模型上下文协议（MCP）发布了2026-07-28版本规范，实现了协议设计的根本性转变。[1]新版本将MCP从有状态的双向协议改造为无状态的请求/响应模式，使得每个请求都可以路由到不同的服务器实例上，从而支持轮询负载均衡。[1]此次更新涉及TypeScript、Python、Go、C#等Tier 1 SDK，这些SDK的月下载量接近5亿次，其中TypeScript和Python SDK的总下载量均已超过10亿次。[1]
核心架构调整包括删除initialize/initialized交换和Mcp-Session-Id header，[1]转而引入server/discover RPC使客户端能够发现服务器能力。[1]方法和工具名称现在通过Mcp-Method和Mcp-Name HTTP头传输，[1]多轮请求（MRTR）机制取代了之前需要保持开放流的服务器初始化请求。[1]列表响应增加了ttlMs和cacheScope字段以支持客户端缓存策略，[1]授权服务器须按RFC 9207返回iss参数，客户端在兑换代码前必须完成验证。[1]
此外，Dynamic Client Registration（DCR）正式弃用，改为Client ID Metadata Documents（CIMD）方案。[1]Roots、Sampling和Logging等功能至少保留12个月兼容期后将移除，[1]HTTP+SSE传输模式也已正式弃用。[1]
The Model Context Protocol (MCP) has released its 2026-07-28 specification, introducing a fundamental architectural shift from a stateful bidirectional protocol to a stateless request-response model [1]. This transformation enables each request to be routed to different server instances, supporting round-robin load balancing while maintaining protocol consistency [1].
The update eliminates the initialize/initialized exchange and removes the Mcp-Session-Id header, streamlining the connection handshake [1]. In their place, the specification introduces a new server/discover RPC endpoint that allows clients to dynamically discover server capabilities [1]. Method and tool names are now transmitted via HTTP headers—Mcp-Method and Mcp-Name—rather than embedded in request payloads [1]. Multi-Round-Trip Requests (MRTR) replace the previous server initialization pattern that required maintaining open streams [1].
Several features enhance caching and security in the new architecture. List responses now include ttlMs and cacheScope parameters to support client-side caching strategies [1]. Authorization servers must return the iss parameter in compliance with RFC 9207, and clients are required to validate this parameter before exchanging authorization codes [1]. The specification formally deprecates Dynamic Client Registration (DCR) in favor of Client ID Metadata Documents (CIMD) [1].
MCP Tier 1 SDKs—covering TypeScript, Python, Go, and C#—have been updated to implement the new specification [1]. The Tier 1 SDKs collectively generate nearly 500 million monthly downloads, with TypeScript and Python SDKs each exceeding 1 billion total downloads [1]. Deprecated features including Roots, Sampling, Logging, and HTTP+SSE transport will maintain backward compatibility for a minimum of 12 months [1].