Explanation

1. Derive fiat order sourceAmount from on-chain tx data

Currently, the fiat submit flow derives sourceAmountRaw from order.cryptoAmount - a human-readable value reported by the on-ramp provider. This value may not precisely reflect what was actually received on-chain.

This PR reads the actual transferred amount from the completed on-chain transaction (order.txHash) instead. For native tokens, the amount is taken from tx.value. For ERC-20 tokens, the amount is decoded from the transfer(address,uint256) call data. If the on-chain read fails or the transaction hash is missing, the existing order.cryptoAmount derivation is used as a fallback.

The implementation introduces:

• getTransferredAmountFromTxHash - a generic utility in utils/transaction-receipt.ts that reads transferred amounts from any on-chain transaction (native or ERC-20). Takes explicit chainId and tokenAddress params for reusability.
• resolveSourceAmountRaw - a fiat-strategy-specific function in strategy/fiat/utils.ts that orchestrates the on-chain read with order.cryptoAmount fallback.
• getRawSourceAmountFromOrderCryptoAmount - the existing decimal-shift conversion, moved from fiat-submit.ts to strategy/fiat/utils.ts and renamed for clarity.

2. Persist fiat order metadata on metamaskPay

The TransactionPayController state is cleaned up when a transaction is finalized (confirmed/failed/dropped). This means fiatPayment.orderId and the provider info are gone by the time the user opens the activity/transaction-details view.

To enable the mobile activity view to show a fiat order status row (and query RampsController:getOrder for live status), this PR persists the fiat order ID and provider code on transaction.metamaskPay before polling begins in submitFiatQuotes.

Changes:

• MetamaskPayMetadata (transaction-controller/types.ts) — Added fiatOrderId?: string and fiatProvider?: string fields.
• submitFiatQuotes (fiat-submit.ts) — Calls updateTransaction to persist fiatOrderId and fiatProvider on tx.metamaskPay before waitForOrderCompletion starts polling. This ensures data is available even while the order is still in-flight.
• Tests — Two new tests verify metadata persistence and that existing metamaskPay fields are preserved.

References

• Related to the fiat strategy submit flow introduced in feat: Implement FiatStrategy submit flow with order polling and relay execution #8347

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them