---
title: "Attachments"
description: "Upload files into the sandbox and reference them in prompts."
sidebarTitle: "Attachments"
icon: "paperclip"
---

Use the filesystem API to upload files, then include file references in prompt content.

<Steps>
  <Step title="Upload a file">
    <CodeGroup>
    ```ts TypeScript
    import { SandboxAgent } from "sandbox-agent";
    import fs from "node:fs";

    const sdk = await SandboxAgent.connect({
      baseUrl: "http://127.0.0.1:2468",
    });

    const buffer = await fs.promises.readFile("./data.csv");

    const upload = await sdk.writeFsFile(
      { path: "./uploads/data.csv" },
      buffer,
    );

    console.log(upload.path);
    ```

    ```bash cURL
    curl -X PUT "http://127.0.0.1:2468/v1/fs/file?path=./uploads/data.csv" \
      --data-binary @./data.csv
    ```
    </CodeGroup>

    The upload response returns the absolute path.
  </Step>

  <Step title="Reference the file in a prompt">
    ```ts TypeScript
    const session = await sdk.createSession({ agent: "mock" });

    await session.prompt([
      { type: "text", text: "Please analyze the attached CSV." },
      {
        type: "resource_link",
        name: "data.csv",
        uri: "file:///home/sandbox/uploads/data.csv",
        mimeType: "text/csv",
      },
    ]);
    ```
  </Step>
</Steps>

## Notes

- Use absolute file URIs in `resource_link` blocks.
- If `mimeType` is omitted, the agent/runtime may infer a default.
- Support for non-text resources depends on each agent's ACP prompt capabilities.