ryanRfox · ryanRfox · Jun 9, 2026
diff --git a/go/.changes/unreleased/add-mezo-mainnet-default-stablecoin.yaml b/go/.changes/unreleased/add-mezo-mainnet-default-stablecoin.yaml
@@ -0,0 +1,2 @@
+kind: added
+body: Add Mezo mainnet (chain ID 31612) support with mUSD as the default stablecoin
diff --git a/go/mechanisms/evm/constants.go b/go/mechanisms/evm/constants.go
@@ -74,6 +74,7 @@ var (
 	ChainIDBaseSepolia   = big.NewInt(84532)
 	ChainIDMegaETH       = big.NewInt(4326)
 	ChainIDMonad         = big.NewInt(143)
+	ChainIDMezo          = big.NewInt(31612)
 	ChainIDMezoTestnet   = big.NewInt(31611)
 	ChainIDStable        = big.NewInt(988)
 	ChainIDStableTestnet = big.NewInt(2201)
@@ -140,6 +141,18 @@ var (
 				Decimals: DefaultDecimals,
 			},
 		},
+		// Mezo Mainnet (uses Permit2 instead of EIP-3009, supports EIP-2612)
+		"eip155:31612": {
+			ChainID: ChainIDMezo,
+			DefaultAsset: AssetInfo{
+				Address:             "0xdD468A1DDc392dcdbEf6db6e34E89AA338F9F186", // mUSD on Mezo
+				Name:                "Mezo USD",
+				Version:             "1",
+				Decimals:            18,
+				AssetTransferMethod: AssetTransferMethodPermit2,
+				SupportsEip2612:     true,
+			},
+		},
 		// Mezo Testnet (uses Permit2 instead of EIP-3009, supports EIP-2612)
 		"eip155:31611": {
 			ChainID: ChainIDMezoTestnet,

diff --git a/python/x402/changelog.d/add-mezo-mainnet-default-stablecoin.feature.md b/python/x402/changelog.d/add-mezo-mainnet-default-stablecoin.feature.md
@@ -0,0 +1 @@
+Add Mezo mainnet (chain ID 31612) support with mUSD as the default stablecoin
diff --git a/python/x402/mechanisms/evm/constants.py b/python/x402/mechanisms/evm/constants.py
@@ -442,6 +442,18 @@ class NetworkConfig(_NetworkConfigRequired, total=False):
             "decimals": 6,
         },
     },
+    # Mezo Mainnet (uses Permit2 instead of EIP-3009, supports EIP-2612)
+    "eip155:31612": {
+        "chain_id": 31612,
+        "default_asset": {
+            "address": "0xdD468A1DDc392dcdbEf6db6e34E89AA338F9F186",
+            "name": "Mezo USD",
+            "version": "1",
+            "decimals": 18,
+            "asset_transfer_method": "permit2",
+            "supports_eip2612": True,
+        },
+    },
     # Mezo Testnet (uses Permit2 instead of EIP-3009, supports EIP-2612)
     "eip155:31611": {
         "chain_id": 31611,

diff --git a/typescript/.changeset/add-mezo-mainnet-default-stablecoin.md b/typescript/.changeset/add-mezo-mainnet-default-stablecoin.md
@@ -0,0 +1,5 @@
+---
+"@x402/evm": minor
+---
+
+Add Mezo mainnet (chain ID 31612) support with mUSD as the default stablecoin
diff --git a/typescript/packages/http/paywall/src/evm/gen/decimals.ts b/typescript/packages/http/paywall/src/evm/gen/decimals.ts
@@ -10,5 +10,6 @@
  */
 export const NETWORK_DECIMALS: Record<string, number> = {
   "eip155:31611": 18,
+  "eip155:31612": 18,
   "eip155:4326": 18,
 };
diff --git a/typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts b/typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts
@@ -97,6 +97,14 @@ export const DEFAULT_STABLECOINS: Record<string, ExactDefaultAssetInfo> = {
     version: "2",
     decimals: 6,
   }, // Arbitrum Sepolia USDC
+  "eip155:31612": {
+    address: "0xdD468A1DDc392dcdbEf6db6e34E89AA338F9F186",
+    name: "Mezo USD",
+    version: "1",
+    decimals: 18,
+    assetTransferMethod: "permit2",
+    supportsEip2612: true,
+  }, // Mezo mainnet mUSD (no EIP-3009, supports EIP-2612)
   "eip155:31611": {
     address: "0x118917a40FAF1CD7a13dB0Ef56C86De7973Ac503",
     name: "Mezo USD",
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		kind: added
		body: Add Mezo mainnet (chain ID 31612) support with mUSD as the default stablecoin
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Add Mezo mainnet (chain ID 31612) support with mUSD as the default stablecoin