The Claude Code side agent is a new optional feature in Claude Code 2.1.287. Called "You should know," it runs alongside a coding session and watches Claude's output for important information that the developer or main agent might miss. Anthropic added it as a built-in mod alongside Claude Mods, a system that lets plugins modify deeper behavior.
The feature is different from simply adding another command to Claude Code. Anthropic describes "You should know" as a side agent that watches the session and flags things worth knowing. It is disabled by default and can be enabled with /plugin enable cc-plugin-you-should-know@builtin in supported first-party sessions with telemetry enabled. The official Claude Code release notes document the change.
Claude Code Gets a Second Layer of Attention
The practical idea is to let the main Claude session stay focused on the coding task while a separate agent watches its output for information that could be easy to overlook. That adds another layer of observation to a workflow that is increasingly moving beyond one prompt and one response.
Saganote has previously covered how Claude Code Auto Mode became the default for some paid plans and how Claude Code sessions can message each other. The new side agent adds another layer to that increasingly multi-agent workflow.
Claude Mods Go Deeper Than Traditional Plugins
Claude Code 2.1.287 also introduces Claude Mods, which Anthropic describes as plugins that can modify deeper behavior. Anthropic's public source shows that a mod is a Claude Code plugin whose behavior lives in a hooks module, allowing it to interact with engine events.
That puts "You should know" in a larger category than a simple productivity shortcut. Developers are getting a mechanism for adding behavior around the main coding agent, similar to how AI agents can be given tools and actions. Claude Code has also expanded beyond a single terminal workflow, including support for building and testing iOS apps in the simulator.
How to Enable You Should Know
The feature is opt-in rather than automatically active. On a supported first-party Claude Code session with telemetry enabled, users can run /plugin enable cc-plugin-you-should-know@builtin. Anthropic's release notes do not describe every type of information the side agent will flag, so its exact behavior should be understood from what the feature surfaces during actual sessions.
For developers already using Claude Code for longer or more autonomous tasks, the change adds another observer to the workflow without requiring a separate coding session.
