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This tutorial shows how to:
  1. Bridge USDC from Arbitrum to Base using Across
  2. Swap bridged USDC → WETH on Base via Uniswap V3
  3. Supply the WETH to Morpho RE7’s WETH pool
  4. Return the RE7 vault tokens back to the user’s EOA
All steps run as one Fusion transaction with gas paid in USDC.

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Demo of Composable Orchestration

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Why this matters

With one user signature you can:
  • Bridge, swap, stake — any multi-step flow — without asking the user to sign again.
  • Pay all gas for every step in one ERC-20 (USDC) instead of native ETH on multiple chains.
  • Leave zero “dust”: every last token that isn’t needed is auto-returned to the user.
  • Keep the user in a single, familiar wallet; no pop-ups, no chain switching, no scary approvals.

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Business impact

Developers get shorter build cycles; users get a smoother checkout-style experience. That’s higher conversion and faster feature delivery with almost no smart-contract risk.

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Key Concepts Used

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Code Walk‑Through

Below we highlight the critical parts of supplyToMorpho.ts. Full file lives in your repo.
1

Initialise Multichain Account & MEE Client

const oNexus = await toMultichainNexusAccount({
  signer: walletProvider,           // Embedded or EOA signer
  chainConfigurations: [
    {
      chain: arbitrum,
      transport: http(),
      version: getMEEVersion(MEEVersion.V2_1_0)
    },
    {
      chain: base,
      transport: http(),
      version: getMEEVersion(MEEVersion.V2_1_0)
    }
  ],
});

const meeClient = await createMeeClient({ account: oNexus });
2

Define Trigger & Constraints

const amountConsumed = parseUnits(amount, 6);
const minAfterSlippage = amountConsumed * 80n / 100n;  // 20 % tolerance
const executionConstraints = [greaterThanOrEqualTo(minAfterSlippage)];

const transferToNexusTrigger = {
  tokenAddress: mcUSDC.addressOn(arbitrum.id),
  amount: amountConsumed,
  chainId: arbitrum.id,
};
Why: Fusion mode starts with an empty orchestrator. A single USDC transfer funds it and reveals the amount we’ll use.
3

Bridge USDC with Across

Follow the Across Integration Tutorial to learn how to encode Across.
const depositAcrossData = await prepareAcrossBridgeTransaction({
  depositor: oNexus.addressOn(arbitrum.id),
  recipient: oNexus.addressOn(base.id),
  inputToken: mcUSDC.addressOn(arbitrum.id),
  outputToken: mcUSDC.addressOn(base.id),
  inputAmount: amountConsumed,
  originChainId: arbitrum.id,
  destinationChainId: base.id,
});
Two instructions are added:
  1. Approve USDC to Across
  2. Raw calldata deposit
4

Swap USDC → WETH on Base

const swapUSDCtoWeth = await oNexus.buildComposable({
  type: "default",
  data: {
    chainId: base.id,
    abi: UniswapSwapRouterAbi,
    to: mcUniswapSwapRouter.addressOn(base.id),
    functionName: "exactInputSingle",
    args: [{
      tokenIn: mcUSDC.addressOn(base.id),
      amountIn: runtimeERC20BalanceOf({
        tokenAddress: mcUSDC.addressOn(base.id),
        targetAddress: oNexus.addressOn(base.id, true),
        constraints: executionConstraints,
      }),
      tokenOut: weth_Base,
      recipient: oNexus.addressOn(base.id, true),
      amountOutMinimum: 0n,
      fee: 100,
      sqrtPriceLimitX96: 0n,
    }],
  },
});
runtimeERC20BalanceOf waits until bridged USDC arrives and meets executionConstraints.
5

Supply WETH to Morpho & Return Vault Tokens

const supplyToMorpho = await oNexus.buildComposable({
  type: "default",
  data: {
    abi: MorphoPoolAbi,
    to: weth_Re7_Morpho_Pool,
    chainId: base.id,
    functionName: "deposit",
    args: [
      runtimeERC20BalanceOf({
        tokenAddress: weth_Base,
        targetAddress: oNexus.addressOn(base.id, true),
        constraints: executionConstraints,
      }),
      oNexus.addressOn(base.id, true),
    ],
  },
});
Then transfer RE7 vault tokens back to the user EOA.
6

Quote & Execute Fusion Transaction

const quote = await meeClient.getFusionQuote({
  trigger: transferToNexusTrigger,
  feeToken: toFeeToken({ mcToken: mcUSDC, chainId: arbitrum.id }),
  instructions: [
    approveUsdcSpendToAcross,
    depositAcross,
    approveUniswapToSpendUSDC,
    swapUSDCtoWeth,
    approveMorphoVaultToSpendWeth,
    supplyToMorpho,
    moveRe7WethBackToEOA,
  ],
});

const { hash } = await meeClient.executeFusionQuote({ fusionQuote: quote });

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What You Achieved

  • One signature → multi‑step, cross‑chain flow
  • Gas paid in USDC, no ETH needed
  • Exact amounts supplied, no guesswork
  • Vault tokens automatically returned to user
Extend this flow by adding staking, leverage, or any other operation—without writing Solidity.
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