Server-side calls

import { function call<TDef extends ProcedureDef>(procedure: Procedure<TDef>, input: TDef["input"], opts: CallOptions<TDef>): Promise<TDef["output"]>call, function createRouterClient<TRouter extends AnyRouter>(router: TRouter, ...[opts]: {} extends RouterClientOptions<TRouter> ? [opts?: RouterClientOptions<TRouter>] : [opts: RouterClientOptions<TRouter>]): TrpcClient<TRouter, {}, DansonForm>createRouterClient } from '@trpc12/trpc/server';

const const caller: TrpcClient<{
    post: {
        byId: BuildProcedure<InputDef<RootDef<Context, {}>, ZodObject<{
            id: ZodString;
        }, $strip>>, "query", {
            output: Post;
            errors: TrpcError<"NOT_FOUND", {
                id: string;
            }>;
            services: never;
            unmapped: never;
        }>;
        list: BuildProcedure<RootDef<Context, {}>, "query", {
            output: Post[];
            errors: never;
            services: never;
            unmapped: never;
        }>;
        create: BuildProcedure<InputDef<With<RootDef<Context, {}>, {
            ctx: Context;
            ctxAdded: {
                ...;
            };
            inputOut: Unset;
            errors: TrpcError<...>;
            shorts: never;
        }>, ZodObject<...>>, "mutation", {
            ...;
        }>;
    };
}, {}, DansonForm>caller = createRouterClient<{
    post: {
        byId: BuildProcedure<InputDef<RootDef<Context, {}>, ZodObject<{
            id: ZodString;
        }, $strip>>, "query", {
            output: Post;
            errors: TrpcError<"NOT_FOUND", {
                id: string;
            }>;
            services: never;
            unmapped: never;
        }>;
        list: BuildProcedure<RootDef<Context, {}>, "query", {
            output: Post[];
            errors: never;
            services: never;
            unmapped: never;
        }>;
        create: BuildProcedure<InputDef<With<RootDef<Context, {}>, {
            ctx: Context;
            ctxAdded: {
                ...;
            };
            inputOut: Unset;
            errors: TrpcError<...>;
            shorts: never;
        }>, ZodObject<...>>, "mutation", {
            ...;
        }>;
    };
}>(router: {
    post: {
        byId: BuildProcedure<InputDef<RootDef<Context, {}>, ZodObject<{
            id: ZodString;
        }, $strip>>, "query", {
            output: Post;
            errors: TrpcError<"NOT_FOUND", {
                id: string;
            }>;
            services: never;
            unmapped: never;
        }>;
        list: BuildProcedure<RootDef<Context, {}>, "query", {
            output: Post[];
            errors: never;
            services: never;
            unmapped: never;
        }>;
        create: BuildProcedure<InputDef<With<RootDef<Context, {}>, {
            ctx: Context;
            ctxAdded: {
                ...;
            };
            inputOut: Unset;
            errors: TrpcError<...>;
            shorts: never;
        }>, ZodObject<...>>, "mutation", {
            ...;
        }>;
    };
}, opts: RouterClientOptions<...>): TrpcClient<...>createRouterClient(const appRouter: {
    post: {
        byId: BuildProcedure<InputDef<RootDef<Context, {}>, ZodObject<{
            id: ZodString;
        }, $strip>>, "query", {
            output: Post;
            errors: TrpcError<"NOT_FOUND", {
                id: string;
            }>;
            services: never;
            unmapped: never;
        }>;
        list: BuildProcedure<RootDef<Context, {}>, "query", {
            output: Post[];
            errors: never;
            services: never;
            unmapped: never;
        }>;
        create: BuildProcedure<InputDef<With<RootDef<Context, {}>, {
            ctx: Context;
            ctxAdded: {
                ...;
            };
            inputOut: Unset;
            errors: TrpcError<...>;
            shorts: never;
        }>, ZodObject<...>>, "mutation", {
            ...;
        }>;
    };
}appRouter, { ctx: {
    user: User | null;
} | (() => MaybePromise<{
    user: User | null;
}>)ctx: { user: User | nulluser } });
const const post: {
    id: string;
    title: string;
    author: string | null;
    createdAt: Date;
}post = await const caller: TrpcClient<{
    post: {
        byId: BuildProcedure<InputDef<RootDef<Context, {}>, ZodObject<{
            id: ZodString;
        }, $strip>>, "query", {
            output: Post;
            errors: TrpcError<"NOT_FOUND", {
                id: string;
            }>;
            services: never;
            unmapped: never;
        }>;
        list: BuildProcedure<RootDef<Context, {}>, "query", {
            output: Post[];
            errors: never;
            services: never;
            unmapped: never;
        }>;
        create: BuildProcedure<InputDef<With<RootDef<Context, {}>, {
            ctx: Context;
            ctxAdded: {
                ...;
            };
            inputOut: Unset;
            errors: TrpcError<...>;
            shorts: never;
        }>, ZodObject<...>>, "mutation", {
            ...;
        }>;
    };
}, {}, DansonForm>caller.post: ClientRouter<{
    byId: BuildProcedure<InputDef<RootDef<Context, {}>, ZodObject<{
        id: ZodString;
    }, $strip>>, "query", {
        output: Post;
        errors: TrpcError<"NOT_FOUND", {
            id: string;
        }>;
        services: never;
        unmapped: never;
    }>;
    list: BuildProcedure<RootDef<Context, {}>, "query", {
        output: Post[];
        errors: never;
        services: never;
        unmapped: never;
    }>;
    create: BuildProcedure<InputDef<With<RootDef<Context, {}>, {
        ctx: Context;
        ctxAdded: {
            ...;
        };
        inputOut: Unset;
        errors: TrpcError<...>;
        shorts: never;
    }>, ZodObject<...>>, "mutation", {
        ...;
    }>;
}, {}, DansonForm, {}>post.byId: {
    query(input: {
        id: string;
    }, opts?: CallOptions<{}> | undefined): TrpcPromise<{
        id: string;
        title: string;
        author: string | null;
        createdAt: Date;
    }, CallError<{
        type: "query";
        ctx: Context;
        meta: {};
        input: {
            id: string;
        };
        output: Post;
        errors: TrpcError<"NOT_FOUND", {
            id: string;
        }> | InputValidationError<{
            readonly code: "invalid_type";
            readonly expected: $ZodInvalidTypeExpected;
            readonly path: readonly [] | readonly ["id"];
            readonly message: string;
        } | {
            readonly code: "too_big";
            readonly origin: "number" | "int" | "bigint" | "date" | "string" | "array" | "set" | "file" | (string & {});
            ... 4 more ...;
            readonly message: string;
        } | ... 9 more ... | {
            ...;
        }>;
        services: never;
    }, DansonForm, never>>;
}byId.function query(input: {
    id: string;
}, opts?: CallOptions<{}> | undefined): TrpcPromise<{
    id: string;
    title: string;
    author: string | null;
    createdAt: Date;
}, CallError<{
    type: "query";
    ctx: Context;
    meta: {};
    input: {
        id: string;
    };
    output: Post;
    errors: TrpcError<"NOT_FOUND", {
        id: string;
    }> | InputValidationError<{
        readonly code: "invalid_type";
        readonly expected: $ZodInvalidTypeExpected;
        readonly path: readonly [] | readonly ["id"];
        readonly message: string;
    } | {
        readonly code: "too_big";
        readonly origin: "number" | "int" | "bigint" | "date" | "string" | "array" | "set" | "file" | (string & {});
        ... 4 more ...;
        readonly message: string;
    } | ... 9 more ... | {
        ...;
    }>;
    services: never;
}, DansonForm, never>>query({ id: stringid: '1' });

await call<{
    type: "query";
    ctx: Context;
    meta: {};
    input: {
        id: string;
    };
    output: Post;
    errors: TrpcError<"NOT_FOUND", {
        id: string;
    }> | InputValidationError<{
        readonly code: "invalid_type";
        readonly expected: $ZodInvalidTypeExpected;
        readonly path: readonly [] | readonly ["id"];
        readonly message: string;
    } | {
        readonly code: "too_big";
        readonly origin: "number" | "int" | "bigint" | "date" | "string" | "array" | "set" | "file" | (string & {});
        readonly maximum: string | number;
        readonly inclusive?: boolean | undefined;
        readonly exact?: boolean | undefined;
        readonly path: readonly [] | readonly [...];
        readonly message: string;
    } | ... 9 more ... | {
        ...;
    }>;
    services: never;
}>(procedure: Procedure<...>, input: {
    ...;
}, opts: CallOptions<...>): Promise<...>call(const appRouter: {
    post: {
        byId: BuildProcedure<InputDef<RootDef<Context, {}>, ZodObject<{
            id: ZodString;
        }, $strip>>, "query", {
            output: Post;
            errors: TrpcError<"NOT_FOUND", {
                id: string;
            }>;
            services: never;
            unmapped: never;
        }>;
        list: BuildProcedure<RootDef<Context, {}>, "query", {
            output: Post[];
            errors: never;
            services: never;
            unmapped: never;
        }>;
        create: BuildProcedure<InputDef<With<RootDef<Context, {}>, {
            ctx: Context;
            ctxAdded: {
                ...;
            };
            inputOut: Unset;
            errors: TrpcError<...>;
            shorts: never;
        }>, ZodObject<...>>, "mutation", {
            ...;
        }>;
    };
}appRouter.post: {
    byId: BuildProcedure<InputDef<RootDef<Context, {}>, ZodObject<{
        id: ZodString;
    }, $strip>>, "query", {
        output: Post;
        errors: TrpcError<"NOT_FOUND", {
            id: string;
        }>;
        services: never;
        unmapped: never;
    }>;
    list: BuildProcedure<RootDef<Context, {}>, "query", {
        output: Post[];
        errors: never;
        services: never;
        unmapped: never;
    }>;
    create: BuildProcedure<InputDef<With<RootDef<Context, {}>, {
        ctx: Context;
        ctxAdded: {
            ...;
        };
        inputOut: Unset;
        errors: TrpcError<...>;
        shorts: never;
    }>, ZodObject<...>>, "mutation", {
        ...;
    }>;
}post.byId: BuildProcedure<InputDef<RootDef<Context, {}>, ZodObject<...>>, "query", {
    ...;
}>byId, { id: stringid: '1' }, { ctx: Contextctx: { Context.user: User | nulluser } });
localLink({ router }) does the same inside a client's link chain. For React Server Actions, see Server Actions.
In-process calls have no HTTP request: you pass the ctx (or a function that makes it) yourself, and the handler's createContext doesn't run. To share request-reading code with the handler, keep it in a function of the request and build one: ctx: () => contextFor(HttpServerRequest.fromWeb(new Request(url, { headers }))).
In-process callers (createRouterClient, createTrpcRsc, localLink({ serializer: false })) pass values by reference, so they keep native types whatever the serializer.
Testing

Test in process with createRouterClient or localLink. @trpc12/trpc/internal/testing is a semi-public TestServer Effect layer for real-server tests (with @effect/vitest's it.layer); it has no compatibility promise.