diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
index bdbf15d..b86c05f 100644
--- a/.github/copilot-instructions.md
+++ b/.github/copilot-instructions.md
@@ -53,6 +53,14 @@ You are operating in a multi-repo, documentation-first architecture. You MUST ST
 > For core framework rules see: `.github/copilot-instructions.md` (in AyCode.Core repo)
 > External repos in `own-dep-repos` are fully accessible — read their source code, docs, and `.github/copilot-instructions.md` freely when you need type definitions, base classes, or context. Do not limit yourself to the current workspace.
 
+## Shared Agent Skills
+
+Skills defined in other repos that can be referenced from here:
+
+- **protocol-audit** — Cross-repo consistency audit for `.github/copilot-instructions.md` across all 5 repos.
+  Location: `AyCode.Core/.github/skills/protocol-audit/SKILL.md`
+  Activate from an AyCode.Core session, or read the SKILL.md directly and follow its steps.
+
 ## nopCommerce Compatibility
 1. All three libraries target **net9.0** — required by nopCommerce 4.80.9. Do NOT change TFM.
 2. **NopDependencies** folder in `Mango.Nop.Core` contains **mirror copies** of nopCommerce entity classes (`BaseEntity`, `Customer`, `Order`, `Product`, `GenericAttribute`, etc.) so that `Mango.Nop.Core` can be referenced without the full nopCommerce dependency chain.