Trying to use a local DB with Vercel Postgres fails due to strict pool URL check

The problem

NOTE FROM MAINTAINERS The way to use @vercel/postgres locally is documented here: https://vercel.com/docs/storage/vercel-postgres/local-development --- I thought I could use Vercel Postgres with a local DB for offline development with a custom connection string that points to a local DB... ...

The fix

@vercel/postgres connects through websockets (it is a Neon client), not plain TCP, so pointing it at a local Postgres fails. Two ways around it: follow the documented local-development flow for Vercel Postgres, or run Neon's wsproxy between the client and your local Postgres on port 5432, which one user confirmed works. Also double-check POSTGRES_URL for typos: one reporter's whole issue was a malformed env value.

In gh:vercel/storage#123 (https://github.com/vercel/storage/issues/123), the reporter ran into this: NOTE FROM MAINTAINERS The way to use @vercel/postgres locally is documented here: https://vercel.com/docs/storage/vercel-postgres/local-development --- I thought I could use Vercel Postgres with a local DB for offline development with a custom connection string that points to a local DB... ... The verified resolution: @vercel/postgres connects through websockets (it is a Neon client), not plain TCP, so pointing it at a local Postgres fails. Two ways around it: follow the documented local-development flow for Vercel Postgres, or run Neon's wsproxy between the client and your local Postgres on port 5432, which one user confirmed works. Also double-check POSTGRES_URL for typos: one reporter's whole issue was a malformed env value.