diff --git a/Directory.Build.props b/Directory.Build.props
index 47423f0..1719887 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <VersionPrefix>0.1.0</VersionPrefix>
+    <VersionPrefix>2.0.0</VersionPrefix>
     <Authors>matengo</Authors>
     <Description>Embedded AOT-oriented vector database library for .NET.</Description>
     <PackageTags>vector-database;embeddings;hnsw;ann;aot;dotnet</PackageTags>
diff --git a/README.md b/README.md
index c96ef05..56f5803 100644
--- a/README.md
+++ b/README.md
@@ -98,6 +98,8 @@ Or for the typed client:
 dotnet add package Qvec.Core.Client
 ```
 
+> **Upgrading from 1.0.x:** 2.0 is a rewrite. The on-disk format (v5) is not readable by 1.0.x and 1.0.x files are rejected with `QvecFormatException`; there is no in-place migration. Export from the old database and re-insert into a new one.
+
 ### Initialize and Add Data
 
 ```csharp