diff --git a/rfcs/v4-issue-formats/formats.ts b/rfcs/v4-issue-formats/formats.ts
new file mode 100644
index 000000000..a74c978c9
--- /dev/null
+++ b/rfcs/v4-issue-formats/formats.ts
@@ -0,0 +1,254 @@
+type ZodParsedType = string;
+type Primitive = string | number | boolean | bigint | symbol | undefined | null;
+class ZodError {}
+
+export enum ZodIssueKind {
+  invalid_type = "invalid_type",
+  custom = "custom",
+  invalid_union = "invalid_union",
+  invalid_date = "invalid_date",
+  invalid_string = "invalid_string",
+  invalid_array = "invalid_array",
+  invalid_number = "invalid_number",
+  invalid_set = "invalid_set",
+  invalid_object = "invalid_object",
+  invalid_bigint = "invalid_bigint",
+  invalid_file = "invalid_file",
+}
+
+export enum ZodIssueCode {
+  invalid_type = "invalid_type",
+  invalid_literal = "invalid_literal",
+  custom = "custom",
+  invalid_union = "invalid_union",
+  invalid_union_discriminator = "invalid_union_discriminator",
+  invalid_enum_value = "invalid_enum_value",
+  unrecognized_keys = "unrecognized_keys",
+  invalid_arguments = "invalid_arguments",
+  invalid_return_type = "invalid_return_type",
+  invalid_date = "invalid_date",
+  invalid_string = "invalid_string",
+  too_small = "too_small",
+  too_big = "too_big",
+  invalid_intersection_types = "invalid_intersection_types",
+  not_multiple_of = "not_multiple_of",
+  not_finite = "not_finite",
+}
+
+// type ZodIssueCode = keyof typeof ZodIssueCode;
+
+export type ZodIssueBase = {
+  path: (string | number)[];
+  message?: string;
+  input?: unknown;
+  code: ZodIssueCode[keyof ZodIssueCode];
+  level: "warn" | "error" | "abort";
+};
+
+export type ZodInvalidTypeIssue = ZodIssueBase & {
+  kind: ZodIssueKind.invalid_type;
+  code: ZodIssueCode.invalid_type;
+  expected: ZodParsedType;
+  received: ZodParsedType;
+};
+
+export type ZodInvalidUnionIssue = ZodIssueBase & {
+  kind: ZodIssueKind.invalid_union;
+  code: ZodIssueCode.invalid_union;
+  unionErrors: ZodError[];
+};
+
+// type TooBig = { code: "too_big"; maximum: number };
+// type TooBigInclusive = { code: "too_big"; maximum: number; inclusive: boolean };
+// type TooSmall = { code: "too_small"; minimum: number };
+// type TooSmallInclusive = {
+//   code: "too_small";
+//   minimum: number;
+//   inclusive: boolean;
+// };
+
+export type ZodInvalidDateIssue = ZodIssueBase & {
+  kind: ZodIssueCode.invalid_date;
+} & (
+    | { code: "too_big"; maximum: number; inclusive: boolean }
+    | {
+        code: "too_small";
+        minimum: number;
+        inclusive: boolean;
+      }
+  );
+
+// there will be some additions here
+export type StringValidation =
+  | "email"
+  | "url"
+  | "emoji"
+  | "uuid"
+  | "nanoid"
+  | "regex"
+  | "cuid"
+  | "cuid2"
+  | "ulid"
+  | "datetime"
+  | "date"
+  | "time"
+  | "duration"
+  | "ip"
+  | "base64";
+
+export type ZodInvalidStringIssue = ZodIssueBase &
+  (
+    | {
+        code: "too_small";
+        subcode: "number_too_small";
+        minimum?: number;
+      }
+    | {
+        kind: ZodIssueCode.invalid_string;
+        code: "too_big";
+        subcode: "number_too_big";
+        maximum?: number;
+      }
+    | {
+        kind: ZodIssueCode.invalid_string;
+        code: "invalid_format";
+        format: StringValidation;
+        pattern?: string;
+      }
+    | {
+        kind: ZodIssueCode.invalid_string;
+        code: "invalid_format";
+        format: "starts_with";
+        value: string;
+      }
+    | {
+        kind: ZodIssueCode.invalid_string;
+        code: "invalid_format";
+        format: "ends_with";
+        value: string;
+      }
+    | {
+        kind: ZodIssueCode.invalid_string;
+        code: "invalid_format";
+        format: "includes";
+        value: string;
+      }
+  );
+
+export type ZodInvalidObjectIssue = ZodIssueBase &
+  (
+    | {
+        kind: ZodIssueCode.invalid_object;
+        code: "missing_keys";
+        keys?: string[];
+      }
+    | {
+        kind: ZodIssueCode.invalid_object;
+        code: "unrecognized_keys";
+        keys?: string[];
+      }
+  );
+
+export type ZodInvalidArrayIssue = ZodIssueBase &
+  (
+    | {
+        kind: ZodIssueCode.invalid_array;
+        code: "not_unique";
+      }
+    | {
+        kind: ZodIssueCode.invalid_array;
+        code: "too_big";
+        maximum?: number;
+      }
+    | {
+        kind: ZodIssueCode.invalid_array;
+        code: "too_small";
+        minimum?: number;
+      }
+  );
+
+export type ZodInvalidNumberIssue = ZodIssueBase &
+  (
+    | {
+        kind: ZodIssueCode.invalid_number;
+        code: "too_big";
+
+        maximum?: number;
+        exclusive?: boolean;
+      }
+    | {
+        kind: ZodIssueCode.invalid_number;
+        code: "too_small";
+        minimum?: number;
+        exclusive?: boolean;
+      }
+    | {
+        kind: ZodIssueCode.invalid_number;
+        code: "not_multiple_of";
+        multipleOf?: number;
+      }
+  );
+
+export type ZodInvalidSetIssue = ZodIssueBase &
+  (
+    | {
+        code: ZodIssueCode.invalid_set;
+        code: "too_big";
+        maximum?: number;
+      }
+    | {
+        code: ZodIssueCode.invalid_set;
+        code: "too_small";
+        minimum?: number;
+      }
+    | {
+        code: ZodIssueCode.invalid_set;
+        code: "not_unique";
+      }
+  );
+
+export interface ZodInvalidBigIntIssue extends ZodIssueBase {
+  kind: ZodIssueCode.invalid_bigint;
+  subcode: "too_big" | "too_small";
+  minimum?: number;
+  maximum?: number;
+  exclusive?: boolean;
+}
+
+export type ZodInvalidFileIssue = ZodIssueBase & {
+  type: ZodIssueCode.invalid_file;
+} & (
+    | {
+        code: "too_big";
+        maximum: number;
+      }
+    | {
+        code: "too_small";
+        minimum: number;
+      }
+    | {
+        code: "invalid_mime";
+        acceptedTypes: string[];
+      }
+    | {
+        code: "invalid_name";
+        expectedName?: string;
+      }
+  );
+
+export interface ZodCustomIssue extends ZodIssueBase {
+  code: ZodIssueCode.custom;
+  params?: { [k: string]: any };
+}
+
+export type ZodIssue =
+  | ZodInvalidTypeIssue
+  | ZodInvalidUnionIssue
+  | ZodInvalidStringIssue
+  | ZodInvalidArrayIssue
+  | ZodInvalidNumberIssue
+  | ZodInvalidSetIssue
+  | ZodInvalidObjectIssue
+  | ZodInvalidBigIntIssue
+  | ZodInvalidFileIssue
+  | ZodCustomIssue;
diff --git a/rfcs/v4-issue-formats/index.md b/rfcs/v4-issue-formats/index.md
new file mode 100644
index 000000000..e69de29bb
diff --git a/rfcs/v4-issue-formats/new_formats.ts b/rfcs/v4-issue-formats/new_formats.ts
new file mode 100644
index 000000000..b4b9932ea
--- /dev/null
+++ b/rfcs/v4-issue-formats/new_formats.ts
@@ -0,0 +1,224 @@
+type ZodParsedType = string;
+type Primitive = string | number | boolean | bigint | symbol | undefined | null;
+class ZodError {}
+type flatten<T> = { [k in keyof T]: T[k] } & {};
+
+export const ZodIssueCode = {
+  custom: "custom",
+  invalid_type: "invalid_type",
+  invalid_string: "invalid_string",
+  invalid_number: "invalid_number",
+  invalid_date: "invalid_date",
+  invalid_bigint: "invalid_bigint",
+  invalid_object: "invalid_object",
+  invalid_array: "invalid_array",
+  invalid_set: "invalid_set",
+  invalid_file: "invalid_file",
+} as const;
+export type ZodIssueCode = typeof ZodIssueCode;
+
+export type ZodIssueBase = {
+  path: (string | number)[];
+  message?: string;
+  input?: unknown;
+  code: string;
+  level: "warn" | "error" | "abort";
+};
+
+export type ZodInvalidTypeIssue = ZodIssueBase & {
+  code: "invalid_type";
+} & (
+    | {
+        check: ZodParsedType;
+        received: ZodParsedType;
+      }
+    | {
+        check: "union";
+        unionErrors: ZodError[];
+      }
+    | {
+        check: "literal";
+        literalValues: Primitive[];
+      }
+    | {
+        check: "enum";
+        enumValues: (string | number)[];
+      }
+  );
+
+export type $StringFormat =
+  | "email"
+  | "url"
+  | "emoji"
+  | "uuid"
+  | "nanoid"
+  | "regex"
+  | "cuid"
+  | "cuid2"
+  | "ulid"
+  | "datetime"
+  | "date"
+  | "time"
+  | "duration"
+  | "ip"
+  | "base64";
+
+export type ZodInvalidStringIssue = ZodIssueBase & {
+  code: "invalid_string";
+} & (
+    | {
+        check: $StringFormat;
+      }
+    | {
+        check: "starts_with";
+        value: string;
+      }
+    | {
+        check: "ends_with";
+        value: string;
+      }
+    | {
+        check: "includes";
+        value: string;
+      }
+    | {
+        check: "min_size";
+        minimum: number;
+      }
+    | {
+        check: "max_size";
+        maximum: number;
+      }
+    | {
+        check: "size";
+        size: number;
+      }
+    | {
+        check: "regex";
+        regex: string;
+      }
+  );
+
+export type ZodInvalidNumberIssue = ZodIssueBase & {
+  code: "invalid_number";
+} & (
+    | {
+        check: "maximum";
+        maximum: number;
+      }
+    | {
+        check: "minimum";
+        minimum: number;
+      }
+    | {
+        check: "not_multiple_of";
+        multipleOf: number;
+      }
+  );
+
+export type ZodInvalidDateIssue = ZodIssueBase & {
+  code: "invalid_date";
+} & (
+    | {
+        check: "maximum";
+        maximum: number;
+      }
+    | {
+        check: "minimum";
+        minimum: number;
+      }
+  );
+
+export type ZodInvalidBigIntIssue = ZodIssueBase & {
+  code: "invalid_bigint";
+} & (
+    | {
+        check: "maximum";
+        maximum: bigint;
+      }
+    | {
+        check: "minimum";
+        minimum: bigint;
+      }
+    | {
+        check: "not_multiple_of";
+        multipleOf: bigint;
+      }
+  );
+
+export type ZodInvalidObjectIssue = ZodIssueBase & {
+  code: "invalid_object";
+} & {
+  check: "unrecognized_keys";
+  keys: string[];
+};
+
+export type ZodInvalidArrayIssue = ZodIssueBase & {
+  code: "invalid_array";
+} & (
+    | {
+        check: "min_size";
+        minimum: number;
+      }
+    | {
+        check: "max_size";
+        maximum: number;
+      }
+    | {
+        check: "size";
+        size: number;
+      }
+  );
+
+export type ZodInvalidSetIssue = ZodIssueBase & {
+  code: "invalid_set";
+} & (
+    | {
+        check: "min_size";
+        minimum: number;
+      }
+    | {
+        check: "max_size";
+        maximum: number;
+      }
+    | {
+        check: "size";
+        size: number;
+      }
+  );
+
+export type ZodInvalidFileIssue = ZodIssueBase & {
+  code: "invalid_file";
+} & (
+    | {
+        check: "min_size";
+        minimum: number;
+      }
+    | {
+        check: "max_size";
+        maximum: number;
+      }
+  );
+
+export interface ZodCustomIssues {
+  custom: { params?: { [k: string]: any } };
+  // test: { name: "string" }
+}
+
+type _ZodCustomIssue<T extends keyof ZodCustomIssues = keyof ZodCustomIssues> =
+  T extends keyof ZodCustomIssues
+    ? flatten<{ check: T } & ZodCustomIssues[T]>
+    : never;
+type ZodCustomIssue = ZodIssueBase & { code: "custom" } & _ZodCustomIssue;
+
+export type ZodIssue =
+  | ZodInvalidTypeIssue
+  | ZodInvalidStringIssue
+  | ZodInvalidNumberIssue
+  | ZodInvalidBigIntIssue
+  | ZodInvalidDateIssue
+  | ZodInvalidArrayIssue
+  | ZodInvalidSetIssue
+  | ZodInvalidObjectIssue
+  | ZodInvalidFileIssue
+  | ZodCustomIssue;
diff --git a/rfcs/v4-issue-formats/old_formats.ts b/rfcs/v4-issue-formats/old_formats.ts
new file mode 100644
index 000000000..46cf69f14
--- /dev/null
+++ b/rfcs/v4-issue-formats/old_formats.ts
@@ -0,0 +1,152 @@
+type ZodParsedType = string;
+type Primitive = string | number | boolean | bigint | symbol | undefined | null;
+class ZodError {}
+
+export enum ZodIssueCode {
+  invalid_type = "invalid_type",
+  invalid_literal = "invalid_literal",
+  custom = "custom",
+  invalid_union = "invalid_union",
+  invalid_union_discriminator = "invalid_union_discriminator",
+  invalid_enum_value = "invalid_enum_value",
+  unrecognized_keys = "unrecognized_keys",
+  invalid_arguments = "invalid_arguments",
+  invalid_return_type = "invalid_return_type",
+  invalid_date = "invalid_date",
+  invalid_string = "invalid_string",
+  too_small = "too_small",
+  too_big = "too_big",
+  invalid_intersection_types = "invalid_intersection_types",
+  not_multiple_of = "not_multiple_of",
+  not_finite = "not_finite",
+}
+
+export type ZodIssueBase = {
+  path: (string | number)[];
+  message?: string;
+  fatal?: boolean;
+};
+
+export interface ZodInvalidTypeIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.invalid_type;
+  expected: ZodParsedType;
+  received: ZodParsedType;
+}
+
+export interface ZodInvalidLiteralIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.invalid_literal;
+  expected: unknown;
+  received: unknown;
+}
+
+export interface ZodUnrecognizedKeysIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.unrecognized_keys;
+  keys: string[];
+}
+
+export interface ZodInvalidUnionIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.invalid_union;
+  unionErrors: ZodError[];
+}
+
+export interface ZodInvalidUnionDiscriminatorIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.invalid_union_discriminator;
+  options: Primitive[];
+}
+
+export interface ZodInvalidEnumValueIssue extends ZodIssueBase {
+  received: string | number;
+  code: typeof ZodIssueCode.invalid_enum_value;
+  options: (string | number)[];
+}
+
+export interface ZodInvalidArgumentsIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.invalid_arguments;
+  argumentsError: ZodError;
+}
+
+export interface ZodInvalidReturnTypeIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.invalid_return_type;
+  returnTypeError: ZodError;
+}
+
+export interface ZodInvalidDateIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.invalid_date;
+}
+
+export type StringValidation =
+  | "email"
+  | "url"
+  | "emoji"
+  | "uuid"
+  | "nanoid"
+  | "regex"
+  | "cuid"
+  | "cuid2"
+  | "ulid"
+  | "datetime"
+  | "date"
+  | "time"
+  | "duration"
+  | "ip"
+  | "base64"
+  | { includes: string; position?: number }
+  | { startsWith: string }
+  | { endsWith: string };
+
+export interface ZodInvalidStringIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.invalid_string;
+  validation: StringValidation;
+}
+
+export interface ZodTooSmallIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.too_small;
+  minimum: number | bigint;
+  inclusive: boolean;
+  exact?: boolean;
+  type: "array" | "string" | "number" | "set" | "date" | "bigint";
+}
+
+export interface ZodTooBigIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.too_big;
+  maximum: number | bigint;
+  inclusive: boolean;
+  exact?: boolean;
+  type: "array" | "string" | "number" | "set" | "date" | "bigint";
+}
+
+export interface ZodInvalidIntersectionTypesIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.invalid_intersection_types;
+}
+
+export interface ZodNotMultipleOfIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.not_multiple_of;
+  multipleOf: number | bigint;
+}
+
+export interface ZodNotFiniteIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.not_finite;
+}
+
+export interface ZodCustomIssue extends ZodIssueBase {
+  code: typeof ZodIssueCode.custom;
+  params?: { [k: string]: any };
+}
+
+export type ZodIssue =
+  | ZodInvalidTypeIssue
+  | ZodInvalidLiteralIssue
+  | ZodUnrecognizedKeysIssue
+  | ZodInvalidUnionIssue
+  | ZodInvalidUnionDiscriminatorIssue
+  | ZodInvalidEnumValueIssue
+  | ZodInvalidArgumentsIssue
+  | ZodInvalidReturnTypeIssue
+  | ZodInvalidDateIssue
+  | ZodInvalidStringIssue
+  | ZodTooSmallIssue
+  | ZodTooBigIssue
+  | ZodInvalidIntersectionTypesIssue
+  | ZodNotMultipleOfIssue
+  | ZodNotFiniteIssue
+  | ZodCustomIssue;