diff --git a/packages/react-relay/hooks.d.ts b/packages/react-relay/hooks.d.ts
index 608f03bb823a..70a9aa6dc2cd 100644
--- a/packages/react-relay/hooks.d.ts
+++ b/packages/react-relay/hooks.d.ts
@@ -80,7 +80,9 @@ export { useEntryPointLoader } from './relay-hooks/useEntryPointLoader';
 export { useFragment } from './relay-hooks/useFragment';
 export { useLazyLoadQuery } from './relay-hooks/useLazyLoadQuery';
 export { useMutation } from './relay-hooks/useMutation';
+export { useMutationAction_EXPERIMENTAL } from './relay-hooks/useMutationAction_EXPERIMENTAL';
 export { usePaginationFragment } from './relay-hooks/usePaginationFragment';
+export { usePrefetchableForwardPaginationFragment } from './relay-hooks/usePrefetchableForwardPaginationFragment';
 export { usePreloadedQuery } from './relay-hooks/usePreloadedQuery';
 export { useQueryLoader } from './relay-hooks/useQueryLoader';
 export { useRefetchableFragment } from './relay-hooks/useRefetchableFragment';
diff --git a/packages/react-relay/relay-hooks/RelayEnvironmentProvider.d.ts b/packages/react-relay/relay-hooks/RelayEnvironmentProvider.d.ts
index 3b7b34f60522..2a9591532b68 100644
--- a/packages/react-relay/relay-hooks/RelayEnvironmentProvider.d.ts
+++ b/packages/react-relay/relay-hooks/RelayEnvironmentProvider.d.ts
@@ -7,10 +7,12 @@
 
 import {ProviderProps, ReactElement, ReactNode} from 'react';
 import {IEnvironment, RelayContext} from 'relay-runtime';
+import {ActorIdentifier, IActorEnvironment} from 'relay-runtime/multi-actor-environment/index';
 
 export interface Props {
     children: ReactNode;
     environment: IEnvironment;
+    getEnvironmentForActor?: ((actorIdentifier: ActorIdentifier) => IActorEnvironment) | null | undefined;
 }
 
 export function RelayEnvironmentProvider(props: Props): ReactElement<ProviderProps<RelayContext>>;
diff --git a/packages/react-relay/relay-hooks/useMutationAction_EXPERIMENTAL.d.ts b/packages/react-relay/relay-hooks/useMutationAction_EXPERIMENTAL.d.ts
new file mode 100644
index 000000000000..725532c049cd
--- /dev/null
+++ b/packages/react-relay/relay-hooks/useMutationAction_EXPERIMENTAL.d.ts
@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {GraphQLTaggedNode, OperationType, VariablesOf} from 'relay-runtime';
+
+// Constrained to `OperationType` (response: unknown), not `MutationParameters`
+// (response: Record<string, unknown>): the Flow source places no constraint on
+// the response/`TData`, and the stricter bag rejects `@catch` mutations whose
+// response is a `Result<…>` union. This also matches the other modern hooks.
+export function useMutationAction_EXPERIMENTAL<TMutation extends OperationType>(
+    mutation: GraphQLTaggedNode,
+): (variables: VariablesOf<TMutation>) => Promise<TMutation['response']>;
diff --git a/packages/react-relay/relay-hooks/usePrefetchableForwardPaginationFragment.d.ts b/packages/react-relay/relay-hooks/usePrefetchableForwardPaginationFragment.d.ts
new file mode 100644
index 000000000000..ae5b7be2f57c
--- /dev/null
+++ b/packages/react-relay/relay-hooks/usePrefetchableForwardPaginationFragment.d.ts
@@ -0,0 +1,69 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {KeyType, KeyTypeData, RefetchFnDynamic} from '../ReactRelayTypes';
+import {LoadMoreFn} from './useLoadMoreFunction';
+import {GraphQLTaggedNode, OperationType, VariablesOf} from 'relay-runtime';
+
+export interface usePrefetchableForwardPaginationFragmentHookType<
+    TQuery extends OperationType,
+    TKey extends KeyType | null | undefined,
+    TFragmentData,
+    TEdgeData,
+> {
+    data: TFragmentData;
+    loadNext: LoadMoreFn<TQuery>;
+    hasNext: boolean;
+    isLoadingNext: boolean;
+    refetch: RefetchFnDynamic<TQuery, TKey>;
+    edges: TEdgeData;
+}
+
+export type GetExtraVariablesFn<TQuery extends OperationType, TFragmentData, TEdgeData> = (args: {
+    hasNext: boolean;
+    data: TFragmentData;
+    getServerEdges: () => TEdgeData;
+}) => Partial<VariablesOf<TQuery>>;
+
+export interface PrefetchingLoadMoreOptions<TQuery extends OperationType, TFragmentData, TEdgeData> {
+    UNSTABLE_extraVariables?:
+        | Partial<VariablesOf<TQuery>>
+        | GetExtraVariablesFn<TQuery, TFragmentData, TEdgeData>
+        | undefined;
+    onComplete?: ((error: Error | null) => void) | undefined;
+}
+
+export function usePrefetchableForwardPaginationFragment<
+    TQuery extends OperationType,
+    TKey extends KeyType,
+    TEdgeData,
+>(
+    fragmentInput: GraphQLTaggedNode,
+    parentFragmentRef: TKey,
+    bufferSize: number,
+    initialSize?: number | null | undefined,
+    prefetchingLoadMoreOptions?: PrefetchingLoadMoreOptions<TQuery, KeyTypeData<TKey>, TEdgeData>,
+    minimalFetchSize?: number,
+    disablePrefetching?: boolean,
+): usePrefetchableForwardPaginationFragmentHookType<TQuery, TKey, KeyTypeData<TKey>, TEdgeData>;
+export function usePrefetchableForwardPaginationFragment<
+    TQuery extends OperationType,
+    TKey extends KeyType,
+    TEdgeData,
+>(
+    fragmentInput: GraphQLTaggedNode,
+    parentFragmentRef: TKey | null | undefined,
+    bufferSize: number,
+    initialSize?: number | null | undefined,
+    prefetchingLoadMoreOptions?: PrefetchingLoadMoreOptions<
+        TQuery,
+        KeyTypeData<TKey> | null | undefined,
+        TEdgeData
+    >,
+    minimalFetchSize?: number,
+    disablePrefetching?: boolean,
+): usePrefetchableForwardPaginationFragmentHookType<TQuery, TKey | null, KeyTypeData<TKey> | null | undefined, TEdgeData>;
diff --git a/packages/relay-runtime/mutations/commitMutation.d.ts b/packages/relay-runtime/mutations/commitMutation.d.ts
index c61d5e12c98a..5a8299525744 100644
--- a/packages/relay-runtime/mutations/commitMutation.d.ts
+++ b/packages/relay-runtime/mutations/commitMutation.d.ts
@@ -8,13 +8,18 @@
 import {PayloadError, UploadableMap} from '../network/RelayNetworkTypes';
 import { GraphQLTaggedNode } from '../query/GraphQLTag';
 import {Environment, SelectorStoreUpdater} from '../store/RelayStoreTypes';
-import {CacheConfig, Disposable} from '../util/RelayRuntimeTypes';
+import {CacheConfig, Disposable, Variables} from '../util/RelayRuntimeTypes';
 import { DeclarativeMutationConfig } from './RelayDeclarativeMutationConfig';
 
+// Mirrors the Flow type `{response: {...}, variables: {...}, rawResponse?: {...}}`,
+// where `{...}` is Flow's inexact empty object ("any object"). `object` is the
+// faithful TS equivalent; `Record<string, unknown>` would be too strict — it
+// requires an implicit index signature, which `@catch` mutations (whose response
+// is a `Result<…>` union) and interface-typed responses do not have.
 export interface MutationParameters {
-    readonly response: Record<string, unknown>;
-    readonly variables: Record<string, unknown>;
-    readonly rawResponse?: Record<string, unknown> | undefined;
+    readonly response: object;
+    readonly variables: Variables;
+    readonly rawResponse?: object | undefined;
 }
 
 export interface MutationConfig<TOperation extends MutationParameters> {