diff --git a/.changeset/tender-bikes-reply.md b/.changeset/tender-bikes-reply.md
new file mode 100644
index 0000000000..e2c35069cd
--- /dev/null
+++ b/.changeset/tender-bikes-reply.md
@@ -0,0 +1,5 @@
+---
+"effect": minor
+---
+
+change `Request` type parameters order from `Request<E, A>` to `Request<A, E = never>`
diff --git a/packages/effect/mod.sh b/packages/effect/mod.sh
index f2857cf163..cf0a298205 100755
--- a/packages/effect/mod.sh
+++ b/packages/effect/mod.sh
@@ -1,5 +1,5 @@
 #!/bin/bash
-dirs=(../effect/test)
+dirs=(../effect/src)
 for dir in ${dirs[@]};
 do
 echo Refactoring $dir
diff --git a/packages/effect/mod.ts b/packages/effect/mod.ts
index fdcdc3f5ce..c39bf14436 100644
--- a/packages/effect/mod.ts
+++ b/packages/effect/mod.ts
@@ -10,7 +10,8 @@ const enabled = {
   swapTakeParams: false,
   swapFiberParams: false,
   swapRuntimeFiberParams: false,
-  swapFiberSetParams: true,
+  swapFiberSetParams: false,
+  swapRequestParams: true,
   cleanupSTM: false,
   cleanupEffect: false,
   cleanupStream: false,
@@ -97,6 +98,7 @@ const swapTakeParams = swapParamsEA("Take")
 const swapFiberParams = swapParamsEA("Fiber")
 const swapRuntimeFiberParams = swapParamsEA("FiberRuntime")
 const swapFiberSetParams = swapParamsEA("FiberSet")
+const swapRequestParams = swapParamsEA("Request")
 
 const swapSTMParams = swapParamsREA("STM")
 const swapSTMGenParams = swapParamsREA("STMGen")
@@ -154,6 +156,9 @@ export default function transformer(file: cs.FileInfo, api: cs.API) {
     if (enabled.swapFiberSetParams) {
       swapFiberSetParams(ast)
     }
+    if (enabled.swapRequestParams) {
+      swapRequestParams(ast)
+    }
     if (enabled.cleanupEffect) {
       cleanupEffect(ast)
     }
diff --git a/packages/effect/src/KeyedPool.ts b/packages/effect/src/KeyedPool.ts
index 0d86b0c265..5fe529facd 100644
--- a/packages/effect/src/KeyedPool.ts
+++ b/packages/effect/src/KeyedPool.ts
@@ -21,7 +21,7 @@ export const KeyedPoolTypeId: unique symbol = internal.KeyedPoolTypeId
 export type KeyedPoolTypeId = typeof KeyedPoolTypeId
 
 /**
- * A `KeyedPool<K, E, A>` is a pool of `Pool`s of items of type `A`. Each pool
+ * A `KeyedPool<K, A, E>` is a pool of `Pool`s of items of type `A`. Each pool
  * in the `KeyedPool` is associated with a key of type `K`.
  *
  * @since 2.0.0
diff --git a/packages/effect/src/Request.ts b/packages/effect/src/Request.ts
index 8e8fc35487..a89090657c 100644
--- a/packages/effect/src/Request.ts
+++ b/packages/effect/src/Request.ts
@@ -29,13 +29,13 @@ export const RequestTypeId: unique symbol = internal.RequestTypeId
 export type RequestTypeId = typeof RequestTypeId
 
 /**
- * A `Request<E, A>` is a request from a data source for a value of type `A`
+ * A `Request<A, E>` is a request from a data source for a value of type `A`
  * that may fail with an `E`.
  *
  * @since 2.0.0
  * @category models
  */
-export interface Request<out E, out A> extends Request.Variance<E, A> {}
+export interface Request<out A, out E = never> extends Request.Variance<A, E> {}
 
 /**
  * @since 2.0.0
@@ -45,10 +45,10 @@ export declare namespace Request {
    * @since 2.0.0
    * @category models
    */
-  export interface Variance<out E, out A> {
+  export interface Variance<out A, out E> {
     readonly [RequestTypeId]: {
-      readonly _E: Types.Covariant<E>
       readonly _A: Types.Covariant<A>
+      readonly _E: Types.Covariant<E>
     }
   }
 
@@ -66,7 +66,7 @@ export declare namespace Request {
    * @since 2.0.0
    * @category type-level
    */
-  export type Error<T extends Request<any, any>> = [T] extends [Request<infer _E, infer _A>] ? _E : never
+  export type Error<T extends Request<any, any>> = [T] extends [Request<infer _A, infer _E>] ? _E : never
 
   /**
    * A utility type to extract the value type from a `Request`.
@@ -74,7 +74,7 @@ export declare namespace Request {
    * @since 2.0.0
    * @category type-level
    */
-  export type Success<T extends Request<any, any>> = [T] extends [Request<infer _E, infer _A>] ? _A : never
+  export type Success<T extends Request<any, any>> = [T] extends [Request<infer _A, infer _E>] ? _A : never
 
   /**
    * A utility type to extract the result type from a `Request`.
@@ -82,7 +82,7 @@ export declare namespace Request {
    * @since 2.0.0
    * @category type-level
    */
-  export type Result<T extends Request<any, any>> = T extends Request<infer E, infer A> ? Exit.Exit<A, E> : never
+  export type Result<T extends Request<any, any>> = T extends Request<infer A, infer E> ? Exit.Exit<A, E> : never
 
   /**
    * A utility type to extract the optional result type from a `Request`.
@@ -90,7 +90,7 @@ export declare namespace Request {
    * @since 2.0.0
    * @category type-level
    */
-  export type OptionalResult<T extends Request<any, any>> = T extends Request<infer E, infer A>
+  export type OptionalResult<T extends Request<any, any>> = T extends Request<infer A, infer E>
     ? Exit.Exit<Option.Option<A>, E>
     : never
 }
@@ -140,7 +140,7 @@ export const tagged: <R extends Request<any, any> & { _tag: string }>(
 export const Class: new<Error, Success, A extends Record<string, any>>(
   args: Types.Equals<Omit<A, keyof Request<unknown, unknown>>, {}> extends true ? void
     : { readonly [P in keyof A as P extends keyof Request<unknown, unknown> ? never : P]: A[P] }
-) => Request<Error, Success> & Readonly<A> = internal.Class as any
+) => Request<Success, Error> & Readonly<A> = internal.Class as any
 
 /**
  * Provides a Tagged constructor for a Request Class.
@@ -163,7 +163,7 @@ export const TaggedClass: <Tag extends string>(
 ) => new<Error, Success, A extends Record<string, any>>(
   args: Types.Equals<Omit<A, keyof Request<unknown, unknown>>, {}> extends true ? void
     : { readonly [P in keyof A as P extends "_tag" | keyof Request<unknown, unknown> ? never : P]: A[P] }
-) => Request<Error, Success> & Readonly<A> & { readonly _tag: Tag } = internal.TaggedClass as any
+) => Request<Success, Error> & Readonly<A> & { readonly _tag: Tag } = internal.TaggedClass as any
 
 /**
  * Complete a `Request` with the specified result.
@@ -303,8 +303,8 @@ export type EntryTypeId = typeof EntryTypeId
 export interface Entry<out R> extends Entry.Variance<R> {
   readonly request: R
   readonly result: Deferred<
-    [R] extends [Request<infer _E, infer _A>] ? _A : never,
-    [R] extends [Request<infer _E, infer _A>] ? _E : never
+    [R] extends [Request<infer _A, infer _E>] ? _A : never,
+    [R] extends [Request<infer _A, infer _E>] ? _E : never
   >
   readonly listeners: Listeners
   readonly ownerId: FiberId
diff --git a/packages/effect/src/RequestResolver.ts b/packages/effect/src/RequestResolver.ts
index 087cd11780..e8ebea96eb 100644
--- a/packages/effect/src/RequestResolver.ts
+++ b/packages/effect/src/RequestResolver.ts
@@ -219,7 +219,7 @@ export const eitherWith: {
  * @since 2.0.0
  * @category constructors
  */
-export const fromFunction: <A extends Request.Request<never, any>>(
+export const fromFunction: <A extends Request.Request<any>>(
   f: (request: A) => Request.Request.Success<A>
 ) => RequestResolver<A, never> = internal.fromFunction
 
@@ -231,7 +231,7 @@ export const fromFunction: <A extends Request.Request<never, any>>(
  * @since 2.0.0
  * @category constructors
  */
-export const fromFunctionBatched: <A extends Request.Request<never, any>>(
+export const fromFunctionBatched: <A extends Request.Request<any>>(
   f: (chunk: Array<A>) => Iterable<Request.Request.Success<A>>
 ) => RequestResolver<A, never> = internal.fromFunctionBatched
 
@@ -257,7 +257,7 @@ export const fromEffect: <R, A extends Request.Request<any, any>>(
 export const fromEffectTagged: <A extends Request.Request<any, any> & { readonly _tag: string }>() => <
   Fns extends {
     readonly [Tag in A["_tag"]]: [Extract<A, { readonly _tag: Tag }>] extends [infer Req]
-      ? Req extends Request.Request<infer ReqE, infer ReqA>
+      ? Req extends Request.Request<infer ReqA, infer ReqE>
         ? (requests: Array<Req>) => Effect.Effect<Iterable<ReqA>, ReqE, any>
       : never
       : never
diff --git a/packages/effect/src/internal/dataSource.ts b/packages/effect/src/internal/dataSource.ts
index 0bbeff6c37..85972230fc 100644
--- a/packages/effect/src/internal/dataSource.ts
+++ b/packages/effect/src/internal/dataSource.ts
@@ -181,7 +181,7 @@ export const eitherWith = dual<
   ))
 
 /** @internal */
-export const fromFunction = <A extends Request.Request<never, any>>(
+export const fromFunction = <A extends Request.Request<any>>(
   f: (request: A) => Request.Request.Success<A>
 ): RequestResolver.RequestResolver<A> =>
   makeBatched((requests: Array<A>) =>
@@ -192,7 +192,7 @@ export const fromFunction = <A extends Request.Request<never, any>>(
   ).identified("FromFunction", f)
 
 /** @internal */
-export const fromFunctionBatched = <A extends Request.Request<never, any>>(
+export const fromFunctionBatched = <A extends Request.Request<any>>(
   f: (chunk: Array<A>) => Iterable<Request.Request.Success<A>>
 ): RequestResolver.RequestResolver<A> =>
   makeBatched((as: Array<A>) =>
@@ -224,7 +224,7 @@ export const fromEffectTagged = <
 <
   Fns extends {
     readonly [Tag in A["_tag"]]: [Extract<A, { readonly _tag: Tag }>] extends [infer Req] ?
-      Req extends Request.Request<infer ReqE, infer ReqA> ?
+      Req extends Request.Request<infer ReqA, infer ReqE> ?
         (requests: Array<Req>) => Effect.Effect<Iterable<ReqA>, ReqE, any>
       : never
       : never
diff --git a/packages/effect/src/internal/request.ts b/packages/effect/src/internal/request.ts
index 321f0f81ac..c1966b3f1d 100644
--- a/packages/effect/src/internal/request.ts
+++ b/packages/effect/src/internal/request.ts
@@ -49,7 +49,7 @@ export const tagged = <R extends Request.Request<any, any> & { _tag: string }>(
 export const Class: new<Error, Success, A extends Record<string, any>>(
   args: Types.Equals<Omit<A, keyof Request.Request<unknown, unknown>>, {}> extends true ? void
     : { readonly [P in keyof A as P extends keyof Request.Request<unknown, unknown> ? never : P]: A[P] }
-) => Request.Request<Error, Success> & Readonly<A> = (function() {
+) => Request.Request<Success, Error> & Readonly<A> = (function() {
   function Class(this: any, args: any) {
     if (args) {
       Object.assign(this, args)
@@ -65,7 +65,7 @@ export const TaggedClass = <Tag extends string>(
 ): new<Error, Success, A extends Record<string, any>>(
   args: Types.Equals<Omit<A, keyof Request.Request<unknown, unknown>>, {}> extends true ? void
     : { readonly [P in keyof A as P extends "_tag" | keyof Request.Request<unknown, unknown> ? never : P]: A[P] }
-) => Request.Request<Error, Success> & Readonly<A> & { readonly _tag: Tag } => {
+) => Request.Request<Success, Error> & Readonly<A> & { readonly _tag: Tag } => {
   return class TaggedClass extends Class<any, any, any> {
     readonly _tag = tag
   } as any
diff --git a/packages/effect/test/Effect/query-nested.test.ts b/packages/effect/test/Effect/query-nested.test.ts
index 9de99bdcd0..ab9ca1bb94 100644
--- a/packages/effect/test/Effect/query-nested.test.ts
+++ b/packages/effect/test/Effect/query-nested.test.ts
@@ -38,27 +38,27 @@ interface ChildExtra {
   readonly extra: string
 }
 
-export interface GetAllParents extends Request.Request<never, ReadonlyArray<Parent>> {
+export interface GetAllParents extends Request.Request<ReadonlyArray<Parent>> {
   readonly _tag: "GetAllParents"
 }
 
 export const GetAllParents = Request.tagged<GetAllParents>("GetAllParents")
 
-export interface GetParentChildren extends Request.Request<never, ReadonlyArray<Child>> {
+export interface GetParentChildren extends Request.Request<ReadonlyArray<Child>> {
   readonly _tag: "GetParentChildren"
   readonly id: number
 }
 
 export const GetParentChildren = Request.tagged<GetParentChildren>("GetParentChildren")
 
-export interface GetChildInfo extends Request.Request<never, ChildInfo> {
+export interface GetChildInfo extends Request.Request<ChildInfo> {
   readonly _tag: "GetChildInfo"
   readonly id: number
 }
 
 export const GetChildInfo = Request.tagged<GetChildInfo>("GetChildInfo")
 
-export interface GetChildExtra extends Request.Request<never, ChildExtra> {
+export interface GetChildExtra extends Request.Request<ChildExtra> {
   readonly _tag: "GetChildExtra"
   readonly id: number
 }
diff --git a/packages/effect/test/Effect/query.test.ts b/packages/effect/test/Effect/query.test.ts
index f0f65b746e..27bf453900 100644
--- a/packages/effect/test/Effect/query.test.ts
+++ b/packages/effect/test/Effect/query.test.ts
@@ -36,7 +36,7 @@ export const userNames: ReadonlyMap<number, string> = new Map(
 
 export type UserRequest = GetAllIds | GetNameById
 
-export interface GetAllIds extends Request.Request<never, ReadonlyArray<number>> {
+export interface GetAllIds extends Request.Request<ReadonlyArray<number>> {
   readonly _tag: "GetAllIds"
 }
 
diff --git a/packages/rpc/src/Resolver.ts b/packages/rpc/src/Resolver.ts
index 25c1d001ae..20b783c3eb 100644
--- a/packages/rpc/src/Resolver.ts
+++ b/packages/rpc/src/Resolver.ts
@@ -18,7 +18,7 @@ export interface RpcResolver<R> extends Resolver.RequestResolver<RpcRequest, R>
  * @category models
  * @since 1.0.0
  */
-export interface RpcRequest extends Request.Request<RpcError, unknown> {
+export interface RpcRequest extends Request.Request<unknown, RpcError> {
   readonly payload: RpcRequest.Payload
   readonly hash: number
   readonly schema: RpcSchema.Any
diff --git a/packages/schema/src/Schema.ts b/packages/schema/src/Schema.ts
index a6a36c8a25..0b052d51e0 100644
--- a/packages/schema/src/Schema.ts
+++ b/packages/schema/src/Schema.ts
@@ -4697,7 +4697,7 @@ export const TaggedError = <Self>() =>
  * @since 1.0.0
  */
 export interface TaggedRequest<Tag extends string, R, IS, S, RR, IE, E, IA, A>
-  extends Request.Request<E, A>, Serializable.SerializableWithResult<R, IS, S, RR, IE, E, IA, A>
+  extends Request.Request<A, E>, Serializable.SerializableWithResult<R, IS, S, RR, IE, E, IA, A>
 {
   readonly _tag: Tag
 }