Update examples for the 2026-07-28 era
## Motivation and Context The runnable examples drifted from the SDK they ship with: - POST requests whose `Accept` header does not cover both `application/json` and `text/event-stream` are answered 406, so the cURL walkthroughs no longer worked as printed. - `MCP::Client#connect` now defaults to `mode: :auto`, which adopts the sessionless modern lifecycle (2026-07-28) against a dual-era server; the Streamable HTTP client example requires a session and broke against its own server. - POST responses on an established session arrive as an SSE stream, which the hand-rolled HTTP client did not parse. - `notification_tool` claimed to send SSE notifications but only returned a `Tool::Response`. - `http_client.rb` read a resource URI the server never registered and skipped `notifications/initialized`. Handshake examples now offer the latest handshake protocol version (`2025-11-25`) instead of `2024-11-05`, the Streamable HTTP client pins `mode: :legacy` for its session-based demo, `notification_tool` reports real `notifications/progress` events requested through `_meta.progressToken`, and the interactive client streams those events from the POST response so they are visible on screen. The modern lifecycle itself had no runnable example, so a new server and client pair (`modern_http_server.rb`, `modern_http_client.rb`) shows the sessionless flow end to end: `server/discover` capability discovery, the per-request `_meta` envelope with the `Mcp-Method` and `Mcp-Name` headers (stamped by the SDK client automatically), `resultType` stamping, SEP-2549 cache hints, a SEP-2322 multi round-trip `deploy` tool resumed automatically by the client's elicitation handler, and the removal of legacy-only methods such as `ping`. The same server keeps serving the legacy `initialize` flow, routed per request by the `MCP-Protocol-Version` header. `examples/README.md` documents the pair and adds a cURL walkthrough covering the modern headers, the envelope, and the multi round-trip exchange. ## How Has This Been Tested? - `ruby examples/stdio_client.rb` against `stdio_server.rb` - `ruby examples/http_client.rb` against `http_server.rb` - `ruby examples/streamable_http_client.rb` against `streamable_http_server.rb`, including the progress stream - `ruby examples/modern_http_client.rb` against `modern_http_server.rb` (discover, modern adoption, cache hints, `resultType`, the multi round-trip resume, `ping` rejection) - The cURL walkthroughs in the banners and `examples/README.md`, including the `requestState` echo and a legacy `initialize` against the modern example server ## Breaking Changes None.
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Koichi ITO
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1 changed files with 501 additions and 51 deletions
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@ -13,14 +13,16 @@ sse_logger.formatter = proc do |severity, datetime, _progname, msg|
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"[SSE] #{severity} #{datetime.strftime("%H:%M:%S.%L")} - #{msg}\n"
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end
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# Tool that returns a response that will be sent via SSE if a stream is active
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# Tool that emits `notifications/progress` events, delivered over the SSE stream.
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# The client must request them by sending a `progressToken` in the request `_meta`.
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class NotificationTool < MCP::Tool
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tool_name "notification_tool"
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description "Returns a notification message that will be sent via SSE if stream is active"
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description "Sends the message back as progress notifications via SSE, then returns a summary"
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input_schema(
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properties: {
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message: { type: "string", description: "Message to send via SSE" },
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delay: { type: "number", description: "Delay in seconds before returning (optional)" },
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steps: { type: "number", description: "Number of progress notifications to send (default: 3)" },
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delay: { type: "number", description: "Delay in seconds between notifications (optional)" },
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},
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required: ["message"],
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)
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@ -28,14 +30,19 @@ class NotificationTool < MCP::Tool
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class << self
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attr_accessor :logger
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def call(message:, delay: 0)
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sleep(delay) if delay > 0
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def call(message:, server_context:, steps: 3, delay: 0)
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steps = steps.to_i.clamp(1, 10)
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logger&.info("Returning notification message: #{message}")
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steps.times do |i|
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sleep(delay) if delay > 0
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logger&.info("Reporting progress #{i + 1}/#{steps}: #{message}")
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server_context.report_progress(i + 1, total: steps, message: message)
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end
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MCP::Tool::Response.new([{
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type: "text",
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text: "Notification: #{message} (timestamp: #{Time.now.iso8601})",
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text: "Sent #{steps} progress notifications for: #{message}",
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}])
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end
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end
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@ -44,6 +51,7 @@ end
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# Create the server
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server = MCP::Server.new(
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name: "sse_test_server",
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version: "1.0.0",
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tools: [NotificationTool],
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prompts: [],
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resources: [],
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@ -149,29 +157,34 @@ puts <<~MESSAGE
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Starting server on http://localhost:9393
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Available Tools:
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1. NotificationTool - Returns messages that are sent via SSE when stream is active"
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1. notification_tool - Sends the message back as progress notifications via SSE
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2. echo - Simple echo tool
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Testing SSE:
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1. Initialize session:
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curl -i http://localhost:9393 \\
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--json '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"sse-test","version":"1.0"}}}'
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-H "Accept: application/json, text/event-stream" \\
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--json '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"protocolVersion":"2025-11-25","capabilities":{},"clientInfo":{"name":"sse-test","version":"1.0"}}}'
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2. Connect SSE stream (use the session ID from step 1):"
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2. Connect SSE stream (use the session ID from step 1):
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curl -i -N -H "Mcp-Session-Id: YOUR_SESSION_ID" http://localhost:9393
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3. In another terminal, test tools (responses will be sent via SSE if stream is active):
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Echo tool:
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curl -i http://localhost:9393 -H "Mcp-Session-Id: YOUR_SESSION_ID" \\
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-H "Accept: application/json, text/event-stream" \\
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--json '{"jsonrpc":"2.0","method":"tools/call","id":2,"params":{"name":"echo","arguments":{"message":"Hello SSE!"}}}'
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Notification tool (with 2 second delay):
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Notification tool (progress notifications require a progressToken in _meta):
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curl -i http://localhost:9393 -H "Mcp-Session-Id: YOUR_SESSION_ID" \\
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--json '{"jsonrpc":"2.0","method":"tools/call","id":3,"params":{"name":"notification_tool","arguments":{"message":"Hello SSE!", "delay": 2}}}'
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-H "Accept: application/json, text/event-stream" \\
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--json '{"jsonrpc":"2.0","method":"tools/call","id":3,"params":{"name":"notification_tool","arguments":{"message":"Hello SSE!","delay":1},"_meta":{"progressToken":"curl-progress"}}}'
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Note: When an SSE stream is active, tool responses will appear in the SSE stream and the POST request will return 202 Accepted with no body.
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Note: Each POST is answered with an SSE stream of its own; request-scoped notifications
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(such as the progress events above) appear on it before the final response.
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The standalone GET stream carries server-initiated messages that are not tied to a request.
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Press Ctrl+C to stop the server
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MESSAGE
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