Files over tools: how we built the Knock Agent with a virtual filesystem and bash

Files over tools: how we built our agent with a virtual filesystem and bash

We built the Knock Agent to manage customer messaging by replacing complex API tools with a virtual filesystem and bash. Instead of exposing every API endpoint, we give the agent a file-based view of your account, allowing it to explore context and script changes efficiently. By porting just-bash to Elixir, we created a lightweight, secure environment that mirrors how developers work locally, enabling the agent to edit workflows and templates directly before persisting changes back to Knock.

"We believe a full sandbox is—at this stage—overkill for our simple needs."