wallet: skip APS when no partial spend exists #34362

1. 
   8144225309 commented at 4:38 am on January 21, 2026: none

   Skip the APS coin selection pass when the initial selection contains no partial spend—APS cannot improve privacy in this case.

   Detection compares selected vs available UTXO counts per scriptPubKey, reusing available_coins. Test updated to create an actual partial spend scenario.

   Fixes #25150

2. wallet: skip APS when no partial spend exists

   Compute has_partial_spend inside CreateTransactionInternal using the
   available_coins that are already fetched for coin selection. This avoids
   a redundant AvailableCoins call compared to checking after the fact.
   
   The check determines if the selection spends some but not all UTXOs from
   any scriptPubKey. If no partial spend exists, APS cannot improve privacy,
   so we skip the second coin selection attempt entirely.
   
   Benefits:
   - Avoids unnecessary double coin selection when APS provides no benefit
   - Eliminates misleading tracepoint data
   - Prevents potential disimprovement of selection results
   - No extra AvailableCoins call (uses existing data)
   
   Add has_partial_spend field to CreatedTransactionResult to communicate
   this information from CreateTransactionInternal to CreateTransaction.
   
   Update interface_usdt_coinselection test to set up partial spend scenarios
   so APS tracepoints fire as expected.
   
   Fixes #25150

   b09ffd1563
3. DrahtBot added the label Wallet on Jan 21, 2026
4. 
   DrahtBot commented at 4:38 am on January 21, 2026: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/34362.

   Reviews

   See the guideline for information on the review process. A summary of reviews will appear here.

Contributors
8144225309 DrahtBot

Labels
Wallet