Optimise vested amounts computation using math/big

[masih]

Continuous-vesting proration is amount * elapsed / duration, which is an integer computation. Going through sdk.Dec allocates a scaled big.Int per coin only to truncate the extra precision back away. Use math/big.Int directly and skip the round trip.

While at it:

• rename the loop-local "x" in PeriodicVestingAccount.GetVestedCoins to "elapsed" so it matches the continuous-vesting variable naming
• correct the Validate() error string on continuous and periodic vesting accounts: the predicate fails when start-time >= end-time, so "cannot be before end-time" was reversed
• cover two non-aligned timestamps in TestGetVestedCoinsContVestingAcc

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	May 18, 2026, 2:17 PM

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 59.27%. Comparing base (b671648) to head (09773ea).

Files with missing lines	Patch %	Lines
sei-cosmos/x/auth/vesting/types/vesting_account.go	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3456      +/-   ##
==========================================
- Coverage   59.29%   59.27%   -0.03%     
==========================================
  Files        2126     2126              
  Lines      175702   175701       -1     
==========================================
- Hits       104183   104138      -45     
- Misses      62448    62481      +33     
- Partials     9071     9082      +11     

Flag	Coverage Δ
sei-chain-pr	77.50% <88.88%> (?)
sei-db	70.41% <ø> (ø)

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Files with missing lines	Coverage Δ
sei-cosmos/x/auth/vesting/types/vesting_account.go	89.62% <88.88%> (ø)

... and 26 files with indirect coverage changes

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[cursor]

PR Summary

Medium Risk
Touches vesting amount computation, which can affect spendable balances if the integer math changes rounding/truncation behavior. Test coverage is expanded, but any downstream expectations about decimal rounding should be rechecked.

Overview
Optimizes continuous vesting proration by replacing sdk.Dec-based scalar math with direct integer arithmetic via math/big in ContinuousVestingAccount.GetVestedCoins.

Also corrects the inverted validation error message for start/end time ordering in both continuous and periodic vesting accounts, renames a periodic loop-local variable for clarity, and adds test cases covering pro-rata vesting at non-aligned timestamps.

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Rounding behavior changed from bankers rounding to truncation

High Severity

The old code used sdk.Dec arithmetic with RoundInt(), which applies bankers rounding (round-half-to-even). The new big.Int code uses Quo which truncates toward zero. This changes vested amounts by up to 1 unit per denomination at non-aligned timestamps. For example, 1000 * 7/24 previously yielded 292 (rounded) but now yields 291 (truncated). In a blockchain context this is a consensus-breaking change — nodes running different versions will disagree on vesting state.

 

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[masih]

yup and labeled as such. Reviewers, please advise if I can avoid this.