[bulk_payment] Missing overflow check when summing batch total in execute_batch_partial

[Wilfred007]

Description

The total-amount accumulation in execute_batch_partial uses plain addition over the batch's amounts without a checked/saturating operation. A sufficiently large or adversarial batch could overflow i128 accumulation, leading to incorrect settlement totals.

Where

contracts/bulk_payment/src/lib.rs (~line 687-701)

Acceptance Criteria

• Replace the running total with checked_add, returning a contract error on overflow
• Add a test that constructs a batch designed to overflow and asserts a clean error instead of a panic or wraparound

[leocagli]

Hi, I'd like to add the overflow check when summing batch totals in execute_batch. Checked-arithmetic fix with a test. Could you assign me?

[Timrossid]

@Timrossid has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer, I’ve reviewed this issue and I would love to work on this. I've worked on similar issues and I am confident that I will be able to resolve it neatly. I can have a PR ready for review soon.

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[Buchi-Einstein]

@Buchi-Einstein has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Can I work on this please

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[devonahi]

@devonahi has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello maintainer, I can handle this issue.

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[Caneryy]

@Caneryy has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi there, can I work on this issue?

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[drips-wave]

Congratulations, @devonahi! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @devonahi: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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