Postgres backend provider

Status: NEXT_PUBLIC_BACKEND_PROVIDER=postgres selects the server-side blob registry and nothing else. It is not the self-hosting switch, and it gives the browser no data layer.

Table data already runs on self-hosted Postgres — through PostgREST, which the browser repositories speak natively, so the cutover is one address: NEXT_PUBLIC_DATA_URL. See oracle-shift-guide.md. Supabase remains the identity provider either way.

A second, direct-pg set of repositories used to live under backend/providers/postgres/repositories/. It was never imported by anything that shipped: wire-backend.ts reached a stub that threw, because the pg driver cannot run in a browser bundle. It was deleted rather than maintained as a duplicate of the live path; git log has it if the app ever needs to talk to Postgres without PostgREST in front.

What is live

Item	Location
pg pool + RLS session (request.jwt.claim.sub)	backend/providers/postgres/pool.ts, pg-runner.ts
Blob registry	storage/providers/postgres/blob-registry.ts
Tiered blob API	storage/server/blob-api.ts picks the Postgres registry when backend = postgres
Self-host auth stubs	supabase/migrations-self-hosted-postgres/0025_self_host_auth.sql

Server-side blob registry

Server-only, since it uses the Node pg driver:

NEXT_PUBLIC_BACKEND_PROVIDER=postgres
DATABASE_URL=postgres://user:pass@localhost:5432/thesis
NEXT_PUBLIC_BLOB_PROVIDER=tiered
# Auth and table data still Supabase-shaped:
NEXT_PUBLIC_SUPABASE_URL=...
NEXT_PUBLIC_SUPABASE_ANON_KEY=...
# R2 for hot tier (see docs/running/storage/r2-setup.md)

Order matters. Apply supabase/migrations-self-hosted-postgres/ first, then every file in supabase/migrations/. A stock Postgres has none of the furniture Supabase provides implicitly — auth.users in a foreign key, auth.uid() in every RLS policy, storage.buckets, the anon/authenticated/service_role grants — and the base chain uses it from the first file, so 0001_papers.sql fails on line 28 and nothing after it runs. This paragraph used to give the two in the opposite order.

0025 creates a minimal auth.users stub with RLS enabled and no policies; sync user ids from Supabase via service role or direct postgres.

Scheduled maintenance

Two jobs are deployment configuration rather than application code, and one of them has to run or the chunk archive stays empty: see metrics-maintenance.md for the commands, a suggested cron schedule, and the queries that show whether it is working.