---
title: A2A Agent
slug: /a2a-agent-component
---

:::tip
As of Langflow 1.11.x, A2A support is **off** by default. To enable it, set the following environment variable before starting Langflow:

```bash
LANGFLOW_A2A_ENABLED=true
```

`LANGFLOW_A2A_ENABLED` enables Langflow's A2A server endpoints. Set it when you [publish Langflow flows as A2A agents](./a2a-server#publish-a-flow-as-an-a2a-agent), or when you use **Internal** mode to call those published flows. You do **not** need it to call a remote agent in **External** mode.
:::

The **A2A Agent** component calls an [Agent2Agent (A2A)](https://a2a-protocol.org/) agent and returns its reply.

Use **Internal** mode to call published A2A agent flows within the same Langflow [project](/concepts-flows#projects), or use **External** mode to call a remote A2A agent by its published URL.

For more information on publishing a Langflow flow, see [Publish a flow as an A2A agent](./a2a-server#publish-a-flow-as-an-a2a-agent).

## Use Internal mode in a flow

1. Add an **A2A Agent** component to your flow.
2. In the **A2A Agent** component, set **Mode** to **Internal**.
3. In **Agent**, select a published A2A agent flow within your Langflow [project](/concepts-flows#projects). The flow must have [**Chat Input** and **Chat Output** components](./chat-input-and-output). For more information, see [Publish a flow as an A2A agent](./a2a-server#publish-a-flow-as-an-a2a-agent).
4. Connect a [**Chat Input** component](./chat-input-and-output#chat-input) to the **A2A Agent** component's **Message** input.
5. Connect the **Response** output to the next component in your flow, such as a [**Chat Output** component](./chat-input-and-output#chat-output).

## Use External mode in a flow

1. Add an **A2A Agent** component to your flow.
2. In the **A2A Agent** component, set **Mode** to **External**.
3. Enter the remote agent's base URL in the **Agent URL** field.
Alternatively, enter the agent's `/.well-known/agent-card.json` card URL in the **Agent URL** field.
Both options resolve the same agent.
When the URL returns a card, the component displays a read-only **Agent card** preview.
4. Optional: If the remote agent requires `x-api-key` authentication, enter the API key in the **API Key** field, or use a [global variable](./configuration-global-variables).
5. Connect a [**Chat Input** component](./chat-input-and-output#chat-input) to the **A2A Agent** component's **Message** input.
6. Connect the **Response** output to the next component in your flow, such as a [**Chat Output** component](./chat-input-and-output#chat-output).

### Local and private agent URLs

Langflow enables [SSRF protection](./api-keys-and-authentication#ssrf-protection) by default.
Loopback and private addresses such as `localhost`, `127.0.0.1`, and `::1` are blocked unless you allow them.

If the remote agent URL points at a local or private host, such as another Langflow instance on `http://localhost:7862`, set `LANGFLOW_SSRF_ALLOWED_HOSTS` on the Langflow instance that runs the **A2A Agent** component. The allowlist takes hostnames and not full URLs. For example:

```bash
export LANGFLOW_SSRF_ALLOWED_HOSTS=localhost,127.0.0.1
```
Restart Langflow after changing the variable.

For more information, see [SSRF protection](./api-keys-and-authentication#ssrf-protection).

## A2A Agent parameters

| Name | Type | Description |
|------|------|-------------|
| mode | Tab | Input parameter. **Internal** calls another agent flow in this project. **External** calls a remote A2A agent by URL. Default: `External`. |
| agent_name_selected | Dropdown | Input parameter. **Internal** mode only. An agent flow in this project (one with [**Chat Input** and **Chat Output** components](./chat-input-and-output)). |
| agent_url | String | Input parameter. **External** mode only. The remote A2A agent's base URL or `/.well-known/agent-card.json` card URL. |
| agent_card | Data display | Input parameter. **External** mode only. Read-only preview of the remote agent's advertised card. Appears when the URL returns a card. |
| input_value | String | Input parameter. The message to send to the agent. Supports **Tool Mode**. |
| api_key | Secret string | Input parameter. **External** mode only. Optional API key sent as `x-api-key` for agents that require it. |
| timeout | Integer | Input parameter. **External** mode only. Maximum seconds to wait for the agent's reply. Default: `60`. |
| response | Message | Output parameter. The agent's reply text. |

## See also

* [Use Langflow as an A2A agent](./a2a-server)
* [SSRF protection](./api-keys-and-authentication#ssrf-protection)
* [Agent2Agent protocol](https://a2a-protocol.org/)