Client / server-only split for shared metadata

Problem

You have a folder like lib/publishers/:

• bluesky.ts, mastodon.ts, ... — call the platform APIs. All start with import 'server-only' (they touch tokens).
• index.ts re-exports the adapters and also a PUBLISHERS metadata object (labels, option fields) used by the admin UI to render forms.

A client component ('use client') imports the registry:

import { PUBLISHERS } from '@/lib/publishers'

Next.js build:

'server-only' cannot be imported from a Client Component

Wrong fix

Removing import 'server-only' from the adapters "works" but silently allows the crypto / token code to bundle into the browser — an actual security regression.

Correct fix

Split the module in two:

• lib/publishers/meta-catalog.ts — no 'server-only'. Just types + the static registry.
• lib/publishers/index.ts — keeps import 'server-only', re-exports from meta-catalog and exports the server-only adapters.

Then:

• Client UI: import { PUBLISHERS } from '@/lib/publishers/meta-catalog'
• Server action: import { runShortPublisher } from '@/lib/publishers'

Rule of thumb

Any file that could conceivably be imported by a client component must NOT import 'server-only'. If a barrel index needs to be shared, split the pure-data parts out and keep the server-only stuff behind a separate entry point.

Grep before shipping:

rg "import 'server-only'" src/lib | while read line; do ... ; done

Then check every use client component that transitively hits those modules.