Fighting Game · Guides & deep dives

V2 Server Currency Authority

source ids, mutation batch size, required server-authoritative ledger flags, unique server request ids, client-authored rejection, and client balance mismatch rejection.

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ServerCurrencyAuthority.V2 is the gameplay-side gate that prevents clients from mutating currency state directly. It complements the broader V2OnlineServices server economy validator by rejecting suspicious currency mutations before they are applied to CurrencyLedger.V2.

Runtime Surface#

  • FV2ServerCurrencyAuthorityPolicy defines the server-only rules: trusted source ids, mutation batch size, required server-authoritative ledger flags, unique server request ids, client-authored rejection, and client balance mismatch rejection.
  • FV2ServerCurrencyMutation wraps a FV2CurrencyLedgerRequest with server request id, server authority id, client-reported balance, client-authored status, and trusted-source status.
  • FV2ServerCurrencyAuthorityResult returns the initial ledger, the committed ledger, applied transactions, the last ledger result, rejection evidence, and blocking issues.
  • ApplyServerCurrencyMutations evaluates a batch against policy and applies mutations through ApplyCurrencyLedgerTransaction only after server authority checks pass.

Authority Rules#

  1. Currency changes originate from the server authority, not client-side balance writes.
  2. Every mutation must include ServerRequestId, ServerAuthorityId, and a ledger request marked bServerAuthoritative.
  3. SourceId must be allowed by the server authority policy and the mutation must be marked trusted by the caller.
  4. Client-authored mutations are rejected before ledger application.
  5. Client-reported balance must match the server ledger result. Mismatches fail closed and preserve the pre-request ledger.
  6. Duplicate server request ids are rejected to prevent replayed or duplicated mutation batches.
  7. Batch application is atomic. If any mutation is rejected, no candidate ledger updates are committed.
  8. Accepted mutations still flow through CurrencyLedger.V2, so currency definitions, caps, negative-balance rules, duplicate transaction ids, and audit trail fields remain authoritative.

Validation Commands#

Run these checks when touching server-authoritative currency management:

bash
python3 V2/ue/Tools/check-v2-server-currency-authority.py
python3 V2/ue/Tools/check-v2-currency-ledger.py
python3 V2/ue/Tools/check-v2-currency-definition.py
python3 V2/ue/Tools/check-v2-ci-workflow.py
python3 -m json.tool V2/ue/Content/V2/Gameplay/Economy/ServerCurrencyAuthority_V2_Contract.json
python3 -m json.tool V2/ue/Build/Horde/v2-buildgraph-job.json
python3 V2/tools/validate-v2-docs.py