diff --git a/PATCHES.md b/PATCHES.md
index b34a7f0..ba53678 100644
--- a/PATCHES.md
+++ b/PATCHES.md
@@ -1,5 +1,8 @@
 # Vendored `containerization` — Nucleic patches
 
+> Overview of *why* these patches exist (the session-isolation model) + the build/validate workflow:
+> [`docs/CONTAINER_ISOLATION.md`](../../docs/CONTAINER_ISOLATION.md). This file is the per-patch detail.
+
 This is a **vendored copy** of [apple/containerization](https://github.com/apple/containerization)
 at upstream commit `6b7b42ca3efeee8c706070e4355e6a807c5336ae`, referenced by the root `Package.swift`
 via `.package(path: "third_party/containerization")` instead of the github URL.