diff --git a/README.md b/README.md
index 6cac162..26a3d8a 100644
--- a/README.md
+++ b/README.md
@@ -100,6 +100,17 @@ A [barrel](https://basarat.gitbook.io/typescript/main-1/barrel) is a way to roll
 npm install ctix --save-dev
 ```
 
+> **TypeScript version requirement**
+>
+> ctix 2.8.0 requires **TypeScript >=5.0.0 and <6.0.0**.
+>
+> TypeScript 6.x shifts to ESM-first defaults and introduces breaking changes to `moduleResolution` and `baseUrl` that are not yet supported by ctix. Until ctix adds ESM support, please keep your TypeScript version in the 5.x range.
+>
+> ```bash
+> # install a compatible TypeScript version explicitly
+> npm install typescript@">=5 <6" --save-dev
+> ```
+
 ## Usage
 
 ```bash