From 12c6bfb3139e37901ed5a545b45f6172e21a30b2 Mon Sep 17 00:00:00 2001
From: Matt DeKok <matt@dekok.dev>
Date: Wed, 15 Oct 2025 13:52:09 -0500
Subject: [PATCH 1/3] fix: `RecursiveFormFields` type for recursive or unknown
 schemas

---
 .changeset/upset-hotels-mix.md       |  5 +++++
 packages/kit/src/exports/public.d.ts | 22 +++++++++++++++++-----
 packages/kit/types/index.d.ts        | 22 +++++++++++++++++-----
 3 files changed, 39 insertions(+), 10 deletions(-)
 create mode 100644 .changeset/upset-hotels-mix.md

diff --git a/.changeset/upset-hotels-mix.md b/.changeset/upset-hotels-mix.md
new file mode 100644
index 000000000000..45b003eadee2
--- /dev/null
+++ b/.changeset/upset-hotels-mix.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: `RecursiveFormFields` type for recursive or unknown schemas
diff --git a/packages/kit/src/exports/public.d.ts b/packages/kit/src/exports/public.d.ts
index 01e4f8cf9eb9..18ed911e8302 100644
--- a/packages/kit/src/exports/public.d.ts
+++ b/packages/kit/src/exports/public.d.ts
@@ -1917,19 +1917,31 @@ type RemoteFormFieldContainer<Value> = RemoteFormFieldMethods<Value> & {
 /**
  * Recursive type to build form fields structure with proxy access
  */
-type RemoteFormFields<T> =
+export type RemoteFormFields<T, Leaf extends boolean = false> =
 	WillRecurseIndefinitely<T> extends true
-		? RecursiveFormFields
+		? RecursiveFormFields<Leaf>
 		: NonNullable<T> extends string | number | boolean | File
 			? RemoteFormField<NonNullable<T>>
 			: T extends string[] | File[]
 				? RemoteFormField<T> & { [K in number]: RemoteFormField<T[number]> }
 				: T extends Array<infer U>
-					? RemoteFormFieldContainer<T> & { [K in number]: RemoteFormFields<U> }
-					: RemoteFormFieldContainer<T> & { [K in keyof T]-?: RemoteFormFields<T[K]> };
+					? RemoteFormFieldContainer<T> & {
+							[K in number]: RemoteFormFields<
+								U,
+								U extends RemoteFormFieldValue | unknown ? true : false
+							>;
+						}
+					: RemoteFormFieldContainer<T> & {
+							[K in keyof T]-?: RemoteFormFields<
+								T[K],
+								T[K] extends RemoteFormFieldValue | unknown ? true : false
+							>;
+						};
 
 // By breaking this out into its own type, we avoid the TS recursion depth limit
-type RecursiveFormFields = RemoteFormField<any> & { [key: string | number]: RecursiveFormFields };
+type RecursiveFormFields<Leaf extends boolean = false> = (Leaf extends true
+	? RemoteFormField<any>
+	: RemoteFormFieldContainer<any>) & { [key: string | number]: RecursiveFormFields<true> };
 
 type MaybeArray<T> = T | T[];
 
diff --git a/packages/kit/types/index.d.ts b/packages/kit/types/index.d.ts
index b503853794e8..e04c0dd4d082 100644
--- a/packages/kit/types/index.d.ts
+++ b/packages/kit/types/index.d.ts
@@ -1893,19 +1893,31 @@ declare module '@sveltejs/kit' {
 	/**
 	 * Recursive type to build form fields structure with proxy access
 	 */
-	type RemoteFormFields<T> =
+	export type RemoteFormFields<T, Leaf extends boolean = false> =
 		WillRecurseIndefinitely<T> extends true
-			? RecursiveFormFields
+			? RecursiveFormFields<Leaf>
 			: NonNullable<T> extends string | number | boolean | File
 				? RemoteFormField<NonNullable<T>>
 				: T extends string[] | File[]
 					? RemoteFormField<T> & { [K in number]: RemoteFormField<T[number]> }
 					: T extends Array<infer U>
-						? RemoteFormFieldContainer<T> & { [K in number]: RemoteFormFields<U> }
-						: RemoteFormFieldContainer<T> & { [K in keyof T]-?: RemoteFormFields<T[K]> };
+						? RemoteFormFieldContainer<T> & {
+								[K in number]: RemoteFormFields<
+									U,
+									U extends RemoteFormFieldValue | unknown ? true : false
+								>;
+							}
+						: RemoteFormFieldContainer<T> & {
+								[K in keyof T]-?: RemoteFormFields<
+									T[K],
+									T[K] extends RemoteFormFieldValue | unknown ? true : false
+								>;
+							};
 
 	// By breaking this out into its own type, we avoid the TS recursion depth limit
-	type RecursiveFormFields = RemoteFormField<any> & { [key: string | number]: RecursiveFormFields };
+	type RecursiveFormFields<Leaf extends boolean = false> = (Leaf extends true
+		? RemoteFormField<any>
+		: RemoteFormFieldContainer<any>) & { [key: string | number]: RecursiveFormFields<true> };
 
 	type MaybeArray<T> = T | T[];
 

From b15abcbb0825a17c37ae0a4e6d489ef7a748de43 Mon Sep 17 00:00:00 2001
From: Matt DeKok <matt@dekok.dev>
Date: Sun, 19 Oct 2025 17:28:24 -0500
Subject: [PATCH 2/3] fix: better recursive unknown fields

---
 packages/kit/src/exports/public.d.ts | 39 ++++++++++++++++++----------
 packages/kit/types/index.d.ts        | 39 ++++++++++++++++++----------
 2 files changed, 52 insertions(+), 26 deletions(-)

diff --git a/packages/kit/src/exports/public.d.ts b/packages/kit/src/exports/public.d.ts
index 18ed911e8302..7f9a6f05ba00 100644
--- a/packages/kit/src/exports/public.d.ts
+++ b/packages/kit/src/exports/public.d.ts
@@ -1914,34 +1914,47 @@ type RemoteFormFieldContainer<Value> = RemoteFormFieldMethods<Value> & {
 	allIssues(): RemoteFormIssue[] | undefined;
 };
 
+type UnknownField<Value> = RemoteFormFieldMethods<Value> & {
+	/** Validation issues belonging to this or any of the fields that belong to it, if any */
+	allIssues(): RemoteFormIssue[] | undefined;
+} & {
+	/**
+	 * Returns an object that can be spread onto an input element with the correct type attribute,
+	 * aria-invalid attribute if the field is invalid, and appropriate value/checked property getters/setters.
+	 * @example
+	 * ```svelte
+	 * <input {...myForm.fields.myString.as('text')} />
+	 * <input {...myForm.fields.myNumber.as('number')} />
+	 * <input {...myForm.fields.myBoolean.as('checkbox')} />
+	 * ```
+	 */
+	as<T extends RemoteFormFieldType<Value>>(...args: AsArgs<T, Value>): InputElementProps<T>;
+} & {
+	[key: string | number]: UnknownField<any>;
+};
+
 /**
  * Recursive type to build form fields structure with proxy access
  */
-export type RemoteFormFields<T, Leaf extends boolean = false> =
+export type RemoteFormFields<T> =
 	WillRecurseIndefinitely<T> extends true
-		? RecursiveFormFields<Leaf>
+		? RecursiveFormFields
 		: NonNullable<T> extends string | number | boolean | File
 			? RemoteFormField<NonNullable<T>>
 			: T extends string[] | File[]
 				? RemoteFormField<T> & { [K in number]: RemoteFormField<T[number]> }
 				: T extends Array<infer U>
 					? RemoteFormFieldContainer<T> & {
-							[K in number]: RemoteFormFields<
-								U,
-								U extends RemoteFormFieldValue | unknown ? true : false
-							>;
+							[K in number]: RemoteFormFields<U>;
 						}
 					: RemoteFormFieldContainer<T> & {
-							[K in keyof T]-?: RemoteFormFields<
-								T[K],
-								T[K] extends RemoteFormFieldValue | unknown ? true : false
-							>;
+							[K in keyof T]-?: RemoteFormFields<T[K]>;
 						};
 
 // By breaking this out into its own type, we avoid the TS recursion depth limit
-type RecursiveFormFields<Leaf extends boolean = false> = (Leaf extends true
-	? RemoteFormField<any>
-	: RemoteFormFieldContainer<any>) & { [key: string | number]: RecursiveFormFields<true> };
+type RecursiveFormFields = RemoteFormFieldContainer<any> & {
+	[key: string | number]: UnknownField<any>;
+};
 
 type MaybeArray<T> = T | T[];
 
diff --git a/packages/kit/types/index.d.ts b/packages/kit/types/index.d.ts
index 1e4b415b0ab0..b99394c4efc5 100644
--- a/packages/kit/types/index.d.ts
+++ b/packages/kit/types/index.d.ts
@@ -1890,34 +1890,47 @@ declare module '@sveltejs/kit' {
 		allIssues(): RemoteFormIssue[] | undefined;
 	};
 
+	type UnknownField<Value> = RemoteFormFieldMethods<Value> & {
+		/** Validation issues belonging to this or any of the fields that belong to it, if any */
+		allIssues(): RemoteFormIssue[] | undefined;
+	} & {
+		/**
+		 * Returns an object that can be spread onto an input element with the correct type attribute,
+		 * aria-invalid attribute if the field is invalid, and appropriate value/checked property getters/setters.
+		 * @example
+		 * ```svelte
+		 * <input {...myForm.fields.myString.as('text')} />
+		 * <input {...myForm.fields.myNumber.as('number')} />
+		 * <input {...myForm.fields.myBoolean.as('checkbox')} />
+		 * ```
+		 */
+		as<T extends RemoteFormFieldType<Value>>(...args: AsArgs<T, Value>): InputElementProps<T>;
+	} & {
+		[key: string | number]: UnknownField<any>;
+	};
+
 	/**
 	 * Recursive type to build form fields structure with proxy access
 	 */
-	export type RemoteFormFields<T, Leaf extends boolean = false> =
+	export type RemoteFormFields<T> =
 		WillRecurseIndefinitely<T> extends true
-			? RecursiveFormFields<Leaf>
+			? RecursiveFormFields
 			: NonNullable<T> extends string | number | boolean | File
 				? RemoteFormField<NonNullable<T>>
 				: T extends string[] | File[]
 					? RemoteFormField<T> & { [K in number]: RemoteFormField<T[number]> }
 					: T extends Array<infer U>
 						? RemoteFormFieldContainer<T> & {
-								[K in number]: RemoteFormFields<
-									U,
-									U extends RemoteFormFieldValue | unknown ? true : false
-								>;
+								[K in number]: RemoteFormFields<U>;
 							}
 						: RemoteFormFieldContainer<T> & {
-								[K in keyof T]-?: RemoteFormFields<
-									T[K],
-									T[K] extends RemoteFormFieldValue | unknown ? true : false
-								>;
+								[K in keyof T]-?: RemoteFormFields<T[K]>;
 							};
 
 	// By breaking this out into its own type, we avoid the TS recursion depth limit
-	type RecursiveFormFields<Leaf extends boolean = false> = (Leaf extends true
-		? RemoteFormField<any>
-		: RemoteFormFieldContainer<any>) & { [key: string | number]: RecursiveFormFields<true> };
+	type RecursiveFormFields = RemoteFormFieldContainer<any> & {
+		[key: string | number]: UnknownField<any>;
+	};
 
 	type MaybeArray<T> = T | T[];
 

From c3be7cc15c56cecd70c8e7253883d3797e289d8f Mon Sep 17 00:00:00 2001
From: Matt DeKok <matt@dekok.dev>
Date: Sun, 19 Oct 2025 19:47:04 -0500
Subject: [PATCH 3/3] simplify type

---
 packages/kit/src/exports/public.d.ts | 1 -
 packages/kit/types/index.d.ts        | 1 -
 2 files changed, 2 deletions(-)

diff --git a/packages/kit/src/exports/public.d.ts b/packages/kit/src/exports/public.d.ts
index 77ea2507c15d..cb42dc6cc1c0 100644
--- a/packages/kit/src/exports/public.d.ts
+++ b/packages/kit/src/exports/public.d.ts
@@ -1917,7 +1917,6 @@ type RemoteFormFieldContainer<Value> = RemoteFormFieldMethods<Value> & {
 type UnknownField<Value> = RemoteFormFieldMethods<Value> & {
 	/** Validation issues belonging to this or any of the fields that belong to it, if any */
 	allIssues(): RemoteFormIssue[] | undefined;
-} & {
 	/**
 	 * Returns an object that can be spread onto an input element with the correct type attribute,
 	 * aria-invalid attribute if the field is invalid, and appropriate value/checked property getters/setters.
diff --git a/packages/kit/types/index.d.ts b/packages/kit/types/index.d.ts
index ba5b858dcbe2..52fcb547490d 100644
--- a/packages/kit/types/index.d.ts
+++ b/packages/kit/types/index.d.ts
@@ -1893,7 +1893,6 @@ declare module '@sveltejs/kit' {
 	type UnknownField<Value> = RemoteFormFieldMethods<Value> & {
 		/** Validation issues belonging to this or any of the fields that belong to it, if any */
 		allIssues(): RemoteFormIssue[] | undefined;
-	} & {
 		/**
 		 * Returns an object that can be spread onto an input element with the correct type attribute,
 		 * aria-invalid attribute if the field is invalid, and appropriate value/checked property getters/setters.