diff --git a/.changeset/tiny-waves-help.md b/.changeset/tiny-waves-help.md
new file mode 100644
index 000000000..6efb9f0a7
--- /dev/null
+++ b/.changeset/tiny-waves-help.md
@@ -0,0 +1,5 @@
+---
+"openapi-fetch": patch
+---
+
+Use openapi-typescript-helpers package for types
diff --git a/package.json b/package.json
index 8172419c0..c8c51041a 100644
--- a/package.json
+++ b/package.json
@@ -13,9 +13,11 @@
     "build:openapi-fetch": "cd packages/openapi-fetch && pnpm run build",
     "lint": "run-p -s lint:*",
     "lint:openapi-typescript": "cd packages/openapi-typescript && pnpm run lint",
+    "lint:openapi-typescript-helpers": "cd packages/openapi-typescript-helpers && pnpm run lint",
     "lint:openapi-fetch": "cd packages/openapi-fetch && pnpm run lint",
     "test": "run-p -s test:*",
     "test:openapi-typescript": "cd packages/openapi-typescript && pnpm test",
+    "test:openapi-typescript-helpers": "cd packages/openapi-typescript-helpers && pnpm test",
     "test:openapi-fetch": "cd packages/openapi-fetch && pnpm test",
     "version": "pnpm run build && changeset version && pnpm i"
   },
diff --git a/packages/openapi-fetch/package.json b/packages/openapi-fetch/package.json
index 4bee87b52..ae44f0c6c 100644
--- a/packages/openapi-fetch/package.json
+++ b/packages/openapi-fetch/package.json
@@ -57,6 +57,9 @@
     "prepublish": "pnpm run prepare && pnpm run build",
     "version": "pnpm run prepare && pnpm run build"
   },
+  "dependencies": {
+    "openapi-typescript-helpers": "^0.0.1"
+  },
   "devDependencies": {
     "axios": "^1.4.0",
     "del-cli": "^5.0.0",
diff --git a/packages/openapi-fetch/src/index.ts b/packages/openapi-fetch/src/index.ts
index 263e435ca..4749f90b3 100644
--- a/packages/openapi-fetch/src/index.ts
+++ b/packages/openapi-fetch/src/index.ts
@@ -1,3 +1,5 @@
+import type { ErrorResponse, HttpMethod, SuccessResponse, FilterKeys, MediaType, PathsWithMethod, ResponseObjectMap, OperationRequestBodyContent } from "openapi-typescript-helpers";
+
 // settings & const
 const DEFAULT_HEADERS = {
   "Content-Type": "application/json",
@@ -19,55 +21,24 @@ interface ClientOptions extends RequestInit {
   /** global bodySerializer */
   bodySerializer?: BodySerializer<unknown>;
 }
-export interface BaseParams {
-  params?: { query?: Record<string, unknown> };
-}
-
-// const
-
-export type PathItemObject = { [M in HttpMethod]: OperationObject } & { parameters?: any };
+export type QuerySerializer<T> = (query: T extends { parameters: any } ? NonNullable<T["parameters"]["query"]> : Record<string, unknown>) => string;
+export type BodySerializer<T> = (body: OperationRequestBodyContent<T>) => any;
 export type ParseAs = "json" | "text" | "blob" | "arrayBuffer" | "stream";
-export interface OperationObject {
-  parameters: any;
-  requestBody: any; // note: "any" will get overridden in inference
-  responses: any;
+export interface DefaultParamsOption {
+  params?: { query?: Record<string, unknown> };
 }
-export type HttpMethod = "get" | "put" | "post" | "delete" | "options" | "head" | "patch" | "trace";
-export type OkStatus = 200 | 201 | 202 | 203 | 204 | 206 | 207 | "2XX";
-// prettier-ignore
-export type ErrorStatus = 500 | '5XX' | 400 | 401 | 402 | 403 | 404 | 405 | 406 | 407 | 408 | 409 | 410 | 411 | 412 | 413 | 414 | 415 | 416 | 417 | 418 | 420 | 421 | 422 | 423 | 424 | 425 | 426 | 429 | 431 | 444 | 450 | 451 | 497 | 498 | 499 | '4XX' | "default";
-
-// util
-/** Get a union of paths which have method */
-export type PathsWith<Paths extends Record<string, PathItemObject>, PathnameMethod extends HttpMethod> = {
-  [Pathname in keyof Paths]: Paths[Pathname] extends { [K in PathnameMethod]: any } ? Pathname : never;
-}[keyof Paths];
-/** Find first match of multiple keys */
-export type FilterKeys<Obj, Matchers> = { [K in keyof Obj]: K extends Matchers ? Obj[K] : never }[keyof Obj];
-export type MediaType = `${string}/${string}`;
-
-// general purpose types
-export type Params<T> = T extends { parameters: any } ? { params: NonNullable<T["parameters"]> } : BaseParams;
-export type RequestBodyObj<T> = T extends { requestBody?: any } ? T["requestBody"] : never;
-export type RequestBodyContent<T> = undefined extends RequestBodyObj<T> ? FilterKeys<NonNullable<RequestBodyObj<T>>, "content"> | undefined : FilterKeys<RequestBodyObj<T>, "content">;
-export type RequestBodyMedia<T> = FilterKeys<RequestBodyContent<T>, MediaType> extends never ? FilterKeys<NonNullable<RequestBodyContent<T>>, MediaType> | undefined : FilterKeys<RequestBodyContent<T>, MediaType>;
-export type RequestBody<T> = RequestBodyMedia<T> extends never ? { body?: never } : undefined extends RequestBodyMedia<T> ? { body?: RequestBodyMedia<T> } : { body: RequestBodyMedia<T> };
-export type QuerySerializer<T> = (query: T extends { parameters: any } ? NonNullable<T["parameters"]["query"]> : Record<string, unknown>) => string;
-export type BodySerializer<T> = (body: RequestBodyMedia<T>) => any;
-export type RequestOptions<T> = Params<T> &
-  RequestBody<T> & {
+export type ParamsOption<T> = T extends { parameters: any } ? { params: NonNullable<T["parameters"]> } : DefaultParamsOption;
+export type RequestBodyOption<T> = OperationRequestBodyContent<T> extends never ? { body?: never } : undefined extends OperationRequestBodyContent<T> ? { body?: OperationRequestBodyContent<T> } : { body: OperationRequestBodyContent<T> };
+export type FetchOptions<T> = RequestOptions<T> & Omit<RequestInit, "body">;
+export type FetchResponse<T> =
+  | { data: FilterKeys<SuccessResponse<ResponseObjectMap<T>>, MediaType>; error?: never; response: Response }
+  | { data?: never; error: FilterKeys<ErrorResponse<ResponseObjectMap<T>>, MediaType>; response: Response };
+export type RequestOptions<T> = ParamsOption<T> &
+  RequestBodyOption<T> & {
     querySerializer?: QuerySerializer<T>;
     bodySerializer?: BodySerializer<T>;
     parseAs?: ParseAs;
   };
-export type Success<T> = FilterKeys<FilterKeys<T, OkStatus>, "content">;
-export type Error<T> = FilterKeys<FilterKeys<T, ErrorStatus>, "content">;
-
-// fetch types
-export type FetchOptions<T> = RequestOptions<T> & Omit<RequestInit, "body">;
-export type FetchResponse<T> =
-  | { data: T extends { responses: any } ? NonNullable<FilterKeys<Success<T["responses"]>, MediaType>> : unknown; error?: never; response: Response }
-  | { data?: never; error: T extends { responses: any } ? NonNullable<FilterKeys<Error<T["responses"]>, MediaType>> : unknown; response: Response };
 
 export default function createClient<Paths extends {}>(clientOptions: ClientOptions = {}) {
   const { fetch = globalThis.fetch, querySerializer: globalQuerySerializer, bodySerializer: globalBodySerializer, ...options } = clientOptions;
@@ -94,7 +65,7 @@ export default function createClient<Paths extends {}>(clientOptions: ClientOpti
     // handle empty content
     // note: we return `{}` because we want user truthy checks for `.data` or `.error` to succeed
     if (response.status === 204 || response.headers.get("Content-Length") === "0") {
-      return response.ok ? { data: {} as any, response } : { error: {} as any, response };
+      return response.ok ? { data: {} as any, response: response as any } : { error: {} as any, response: response as any };
     }
 
     // parse response (falling back to .text() when necessary)
@@ -104,7 +75,7 @@ export default function createClient<Paths extends {}>(clientOptions: ClientOpti
         const cloned = response.clone();
         data = typeof cloned[parseAs] === "function" ? await cloned[parseAs]() : await cloned.text();
       }
-      return { data, response };
+      return { data, response: response as any };
     }
 
     // handle errors (always parse as .json() or .text())
@@ -114,40 +85,40 @@ export default function createClient<Paths extends {}>(clientOptions: ClientOpti
     } catch {
       error = await response.clone().text();
     }
-    return { error, response };
+    return { error, response: response as any };
   }
 
   return {
     /** Call a GET endpoint */
-    async GET<P extends PathsWith<Paths, "get">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "get">>) {
+    async GET<P extends PathsWithMethod<Paths, "get">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "get">>) {
       return coreFetch<P, "get">(url, { ...init, method: "GET" } as any);
     },
     /** Call a PUT endpoint */
-    async PUT<P extends PathsWith<Paths, "put">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "put">>) {
+    async PUT<P extends PathsWithMethod<Paths, "put">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "put">>) {
       return coreFetch<P, "put">(url, { ...init, method: "PUT" } as any);
     },
     /** Call a POST endpoint */
-    async POST<P extends PathsWith<Paths, "post">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "post">>) {
+    async POST<P extends PathsWithMethod<Paths, "post">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "post">>) {
       return coreFetch<P, "post">(url, { ...init, method: "POST" } as any);
     },
     /** Call a DELETE endpoint */
-    async DELETE<P extends PathsWith<Paths, "delete">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "delete">>) {
+    async DELETE<P extends PathsWithMethod<Paths, "delete">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "delete">>) {
       return coreFetch<P, "delete">(url, { ...init, method: "DELETE" } as any);
     },
     /** Call a OPTIONS endpoint */
-    async OPTIONS<P extends PathsWith<Paths, "options">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "options">>) {
+    async OPTIONS<P extends PathsWithMethod<Paths, "options">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "options">>) {
       return coreFetch<P, "options">(url, { ...init, method: "OPTIONS" } as any);
     },
     /** Call a HEAD endpoint */
-    async HEAD<P extends PathsWith<Paths, "head">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "head">>) {
+    async HEAD<P extends PathsWithMethod<Paths, "head">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "head">>) {
       return coreFetch<P, "head">(url, { ...init, method: "HEAD" } as any);
     },
     /** Call a PATCH endpoint */
-    async PATCH<P extends PathsWith<Paths, "patch">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "patch">>) {
+    async PATCH<P extends PathsWithMethod<Paths, "patch">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "patch">>) {
       return coreFetch<P, "patch">(url, { ...init, method: "PATCH" } as any);
     },
     /** Call a TRACE endpoint */
-    async TRACE<P extends PathsWith<Paths, "trace">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "trace">>) {
+    async TRACE<P extends PathsWithMethod<Paths, "trace">>(url: P, init: FetchOptions<FilterKeys<Paths[P], "trace">>) {
       return coreFetch<P, "trace">(url, { ...init, method: "TRACE" } as any);
     },
   };
diff --git a/packages/openapi-typescript-helpers/CHANGELOG.md b/packages/openapi-typescript-helpers/CHANGELOG.md
new file mode 100644
index 000000000..30a964ead
--- /dev/null
+++ b/packages/openapi-typescript-helpers/CHANGELOG.md
@@ -0,0 +1,5 @@
+# openapi-typescript-helpers
+
+## 0.0.0
+
+Initial release
diff --git a/packages/openapi-typescript-helpers/LICENSE b/packages/openapi-typescript-helpers/LICENSE
new file mode 100644
index 000000000..5de76d308
--- /dev/null
+++ b/packages/openapi-typescript-helpers/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2023 Drew Powers
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/packages/openapi-typescript-helpers/README.md b/packages/openapi-typescript-helpers/README.md
new file mode 100644
index 000000000..0fbf9c367
--- /dev/null
+++ b/packages/openapi-typescript-helpers/README.md
@@ -0,0 +1,5 @@
+# openapi-typescript-helpers
+
+Helper utilities that power `openapi-fetch` but are generically-available for any project.
+
+This package isn’t as well-documented as the others, so it’s a bit “use at your own discretion.”
diff --git a/packages/openapi-typescript-helpers/index.d.ts b/packages/openapi-typescript-helpers/index.d.ts
new file mode 100644
index 000000000..357a95101
--- /dev/null
+++ b/packages/openapi-typescript-helpers/index.d.ts
@@ -0,0 +1,42 @@
+/* eslint-disable @typescript-eslint/no-explicit-any, @typescript-eslint/ban-types */
+
+// HTTP types
+
+export type HttpMethod = "get" | "put" | "post" | "delete" | "options" | "head" | "patch" | "trace";
+/** 2XX statuses */
+export type OkStatus = 200 | 201 | 202 | 203 | 204 | 206 | 207 | "2XX";
+// prettier-ignore
+/** 4XX and 5XX statuses */
+export type ErrorStatus = 500 | '5XX' | 400 | 401 | 402 | 403 | 404 | 405 | 406 | 407 | 408 | 409 | 410 | 411 | 412 | 413 | 414 | 415 | 416 | 417 | 418 | 420 | 421 | 422 | 423 | 424 | 425 | 426 | 429 | 431 | 444 | 450 | 451 | 497 | 498 | 499 | '4XX' | "default";
+
+// OpenAPI type helpers
+
+/** Given an OpenAPI **Paths Object**, find all paths that have the given method */
+export type PathsWithMethod<Paths extends Record<string, PathItemObject>, PathnameMethod extends HttpMethod> = {
+  [Pathname in keyof Paths]: Paths[Pathname] extends { [K in PathnameMethod]: any } ? Pathname : never;
+}[keyof Paths];
+/** Internal helper used in PathsWithMethod */
+export type PathItemObject = { [M in HttpMethod]: OperationObject } & { parameters?: any };
+/** Return `responses` for an Operation Object */
+export type ResponseObjectMap<T> = T extends { responses: any } ? T["responses"] : unknown;
+/** Return `content` for a Response Object */
+export type ResponseContent<T> = T extends { content: any } ? T["content"] : unknown;
+/** Return `requestBody` for an Operation Object */
+export type OperationRequestBody<T> = T extends { requestBody?: any } ? T["requestBody"] : never;
+/** Internal helper used in OperationRequestBodyContent */
+export type OperationRequestBodyMediaContent<T> = undefined extends OperationRequestBody<T> ? FilterKeys<NonNullable<OperationRequestBody<T>>, "content"> | undefined : FilterKeys<OperationRequestBody<T>, "content">;
+/** Return first `content` from a Request Object Mapping, allowing any media type */
+export type OperationRequestBodyContent<T> = FilterKeys<OperationRequestBodyMediaContent<T>, MediaType> extends never
+  ? FilterKeys<NonNullable<OperationRequestBodyMediaContent<T>>, MediaType> | undefined
+  : FilterKeys<OperationRequestBodyMediaContent<T>, MediaType>;
+/** Return first 2XX response from a Response Object Map */
+export type SuccessResponse<T> = FilterKeys<FilterKeys<T, OkStatus>, "content">;
+/** Return first 5XX or 4XX response (in that order) from a Response Object Map */
+export type ErrorResponse<T> = FilterKeys<FilterKeys<T, ErrorStatus>, "content">;
+
+// Generic TS utils
+
+/** Find first match of multiple keys */
+export type FilterKeys<Obj, Matchers> = { [K in keyof Obj]: K extends Matchers ? Obj[K] : never }[keyof Obj];
+/** Return any `[string]/[string]` media type (important because openapi-fetch allows any content response, not just JSON-like) */
+export type MediaType = `${string}/${string}`;
diff --git a/packages/openapi-typescript-helpers/index.js b/packages/openapi-typescript-helpers/index.js
new file mode 100644
index 000000000..6e5f33030
--- /dev/null
+++ b/packages/openapi-typescript-helpers/index.js
@@ -0,0 +1,4 @@
+/**
+ * Stub file to allow importing from the root of the package.
+ */
+export default null;
diff --git a/packages/openapi-typescript-helpers/package.json b/packages/openapi-typescript-helpers/package.json
new file mode 100644
index 000000000..c7241d4e9
--- /dev/null
+++ b/packages/openapi-typescript-helpers/package.json
@@ -0,0 +1,38 @@
+{
+  "name": "openapi-typescript-helpers",
+  "description": "TypeScript helpers for consuming openapi-typescript types",
+  "version": "0.0.1",
+  "author": {
+    "name": "Drew Powers",
+    "email": "drew@pow.rs"
+  },
+  "license": "MIT",
+  "type": "module",
+  "main": "./index.js",
+  "types": "./index.d.ts",
+  "exports": {
+    ".": {
+      "default": "./index.js",
+      "types": "./index.d.ts"
+    },
+    "./*": "./*"
+  },
+  "homepage": "https://openapi-ts.pages.dev",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/drwpow/openapi-typescript",
+    "directory": "packages/openapi-fetch"
+  },
+  "bugs": {
+    "url": "https://github.com/drwpow/openapi-typescript/issues"
+  },
+  "scripts": {
+    "lint": "pnpm run lint:js",
+    "lint:js": "eslint \"*.{js,ts}\"",
+    "lint:prettier": "prettier --check \"{src,test}/**/*\"",
+    "test": "tsc --noEmit"
+  },
+  "devDependencies": {
+    "typescript": "^5.1.6"
+  }
+}
diff --git a/packages/openapi-typescript-helpers/tsconfig.json b/packages/openapi-typescript-helpers/tsconfig.json
new file mode 100644
index 000000000..762bd96d6
--- /dev/null
+++ b/packages/openapi-typescript-helpers/tsconfig.json
@@ -0,0 +1,7 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "."
+  },
+  "include": ["."]
+}
diff --git a/packages/openapi-typescript/tsconfig.json b/packages/openapi-typescript/tsconfig.json
index a5d4a6abb..bd4969bc2 100644
--- a/packages/openapi-typescript/tsconfig.json
+++ b/packages/openapi-typescript/tsconfig.json
@@ -2,7 +2,8 @@
   "extends": "../../tsconfig.json",
   "compilerOptions": {
     "sourceRoot": ".",
-    "outDir": "dist"
+    "outDir": "dist",
+    "types": ["vitest/globals"]
   },
   "include": ["scripts", "src", "test", "*.ts"],
   "exclude": ["examples", "node_modules"]
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 86392e437..cc2d7fc37 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -101,6 +101,10 @@ importers:
         version: 5.1.6
 
   packages/openapi-fetch:
+    dependencies:
+      openapi-typescript-helpers:
+        specifier: ^0.0.1
+        version: link:../openapi-typescript-helpers
     devDependencies:
       axios:
         specifier: ^1.4.0
@@ -188,6 +192,12 @@ importers:
         specifier: ^0.34.1
         version: 0.34.1(supports-color@9.4.0)
 
+  packages/openapi-typescript-helpers:
+    devDependencies:
+      typescript:
+        specifier: ^5.1.6
+        version: 5.1.6
+
 packages:
 
   /@aashutoshrathi/word-wrap@1.2.6:
diff --git a/tsconfig.json b/tsconfig.json
index 204c13843..93bb9800a 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -12,7 +12,6 @@
     "sourceMap": true,
     "strict": true,
     "target": "ESNext",
-    "types": ["vitest/globals"],
     "useDefineForClassFields": true
   }
 }