feat: add USDT0 Legacy Mesh as fallback bridge for TAC

packages/adapters/rebalance/src/adapters/index.ts

@@ -17,6 +17,7 @@ import { CCIPBridgeAdapter } from './ccip';
 import { ZKSyncNativeBridgeAdapter } from './zksync';
 import { LineaNativeBridgeAdapter } from './linea';
 import { ZircuitNativeBridgeAdapter } from './zircuit';
+import { Usdt0BridgeAdapter } from './usdt0';
 
 export class RebalanceAdapter {
   constructor(
@@ -103,6 +104,8 @@ export class RebalanceAdapter {
         return new LineaNativeBridgeAdapter(this.config.chains, this.logger);
       case SupportedBridge.Zircuit:
         return new ZircuitNativeBridgeAdapter(this.config.chains, this.logger);
+      case SupportedBridge.Usdt0:
+        return new Usdt0BridgeAdapter(this.config.chains, this.logger);
       default:
         throw new Error(`Unsupported adapter type: ${type}`);
     }

packages/adapters/rebalance/src/adapters/usdt0/index.ts

@@ -0,0 +1,2 @@
+export { Usdt0BridgeAdapter } from './usdt0';
+export * from './types';

packages/adapters/rebalance/src/adapters/usdt0/types.ts

@@ -0,0 +1,56 @@
+/**
+ * USDT0 Legacy Mesh contract addresses and constants
+ *
+ * USDT0 is Tether's official omnichain USDT built on LayerZero OFT standard.
+ * For TON, it uses the "Legacy Mesh" — a credit/debit pool mechanism that
+ * releases canonical USDT (same jetton as EQCxE6mUtQJKFnGfaROTKOt1lZbDiiX1kCixRv7Nw2Id_sDs)
+ * on TON. The pool currently holds ~9.2B USDT.
+ *
+ * Reference:
+ * - USDT0 Docs: https://docs.usdt0.to/
+ * - Deployments: https://docs.usdt0.to/api/deployments
+ * - Legacy Mesh: https://docs.usdt0.to/overview/the-legacy-mesh
+ */
+
+// ============================================================================
+// Contract Addresses
+// ============================================================================
+
+/**
+ * USDT0 Legacy Mesh OFT contract on Ethereum mainnet
+ * Used for sending USDT to legacy chains (TON, Tron)
+ * Uses credit/debit pool mechanism (not mint/burn)
+ */
+export const USDT0_LEGACY_MESH_ETH = '0x1F748c76dE468e9D11bd340fA9D5CBADf315dFB0' as `0x${string}`;
+
+/**
+ * USDT ERC-20 on Ethereum mainnet
+ * Must be approved to the Legacy Mesh OFT contract before sending
+ */
+export const USDT_ETH = '0xdAC17F958D2ee523a2206206994597C13D831ec7' as `0x${string}`;
+
+// ============================================================================
+// LayerZero Endpoint IDs (USDT0-specific)
+// ============================================================================
+
+/**
+ * TON LayerZero Endpoint ID for USDT0 Legacy Mesh
+ * Note: This differs from Stargate's TON endpoint (30826).
+ * USDT0 uses its own endpoint for the Legacy Mesh routing.
+ */
+export const USDT0_LZ_ENDPOINT_TON = 30343;
+
+/**
+ * Ethereum LayerZero Endpoint ID
+ */
+export const USDT0_LZ_ENDPOINT_ETH = 30101;
+
+// ============================================================================
+// Fee Constants
+// ============================================================================
+
+/**
+ * USDT0 Legacy Mesh transfer fee: 0.03% (3 basis points)
+ * Used for fee estimation when on-chain quoteOFT is unavailable
+ */
+export const USDT0_LEGACY_MESH_FEE_BPS = 3n;