and Workflows have first-class support for Image and Document variable types in their Input Variables.

Screenshot showing Workflow inputs configuration with new Image and Document variable types available in the dropdown menu alongside existing String, Number, JSON, and Chat History options — New Image and Document input variable types available in Workflow configuration

Image and Document input types are also available when configuring Prompt input variables

Static Images & Documents in Prompts

September 10th, 2025

You can now attach static images and documents directly to your Prompts without needing to include them as part of a chat history input variable. This makes it much simpler to provide consistent reference materials that should be sent with every Prompt execution.

To attach a static image or document, click the paperclip icon in the Prompt editor and choose “Insert Static Attachment”. The attached files will be included automatically with every execution of your Prompt.

Screenshot showing the Prompt editor interface with a user attaching a static image via the paperclip icon menu, displaying options for Insert Variable Attachment and Insert Static Attachment — Adding static attachments to Prompts using the paperclip icon

This feature is particularly useful when you have standard reference documents, product images, or other materials that need to be consistently included across all executions of a particular Prompt.

Stack Trace for Workflow Execution Errors

September 8th, 2025

You can now see stack traces for any errors that show up when you execute your Deployed Workflow. This is particularly useful when you want more context as to why a particular Execution failed by giving you the error message and the Stack Trace of the error that was surfaced. Stack Trace for Workflow Execution Errors

Create Custom Nodes from the UI

September 8th, 2025

You can now create Custom Nodes by drag-and-dropping them from the Node side panel.

Custom Nodes in Side Panel

Custom Nodes allow you to define any custom behavior by specifying:

Input attributes
Outputs to return
And the underlying code to execute

Previously, you could only create new Custom Nodes by pushing up the code representation of a Workflow that contained one via the vellum workflows push CLI command. Now, you can define the Custom Node and edit its underlying code straight from the UI. To do this, click the Code Preview button, toggle on edit mode, and edit the definition of for your Custom Node.

Positioning Nodes In Front / Behind One Another

September 7th, 2025

You can now right-click on any Node in your Workflows to position it in front of or behind other Nodes. This feature is particularly useful when working with Note Nodes, allowing you to place them behind other Nodes to help document and organize different parts of your Workflow.

Bring Node to Front and Back

This layering system makes it easier to create visually organized Workflows where documentation and workflow logic can be cleanly separated, improving both readability and collaboration.

Updated Data Retention Policy for New Organizations

September 4th, 2025

New Organizations now default to a 30-day retention period for monitoring data, helping optimize storage costs and performance while maintaining essential operational insights. This change provides a balanced approach to data management without impacting functionality.

Existing Organizations maintain their current data retention settings, and Organizations on paid plans can still customize their retention periods to meet specific business requirements. If you need longer data retention for your use case, please reach out to our support team who can help configure the appropriate settings for your needs.

Syntax Highlighting in Prompt Jinja Blocks

September 1st, 2025

Prompt Jinja Blocks now include line numbers and syntax highlighting, making it significantly easier to write and validate Jinja code.

Jinja Syntax Highlighting

Previously, Jinja blocks appeared as plain text without visual feedback, making it difficult to spot syntax errors or understand code structure.