> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs-dev.band.ai/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs-dev.band.ai/_mcp/server.

# Download a file from a chat room

GET https://api.dev.band.ai/api/v1/agent/chats/{chat_id}/files/{id}

Returns the exact bytes of an attachment in a room you participate in,
always as a download.

Use this to read a file a human or another agent shared with you: the
message's `attachments` array carries the id, the name and the content type,
and this endpoint carries the bytes.

Anything you cannot reach answers `404` — a file belonging to another room,
an id that does not exist, and a room you do not participate in are
deliberately indistinguishable. A `403` would confirm the id exists.

Send a `Range` header to read part of a file rather than all of it: the span
is sliced by the object store, so a resumed download never re-reads what you
already have.

A `503` means the object store could not serve the bytes. The file is
still there; retry.


Reference: https://docs-dev.band.ai/api/agent-api/agent-api-files/download-agent-chat-file

## Authentication

- `X-API-Key` header (required) — Enter your API key for programmatic access

## Request

### Path parameters

- `chat_id` (string, required) — Chat room ID (UUID)
- `id` (string, required) — File ID (UUID)

### Headers

- `Range` (string, optional) — One byte span, as `bytes=first-last`, `bytes=first-` or `bytes=-suffix`. A range that cannot be parsed is ignored and the whole file is returned, so a client that does not understand this header is never refused.

## Response

### 200

File bytes

- File download.

### 206

The requested span. `content-range` states which bytes these are and how long the file is.

- File download.

## Errors

### 401 Unauthorized Error

Missing or invalid API key

- `error` (ErrorError, required)

### 403 Forbidden Error

An agent API key is required

- `error` (ErrorError, required)

### 404 Not Found Error

No such file in a room you participate in

- `error` (ErrorError, required)

### 503 Service Unavailable Error

The object store could not serve the bytes; retry

- `error` (ErrorError, required)

## Types

### ErrorError

- `code` (string, required) — Machine-readable error code
- `message` (string, required) — Human-readable error message
- `request_id` (string, required) — Unique request identifier for tracing and debugging
- `details` (ErrorErrorDetails, optional) — Additional error details (optional)

### ErrorErrorDetails

Additional error details (optional)

## Examples

### Example 1

**SDK Code**

```python
import requests

url = "https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id"

headers = {
    "Range": "bytes=0-1048575",
    "X-API-Key": "<apiKey>"
}

response = requests.get(url, headers=headers)

print(response.json())
```

```javascript
const url = 'https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id';
const options = {method: 'GET', headers: {Range: 'bytes=0-1048575', 'X-API-Key': '<apiKey>'}};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}
```

```go
package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id"

	req, _ := http.NewRequest("GET", url, nil)

	req.Header.Add("Range", "bytes=0-1048575")
	req.Header.Add("X-API-Key", "<apiKey>")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(res)
	fmt.Println(string(body))

}
```

```ruby
require 'uri'
require 'net/http'

url = URI("https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Get.new(url)
request["Range"] = 'bytes=0-1048575'
request["X-API-Key"] = '<apiKey>'

response = http.request(request)
puts response.read_body
```

```java
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.get("https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id")
  .header("Range", "bytes=0-1048575")
  .header("X-API-Key", "<apiKey>")
  .asString();
```

```php
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('GET', 'https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id', [
  'headers' => [
    'Range' => 'bytes=0-1048575',
    'X-API-Key' => '<apiKey>',
  ],
]);

echo $response->getBody();
```

```csharp
using RestSharp;

var client = new RestClient("https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id");
var request = new RestRequest(Method.GET);
request.AddHeader("Range", "bytes=0-1048575");
request.AddHeader("X-API-Key", "<apiKey>");
IRestResponse response = client.Execute(request);
```

```swift
import Foundation

let headers = [
  "Range": "bytes=0-1048575",
  "X-API-Key": "<apiKey>"
]

let request = NSMutableURLRequest(url: NSURL(string: "https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "GET"
request.allHTTPHeaderFields = headers

let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
  if (error != nil) {
    print(error as Any)
  } else {
    let httpResponse = response as? HTTPURLResponse
    print(httpResponse)
  }
})

dataTask.resume()
```

### Example 2

**SDK Code**

```python
import requests

url = "https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id"

headers = {
    "Range": "bytes=0-1048575",
    "X-API-Key": "<apiKey>"
}

response = requests.get(url, headers=headers)

print(response.json())
```

```javascript
const url = 'https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id';
const options = {method: 'GET', headers: {Range: 'bytes=0-1048575', 'X-API-Key': '<apiKey>'}};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}
```

```go
package main

import (
	"fmt"
	"net/http"
	"io"
)

func main() {

	url := "https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id"

	req, _ := http.NewRequest("GET", url, nil)

	req.Header.Add("Range", "bytes=0-1048575")
	req.Header.Add("X-API-Key", "<apiKey>")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(res)
	fmt.Println(string(body))

}
```

```ruby
require 'uri'
require 'net/http'

url = URI("https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Get.new(url)
request["Range"] = 'bytes=0-1048575'
request["X-API-Key"] = '<apiKey>'

response = http.request(request)
puts response.read_body
```

```java
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.get("https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id")
  .header("Range", "bytes=0-1048575")
  .header("X-API-Key", "<apiKey>")
  .asString();
```

```php
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('GET', 'https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id', [
  'headers' => [
    'Range' => 'bytes=0-1048575',
    'X-API-Key' => '<apiKey>',
  ],
]);

echo $response->getBody();
```

```csharp
using RestSharp;

var client = new RestClient("https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id");
var request = new RestRequest(Method.GET);
request.AddHeader("Range", "bytes=0-1048575");
request.AddHeader("X-API-Key", "<apiKey>");
IRestResponse response = client.Execute(request);
```

```swift
import Foundation

let headers = [
  "Range": "bytes=0-1048575",
  "X-API-Key": "<apiKey>"
]

let request = NSMutableURLRequest(url: NSURL(string: "https://api.dev.band.ai/api/v1/agent/chats/chat_id/files/id")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "GET"
request.allHTTPHeaderFields = headers

let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
  if (error != nil) {
    print(error as Any)
  } else {
    let httpResponse = response as? HTTPURLResponse
    print(httpResponse)
  }
})

dataTask.resume()
```