Supabase’s October 30 change: check your next AI-generated table

If your AI coding tool creates tables in Supabase, review the next migration before shipping it. Decide which app roles need access, include the intended grants, explicitly enable row-level security (RLS), define its policies, and test the result with harmless records. Do not solve a permission error by opening a private table to everyone.

This matters most when a generated feature adds a table and immediately queries it through supabase-js or the Data API. Your current screens working today does not tell you whether that next feature will have the permissions it needs.

What changes on October 30?

Supabase’s announcement schedules the new default for existing projects on October 30, 2026. After rollout, newly created tables in the public schema need explicit grants for intended Data API access. Existing tables keep their current grants. The announcement dates from April 28; the approaching rollout makes this a preparation task now. Official change notice.

Supabase distinguishes Data API clients from direct Postgres connections, which it says are unaffected by this change. It also specifically tells people using AI tools to create tables to update their instructions for the grants step. Affected workflows and AI-tool guidance.

Start by identifying the actual path your app uses. Ask the builder or maintainer to point to the relevant client call, server query and migration. A backend service and a browser feature in the same app may need separate answers. Do not infer the connection method from the framework name alone.

Keep table access and row access separate

A grant answers whether a role can use a database object or operation. RLS policies govern which rows it can read or modify. Supabase documents these as separate layers; the rollout does not replace your RLS rules. Data API security model.

For a private resource, a permission plan therefore needs two answers: which operations should this app role reach, and which records should the current user be allowed to act on? Write both answers before asking an assistant to generate SQL.

Treat “the request succeeds” as one observation. It still leaves questions about the identity used, the returned records and the operations available to another user. Conversely, an empty result might be correct isolation or a broken owner path. Compare the result with an expectation you wrote first.

A worked review: adding private project notes

Imagine a fictional app adding a project_notes table. Users should create notes for projects they belong to and read the notes for those projects. Unrelated users and signed-out visitors should have no access. This is an editorial example, not a tested implementation or a report about a particular app.

Before generating the migration, prepare this review record:

The membership rule deserves attention. A generated condition that merely checks that someone is signed in does not express our example’s project-membership requirement. Ask the assistant to explain where that relationship is checked and how the test distinguishes members from unrelated users.

Avoid copying a condition from another table without reviewing its assumptions. A personal to-do app, a shared project workspace and an admin-only workflow have different product rules. The goal is to make the intended access visible in the change, not to find a policy that makes an error disappear.

Review the whole migration before applying it

Ask for a proposed diff containing the table definition, intended role grants, explicit RLS enablement and policies together. Have the maintainer check that each requested operation has a business reason. Keep internal processing tables out of a browser-accessible flow unless the feature actually requires that access.

For the project-notes example, walk through how each rule supports membership-based access. Check who can supply the project identifier on a new note, how membership is established, and what should happen if someone changes that identifier. These are product-specific review questions; the fictional table name alone does not provide a safe policy.

Supabase’s RLS guide documents writing policies for the operations your application needs. Use that reference alongside your actual schema. A copied example is a starting point for review, not evidence that your relationships, roles and permissions are correct.

Also ask whether the proposed change modifies existing objects or default privileges. A migration for one new feature should make any wider permission changes explicit. Review each additional change on its own merits rather than accept it as incidental setup.

Handle a permission error without widening access blindly

Supabase’s announcement shows a 42501 permission-denied example for a missing grant, with a hint identifying the role and privilege. Documented error example.

Read the complete error and the request context. Record the operation, target table and effective role. Then compare them with your permission plan. If the intended role should perform that operation, ask for the smallest appropriate correction and review the row-level behavior too. Do not assume every permission error has the same cause.

For private project notes, granting anonymous reads merely because a hint names anon would conflict with our stated product rule. Investigate why that request is using the anonymous role and what access the feature actually needs. An error message describes a failed request; it does not decide your authorization policy.

Keep privileged credentials out of this troubleshooting shortcut. Supabase documents that service_role bypasses RLS and must remain server-side. Do not move that authority into browser code to make a failing feature work. Role and RLS guidance.

Test the next table, not just yesterday’s screens

Use a disposable staging environment and synthetic accounts. For the fictional feature, create one project with user A as a member, and an unrelated user B. Add harmless notes through the intended feature path. Record expected behavior before running each check.

1. Confirm user A can perform the operations the product permits on their project’s notes.
2. Confirm a signed-out request cannot read or change those private notes.
3. Confirm user B cannot read, edit or delete user A’s project notes through the app’s API path.
4. Confirm user B cannot create a note attributed to a project they do not belong to.
5. Confirm changing the supplied note or project identifier does not cross the intended boundary.
6. Check the returned records and resulting database state, not only the HTTP status or success toast.

These are proposed acceptance checks for this example, not tests performed for this article. Adapt them to the operations your product actually offers. A deliberately read-only feature has different success expectations from an editor.

Save a concise result for each check: environment, account role, synthetic target, expected outcome, observed outcome and unresolved issue. If a test uses a privileged identity, label it separately; it cannot stand in for ordinary member access.

Give your coding assistant a reviewable request

Use a redacted schema or disposable example. The following prompt asks for a proposal and evidence plan, without authorizing a production change:

Review the next Supabase table this feature will create. Identify whether the feature uses the Data API or a direct Postgres connection. Show the proposed table, required per-role grants, explicit RLS enablement and policies together. Explain how each operation enforces our stated ownership or membership rules. Do not apply SQL, disable RLS, add blanket grants or use privileged browser credentials. Propose staging checks for the intended user, a signed-out visitor and an unrelated user. State any settings or relationships you cannot verify, and show the diff for review.

Keep the unresolved questions. If the assistant cannot establish which role a request uses or how project membership is stored, it should ask for that information rather than invent a permissive rule. Review its explanation against the code and administrator-confirmed settings.

What this rollout does not settle

Existing permissions still deserve their own review. Supabase says current tables retain their grants; do not treat the new default as a repair of earlier access decisions. Existing-table scope.

Keep this article’s scope to the table workflow described in the announcement. Review views, functions, storage and other access paths separately using the relevant documentation. Supabase’s API security guide identifies additional controls and qualifications; a conclusion about one new table does not close every application-security question.

For broader implementation review, use the VAS security checklist. This article makes no claim that a website scan verifies private database configuration or proves that a migration is safe.

Before shipping the next feature, the useful handover is simple: the intended access is written down, the proposed migration has been reviewed, allowed and denied cases have been checked with disposable data, and unresolved questions have owners. Recheck Supabase’s current rollout guidance before acting. No customer project, migration or credential was accessed for this draft; the worked example and review prompt are editorial tools.