[NO-JIRA] - Fix Mainnet Domain signature

[rarcifa]

Title

Fix mainnet X402 payment flow and harden facilitator API typing

---

Description

This PR fixes a mainnet-only failure in the Facilitator SDK and hardens the API client with strict runtime validation.

Bug Fix: Mainnet EIP-3009 Signature Domain

Mainnet verification was failing because the EIP-712 domain used for USDC.e signing was configured with an incorrect version.

Before

version: '2'

After

version: '1'

Cronos USDC.e implements the EIP-3009 TransferWithAuthorization domain with version "1". Using "2" causes signature verification to fail on mainnet, while testnet appeared to work due to relaxed/local verification.

This change makes mainnet settlement work correctly.

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Hard-Typed Facilitator API Responses

The Facilitator HTTP client is now fully runtime-typed using assertion guards:

• Removes all any usage
• Parses responses as unknown
• Validates payload shape before returning
• Throws descriptive errors on malformed responses

This guarantees that SDK consumers only ever receive correctly shaped data from:

• /v2/x402/supported
• /v2/x402/verify
• /v2/x402/settle

---

Type Cleanup

Replaced an empty interface alias:

export interface X402PaymentRequirements extends PaymentRequirements {}

with:

export type X402PaymentRequirements = PaymentRequirements;

This avoids @typescript-eslint/no-empty-object-type violations and keeps the type model clean.

---

Result

Mainnet X402 payments now verify and settle correctly
API client is fully type-safe at runtime
No any, no unsafe casts
No breaking public API changes

---

Notes for Reviewers

• Testnet behavior remains unchanged
• Mainnet now passes /verify with correct EIP-712 domain
• No dependency changes
• No API surface changes

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	npm/​@​crypto.com/​facilitator-client@​1.0.1 ⏵ 1.0.4	+1		+1	+3
	npm/​@​crypto.com/​facilitator-client@​1.0.1 ⏵ 1.0.3	+1		+1	+3

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