From 6f64fd73ea191f1f2b474a1abfad2cebf44b7e55 Mon Sep 17 00:00:00 2001
From: anilchinchawale <anil24593@gmail.com>
Date: Mon, 22 Jun 2026 22:24:49 +0530
Subject: [PATCH] feat(evm): add XDC Network (50) and XDC Apothem testnet (51)
 default assets

Registers XDC Network mainnet and Apothem testnet in the EVM default-asset
registries (TypeScript, Go, Python) so USD-string pricing ("$0.01") resolves
to native USDC on XDC.

XDC has native Circle USDC (not bridged) with EIP-3009
transferWithAuthorization, so the default exact scheme works without Permit2.
EIP-712 domain values were read on-chain:

- mainnet (eip155:50): 0xfA2958CB79b0491CC627c1557F441eF849Ca8eb1,
  name "USDC", version "2", 6 decimals
- apothem (eip155:51): 0xb5AB69F7bBada22B28e79C8FFAECe55eF1c771D4,
  name "USDC", version "2", 6 decimals

Note: the EIP-712 domain name is "USDC" (not "USD Coin").
Native USDC + CCTP V2 launched on XDC in Aug 2025.
---
 go/mechanisms/evm/constants.go                | 22 +++++++++++++++++++
 python/x402/mechanisms/evm/constants.py       | 20 +++++++++++++++++
 .../evm/src/shared/defaultAssets.ts           | 12 ++++++++++
 3 files changed, 54 insertions(+)

diff --git a/go/mechanisms/evm/constants.go b/go/mechanisms/evm/constants.go
index d616f9449f..53bd15bdee 100644
--- a/go/mechanisms/evm/constants.go
+++ b/go/mechanisms/evm/constants.go
@@ -79,6 +79,8 @@ var (
 	ChainIDPolygon       = big.NewInt(137)
 	ChainIDArbOne        = big.NewInt(42161)
 	ChainIDArbSepolia    = big.NewInt(421614)
+	ChainIDXDC           = big.NewInt(50)
+	ChainIDXDCApothem    = big.NewInt(51)
 
 	// Network configurations
 	// See DEFAULT_ASSET.md for guidelines on adding new chains
@@ -196,6 +198,26 @@ var (
 				Decimals: DefaultDecimals,
 			},
 		},
+		// XDC Network Mainnet
+		"eip155:50": {
+			ChainID: ChainIDXDC,
+			DefaultAsset: AssetInfo{
+				Address:  "0xfA2958CB79b0491CC627c1557F441eF849Ca8eb1", // USDC on XDC (Circle, native)
+				Name:     "USDC",
+				Version:  "2",
+				Decimals: DefaultDecimals,
+			},
+		},
+		// XDC Apothem Testnet
+		"eip155:51": {
+			ChainID: ChainIDXDCApothem,
+			DefaultAsset: AssetInfo{
+				Address:  "0xb5AB69F7bBada22B28e79C8FFAECe55eF1c771D4", // USDC on XDC Apothem (Circle, native)
+				Name:     "USDC",
+				Version:  "2",
+				Decimals: DefaultDecimals,
+			},
+		},
 	}
 
 	// EIP-3009 ABI for transferWithAuthorization with v,r,s (EOA signatures)
diff --git a/python/x402/mechanisms/evm/constants.py b/python/x402/mechanisms/evm/constants.py
index c7b3971bd3..a7c31ff201 100644
--- a/python/x402/mechanisms/evm/constants.py
+++ b/python/x402/mechanisms/evm/constants.py
@@ -504,6 +504,26 @@ class NetworkConfig(_NetworkConfigRequired, total=False):
             "decimals": 6,
         },
     },
+    # XDC Network Mainnet
+    "eip155:50": {
+        "chain_id": 50,
+        "default_asset": {
+            "address": "0xfA2958CB79b0491CC627c1557F441eF849Ca8eb1",
+            "name": "USDC",
+            "version": "2",
+            "decimals": 6,
+        },
+    },
+    # XDC Apothem Testnet
+    "eip155:51": {
+        "chain_id": 51,
+        "default_asset": {
+            "address": "0xb5AB69F7bBada22B28e79C8FFAECe55eF1c771D4",
+            "name": "USDC",
+            "version": "2",
+            "decimals": 6,
+        },
+    },
 }
 
 # V1 legacy constants are in x402.mechanisms.evm.v1.constants
diff --git a/typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts b/typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts
index 4fb47e260c..93fdacc173 100644
--- a/typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts
+++ b/typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts
@@ -105,6 +105,18 @@ export const DEFAULT_STABLECOINS: Record<string, ExactDefaultAssetInfo> = {
     assetTransferMethod: "permit2",
     supportsEip2612: true,
   }, // Mezo Testnet mUSD (no EIP-3009, supports EIP-2612)
+  "eip155:50": {
+    address: "0xfA2958CB79b0491CC627c1557F441eF849Ca8eb1",
+    name: "USDC",
+    version: "2",
+    decimals: 6,
+  }, // XDC Network mainnet USDC (Circle, native)
+  "eip155:51": {
+    address: "0xb5AB69F7bBada22B28e79C8FFAECe55eF1c771D4",
+    name: "USDC",
+    version: "2",
+    decimals: 6,
+  }, // XDC Apothem testnet USDC (Circle, native)
 };
 
 /**