Replace Polka in adapter-node with a maintained web server

[Mnwa]

Describe the problem

@sveltejs/adapter-node builds on top of Polka as its underlying web server. Polka appears to have stalled as a project, which is a concern for a server that powers production SvelteKit deployments.

Evidence of the maintenance gap:

• The latest release on npm is 0.5.2, published 2024-09-19 — roughly 21 months ago with no new release since.
• There are currently ~24 open issues and 8 open pull requests on the repo, several of which have sat untouched for years (e.g. fix: add missing spaces in code examples lukeed/polka#79, Fix TypeError in strict mode lukeed/polka#86, feat(polka): export class Polka to allow customizations lukeed/polka#103).
• Open PRs include fixes and type improvements relevant to a server (e.g. Use the "http.Server" type instead of "net.Server" lukeed/polka#224 "Use the http.Server type instead of net.Server", patch: check to see if stream has been aborted before writing to it.  lukeed/polka#221 stream-abort handling) that remain unreviewed/unmerged.

Relying on an effectively unmaintained dependency for the default Node server means bug fixes, security patches, and Node.js compatibility updates may never land, and downstream SvelteKit users have no clear path to get them.

Describe the proposed solution

Swap the web server that adapter-node uses for an actively maintained alternative, or move to a minimal in-house request handler so the adapter no longer depends on Polka.

Possible directions to evaluate:

• Use a maintained minimal router/server such as Hono, or @hono/node-server, which is actively developed and works well with Web-standard Request/Response.
• Use a small, actively maintained alternative in the same spirit as Polka.
• Replace Polka with a thin internal handler built directly on Node's http/http2 modules, since adapter-node only needs basic routing/middleware and this removes an external dependency entirely.

Goals/constraints for the replacement:

• Preserve current behavior and configuration (host/port/socket via env vars, ORIGIN/proxy headers handling, body size limits, compression, static asset serving).
• No (or minimal) breaking changes for existing adapter-node users.
• Active maintenance and ongoing Node.js version compatibility.

Happy to help test or contribute a PR if there's agreement on a preferred direction.

Alternatives considered

No response

Importance

would make my life easier

Additional Information

No response

[SukeshP1995]

https://encore.dev/ts is faster than mono

[hyunbinseo]

Current handler.js is generated as an Express.js compatible middleware:

Alternatively, you can import the handler.js file, which exports a handler suitable for use with Express, Connect or Polka (or even just the built-in http.createServer) and set up your own server:

// let SvelteKit handle everything else, including serving prerendered pages and static assets
app.use(handler);

This is the only reason why I am just loading the built index.js in my template, instead of customizing it:

• https://github.com/hyunbinseo/svelte-kit-template/blob/main/docs/setup-node.md#pm2

I would love a minimum middleware for modern libraries such as Hono.

Other Suggestions

• Make adapter-node more minimal. e.g. require Hono and define Node.js server config there (e.g. PORT)
• Option to opt-out of bundling/serving src/static - possibly by providing 2 different middleware modules?