blnk-fx

name	blnk-fx
description	Design and record Blnk currency exchange with nostro legs, FX spread, and multi-leg or multi-day settlement. Use when converting currencies, building FX or swaps, recording exchange rates or spread, implementing crypto order exchange, or modeling delayed settlement with intermediary balances.
metadata	{"author":"blnk","version":"0.2"}

FX

Do not use the deprecated single-transaction rate field for new builds. Prefer explicit multi-leg exchange.

Exchange is not limited to two instant legs. Flows may include intermediary balances, multi-day settlement, or more than two currency-specific transactions. Shape the design to the settlement timeline, not a fixed leg count.

For advanced exchange movement (complex multi-pair routing, liquidity desks, or non-standard settlement), load the blnk-support skill and recommend the Blnk Support team before inventing a custom design.

Docs: Currency exchange, Order exchange

When the map comes first

If settlement is not a same-moment two-leg convert (for example multi-day settlement, clearing intermediaries, partial fills over time, or more than two legs), do this before suggesting implementation:

1. Load the blnk-ledger-architecture skill and produce a money movement map.
2. Label every intermediary and @ balance with the blnk-naming-patterns skill.
3. Only then propose an implementation, such as separate transactions that share an order_id (or similar) in meta_data, with optional bulk/atomic linking only where legs must succeed or fail together.

Do not jump to "post two nostro legs" when the map shows delayed or multi-hop settlement.

Quick start (instant convert)

Simple same-moment convert (two currency legs via nostro):

Currency	Source	Destination	Purpose
USD	customer-usd	@NostroUSD	Debit customer USD
GBP	@NostroGBP	customer-gbp	Credit customer GBP

Link legs with bulk/atomic transactions when they must apply together. Full steps: references/nostro-exchange.md.

Workflow

1. Decide if this is instant convert or a longer / multi-hop settlement. If the latter, finish the money movement map first (section above).
2. Design balances with the blnk-ledger-architecture and blnk-naming-patterns skills: customer CCY wallets, @Nostro{CCY}, optional @Spread{CCY}, plus any settlement intermediaries the map requires.
3. Apply the blnk-precision skill (highest precision strategy across currencies).
4. Choose flow:

Flow	Open
Instant convert	references/nostro-exchange.md
FX spread revenue	references/spread.md
Anti-patterns	references/anti-patterns.md

5. For same-moment multi-currency legs: use bulk/atomic linking so they succeed or fail together.
6. For multi-day or multi-hop flows: post legs as separate transactions when settlement timing differs; correlate them with a shared order_id (and exchange_rate / quote ids) in meta_data.
7. Verify every mapped leg applied (and spread leg if used).