diff --git a/.vscode/settings.json b/.vscode/settings.json
index 25fa6215f..8400d618a 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -1,3 +1,4 @@
 {
-  "typescript.tsdk": "node_modules/typescript/lib"
+  "typescript.tsdk": "node_modules/typescript/lib",
+  "cSpell.words": ["fets"]
 }
diff --git a/benchmark/start-server.ts b/benchmark/start-server.ts
index e7a0ed536..7bc184a8c 100644
--- a/benchmark/start-server.ts
+++ b/benchmark/start-server.ts
@@ -115,6 +115,11 @@ const router = createRouter({
     handler,
   });
 
+// @ts-ignore  Types of parameters 'req' and 'req' are incompatible.
+// Type 'IncomingMessage' is not assignable to type 'NodeRequest' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
+// Types of property 'url' are incompatible.
+//   Type 'string | undefined' is not assignable to type 'string'.
+//     Type 'undefined' is not assignable to type 'string'.
 createServer(router).listen(4000, () => {
   readyCount++;
   console.log('listening on 0.0.0.0:4000');
diff --git a/e2e/shared-scripts/src/types.ts b/e2e/shared-scripts/src/types.ts
index 899003742..5ebe11859 100644
--- a/e2e/shared-scripts/src/types.ts
+++ b/e2e/shared-scripts/src/types.ts
@@ -3,8 +3,8 @@ import { OutputValue, Stack } from '@pulumi/pulumi/automation';
 
 export type DeploymentConfiguration<TProgramOutput = any> = {
   name: string;
-  prerequisites?: (stack: Stack) => Promise<void>;
-  config?: (stack: Stack) => Promise<void>;
+  prerequisites?: ((stack: Stack) => Promise<void>) | undefined;
+  config?: ((stack: Stack) => Promise<void>) | undefined;
   program: () => Promise<{
     [K in keyof TProgramOutput]: Output<TProgramOutput[K]> | TProgramOutput[K];
   }>;
diff --git a/e2e/shared-server/src/index.ts b/e2e/shared-server/src/index.ts
index b25eb638f..8517e1596 100644
--- a/e2e/shared-server/src/index.ts
+++ b/e2e/shared-server/src/index.ts
@@ -1,7 +1,7 @@
 import { createRouter, Response, useErrorHandling } from 'fets';
 import { z } from 'zod';
 
-export function createTestServerAdapter<TServerContext = {}>(base?: string) {
+export function createTestServerAdapter<TServerContext = {}>(base?: string | undefined) {
   return createRouter<TServerContext, {}>({
     base,
     plugins: [useErrorHandling()],
diff --git a/examples/todolist/src/router.ts b/examples/todolist/src/router.ts
index 3cce6547b..06dbae395 100644
--- a/examples/todolist/src/router.ts
+++ b/examples/todolist/src/router.ts
@@ -25,7 +25,7 @@ export const router = createRouter({
       schemas: {
         Todo: TodoSchema,
       },
-    } as const,
+    },
   },
 })
   .route({
@@ -42,7 +42,9 @@ export const router = createRouter({
         },
       },
     } as const,
-    handler: () => Response.json(todos),
+    handler: () => {
+      return Response.json(todos);
+    },
   })
   .route({
     description: 'Get a todo',
@@ -193,7 +195,7 @@ export const router = createRouter({
           required: ['file'],
           additionalProperties: false,
         },
-      },
+      } as const,
       responses: {
         200: {
           type: 'object',
@@ -213,12 +215,15 @@ export const router = createRouter({
       const body = await request.formData();
       const file = body.get('file');
       const description = body.get('description');
-      return Response.json({
+
+      const json = {
         name: file.name,
-        description,
+        description: description || '',
         type: file.type,
         size: file.size,
         lastModified: file.lastModified,
-      });
+      } as const;
+
+      return Response.json(json);
     },
   });
diff --git a/examples/zod-example/src/index.ts b/examples/zod-example/src/index.ts
index 0a10913b7..50af43f78 100644
--- a/examples/zod-example/src/index.ts
+++ b/examples/zod-example/src/index.ts
@@ -96,6 +96,12 @@ export const router = createRouter()
     },
   });
 
+// TODO: Type 'IncomingMessage' is not assignable to type 'NodeRequest' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
+// Types of property 'url' are incompatible.
+// Type 'string | undefined' is not assignable to type 'string'.
+// Type 'undefined' is not assignable to type 'string'.
+// eslint-disable-next-line @typescript-eslint/ban-ts-comment
+// @ts-ignore
 createServer(router).listen(3000, () => {
   console.log('SwaggerUI is served at http://localhost:3000/docs');
 });
diff --git a/examples/zod-example/tsconfig.json b/examples/zod-example/tsconfig.json
index 7e87753c3..5a013a7a9 100644
--- a/examples/zod-example/tsconfig.json
+++ b/examples/zod-example/tsconfig.json
@@ -1,4 +1,5 @@
 {
+  "extends": "../../tsconfig.json",
   "compilerOptions": {
     "target": "esnext",
     "moduleResolution": "node",
diff --git a/packages/fets/src/createRouter.ts b/packages/fets/src/createRouter.ts
index 28be5c03a..7163e0848 100644
--- a/packages/fets/src/createRouter.ts
+++ b/packages/fets/src/createRouter.ts
@@ -38,13 +38,13 @@ const HTTP_METHODS: HTTPMethod[] = [
 const EMPTY_OBJECT = {};
 const EMPTY_MATCH = { pathname: { groups: {} } } as URLPatternResult;
 
-export function createRouterBase(
+export function createRouterBase<TServerContext>(
   {
     fetchAPI: givenFetchAPI,
     base: basePath = '/',
     plugins = [],
     swaggerUI,
-  }: RouterOptions<any, any> = {},
+  }: RouterOptions<TServerContext, any>,
   openAPIDocument: OpenAPIDocument,
 ): RouterBaseObject<any, any, any> {
   const fetchAPI = {
@@ -325,19 +325,20 @@ export function createRouterBase(
 
 export function createRouter<
   TServerContext,
-  TComponents extends RouterComponentsBase = {},
+  TComponents extends RouterComponentsBase,
   TRouterSDK extends RouterSDK<string, TypedRequest, TypedResponse> = {
     [TKey: string]: never;
   },
 >(
-  options: RouterOptions<TServerContext, TComponents> = {},
+  options?: RouterOptions<TServerContext, TComponents> | undefined,
 ): Router<TServerContext, TComponents, TRouterSDK> {
   const {
     openAPI: { endpoint: oasEndpoint = '/openapi.json', ...openAPIDocument } = {},
     swaggerUI: { endpoint: swaggerUIEndpoint = '/docs', ...swaggerUIOpts } = {},
     plugins: userPlugins = [],
     base = '/',
-  } = options;
+  } = options || {};
+
   openAPIDocument.openapi = openAPIDocument.openapi || '3.0.1';
   const oasInfo = (openAPIDocument.info ||= {} as OpenAPIInfo);
   oasInfo.title ||= 'feTS API';
@@ -373,9 +374,26 @@ export function createRouter<
     plugins,
   };
   const routerBaseObject = createRouterBase(finalOpts, openAPIDocument as OpenAPIDocument);
+
+  // Argument of type 'RouterOptions<TServerContext, TComponents>' is not assignable to parameter of type 'ServerAdapterOptions<TServerContext>' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
+  // Types of property 'plugins' are incompatible.
+  // Type 'RouterPlugin<TServerContext>[] | undefined' is not assignable to type 'ServerAdapterPlugin<TServerContext>[]'.
+  //   Type 'undefined' is not assignable to type 'ServerAdapterPlugin<TServerContext>[]'.
+  // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+  // @ts-ignore
   const router = createServerAdapter(routerBaseObject, finalOpts);
+
   for (const onRouterInitHook of routerBaseObject.__onRouterInitHooks) {
+    // Argument of type 'ServerAdapter<TServerContext, ServerAdapterBaseObject<TServerContext, ServerAdapterRequestHandler<TServerContext>>>' is not assignable to parameter of type 'Router<any, any, any>'.
+    // Type 'ServerAdapter<TServerContext, ServerAdapterBaseObject<TServerContext, ServerAdapterRequestHandler<TServerContext>>>' is not assignable to type 'RouterBaseObject<any, any, any>'.
+    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+    // @ts-ignore
     onRouterInitHook(router);
   }
+
+  // Type 'ServerAdapter<TServerContext, ServerAdapterBaseObject<TServerContext, ServerAdapterRequestHandler<TServerContext>>>' is not assignable to type 'Router<TServerContext, TComponents, TRouterSDK>'.
+  // Type 'ServerAdapter<TServerContext, ServerAdapterBaseObject<TServerContext, ServerAdapterRequestHandler<TServerContext>>>' is not assignable to type 'RouterBaseObject<TServerContext, TComponents, TRouterSDK>'.
+  // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+  // @ts-ignore
   return router;
 }
diff --git a/packages/fets/src/plugins/ajv.ts b/packages/fets/src/plugins/ajv.ts
index c02e7333a..5e92b74c1 100644
--- a/packages/fets/src/plugins/ajv.ts
+++ b/packages/fets/src/plugins/ajv.ts
@@ -4,8 +4,8 @@ import addFormats from 'ajv-formats';
 import jsonSerializerFactory from '@ardatan/fast-json-stringify';
 import { URL } from '@whatwg-node/fetch';
 import { Response } from '../Response.js';
-import { StatusCode } from '../typed-fetch.js';
-import {
+import type { StatusCode } from '../typed-fetch.js';
+import type {
   JSONSerializer,
   PromiseOrValue,
   RouterComponentsBase,
@@ -18,9 +18,9 @@ import { getHeadersObj } from './utils.js';
 type ValidateRequestFn = (request: RouterRequest) => PromiseOrValue<ErrorObject[]>;
 
 export function useAjv({
-  components = {},
+  components = { schemas: {} },
 }: {
-  components?: RouterComponentsBase;
+  components?: RouterComponentsBase | undefined;
 } = {}): RouterPlugin<any> {
   const ajv = new Ajv({
     strict: false,
@@ -73,10 +73,16 @@ export function useAjv({
     onRoute({ path, schemas, handlers }) {
       const validationMiddlewares = new Map<string, ValidateRequestFn>();
       if (schemas?.request?.headers && !isZodSchema(schemas.request.headers)) {
+        const { headers } = schemas.request;
+
+        // TODO: Property '$async' is missing in type '{ components: RouterComponentsBase; type?: JSONSchema7TypeName | JSONSchema7TypeName[] | undefined; pattern?: string | undefined; ... 46 more ...; [$JSONSchema7]?: unique symbol; }' but required in type 'AsyncSchema'
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
         const validateFn = ajv.compile({
-          ...schemas.request.headers,
+          ...headers,
           components,
         });
+
         validationMiddlewares.set('headers', request => {
           const headersObj = getHeadersObj(request.headers);
           const isValid = validateFn(headersObj);
@@ -87,10 +93,14 @@ export function useAjv({
         });
       }
       if (schemas?.request?.params && !isZodSchema(schemas.request.params)) {
+        // TODO: Property '$async' is missing in type '{ components: RouterComponentsBase; type?: JSONSchema7TypeName | JSONSchema7TypeName[] | undefined; pattern?: string | undefined; ... 46 more ...; [$JSONSchema7]?: unique symbol; }' but required in type 'AsyncSchema'
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
         const validateFn = ajv.compile({
           ...schemas.request.params,
           components,
         });
+
         validationMiddlewares.set('params', request => {
           const isValid = validateFn(request.params);
           if (!isValid) {
@@ -100,10 +110,14 @@ export function useAjv({
         });
       }
       if (schemas?.request?.query && !isZodSchema(schemas.request.query)) {
+        // TODO: Property '$async' is missing in type '{ components: RouterComponentsBase; type?: JSONSchema7TypeName | JSONSchema7TypeName[] | undefined; pattern?: string | undefined; ... 46 more ...; [$JSONSchema7]?: unique symbol; }' but required in type 'AsyncSchema'
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
         const validateFn = ajv.compile({
           ...schemas.request.query,
           components,
         });
+
         validationMiddlewares.set('query', request => {
           const isValid = validateFn(request.query);
           if (!isValid) {
@@ -113,10 +127,14 @@ export function useAjv({
         });
       }
       if (schemas?.request?.json && !isZodSchema(schemas.request.json)) {
+        // TODO: Property '$async' is missing in type '{ components: RouterComponentsBase; type?: JSONSchema7TypeName | JSONSchema7TypeName[] | undefined; pattern?: string | undefined; ... 46 more ...; [$JSONSchema7]?: unique symbol; }' but required in type 'AsyncSchema'
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
         const validateFn = ajv.compile({
           ...schemas.request.json,
           components,
         });
+
         validationMiddlewares.set('json', async request => {
           const contentType = request.headers.get('content-type');
           if (contentType?.includes('json')) {
@@ -134,10 +152,14 @@ export function useAjv({
         });
       }
       if (schemas?.request?.formData && !isZodSchema(schemas.request.formData)) {
+        // TODO: Property '$async' is missing in type '{ components: RouterComponentsBase; type?: JSONSchema7TypeName | JSONSchema7TypeName[] | undefined; pattern?: string | undefined; ... 46 more ...; [$JSONSchema7]?: unique symbol; }' but required in type 'AsyncSchema'
+        // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+        // @ts-ignore
         const validateFn = ajv.compile({
           ...schemas.request.formData,
           components,
         });
+
         validationMiddlewares.set('formData', async request => {
           const contentType = request.headers.get('content-type');
           if (
@@ -145,14 +167,18 @@ export function useAjv({
             contentType?.includes('application/x-www-form-urlencoded')
           ) {
             const formData = await request.formData();
-            const formDataObj: Record<string, FormDataEntryValue> = {};
+            const formDataObj: Record<string, FormDataEntryValue | undefined> = {};
             const jobs: Promise<void>[] = [];
             formData.forEach((value, key) => {
+              if (typeof value === 'undefined') {
+                return;
+              }
+
               if (typeof value === 'string') {
                 formDataObj[key] = value;
               } else {
                 jobs.push(
-                  value.arrayBuffer().then(buffer => {
+                  value.arrayBuffer().then((buffer: ArrayBuffer): void => {
                     const typedArray = new Uint8Array(buffer);
                     const binaryStrParts: string[] = [];
                     typedArray.forEach((byte, index) => {
diff --git a/packages/fets/src/plugins/openapi.ts b/packages/fets/src/plugins/openapi.ts
index 85450c42e..ebfad575e 100644
--- a/packages/fets/src/plugins/openapi.ts
+++ b/packages/fets/src/plugins/openapi.ts
@@ -3,38 +3,39 @@ import { Response } from '../Response.js';
 import swaggerUiHtml from '../swagger-ui-html.js';
 import { StatusCode } from '../typed-fetch.js';
 import {
+  JSONSchema,
   OpenAPIDocument,
   OpenAPIOperationObject,
   OpenAPIPathObject,
   RouterPlugin,
 } from '../types.js';
-import { isZodSchema } from '../zod/types.js';
+import { isZodSchema, ZodType } from '../zod/types.js';
 
 export interface SwaggerUIOpts {
-  spec?: OpenAPIDocument;
-  dom_id?: string;
-  displayOperationId?: boolean;
-  tryItOutEnabled?: boolean;
-  requestSnippetsEnabled?: boolean;
-  displayRequestDuration?: boolean;
-  defaultModelRendering?: 'model' | 'example' | 'schema';
-  defaultModelExpandDepth?: number;
-  defaultModelsExpandDepth?: number;
-  docExpansion?: 'none' | 'list' | 'full';
-  filter?: boolean;
-  maxDisplayedTags?: number;
-  showExtensions?: boolean;
-  showCommonExtensions?: boolean;
-  tagsSorter?: 'alpha';
-  operationsSorter?: 'alpha';
-  showTags?: boolean;
-  showMutatedRequest?: boolean;
-  oauth2RedirectUrl?: string;
-  validatorUrl?: string;
-  deepLinking?: boolean;
-  presets?: any[];
-  plugins?: any[];
-  layout?: string;
+  spec?: OpenAPIDocument | undefined;
+  dom_id?: string | undefined;
+  displayOperationId?: boolean | undefined;
+  tryItOutEnabled?: boolean | undefined;
+  requestSnippetsEnabled?: boolean | undefined;
+  displayRequestDuration?: boolean | undefined;
+  defaultModelRendering?: 'model' | 'example' | 'schema' | undefined;
+  defaultModelExpandDepth?: number | undefined;
+  defaultModelsExpandDepth?: number | undefined;
+  docExpansion?: 'none' | 'list' | 'full' | undefined;
+  filter?: boolean | undefined;
+  maxDisplayedTags?: number | undefined;
+  showExtensions?: boolean | undefined;
+  showCommonExtensions?: boolean | undefined;
+  tagsSorter?: 'alpha' | undefined;
+  operationsSorter?: 'alpha' | undefined;
+  showTags?: boolean | undefined;
+  showMutatedRequest?: boolean | undefined;
+  oauth2RedirectUrl?: string | undefined;
+  validatorUrl?: string | undefined;
+  deepLinking?: boolean | undefined;
+  presets?: any[] | undefined;
+  plugins?: any[] | undefined;
+  layout?: string | undefined;
 }
 
 export type OpenAPIPluginOptions = {
@@ -43,11 +44,11 @@ export type OpenAPIPluginOptions = {
   swaggerUIOpts: SwaggerUIOpts;
 };
 
-export function useOpenAPI({
+export function useOpenAPI<TServerContext = any>({
   oasEndpoint,
   swaggerUIEndpoint,
   swaggerUIOpts,
-}: OpenAPIPluginOptions): RouterPlugin<any> {
+}: OpenAPIPluginOptions): RouterPlugin<TServerContext> {
   let paths: Record<string, OpenAPIPathObject>;
   return {
     onRouterInit(router) {
@@ -97,7 +98,7 @@ export function useOpenAPI({
         if (!pathForOAS.startsWith('/')) {
           pathForOAS = `/${pathForOAS}`;
         }
-        const pathObj: any = (paths[pathForOAS] = paths[pathForOAS] || {});
+        const pathObj = (paths[pathForOAS] = paths[pathForOAS] || {});
         const lowerCasedMethod = method.toLowerCase();
         pathObj[lowerCasedMethod] = pathObj[lowerCasedMethod] || {};
         const operation = pathObj[lowerCasedMethod] as OpenAPIOperationObject;
@@ -106,9 +107,14 @@ export function useOpenAPI({
         operation.tags = tags;
         if (schemas.responses) {
           for (const statusCode in schemas.responses) {
-            let responseSchema = schemas.responses[statusCode as any as StatusCode];
+            let responseSchema: JSONSchema | ZodType | undefined =
+              schemas.responses[statusCode as unknown as StatusCode];
+
             if (isZodSchema(responseSchema)) {
-              responseSchema = zodToJsonSchema(responseSchema as any, {
+              // TODO: Possible bug. zodToJsonSchema is not returning the correct type.
+              // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+              // @ts-ignore
+              responseSchema = zodToJsonSchema(responseSchema, {
                 target: 'openApi3',
               });
             }
@@ -117,7 +123,7 @@ export function useOpenAPI({
               description: '',
               content: {
                 'application/json': {
-                  schema: responseSchema as any,
+                  schema: responseSchema,
                 },
               },
             };
@@ -130,80 +136,109 @@ export function useOpenAPI({
           };
         }
         if (schemas.request?.headers) {
-          let headersSchema: any = schemas.request.headers;
+          let headersSchema = schemas.request.headers;
+
           if (isZodSchema(headersSchema)) {
-            headersSchema = zodToJsonSchema(headersSchema as any, {
+            // TODO: Possible bug. zodToJsonSchema is not returning the correct type.
+            // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+            // @ts-ignore
+            headersSchema = zodToJsonSchema(headersSchema, {
               target: 'openApi3',
             });
           }
-          for (const headerName in headersSchema.properties) {
-            const headerSchema = headersSchema.properties[headerName];
-            operation.parameters = operation.parameters || [];
-            operation.parameters.push({
-              name: headerName,
-              in: 'header',
-              required: headersSchema.required?.includes(headerName),
-              schema: headerSchema,
-            });
+          if ('properties' in headersSchema) {
+            for (const headerName in headersSchema.properties) {
+              const headerSchema = headersSchema.properties[headerName];
+              operation.parameters = operation.parameters || [];
+              operation.parameters.push({
+                name: headerName,
+                in: 'header',
+                required: headersSchema.required?.includes(headerName),
+                schema: headerSchema,
+              });
+            }
           }
         }
         if (schemas.request?.params) {
-          let paramsSchema: any = schemas.request.params;
+          let paramsSchema = schemas.request.params;
+
           if (isZodSchema(paramsSchema)) {
-            paramsSchema = zodToJsonSchema(paramsSchema as any, {
+            // TODO: Possible bug. zodToJsonSchema is not returning the correct type.
+            // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+            // @ts-ignore
+            paramsSchema = zodToJsonSchema(paramsSchema, {
               target: 'openApi3',
             });
           }
-          for (const paramName in paramsSchema.properties) {
-            const paramSchema: any = paramsSchema.properties[paramName];
-            operation.parameters = operation.parameters || [];
-            operation.parameters.push({
-              name: paramName,
-              in: 'path',
-              required: paramsSchema.required?.includes(paramName),
-              schema: paramSchema,
-            });
+
+          if ('properties' in paramsSchema) {
+            for (const paramName in paramsSchema.properties) {
+              const paramSchema = paramsSchema.properties[paramName];
+
+              operation.parameters = operation.parameters || [];
+              operation.parameters.push({
+                name: paramName,
+                in: 'path',
+                required: paramsSchema.required?.includes(paramName),
+                schema: paramSchema,
+              });
+            }
           }
         }
         if (schemas.request?.query) {
-          let queriesSchema: any = schemas.request.query;
+          let queriesSchema = schemas.request.query;
           if (isZodSchema(queriesSchema)) {
-            queriesSchema = zodToJsonSchema(queriesSchema as any, {
+            // TODO: Possible bug. zodToJsonSchema is not returning the correct type.
+            // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+            // @ts-ignore
+            queriesSchema = zodToJsonSchema(queriesSchema, {
               target: 'openApi3',
             });
           }
-          for (const queryName in queriesSchema.properties) {
-            const querySchema = queriesSchema.properties[queryName];
-            operation.parameters = operation.parameters || [];
-            operation.parameters.push({
-              name: queryName,
-              in: 'query',
-              required: queriesSchema.required?.includes(queryName),
-              schema: querySchema as any,
-            });
+
+          if ('properties' in queriesSchema) {
+            for (const queryName in queriesSchema.properties) {
+              const querySchema = queriesSchema.properties[queryName];
+              operation.parameters = operation.parameters || [];
+              operation.parameters.push({
+                name: queryName,
+                in: 'query',
+                required: queriesSchema.required?.includes(queryName),
+                schema: querySchema,
+              });
+            }
           }
         }
         if (schemas.request?.json) {
-          let requestJsonSchema: any = schemas.request.json;
+          let requestJsonSchema = schemas.request.json;
+
           if (isZodSchema(requestJsonSchema)) {
-            requestJsonSchema = zodToJsonSchema(requestJsonSchema as any, {
+            // TODO: Possible bug. zodToJsonSchema is not returning the correct type.
+            // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+            // @ts-ignore
+            requestJsonSchema = zodToJsonSchema(requestJsonSchema, {
               target: 'openApi3',
             });
           }
-          const requestBody = (operation.requestBody = (operation.requestBody || {}) as any);
+
+          const requestBody = (operation.requestBody = operation.requestBody || {});
           requestBody.required = true;
-          const requestBodyContent = (requestBody.content = (requestBody.content || {}) as any);
+          const requestBodyContent = (requestBody.content = requestBody.content || {});
           requestBodyContent['application/json'] = {
             schema: requestJsonSchema,
           };
         }
         if (schemas.request?.formData) {
-          const requestBody = (operation.requestBody = (operation.requestBody || {}) as any);
+          const requestBody = (operation.requestBody = operation.requestBody || {});
           requestBody.required = true;
-          const requestBodyContent = (requestBody.content = (requestBody.content || {}) as any);
-          let requestFormDataSchema: any = schemas.request.formData;
+          const requestBodyContent = (requestBody.content = requestBody.content || {});
+          let requestFormDataSchema = schemas.request.formData;
+
           if (isZodSchema(requestFormDataSchema)) {
-            requestFormDataSchema = zodToJsonSchema(requestFormDataSchema as any, {
+            // TODO: Possible bug. zodToJsonSchema is not returning the correct type.
+            // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+            // @ts-ignore
+            requestFormDataSchema = zodToJsonSchema(requestFormDataSchema, {
               target: 'openApi3',
             });
           }
diff --git a/packages/fets/src/typed-fetch.ts b/packages/fets/src/typed-fetch.ts
index c5bdacdd2..f2d9a81c2 100644
--- a/packages/fets/src/typed-fetch.ts
+++ b/packages/fets/src/typed-fetch.ts
@@ -47,7 +47,7 @@ export type NotOkStatusCode = Exclude<StatusCode, OkStatusCode>;
 
 export type TypedBody<
   TJSON,
-  TFormData extends Record<string, FormDataEntryValue>,
+  TFormData extends Record<string, FormDataEntryValue | undefined>,
   THeaders extends Record<string, string>,
 > = Omit<Body, 'json' | 'formData' | 'headers'> & {
   /**
@@ -314,7 +314,7 @@ export type HTTPMethod =
 export type TypedRequestInit<
   THeaders extends Record<string, string>,
   TMethod extends HTTPMethod,
-  TFormData extends Record<string, FormDataEntryValue>,
+  TFormData extends Record<string, FormDataEntryValue | undefined>,
 > = Omit<RequestInit, 'method' | 'headers' | 'body'> & {
   method: TMethod;
   headers: TypedHeaders<THeaders>;
@@ -323,7 +323,10 @@ export type TypedRequestInit<
 
 export type TypedRequest<
   TJSON = any,
-  TFormData extends Record<string, FormDataEntryValue> = Record<string, FormDataEntryValue>,
+  TFormData extends Record<string, FormDataEntryValue | undefined> = Record<
+    string,
+    FormDataEntryValue | undefined
+  >,
   THeaders extends Record<string, string> = Record<string, string>,
   TMethod extends HTTPMethod = HTTPMethod,
   TQueryParams extends Record<string, string | string[]> = Record<string, string | string[]>,
@@ -340,7 +343,7 @@ export type TypedRequestCtor = new <
   THeaders extends Record<string, string>,
   TMethod extends HTTPMethod,
   TQueryParams extends Record<string, string | string[]>,
-  TFormData extends Record<string, FormDataEntryValue>,
+  TFormData extends Record<string, FormDataEntryValue | undefined>,
 >(
   input: string | TypedURL<TQueryParams>,
   init?: TypedRequestInit<THeaders, TMethod, TFormData>,
@@ -391,7 +394,10 @@ export type TypedURLCtor = new <TQueryParams extends Record<string, string | str
 ) => TypedURL<TQueryParams>;
 
 export interface TypedFormData<
-  TMap extends Record<string, FormDataEntryValue> = Record<string, FormDataEntryValue>,
+  TMap extends Record<string, FormDataEntryValue | undefined> = Record<
+    string,
+    FormDataEntryValue | undefined
+  >,
 > {
   append<TName extends keyof TMap>(
     name: TName,
diff --git a/packages/fets/src/types.ts b/packages/fets/src/types.ts
index e903f96fe..9508369d1 100644
--- a/packages/fets/src/types.ts
+++ b/packages/fets/src/types.ts
@@ -34,42 +34,45 @@ export type JSONSerializer = (obj: any) => string;
 export type JSONSchema = Exclude<JSONSchemaOrBoolean, boolean>;
 
 export interface OpenAPIInfo {
-  title?: string;
-  description?: string;
-  version?: string;
-  license?: {
-    name?: string;
-    url?: string;
-  };
+  title?: string | undefined;
+  description?: string | undefined;
+  version?: string | undefined;
+  license?:
+    | {
+        name?: string | undefined;
+        url?: string | undefined;
+      }
+    | undefined;
 }
 
 export type OpenAPIPathObject = Record<string, OpenAPIOperationObject> & {
-  parameters?: OpenAPIParameterObject[];
+  parameters?: OpenAPIParameterObject[] | undefined;
 };
 
 export interface OpenAPIParameterObject {
   name: string;
   in: 'path' | 'query' | 'header' | 'cookie';
-  required?: boolean;
+  required?: boolean | undefined;
   schema?: any;
 }
 
 export interface OpenAPIRequestBodyObject {
-  content?: Record<string, OpenAPIMediaTypeObject>;
+  content?: Record<string, OpenAPIMediaTypeObject> | undefined;
+  required?: boolean | undefined;
 }
 
 export interface OpenAPIOperationObject {
-  operationId?: string;
-  description?: string;
-  tags?: string[];
-  parameters?: OpenAPIParameterObject[];
-  requestBody?: OpenAPIRequestBodyObject;
-  responses?: Record<string | number, OpenAPIResponseObject>;
+  operationId?: string | undefined;
+  description?: string | undefined;
+  tags?: string[] | undefined;
+  parameters?: OpenAPIParameterObject[] | undefined;
+  requestBody?: OpenAPIRequestBodyObject | undefined;
+  responses?: Record<string | number, OpenAPIResponseObject> | undefined;
 }
 
 export interface OpenAPIResponseObject {
-  description?: string;
-  content?: Record<string, OpenAPIMediaTypeObject>;
+  description?: string | undefined;
+  content?: Record<string, OpenAPIMediaTypeObject> | undefined;
 }
 
 export interface OpenAPIMediaTypeObject {
@@ -77,38 +80,46 @@ export interface OpenAPIMediaTypeObject {
 }
 
 export type OpenAPIDocument = {
-  openapi?: string;
-  info?: OpenAPIInfo;
+  openapi?: string | undefined;
+  info?: OpenAPIInfo | undefined;
   servers?:
     | {
         url: string;
       }[]
-    | string[];
-  paths?: Record<string, OpenAPIPathObject>;
+    | string[]
+    | undefined;
+  paths?: Record<string, OpenAPIPathObject> | undefined;
   components?: unknown;
 };
 
 export interface RouterOpenAPIOptions<TComponents extends RouterComponentsBase>
   extends OpenAPIDocument {
-  endpoint?: string | false;
-  components?: TComponents;
+  endpoint?: string | false | undefined;
+  components?: TComponents | undefined;
 }
 
 export interface RouterSwaggerUIOptions extends SwaggerUIOpts {
-  endpoint?: string | false;
+  endpoint?: string | false | undefined;
 }
 
+// I've created a PR to fix this in @whatwg-node/server https://github.com/ardatan/whatwg-node/issues/391
+// Interface 'RouterOptions<TServerContext, TComponents>' incorrectly extends interface 'ServerAdapterOptions<TServerContext>'.
+// Types of property 'plugins' are incompatible.
+// Type 'RouterPlugin<TServerContext>[] | undefined' is not assignable to type 'ServerAdapterPlugin<TServerContext>[]'.
+//   Type 'undefined' is not assignable to type 'ServerAdapterPlugin<TServerContext>[]'
+// eslint-disable-next-line @typescript-eslint/ban-ts-comment
+// @ts-ignore
 export interface RouterOptions<TServerContext, TComponents extends RouterComponentsBase>
   extends ServerAdapterOptions<TServerContext> {
-  base?: string;
-  plugins?: RouterPlugin<TServerContext>[];
+  base?: string | undefined;
+  plugins?: RouterPlugin<TServerContext>[] | undefined;
 
-  openAPI?: RouterOpenAPIOptions<TComponents>;
-  swaggerUI?: RouterSwaggerUIOptions;
+  openAPI?: RouterOpenAPIOptions<TComponents> | undefined;
+  swaggerUI?: RouterSwaggerUIOptions | undefined;
 }
 
 export type RouterComponentsBase = {
-  schemas?: Record<string, JSONSchema>;
+  schemas: Record<string, JSONSchema>;
 };
 /*
 Maybe later;
@@ -174,13 +185,16 @@ export type FromRouterComponentSchema<
 export type PromiseOrValue<T> = T | Promise<T>;
 
 export type StatusCodeMap<T> = {
-  [TKey in StatusCode]?: T;
+  [TKey in StatusCode]?: T | undefined;
 };
 
 export type TypedRouterHandlerTypeConfig<
   TPath extends string,
   TRequestJSON = any,
-  TRequestFormData extends Record<string, FormDataEntryValue> = Record<string, FormDataEntryValue>,
+  TRequestFormData extends Record<string, FormDataEntryValue | undefined> = Record<
+    string,
+    FormDataEntryValue | undefined
+  >,
   TRequestHeaders extends Record<string, string> = Record<string, string>,
   TRequestQueryParams extends Record<string, string | string[]> = Record<string, string | string[]>,
   TRequestPathParams extends Record<string, any> = Record<
@@ -190,13 +204,13 @@ export type TypedRouterHandlerTypeConfig<
   TResponseJSONStatusMap extends StatusCodeMap<any> = StatusCodeMap<any>,
 > = {
   request: {
-    json?: TRequestJSON;
-    formData?: TRequestFormData;
-    headers?: TRequestHeaders;
-    query?: TRequestQueryParams;
-    params?: TRequestPathParams;
+    json?: TRequestJSON | undefined;
+    formData?: TRequestFormData | undefined;
+    headers?: TRequestHeaders | undefined;
+    query?: TRequestQueryParams | undefined;
+    params?: TRequestPathParams | undefined;
   };
-  responses?: TResponseJSONStatusMap;
+  responses?: TResponseJSONStatusMap | undefined;
 };
 
 export type TypedRequestFromTypeConfig<
@@ -223,7 +237,7 @@ export type TypedRequestFromTypeConfig<
     : never
   : TypedRequest<
       any,
-      Record<string, FormDataEntryValue>,
+      Record<string, FormDataEntryValue | undefined>,
       Record<string, string>,
       TMethod,
       Record<string, string | string[]>,
@@ -332,12 +346,12 @@ export type RouteHandler<
 // TODO: Remove Response from here
 
 export type OnRouteHookPayload<TServerContext> = {
-  operationId?: string;
-  description?: string;
-  tags?: string[];
+  operationId?: string | undefined;
+  description?: string | undefined;
+  tags?: string[] | undefined;
   method: HTTPMethod;
   path: string;
-  schemas?: RouteSchemas | RouteZodSchemas;
+  schemas?: RouteSchemas | RouteZodSchemas | undefined;
   openAPIDocument: OpenAPIDocument;
   handlers: RouteHandler<TServerContext, TypedRequest, TypedResponse>[];
 };
@@ -356,20 +370,22 @@ export type OnSerializeResponseHook<TServerContext> = (
 ) => void;
 
 export type RouterPlugin<TServerContext> = ServerAdapterPlugin<TServerContext> & {
-  onRouterInit?: OnRouterInitHook<TServerContext>;
-  onRoute?: OnRouteHook<TServerContext>;
-  onSerializeResponse?: OnSerializeResponseHook<TServerContext>;
+  onRouterInit?: OnRouterInitHook<TServerContext> | undefined;
+  onRoute?: OnRouteHook<TServerContext> | undefined;
+  onSerializeResponse?: OnSerializeResponseHook<TServerContext> | undefined;
 };
 
 export type RouteSchemas = {
-  request?: {
-    headers?: JSONSchema;
-    params?: JSONSchema;
-    query?: JSONSchema;
-    json?: JSONSchema;
-    formData?: JSONSchema;
-  };
-  responses?: StatusCodeMap<JSONSchema>;
+  request?:
+    | {
+        headers?: JSONSchema | undefined;
+        params?: JSONSchema | undefined;
+        query?: JSONSchema | undefined;
+        json?: JSONSchema | undefined;
+        formData?: JSONSchema | undefined;
+      }
+    | undefined;
+  responses?: StatusCodeMap<JSONSchema> | undefined;
 };
 
 export type RouterSDKOpts<
@@ -384,11 +400,11 @@ export type RouterSDKOpts<
   infer TPathParam
 >
   ? {
-      json?: TJSONBody;
-      formData?: TFormData;
-      headers?: THeaders;
-      query?: TQueryParams;
-      params?: TPathParam;
+      json?: TJSONBody | undefined;
+      formData?: TFormData | undefined;
+      headers?: THeaders | undefined;
+      query?: TQueryParams | undefined;
+      params?: TPathParam | undefined;
     }
   : never;
 
@@ -399,7 +415,7 @@ export type RouterSDK<
 > = {
   [TPathKey in TPath]: {
     [TMethod in Lowercase<TTypedRequest['method']>]: (
-      opts?: RouterSDKOpts<TTypedRequest, TTypedRequest['method']>,
+      opts?: RouterSDKOpts<TTypedRequest, TTypedRequest['method']> | undefined,
     ) => Promise<Exclude<TTypedResponse, undefined>>;
   };
 };
@@ -431,10 +447,10 @@ export type TypedRequestFromRouteSchemas<
         ? FromSchemaWithComponents<
             TComponents,
             TRouteSchemas['request']['formData']
-          > extends Record<string, FormDataEntryValue>
+          > extends Record<string, FormDataEntryValue | undefined>
           ? FromSchemaWithComponents<TComponents, TRouteSchemas['request']['formData']>
-          : Record<string, FormDataEntryValue>
-        : Record<string, FormDataEntryValue>,
+          : Record<string, FormDataEntryValue | undefined>
+        : Record<string, FormDataEntryValue | undefined>,
       TRouteSchemas['request'] extends { headers: JSONSchema }
         ? FromSchemaWithComponents<TComponents, TRouteSchemas['request']['headers']> extends Record<
             string,
@@ -463,7 +479,7 @@ export type TypedRequestFromRouteSchemas<
     >
   : TypedRequest<
       any,
-      Record<string, FormDataEntryValue>,
+      Record<string, FormDataEntryValue | undefined>,
       Record<string, string>,
       TMethod,
       Record<string, string | string[]>,
@@ -499,7 +515,7 @@ export type AddRouteWithTypesOpts<
   TPath extends string,
   TTypedRequest extends TypedRequest<
     any,
-    Record<string, FormDataEntryValue>,
+    Record<string, FormDataEntryValue | undefined>,
     Record<string, string>,
     TMethod,
     Record<string, string | string[]>,
@@ -507,11 +523,11 @@ export type AddRouteWithTypesOpts<
   >,
   TTypedResponse extends TypedResponse,
 > = {
-  operationId?: string;
-  description?: string;
-  method?: TMethod;
-  tags?: string[];
-  internal?: boolean;
+  operationId?: string | undefined;
+  description?: string | undefined;
+  method?: TMethod | undefined;
+  tags?: string[] | undefined;
+  internal?: boolean | undefined;
   path: TPath;
   handler:
     | RouteHandler<TServerContext, TTypedRequest, TTypedResponse>
@@ -553,7 +569,7 @@ export type RouterClient<TRouter extends Router<any, any, any>> = TRouter['__cli
 export type RouterInput<TRouter extends Router<any, any, any>> = {
   [TPath in keyof RouterClient<TRouter>]: {
     [TMethod in keyof RouterClient<TRouter>[TPath]]: RouterClient<TRouter>[TPath][TMethod] extends (
-      requestParams?: infer TRequestParams,
+      requestParams?: infer TRequestParams | undefined,
     ) => any
       ? Required<TRequestParams>
       : never;
diff --git a/packages/fets/src/utils.ts b/packages/fets/src/utils.ts
index 7df9df7de..26477cc1d 100644
--- a/packages/fets/src/utils.ts
+++ b/packages/fets/src/utils.ts
@@ -10,14 +10,14 @@ export interface PatternHandlersObj<TServerContext> {
 interface AddHandlerToMethodOpts<TServerContext> {
   // Operation related options
 
-  operationId?: string;
-  description?: string;
-  tags?: string[];
+  operationId?: string | undefined;
+  description?: string | undefined;
+  tags?: string[] | undefined;
   method: HTTPMethod;
   path: string;
-  schemas?: RouteSchemas;
+  schemas?: RouteSchemas | undefined;
   handlers: RouteHandler<TServerContext, TypedRequest, TypedResponse>[];
-  internal?: boolean;
+  internal?: boolean | undefined;
 
   // Router related options
   onRouteHooks: OnRouteHook<TServerContext>[];
@@ -59,7 +59,7 @@ function preparePatternHandlerObjByMethod<TServerContext>({
 
 declare global {
   interface URLPattern {
-    isPattern?: boolean;
+    isPattern?: boolean | undefined;
   }
 }
 
diff --git a/packages/fets/src/zod/types.ts b/packages/fets/src/zod/types.ts
index 2bf4c2f47..4d4c0464d 100644
--- a/packages/fets/src/zod/types.ts
+++ b/packages/fets/src/zod/types.ts
@@ -1,3 +1,4 @@
+import type { ZodSchema } from 'zod';
 import {
   HTTPMethod,
   TypedRequest,
@@ -6,31 +7,33 @@ import {
 } from '../typed-fetch';
 import { AddRouteWithTypesOpts, StatusCodeMap } from '../types';
 
-export type ZodType = { _output: any; safeParse(input: any): any };
+export type ZodType = ZodSchema; // { _output: any; safeParse(input: any): any };
 export type InferZodType<T extends ZodType> = T['_output'];
 
 export type RouteZodSchemas = {
-  request?: {
-    json?: ZodType;
-    formData?: ZodType;
-    headers?: ZodType;
-    params?: ZodType;
-    query?: ZodType;
-  };
-  responses?: StatusCodeMap<ZodType>;
+  request?:
+    | {
+        json?: ZodType | undefined;
+        formData?: ZodType | undefined;
+        headers?: ZodType | undefined;
+        params?: ZodType | undefined;
+        query?: ZodType | undefined;
+      }
+    | undefined;
+  responses?: StatusCodeMap<ZodType> | undefined;
 };
 
 export type TypedRequestFromRouteZodSchemas<
   TRouteZodSchemas extends RouteZodSchemas,
   TMethod extends HTTPMethod,
-> = TRouteZodSchemas extends { request: Required<RouteZodSchemas>['request'] }
+> = TRouteZodSchemas extends { request: RouteZodSchemas['request'] }
   ? TypedRequest<
       TRouteZodSchemas['request'] extends { json: ZodType }
         ? InferZodType<TRouteZodSchemas['request']['json']>
         : any,
       TRouteZodSchemas['request'] extends { formData: ZodType }
         ? InferZodType<TRouteZodSchemas['request']['formData']>
-        : Record<string, FormDataEntryValue>,
+        : Record<string, FormDataEntryValue | undefined>,
       TRouteZodSchemas['request'] extends { headers: ZodType }
         ? InferZodType<TRouteZodSchemas['request']['headers']>
         : Record<string, string>,
@@ -42,7 +45,12 @@ export type TypedRequestFromRouteZodSchemas<
         ? InferZodType<TRouteZodSchemas['request']['params']>
         : Record<string, any>
     >
-  : TypedRequest<any, Record<string, FormDataEntryValue>, Record<string, string>, TMethod>;
+  : TypedRequest<
+      any,
+      Record<string, FormDataEntryValue | undefined>,
+      Record<string, string>,
+      TMethod
+    >;
 
 export type TypedResponseFromRouteZodSchemas<TRouteZodSchemas extends RouteZodSchemas> =
   TRouteZodSchemas extends { responses: StatusCodeMap<ZodType> }
diff --git a/packages/fets/tests/router.spec.ts b/packages/fets/tests/router.spec.ts
index 3122500f5..6a0244a52 100644
--- a/packages/fets/tests/router.spec.ts
+++ b/packages/fets/tests/router.spec.ts
@@ -58,9 +58,14 @@ describe('Router', () => {
     expect(json.message).toBe('Hello John!');
   });
   it('should process multiple handlers for the same route', async () => {
-    const router = createRouter<{
-      message: string;
-    }>();
+    const router = createRouter<
+      {
+        message: string;
+      },
+      { schemas: {} },
+      {}
+    >();
+
     router.route({
       path: '/greetings',
       method: 'GET',
@@ -107,6 +112,7 @@ describe('Router', () => {
   });
   it('can pull route params from the basepath as well', async () => {
     const router = createRouter({ base: '/api' });
+
     router.route({
       path: '/greetings/:name',
       method: 'GET',
@@ -121,10 +127,11 @@ describe('Router', () => {
   });
 
   it('can handle nested routers', async () => {
-    const router = createRouter<any, {}>();
-    const nested = createRouter<any, {}>({
+    const router = createRouter<any, { schemas: {} }>();
+    const nested = createRouter<any, { schemas: {} }>({
       base: '/api',
     });
+
     nested.route({
       path: '/greetings/:name',
       method: 'GET',
diff --git a/tsconfig.json b/tsconfig.json
index 38bd46c3c..c15520dac 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -26,6 +26,7 @@
     "noUnusedParameters": true,
     "noFallthroughCasesInSwitch": true,
     "noPropertyAccessFromIndexSignature": false,
+    "exactOptionalPropertyTypes": true,
     "paths": {
       "@e2e/*": ["e2e/*/src/index.ts"],
       "fets": ["packages/fets/src/index.ts"]
diff --git a/yarn.lock b/yarn.lock
index 187ac0fdb..711054a44 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -11481,6 +11481,15 @@ resolve@^1.0.0, resolve@^1.1.7, resolve@^1.10.0, resolve@^1.10.1, resolve@^1.14.
     path-parse "^1.0.7"
     supports-preserve-symlinks-flag "^1.0.0"
 
+resolve@^1.22.3:
+  version "1.22.3"
+  resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.22.3.tgz#4b4055349ffb962600972da1fdc33c46a4eb3283"
+  integrity sha512-P8ur/gp/AmbEzjr729bZnLjXK5Z+4P0zhIJgBgzqRih7hL7BOukHGtSTA3ACMY467GRFz3duQsi0bDZdR7DKdw==
+  dependencies:
+    is-core-module "^2.12.0"
+    path-parse "^1.0.7"
+    supports-preserve-symlinks-flag "^1.0.0"
+
 resolve@^2.0.0-next.4:
   version "2.0.0-next.4"
   resolved "https://registry.yarnpkg.com/resolve/-/resolve-2.0.0-next.4.tgz#3d37a113d6429f496ec4752d2a2e58efb1fd4660"