API reference

v0.0.1 — minimal surface. Three exports. That's the API.

svelteRenderer(component, options)

Returns a Hono MiddlewareHandler that responds with an HTML document containing the SSR'd Svelte component, followed by a hydration script that mounts the matching client bundle.

Option	Type	Required	Notes
`hydrateAs`	`string`	yes	Matches a key in the bundles map passed to `attachSvelteRoutes`.
`props`	`Record<string, unknown>`	no	Same props used by SSR and hydration. JSON-serialized into the page.
`title`	`string`	no	Sets `<title>`.
`head`	`string`	no	Extra raw `<head>` HTML.
`bodyClass`	`string`	no	Class on the `<body>`.

attachSvelteRoutes(app, options)

Registers GET /__svelte/:id.{js,css} routes on the Hono app. Call once per app instance. Idempotent.

Option	Type	Notes
`bundles`	`Record<string, { js, css }>`	Keyed by `hydrateAs`. The build helper produces this.
`prefix`	`string`	Defaults to `"/__svelte"`. Override only on collision.

buildHonoSvelte(options)

From hono-svelte/build. Two esbuild passes — client + server — emitting a single bundled worker with all client bundles inlined as build-time string constants.

Option	Type	Notes
`workerEntry`	`string`	Path to your Worker entry (TS or JS).
`outDir`	`string`	Output dir. `worker.bundled.mjs` lands here.
`components`	`Record<string, string>`	id → path to `.svelte` file. id matches `hydrateAs`.
`target`	`string`	Defaults `"es2022"`.
`dev`	`boolean`	Source maps + no minify. Defaults `false`.

The constant the build injects

Inside your worker source:

declare const __HONO_SVELTE_BUNDLES__: Record<string, { js: string; css: string }>;

esbuild's define replaces this identifier with a JSON object at build time. Pass it directly to attachSvelteRoutes.

Constraints

Build-time compile. No eval at runtime — Workers prohibits it. See Why.
One root per page. SSR mount target is #hono-svelte-root.
Non-streaming HTML. Full document in one Response. Workers fan out at the edge; streaming is rarely the right primitive at this size.
Hono owns routing. No file-system router, no load functions, no +layout.svelte. Use Hono. That's the point.