Fresh eyes review
Let a sub-agent review the code
Ask an AI agent to review the code it just wrote, and it will not find much. Show the same changes to a fresh session, and it will return with many more findings. Some valid, some minor, others just noise. Even the best models behave like this: the authoring session is biased by its own reasoning.
After all, people are no different: finding mistakes in your own text is hard, while a colleague often spots them more easily. This skill gives your agent that colleague: a sub-agent that starts with a clean context.
fresh-eyes-review
Run it from your main session and tell it what to review: it can be a branch, a commit, a git diff, a couple of files, even a document (for example a PLAN.md). Or just invoke it without arguments and it will figure out what to review on its own and ask you to confirm the prompt for the reviewing session. Approve it, or tweak it first, and the review will start in a clean context.
The reviewing session sees the changes and their goal, and is free to check the whole codebase. What it never sees is the reasoning of the authoring session (no plan, notes, chat history, etc.). This part matters: hand it the reasoning that produced a bug, and chances are that it will overlook the bug for the same reason the authoring session did.
Findings come back to the main session: each one points at a file and describes how it actually breaks. No minor style nitpicks, no vague concerns, and "nothing found" is a valid answer by design. The reviewing session can't always distinguish a bug from an intentional choice, so the judgment is left to the main authoring session, which knows more about the task and will help you judge each finding. Then you decide what needs to be addressed.
More than a code reviewer
Reviewing code is the classic case, but not the only one! You can easily point it at a document: type /fresh-eyes-review the PLAN.md against the REQUIREMENTS.md even before any code is written. The same works for a requirements doc against its original ticket, and so on.
Other skills also use /fresh-eyes-review as a building block: they pass in the changes, the goal and the review instructions themselves, and the review runs as one step of a bigger workflow (fresh context included). Any agent that can spawn sub-agents can do this.