diff --git a/packages/reffuse/src/Reffuse.ts b/packages/reffuse/src/Reffuse.ts
index c91b6b9..1185e55 100644
--- a/packages/reffuse/src/Reffuse.ts
+++ b/packages/reffuse/src/Reffuse.ts
@@ -14,7 +14,7 @@ export class Reffuse<
     readonly Provider: ReffuseReactContext.Provider<RuntimeR, OwnContextR, ParentContextR>
 
     constructor(
-        runtime: Runtime.Runtime<RuntimeR>,
+        readonly runtime: Runtime.Runtime<RuntimeR>,
         parent?: Reffuse<RuntimeR, ParentContextR, unknown, unknown>,
     ) {
         this.Provider = parent
@@ -22,6 +22,15 @@ export class Reffuse<
             : ReffuseReactContext.makeRootProvider(runtime, this.Context)
     }
 
+    extend<OwnContextR = never>() {
+        return new Reffuse<
+            RuntimeR,
+            ContextR | OwnContextR,
+            OwnContextR,
+            ContextR
+        >(this.runtime, this)
+    }
+
 
     useRuntime(): Runtime.Runtime<RuntimeR> {
         return React.useContext(this.Context).runtime