diff --git a/docs/install-and-setup.md b/docs/install-and-setup.md
index 5dc079816..1baedb430 100644
--- a/docs/install-and-setup.md
+++ b/docs/install-and-setup.md
@@ -8,6 +8,8 @@
     - In AngularFire 21.0.0-rc.1 and earlier, `ng add` run by an agent with firebase-tools 15.26 or later stops after you choose features, with `Cannot read properties of undefined (reading 'email')`.
     - If it already stopped, run `ng add @angular/fire@next` again yourself. The stopped run leaves only an empty `firebase.json`, which the second run reuses.
   - A copy older than 14 stops setup with `firebase-tools version 14.0.0+ is required, please upgrade and run again`, and `ng add` does not upgrade a copy you already have.
+- **npm 11.6 or later**, if you use npm. Older versions, including the npm 10 that ships with Node.js 20 and 22, cannot install a new Angular 21 project ([npm/cli#9787](https://github.com/npm/cli/issues/9787), `Cannot read properties of null (reading 'edgesOut')`). Update with `npm install -g npm@11`.
+  - If it already failed, delete the project folder it left behind before running the command again.
 - **Harmless CLI noise.** The Firebase CLI may print a `punycode` deprecation warning or ask about enabling extra features (for example Gemini) during setup. These come from the CLI, not from AngularFire, and are safe to ignore.
 
 ### 1. Create a new project