@lankajs/host

▸ module · Living inside another framework

The two places lanka meets Next, React Router, TanStack Start or Expo: one instance per unit of server work, and one first state per screen.

A library in the same box. The app imports and calls it; core does not know it exists.

Runs in: the browser, node and React Native — everywhere · @lankajs/host/server: node.

How to use it: GUIDE.md — the user guide, with examples. How to change it: SKILL.md.

Contents

• hydrateLankaVM — server data as a ViewModel's first state, in the browser
• runLankaRequest — SSR, RSC, loaders, server functions: an instance per request, carrying the caller's headers
• runLankaStatic — SSG and ISR: the same scope with identity refused

Why a package and not a flag on startLanka

node:async_hooks exists in node and nowhere else. Core is universal — the browser, node and React Native — and a single import of a node builtin inside it would put the filesystem's neighbour in every browser bundle that tree-shaking failed to reach.

So core publishes a SEAM instead: setLankaRuntimeResolver in lanka/internal, which replaces the question "which instance is active" with a strategy. Core ships no strategy and knows of none; this package installs the one that knows what a request is.

One mode per name, because they differ in what may cross in

runLankaRequest is for work with a user waiting — SSR, a server component, a loader, a server function, a server action, a streamed chunk — and it forwards that user's cookie and authorization into the API call. Without that, a signed-in page renders signed out and flips on hydration, silently.

runLankaStatic is for work with no user: a prerender, a static route, an ISR revalidation. It refuses headers, in the types and again at runtime, because output served to everybody must not carry one reader's identity. A boolean flag would have made that a default somebody flips; a second name makes it hard to write by accident.

What still may not cross to the server

ViewModels. A ViewModel is a zustand store created at module level and read through React hooks — one store per PROCESS, which on a server is one store shared by every user connected to it. The gateway layer has no such state, which is exactly why it is the layer that travels.

The handoff is data, not state: a loader returns what it fetched, the page passes it as a prop, and hydrateLankaVM makes it the ViewModel's first state in the browser.

No cache, deliberately

Next, React Router and TanStack Start each ship a request cache with revalidation. A second cache here would disagree with theirs on the first mutation, and the application would own the disagreement. A gateway returns data; whoever called it decides what to remember — revalidate, revalidateTag and their siblings stay the host's.

Repository map: ../../README.md