Dust sweep

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Scenario

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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

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,
});

​

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.