Summary

New @constructive-io/fetch package — a lean isomorphic fetch wrapper that fixes *.localhost subdomain handling in Node.js.

Problem: Node.js has two issues with *.localhost subdomains that break local development with the Constructive GraphQL server's subdomain routing:

1. DNS — fetch('http://auth.localhost:3000/') throws ENOTFOUND (nodejs/node#50871)
2. Host header — Node's fetch (undici) treats Host as forbidden and silently drops it

Solution: createFetch() returns a fetch function that:

• In Node.js: uses node:http/node:https for *.localhost URLs (fixing DNS + Host header), delegates everything else to globalThis.fetch
• In browsers: returns globalThis.fetch as-is (browsers handle *.localhost natively)

Zero dependencies. ~100 lines of source code. Designed to replace @constructive-io/node as the default fetch for generated SDK clients (see constructive#1033).

API

import { createFetch } from '@constructive-io/fetch';

const fetch = createFetch();
const res = await fetch('http://auth.localhost:3000/graphql', { ... });

Review & Testing Checklist for Human

• Verify the *.localhost → localhost rewrite + Host header injection works against a real PostGraphile server with subdomain routing
• Confirm non-localhost URLs pass through to globalThis.fetch without modification
• Review node:http request handling covers all needed fetch options (method, headers, body, signal)

Notes

• Uses synchronous require('node:http') rather than async import() — works in CJS (the monorepo target) and avoids bundler analysis issues
• The result of createFetch() is cached (singleton) — safe to call repeatedly
• 8 tests passing covering: subdomain detection, Host header preservation, plain localhost passthrough, content-type forwarding

Link to Devin session: https://app.devin.ai/sessions/0e3a5bf6765a4c979b64ef786a813225
Requested by: @pyramation