diff --git a/packages/core/src/carrier.ts b/packages/core/src/carrier.ts
index d053234b4929..1879dc47f2d4 100644
--- a/packages/core/src/carrier.ts
+++ b/packages/core/src/carrier.ts
@@ -1,6 +1,7 @@
 import type { AsyncContextStack } from './asyncContext/stackStrategy';
 import type { AsyncContextStrategy } from './asyncContext/types';
-import type { Client, Integration, MetricsAggregator, Scope } from './types-hoist';
+import type { Client, MetricsAggregator, Scope } from './types-hoist';
+import type { Logger } from './utils-hoist/logger';
 import { SDK_VERSION } from './utils-hoist/version';
 import { GLOBAL_OBJ } from './utils-hoist/worldwide';
 
@@ -16,7 +17,7 @@ type VersionedCarrier = {
   version?: string;
 } & Record<Exclude<string, 'version'>, SentryCarrier>;
 
-interface SentryCarrier {
+export interface SentryCarrier {
   acs?: AsyncContextStrategy;
   stack?: AsyncContextStack;
 
@@ -24,13 +25,12 @@ interface SentryCarrier {
   defaultIsolationScope?: Scope;
   defaultCurrentScope?: Scope;
   globalMetricsAggregators?: WeakMap<Client, MetricsAggregator> | undefined;
+  logger?: Logger;
 
-  // TODO(v9): Remove these properties - they are no longer used and were left over in v8
-  integrations?: Integration[];
-  extensions?: {
-    // eslint-disable-next-line @typescript-eslint/ban-types
-    [key: string]: Function;
-  };
+  /** Overwrites TextEncoder used in `@sentry/core`, need for `react-native@0.73` and older */
+  encodePolyfill?: (input: string) => Uint8Array;
+  /** Overwrites TextDecoder used in `@sentry/core`, need for `react-native@0.73` and older */
+  decodePolyfill?: (input: Uint8Array) => string;
 }
 
 /**
@@ -57,3 +57,25 @@ export function getSentryCarrier(carrier: Carrier): SentryCarrier {
   // rather than what's set in .version so that "this" SDK always gets its carrier
   return (__SENTRY__[SDK_VERSION] = __SENTRY__[SDK_VERSION] || {});
 }
+
+/**
+ * Returns a global singleton contained in the global `__SENTRY__[]` object.
+ *
+ * If the singleton doesn't already exist in `__SENTRY__`, it will be created using the given factory
+ * function and added to the `__SENTRY__` object.
+ *
+ * @param name name of the global singleton on __SENTRY__
+ * @param creator creator Factory function to create the singleton if it doesn't already exist on `__SENTRY__`
+ * @param obj (Optional) The global object on which to look for `__SENTRY__`, if not `GLOBAL_OBJ`'s return value
+ * @returns the singleton
+ */
+export function getGlobalSingleton<Prop extends keyof SentryCarrier>(
+  name: Prop,
+  creator: () => NonNullable<SentryCarrier[Prop]>,
+  obj = GLOBAL_OBJ,
+): NonNullable<SentryCarrier[Prop]> {
+  const __SENTRY__ = (obj.__SENTRY__ = obj.__SENTRY__ || {});
+  const carrier = (__SENTRY__[SDK_VERSION] = __SENTRY__[SDK_VERSION] || {});
+  // Note: We do not want to set `carrier.version` here, as this may be called before any `init` is called, e.g. for the default scopes
+  return carrier[name] || (carrier[name] = creator());
+}
diff --git a/packages/core/src/currentScopes.ts b/packages/core/src/currentScopes.ts
index 85b148738467..b339a9f6d4cf 100644
--- a/packages/core/src/currentScopes.ts
+++ b/packages/core/src/currentScopes.ts
@@ -1,9 +1,9 @@
 import { getAsyncContextStrategy } from './asyncContext';
 import { getMainCarrier } from './carrier';
+import { getGlobalSingleton } from './carrier';
 import { Scope as ScopeClass } from './scope';
 import type { Client, Scope, TraceContext } from './types-hoist';
 import { dropUndefinedKeys } from './utils-hoist/object';
-import { getGlobalSingleton } from './utils-hoist/worldwide';
 
 /**
  * Get the currently active scope.
diff --git a/packages/core/src/defaultScopes.ts b/packages/core/src/defaultScopes.ts
index c9fb32c2049e..581eef68aff1 100644
--- a/packages/core/src/defaultScopes.ts
+++ b/packages/core/src/defaultScopes.ts
@@ -1,6 +1,6 @@
+import { getGlobalSingleton } from './carrier';
 import { Scope as ScopeClass } from './scope';
 import type { Scope } from './types-hoist';
-import { getGlobalSingleton } from './utils-hoist/worldwide';
 
 /** Get the default current scope. */
 export function getDefaultCurrentScope(): Scope {
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 77259d2434d4..efaa6a12a675 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -45,7 +45,7 @@ export {
   getDefaultIsolationScope,
 } from './defaultScopes';
 export { setAsyncContextStrategy } from './asyncContext';
-export { getMainCarrier } from './carrier';
+export { getGlobalSingleton, getMainCarrier } from './carrier';
 export { makeSession, closeSession, updateSession } from './session';
 // eslint-disable-next-line deprecation/deprecation
 export { SessionFlusher } from './sessionflusher';
diff --git a/packages/core/src/metrics/exports.ts b/packages/core/src/metrics/exports.ts
index 00f100bcaeb2..03d2ef90efe8 100644
--- a/packages/core/src/metrics/exports.ts
+++ b/packages/core/src/metrics/exports.ts
@@ -1,10 +1,10 @@
+import { getGlobalSingleton } from '../carrier';
 import { getClient } from '../currentScopes';
 import { DEBUG_BUILD } from '../debug-build';
 import { startSpanManual } from '../tracing';
 import type { Client, DurationUnit, MetricData, MetricsAggregator as MetricsAggregatorInterface } from '../types-hoist';
 import { logger } from '../utils-hoist/logger';
 import { timestampInSeconds } from '../utils-hoist/time';
-import { getGlobalSingleton } from '../utils-hoist/worldwide';
 import { handleCallbackErrors } from '../utils/handleCallbackErrors';
 import { getActiveSpan, getRootSpan, spanToJSON } from '../utils/spanUtils';
 import { COUNTER_METRIC_TYPE, DISTRIBUTION_METRIC_TYPE, GAUGE_METRIC_TYPE, SET_METRIC_TYPE } from './constants';
@@ -23,9 +23,9 @@ function getMetricsAggregatorForClient(
   client: Client,
   Aggregator: MetricsAggregatorConstructor,
 ): MetricsAggregatorInterface {
-  const globalMetricsAggregators = getGlobalSingleton<WeakMap<Client, MetricsAggregatorInterface>>(
+  const globalMetricsAggregators = getGlobalSingleton(
     'globalMetricsAggregators',
-    () => new WeakMap(),
+    () => new WeakMap<Client, MetricsAggregatorInterface>(),
   );
 
   const aggregator = globalMetricsAggregators.get(client);
diff --git a/packages/core/src/utils-hoist/envelope.ts b/packages/core/src/utils-hoist/envelope.ts
index be640b90ad4f..52fb7e175070 100644
--- a/packages/core/src/utils-hoist/envelope.ts
+++ b/packages/core/src/utils-hoist/envelope.ts
@@ -1,3 +1,4 @@
+import { getSentryCarrier } from '../carrier';
 import type {
   Attachment,
   AttachmentItem,
@@ -74,18 +75,16 @@ export function envelopeContainsItemType(envelope: Envelope, types: EnvelopeItem
  * Encode a string to UTF8 array.
  */
 function encodeUTF8(input: string): Uint8Array {
-  return GLOBAL_OBJ.__SENTRY__ && GLOBAL_OBJ.__SENTRY__.encodePolyfill
-    ? GLOBAL_OBJ.__SENTRY__.encodePolyfill(input)
-    : new TextEncoder().encode(input);
+  const carrier = getSentryCarrier(GLOBAL_OBJ);
+  return carrier.encodePolyfill ? carrier.encodePolyfill(input) : new TextEncoder().encode(input);
 }
 
 /**
  * Decode a UTF8 array to string.
  */
 function decodeUTF8(input: Uint8Array): string {
-  return GLOBAL_OBJ.__SENTRY__ && GLOBAL_OBJ.__SENTRY__.decodePolyfill
-    ? GLOBAL_OBJ.__SENTRY__.decodePolyfill(input)
-    : new TextDecoder().decode(input);
+  const carrier = getSentryCarrier(GLOBAL_OBJ);
+  return carrier.decodePolyfill ? carrier.decodePolyfill(input) : new TextDecoder().decode(input);
 }
 
 /**
diff --git a/packages/core/src/utils-hoist/index.ts b/packages/core/src/utils-hoist/index.ts
index b643f2e46d84..28a981be7bb4 100644
--- a/packages/core/src/utils-hoist/index.ts
+++ b/packages/core/src/utils-hoist/index.ts
@@ -5,7 +5,7 @@ export { getBreadcrumbLogLevelFromHttpStatusCode } from './breadcrumb-log-level'
 export { getComponentName, getDomElement, getLocationHref, htmlTreeAsString } from './browser';
 export { dsnFromString, dsnToString, makeDsn } from './dsn';
 export { SentryError } from './error';
-export { GLOBAL_OBJ, getGlobalSingleton } from './worldwide';
+export { GLOBAL_OBJ } from './worldwide';
 export type { InternalGlobal } from './worldwide';
 export { addConsoleInstrumentationHandler } from './instrument/console';
 export { addFetchEndInstrumentationHandler, addFetchInstrumentationHandler } from './instrument/fetch';
diff --git a/packages/core/src/utils-hoist/logger.ts b/packages/core/src/utils-hoist/logger.ts
index 90d306f11434..ee642d44582d 100644
--- a/packages/core/src/utils-hoist/logger.ts
+++ b/packages/core/src/utils-hoist/logger.ts
@@ -1,7 +1,7 @@
+import { getGlobalSingleton } from '../carrier';
 import type { ConsoleLevel } from '../types-hoist';
-
 import { DEBUG_BUILD } from './debug-build';
-import { GLOBAL_OBJ, getGlobalSingleton } from './worldwide';
+import { GLOBAL_OBJ } from './worldwide';
 
 /** Prefix for logging strings */
 const PREFIX = 'Sentry Logger ';
@@ -24,7 +24,7 @@ export const originalConsoleMethods: {
   [key in ConsoleLevel]?: (...args: unknown[]) => void;
 } = {};
 
-/** JSDoc */
+/** A Sentry Logger instance. */
 export interface Logger extends LoggerConsoleMethods {
   disable(): void;
   enable(): void;
diff --git a/packages/core/src/utils-hoist/worldwide.ts b/packages/core/src/utils-hoist/worldwide.ts
index 92018731ff4f..cd88db09942c 100644
--- a/packages/core/src/utils-hoist/worldwide.ts
+++ b/packages/core/src/utils-hoist/worldwide.ts
@@ -12,40 +12,8 @@
 
 /* eslint-disable @typescript-eslint/no-explicit-any */
 
-import type { Client, MetricsAggregator, Scope } from '../types-hoist';
-
+import type { Carrier } from '../carrier';
 import type { SdkSource } from './env';
-import type { logger } from './logger';
-import { SDK_VERSION } from './version';
-
-interface SentryCarrier {
-  acs?: any;
-  stack?: any;
-
-  globalScope?: Scope;
-  defaultIsolationScope?: Scope;
-  defaultCurrentScope?: Scope;
-  globalMetricsAggregators?: WeakMap<Client, MetricsAggregator> | undefined;
-  logger?: typeof logger;
-
-  /** Overwrites TextEncoder used in `@sentry/core`, need for `react-native@0.73` and older */
-  encodePolyfill?: (input: string) => Uint8Array;
-  /** Overwrites TextDecoder used in `@sentry/core`, need for `react-native@0.73` and older */
-  decodePolyfill?: (input: Uint8Array) => string;
-}
-
-// TODO(v9): Clean up or remove this type
-type BackwardsCompatibleSentryCarrier = SentryCarrier & {
-  // pre-v7 hub (replaced by .stack)
-  hub: any;
-  integrations?: any[];
-  logger: any;
-  extensions?: {
-    /** Extension methods for the hub, which are bound to the current Hub instance */
-    // eslint-disable-next-line @typescript-eslint/ban-types
-    [key: string]: Function;
-  };
-};
 
 /** Internal global with common properties and Sentry extensions  */
 export type InternalGlobal = {
@@ -73,9 +41,6 @@ export type InternalGlobal = {
    * file.
    */
   _sentryDebugIds?: Record<string, string>;
-  __SENTRY__: Record<Exclude<string, 'version'>, SentryCarrier> & {
-    version?: string;
-  } & BackwardsCompatibleSentryCarrier;
   /**
    * Raw module metadata that is injected by bundler plugins.
    *
@@ -83,25 +48,7 @@ export type InternalGlobal = {
    */
   _sentryModuleMetadata?: Record<string, any>;
   _sentryEsmLoaderHookRegistered?: boolean;
-};
+} & Carrier;
 
 /** Get's the global object for the current JavaScript runtime */
 export const GLOBAL_OBJ = globalThis as unknown as InternalGlobal;
-
-/**
- * Returns a global singleton contained in the global `__SENTRY__[]` object.
- *
- * If the singleton doesn't already exist in `__SENTRY__`, it will be created using the given factory
- * function and added to the `__SENTRY__` object.
- *
- * @param name name of the global singleton on __SENTRY__
- * @param creator creator Factory function to create the singleton if it doesn't already exist on `__SENTRY__`
- * @param obj (Optional) The global object on which to look for `__SENTRY__`, if not `GLOBAL_OBJ`'s return value
- * @returns the singleton
- */
-export function getGlobalSingleton<T>(name: keyof SentryCarrier, creator: () => T, obj?: unknown): T {
-  const gbl = (obj || GLOBAL_OBJ) as InternalGlobal;
-  const __SENTRY__ = (gbl.__SENTRY__ = gbl.__SENTRY__ || {});
-  const versionedCarrier = (__SENTRY__[SDK_VERSION] = __SENTRY__[SDK_VERSION] || {});
-  return versionedCarrier[name] || (versionedCarrier[name] = creator());
-}
diff --git a/packages/core/test/lib/hint.test.ts b/packages/core/test/lib/hint.test.ts
index d455a5bd5e44..f7fd5ff83ae4 100644
--- a/packages/core/test/lib/hint.test.ts
+++ b/packages/core/test/lib/hint.test.ts
@@ -14,7 +14,6 @@ describe('Hint', () => {
 
   afterEach(() => {
     jest.clearAllMocks();
-    // @ts-expect-error for testing
     delete GLOBAL_OBJ.__SENTRY__;
   });
 
diff --git a/packages/core/test/utils-hoist/envelope.test.ts b/packages/core/test/utils-hoist/envelope.test.ts
index ac1f17cfa1d9..6da22c1869a9 100644
--- a/packages/core/test/utils-hoist/envelope.test.ts
+++ b/packages/core/test/utils-hoist/envelope.test.ts
@@ -7,6 +7,7 @@ import {
   spanToJSON,
 } from '@sentry/core';
 import { SentrySpan } from '@sentry/core';
+import { getSentryCarrier } from '../../src/carrier';
 import {
   addItemToEnvelope,
   createEnvelope,
@@ -107,17 +108,18 @@ describe('envelope', () => {
       {
         name: 'with TextEncoder/Decoder polyfill',
         before: () => {
-          GLOBAL_OBJ.__SENTRY__ = {} as InternalGlobal['__SENTRY__'];
-          GLOBAL_OBJ.__SENTRY__.encodePolyfill = jest.fn<Uint8Array, [string]>((input: string) =>
+          GLOBAL_OBJ.__SENTRY__ = {};
+
+          getSentryCarrier(GLOBAL_OBJ).encodePolyfill = jest.fn<Uint8Array, [string]>((input: string) =>
             new TextEncoder().encode(input),
           );
-          GLOBAL_OBJ.__SENTRY__.decodePolyfill = jest.fn<string, [Uint8Array]>((input: Uint8Array) =>
+          getSentryCarrier(GLOBAL_OBJ).decodePolyfill = jest.fn<string, [Uint8Array]>((input: Uint8Array) =>
             new TextDecoder().decode(input),
           );
         },
         after: () => {
-          expect(GLOBAL_OBJ.__SENTRY__.encodePolyfill).toHaveBeenCalled();
-          expect(GLOBAL_OBJ.__SENTRY__.decodePolyfill).toHaveBeenCalled();
+          expect(getSentryCarrier(GLOBAL_OBJ).encodePolyfill).toHaveBeenCalled();
+          expect(getSentryCarrier(GLOBAL_OBJ).decodePolyfill).toHaveBeenCalled();
         },
       },
       {