diff --git a/packages/next-safe-action/src/__tests__/action-callbacks.test.ts b/packages/next-safe-action/src/__tests__/action-callbacks.test.ts
index 84fb3d6..69c1732 100644
--- a/packages/next-safe-action/src/__tests__/action-callbacks.test.ts
+++ b/packages/next-safe-action/src/__tests__/action-callbacks.test.ts
@@ -27,13 +27,13 @@ test("action with no input schema and no server errors calls `onSuccess` and `on
 			return;
 		},
 		{
-			onSuccess: () => {
+			onSuccess: async () => {
 				executed++;
 			},
-			onError: () => {
+			onError: async () => {
 				executed++; // should not be called
 			},
-			onSettled: () => {
+			onSettled: async () => {
 				executed++;
 			},
 		}
@@ -57,7 +57,15 @@ test("action with input schemas and no errors calls `onSuccess` and `onSettled`
 				};
 			},
 			{
-				onSuccess: ({ clientInput, bindArgsClientInputs, parsedInput, bindArgsParsedInputs, data, metadata, ctx }) => {
+				onSuccess: async ({
+					clientInput,
+					bindArgsClientInputs,
+					parsedInput,
+					bindArgsParsedInputs,
+					data,
+					metadata,
+					ctx,
+				}) => {
 					executed++;
 
 					assert.deepStrictEqual(
@@ -75,10 +83,10 @@ test("action with input schemas and no errors calls `onSuccess` and `onSettled`
 						}
 					);
 				},
-				onError: () => {
+				onError: async () => {
 					executed++; // should not be called
 				},
-				onSettled: ({ clientInput, bindArgsClientInputs, result, metadata, ctx }) => {
+				onSettled: async ({ clientInput, bindArgsClientInputs, result, metadata, ctx }) => {
 					executed++;
 
 					assert.deepStrictEqual(
@@ -115,10 +123,10 @@ test("action with input schemas and server error calls `onError` and `onSettled`
 				throw new Error("Server error");
 			},
 			{
-				onSuccess: () => {
+				onSuccess: async () => {
 					executed++; // should not be called
 				},
-				onError({ error, clientInput, bindArgsClientInputs, metadata, ctx }) {
+				onError: async ({ error, clientInput, bindArgsClientInputs, metadata, ctx }) => {
 					executed++;
 
 					assert.deepStrictEqual(
@@ -134,7 +142,7 @@ test("action with input schemas and server error calls `onError` and `onSettled`
 						}
 					);
 				},
-				onSettled({ clientInput, bindArgsClientInputs, result, metadata, ctx }) {
+				onSettled: async ({ clientInput, bindArgsClientInputs, result, metadata, ctx }) => {
 					executed++;
 
 					assert.deepStrictEqual(
@@ -171,10 +179,10 @@ test("action with validation errors calls `onError` and `onSettled` callbacks wi
 				};
 			},
 			{
-				onSuccess: () => {
+				onSuccess: async () => {
 					executed++; // should not be called
 				},
-				onError({ error, clientInput, bindArgsClientInputs, metadata, ctx }) {
+				onError: async ({ error, clientInput, bindArgsClientInputs, metadata, ctx }) => {
 					executed++;
 
 					assert.deepStrictEqual(
@@ -202,7 +210,7 @@ test("action with validation errors calls `onError` and `onSettled` callbacks wi
 						}
 					);
 				},
-				onSettled({ clientInput, bindArgsClientInputs, result, metadata, ctx }) {
+				onSettled: async ({ clientInput, bindArgsClientInputs, result, metadata, ctx }) => {
 					executed++;
 
 					assert.deepStrictEqual(
@@ -252,10 +260,10 @@ test("action with server validation error calls `onError` and `onSettled` callba
 			});
 		},
 		{
-			onSuccess: () => {
+			onSuccess: async () => {
 				executed++; // should not be called
 			},
-			onError({ error, clientInput, bindArgsClientInputs, metadata, ctx }) {
+			onError: async ({ error, clientInput, bindArgsClientInputs, metadata, ctx }) => {
 				executed++;
 
 				assert.deepStrictEqual(
@@ -275,7 +283,7 @@ test("action with server validation error calls `onError` and `onSettled` callba
 					}
 				);
 			},
-			onSettled({ clientInput, bindArgsClientInputs, result, metadata, ctx }) {
+			onSettled: async ({ clientInput, bindArgsClientInputs, result, metadata, ctx }) => {
 				executed++;
 
 				assert.deepStrictEqual(
diff --git a/packages/next-safe-action/src/__tests__/bind-args-validation-errors.test.ts b/packages/next-safe-action/src/__tests__/bind-args-validation-errors.test.ts
index 0fce638..45f18f5 100644
--- a/packages/next-safe-action/src/__tests__/bind-args-validation-errors.test.ts
+++ b/packages/next-safe-action/src/__tests__/bind-args-validation-errors.test.ts
@@ -56,7 +56,9 @@ test("action with invalid bind args input gives back an object with correct `bin
 	];
 
 	const action = dac
-		.bindArgsSchemas(bindArgsSchemas, { handleBindArgsValidationErrorsShape: flattenBindArgsValidationErrors })
+		.bindArgsSchemas(bindArgsSchemas, {
+			handleBindArgsValidationErrorsShape: async (ve) => flattenBindArgsValidationErrors(ve),
+		})
 		.action(async () => {
 			return {
 				ok: true,
@@ -138,7 +140,9 @@ test("action with invalid bind args input gives back an object with correct `bin
 	];
 
 	const action = foac
-		.bindArgsSchemas(bindArgsSchemas, { handleBindArgsValidationErrorsShape: flattenBindArgsValidationErrors })
+		.bindArgsSchemas(bindArgsSchemas, {
+			handleBindArgsValidationErrorsShape: async (ve) => flattenBindArgsValidationErrors(ve),
+		})
 		.action(async () => {
 			return {
 				ok: true,
@@ -225,7 +229,9 @@ test("action with invalid bind args input gives back an object with correct `bin
 	];
 
 	const action = flac
-		.bindArgsSchemas(bindArgsSchemas, { handleBindArgsValidationErrorsShape: formatBindArgsValidationErrors })
+		.bindArgsSchemas(bindArgsSchemas, {
+			handleBindArgsValidationErrorsShape: async (ve) => formatBindArgsValidationErrors(ve),
+		})
 		.action(async () => {
 			return {
 				ok: true,
diff --git a/packages/next-safe-action/src/__tests__/combined-validation-errors.test.ts b/packages/next-safe-action/src/__tests__/combined-validation-errors.test.ts
index 1b7f340..a890a3e 100644
--- a/packages/next-safe-action/src/__tests__/combined-validation-errors.test.ts
+++ b/packages/next-safe-action/src/__tests__/combined-validation-errors.test.ts
@@ -74,7 +74,9 @@ test("action with invalid bind args input and invalid main input gives back an o
 
 	const action = dac
 		.schema(schema)
-		.bindArgsSchemas(bindArgsSchemas, { handleBindArgsValidationErrorsShape: flattenBindArgsValidationErrors })
+		.bindArgsSchemas(bindArgsSchemas, {
+			handleBindArgsValidationErrorsShape: async (ve) => flattenBindArgsValidationErrors(ve),
+		})
 		.action(async () => {
 			return {
 				ok: true,
@@ -131,7 +133,7 @@ test("action with invalid bind args input and invalid main input gives back an o
 	];
 
 	const action = foac
-		.schema(schema, { handleValidationErrorsShape: flattenValidationErrors })
+		.schema(schema, { handleValidationErrorsShape: async (ve) => flattenValidationErrors(ve) })
 		.bindArgsSchemas(bindArgsSchemas)
 		.action(async () => {
 			return {
@@ -179,7 +181,9 @@ test("action with invalid bind args input and valid main input gives back an obj
 
 	const action = foac
 		.schema(schema)
-		.bindArgsSchemas(bindArgsSchemas, { handleBindArgsValidationErrorsShape: flattenBindArgsValidationErrors })
+		.bindArgsSchemas(bindArgsSchemas, {
+			handleBindArgsValidationErrorsShape: async (ve) => flattenBindArgsValidationErrors(ve),
+		})
 		.action(async () => {
 			return {
 				ok: true,
@@ -287,8 +291,10 @@ test("action with invalid bind args input, invalid main input and root level sch
 	];
 
 	const action = flac
-		.schema(schema, { handleValidationErrorsShape: formatValidationErrors })
-		.bindArgsSchemas(bindArgsSchemas, { handleBindArgsValidationErrorsShape: formatBindArgsValidationErrors })
+		.schema(schema, { handleValidationErrorsShape: async (ve) => formatValidationErrors(ve) })
+		.bindArgsSchemas(bindArgsSchemas, {
+			handleBindArgsValidationErrorsShape: async (ve) => formatBindArgsValidationErrors(ve),
+		})
 		.action(async () => {
 			return {
 				ok: true,
diff --git a/packages/next-safe-action/src/__tests__/middleware.test.ts b/packages/next-safe-action/src/__tests__/middleware.test.ts
index 896c196..cccc50f 100644
--- a/packages/next-safe-action/src/__tests__/middleware.test.ts
+++ b/packages/next-safe-action/src/__tests__/middleware.test.ts
@@ -357,10 +357,10 @@ test("overridden formatted validation errors in execution result from middleware
 				z.object({
 					username: z.string().max(3),
 				}),
-			{ handleValidationErrorsShape: formatValidationErrors }
+			{ handleValidationErrorsShape: async (ve) => formatValidationErrors(ve) }
 		)
 		.bindArgsSchemas([z.object({ age: z.number().positive() })], {
-			handleBindArgsValidationErrorsShape: formatBindArgsValidationErrors,
+			handleBindArgsValidationErrorsShape: async (ve) => formatBindArgsValidationErrors(ve),
 		})
 		.use(async ({ next }) => {
 			// Await action execution.
diff --git a/packages/next-safe-action/src/__tests__/validation-errors.test.ts b/packages/next-safe-action/src/__tests__/validation-errors.test.ts
index db13dce..188f24d 100644
--- a/packages/next-safe-action/src/__tests__/validation-errors.test.ts
+++ b/packages/next-safe-action/src/__tests__/validation-errors.test.ts
@@ -126,7 +126,7 @@ test("action with invalid input gives back an object with correct `validationErr
 
 	const action = dac
 		.schema(schema, {
-			handleValidationErrorsShape: flattenValidationErrors,
+			handleValidationErrorsShape: async (ve) => flattenValidationErrors(ve),
 		})
 		.action(async () => {
 			return {
@@ -318,7 +318,7 @@ test("action with invalid input gives back an object with correct `validationErr
 
 	const action = foac
 		.schema(schema, {
-			handleValidationErrorsShape: flattenValidationErrors,
+			handleValidationErrorsShape: async (ve) => flattenValidationErrors(ve),
 		})
 		.action(async () => {
 			return {
@@ -452,7 +452,7 @@ test("action with invalid input gives back an object with correct `validationErr
 
 	const action = flac
 		.schema(schema, {
-			handleValidationErrorsShape: formatValidationErrors,
+			handleValidationErrorsShape: async (ve) => formatValidationErrors(ve),
 		})
 		.action(async () => {
 			return {