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| 1 | +import { randomUUID } from 'node:crypto'; |
| 2 | + |
| 3 | +import type { JSONRPCMessage, MessageExtraInfo } from '@modelcontextprotocol/core'; |
| 4 | + |
| 5 | +import { McpServer } from '../../src/server/mcp.js'; |
| 6 | +import type { EventId, EventStore, StreamId } from '../../src/server/streamableHttp.js'; |
| 7 | +import { WebStandardStreamableHTTPServerTransport } from '../../src/server/streamableHttp.js'; |
| 8 | + |
| 9 | +/** |
| 10 | + * Gate-closure tests for the two protocol-version checks that guard |
| 11 | + * resumability behavior (priming events and `closeSSEStream` callbacks). |
| 12 | + * |
| 13 | + * The protocol version in an `initialize` request body is NOT validated |
| 14 | + * against `supportedProtocolVersions` (unlike the `MCP-Protocol-Version` |
| 15 | + * header), so these gates must be bounded: only versions the transport |
| 16 | + * instance actually supports may enable the resumability behavior introduced |
| 17 | + * with protocol version 2025-11-25. An unknown future version string must |
| 18 | + * behave like a client that does not support it. |
| 19 | + */ |
| 20 | + |
| 21 | +function initializeRequest(protocolVersion: string): Request { |
| 22 | + const body = { |
| 23 | + jsonrpc: '2.0', |
| 24 | + method: 'initialize', |
| 25 | + params: { |
| 26 | + clientInfo: { name: 'test-client', version: '1.0' }, |
| 27 | + protocolVersion, |
| 28 | + capabilities: {} |
| 29 | + }, |
| 30 | + id: 'init-1' |
| 31 | + } as JSONRPCMessage; |
| 32 | + |
| 33 | + return new Request('http://localhost/mcp', { |
| 34 | + method: 'POST', |
| 35 | + headers: { |
| 36 | + 'Content-Type': 'application/json', |
| 37 | + Accept: 'application/json, text/event-stream' |
| 38 | + }, |
| 39 | + body: JSON.stringify(body) |
| 40 | + }); |
| 41 | +} |
| 42 | + |
| 43 | +async function readFirstSSEChunk(response: Response): Promise<string> { |
| 44 | + const reader = response.body?.getReader(); |
| 45 | + const { value } = await reader!.read(); |
| 46 | + return new TextDecoder().decode(value); |
| 47 | +} |
| 48 | + |
| 49 | +/** |
| 50 | + * A priming event is an SSE event with an event ID and empty data, |
| 51 | + * e.g. `id: <eventId>\ndata: \n\n`. |
| 52 | + */ |
| 53 | +function isPrimingEvent(sseChunk: string): boolean { |
| 54 | + const lines = sseChunk.split('\n'); |
| 55 | + const dataLine = lines.find(line => line.startsWith('data:')); |
| 56 | + return lines.some(line => line.startsWith('id:')) && dataLine !== undefined && dataLine.slice(5).trim() === ''; |
| 57 | +} |
| 58 | + |
| 59 | +describe('WebStandardStreamableHTTPServerTransport - future-version gate closure', () => { |
| 60 | + let transport: WebStandardStreamableHTTPServerTransport; |
| 61 | + let mcpServer: McpServer; |
| 62 | + let storedEvents: Map<EventId, { streamId: StreamId; message: JSONRPCMessage }>; |
| 63 | + let capturedExtras: Array<MessageExtraInfo | undefined>; |
| 64 | + |
| 65 | + beforeEach(async () => { |
| 66 | + storedEvents = new Map(); |
| 67 | + capturedExtras = []; |
| 68 | + |
| 69 | + const eventStore: EventStore = { |
| 70 | + async storeEvent(streamId: StreamId, message: JSONRPCMessage): Promise<EventId> { |
| 71 | + const eventId = `${streamId}_${storedEvents.size}`; |
| 72 | + storedEvents.set(eventId, { streamId, message }); |
| 73 | + return eventId; |
| 74 | + }, |
| 75 | + async getStreamIdForEventId(eventId: EventId): Promise<StreamId | undefined> { |
| 76 | + return storedEvents.get(eventId)?.streamId; |
| 77 | + }, |
| 78 | + async replayEventsAfter(): Promise<StreamId> { |
| 79 | + throw new Error('not used in these tests'); |
| 80 | + } |
| 81 | + }; |
| 82 | + |
| 83 | + mcpServer = new McpServer({ name: 'test-server', version: '1.0.0' }, { capabilities: {} }); |
| 84 | + transport = new WebStandardStreamableHTTPServerTransport({ |
| 85 | + sessionIdGenerator: () => randomUUID(), |
| 86 | + eventStore |
| 87 | + }); |
| 88 | + await mcpServer.connect(transport); |
| 89 | + |
| 90 | + // Capture the per-message extras (closeSSEStream availability) while |
| 91 | + // preserving normal server dispatch. |
| 92 | + const serverOnMessage = transport.onmessage; |
| 93 | + transport.onmessage = (message, extra) => { |
| 94 | + capturedExtras.push(extra); |
| 95 | + serverOnMessage?.(message, extra); |
| 96 | + }; |
| 97 | + }); |
| 98 | + |
| 99 | + afterEach(async () => { |
| 100 | + await transport.close(); |
| 101 | + }); |
| 102 | + |
| 103 | + function expectPrimingEventStored(expected: boolean): void { |
| 104 | + // The priming event is stored as an empty message; real messages always |
| 105 | + // have at least a `jsonrpc` member. |
| 106 | + const primingStored = [...storedEvents.values()].some(event => Object.keys(event.message).length === 0); |
| 107 | + expect(primingStored).toBe(expected); |
| 108 | + } |
| 109 | + |
| 110 | + describe('unknown future protocol versions in the initialize body', () => { |
| 111 | + // Far-future sentinels, deliberately not the next planned revision |
| 112 | + // (2026-07-28): these cases must stay "unknown" when real future |
| 113 | + // versions gain support, rather than silently inverting. |
| 114 | + it.each(['2099-01-01', '2099-12-31'])('does not send a priming event for protocol version %s', async futureVersion => { |
| 115 | + const response = await transport.handleRequest(initializeRequest(futureVersion)); |
| 116 | + expect(response.status).toBe(200); |
| 117 | + |
| 118 | + const firstChunk = await readFirstSSEChunk(response); |
| 119 | + // The first SSE event must be the initialize response, not a priming event. |
| 120 | + expect(isPrimingEvent(firstChunk)).toBe(false); |
| 121 | + expect(firstChunk).toContain('"result"'); |
| 122 | + |
| 123 | + expectPrimingEventStored(false); |
| 124 | + }); |
| 125 | + |
| 126 | + it.each(['2099-01-01', '2099-12-31'])('does not provide closeSSEStream callbacks for protocol version %s', async futureVersion => { |
| 127 | + const response = await transport.handleRequest(initializeRequest(futureVersion)); |
| 128 | + expect(response.status).toBe(200); |
| 129 | + |
| 130 | + expect(capturedExtras).toHaveLength(1); |
| 131 | + expect(capturedExtras[0]?.closeSSEStream).toBeUndefined(); |
| 132 | + expect(capturedExtras[0]?.closeStandaloneSSEStream).toBeUndefined(); |
| 133 | + }); |
| 134 | + }); |
| 135 | + |
| 136 | + describe('existing protocol versions keep their behavior', () => { |
| 137 | + // Only 2025-11-25 (the version that introduced the empty-SSE-data fix) |
| 138 | + // takes the resumability paths - exactly as before the gates were bounded. |
| 139 | + const expectations: Array<[string, boolean]> = [ |
| 140 | + ['2024-10-07', false], |
| 141 | + ['2024-11-05', false], |
| 142 | + ['2025-03-26', false], |
| 143 | + ['2025-06-18', false], |
| 144 | + ['2025-11-25', true] |
| 145 | + ]; |
| 146 | + |
| 147 | + it.each(expectations)('priming event for protocol version %s: %s', async (version, expectPriming) => { |
| 148 | + const response = await transport.handleRequest(initializeRequest(version)); |
| 149 | + expect(response.status).toBe(200); |
| 150 | + |
| 151 | + const firstChunk = await readFirstSSEChunk(response); |
| 152 | + expect(isPrimingEvent(firstChunk)).toBe(expectPriming); |
| 153 | + |
| 154 | + expectPrimingEventStored(expectPriming); |
| 155 | + }); |
| 156 | + |
| 157 | + it.each(expectations)('closeSSEStream callbacks for protocol version %s: %s', async (version, expectAvailable) => { |
| 158 | + const response = await transport.handleRequest(initializeRequest(version)); |
| 159 | + expect(response.status).toBe(200); |
| 160 | + |
| 161 | + expect(capturedExtras).toHaveLength(1); |
| 162 | + expect(capturedExtras[0]?.closeSSEStream !== undefined).toBe(expectAvailable); |
| 163 | + expect(capturedExtras[0]?.closeStandaloneSSEStream !== undefined).toBe(expectAvailable); |
| 164 | + }); |
| 165 | + }); |
| 166 | +}); |
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