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Feature Pack 016: FDC3 Post-Trade Settlement Interoperability

Overview​

This pack defines the post-trade settlement lifecycle as a child state of 014-fdc3-intent-interoperability (014 stays the pristine FDC3 baseline; 016 owns the settlement-specific changes in its own overlay, per ADR-002 and the state-transition generation plan).

It bridges TraderX (Front-Office Execution) with a post-trade settlement receiver using FINOS FDC3 3.0 experimental intent/context (StartPayment, fdc3.payment — the exact context type proposed in FDC3 PR #2204) and ISO 20022 pacs.008 / pacs.002 messaging.

Provider-neutral by design: three deployment & receiver variants ship with the pack:

  • Local mock receiver (default) — generation/mock-receiver/, dependency-free and offline-reproducible; the demo and tests never require an external service.
  • BankerX reference adapter (opt-in) — the live settlement terminal (terminal.synapticchain.xyz, labeled XRPL TESTNET (altnet) / Solana DEVNET), swapped in via an app-directory URL change.
  • Standalone Web Blotter Reference — generation/traderx-blotter-web/, live at traderx.synapticchain.xyz with FDC3 App Directory at /appd.json and direct on-chain Solana consensus verification.

The new lesson (014 → 016)​

  • Mapping an execution to valid payment instructions, currencies, and counterparties.
  • UETR-keyed correlation of trade ↔ payment request ↔ settlement status report.
  • Preventing duplicate settlement requests.
  • Handling rejection, timeout, and uncertain outcomes honestly.
  • Settlement status taught as a concept distinct from trade status.

The rock-solid operational lesson (v15 → v20, 2026-09-30/10-01)​

One sentence: settlement truth must outlive the page that witnessed it.

Concretely, 016 now teaches the full invariant set, each one learned from a real defect and fixed in source (see generation/traderx-blotter-web/angular-deploy/PATCH-NOTE.md v15–v20):

  1. Durable, UETR-keyed registry beat localStorage. A per-browser ledger (v17) means settled rows reset the moment a second browser opens. Truth moved to the adapter's file-backed registry (v20), with one-way ISO 20022 ordering (Pndg → Acsc/Rjct) enforced server-side.
  2. Adoption must be fingerprint-guarded. A registry entry may only stamp a row under (a) an own-UETR match or (b) a full trade-fingerprint match (security, quantity, side, created). Without the created guard, a re-seeded trade after an adapter restart inherits a stale settlement — demonstrated live, then proven non-adopting.
  3. Chain-truth belongs at the reconciliation seam. The on-chain settlement memo (UETR inside the transfer memo) cures rows whose only witness page missed the live status broadcast — the desk settles only after its WOTS+ attestation passes, so a chain memo IS the settlement.
  4. Intent availability gates the UI by construction. The SETTLE action renders only when findIntent('StartPayment') resolves — no config flag.
  5. One desk, many settlements. Desk-reuse (v19): SETTLE reuses/focuses the open desk window instead of spawning duplicates.
  6. Compliance failure shares the pipeline. Rejection surfaces as RejectedByEnclave:SANCTIONS_POLICY_VIOLATION on the same code path — no separate demo path.
  7. Build-source alignment is a gate, not an assumption. The angular bundle builds from the templates/ copy — the 016 overlay must be cp'd over it before every build; literal-marker greps between old and new bundles catch a silently stale build (v20 lesson).
  8. Counts and bytes are logged honestly per run — mocha-retry FINAL STATS overcount (DOM is the truth); served md5 == disk md5 checked per URL-bust (Cloudflare caches JS per full URL).

Intent-availability gating​

The SETTLE (BANKERX) blotter action column is rendered only when fdc3.findIntent('StartPayment') resolves to at least one workspace participant. Base TraderX (no post-trade participant) shows the pristine 014 blotter; the button appears the moment the mock receiver or BankerX joins the workspace — capability discovery by construction, no configuration flag.