diff --git a/NuGet.config b/NuGet.config
new file mode 100644
index 000000000..c601d09b5
--- /dev/null
+++ b/NuGet.config
@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Project-level NuGet configuration.
+
+  The yavsc solution depends on HigginsSoft.IdentityServer8.* 8.1.0-alpha.*,
+  published only on the internal feed https://isn.pschneider.fr. The public
+  nuget.org feed has 8.0.4 as the nearest version, which causes NU1102 on
+  restore for every project that depends on it (Yavsc.Org, Yavsc.Api,
+  Yavsc.Blogs, Yavsc.Server, cli, tests).
+
+  Listing 'isn' before 'nuget.org' here ensures that restore finds the
+  alpha packages first, then falls back to nuget.org for everything else.
+  Both feeds are reachable anonymously; no credentials are stored here.
+
+  See AGENTS.md for the rationale.
+-->
+<configuration>
+  <packageSources>
+    <clear />
+    <add key="isn" value="https://isn.pschneider.fr/api/v3/index.json" />
+    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+  </packageSources>
+</configuration>