event docs message id event emitter

docs/features/plugin/development/events.mdx

@@ -30,7 +30,7 @@ Events are **fully available** for native Python Tools and Functions defined dir
 
 ### External Tools (OpenAPI & MCP)
 
-External tools can emit events via a **dedicated REST endpoint**. Open WebUI passes the following headers to all external tool requests:
+External tools can emit events via a **dedicated REST endpoint**. Open WebUI passes the following headers to all external tool requests when `ENABLE_FORWARD_USER_INFO_HEADERS=True` is set:
 
 | Header | Description |
 |--------|-------------|
@@ -467,14 +467,24 @@ Yes—emit `"chat:message:delta"` events in a loop, then finish with `"chat:mess
 
 External tools (OpenAPI and MCP servers) can emit events to the Open WebUI UI via a REST endpoint. This enables features like status updates, notifications, and streaming content from tools running on external servers.
 
+### Prerequisites
+
+To receive the chat and message ID headers, you must enable header forwarding by setting the following environment variable on your Open WebUI instance:
+
+```
+ENABLE_FORWARD_USER_INFO_HEADERS=True
+```
+
+Without this, Open WebUI will not include the identification headers in requests to external tools, and event emitting will not work.
+
 ### Headers Provided by Open WebUI
 
-When Open WebUI calls your external tool, it includes these headers:
+When Open WebUI calls your external tool (with header forwarding enabled), it includes these headers:
 
-| Header | Description |
-|--------|-------------|
-| `X-Open-WebUI-Chat-Id` | The chat ID where the tool was invoked |
-| `X-Open-WebUI-Message-Id` | The message ID associated with the tool call |
+| Header | Description | Env Var Override |
+|--------|-------------|------------------|
+| `X-Open-WebUI-Chat-Id` | The chat ID where the tool was invoked | `FORWARD_SESSION_INFO_HEADER_CHAT_ID` |
+| `X-Open-WebUI-Message-Id` | The message ID associated with the tool call | `FORWARD_SESSION_INFO_HEADER_MESSAGE_ID` |
 
 ### Event Endpoint
 

docs/getting-started/env-configuration.mdx

@@ -1357,8 +1357,9 @@ If enabled, the following headers are forwarded:
   - `X-OpenWebUI-User-Email`
   - `X-OpenWebUI-User-Role`
   - `X-OpenWebUI-Chat-Id`
+  - `X-OpenWebUI-Message-Id`
 
-This enables per-user authorization, auditing, rate limiting, and request tracing on external services.
+This enables per-user authorization, auditing, rate limiting, and request tracing on external services. The chat and message ID headers are also required for [external tool event emitting](/features/plugin/development/events#-external-tool-events).
 
 #### `FORWARD_USER_INFO_HEADER_USER_NAME`
 
@@ -1390,6 +1391,12 @@ This enables per-user authorization, auditing, rate limiting, and request tracin
 - Default: `X-OpenWebUI-Chat-Id`
 - Description: Customizes the header name used to forward the current chat/session ID.
 
+#### `FORWARD_SESSION_INFO_HEADER_MESSAGE_ID`
+
+- Type: `str`
+- Default: `X-OpenWebUI-Message-Id`
+- Description: Customizes the header name used to forward the current message ID. This header is required for [external tool event emitting](/features/plugin/development/events#-external-tool-events).
+
 :::tip Custom Header Prefix
 Use these variables when integrating with services that require specific header naming conventions. For example, AWS Bedrock AgentCore requires headers prefixed with `X-Amzn-Bedrock-AgentCore-Runtime-Custom-`:
 
@@ -1399,6 +1406,7 @@ FORWARD_USER_INFO_HEADER_USER_ID=X-Amzn-Bedrock-AgentCore-Runtime-Custom-User-Id
 FORWARD_USER_INFO_HEADER_USER_EMAIL=X-Amzn-Bedrock-AgentCore-Runtime-Custom-User-Email
 FORWARD_USER_INFO_HEADER_USER_ROLE=X-Amzn-Bedrock-AgentCore-Runtime-Custom-User-Role
 FORWARD_SESSION_INFO_HEADER_CHAT_ID=X-Amzn-Bedrock-AgentCore-Runtime-Custom-Chat-Id
+FORWARD_SESSION_INFO_HEADER_MESSAGE_ID=X-Amzn-Bedrock-AgentCore-Runtime-Custom-Message-Id
 ```
 :::