core/priority: use stable sort for scored priorities - #4611
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Replace slices.SortFunc with slices.SortStableFunc when ordering scored priorities so that equal-score priorities keep first-seen order, with messages processed in ascending peer ID order. Go's sort is unstable for slices longer than ~12 elements, so the equal-score order depended on the sort implementation and could diverge across versions and other implementations. Add a regression test with 24 priorities where tied pairs arrive out of score order. category: bug ticket: none Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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KaloyanTanev
approved these changes
Jul 29, 2026
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #4611 +/- ##
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- Coverage 57.59% 57.54% -0.06%
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Files 246 246
Lines 33707 33707
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- Hits 19415 19398 -17
- Misses 11849 11864 +15
- Partials 2443 2445 +2 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Replaces
slices.SortFuncwithslices.SortStableFuncwhen ordering scored priorities, so equal-score priorities keep first-seen order, with messages processed in ascending peer ID order.Go's sort is unstable for slices longer than ~12 elements (below that, pdqsort falls back to insertion sort, which is stable in practice). For topics with 13+ priorities, the order of equal-score entries was unspecified: it could change whenever Go changes its sort implementation, making mixed-version clusters compute different
PriorityResultvalues from identical inputs, and other implementations could not reproduce Charon's result bytes. The serializedPriorityResultfeeds QBFT proposals, so ordering must be a pure deterministic function of the message set.Adds a regression test with 4 peers and a 24-priority topic where tied pairs arrive out of score order; it fails with
SortFuncand passes withSortStableFunc.category: bug
ticket: none