Merge branch 'main' into add-tuui-client

Author: aiqlcom

docs/docs/concepts/transports.mdx

@@ -129,6 +129,14 @@ Use stdio when:
 
 ### Server-Sent Events (SSE)
 
+<Warning>
+
+The SSE Transport has been [**replaced**](http://modelcontextprotocol.io/specification/2025-03-26/changelog#major-changes) with a more
+flexible [Streamable HTTP](http://modelcontextprotocol.io/specification/2025-03-26/basic/transports) transport. Refer to the [Specification](http://modelcontextprotocol.io/specification/2025-03-26/basic/transports)
+and latest SDKs for the most recent information.
+
+</Warning>
+
 SSE transport enables server-to-client streaming with HTTP POST requests for client-to-server communication.
 
 Use SSE when:

docs/specification/draft/basic/lifecycle.mdx

@@ -138,15 +138,12 @@ supports. This **SHOULD** be the _latest_ version supported by the server.
 If the client does not support the version in the server's response, it **SHOULD**
 disconnect.
 
+<Note>
 If using HTTP, the client **MUST** include the `MCP-Protocol-Version:
-<protocol-version>` HTTP header during any subsequent requests to the MCP
-server, allowing the MCP server to respond based on the MCP protocol version.
-
-The protocol version sent by the client **SHOULD** be the one negotiated during [initialization](https://modelcontextprotocol.io/specification/draft/basic/lifecycle#initialization).
-
-If the server receives a request with a missing, invalid, or unsupported
-MCP-Protocol-VERSION, it **MUST** respond with `400 Bad Request`.
-For example: `MCP-Protocol-Version: 2024-11-05`
+<protocol-version>` HTTP header on all subsequent requests to the MCP
+server.
+For details, see [the Protocol Version Header section in Transports](/specification/draft/basic/transports#protocol-version-header).
+</Note>
 
 #### Capability Negotiation
 

docs/specification/draft/basic/transports.mdx

@@ -237,6 +237,25 @@ sequenceDiagram
 
 ```
 
+### Protocol Version Header
+
+If using HTTP, the client **MUST** include the `MCP-Protocol-Version:
+<protocol-version>` HTTP header on all subsequent requests to the MCP
+server, allowing the MCP server to respond based on the MCP protocol version.
+
+For example: `MCP-Protocol-Version: 2025-03-26`
+
+The protocol version sent by the client **SHOULD** be the one [negotiated during
+initialization](/specification/draft/basic/lifecycle#version-negotiation).
+
+For backwards compatibility, if the server does _not_ receive an `MCP-Protocol-Version`
+header, and has no other way to identify the version - for example, by relying on the
+protocol version negotiated during initialization - the server **SHOULD** assume protocol
+version `2025-03-26`.
+
+If the server receives a request with an invalid or unsupported
+`MCP-Protocol-Version`, it **MUST** respond with `400 Bad Request`.
+
 ### Backwards Compatibility
 
 Clients and servers can maintain backwards compatibility with the deprecated [HTTP+SSE