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

# Headers

> Every header BundleUp reads or sends, and which APIs use it.

## Request headers

| Header | Proxy | Unified API | MCP | Platform API | Auth `/connection` | Description |
| - | :-: | :-: | :-: | :-: | :-: | - |
| `Authorization` | ✓ | ✓ | ✓ | ✓ | ✓ | `Bearer YOUR_API_KEY`. On the Proxy and MCP you can also send `Bearer YOUR_API_KEY.CONNECTION_ID` instead of a separate `BU-Connection-Id`. Never forwarded to the provider. |
| `BU-Connection-Id` | ✓ | ✓ (required) | ✓ | | | The connection to act on. Takes precedence over a connection ID appended to the API key. Never forwarded. |
| `BU-Max-Retries` | ✓ | ✓ | | | | Maximum retries for this request, `0` to `5`. Default `3`. Only idempotent methods are retried. Never forwarded. See [Retries](/docs/guides/proxy/retries). |
| `BU-Auth-Mode` | ✓ | | | | | **GitHub App connections only.** `user` (default) or `installation`, to act as the user or as the app installation. See the [GitHub App page](https://www.bundleup.io/integrations/github_app). Never forwarded. |

On the Proxy and MCP, every other request header is forwarded to the provider unchanged.

## Response headers

| Header | Sent by | Description |
| - | - | - |
| `Retry-After` | BundleUp, on its own `429` | `60`: seconds to wait before retrying on this connection. |
| Provider headers | Proxy, MCP | Everything the provider returned, unchanged: content type, rate-limit headers, pagination links, `Mcp-Session-Id` and so on. |

## Webhook headers

Sent by BundleUp on every [webhook](/docs/guides/webhooks/overview) delivery:

| Header | Description |
| - | - |
| `BundleUp-Signature` | Hex-encoded HMAC-SHA256 of the raw body, keyed with the webhook’s signing secret. See [Verifying signatures](/docs/guides/webhooks/verifying). |
| `BundleUp-Event` | The event name, for example `connection.created`. |
| `BundleUp-Workspace` | The workspace ID. |
| `Content-Type` | `application/json` |


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