Designed an organization context‑switching system with client localStorage and server‑side cookie mirroring, letting users act as managed organizations while enforcing least‑privilege authorization.

Situation. On NextMariner a maritime professional can manage organizations — companies, academies — that don’t have their own logins. The person is the account; the organization is something they act on behalf of. So a user needs to move through the whole app as any organization they manage, switching between them freely, and that convenience can’t turn into a hole in the authorization.

Task. Context‑switching had to be quick and unobtrusive for the user while making sure the active context could never, on its own, hand someone access they weren’t entitled to.

Action. An OrganizationContext handles it, with storage on both sides. On the client, localStorage is the source of truth for which organization you’re currently acting as, so switching is instant — no round‑trip. A server‑side cookie mirrors it so that server‑rendered pages resolve the same context during SSR; there’s a getServerViewMode on the server that reads it. The important part is that none of that is trusted for access decisions. Authorization gets re‑checked on the server on every request. The frontend context is there for the experience — showing you the right thing — and the server is the only authority on what you’re allowed to do.

Result. A user can act as any organization they manage without friction, and the interface stays in sync on both client and server. But because permissions are verified server‑side every time, none of that convenience weakens the security. Someone tampering with what’s in localStorage changes what their own UI shows them and nothing more — the server still says no.