diff --git a/packages/extension-form/src/internal/Form.ts b/packages/extension-form/src/internal/Form.ts
index f5ad19d..1b8bed4 100644
--- a/packages/extension-form/src/internal/Form.ts
+++ b/packages/extension-form/src/internal/Form.ts
@@ -1,4 +1,5 @@
 import { Schema } from "effect"
+import type * as FormField from "./FormField.js"
 
 
 export interface Form<A, I, R> {
@@ -7,31 +8,12 @@ export interface Form<A, I, R> {
 
 
 export type FormTree<S extends Schema.Schema<any>> = (
-    S extends Schema.Array$<any> ? ArrayFormField<S> :
-    S extends Schema.Struct<any> ? StructFormField<S> :
-    GenericFormField<S>
+    S extends Schema.Array$<any> ? FormField.ArrayFormField<S> :
+    S extends Schema.Struct<any> ? FormField.StructFormField<S> :
+    FormField.GenericFormField<S>
 )
 
 
-export interface GenericFormField<S extends Schema.Schema<any>> {
-    readonly _tag: "GenericFormField"
-    readonly schema: S
-    readonly value: S["Type"]
-}
-
-export interface ArrayFormField<S extends Schema.Array$<any>> {
-    readonly _tag: "ArrayFormField"
-    readonly schema: S
-    readonly elements: readonly FormTree<S["value"]>[]
-}
-
-export interface StructFormField<S extends Schema.Struct<any>> {
-    readonly _tag: "StructFormField"
-    readonly schema: S
-    readonly fields: { [K in keyof S["fields"]]: FormTree<S["fields"][K]> }
-}
-
-
 const MySchema = Schema.Struct({
     name: Schema.String,
     symbol: Schema.SymbolFromSelf,
diff --git a/packages/extension-form/src/internal/FormField.ts b/packages/extension-form/src/internal/FormField.ts
new file mode 100644
index 0000000..a07df9d
--- /dev/null
+++ b/packages/extension-form/src/internal/FormField.ts
@@ -0,0 +1,25 @@
+import type { Schema } from "effect"
+import type * as Form from "./Form.ts"
+
+
+export interface FormField<S extends Schema.Schema.Any> {
+
+}
+
+export interface GenericFormField<S extends Schema.Schema.Any> extends FormField<S> {
+    readonly _tag: "GenericFormField"
+    readonly schema: S
+    readonly value: S["Type"]
+}
+
+export interface ArrayFormField<S extends Schema.Array$<Schema.Schema.Any>> extends FormField<S> {
+    readonly _tag: "ArrayFormField"
+    readonly schema: S
+    readonly elements: readonly Form.FormTree<S["value"]>[]
+}
+
+export interface StructFormField<S extends Schema.Struct<Schema.Struct.Fields>> extends FormField<S> {
+    readonly _tag: "StructFormField"
+    readonly schema: S
+    readonly fields: { [K in keyof S["fields"]]: Form.FormTree<S["fields"][K]> }
+}