@@ -98,7 +98,7 @@ A specialized HTTP server designed to test and demonstrate Server-Sent Events (S
 
 **Available Tools:**
 
-- `notification_tool` - Send custom SSE notifications with optional delays
+- `notification_tool` - Sends progress notifications over SSE, with optional delays
 - `echo` - Simple echo tool for basic testing
 
 **Usage:**
@@ -124,14 +124,15 @@ An interactive client that connects to the SSE stream and provides a menu-driven
 
 1. Start the SSE test server in one terminal:
 
-   ```console
-   $ ruby examples/streamable_http_server.rb
-   ```
+```console
+$ ruby examples/streamable_http_server.rb
+```
 
 2. Run the SSE test client in another terminal:
-   ```console
-   $ ruby examples/streamable_http_client.rb
-   ```
+
+```console
+$ ruby examples/streamable_http_client.rb
+```
 
 The client will:
 
@@ -155,6 +156,34 @@ $ bundle exec puma --port 9292
 
 The MCP endpoint is available at `http://localhost:9292/mcp`. See [`rails/README.md`](rails/README.md) for a full curl-based walkthrough.
 
+### 8. Modern Lifecycle HTTP Server / Client (`modern_http_server.rb`, `modern_http_client.rb`)
+
+A server and client pair demonstrating the 2026-07-28 modern lifecycle (SEP-2575), which replaces the `initialize` handshake and per-session state with sessionless, self-contained requests.
+
+**Features:**
+
+- `server/discover` capability discovery before (or instead of) a handshake
+- The per-request `_meta` envelope and `Mcp-Method` / `Mcp-Name` headers, stamped by the SDK automatically
+- `resultType` stamping and SEP-2549 cache hints (`ttlMs`, `cacheScope`) on results
+- A multi round-trip `deploy` tool (SEP-2322), resumed automatically by the client's elicitation handler
+- The removal of legacy-only methods such as `ping`
+
+**Usage:**
+
+1. Start the server in one terminal:
+
+```console
+$ ruby examples/modern_http_server.rb
+```
+
+2. Run the client in another terminal:
+
+```console
+$ ruby examples/modern_http_client.rb
+```
+
+The same server still accepts the legacy `initialize` flow: the transport routes each request to the legacy or modern lifecycle by its `MCP-Protocol-Version` header.
+
 ### Testing with MCP Inspector
 
 [MCP Inspector](https://modelcontextprotocol.io/docs/tools/inspector) is a browser-based tool for testing and debugging MCP servers.
@@ -188,24 +217,78 @@ You can also test SSE functionality manually using cURL:
 
 ```console
 SESSION_ID=$(curl -D - -s -o /dev/null http://localhost:9393 \
-  --json '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"curl-test","version":"1.0"}}}' | grep -i "Mcp-Session-Id:" | cut -d' ' -f2- | tr -d '\r')
+  -H "Accept: application/json, text/event-stream" \
+  --json '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2025-11-25","capabilities":{},"clientInfo":{"name":"curl-test","version":"1.0"}}}' | grep -i "Mcp-Session-Id:" | cut -d' ' -f2- | tr -d '\r')
 ```
 
-2. Connect to SSE stream (in one terminal):
+2. Optionally connect the standalone SSE stream, which carries server-initiated messages that are not tied to a request (in another terminal):
 
 ```console
 curl -i -N -H "Mcp-Session-Id: $SESSION_ID" http://localhost:9393
 ```
 
-3. Trigger notifications (in another terminal):
+3. Call the notification tool. The `notifications/progress` events (requested via the `progressToken` in `_meta`) and the final response arrive as SSE events on the POST response itself:
 
 ```console
-# Send immediate notification
 curl -i http://localhost:9393 \
+  -H "Accept: application/json, text/event-stream" \
   -H "Mcp-Session-Id: $SESSION_ID" \
-  --json '{"jsonrpc":"2.0","method":"tools/call","id":2,"params":{"name":"notification_tool","arguments":{"message":"Hello from cURL!"}}}'
+  --json '{"jsonrpc":"2.0","method":"tools/call","id":2,"params":{"name":"notification_tool","arguments":{"message":"Hello from cURL!","delay":0.5},"_meta":{"progressToken":"curl-progress"}}}'
+```
+
+### Testing the modern lifecycle with cURL
+
+The modern lifecycle (2026-07-28, SEP-2575) is sessionless: there is no `initialize` handshake and no `Mcp-Session-Id`. Start `examples/modern_http_server.rb` and walk it manually:
+
+1. Probe capabilities with `server/discover`:
+
+```console
+curl -s http://localhost:9494 \
+  -H "Accept: application/json, text/event-stream" \
+  --json '{"jsonrpc":"2.0","id":0,"method":"server/discover"}'
+```
+
+2. List tools (the `MCP-Protocol-Version` header selects the era, `Mcp-Method` mirrors the method, and `params._meta` carries the SEP-2575 envelope):
+
+```console
+curl -s http://localhost:9494 \
+  -H "Accept: application/json, text/event-stream" \
+  -H "MCP-Protocol-Version: 2026-07-28" \
+  -H "Mcp-Method: tools/list" \
+  --json '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{"_meta":{"io.modelcontextprotocol/protocolVersion":"2026-07-28","io.modelcontextprotocol/clientCapabilities":{}}}}'
+```
+
+3. Call a tool (name-bearing methods additionally mirror the name in the `Mcp-Name` header):
+
+```console
+curl -s http://localhost:9494 \
+  -H "Accept: application/json, text/event-stream" \
+  -H "MCP-Protocol-Version: 2026-07-28" \
+  -H "Mcp-Method: tools/call" \
+  -H "Mcp-Name: greet" \
+  --json '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"greet","arguments":{"name":"curl"},"_meta":{"io.modelcontextprotocol/protocolVersion":"2026-07-28","io.modelcontextprotocol/clientCapabilities":{}}}}'
 ```
 
+4. Observe a multi round-trip result (SEP-2322), then resume it by echoing the `requestState` back together with the answer. Declaring the `elicitation` capability in the envelope is required before the server may embed elicitation requests:
+
+```console
+curl -s http://localhost:9494 \
+  -H "Accept: application/json, text/event-stream" \
+  -H "MCP-Protocol-Version: 2026-07-28" \
+  -H "Mcp-Method: tools/call" \
+  -H "Mcp-Name: deploy" \
+  --json '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"deploy","arguments":{"app":"storefront"},"_meta":{"io.modelcontextprotocol/protocolVersion":"2026-07-28","io.modelcontextprotocol/clientCapabilities":{"elicitation":{}}}}}'
+
+curl -s http://localhost:9494 \
+  -H "Accept: application/json, text/event-stream" \
+  -H "MCP-Protocol-Version: 2026-07-28" \
+  -H "Mcp-Method: tools/call" \
+  -H "Mcp-Name: deploy" \
+  --json '{"jsonrpc":"2.0","id":4,"method":"tools/call","params":{"name":"deploy","arguments":{"app":"storefront"},"inputResponses":{"environment":{"action":"accept","content":{"environment":"staging"}}},"requestState":"{\"app\":\"storefront\"}","_meta":{"io.modelcontextprotocol/protocolVersion":"2026-07-28","io.modelcontextprotocol/clientCapabilities":{"elicitation":{}}}}}'
+```
+
+The same server still accepts the legacy flow from the previous sections, routed by the `MCP-Protocol-Version` header.
+
 ## Streamable HTTP Transport Details
 
 ### Protocol Flow
@@ -236,13 +319,15 @@ Initialize a session:
 
 ```console
 curl -i http://localhost:9292 \
-  --json '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}'
+  -H "Accept: application/json, text/event-stream" \
+  --json '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2025-11-25","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}'
 ```
 
 List tools (using the session ID from initialization):
 
 ```console
 curl -i http://localhost:9292 \
+  -H "Accept: application/json, text/event-stream" \
   -H "Mcp-Session-Id: YOUR_SESSION_ID" \
   --json '{"jsonrpc":"2.0","method":"tools/list","id":2}'
 ```
@@ -251,6 +336,7 @@ Call a tool:
 
 ```console
 curl -i http://localhost:9292 \
+  -H "Accept: application/json, text/event-stream" \
   -H "Mcp-Session-Id: YOUR_SESSION_ID" \
   --json '{"jsonrpc":"2.0","method":"tools/call","id":3,"params":{"name":"example_tool","arguments":{"a":5,"b":3}}}'
 ```
@@ -4,7 +4,7 @@
 require "json"
 require "uri"
 
-# Simple HTTP client example for interacting with the MCP HTTP server
+# Simple HTTP client example for interacting with the MCP HTTP server.
 class MCPHTTPClient
   def initialize(base_url = "http://localhost:9292")
     @base_url = base_url
@@ -30,19 +30,51 @@ def send_request(method, params = nil, id = nil)
 
     response = http.request(request)
 
-    # Store session ID if provided
+    # Store session ID if provided.
     if response["Mcp-Session-Id"]
       @session_id = response["Mcp-Session-Id"]
       puts "Session ID: #{@session_id}"
     end
 
-    JSON.parse(response.body)
+    parse_response_body(response)
+  end
+
+  # In the transport's default SSE mode, POST responses on an established session arrive as
+  # a Server-Sent Events stream whose `data:` line carries the JSON-RPC response; unwrap it
+  # before parsing.
+  def parse_response_body(response)
+    body = response.body
+
+    if response["Content-Type"]&.start_with?("text/event-stream")
+      data_lines = body.lines.select { |line| line.start_with?("data:") }
+      body = data_lines.map { |line| line.sub(/\Adata:\s*/, "") }.join
+    end
+
+    JSON.parse(body)
+  end
+
+  def send_notification(method, params = nil)
+    uri = URI(@base_url)
+    http = Net::HTTP.new(uri.host, uri.port)
+
+    request = Net::HTTP::Post.new(uri.path.empty? ? "/" : uri.path)
+    request["Content-Type"] = "application/json"
+    request["Mcp-Session-Id"] = @session_id if @session_id
+
+    # Notifications carry no `id` and receive no JSON-RPC response body.
+    request.body = {
+      jsonrpc: "2.0",
+      method: method,
+      params: params,
+    }.compact.to_json
+
+    http.request(request)
   end
 
   def initialize_session
     puts "=== Initializing session ==="
     result = send_request("initialize", {
-      protocolVersion: "2024-11-05",
+      protocolVersion: "2025-11-25",
       capabilities: {},
       clientInfo: {
         name: "example_client",
@@ -54,6 +86,14 @@ def initialize_session
     result
   end
 
+  def notify_initialized
+    puts "=== Sending notifications/initialized ==="
+    response = send_notification("notifications/initialized")
+    puts "Response status: #{response.code} #{response.message}"
+
+    response
+  end
+
   def ping
     puts "=== Sending ping ==="
     result = send_request("ping")
@@ -147,37 +187,40 @@ def main
   client = MCPHTTPClient.new
 
   begin
-    # Initialize session
+    # Initialize session.
     client.initialize_session
 
-    # Test ping
+    # Complete the handshake.
+    client.notify_initialized
+
+    # Test ping.
     client.ping
 
-    # List available tools
+    # List available tools.
     client.list_tools
 
-    # Call the example_tool (note: snake_case name)
+    # Call the example_tool (note: snake_case name).
     client.call_tool("example_tool", { a: 5, b: 3 })
 
-    # Call the echo tool
+    # Call the echo tool.
     client.call_tool("echo", { message: "Hello from client!" })
 
-    # List prompts
+    # List prompts.
     client.list_prompts
 
-    # Get a prompt (note: snake_case name)
+    # Get a prompt (note: snake_case name).
     client.get_prompt("example_prompt", { message: "This is a test message" })
 
-    # List resources
+    # List resources.
     client.list_resources
 
-    # Read a resource
-    client.read_resource("test_resource")
+    # Read a resource (the URI registered by http_server.rb).
+    client.read_resource("https://test_resource.invalid")
   rescue => e
     puts "Error: #{e.message}"
     puts e.backtrace
   ensure
-    # Clean up session
+    # Clean up session.
     client.close_session
   end
 end
 
@@ -56,6 +56,7 @@ def template(args, server_context:)
 # Set up the server
 server = MCP::Server.new(
   name: "example_http_server",
+  version: "1.0.0",
   tools: [ExampleTool],
   prompts: [ExamplePrompt],
   resources: [
@@ -169,7 +170,9 @@ def call(env)
   Starting MCP HTTP server on http://localhost:9292
   Use POST requests to initialize and send JSON-RPC commands
   Example initialization:
-    curl -i http://localhost:9292 --json '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}'
+    curl -i http://localhost:9292 \\
+      -H "Accept: application/json, text/event-stream" \\
+      --json '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2025-11-25","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}'
 
   The server will return a session ID in the Mcp-Session-Id header.
   Use this session ID for subsequent requests.