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Featured for Wallets. Recover unused balances automatically. Canonical wallet-cleanup pattern.

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Scenario

A user wants to swap 80% of a USDC balance to USDT but deliberately leave the remaining 20% untouched. In compose terms this is a core.split where only one of the two output handles is bound to a downstream node — the other is left dangling. Dangling resources stay on the per-signer proxy contract at the end of execution; sweepTo tells the backend to transfer them back to the sender (or any specified address) so nothing is stranded. This recipe is the canonical shape for dust recovery — any pattern where part of an input is intentionally unused and must not be left on the proxy.

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What this recipe demonstrates

  • core.split with bps: 8000 (80/20) and only one of the two output handles bound downstream.
  • Implicit dust tracking — the unbound handle (b) never becomes an input to another op; the compiler treats its balance as a terminal residual resource.
  • sweepTo: builder.context.sender returns all residual balances to the sender at the end of the transaction, including the deliberately unused 20%.
  • A minimal two-node flow: one split, one swap.

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Full example

Adapted from dustSweep.ts in the composer-sdk-examples repo. 
import {
  createComposeSdk,
  materialisers,
  resources,
} from '@lifi/composer-sdk';

const USDC = '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48';
const USDT = '0xdAC17F958D2ee523a2206206994597C13D831ec7';

const sdk = createComposeSdk({ baseUrl: 'https://composer.li.quest' });

const builder = sdk.flow(1, {
  name: 'dust-sweep',
  inputs: {
    amountIn: resources.erc20(USDC, 1),
  },
});

// Split USDC 80/20.
// Only the 80% portion (`a`) is consumed by the swap.
// The 20% portion (`b`) is intentionally left unbound — it stays on
// the proxy as dust and gets swept back to the sender.
const { a } = builder.core.split('split', {
  bind: { source: builder.inputs.amountIn },
  config: { bps: 8000 },
});

// Swap only the 80% portion to USDT.
builder.lifi.swap('swap', {
  bind: { amountIn: a },
  config: {
    resourceOut: resources.erc20(USDT, 1),
    slippage: 0.03,
  },
});

// sweepTo ensures the unused 20% USDC is transferred back to the
// sender rather than being stranded on the proxy.
// See /composer/composer-api/concepts/sweeping-and-amounts for the full semantics.
const result = await builder.compile({
  signer: '0xYourSignerAddress',
  inputs: {
    amountIn: materialisers.directDeposit({ amount: '10000000' }), // 10 USDC
  },
  sweepTo: builder.context.sender,
});

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What to observe

  • Inputs. One resource input (amountIn: USDC).
  • Nodes. Two: core.split then lifi.swap. Only split.a is referenced — split.b is never consumed.
  • Dangling handle. Destructuring const { a } = builder.core.split(...) quietly drops b from the TypeScript side; on the wire, split still declares both outputs and the compiler knows b is unused.
  • Terminal resources. Two: the swapped USDT (the intentional output) and the unused USDC from split.b (the dust). Both are swept to the sender by sweepTo.
  • sweepTo shape. request.run.sweepTo === { $ref: 'context.sender' } when you pass builder.context.sender. You can also pass a literal address string, as in the swap-to-recipient recipe.
  • producedResources[<name>].simulated?.amountOut. producedResources on the ComposeCompileResult lists both the USDT (from the swap) and the residual USDC amounts.