diff --git a/pyproject.toml b/pyproject.toml
index 852cd32a9..75c1304e6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "mcp"
-version = "0.8.0"
+version = "0.9.0.dev0"
 description = "Model Context Protocol implementation for Python"
 readme = "README.md"
 requires-python = ">=3.10"
diff --git a/uv.lock b/uv.lock
index 775750522..1a3facfeb 100644
--- a/uv.lock
+++ b/uv.lock
@@ -171,7 +171,7 @@ wheels = [
 
 [[package]]
 name = "mcp"
-version = "0.8.0.dev0"
+version = "0.9.0.dev0"
 source = { editable = "." }
 dependencies = [
     { name = "anyio" },