diff --git a/documentation/docs/98-reference/.generated/client-errors.md b/documentation/docs/98-reference/.generated/client-errors.md
index 4fa8e1fc43..81179c06d6 100644
--- a/documentation/docs/98-reference/.generated/client-errors.md
+++ b/documentation/docs/98-reference/.generated/client-errors.md
@@ -143,7 +143,7 @@ This restriction only applies when using the `experimental.async` option, which
 ### fn_unavailable_on_client
 
 ```
-`%name%`(...) is unavailable on the client.
+`%name%`(...) is unavailable in the browser.
 ```
 
 ### fork_discarded
diff --git a/documentation/docs/98-reference/.generated/server-errors.md b/documentation/docs/98-reference/.generated/server-errors.md
index 101dc5db9e..8d7362c4c2 100644
--- a/documentation/docs/98-reference/.generated/server-errors.md
+++ b/documentation/docs/98-reference/.generated/server-errors.md
@@ -29,7 +29,7 @@ First set occurred at:
 %stack%
 ```
 
-This error occurs when using `hydratable` or `setHydratableValue` multiple times with the same key. To avoid this, you can combine `hydratable` with `cache`, or check whether the value has already been set with `hasHydratableValue`.
+This error occurs when using `hydratable` or `hydratable.set` multiple times with the same key. To avoid this, you can combine `hydratable` with `cache`, or check whether the value has already been set with `hydratable.has`.
 
 ```svelte
 <script>
diff --git a/packages/svelte/src/internal/client/errors.js b/packages/svelte/src/internal/client/errors.js
index d067ff95a3..e32256bda9 100644
--- a/packages/svelte/src/internal/client/errors.js
+++ b/packages/svelte/src/internal/client/errors.js
@@ -246,13 +246,13 @@ export function flush_sync_in_effect() {
 }
 
 /**
- * `%name%`(...) is unavailable on the client.
+ * `%name%`(...) is unavailable in the browser.
  * @param {string} name
  * @returns {never}
  */
 export function fn_unavailable_on_client(name) {
 	if (DEV) {
-		const error = new Error(`fn_unavailable_on_client\n\`${name}\`(...) is unavailable on the client.\nhttps://svelte.dev/e/fn_unavailable_on_client`);
+		const error = new Error(`fn_unavailable_on_client\n\`${name}\`(...) is unavailable in the browser.\nhttps://svelte.dev/e/fn_unavailable_on_client`);
 
 		error.name = 'Svelte error';
 
diff --git a/packages/svelte/src/internal/client/reactivity/resource.js b/packages/svelte/src/internal/client/reactivity/resource.js
index 739cc56021..f1db0a2d41 100644
--- a/packages/svelte/src/internal/client/reactivity/resource.js
+++ b/packages/svelte/src/internal/client/reactivity/resource.js
@@ -1,6 +1,6 @@
 /** @import { Source, Derived } from '#client' */
 /** @import { Resource as ResourceType } from '#shared' */
-import { state, derived, set, get, tick } from '../index.js';
+import { state, derived, set, get, tick, proxy } from '../index.js';
 import { deferred } from '../../shared/utils.js';
 import { async_mode_flag } from '../../flags/index.js';
 import * as e from '../errors.js';
@@ -49,10 +49,24 @@ class Resource {
 	/** {@type Source<any>} */
 	#error = state(undefined);
 
+	/** @type {Source<((oldValue: T) => T)[]>} */
+	#overrides = state(proxy([]));
+
+	/** @type {Derived<T | undefined>} */
+	#current = derived(() => {
+		return get(this.#ready)
+			? get(this.#overrides).reduce((v, r) => r(v), /** @type {T} */ (get(this.#raw)))
+			: undefined;
+	});
+
 	/** @type {Derived<Promise<T>['then']>} */
+	// @ts-ignore
 	#then = derived(() => {
+		// eslint-disable-next-line @typescript-eslint/no-unused-expressions
+		get(this.#overrides).length;
 		const p = get(this.#promise);
-		return (resolve, reject) => p.then(resolve, reject);
+		return (resolve, reject) =>
+			p.then(() => resolve?.(/** @type {T} */ (get(this.#current))), reject);
 	});
 
 	/**
@@ -126,7 +140,7 @@ class Resource {
 	}
 
 	get current() {
-		return get(this.#ready) ? get(this.#raw) : undefined;
+		return get(this.#current);
 	}
 
 	get error() {
@@ -166,6 +180,26 @@ class Resource {
 		set(this.#raw, value);
 		set(this.#promise, Promise.resolve(value));
 	};
+
+	/**
+	 * @param {(oldValue: T) => T} fn
+	 * @param {Promise<T>} promise
+	 */
+	withOverride(fn, promise) {
+		get(this.#overrides).push(fn);
+
+		const rollback = () => {
+			const i = get(this.#overrides).indexOf(fn);
+			if (i !== -1) {
+				get(this.#overrides).splice(i, 1);
+			}
+		};
+
+		promise.then((result) => {
+			this.set(result);
+			rollback();
+		}, rollback);
+	}
 }
 
 /** @returns {Promise<void>} */
diff --git a/packages/svelte/src/internal/server/reactivity/resource.js b/packages/svelte/src/internal/server/reactivity/resource.js
index c3f3fc0692..6d21e5f623 100644
--- a/packages/svelte/src/internal/server/reactivity/resource.js
+++ b/packages/svelte/src/internal/server/reactivity/resource.js
@@ -99,6 +99,10 @@ class Resource {
 		this.#current = value;
 		this.#promise = Promise.resolve();
 	};
+
+	withOverride = () => {
+		throw new Error('TODO Cannot override a resource on the server');
+	};
 }
 
 export function refreshAll() {
diff --git a/packages/svelte/src/internal/shared/types.d.ts b/packages/svelte/src/internal/shared/types.d.ts
index 4c5eeed601..57722bfd6f 100644
--- a/packages/svelte/src/internal/shared/types.d.ts
+++ b/packages/svelte/src/internal/shared/types.d.ts
@@ -40,6 +40,7 @@ export type Resource<T> = {
 	set: (value: Awaited<T>) => void;
 	loading: boolean;
 	error: any;
+	withOverride(fn: (oldValue: Awaited<T>) => Awaited<T>, promise: Promise<Awaited<T>>): void;
 } & (
 	| {
 			ready: false;
diff --git a/packages/svelte/types/index.d.ts b/packages/svelte/types/index.d.ts
index be91465c30..4998804413 100644
--- a/packages/svelte/types/index.d.ts
+++ b/packages/svelte/types/index.d.ts
@@ -2203,6 +2203,7 @@ declare module 'svelte/reactivity' {
 		set: (value: Awaited<T>) => void;
 		loading: boolean;
 		error: any;
+		withOverride(fn: (oldValue: Awaited<T>) => Awaited<T>, promise: Promise<Awaited<T>>): void;
 	} & (
 		| {
 				ready: false;
@@ -2215,8 +2216,6 @@ declare module 'svelte/reactivity' {
 	);
 
 	type GetRequestInit = Omit<RequestInit, 'method' | 'body'> & { method?: 'GET' };
-
-	type CacheEntry = { count: number; item: any };
 	/**
 	 * A reactive version of the built-in [`Date`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date) object.
 	 * Reading the date (whether with methods like `date.getTime()` or `date.toString()`, or via things like [`Intl.DateTimeFormat`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat))
@@ -2480,35 +2479,22 @@ declare module 'svelte/reactivity' {
 	 * @since 5.7.0
 	 */
 	export function createSubscriber(start: (update: () => void) => (() => void) | void): () => void;
-	export function resource<T>(fn: () => T): Resource<T>;
+	export class ReactiveCache<K = any, V = any> {
+		
+		register(key: K, fn: () => V): V;
+		[Symbol.iterator](): Generator<V, void, unknown>;
+		#private;
+	}
 	export function fetcher<TReturn>(url: string | URL, init?: GetRequestInit | undefined): Resource<TReturn>;
-	export function cache<TFn extends (...args: any[]) => any>(key: string, fn: TFn): ReturnType<TFn>;
+	export function resource<T>(fn: () => T): Resource<T>;
 
-	export class CacheObserver<T> extends BaseCacheObserver<T> {
-		constructor(prefix?: string);
-	}
+	export function refreshAll(): Promise<void>;
 	class ReactiveValue<T> {
 		
 		constructor(fn: () => T, onsubscribe: (update: () => void) => void);
 		get current(): T;
 		#private;
 	}
-	class BaseCacheObserver<T> implements ReadonlyMap<string, T> {
-		
-		constructor(get_cache: () => Map<string, CacheEntry>, prefix?: string | undefined);
-		
-		get(key: string): any;
-		
-		has(key: string): boolean;
-		get size(): number;
-		
-		forEach(cb: (item: T, key: string, map: ReadonlyMap<string, T>) => void): void;
-		entries(): Generator<[string, T], undefined, unknown>;
-		keys(): Generator<string, undefined, unknown>;
-		values(): Generator<T, undefined, unknown>;
-		[Symbol.iterator](): Generator<[string, T], undefined, unknown>;
-		#private;
-	}
 
 	export {};
 }