Variable withPostgresClientConst Alpha

Alpha. Contributes ctx.postgres — an RLS-scoped pg client, the safe version of "authenticate, then query as the user". This is the direct-connection counterpart to withSupabaseClient, and its service-role companion is withPostgresAdminClient (@supabase/server/middleware/postgres-admin).

Every query runs in its own short transaction that injects the caller's claims and drops to their role, exactly like PostgREST:

begin;
select set_config('request.jwt.claims', $claims, true);  -- auth.uid() resolves
set local role "authenticated";                          -- RLS now enforces
<your query>
commit;
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Everything is transaction-local, so nothing leaks onto the pooled connection.

Only authenticated and anon are assumed. A token naming any other role — including service_role — is refused with a 500 and code: 'UNSUPPORTED_ROLE', never silently downgraded to anon: running the query as the wrong identity would return zero rows and leave nothing to debug. Bypassing RLS is a separate, explicit opt-in: compose withPostgresAdminClient.

Custom roles. Supabase supports custom Postgres roles via the role claim, and RLS still applies to them. They are not supported here yet, so such a token is refused rather than downgraded.

Reads the caller's claims from ctx.jwtClaims, which withSupabase populates (JWKS-verified) — so after withSupabase in a pipeline it composes directly:

pipeline([withSupabase({ auth: 'user' }), withPostgresClient()], handler)
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Standalone (no withSupabase), pair it with withClaims so ctx.jwtClaims is present before it runs.

Table grants. Queries run as authenticated or anon, so those roles need explicit table privileges (e.g. `grant select, insert on

to authenticated`) in addition to RLS policies. A missing grant fails with `permission denied` (SQLSTATE 42501) before RLS is consulted.

Runtime note. pg needs raw TCP, so this runs on Node/Deno (including the Supabase Edge runtime), not on Workers-style isolates.

The composable middleware surface tracks @supabase/middleware 0.x — entry shapes, context keys, and config options may change between 0.x releases.

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