diff --git a/packages/effect-fc/src/Result.ts b/packages/effect-fc/src/Result.ts
index 349434a..fe7bdf3 100644
--- a/packages/effect-fc/src/Result.ts
+++ b/packages/effect-fc/src/Result.ts
@@ -11,13 +11,11 @@ export type Result<A, E = never, P = never> = (
     | Final<A, E, P>
 )
 
-export type Final<A, E = never, P = never> = (
-    & (Success<A> | Failure<A, E>)
-    // biome-ignore lint/complexity/noBannedTypes: "{}" is relevant here
-    & ({} | WillFetch | WillRefresh | Refreshing<P>)
-)
+// biome-ignore lint/complexity/noBannedTypes: "{}" is relevant here
+export type Final<A, E = never, P = never> = (Success<A> | Failure<A, E>) & ({} | Flags<P>)
+export type Flags<P = never> = WillFetch | WillRefresh | Refreshing<P>
 
-export namespace Result {
+export declare namespace Result {
     export interface Prototype extends Pipeable.Pipeable, Equal.Equal {
         readonly [ResultTypeId]: ResultTypeId
     }
@@ -27,6 +25,10 @@ export namespace Result {
     export type Progress<R extends Result<any, any, any>> = [R] extends [Result<infer _A, infer _E, infer P>] ? P : never
 }
 
+export declare namespace Flags {
+    export type Keys = keyof WillFetch & WillRefresh & Refreshing<any>
+}
+
 export interface Initial extends Result.Prototype {
     readonly _tag: "Initial"
 }
@@ -47,16 +49,16 @@ export interface Failure<A, E = never> extends Result.Prototype {
     readonly previousSuccess: Option.Option<Success<A>>
 }
 
-export interface WillFetch extends Result.Prototype {
-    readonly willFetch: true
+export interface WillFetch {
+    readonly _flag: "WillFetch"
 }
 
-export interface WillRefresh extends Result.Prototype {
-    readonly willRefresh: true
+export interface WillRefresh {
+    readonly _flag: "WillRefresh"
 }
 
-export interface Refreshing<P = never> extends Result.Prototype {
-    readonly refreshing: true
+export interface Refreshing<P = never> {
+    readonly _flag: "Refreshing"
     readonly progress: P
 }
 
@@ -113,9 +115,9 @@ export const isInitial = (u: unknown): u is Initial => isResult(u) && u._tag ===
 export const isRunning = (u: unknown): u is Running<unknown> => isResult(u) && u._tag === "Running"
 export const isSuccess = (u: unknown): u is Success<unknown> => isResult(u) && u._tag === "Success"
 export const isFailure = (u: unknown): u is Failure<unknown, unknown> => isResult(u) && u._tag === "Failure"
-export const isWillFetch = (u: unknown): u is WillFetch => isResult(u) && Predicate.hasProperty(u, "willFetch")
-export const isWillRefresh = (u: unknown): u is WillRefresh => isResult(u) && Predicate.hasProperty(u, "willRefresh")
-export const isRefreshing = (u: unknown): u is Refreshing<unknown> => isResult(u) && Predicate.hasProperty(u, "refreshing")
+export const hasWillFetchFlag = (u: unknown): u is WillFetch => isResult(u) && Predicate.hasProperty(u, "_flag") && u._flag === "WillFetch"
+export const hasWillRefreshFlag = (u: unknown): u is WillRefresh => isResult(u) && Predicate.hasProperty(u, "_flag") && u._flag === "WillRefresh"
+export const hasRefreshingFlag = (u: unknown): u is Refreshing<unknown> => isResult(u) && Predicate.hasProperty(u, "_flag") && u._flag === "Refreshing"
 
 export const initial: {
     (): Initial
@@ -135,23 +137,23 @@ export const fail = <E, A = never>(
 
 export const willFetch = <R extends Initial | Final<any, any, any>>(
     result: R
-): Omit<R, keyof WillFetch> & WillFetch => Object.setPrototypeOf(
-    Object.assign({}, result, { willFetch: true }),
+): Omit<R, keyof Flags.Keys> & WillFetch => Object.setPrototypeOf(
+    Object.assign({}, result, { _flag: "WillFetch" }),
     Object.getPrototypeOf(result),
 )
 
 export const willRefresh = <R extends Final<any, any, any>>(
     result: R
-): Omit<R, keyof WillRefresh> & WillRefresh => Object.setPrototypeOf(
-    Object.assign({}, result, { willRefresh: true }),
+): Omit<R, keyof Flags.Keys> & WillRefresh => Object.setPrototypeOf(
+    Object.assign({}, result, { _flag: "WillRefresh" }),
     Object.getPrototypeOf(result),
 )
 
 export const refreshing = <R extends Final<any, any, any>, P = never>(
     result: R,
     progress?: P,
-): Omit<R, keyof Refreshing<Result.Progress<R>>> & Refreshing<P> => Object.setPrototypeOf(
-    Object.assign({}, result, { refreshing: true, progress }),
+): Omit<R, keyof Flags.Keys> & Refreshing<P> => Object.setPrototypeOf(
+    Object.assign({}, result, { _flag: "Refreshing", progress }),
     Object.getPrototypeOf(result),
 )
 
@@ -203,17 +205,17 @@ export const makeProgressLayer = <A, E, P = never>(): Layer.Layer<
     const state = yield* State<A, E, P>()
 
     return {
-        update: <E, R>(f: (previous: P) => Effect.Effect<P, E, R>) => Effect.Do.pipe(
+        update: <FE, FR>(f: (previous: P) => Effect.Effect<P, FE, FR>) => Effect.Do.pipe(
             Effect.bind("previous", () => Effect.andThen(state.get, previous =>
-                isRunning(previous) || isRefreshing(previous)
+                (isRunning(previous) || hasRefreshingFlag(previous))
                     ? Effect.succeed(previous)
                     : Effect.fail(new PreviousResultNotRunningNorRefreshing({ previous })),
             )),
             Effect.bind("progress", ({ previous }) => f(previous.progress)),
-            Effect.let("next", ({ previous, progress }) => Object.setPrototypeOf(
-                Object.assign({}, previous, { progress }),
-                Object.getPrototypeOf(previous),
-            )),
+            Effect.let("next", ({ previous, progress }) => isRunning(previous)
+                ? running(progress)
+                : refreshing(previous, progress) as Final<A, E, P> & Refreshing<P>
+            ),
             Effect.andThen(({ next }) => state.set(next)),
         ),
     }
@@ -223,19 +225,11 @@ export const makeProgressLayer = <A, E, P = never>(): Layer.Layer<
 export namespace unsafeForkEffect {
     export type OutputContext<A, E, R, P> = Exclude<R, State<A, E, P> | Progress<P> | Progress<never>>
 
-    export type Options<A, E, P> = {
-        readonly initial?: Result<A, E, P>
+    export interface Options<A, E, P> {
+        // biome-ignore lint/complexity/noBannedTypes: "{}" is relevant here
+        readonly initial?: (Initial | Success<A> | Failure<A, E>) & ({} | WillFetch | WillRefresh)
         readonly initialProgress?: P
-        readonly previous?: Final<A, E, P>
-    } & (
-        | {
-            readonly refresh: true
-            readonly previous: Final<A, E, P>
-        }
-        | {
-            readonly refresh?: false
-        }
-    )
+    }
 }
 
 export const unsafeForkEffect = <A, E, R, P = never>(
@@ -249,13 +243,17 @@ export const unsafeForkEffect = <A, E, R, P = never>(
     Effect.bind("ref", () => Ref.make(options?.initial ?? initial<A, E, P>())),
     Effect.bind("pubsub", () => PubSub.unbounded<Result<A, E, P>>()),
     Effect.bind("fiber", ({ ref, pubsub }) => Effect.forkScoped(State<A, E, P>().pipe(
-        Effect.andThen(state => state.set(options?.refresh
-            ? refreshing(options.previous, options?.initialProgress) as Result<A, E, P>
-            : running(options?.initialProgress)
+        Effect.andThen(state => state.set(
+            (isFinal(options?.initial) && hasWillRefreshFlag(options?.initial))
+                ? refreshing(options.initial, options?.initialProgress) as Result<A, E, P>
+                : running(options?.initialProgress)
         ).pipe(
             Effect.andThen(effect),
             Effect.onExit(exit => Effect.andThen(
-                state.set(fromExit(exit, (options?.previous && isSuccess(options.previous)) ? options.previous : undefined)),
+                state.set(fromExit(
+                    exit,
+                    isSuccess(options?.initial) ? options.initial : undefined),
+                ),
                 Effect.forkScoped(PubSub.shutdown(pubsub)),
             )),
         )),
@@ -286,7 +284,7 @@ export const unsafeForkEffect = <A, E, R, P = never>(
 export namespace forkEffect {
     export type InputContext<R, P> = R extends Progress<infer X> ? [X] extends [P] ? R : never : R
     export type OutputContext<A, E, R, P> = unsafeForkEffect.OutputContext<A, E, R, P>
-    export type Options<A, E, P> = unsafeForkEffect.Options<A, E, P>
+    export interface Options<A, E, P> extends unsafeForkEffect.Options<A, E, P> {}
 }
 
 export const forkEffect: {