Disabling a submit button solves the UI illusion, not the real failure mode…

Disabling a submit button solves the UI illusion, not the real failure mode: browsers, flaky networks, queued actions and autonomous agents will retry, replay, and duplicate requests before your DOM even updates. The durable fix belongs on the server: make Node/Azure endpoints replay-safe with idempotency keys, small dedupe stores, and explicit outcome semantics (success, already-applied, retryable-failure). Treat every client call as potentially retried by something you do not control, and design your API surface and storage wiring so duplicate deliveries are harmless.