A second agent, watching the first one
When Claude Code works through a long task — a multi-file refactor, a dependency bump, a migration — a lot happens between the prompt you typed and the summary it gives you at the end. Assumptions get made. Edge cases get silently skipped. A flag gets flipped that you'd want to know about. Most of that scrolls past in the output, and unless you read every line, you miss it.
You Should Know is a built-in Claude Code plugin, shipped in v2.1.287 (October 1, 2026), that addresses this directly. Instead of trying to make the main agent narrate everything, it spins up a separate side agent whose only job is to watch the main agent's work and flag things worth your attention. When it spots something, it drops a note in a banner above your prompt — not buried in the transcript, not something you have to scroll back for.
Enabling it
The plugin ships disabled by default. Turn it on with:
/plugin enable cc-plugin-you-should-know@builtin
It's also visible in the /plugin panel under Installed → Show disabled sections. Two requirements worth knowing before you flip it on: it only runs on first-party Claude sessions, and it requires telemetry to be enabled, since the side agent's observations are part of that data path. If either condition isn't met, the plugin stays dormant even if "enabled."
What it's good for
- Long autonomous runs where you step away and want a digest of notable decisions, not a full transcript re-read.
- Catching things phrased ambiguously — a v2.1.288 refinement changed how notes are worded ("we," "the main agent," or "you") depending on who actually made the relevant call, so you can tell your own choices apart from Claude's.
- Working alongside Mods (lesson 066) — this plugin is itself a Mod, built on the same event-handler system that lets plugins observe and annotate what Claude Code is doing in real time.
It's not a substitute for reviewing diffs or reading plans — it's a safety net for the stuff that's easy to miss when you're trusting Claude to handle the toil.