Stop stale quote requests from overwriting new input

Debouncing reduces the number of quote requests. It does not prevent an earlier request from resolving after a later one. A swap form needs both traffic control and response identity checks.

Give each request a generation

Increment a counter whenever the trade context changes. Capture the counter with the normalized chain, account, tokens, amount and recipient before starting the request. A response may update the form only if its generation still matches the active context.

Illustrative control flow

edit input → increment generation → clear executable quote

wait for input pause → request with captured generation

response → compare generation → accept or discard

AbortController can cancel fetch work and response consumption. Abort the previous request when starting a replacement, but keep the generation check: cancellation can race with completion and does not undo work already performed remotely.

Separate loading from freshness

A previous estimate can remain visible while refreshing if the interface clearly marks it as stale. It must not remain executable. Store displayEstimate and executableQuote separately so a loading animation cannot accidentally preserve an old transaction button.

Do not debounce the action that clears unsafe state. Invalidation should occur immediately on input change; only the next network request waits. Likewise, a wallet account change invalidates quotes even when the token amount has not changed.

A deterministic test

Start request A for one unit, then B for ten units. Resolve B first and A second. The final output must belong to ten units. Repeat with A rejecting after B succeeds: the old failure must not replace the new successful quote with an error message. These tests need controlled promises, not a slow live endpoint.