TLRecordAuthorizer

Authorizes a single record write from a client: any per-record, per-session rule the host wants to enforce server-side — veto writes the session isn't allowed to make, or rewrite the record on create. The session's meta carries whatever the rule needs (identity, roles, …); for example, force a comment's authorId to the signed-in user so nobody can post in someone else's name.

Called on create, update, and delete of records whose typeName it's registered for (see TLRecordAuthorizers), and only for client pushes — never for server-initiated writes.

prev and next are always at the server's schema version: client writes are migrated before the authorizer runs, so guarding or stamping a field never requires knowing what older clients call it. On create, the record you return is what gets stored (after validation) — no migration runs afterwards, so stamped fields can't be clobbered.

Return null to reject the write — it's skipped and the client self-corrects, exactly like the objectAccess gate. Otherwise the write is allowed, and:

• on create, the record you return is what gets stored, so stamp identity fields here (e.g. set authorId from session.meta); - on update and delete, only allow-vs-reject is used (the returned record's contents are ignored), so use them to veto changes to immutable fields or unauthorized deletes — return next/prev to allow, null to reject.

⚠︎ Runs synchronously inside the commit transaction, on the same path as every document edit — it must be fast and do no I/O. next/prev are client-controlled records, so treat their contents as untrusted; prefer returning null to reject over throwing, though a throw is caught, logged, and treated as a rejection (fail closed) rather than crashing the push. For expensive, async checks (e.g. resolving mentions against who can access a file), react after the fact via onCommittedChanges.

type TLRecordAuthorizer<Rec extends UnknownRecord, SessionMeta> = (
  args: {
    session: {
      isReadonly: boolean;
      meta: SessionMeta;
      sessionId: string;
    };
  } & (
    | {
        next: null;
        prev: Rec;
        type: "delete";
      }
    | {
        next: Rec;
        prev: null;
        type: "create";
      }
    | {
        next: Rec;
        prev: Rec;
        type: "update";
      }
  ),
) => null | Rec;