Supabase Core

Supabase Core

Shared model for the supabase cluster. The feature-build, current-API, and performance spokes all depend on these interlocking concepts — keep them consistent here so no spoke contradicts another.

1. The authorization model (Supabase's defining decision)

Authorization lives in the database, as Postgres Row-Level Security. Supabase exposes your tables directly (the auto-generated Data API / PostgREST), so a request can reach a table without passing through any app server. RLS is the boundary every product enforces:

Request ──carries──> Role + JWT claims ──checked by──> RLS Policy(ies) ──on──> Table/Storage object

• RLS is default-deny once enabled, but OFF by default on a new table. Enable RLS on every table in an exposed schema (especially public), then write policies that match the actual access model — don't reflexively stamp the same auth.uid() policy on every table. → supabase, supabase-developer
• A policy is per-command. An UPDATE first has to SELECT the row — without a SELECT policy, updates silently affect 0 rows (no error). Storage upsert needs INSERT + SELECT + UPDATE; INSERT alone makes file replacement fail silently.
• Views and privileged code bypass RLS. Create views WITH (security_invoker = true) (Postgres 15+); keep security definer functions in a private/unexposed schema; on older Postgres, revoke view access from anon/authenticated.

Rule: the narrowest policy that satisfies the real access model — and treat enabling the Data API on a schema, adding a permissive policy, or exposing a view as a security change worth stating.

2. Keys & roles (who reaches the database, and as what)

The role + JWT decide which policies apply. service_role ignores RLS entirely, which is exactly why it must never reach the browser.

3. Auth claims & sessions (the silent traps)

• Never use user_metadata / raw_user_meta_data in authorization. It is user-editable and can appear in auth.jwt(). Put authorization data in app_metadata / raw_app_meta_data. → supabase
• JWT claims aren't fresh until the user's token refreshes — app_metadata/auth.jwt() can lag.
• Deleting a user does not invalidate existing access tokens — sign out / revoke sessions, keep JWT expiry short, validate session_id against auth.sessions for sensitive ops.
• On the client, distinguish getSession (fast, trusts local) from getUser/getClaims (revalidated); use @supabase/ssr for cookie-based SSR. → supabase

4. Products map onto the same boundary

Feature wiring across these → supabase-developer. Current per-product API/config (which drifts between versions) → supabase. Query/index/pooling performance underneath → supabase-postgres-best-practices.

5. The schema-change workflow (iterate freely, commit cleanly)

1. Iterate with execute_sql (MCP) or supabase db query (CLI) — runs SQL directly, no migration-history entry, so you can change your mind. Do NOT use apply_migration to iterate a local schema — it writes history on every call and breaks db diff/db pull.
2. Run advisors → supabase db advisors (CLI v2.81.3+) or MCP get_advisors; fix findings.
3. Re-check the security traps in §1–§3 if the change touches views, functions, triggers, storage, or auth.
4. Generate the migration → supabase db pull <name> --local --yes, then supabase migration list --local to verify. → supabase

CLI gotchas: supabase db query needs v2.79.0+; supabase db advisors needs v2.81.3+ — fall back to MCP execute_sql / get_advisors. Always discover commands via --help; the CLI structure changes between versions.

6. Version / conventions

• Supabase changes frequently — do not trust training data. Function signatures, config.toml, and API conventions drift between versions. Look up the topic first: MCP search_docs → fetch any docs page as markdown (append .md to the URL) → web search. → supabase
• Verify your work: after any fix, run a test query confirming it. A fix without verification is incomplete.
• Recover, don't loop: if an approach fails 2–3 times, change method / check docs / read logs — don't re-run the same command.

7. Shared guardrails

• RLS-by-default: enable it on every table in an exposed schema; policies match the real access model.
• Remember per-command policies: UPDATE needs SELECT; storage upsert needs INSERT + SELECT + UPDATE.
• app_metadata, never user_metadata, for authorization claims.
• Never expose service_role/secret keys in public clients; publishable keys for the browser.
• Views security_invoker; security definer functions out of exposed schemas.
• State every data-access-surface change (RLS enable/policy, exposed schema, view, storage policy, key).
• Verify against live docs before implementing; verify the result with a test query after.
• Supabase vs a hand-rolled backend: pick Supabase for Postgres + the RLS boundary + batteries-included Auth/Storage/Realtime; if you need heavy custom server logic beyond Edge Functions, weigh a dedicated backend cluster alongside it.