wallet: skip APS when no partial spend exists #34405

1. 
   8144225309 commented at 4:36 am on January 26, 2026: none

   Fixes #25150

   APS (Avoid Partial Spends) runs a second coin selection pass to fully spend UTXOs sharing a scriptPubKey. This currently runs unconditionally, even when the first selection has no partial spend. Running APS unnecessarily wastes computation and can produce a worse result when there was nothing to fix.

   Detect partial spends by comparing selected vs available UTXO counts per scriptPubKey, reusing available_coins. Skip APS if none found.

   Test updated to create partial spend scenarios so tracepoints fire.

   ---

   Supersedes #34362 which was corrupted by a shallow clone force-push.

2. DrahtBot added the label Wallet on Jan 26, 2026
3. 
   DrahtBot commented at 4:37 am on January 26, 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/34405.

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

4. 8144225309 force-pushed on Jan 26, 2026
5. 8144225309 force-pushed on Jan 26, 2026
6. 8144225309 force-pushed on Jan 26, 2026
7. wallet: skip APS when no partial spend exists

   APS runs a second coin selection to fully spend UTXOs sharing a
   scriptPubKey. Currently runs unconditionally, even when the first
   selection has no partial spend and APS cannot help.
   
   Detect partial spends by comparing selected vs available UTXO counts
   per scriptPubKey inside CreateTransactionInternal, reusing available_coins.
   Add has_partial_spend to CreatedTransactionResult. Skip APS if false.
   
   Update interface_usdt_coinselection test to expect APS to be skipped
   when no partial spend exists. Add new test that creates a partial spend
   scenario so the full APS tracepoint flow is verified.
   
   Fixes #25150

   53de94fb82
8. 8144225309 force-pushed on Jan 26, 2026

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