CHANGELOG

Does this branch warrant an entry to the CHANGELOG?

• Yes
• No

Dependencies

none

Requirements

If you have made any visual changes to the GUI. Make sure you have:

• Tested on iOS device
• Tested on Android device
• Tested on small-screen device (iPod Touch)
• Tested on large-screen device (tablet)

Description

Fixes the Sell scene "Max" bug where the previously entered fiat amount was momentarily copied into the crypto field (e.g. entering 100 USD, then tapping Max, showed 100 in the crypto field before the real max resolved).

Root cause is in handleMaxPress in RampCreateScene.tsx. On the sell path it flipped lastUsedInput to 'crypto' before awaiting the async max calculation, while amountQuery still held the previously entered fiat value { exchangeAmount: '100' }. During that async gap displayCryptoAmount took its lastUsedInput === 'crypto' branch and returned amountQuery.exchangeAmount (the fiat number), so the crypto field rendered the fiat value. On large wallets the max calculation (getMaxSpendable) is slow, so the wrong value lingered and routing stalled.

The fix sets the max amount query before flipping the input type (and no longer flips it before the await), so the display memos take their max branch immediately and the crypto field only ever shows the computed max. Buy is unchanged (its branch has no await, so its state updates already batch).

Hardening around the same async max window (added while addressing review rounds, all folded into the one commit):

• A manual edit during the compute cancels the in-flight max via a shared cancelPendingMax helper (bumps a monotonic request id, clears the pending auto-nav and the computing spinner), so a late-resolving max cannot overwrite the typed amount or auto-navigate on it.
• Auto-navigation is suspended while a wallet, fiat, or region picker is open (withPickerOpen / showPickerModal), so a max quote resolving mid-selection cannot navigate out from under the modal; the max keeps computing and navigates once the picker closes.
• The fiat-change check compares against the resolved displayed fiat, so re-selecting the displayed default no longer cancels an in-flight max.
• The sell max compute is wrapped in try/catch: on rejection it surfaces the error and recovers instead of leaving the scene blank with auto-nav armed.
• A spinner + disabled Max shows during the compute (and overlapping Max taps are ignored), so a slow max gives feedback instead of a blank, re-tappable scene.

Asana: https://app.asana.com/0/1215088146871429/1215965639107175

Testing (iOS sim, edge-funds, My Ether 4 / ETH, Sell scene):

• Entered a fiat amount, tapped Max: the crypto field shows the wallet's max spendable amount, not the fiat value.
• Hack-verified the transient by temporarily widening the async window: with the fix, during the window the crypto field shows the converted value (not the entered fiat number); reverting to the old ordering under the same widened window reproduces the fiat-in-crypto flash. All temporary edits reverted; working tree clean.