> For the complete documentation index, see [llms.txt](https://docs.heisenware.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.heisenware.com/app-builder/build-backend/extension-nodes.md). # Extension nodes Extension nodes process data directly within a flow without requiring a full function node. They attach to a function output or to another extension node to act on the data passing through. This lets you build processing pipelines by chaining nodes together, such as connecting a filter to a modifier, or a modifier to another modifier. Except for recorders, extension nodes operate as their own output. You can wire them to function inputs, triggers, or widgets exactly like a standard function output. To branch a single data source into multiple concurrent paths, attach multiple extension nodes to the same output in parallel. ## Types

Type	What it does
Modifier	Transforms the structure or value of the data, using JSONata or a JavaScript expression.
Filter	Acts as a conditional gate: halts the flow or branches it based on a JavaScript condition.
Recorder	Stores the output as timeseries data in the internal InfluxDB database.
Error handler	Opens a separate output that activates only when the parent function fails, enabling dedicated error logic. You can only attach an error handler directly to a function, not to other extension nodes.

## Working with extension nodes * **Add**: Click the + icon on a function's output or on an existing extension node and select the desired type. You can add multiple parallel extension nodes to the same output. * **Chain**: Add an extension node to the output of another extension node to create a multi-step pipeline (e.g., filter data, then modify it). * **Test**: Extension nodes show their last result directly below them. Click the icon of a modifier or filter to evaluate it manually during development. * **Delete**: Right-click an extension node and select Delete. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.heisenware.com/app-builder/build-backend/extension-nodes.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.