rpc

Vovk.ts RPC client

Every controller procedure with HTTP decorator automatically gets typed client counterpart. vovk generate produces these client modules from segment schemas. Import path depends on config:

• Default setup only (composed client + JS template + default outDir: './node_modules/.vovk-client') → vovk-client npm package barrel re-exports emitted .js / .d.ts. Import from 'vovk-client'.
• Any other config — TS template, segmented client, custom source-tree outDir — vovk-client package not used. Generated files live in source tree, import through local path alias (e.g. '@/client', '@/client/<segment>').

Key identity: client module name = key used in initSegment's controllers map, regardless of import path.

// server
initSegment({ controllers: { UserRPC: UserController } });

// client (default setup shown — composed + JS template)
import { UserRPC } from 'vovk-client';
await UserRPC.getUser({ params: { id: '42' } });

Not UserControllerRPC. Not UserController. Whatever the key is.

Scope

Covers:

• vovk generate — when to run, what it produces.
• Composed vs segmented clients (composedClient / segmentedClient config).
• RPC method call shape.
• Fetcher customization via createFetcher + outputConfig.imports.fetcher, plus dynamically registered onSuccess / onError subscribers.
• Client-side validation (vovk-ajv integration, custom via createValidateOnClient).
• Error rethrow (HttpException, status/message/cause, HttpStatus.NULL).
• RPC method surface (.withDefaults, .getURL, .queryKey, .schema, .controllerSchema, .segmentSchema, .fullSchema, .isRPC).
• React Query / TanStack Query integration.
• openapi and schema payload imports.
• Cancellation — what's supported, what isn't.

Out of scope:

• Segment registration → segment skill.
• Procedure / handler / validation authoring → procedure skill.
• Streaming clients (async iteration, progressive()) → jsonlines skill.
• Python / Rust clients → python / rust skills.
• @operation metadata for OpenAPI → openapi skill.

Generating client

npx vovk generate

What it does:

• Reads .vovk-schema/**/*.json for every segment (nested segments live in subdirectories, e.g. .vovk-schema/customer/static.json).
• Emits generated code into configured outDir using selected fromTemplates preset.
• Default composed setup — fromTemplates: ['js'] + outDir: './node_modules/.vovk-client' — emits .js / .d.ts files; vovk-client npm package re-exports via export * from '../.vovk-client/index.js'. Only config where you import from 'vovk-client'.
• Alternate (recommended for pnpm) — fromTemplates: ['ts'] + outDir: './src/client' — emits .ts files directly into source tree. vovk-client package not used; users import from local alias like '@/client', own tsc handles files.
• Segmented client (any template) — always vendors per-segment modules into source tree (default ./src/client/<segment>). vovk-client not used regardless of template.

See "Import path depends on template + outDir" below for why these pair up.

vovk generate does NOT rebuild schemas from controller source. Schema emission = separate step: vovk dev runs alongside Next.js dev server, hits each segment's _schema_ endpoint (only available when NODE_ENV === 'development'), writes JSON into .vovk-schema/. vovk generate reads whatever's there.

Consequence: if backend changed and client looks stale, running vovk generate alone isn't enough — .vovk-schema/ hasn't been refreshed. Run npm run dev (starts vovk dev alongside next dev via concurrently) to re-emit schemas, then client regenerates from them.

When to run:

• Automatic: prebuild script installed by vovk init runs vovk generate before next build. During npm run dev, dev watcher refreshes .vovk-schema/ on backend changes, client regenerates.
• Explicit: before integration tests, after checking out branch, if client method appears missing ("compiled fine, why is UserRPC.createUser undefined?"). If method just written is missing, schema probably stale — restart npm run dev rather than re-running vovk generate.

Call shape

Same signature across every RPC method. Core options first, advanced below:

await ModuleRPC.methodName({
  // data
  params?: { ... },                 // path params — typed
  query?: { ... },                  // query string — typed
  body?: { ... } | FormData | ...,  // narrows by contentType — see "Body by content type"
  meta?: { [key: string]: any },    // serialized as x-meta header — see meta-isolation gotcha

  // transport
  apiRoot?: string,                 // override the generation-time default
  init?: RequestInit,               // headers, credentials, next.revalidate, etc. — see "init.signal is silently overwritten" below

  // validation
  disableClientValidation?: boolean,
  validateOnClient?: ...,           // per-call validator override

  // advanced
  interpretAs?: string,             // force response interpretation, e.g. 'application/jsonl' when server didn't set it
  transform?: (data, response) => any, // post-process the parsed response

  // plus any custom options declared via createFetcher<TOptions>({...}) — see Fetcher section
});

Return type = Promise of whatever procedure's output schema resolves to, or whatever transform returns if present. Override per call:

const user = await UserRPC.updateUser<SomeType>({ /* ... */ });

Body by content type

body's accepted type narrows to procedure's contentType: FormData for multipart/form-data, URLSearchParams or FormData for application/x-www-form-urlencoded, File / Blob / ArrayBuffer / Uint8Array for binary (image/*, video/*, */*). Schema-typed objects always accepted. Full matrix → procedure skill.

const form = new FormData();
form.append('file', file);
await UserRPC.uploadAvatar({ body: form }); // multipart/form-data procedure

Never hand-set Content-Type — fetcher derives it (multipart boundary included). Manual headers = usual HTTP 415 trigger.

apiRoot

apiRoot baked in at generation time: defaults to /${rootEntry} (rootEntry defaults to 'api', so default baked-in value = /api). When outputConfig.origin is set, bake produces full URL like http://localhost:3000/api. Per-call apiRoot fully replaces baked-in value for that call — config-level changes still require vovk generate.

In browser, relative /api resolves against page origin, so same call works from /dashboard and /settings. On server (Node, edge, integration tests) relative URLs don't resolve — pass full URL per call, bake one in via outputConfig.origin, or use withDefaults({ apiRoot }).

init

RequestInit forwarded to fetch — headers, credentials, mode, cache, Next.js-specific next: { revalidate: number } all pass through.

init.signal is silently overwritten. Internal fetcher creates own AbortController per call and overrides any signal you pass via init — packages/vovk/src/client/fetcher.ts:134-136. So passing init.signal does NOT abort request. For streaming endpoints, returned async iterable exposes .abortController — call .abort() on it. For non-streaming JSON responses, no public abort path exists today.

transform

Receives parsed response data and original Response. Return anything — including tuple if you want Response exposed to caller:

const [user, response] = await UserRPC.updateUser({
  /* ... */
  transform: (data, response) => [data, response] as const,
});
response satisfies Response;

interpretAs

Forces fetcher's content-type dispatch. Useful when server returns JSON Lines but omits content-type: application/jsonl (common behind some proxies or when streaming through Next.js): interpretAs: 'application/jsonl' makes client treat response as async iterable anyway.

Composed vs segmented client

Two top-level config keys — composedClient and segmentedClient — = independent toggles; enable one, the other, or both. Defaults differ because they target different workflows:

Key	Default enabled	Default fromTemplates	Default outDir	Default import
composedClient	true	['js']	./node_modules/.vovk-client	'vovk-client'
segmentedClient	false	['ts']	./src/client (or ./client if no src)	'@/client/<segment>'

Only composed client's default wires up vovk-client npm barrel (re-exports .js/.d.ts from node_modules/.vovk-client). Deviating from that exact combo — switching composed to TS template, source-tree outDir, or enabling segmented — bypasses vovk-client entirely; import from local alias.

// vovk.config.mjs
const config = {
  composedClient: {
    enabled: true, outDir: './node_modules/.vovk-client', fromTemplates: ['js'],  // all defaults
    prettifyClient: false,                    // true → run Prettier on emitted files
    includeSegments: ['public'],              // mutually exclusive with excludeSegments
  },
  segmentedClient: { enabled: true, outDir: './src/client', fromTemplates: ['ts'] },
};

Both keys can carry nested outputConfig overriding top-level for that specific output (e.g. segmented SDKs with different OpenAPI block).

Composed — one client module re-exports every RPC across every segment. Default case for most projects: import { UserRPC, PostRPC } from 'vovk-client'. With source-tree outDir (TS template), import from '@/client'.

Segmented — per-segment entries; importing @/client/admin keeps other segments out of bundle. Useful when segment boundaries map to independent deploys, versioning, or SDK consumers.

src/client/
├── root/     (index.ts, schema.ts, openapi.json, openapi.ts)
├── admin/    ...
└── customer/
    └── static/    (nested sub-segment)

import { UserRPC } from '@/client/customer';
import { AdminRPC } from '@/client/admin';

Import path depends on template + outDir (composed client)

Composed's import path follows from fromTemplates × outDir. vovk-client's barrel = export * from '../.vovk-client/index.js' — only resolves .js/.d.ts at default location.

fromTemplates	outDir	Import from	Notes
['js']	./node_modules/.vovk-client (default)	'vovk-client'	Default — only combo that actually uses vovk-client.
['ts']	source tree (e.g. ./src/client)	'@/client'	Recommended for pnpm; your tsc handles .ts directly.
['js']	custom source-tree path	local path	Valid but unusual.
['ts']	default node_modules/.vovk-client	broken	Barrel can't find .js to re-export.

Segmented has no equivalent table — always vendors per-segment modules into configured outDir; always import from local alias.

Why switch to TS template / source-tree outDir?

• pnpm — strict non-hoisted node_modules breaks vovk-client → .vovk-client sibling hop.
• Commit client — review, CI reproducibility, offline builds.
• TS integration — source maps, go-to-definition, type narrowing align with project's tsconfig.

Step-by-step setup → init skill.

Fetcher

Fetcher = client's core primitive — function (VovkFetcher<TFetcherOptions>) that takes request metadata (endpoint, method, schema, validator) and dispatches actual fetch. Default (import { fetcher } from 'vovk/fetcher') already handles JSON and JSON Lines, runs client-side validation, injects x-meta header, rethrows HttpException on errors.

Response-shape dispatch by content type:

• application/json → parsed JSON (typed as procedure's output schema).
• application/jsonl / application/jsonlines → disposable async iterable (see jsonlines skill).
• Other content types → raw Response object — caller reads text, binary, or streams it.

You extend default rather than rewriting via createFetcher:

// src/lib/fetcher.ts
import { createFetcher } from 'vovk';

export const fetcher = createFetcher<{
  // Custom per-call options — become typed fields on every RPC method call site.
  useAuth?: boolean;
  successMessage?: string;
}>({
  prepareRequestInit: async (init, { useAuth }) => ({
    ...init,
    headers: {
      ...init.headers,
      ...(useAuth ? { Authorization: `Bearer ${await getToken()}` } : {}),
    },
  }),
  transformResponse: (data, options, info) => data,     // optional
  onSuccess: (data, { successMessage }) => {
    if (successMessage) console.log(successMessage);
  },
  onError: (error, options) => { /* Sentry, retry hooks */ },
});

With that fetcher installed, callers get custom options inline:

await UserRPC.updateUser({
  params: { id: '42' },
  body: { /* ... */ },
  useAuth: true,
  successMessage: 'Updated!',
});

Hooks

All optional; options = typed TOptions you declared.

• prepareRequestInit(init, options) => RequestInit | Promise<RequestInit> — mutate RequestInit before fetch (headers, credentials, mode, cache, next.revalidate). Async OK — fetcher awaits return.
• transformResponse(data, options, info) — transform parsed response; info = { response, init, schema } gives access to raw Response, final RequestInit, procedure's VovkHandlerSchema (useful for reading operationObject).
• onSuccess(data, options) — observe successful responses (toasts, analytics).
• onError(error: HttpException, options) — observe failures. Both network errors and HTTP-status errors land here; error.statusCode === 0 (HttpStatus.NULL) = either transport failure or client-side validation rejection.

Event-style subscribers (dynamic)

onSuccess and onError can also be attached after fetcher is created. Useful when callback depends on state not available at creation time (React context value, Zustand store reference, lazily loaded logger). Each registration returns unsubscribe function; multiple subscribers run in order on every call:

// Somewhere in an app entry point (or a React effect, etc.)
import { fetcher } from '@/lib/fetcher';

const unsubSuccess = fetcher.onSuccess((data, { successMessage }) => {
  if (successMessage) toast.success(successMessage);
});

const unsubError = fetcher.onError((error) => {
  sentryReport(error);
});

// Later
unsubSuccess();
unsubError();

Prefer this pattern over baking toasts / store writes into createFetcher when dependency graph would otherwise force you to import UI-layer modules from transport layer.

Point config at fetcher

// vovk.config.mjs
/** @type {import('vovk').VovkConfig} */
const config = {
  outputConfig: {
    imports: {
      fetcher: './src/lib/fetcher',  // must export `fetcher` (named export)
    },
  },
};
export default config;

Generated client imports fetcher from that path. After editing config manually, run vovk generate.

Per-segment fetcher: different segments can use different fetchers (e.g., admin segment needs different auth than public one):

outputConfig: {
  imports: { fetcher: './src/lib/fetcher' },    // applied to all segments by default
  segments: {
    admin: {
      imports: { fetcher: './src/lib/adminFetcher' },  // overrides for admin
    },
  },
}

Common patterns:

• Auth token: inject Authorization header in prepareRequestInit, gated on useAuth custom option.
• Retry on 401: in onError, trigger token refresh; wrap call sites in retry helper.
• Telemetry: start timer in prepareRequestInit, report in onSuccess / onError.
• Success toasts: successMessage custom option + dynamic fetcher.onSuccess(...) subscriber that reads your toast library.

Keep fetcher focused on transport-layer concerns. Stateful things (request dedup, mutation queuing) belong in layer above.

Client-side validation

Install vovk-ajv, set outputConfig.imports.validateOnClient: 'vovk-ajv'. Generated client validates params / body / query against procedure's schema before HTTP call — invalid inputs throw HttpException(HttpStatus.NULL, ...) locally (i.e. statusCode === 0, same as transport failures) instead of round-tripping.

Roll your own validator via createValidateOnClient from vovk if Ajv isn't fit; point imports.validateOnClient at its module path:

// src/lib/validateOnClient.ts
import { createValidateOnClient, HttpException, HttpStatus } from 'vovk';

export const validateOnClient = createValidateOnClient({
  validate: async (input, schema, meta) => {
    // run your validator; on failure:
    // throw new HttpException(HttpStatus.NULL, 'Validation failed', { /* optional cause */ });
    return input;
  },
});

Skip per call:

await UserRPC.updateUser({
  params: { id: 'malformed' },
  disableClientValidation: true,
});

disableClientValidation also useful when debugging — bypass local pass to surface server-side validation error verbatim. Override with different validator per call via validateOnClient. Neither should be habit in production code paths.

Error handling

HttpException thrown on server rethrown on client with same statusCode, message, cause:

import { HttpException } from 'vovk';

try {
  await UserRPC.getUser({ params: { id: '42' } });
} catch (e) {
  if (e instanceof HttpException) {
    console.log(e.statusCode); // 404
    console.log(e.message);    // 'User not found'
    console.log(e.cause);      // any extra context passed server-side
  }
}

Bare Error on server → HttpException with status 500 on client. Network failures (no server, DNS error) and client-side validation failures both throw HttpException with status 0 (HttpStatus.NULL) — same instanceof HttpException check covers transport, validation, HTTP-status failures uniformly. Disambiguate by e.statusCode.

Types against RPC modules

Same inference helpers as controller-side (from vovk):

import type {
  VovkBody,
  VovkQuery,
  VovkParams,
  VovkInput,        // { params, query, body }
  VovkOutput,
  VovkIteration,    // per-chunk type for JSON Lines streams (see `jsonlines` skill)
  VovkYieldType,    // actual yielded type even when input isn't validated
  VovkReturnType,   // actual return type even when input isn't validated
} from 'vovk';
import { UserRPC } from 'vovk-client';

type Body   = VovkBody<typeof UserRPC.updateUser>;
type Query  = VovkQuery<typeof UserRPC.updateUser>;
type Params = VovkParams<typeof UserRPC.updateUser>;
type In     = VovkInput<typeof UserRPC.updateUser>;
type Out    = VovkOutput<typeof UserRPC.updateUser>;

All work identically against controller methods, RPC modules, imported mixin modules. VovkYieldType / VovkReturnType exist for cases where validation hasn't been declared on method (can't be used for self-references in services without triggering "implicit any" TypeScript errors).

RPC method surface

Every generated RPC method = more than just callable. Useful properties:

• .withDefaults(options) — returns new RPC module with given options deeply merged into every call. Handy for per-environment apiRoot, persistent init.headers, scoped fetcher.
• .getURL({ params, query, apiRoot }) — compute URL call would hit, without making request. Useful for <a href>, <form action>, or calling fetch directly.
• .queryKey(key?) — returns globally unique React Query / TanStack Query cache key. Shape: [segmentName, controllerPrefix, rpcModuleName, decoratorPath, httpMethod, ...key]. Optional key = array of extra scalars to disambiguate similar queries (typically same values passed in params / query).
• .apiRoot — baked-in apiRoot string.
• .schema (VovkHandlerSchema), .controllerSchema (VovkControllerSchema), .segmentSchema (VovkSegmentSchema), .fullSchema (VovkSchema) — raw schema objects. schema.validation.body etc. give per-input JSON Schema; schema.operationObject gives OpenAPI operation fragment; fullSchema.meta.config exposes config subset emitted into client (by default only libs and rootEntry, e.g. fullSchema.meta.config.libs.ajv).
• .isRPC: true — type guard (distinguishes RPC modules from raw controllers in tools like deriveTools).

const API = UserRPC.withDefaults({
  apiRoot: 'https://api.example.com/v1',
  init: { headers: { 'x-hello': 'world' } },
});
await API.getUser({ params: { id: '42' } });

const url = UserRPC.getUser.getURL({ params: { id: '42' } });
// => computed URL with params/query baked in

React Query / TanStack Query

import { useQuery } from '@tanstack/react-query';

// Extra key values disambiguate per-id queries:
useQuery({
  queryKey: UserRPC.getUser.queryKey(['42']),
  queryFn: () => UserRPC.getUser({ params: { id: '42' } }),
});

// Invalidate every query for this RPC module:
queryClient.invalidateQueries({
  queryKey: UserRPC.getUser.queryKey().slice(0, 3),
});

JSON Lines streams pair with TanStack's experimental_streamedQuery → see jsonlines skill.

Mutations reference method directly:

import { useMutation } from '@tanstack/react-query';

useMutation({ mutationFn: UserRPC.updateUser });

openapi and schema payloads from client

Composed (default JS setup — via vovk-client barrel):

import { openapi } from 'vovk-client/openapi';   // OpenAPI 3.x, derived from procedures + @operation metadata
import { schema }  from 'vovk-client/schema';    // Raw VovkSchema — all segments
import { schema }  from 'vovk-client';           // Same thing, re-exported from the root

Composed with TS template + source-tree outDir bypasses vovk-client entirely — import from local alias ('@/client/openapi', '@/client/schema').

Segmented (one OpenAPI + schema per segment — always via local alias, vovk-client not involved):

import { openapi } from '@/client/admin/openapi';
import { schema }  from '@/client/admin/schema';
import { schema }  from '@/client/admin';          // Same thing, re-exported from the segment root

Import path follows segmented client's outDir — if you changed segmentedClient.outDir to something else (e.g. ./sdk), path = @/sdk/admin/openapi etc.

See openapi skill for how spec is built.

Flows

"Fetch users on page load (client component)" — ensure procedure has HTTP decorator, then:

'use client';
import { UserRPC } from 'vovk-client';
useEffect(() => { UserRPC.list().then(setUsers); }, []);

"Add auth header to every RPC call" — createFetcher({ prepareRequestInit }), point outputConfig.imports.fetcher at it. Don't hand-roll per-call.

"My new procedure isn't on client" — restart npm run dev to re-emit .vovk-schema/. Still missing → check controller is registered in initSegment({ controllers }) and method has HTTP decorator.

"Call API from another Node process" — pass full URL: UserRPC.list({ apiRoot: 'https://api.example.com/api' }), or bake via UserRPC.withDefaults({ apiRoot }).

"Consume JSON Lines stream" — using stream = await StreamRPC.xxx(...); for await (const chunk of stream) { /* ... */ }. Full coverage → jsonlines skill.

Gotchas

• Import name mismatch: UserRPC (the controllers key), not UserControllerRPC. Most common "I can't import my RPC module" cause.
• Stale client: vovk generate regenerates from .vovk-schema/, only refreshed by running dev server. If user edited controller and ran vovk generate directly, output stale. Fix: npm run dev to re-emit schemas, then regenerate.
• No HTTP decorator = no RPC. Procedure without @get/@post/etc. is call-via-.fn() only; won't appear on client.
• Baked-in apiRoot defaults to /api (rootEntry: 'api' with no origin). Works in browser (resolves against page origin), fails outside (Node, edge, integration tests). Pass full URL per call, bake one in via outputConfig.origin, or use withDefaults({ apiRoot }).
• Fetcher path changes need regeneration. Editing fetcher file fine; changing its path in outputConfig.imports.fetcher requires vovk generate (or dev-watcher restart).
• disableClientValidation only skips client validation pass. Server-side validation still runs (unless procedure disables it, which should be rare).
• Client meta ≠ server req.vovk.meta(). meta option serialized as x-meta header and lands on server under xMetaHeader key — isolated from server-set trusted state (what authGuard writes via req.vovk.meta<AuthMeta>({ user }) is untouched by client). Treat client meta as advisory only; never use for auth or authorization decisions.