[Bug]: Coinselection Autopilot (Bitkit)

[catch-21]

Describe the bug

When using either the default coin selection setting of Autopilot with "Lowest Fee' OR when using manual coin selection that automatically uses "Use smallest UTXO's first" the result is the same for both: more UTxOs are selected for input to a transaction than required to satisfy the output and fee. This results in paying a higher fee than could have been achieved with less inputs.

Reproduce

1. Have two of more UTxOs in the wallet
2. Make a transaction with an output amount plus fee significantly lower than at least one of your UTxOs
3. If using Manual coin selection, the 'Auto' option will show you which UTxOs are being selected (to use smallest UTXO first) but it actually uses more UTxOs than needed, including the largest.
4. If using Autopilot coin selection, it isn't possible to immediately see the selected UTxOs. You can either check the proposed fee against your expectations (compare with manual coin selection) or you can submit the transaction and check what inputs were actually used.
5. Either way, the wallet uses more inputs than necessary when trying to optimise for low fee or use smallest UTxO first.

Screenshots / Recording

This screengrab shows manual coin selection for a transaction on regtest. Either of the two UTxOs are large enough to satisfy the total requires yet the Auto insists on using both. The same two UTxOs are selected when using Autopilot (default).

Simulator.Screen.Recording.-.iPhone.15.-.2024-04-25.at.17.14.49.mp4

Operating system

Android 13 TKQ1.220829.002

Bitkit version

c55c045

Log output

No response

[coreyphillips]

Autopilot/Automatic Coin Selection is a feature we have to temporarily remove from the UI until a later date (after we come out of beta) where we can enable it and thoroughly test it. We were meant to remove/comment out this setting earlier to avoid confusion, but never got around to it.

[catch-21]

This problem is partly hidden by #1761 because now the user doesn't know what type of autopilot is being used. However, in manual mode there is still an Auto option that is 'use smallest utxo' and that doesn't work correctly.

[catch-21]

The simplest fix here is to remove the text "Small: uses smallest UTxO's first"

[pwltr]

Should start with implementation in beignet and add tests there. Then integrate into Bitkit.

[JeanlChristophe]

User can select coin selection method:

• Manual
• Autopilot

Autopilot mode options:

• Consolidate
• Maximum Privacy
• Minimum UTXOs