Account for bypassing of initialization

Author: Zachary German

docs/specification/draft/basic/lifecycle.mdx

@@ -39,7 +39,9 @@ sequenceDiagram
 
 ### Initialization
 
-The initialization phase **MUST** be the first interaction between client and server.
+The initialization phase **SHOULD** be the first interaction between client and server.
+Bypassing initialization is appropriate when the client has prior knowledge of, and accounts for,
+the protocol versions, capabilities, and initialization bypass support of all servers it interacts with.
 During this phase, the client and server:
 
 - Establish protocol version compatibility

docs/specification/draft/basic/transports.mdx

@@ -172,12 +172,10 @@ act as a cursor within that particular stream.
 ### Session Management
 
 An MCP "session" consists of logically related interactions between a client and a
-server, beginning with the [initialization phase](/specification/draft/basic/lifecycle). To support
-servers which want to establish stateful sessions:
+server. To support servers which want to establish stateful sessions:
 
-1. A server using the Streamable HTTP transport **MAY** assign a session ID at
-   initialization time, by including it in an `Mcp-Session-Id` header on the HTTP
-   response containing the `InitializeResult`.
+1. A server using the Streamable HTTP transport **MAY** assign a session ID by including
+   it in an `Mcp-Session-Id` header on any HTTP response.
    - The session ID **SHOULD** be globally unique and cryptographically secure (e.g., a
      securely generated UUID, a JWT, or a cryptographic hash).
    - The session ID **MUST** only contain visible ASCII characters (ranging from 0x21 to
@@ -190,7 +188,8 @@ servers which want to establish stateful sessions:
 3. The server **MAY** terminate the session at any time, after which it **MUST** respond
    to requests containing that session ID with HTTP 404 Not Found.
 4. When a client receives HTTP 404 in response to a request containing an
-   `Mcp-Session-Id`, it **MUST** start a new session by sending a new `InitializeRequest`
+   `Mcp-Session-Id` obtained through an [initialization phase](/specification/draft/basic/lifecycle),
+   it **SHOULD** start a new session by sending a new `InitializeRequest`
    without a session ID attached.
 5. Clients that no longer need a particular session (e.g., because the user is leaving
    the client application) **SHOULD** send an HTTP DELETE to the MCP endpoint with the