Research: FDC3 Post-Trade Cash-Leg Settlement (TraderX ↔ BankerX)

Objective

Complete the trading lifecycle beyond execution: let TraderX blotter rows dispatch standardized post-trade settlement instructions to a clearing desk through FINOS FDC3 3.0, without changing TraderX backend service contracts.

Inputs Reviewed

• spec.md (016) and the 014-fdc3-intent-interoperability transition delta
• FINOS FDC3 3.0 intent/context usage patterns; our authored fdc3.payment context type (FINOS PR #2204)
• ISO 20022 CBPR+ message structure: pacs.008 (credit transfer initiation) → pacs.002 (payment status report, Acsc)
• RFC 4122 UUIDv4 UETR as the end-to-end settlement reference
• BankerX reference implementation (synaptic-fx-terminal): ADR-555 Alcove Runtime Guardian pre-flight, sanctions Bloom screening, solvency check, atomic settlement across the Trilateral Settlement Powerhouse (Solana Token-2022 RequiredMemoTransfers, XRPL Altnet DENSE-16 SHAMap, SynapticChain L1 SMR)
• state 009 blotter interaction patterns and state 012/014 convergence + interop baselines

Key Decisions

1. Reuse the state-014 FDC3 adapter baseline (agent detection, listeners, graceful absence) rather than building a parallel stack.
2. Use fdc3.raiseIntent("StartPayment", paymentContext) as the single settlement entry point; paymentContext carries the full ISO 20022-adjacent payload so the clearing desk never re-keys data.
3. Bind every settlement to an RFC 4122 UUIDv4 UETR minted at dispatch time; the UETR is the join key across blotter, BankerX, and pacs.002 confirmation.
4. Keep TraderX crypto-free and under 2ms dispatch: all compliance (guardian, sanctions, solvency) runs in the BankerX tier.
5. Treat FDC3 availability as optional: identical fallback (toast + direct dispatch URI) as state-014 degraded mode.
6. Backend TraderX services unchanged; settlement state arrives back through FDC3 context listeners only.

Risks and Mitigations

• Risk: paymentContext drift against the upstream FDC3 proposal.
  • Mitigation: schema pinned in contracts/contract-delta.md; reference flow validated by the BankerX adapter tests.
• Risk: settlement confirmations arriving for stale or duplicated dispatches.
  • Mitigation: UETR-keyed correlation; a row is only marked SETTLED on a matching-UETR Acsc.
• Risk: long settlement latency masks UI failures.
  • Mitigation: structured diagnostic logging of IntentResolution (target app, status) so operators can trace dispatches (FR-01604).
• Risk: non-conformant payloads rejected by CBPR+ validation downstream.
  • Mitigation: field-level validation at context-build time (amount/currency/pair/rate/debtor/creditor present and well-formed).
• Risk: partial rail availability in the trilateral settlement topology.
  • Mitigation: networkRouting declares the routing preference; BankerX performs pre-flight before any dispatch is acknowledged.