> ## Documentation Index
> Fetch the complete documentation index at: https://docs.compasslabs.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Embed Fees with Transaction Bundler 

> Turn every on‑chain user action into revenue: embed fees in the same user‑signed transaction.

export const GithubCodeBlock = ({typescript, python}) => {
  const [typescriptCode, setTypescriptCode] = useState("");
  const [pythonCode, setPythonCode] = useState("");
  function removeWhitespace(strings, x) {
    return strings.map(str => {
      let count = 0;
      let i = 0;
      while (i < str.length && count < x && str[i] === " ") {
        count++;
        i++;
      }
      return str.slice(i);
    });
  }
  function cropToSnippet({text, from, to}) {
    const lines = text.split("\n");
    let result = [];
    let isCollecting = false;
    for (const line of lines) {
      if (line.trim() === from) {
        isCollecting = true;
        continue;
      }
      if (line.trim() === to) {
        break;
      }
      if (isCollecting) {
        result.push(line);
      }
    }
    const whitespaceToDelete = result[0].length - result[0].trimStart().length;
    result = removeWhitespace(result, whitespaceToDelete);
    return result.join("\n");
  }
  function removeSnippetComments(code) {
    return code.replace(/(\/\/|#) SNIPPET (START|END) \d+(\n|$)/g, "");
  }
  useEffect(() => {
    if (!typescript) return;
    fetch(typescript.url).then(response => response.text()).then(text => {
      let code = text;
      if (typescript.snippetNumber) {
        code = cropToSnippet({
          text,
          from: `// SNIPPET START ${typescript.snippetNumber}`,
          to: `// SNIPPET END ${typescript.snippetNumber}`
        });
      } else {
        code = removeSnippetComments(code);
      }
      setTypescriptCode(code);
    }).catch(error => {
      console.error("Error loading file:", error);
    });
  }, [typescript]);
  useEffect(() => {
    if (!python) return;
    fetch(python.url).then(response => response.text()).then(text => {
      let code = text;
      if (python.snippetNumber) {
        code = cropToSnippet({
          text,
          from: `# SNIPPET START ${python.snippetNumber}`,
          to: `# SNIPPET END ${python.snippetNumber}`
        });
      } else {
        code = removeSnippetComments(code);
      }
      setPythonCode(code);
    }).catch(error => {
      console.error("Error loading file:", error);
    });
  }, [python]);
  if (!python && !typescript) return null;
  if (!python) {
    return <CodeBlock language="typescript" filename={typescript.name} expandable={typescript?.numOfLinesExpandable ? "true" : null} lines="true" icon="https://upload.wikimedia.org/wikipedia/commons/f/f5/Typescript.svg" code={typescriptCode} children={typescriptCode || !typescript?.numOfLinesExpandable || <div style={{
      whiteSpace: "pre-wrap"
    }}>
        {Array(typescript?.numOfLinesExpandable).fill("-").map(x => x).join("\n")}
      </div>} />;
  }
  if (!typescript) {
    return <CodeBlock language="python" filename={python.name} expandable={python?.numOfLinesExpandable ? "true" : null} lines="true" icon="https://upload.wikimedia.org/wikipedia/commons/c/c3/Python-logo-notext.svg" code={pythonCode} children={pythonCode || !python?.numOfLinesExpandable || <div style={{
      whiteSpace: "pre-wrap"
    }}>
        {Array(python?.numOfLinesExpandable).fill("-").map(x => x).join("\n")}
      </div>} />;
  }
  return <CodeGroup>
  <CodeBlock language="typescript" filename={typescript.name} expandable={typescript?.numOfLinesExpandable ? "true" : null} lines="true" icon="https://upload.wikimedia.org/wikipedia/commons/f/f5/Typescript.svg" code={typescriptCode} children={typescriptCode || !typescript?.numOfLinesExpandable || <div style={{
    whiteSpace: "pre-wrap"
  }}>
          {Array(typescript?.numOfLinesExpandable).fill("-").map(x => x).join("\n")}
        </div>} />
  <CodeBlock language="python" filename={python.name} expandable={python?.numOfLinesExpandable ? "true" : null} lines="true" icon="https://upload.wikimedia.org/wikipedia/commons/c/c3/Python-logo-notext.svg" code={pythonCode} children={pythonCode || !python?.numOfLinesExpandable || <div style={{
    whiteSpace: "pre-wrap"
  }}>
          {Array(python?.numOfLinesExpandable).fill("-").map(x => x).join("\n")}
        </div>} />
</CodeGroup>;
};

🕐 Time to complete: ±10 minutes

🧰 What you need:

* Free [Compass API Key](https://www.compasslabs.ai/login)
* Wallet (EOA or [smart account guide](/v1/wallet-support/overview))

## Introduction

Embedded Fees let you add your fee (on deposit, withdrawal, performance, management, your choice) inside the same user-signed transaction that executes the DeFi flow. It’s fully non-custodial, one atomic transaction, and no new smart contracts.

This guide shows how to bundle three actions into a single atomic transaction using the Compass SDK:

* **Approve:** Set ERC-20 allowance on Morpho
* **Fee:** transfer a portion of the asset to your fee address
* **Deposit:** deposit tokens on Morpho

> This pattern generalizes: you can combine any supported actions ( `Aave/Morpho/Uniswap/Pendle/Sky`, and **any ERC‑4626 vault**) in one bundle.

**By adding a fee step, you get paid automatically whenever users transact with your DeFi product built with the Compass API.**

<Note>
  Learn more about the concept: [How Compass turns on revenue instantly](https://medium.com/@compasslabs/turn-on-revenue-where-users-click-earn-aa15cd8a8bb0).
</Note>

<img src="https://mintcdn.com/compasslabs-f07467e0/xcz0y_akL4AKxR-L/images/Screenshot2025-09-19at18.42.04.png?fit=max&auto=format&n=xcz0y_akL4AKxR-L&q=85&s=3ac3570d503d9398d1ae37229dfaf8fc" alt="Screenshot 2025-09-19 at 18.42.04.png" width="1980" height="952" data-path="images/Screenshot2025-09-19at18.42.04.png" />

## Setup

<Steps>
  <Step title="Install Dependencies">
    Install the required packages.

    <CodeGroup>
      ```shellscript Typescript theme={"system"}
      npm install @compass-labs/api-sdk viem dotenv
      ```

      ```bash theme={"system"}
      pip install compass_api_sdk web3 python-dotenv
      ```
    </CodeGroup>
  </Step>

  <Step title="Set Environment Variables">
    Create a .env file in your project root.

    ```dotenv .env theme={"system"}
    PRIVATE_KEY="your_wallet_private_key"
    RPC_URL="your_ethereum_rpc_url"
    COMPASS_API_KEY="your_compass_api_key"
    ```
  </Step>

  <Step title="Import Libraries & Environment Variables">
    <GithubCodeBlock
      typescript={{
name: "index.ts",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/typescript/src/index.ts",
snippetNumber: 11,
}}
      python={{
name: "main.py",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/python/main.py",
snippetNumber: 21,
}}
    />
  </Step>

  <Step title="Initialize SDK and Account">
    <GithubCodeBlock
      typescript={{
name: "index.ts",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/typescript/src/index.ts",
snippetNumber: 12,
}}
      python={{
name: "main.py",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/python/main.py",
snippetNumber: 22,
}}
    />
  </Step>
</Steps>

<Note>
  The full, uninterrupted code is available at the end of the tutorial.
</Note>

## Get Authorization

Before you can bundle transactions, you need to get an authorization from the Compass API and sign it with your private key. This ensures only you can execute the batch.

<Steps>
  <Step title="Get and Sign Authorization">
    Request authorization from the Compass API and sign it with your wallet to authenticate the transaction batching.

    <GithubCodeBlock
      typescript={{
name: "index.ts",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/typescript/src/index.ts",
snippetNumber: 13,
}}
      python={{
name: "main.py",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/python/main.py",
snippetNumber: 23,
}}
    />
  </Step>
</Steps>

## Bundle the Actions

Now let's bundle the allowance, transfer, and deposit actions for atomic execution. This step shows how to combine both actions into a single transaction using the Compass API.

<Steps>
  <Step title="Create Bundled Transaction">
    Bundle the allowance, transfer, and deposit actions for atomic execution. This step shows how to combine both actions into a single transaction using the Compass API.

    Any transactional endpoint in the Compass API can be turned into an action, see [API Reference](https://docs.compasslabs.ai/v1/api-reference/transaction-batching/construct-bundled-transaction#body-actions).

    <GithubCodeBlock
      typescript={{
name: "index.ts",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/typescript/src/index.ts",
snippetNumber: 14,
}}
      python={{
name: "main.py",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/python/main.py",
snippetNumber: 24,
}}
    />
  </Step>
</Steps>

## Execute the Transaction:

The final step is to sign and broadcast the transaction to the network. This will execute your bundled actions in a single atomic transaction.

<Steps>
  <Step title="Sign and Broadcast Transaction">
    Sign the returned transaction with your private key and broadcast it to the network. Use the helper function we defined above to do this. This is the final step to actually send your bundled transaction to Ethereum.

    <GithubCodeBlock
      typescript={{
name: "index.ts",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/typescript/src/index.ts",
snippetNumber: 15,
}}
      python={{
name: "main.py",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/python/main.py",
snippetNumber: 25,
}}
    />
  </Step>
</Steps>

<Tip>
  For further practice, try bundling different combinations of actions, test with various token pairs, or explore other [Compass Bundler](/v1/transaction-bundler/introduction) features to create more complex transaction bundles.
</Tip>

## Full Code

Here is the full script from the tutorial. Copy and paste into your code editor and play around!

<GithubCodeBlock
  typescript={{
name: "index.ts",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/typescript/src/index.ts",
numOfLinesExpandable: 88,
}}
  python={{
name: "main.py",
url: "https://raw.githubusercontent.com/CompassLabs/api_usecases/main/v1/transaction-bundler/embed_a_fee_in_bundle/python/main.py",
numOfLinesExpandable: 77,
}}
/>

## Resources.

<CardGroup cols={2}>
  <Card title="Compass API Docs" icon="compass" href="https://docs.compasslabs.ai/v1/api-reference/transaction-bundler/construct-bundled-transaction">
    Access detailed API documentation and references
  </Card>

  <Card title="GitHub Examples" icon="github" href="https://github.com/CompassLabs/api_usecases/tree/main/v1/transaction_bundler/">
    View more code examples and implementations
  </Card>
</CardGroup>