Apollo Client Changelog File — Apollo GraphQL

@apollo/client

4.2.10

Patch Changes

#13385 bfb674e Thanks @jerelmiller! - Fix accidental widening of the client.mutate return type when optimisticResponse was present.
#13382 365373e Thanks @jerelmiller! - Fix result types widened when a query's variables had constant types (e.g. TypedDocumentNode<Data, { type: "main" }>). This caused options such as returnPartialData or errorPolicy to be reported as their widened types (e.g. boolean, ErrorPolicy) instead of the value that was passed which returned the wrong data and dataState types.
#13382 365373e Thanks @jerelmiller! - Fix issue where unknown options were permitted by TypeScript when passed alongside a valid option to APIs with modern signatures.
#13383 5840f50 Thanks @jerelmiller! - Update the return type of refetch, fetchMore and useLazyQuery's execute function on the provided errorPolicy. Previously these APIs all used the default type which typed data as TData | undefined and error as ErrorLike | undefined.

4.2.9

Patch Changes

#13364 2f383e7 Thanks @atharv-sys32! - Fix a bug where GraphQL variable default values were not applied during cache reads when variables with defaults were explicitly set to undefined. This caused @include/@skip directives to throw "Invalid variable referenced" errors when the variable was passed as undefined instead of being omitted entirely.
#13367 2b39cc8 Thanks @jerelmiller! - Fix an issue where some @export queries would not react to cache updates when the fields keyed by exported variables were updated.

4.2.8

Patch Changes

#13349 501a33b Thanks @jerelmiller! - Prevent the setTimeout in connectToDevtools that shows the devtools suggestion from firing when the user agent does not match Chrome or Firefox. This check was previously done inside the setTimeout which meant the timer was scheduled for environments where we'd never show the message anyways. For test environments, this could cause flaky tests when that setTimeout outlived the tests and ran after any virtual DOM was torn down and removed.

4.2.7

Patch Changes

#13320 538c906 Thanks @jerelmiller! - Cleanup some unused internals. Please file an issue if you notice anything change.

4.2.6

Patch Changes

#13315 a406cc9 Thanks @fallintoplace! - Prevent relay multipart subscriptions from issuing a fetch request after serializing the request body fails.
#13307 abd0781 Thanks @wolfie! - Speed up cache writes by avoiding a full AST visit of every written field to detect @stream. The check now runs only when the result carries stream info, and only inspects the field node's own directives. As a result, fields that merely contain @stream on a nested field are no longer treated as streamed themselves and now overwrite existing lists like regular fields instead of merging chunk-wise.

4.2.5

Patch Changes

#13302 bb75dd3 Thanks @tpict! - Export KeyArgsFunction and RelayFieldPolicy types from public entrypoints.

4.2.4

Patch Changes

#13281 e4df809 Thanks @jerelmiller! - Fixes an issue where client.readFragment and client.readQuery ignored the optimistic option when passed in the options object.

4.2.3

Patch Changes

#13254 66e9dfc Thanks @jerelmiller! - Add support for graphql v17 as a valid peer dependency.

4.2.2

Patch Changes

#13184 c207b88 Thanks @audrius-savickas! - Preserve referential equality of masked data on refetch when the result is deeply equal to the previous result.

4.2.1

Patch Changes

#13248 062ffe3 Thanks @jerelmiller! - Fixes an issue where useLazyQuery would not apply a changed pollInterval between renders.

4.2.0

Minor Changes

#13132 f3ce805 Thanks @phryneas! - Introduce "classic" and "modern" method and hook signatures.

Apollo Client 4.2 introduces two signature styles for methods and hooks. All signatures previously present are now "classic" signatures, and a new set of "modern" signatures are added alongside them.

Classic signatures are the default and are identical to the signatures before Apollo Client 4.2, preserving backward compatibility. Classic signatures still work with manually specified TypeScript generics (e.g., useSuspenseQuery<MyData>(...)). However, manually specifying generics has been discouraged for a long time—instead, we recommend using TypedDocumentNode to automatically infer types, which provides more accurate results without any manual annotations.

Modern signatures automatically incorporate your declared defaultOptions into return types, providing more accurate types. Modern signatures infer types from the document node and do not support manually passing generic type arguments; TypeScript will produce a type error if you attempt to do so.

Methods and hooks automatically switch to modern signatures the moment any non-optional property is declared in DeclareDefaultOptions. The switch happens across all methods and hooks globally:
```
// apollo.d.ts
import "@apollo/client";
declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface WatchQuery {
        errorPolicy: "all"; // non-optional → modern signatures activated automatically
      }
    }
  }
}
```
Users can also manually switch to modern signatures without declaring any defaultOptions, for example when wanting accurate type inference without relying on global defaultOptions:
```
// apollo.d.ts
import "@apollo/client";
declare module "@apollo/client" {
  export interface TypeOverrides {
    signatureStyle: "modern";
  }
}
```
Users can do a global DeclareDefaultOptions type augmentation and then manually switch back to "classic" for migration purposes:
```
// apollo.d.ts
import "@apollo/client";
declare module "@apollo/client" {
  export interface TypeOverrides {
    signatureStyle: "classic";
  }
}
```
Note that this is not recommended for long-term use. When combined with DeclareDefaultOptions, switching back to classic results in the same incorrect types as before Apollo Client 4.2—methods and hooks will not reflect the defaultOptions you've declared.
#13130 dd12231 Thanks @jerelmiller! - Improve the accuracy of client.query return type to better detect the current errorPolicy. The data property is no longer nullable when the errorPolicy is none. This makes it possible to remove the undefined checks or optional chaining in most cases.

#13210 1f9a428 Thanks @jerelmiller! - Add support for automatic event-based refetching, such as window focus.

The RefetchEventManager class handles automatic refetches in response to events. Apollo Client provides built-in sources for window focus and network reconnect as windowFocusSource and onlineSource.

Event refetching is fully opt-in. Create and pass a RefetchEventManager instance to the ApolloClient constructor to activate the event listeners.

import {
  ApolloClient,
  InMemoryCache,
  RefetchEventManager,
  windowFocusSource,
  onlineSource,
} from "@apollo/client";

const client = new ApolloClient({
  link,
  cache: new InMemoryCache(),
  refetchEventManager: new RefetchEventManager({
    sources: {
      // Refetch when window is focused
      windowFocus: windowFocusSource,

      // Refetch when the user comes back online
      online: onlineSource,
    },
  }),
});

By default, all active queries refetch when the events fire. Queries can opt out per-event or disable all event refetches:

// Skip refetch on window focus for this query, but keep `online`
useQuery(QUERY, {
  refetchOn: { windowFocus: false },
});

// Disable all event-driven refetches for this query
useQuery(OTHER_QUERY, {
  refetchOn: false,
});

// Enable every event for this query, regardless of defaultOptions
useQuery(LIVE_DASHBOARD, {
  refetchOn: true,
});

// Dynamically enable or disable a refetch when the event fires
useQuery(LIVE_DASHBOARD, {
  refetchOn: ({ source, payload }) => {
    if (source === "windowFocus") {
      // payload is the data associated with the event
      return someCondition(payload);
    }

    return true;
  },
});

// Dynamically enable or disable a refetch for a specific event
useQuery(LIVE_DASHBOARD, {
  refetchOn: {
    windowFocus: ({ payload }) => {
      // payload is the data associated with the event
      return someCondition(payload);
    },
  },
});

To enable per-query opt-in rather than opt-out, set defaultOptions.watchQuery.refetchOn to false and enable it per-query instead.

const client = new ApolloClient({
  link,
  cache,
  refetchEventManager: new RefetchEventManager({
    sources: { windowFocus: windowFocusSource },
  }),
  defaultOptions: {
    watchQuery: { refetchOn: false },
  },
});

// Only this query refetches on window focus
useQuery(DASHBOARD_QUERY, { refetchOn: { windowFocus: true } });

When defaultOptions.watchQuery.refetchOn and per-query refetchOn options are provided, the objects are merged together.

Custom events

You can also add your own custom events that trigger refetches. Register your event name and payload type using TypeScript module augmentation, then provide a source function that returns an Observable. The source's emitted value becomes the event's payload.

import { Observable } from "@apollo/client";
import { filter } from "rxjs";
import { AppState, AppStateStatus, Platform } from "react-native";

declare module "@apollo/client" {
  interface RefetchEvents {
    reactNativeAppStatus: AppStateStatus;
  }
}

const refetchEventManager = new RefetchEventManager({
  sources: {
    reactNativeAppStatus: () => {
      return new Observable((observer) => {
        const subscription = AppState.addEventListener("change", (status) => {
          observer.next(status);
        });
        return () => subscription.remove();
      }).pipe(
        filter((status) => Platform.OS !== "web" && status === "active")
      );
    },
  },
});

// Disable per-query by setting the event to false
useQuery(QUERY, { refetchOn: { reactNativeAppStatus: false } });

Manually trigger an event refetch

Refetches can be triggered imperatively by calling emit with the event name and its payload (if any).

refetchEventManager.emit("reactNativeAppStatus", "active");

Sourceless events

A source that has no automatic detection logic but still wants imperative emit support can be declared as true. Type the event as void to omit the payload argument.

declare module "@apollo/client" {
  interface RefetchEvents {
    userTriggered: void;
  }
}

const refetchEventManager = new RefetchEventManager({
  sources: { userTriggered: true },
});

refetchEventManager.emit("userTriggered");

Note: Calling emit on an event without a registered source will log a warning and result in a no-op.

Custom handlers

When an event fires, the default handler calls client.refetchQueries({ include: "active" }) filtered by each query's refetchOn setting. You can override the handler for an event to add your own custom filtering. For example, to refetch all queries, including standby queries, define a handler for the event:

const refetchEventManager = new RefetchEventManager({
  // ...
  handlers: {
    userTriggered: ({ client, source, payload, matchesRefetchOn }) => {
      return client.refetchQueries({
        include: "all",
        onQueryUpdated: (observableQuery) => {
          return matchesRefetchOn(observableQuery);
        },
      });
    },
  },
});

Handlers must return either a RefetchQueriesResult or void. Returning void skips refetching for the event.

#13232 f1b541f Thanks @jerelmiller! - Version bump to rc.
#13206 08fccab Thanks @jerelmiller! - Extend the defaultOptions type-safety work to client.mutate and useMutation.

The errorPolicy option now flows through to the result types for mutations in the same way it already does for queries:
- ApolloClient.MutateResult<TData, TErrorPolicy> maps errorPolicy to the concrete shape of data and error:
  - "none" → { data: TData; error?: never }
  - "all" → { data: TData | undefined; error?: ErrorLike }
  - "ignore" → { data: TData | undefined; error?: never }
- client.mutate and useMutation pick up the declared defaultOptions.mutate.errorPolicy and the explicit errorPolicy on each call to narrow return types accordingly.
- useMutation.Result.error is narrowed to undefined when errorPolicy is "ignore", since client.mutate never resolves with an error in that case.
DeclareDefaultOptions.Mutate already accepted errorPolicy; the new behavior is that once you declare it, hook and method return types reflect it:
```
// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface Mutate {
        errorPolicy: "all";
      }
    }
  }
}
```
```
const result = await client.mutate({ mutation: MUTATION });
result.data;
//     ^? TData | undefined
result.error;
//     ^? ErrorLike | undefined
```
Setting errorPolicy on an individual call overrides the default for that call's return type.

#13222 b93c172 Thanks @jerelmiller! - Extend the defaultOptions type-safety work to preloadQuery (returned from createQueryPreloader). Defaults declared in DeclareDefaultOptions.WatchQuery now work with preloadQuery to ensure the PreloadedQueryRef's data states are correctly set.

// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface WatchQuery {
        errorPolicy: "all";
      }
    }
  }
}

const preloadQuery = createQueryPreloader(client);
const queryRef = preloadQuery(QUERY);
//    ^? PreloadedQueryRef<TData, TVariables, "complete" | "streaming" | "empty">

#13132 f3ce805 Thanks @phryneas! - Synchronize method and hook return types with defaultOptions.

Prior to this change, the following code snippet would always apply:
```
declare const MY_QUERY: TypedDocumentNode<TData, TVariables>;
const result1 = useSuspenseQuery(MY_QUERY);
result1.data;
//      ^? TData
const result2 = useSuspenseQuery(MY_QUERY, { errorPolicy: "all" });
result2.data;
//      ^? TData | undefined
```
While these types are generally correct, if you were to set errorPolicy: 'all' as a default option, the type of result.data for the first query would remain TData instead of changing to TData | undefined to match the runtime behavior.

We are now enforcing that certain defaultOptions types need to be registered globally. This means that if you want to use errorPolicy: 'all' as a default option for a query, you will need to register its type like this:
```
// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface WatchQuery {
        // possible global-registered values:
        // * `errorPolicy`
        // * `returnPartialData`
        errorPolicy: "all";
      }
      interface Query {
        // possible global-registered values:
        // * `errorPolicy`
      }
      interface Mutate {
        // possible global-registered values:
        // * `errorPolicy`
      }
    }
  }
}
```
Once this type declaration is in place, the type of result.data in the above example will correctly be changed to TData | undefined, reflecting the possibility that if an error occurs, data might be undefined. Manually specifying useSuspenseQuery(MY_QUERY, { errorPolicy: "none" }); changes result.data to TData to reflect the local override.

This change means that you will need to declare your default options types in order to use defaultOptions with ApolloClient, otherwise you will see a TypeScript error.

Without the type declaration, the following (previously valid) code will now error:
```
new ApolloClient({
  link: ApolloLink.empty(),
  cache: new InMemoryCache(),
  defaultOptions: {
    watchQuery: {
      // results in a type error:
      // Type '"all"' is not assignable to type '"A default option for watchQuery.errorPolicy must be declared in ApolloClient.DeclareDefaultOptions before usage. See https://www.apollographql.com/docs/react/data/typescript#declaring-default-options-for-type-safety."'.
      errorPolicy: "all",
    },
  },
});
```
If you are creating multiple instances of Apollo Client with conflicting default options and you cannot register a single defaultOptions value as a result, you can relax the constraints by declaring those options as union types covering all values used by all clients. The properties can be required (to enforce them in defaultOptions) or optional (if some constructor calls won't pass a value):
```
// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  export namespace ApolloClient {
    export namespace DeclareDefaultOptions {
      interface WatchQuery {
        errorPolicy?: "none" | "all" | "ignore";
        returnPartialData?: boolean;
      }
      interface Query {
        errorPolicy?: "none" | "all" | "ignore";
      }
      interface Mutate {
        errorPolicy?: "none" | "all" | "ignore";
      }
    }
  }
}
```
With this declaration, the ApolloClient constructor accepts any of those values in defaultOptions. The tradeoff is that hook and method return types become more generic. For example, calling useSuspenseQuery without an explicit errorPolicy will return a result typed as if all error policies are possible, since TypeScript can't know which specific value your instance uses at runtime.

Note that making a property optional (errorPolicy?:) is equivalent to adding the TypeScript default value ("none") to the union. So errorPolicy?: "all" | "ignore" has the same effect on return types as errorPolicy: "none" | "all" | "ignore", because TypeScript assumes the option could also be absent (i.e., "none").

You can also use a partial union that only lists the values you actually use. For example, if you only ever use "all" or "ignore", declare errorPolicy: "all" | "ignore" (required) to keep the union narrow and avoid unused values broadening your signatures unnecessarily.

Patch Changes

#13217 790f987 Thanks @jerelmiller! - Fix the deprecation for the classic signatures for function overloads that rely on type inference from a TypedDocumentNode. The deprecation now only applies to classic signatures that provide explicit type arguments to encourage the use of TypedDocumentNode.
#13166 0537d97 Thanks @jerelmiller! - Release changes in 4.1.5 and 4.1.6.
#13215 54c9eb7 Thanks @jerelmiller! - Ensure the options object for the useQuery, useSuspenseQuery, and useBackgroundQuery hooks provide proper IntelliSense suggestions.
#13229 9a7f65a Thanks @jerelmiller! - Fix refetchOn merging when defaultOptions.watchQuery.refetchOn is set to a non-object value (false, true, or a function) and the per-query refetchOn is an object. Previously the per-query object completely replaced the default so unspecified events fell back to "enabled" regardless of the default.

The defaultOptions value now applies to any event the per-query object does not explicitly configure:
- false - unspecified events stay disabled
- true - unspecified events refetch
- Callback function - the function is called for unspecified events to determine whether to refetch
```
const client = new ApolloClient({
  // ...
  defaultOptions: {
    watchQuery: {
      refetchOn: false,
    },
  },
});

// Only `windowFocus` refetches. Other events stay disabled per the default.
useQuery(QUERY, { refetchOn: { windowFocus: true } });
```
#13230 b25b659 Thanks @jerelmiller! - Add the ability to override the default event handler on RefetchEventManager. The default handler runs when no per-source handler is configured for an event. Provide a custom handler via the defaultHandler constructor option or the setDefaultEventHandler instance method.
```
new RefetchEventManager({
  defaultHandler: ({ client, matchesRefetchOn }) => {
    return client.refetchQueries({
      include: "all",
      onQueryUpdated: matchesRefetchOn,
    });
  },
});
```

4.2.0-rc.0

Minor Changes

#13232 f1b541f Thanks @jerelmiller! - Version bump to rc.

4.2.0-alpha.8

Patch Changes

#13229 9a7f65a Thanks @jerelmiller! - Fix refetchOn merging when defaultOptions.watchQuery.refetchOn is set to a non-object value (false, true, or a function) and the per-query refetchOn is an object. Previously the per-query object completely replaced the default so unspecified events fell back to "enabled" regardless of the default.

The defaultOptions value now applies to any event the per-query object does not explicitly configure:
- false - unspecified events stay disabled
- true - unspecified events refetch
- Callback function - the function is called for unspecified events to determine whether to refetch
```
const client = new ApolloClient({
  // ...
  defaultOptions: {
    watchQuery: {
      refetchOn: false,
    },
  },
});

// Only `windowFocus` refetches. Other events stay disabled per the default.
useQuery(QUERY, { refetchOn: { windowFocus: true } });
```
#13230 b25b659 Thanks @jerelmiller! - Add the ability to override the default event handler on RefetchEventManager. The default handler runs when no per-source handler is configured for an event. Provide a custom handler via the defaultHandler constructor option or the setDefaultEventHandler instance method.
```
new RefetchEventManager({
  defaultHandler: ({ client, matchesRefetchOn }) => {
    return client.refetchQueries({
      include: "all",
      onQueryUpdated: matchesRefetchOn,
    });
  },
});
```

4.2.0-alpha.7

Minor Changes

// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface WatchQuery {
        errorPolicy: "all";
      }
    }
  }
}

const preloadQuery = createQueryPreloader(client);
const queryRef = preloadQuery(QUERY);
//    ^? PreloadedQueryRef<TData, TVariables, "complete" | "streaming" | "empty">

4.2.0-alpha.6

Patch Changes

#13217 790f987 Thanks @jerelmiller! - Fix the deprecation for the classic signatures for function overloads that rely on type inference from a TypedDocumentNode. The deprecation now only applies to classic signatures that provide explicit type arguments to encourage the use of TypedDocumentNode.

4.2.0-alpha.5

Patch Changes

#13215 54c9eb7 Thanks @jerelmiller! - Ensure the options object for the useQuery, useSuspenseQuery, and useBackgroundQuery hooks provide proper IntelliSense suggestions.

4.2.0-alpha.4

Minor Changes

#13210 1f9a428 Thanks @jerelmiller! - Add support for automatic event-based refetching, such as window focus.

Event refetching is fully opt-in. Create and pass a RefetchEventManager instance to the ApolloClient constructor to activate the event listeners.

import {
  ApolloClient,
  InMemoryCache,
  RefetchEventManager,
  windowFocusSource,
  onlineSource,
} from "@apollo/client";

const client = new ApolloClient({
  link,
  cache: new InMemoryCache(),
  refetchEventManager: new RefetchEventManager({
    sources: {
      // Refetch when window is focused
      windowFocus: windowFocusSource,

      // Refetch when the user comes back online
      online: onlineSource,
    },
  }),
});

By default, all active queries refetch when the events fire. Queries can opt out per-event or disable all event refetches:

// Skip refetch on window focus for this query, but keep `online`
useQuery(QUERY, {
  refetchOn: { windowFocus: false },
});

// Disable all event-driven refetches for this query
useQuery(OTHER_QUERY, {
  refetchOn: false,
});

// Enable every event for this query, regardless of defaultOptions
useQuery(LIVE_DASHBOARD, {
  refetchOn: true,
});

// Dynamically enable or disable a refetch when the event fires
useQuery(LIVE_DASHBOARD, {
  refetchOn: ({ source, payload }) => {
    if (source === "windowFocus") {
      // payload is the data associated with the event
      return someCondition(payload);
    }

    return true;
  },
});

// Dynamically enable or disable a refetch for a specific event
useQuery(LIVE_DASHBOARD, {
  refetchOn: {
    windowFocus: ({ payload }) => {
      // payload is the data associated with the event
      return someCondition(payload);
    },
  },
});

To enable per-query opt-in rather than opt-out, set defaultOptions.watchQuery.refetchOn to false and enable it per-query instead.

const client = new ApolloClient({
  link,
  cache,
  refetchEventManager: new RefetchEventManager({
    sources: { windowFocus: windowFocusSource },
  }),
  defaultOptions: {
    watchQuery: { refetchOn: false },
  },
});

// Only this query refetches on window focus
useQuery(DASHBOARD_QUERY, { refetchOn: { windowFocus: true } });

When defaultOptions.watchQuery.refetchOn and per-query refetchOn options are provided, the objects are merged together.

Custom events

import { Observable } from "@apollo/client";
import { filter } from "rxjs";
import { AppState, AppStateStatus, Platform } from "react-native";

declare module "@apollo/client" {
  interface RefetchEvents {
    reactNativeAppStatus: AppStateStatus;
  }
}

const refetchEventManager = new RefetchEventManager({
  sources: {
    reactNativeAppStatus: () => {
      return new Observable((observer) => {
        const subscription = AppState.addEventListener("change", (status) => {
          observer.next(status);
        });
        return () => subscription.remove();
      }).pipe(
        filter((status) => Platform.OS !== "web" && status === "active")
      );
    },
  },
});

// Disable per-query by setting the event to false
useQuery(QUERY, { refetchOn: { reactNativeAppStatus: false } });

Manually trigger an event refetch

Refetches can be triggered imperatively by calling emit with the event name and its payload (if any).

refetchEventManager.emit("reactNativeAppStatus", "active");

Sourceless events

A source that has no automatic detection logic but still wants imperative emit support can be declared as true. Type the event as void to omit the payload argument.

declare module "@apollo/client" {
  interface RefetchEvents {
    userTriggered: void;
  }
}

const refetchEventManager = new RefetchEventManager({
  sources: { userTriggered: true },
});

refetchEventManager.emit("userTriggered");

Note: Calling emit on an event without a registered source will log a warning and result in a no-op.

Custom handlers

const refetchEventManager = new RefetchEventManager({
  // ...
  handlers: {
    userTriggered: ({ client, source, payload, matchesRefetchOn }) => {
      return client.refetchQueries({
        include: "all",
        onQueryUpdated: (observableQuery) => {
          return matchesRefetchOn(observableQuery);
        },
      });
    },
  },
});

Handlers must return either a RefetchQueriesResult or void. Returning void skips refetching for the event.

4.2.0-alpha.3

Minor Changes

#13206 08fccab Thanks @jerelmiller! - Extend the defaultOptions type-safety work to client.mutate and useMutation.

The errorPolicy option now flows through to the result types for mutations in the same way it already does for queries:
- ApolloClient.MutateResult<TData, TErrorPolicy> maps errorPolicy to the concrete shape of data and error:
  - "none" → { data: TData; error?: never }
  - "all" → { data: TData | undefined; error?: ErrorLike }
  - "ignore" → { data: TData | undefined; error?: never }
- client.mutate and useMutation pick up the declared defaultOptions.mutate.errorPolicy and the explicit errorPolicy on each call to narrow return types accordingly.
- useMutation.Result.error is narrowed to undefined when errorPolicy is "ignore", since client.mutate never resolves with an error in that case.
DeclareDefaultOptions.Mutate already accepted errorPolicy; the new behavior is that once you declare it, hook and method return types reflect it:
```
// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface Mutate {
        errorPolicy: "all";
      }
    }
  }
}
```
```
const result = await client.mutate({ mutation: MUTATION });
result.data;
//     ^? TData | undefined
result.error;
//     ^? ErrorLike | undefined
```
Setting errorPolicy on an individual call overrides the default for that call's return type.

4.2.0-alpha.2

@apollo/client

4.2.10

Patch Changes

#13385 bfb674e Thanks @jerelmiller! - Fix accidental widening of the client.mutate return type when optimisticResponse was present.
#13382 365373e Thanks @jerelmiller! - Fix result types widened when a query's variables had constant types (e.g. TypedDocumentNode<Data, { type: "main" }>). This caused options such as returnPartialData or errorPolicy to be reported as their widened types (e.g. boolean, ErrorPolicy) instead of the value that was passed which returned the wrong data and dataState types.
#13382 365373e Thanks @jerelmiller! - Fix issue where unknown options were permitted by TypeScript when passed alongside a valid option to APIs with modern signatures.
#13383 5840f50 Thanks @jerelmiller! - Update the return type of refetch, fetchMore and useLazyQuery's execute function on the provided errorPolicy. Previously these APIs all used the default type which typed data as TData | undefined and error as ErrorLike | undefined.

4.2.9

Patch Changes

#13364 2f383e7 Thanks @atharv-sys32! - Fix a bug where GraphQL variable default values were not applied during cache reads when variables with defaults were explicitly set to undefined. This caused @include/@skip directives to throw "Invalid variable referenced" errors when the variable was passed as undefined instead of being omitted entirely.
#13367 2b39cc8 Thanks @jerelmiller! - Fix an issue where some @export queries would not react to cache updates when the fields keyed by exported variables were updated.

4.2.8

Patch Changes

#13349 501a33b Thanks @jerelmiller! - Prevent the setTimeout in connectToDevtools that shows the devtools suggestion from firing when the user agent does not match Chrome or Firefox. This check was previously done inside the setTimeout which meant the timer was scheduled for environments where we'd never show the message anyways. For test environments, this could cause flaky tests when that setTimeout outlived the tests and ran after any virtual DOM was torn down and removed.

4.2.7

Patch Changes

#13320 538c906 Thanks @jerelmiller! - Cleanup some unused internals. Please file an issue if you notice anything change.

4.2.6

Patch Changes

#13315 a406cc9 Thanks @fallintoplace! - Prevent relay multipart subscriptions from issuing a fetch request after serializing the request body fails.
#13307 abd0781 Thanks @wolfie! - Speed up cache writes by avoiding a full AST visit of every written field to detect @stream. The check now runs only when the result carries stream info, and only inspects the field node's own directives. As a result, fields that merely contain @stream on a nested field are no longer treated as streamed themselves and now overwrite existing lists like regular fields instead of merging chunk-wise.

4.2.5

Patch Changes

#13302 bb75dd3 Thanks @tpict! - Export KeyArgsFunction and RelayFieldPolicy types from public entrypoints.

4.2.4

Patch Changes

#13281 e4df809 Thanks @jerelmiller! - Fixes an issue where client.readFragment and client.readQuery ignored the optimistic option when passed in the options object.

4.2.3

Patch Changes

#13254 66e9dfc Thanks @jerelmiller! - Add support for graphql v17 as a valid peer dependency.

4.2.2

Patch Changes

#13184 c207b88 Thanks @audrius-savickas! - Preserve referential equality of masked data on refetch when the result is deeply equal to the previous result.

4.2.1

Patch Changes

#13248 062ffe3 Thanks @jerelmiller! - Fixes an issue where useLazyQuery would not apply a changed pollInterval between renders.

4.2.0

Minor Changes

#13132 f3ce805 Thanks @phryneas! - Introduce "classic" and "modern" method and hook signatures.

Apollo Client 4.2 introduces two signature styles for methods and hooks. All signatures previously present are now "classic" signatures, and a new set of "modern" signatures are added alongside them.

Classic signatures are the default and are identical to the signatures before Apollo Client 4.2, preserving backward compatibility. Classic signatures still work with manually specified TypeScript generics (e.g., useSuspenseQuery<MyData>(...)). However, manually specifying generics has been discouraged for a long time—instead, we recommend using TypedDocumentNode to automatically infer types, which provides more accurate results without any manual annotations.

Modern signatures automatically incorporate your declared defaultOptions into return types, providing more accurate types. Modern signatures infer types from the document node and do not support manually passing generic type arguments; TypeScript will produce a type error if you attempt to do so.

Methods and hooks automatically switch to modern signatures the moment any non-optional property is declared in DeclareDefaultOptions. The switch happens across all methods and hooks globally:
```
// apollo.d.ts
import "@apollo/client";
declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface WatchQuery {
        errorPolicy: "all"; // non-optional → modern signatures activated automatically
      }
    }
  }
}
```
Users can also manually switch to modern signatures without declaring any defaultOptions, for example when wanting accurate type inference without relying on global defaultOptions:
```
// apollo.d.ts
import "@apollo/client";
declare module "@apollo/client" {
  export interface TypeOverrides {
    signatureStyle: "modern";
  }
}
```
Users can do a global DeclareDefaultOptions type augmentation and then manually switch back to "classic" for migration purposes:
```
// apollo.d.ts
import "@apollo/client";
declare module "@apollo/client" {
  export interface TypeOverrides {
    signatureStyle: "classic";
  }
}
```
Note that this is not recommended for long-term use. When combined with DeclareDefaultOptions, switching back to classic results in the same incorrect types as before Apollo Client 4.2—methods and hooks will not reflect the defaultOptions you've declared.
#13130 dd12231 Thanks @jerelmiller! - Improve the accuracy of client.query return type to better detect the current errorPolicy. The data property is no longer nullable when the errorPolicy is none. This makes it possible to remove the undefined checks or optional chaining in most cases.

#13210 1f9a428 Thanks @jerelmiller! - Add support for automatic event-based refetching, such as window focus.

Event refetching is fully opt-in. Create and pass a RefetchEventManager instance to the ApolloClient constructor to activate the event listeners.

import {
  ApolloClient,
  InMemoryCache,
  RefetchEventManager,
  windowFocusSource,
  onlineSource,
} from "@apollo/client";

const client = new ApolloClient({
  link,
  cache: new InMemoryCache(),
  refetchEventManager: new RefetchEventManager({
    sources: {
      // Refetch when window is focused
      windowFocus: windowFocusSource,

      // Refetch when the user comes back online
      online: onlineSource,
    },
  }),
});

By default, all active queries refetch when the events fire. Queries can opt out per-event or disable all event refetches:

// Skip refetch on window focus for this query, but keep `online`
useQuery(QUERY, {
  refetchOn: { windowFocus: false },
});

// Disable all event-driven refetches for this query
useQuery(OTHER_QUERY, {
  refetchOn: false,
});

// Enable every event for this query, regardless of defaultOptions
useQuery(LIVE_DASHBOARD, {
  refetchOn: true,
});

// Dynamically enable or disable a refetch when the event fires
useQuery(LIVE_DASHBOARD, {
  refetchOn: ({ source, payload }) => {
    if (source === "windowFocus") {
      // payload is the data associated with the event
      return someCondition(payload);
    }

    return true;
  },
});

// Dynamically enable or disable a refetch for a specific event
useQuery(LIVE_DASHBOARD, {
  refetchOn: {
    windowFocus: ({ payload }) => {
      // payload is the data associated with the event
      return someCondition(payload);
    },
  },
});

To enable per-query opt-in rather than opt-out, set defaultOptions.watchQuery.refetchOn to false and enable it per-query instead.

const client = new ApolloClient({
  link,
  cache,
  refetchEventManager: new RefetchEventManager({
    sources: { windowFocus: windowFocusSource },
  }),
  defaultOptions: {
    watchQuery: { refetchOn: false },
  },
});

// Only this query refetches on window focus
useQuery(DASHBOARD_QUERY, { refetchOn: { windowFocus: true } });

When defaultOptions.watchQuery.refetchOn and per-query refetchOn options are provided, the objects are merged together.

Custom events

import { Observable } from "@apollo/client";
import { filter } from "rxjs";
import { AppState, AppStateStatus, Platform } from "react-native";

declare module "@apollo/client" {
  interface RefetchEvents {
    reactNativeAppStatus: AppStateStatus;
  }
}

const refetchEventManager = new RefetchEventManager({
  sources: {
    reactNativeAppStatus: () => {
      return new Observable((observer) => {
        const subscription = AppState.addEventListener("change", (status) => {
          observer.next(status);
        });
        return () => subscription.remove();
      }).pipe(
        filter((status) => Platform.OS !== "web" && status === "active")
      );
    },
  },
});

// Disable per-query by setting the event to false
useQuery(QUERY, { refetchOn: { reactNativeAppStatus: false } });

Manually trigger an event refetch

Refetches can be triggered imperatively by calling emit with the event name and its payload (if any).

refetchEventManager.emit("reactNativeAppStatus", "active");

Sourceless events

A source that has no automatic detection logic but still wants imperative emit support can be declared as true. Type the event as void to omit the payload argument.

declare module "@apollo/client" {
  interface RefetchEvents {
    userTriggered: void;
  }
}

const refetchEventManager = new RefetchEventManager({
  sources: { userTriggered: true },
});

refetchEventManager.emit("userTriggered");

Note: Calling emit on an event without a registered source will log a warning and result in a no-op.

Custom handlers

const refetchEventManager = new RefetchEventManager({
  // ...
  handlers: {
    userTriggered: ({ client, source, payload, matchesRefetchOn }) => {
      return client.refetchQueries({
        include: "all",
        onQueryUpdated: (observableQuery) => {
          return matchesRefetchOn(observableQuery);
        },
      });
    },
  },
});

Handlers must return either a RefetchQueriesResult or void. Returning void skips refetching for the event.

#13232 f1b541f Thanks @jerelmiller! - Version bump to rc.
#13206 08fccab Thanks @jerelmiller! - Extend the defaultOptions type-safety work to client.mutate and useMutation.

The errorPolicy option now flows through to the result types for mutations in the same way it already does for queries:
- ApolloClient.MutateResult<TData, TErrorPolicy> maps errorPolicy to the concrete shape of data and error:
  - "none" → { data: TData; error?: never }
  - "all" → { data: TData | undefined; error?: ErrorLike }
  - "ignore" → { data: TData | undefined; error?: never }
- client.mutate and useMutation pick up the declared defaultOptions.mutate.errorPolicy and the explicit errorPolicy on each call to narrow return types accordingly.
- useMutation.Result.error is narrowed to undefined when errorPolicy is "ignore", since client.mutate never resolves with an error in that case.
DeclareDefaultOptions.Mutate already accepted errorPolicy; the new behavior is that once you declare it, hook and method return types reflect it:
```
// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface Mutate {
        errorPolicy: "all";
      }
    }
  }
}
```
```
const result = await client.mutate({ mutation: MUTATION });
result.data;
//     ^? TData | undefined
result.error;
//     ^? ErrorLike | undefined
```
Setting errorPolicy on an individual call overrides the default for that call's return type.

// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface WatchQuery {
        errorPolicy: "all";
      }
    }
  }
}

const preloadQuery = createQueryPreloader(client);
const queryRef = preloadQuery(QUERY);
//    ^? PreloadedQueryRef<TData, TVariables, "complete" | "streaming" | "empty">

#13132 f3ce805 Thanks @phryneas! - Synchronize method and hook return types with defaultOptions.

Prior to this change, the following code snippet would always apply:
```
declare const MY_QUERY: TypedDocumentNode<TData, TVariables>;
const result1 = useSuspenseQuery(MY_QUERY);
result1.data;
//      ^? TData
const result2 = useSuspenseQuery(MY_QUERY, { errorPolicy: "all" });
result2.data;
//      ^? TData | undefined
```
While these types are generally correct, if you were to set errorPolicy: 'all' as a default option, the type of result.data for the first query would remain TData instead of changing to TData | undefined to match the runtime behavior.

We are now enforcing that certain defaultOptions types need to be registered globally. This means that if you want to use errorPolicy: 'all' as a default option for a query, you will need to register its type like this:
```
// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface WatchQuery {
        // possible global-registered values:
        // * `errorPolicy`
        // * `returnPartialData`
        errorPolicy: "all";
      }
      interface Query {
        // possible global-registered values:
        // * `errorPolicy`
      }
      interface Mutate {
        // possible global-registered values:
        // * `errorPolicy`
      }
    }
  }
}
```
Once this type declaration is in place, the type of result.data in the above example will correctly be changed to TData | undefined, reflecting the possibility that if an error occurs, data might be undefined. Manually specifying useSuspenseQuery(MY_QUERY, { errorPolicy: "none" }); changes result.data to TData to reflect the local override.

This change means that you will need to declare your default options types in order to use defaultOptions with ApolloClient, otherwise you will see a TypeScript error.

Without the type declaration, the following (previously valid) code will now error:
```
new ApolloClient({
  link: ApolloLink.empty(),
  cache: new InMemoryCache(),
  defaultOptions: {
    watchQuery: {
      // results in a type error:
      // Type '"all"' is not assignable to type '"A default option for watchQuery.errorPolicy must be declared in ApolloClient.DeclareDefaultOptions before usage. See https://www.apollographql.com/docs/react/data/typescript#declaring-default-options-for-type-safety."'.
      errorPolicy: "all",
    },
  },
});
```
If you are creating multiple instances of Apollo Client with conflicting default options and you cannot register a single defaultOptions value as a result, you can relax the constraints by declaring those options as union types covering all values used by all clients. The properties can be required (to enforce them in defaultOptions) or optional (if some constructor calls won't pass a value):
```
// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  export namespace ApolloClient {
    export namespace DeclareDefaultOptions {
      interface WatchQuery {
        errorPolicy?: "none" | "all" | "ignore";
        returnPartialData?: boolean;
      }
      interface Query {
        errorPolicy?: "none" | "all" | "ignore";
      }
      interface Mutate {
        errorPolicy?: "none" | "all" | "ignore";
      }
    }
  }
}
```
With this declaration, the ApolloClient constructor accepts any of those values in defaultOptions. The tradeoff is that hook and method return types become more generic. For example, calling useSuspenseQuery without an explicit errorPolicy will return a result typed as if all error policies are possible, since TypeScript can't know which specific value your instance uses at runtime.

Note that making a property optional (errorPolicy?:) is equivalent to adding the TypeScript default value ("none") to the union. So errorPolicy?: "all" | "ignore" has the same effect on return types as errorPolicy: "none" | "all" | "ignore", because TypeScript assumes the option could also be absent (i.e., "none").

You can also use a partial union that only lists the values you actually use. For example, if you only ever use "all" or "ignore", declare errorPolicy: "all" | "ignore" (required) to keep the union narrow and avoid unused values broadening your signatures unnecessarily.

Patch Changes

#13217 790f987 Thanks @jerelmiller! - Fix the deprecation for the classic signatures for function overloads that rely on type inference from a TypedDocumentNode. The deprecation now only applies to classic signatures that provide explicit type arguments to encourage the use of TypedDocumentNode.
#13166 0537d97 Thanks @jerelmiller! - Release changes in 4.1.5 and 4.1.6.
#13215 54c9eb7 Thanks @jerelmiller! - Ensure the options object for the useQuery, useSuspenseQuery, and useBackgroundQuery hooks provide proper IntelliSense suggestions.
#13229 9a7f65a Thanks @jerelmiller! - Fix refetchOn merging when defaultOptions.watchQuery.refetchOn is set to a non-object value (false, true, or a function) and the per-query refetchOn is an object. Previously the per-query object completely replaced the default so unspecified events fell back to "enabled" regardless of the default.

The defaultOptions value now applies to any event the per-query object does not explicitly configure:
- false - unspecified events stay disabled
- true - unspecified events refetch
- Callback function - the function is called for unspecified events to determine whether to refetch
```
const client = new ApolloClient({
  // ...
  defaultOptions: {
    watchQuery: {
      refetchOn: false,
    },
  },
});

// Only `windowFocus` refetches. Other events stay disabled per the default.
useQuery(QUERY, { refetchOn: { windowFocus: true } });
```
#13230 b25b659 Thanks @jerelmiller! - Add the ability to override the default event handler on RefetchEventManager. The default handler runs when no per-source handler is configured for an event. Provide a custom handler via the defaultHandler constructor option or the setDefaultEventHandler instance method.
```
new RefetchEventManager({
  defaultHandler: ({ client, matchesRefetchOn }) => {
    return client.refetchQueries({
      include: "all",
      onQueryUpdated: matchesRefetchOn,
    });
  },
});
```

4.2.0-rc.0

Minor Changes

#13232 f1b541f Thanks @jerelmiller! - Version bump to rc.

4.2.0-alpha.8

Patch Changes

#13229 9a7f65a Thanks @jerelmiller! - Fix refetchOn merging when defaultOptions.watchQuery.refetchOn is set to a non-object value (false, true, or a function) and the per-query refetchOn is an object. Previously the per-query object completely replaced the default so unspecified events fell back to "enabled" regardless of the default.

The defaultOptions value now applies to any event the per-query object does not explicitly configure:
- false - unspecified events stay disabled
- true - unspecified events refetch
- Callback function - the function is called for unspecified events to determine whether to refetch
```
const client = new ApolloClient({
  // ...
  defaultOptions: {
    watchQuery: {
      refetchOn: false,
    },
  },
});

// Only `windowFocus` refetches. Other events stay disabled per the default.
useQuery(QUERY, { refetchOn: { windowFocus: true } });
```
#13230 b25b659 Thanks @jerelmiller! - Add the ability to override the default event handler on RefetchEventManager. The default handler runs when no per-source handler is configured for an event. Provide a custom handler via the defaultHandler constructor option or the setDefaultEventHandler instance method.
```
new RefetchEventManager({
  defaultHandler: ({ client, matchesRefetchOn }) => {
    return client.refetchQueries({
      include: "all",
      onQueryUpdated: matchesRefetchOn,
    });
  },
});
```

4.2.0-alpha.7

Minor Changes

// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface WatchQuery {
        errorPolicy: "all";
      }
    }
  }
}

const preloadQuery = createQueryPreloader(client);
const queryRef = preloadQuery(QUERY);
//    ^? PreloadedQueryRef<TData, TVariables, "complete" | "streaming" | "empty">

4.2.0-alpha.6

Patch Changes

#13217 790f987 Thanks @jerelmiller! - Fix the deprecation for the classic signatures for function overloads that rely on type inference from a TypedDocumentNode. The deprecation now only applies to classic signatures that provide explicit type arguments to encourage the use of TypedDocumentNode.

4.2.0-alpha.5

Patch Changes

#13215 54c9eb7 Thanks @jerelmiller! - Ensure the options object for the useQuery, useSuspenseQuery, and useBackgroundQuery hooks provide proper IntelliSense suggestions.

4.2.0-alpha.4

Minor Changes

#13210 1f9a428 Thanks @jerelmiller! - Add support for automatic event-based refetching, such as window focus.

Event refetching is fully opt-in. Create and pass a RefetchEventManager instance to the ApolloClient constructor to activate the event listeners.

import {
  ApolloClient,
  InMemoryCache,
  RefetchEventManager,
  windowFocusSource,
  onlineSource,
} from "@apollo/client";

const client = new ApolloClient({
  link,
  cache: new InMemoryCache(),
  refetchEventManager: new RefetchEventManager({
    sources: {
      // Refetch when window is focused
      windowFocus: windowFocusSource,

      // Refetch when the user comes back online
      online: onlineSource,
    },
  }),
});

By default, all active queries refetch when the events fire. Queries can opt out per-event or disable all event refetches:

// Skip refetch on window focus for this query, but keep `online`
useQuery(QUERY, {
  refetchOn: { windowFocus: false },
});

// Disable all event-driven refetches for this query
useQuery(OTHER_QUERY, {
  refetchOn: false,
});

// Enable every event for this query, regardless of defaultOptions
useQuery(LIVE_DASHBOARD, {
  refetchOn: true,
});

// Dynamically enable or disable a refetch when the event fires
useQuery(LIVE_DASHBOARD, {
  refetchOn: ({ source, payload }) => {
    if (source === "windowFocus") {
      // payload is the data associated with the event
      return someCondition(payload);
    }

    return true;
  },
});

// Dynamically enable or disable a refetch for a specific event
useQuery(LIVE_DASHBOARD, {
  refetchOn: {
    windowFocus: ({ payload }) => {
      // payload is the data associated with the event
      return someCondition(payload);
    },
  },
});

To enable per-query opt-in rather than opt-out, set defaultOptions.watchQuery.refetchOn to false and enable it per-query instead.

const client = new ApolloClient({
  link,
  cache,
  refetchEventManager: new RefetchEventManager({
    sources: { windowFocus: windowFocusSource },
  }),
  defaultOptions: {
    watchQuery: { refetchOn: false },
  },
});

// Only this query refetches on window focus
useQuery(DASHBOARD_QUERY, { refetchOn: { windowFocus: true } });

When defaultOptions.watchQuery.refetchOn and per-query refetchOn options are provided, the objects are merged together.

Custom events

import { Observable } from "@apollo/client";
import { filter } from "rxjs";
import { AppState, AppStateStatus, Platform } from "react-native";

declare module "@apollo/client" {
  interface RefetchEvents {
    reactNativeAppStatus: AppStateStatus;
  }
}

const refetchEventManager = new RefetchEventManager({
  sources: {
    reactNativeAppStatus: () => {
      return new Observable((observer) => {
        const subscription = AppState.addEventListener("change", (status) => {
          observer.next(status);
        });
        return () => subscription.remove();
      }).pipe(
        filter((status) => Platform.OS !== "web" && status === "active")
      );
    },
  },
});

// Disable per-query by setting the event to false
useQuery(QUERY, { refetchOn: { reactNativeAppStatus: false } });

Manually trigger an event refetch

Refetches can be triggered imperatively by calling emit with the event name and its payload (if any).

refetchEventManager.emit("reactNativeAppStatus", "active");

Sourceless events

A source that has no automatic detection logic but still wants imperative emit support can be declared as true. Type the event as void to omit the payload argument.

declare module "@apollo/client" {
  interface RefetchEvents {
    userTriggered: void;
  }
}

const refetchEventManager = new RefetchEventManager({
  sources: { userTriggered: true },
});

refetchEventManager.emit("userTriggered");

Note: Calling emit on an event without a registered source will log a warning and result in a no-op.

Custom handlers

const refetchEventManager = new RefetchEventManager({
  // ...
  handlers: {
    userTriggered: ({ client, source, payload, matchesRefetchOn }) => {
      return client.refetchQueries({
        include: "all",
        onQueryUpdated: (observableQuery) => {
          return matchesRefetchOn(observableQuery);
        },
      });
    },
  },
});

Handlers must return either a RefetchQueriesResult or void. Returning void skips refetching for the event.

4.2.0-alpha.3

Minor Changes

#13206 08fccab Thanks @jerelmiller! - Extend the defaultOptions type-safety work to client.mutate and useMutation.

The errorPolicy option now flows through to the result types for mutations in the same way it already does for queries:
- ApolloClient.MutateResult<TData, TErrorPolicy> maps errorPolicy to the concrete shape of data and error:
  - "none" → { data: TData; error?: never }
  - "all" → { data: TData | undefined; error?: ErrorLike }
  - "ignore" → { data: TData | undefined; error?: never }
- client.mutate and useMutation pick up the declared defaultOptions.mutate.errorPolicy and the explicit errorPolicy on each call to narrow return types accordingly.
- useMutation.Result.error is narrowed to undefined when errorPolicy is "ignore", since client.mutate never resolves with an error in that case.
DeclareDefaultOptions.Mutate already accepted errorPolicy; the new behavior is that once you declare it, hook and method return types reflect it:
```
// apollo.d.ts
import "@apollo/client";

declare module "@apollo/client" {
  namespace ApolloClient {
    namespace DeclareDefaultOptions {
      interface Mutate {
        errorPolicy: "all";
      }
    }
  }
}
```
```
const result = await client.mutate({ mutation: MUTATION });
result.data;
//     ^? TData | undefined
result.error;
//     ^? ErrorLike | undefined
```
Setting errorPolicy on an individual call overrides the default for that call's return type.