Implement NonceManager with atomic sequence reservation

[N-thnI]

Description

Add the core nonce/sequence manager that replaces three diverging implementations.

Problem Statement

Sequence management is currently implemented three times: vero-core-engine/engine-bridge/src/nonce-manager.ts, vero-relayer-service/src/relayer/nonceManager.js, and ad-hoc handling in the dashboard. That divergence has already produced separately-filed bugs — vero-core-engine#164 (check-then-act race in reserve()), #183 (refresh() bypasses the per-account lock), and vero-relayer-service#198 (a cached sequence served from inside the lock, causing tx_bad_seq at default concurrency). Consolidating means this class of bug gets fixed once instead of three times.

Proposed Changes

• Create src/nonce/index.ts exporting a NonceManager class
• reserve(account) returns the next sequence and marks it consumed in a single atomic step — no observable window between read and write
• Track reservations per account, keyed by public key
• Never serve a cached sequence value from inside a reservation; see the sibling locking issue
• Export from src/index.ts

Technical Implementation Scaffolding

• Target Repository: vero-sdk
• Target Path: src/nonce/index.ts
• Branch Naming: feat/issue--nonce-manager-core
• Authority Context: Security-sensitive — transaction sequencing

Acceptance Criteria

• Two concurrent reserve() calls for the same account never return the same sequence
• Reservations for different accounts do not block each other
• Unit tests cover the concurrent case explicitly
• npm test, npm run typecheck, npm run lint, and npm run build all pass

Definition of Done

• Reviewed by lead maintainer
• Pull request merged via verified status check

[amankoli09]

can i work on this issue PR merge within 1hr

[telemarkdigital-publisher]

I can take this if assigned. I did a quick pass over the SDK shape and would keep the PR scoped to the nonce manager surface.

Plan:

• add src/nonce/index.ts with NonceManager.reserve(account) tracking per-account sequence state by public key and making the read/increment/mark-consumed step atomic
• avoid a global lock so separate accounts can reserve concurrently; if Add a per-account async lock primitive for nonce reservation #2 lands first, reuse that primitive, otherwise keep the smallest internal keyed critical section needed for this issue
• add focused Jest coverage for same-account concurrent reservations returning distinct sequences and different-account reservations not blocking each other
• export the module from src/index.ts without changing unrelated SDK APIs

Verification before PR: npm test, npm run typecheck, npm run lint, and npm run build.

[grantfox-oss]

🦊 GrantFox — @amankoli09 has been assigned to this issue as part of the Third Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #1)
2. Your PR will be reviewed by the Vero-protocol maintainers

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[N-thnI]

Closing — the NonceManager core this issue describes was delivered by PR #6, which also had to implement it in order to write the concurrency tests it was assigned.

@amankoli09 — this is our mistake, not yours. We filed #1–#5 simultaneously without flagging that #3, #4, and #5 all sit on top of #1 and #2, so the person assigned #5 built the foundation to get their own work done. You shouldn't lose out for that. Please pick any other open issue in this repo and we'll assign it to you straight away — or tell us which one you want and we'll sort it. Sorry for the wasted setup time.

[amankoli09]

@N-thnI no worries I'll take the other one thanks

[amankoli09]

@N-thnI I have applied to #51 bro if possible please consider me in reward list it would be great help for me