Cloudflare's Agents SDK and product MCP servers adopt 2026-07-28, and /sse URLs stop serving HTTP+SSE

Cloudflare's adoption of the 2026-07-28 revision landed in two steps. Agents SDK v0.20.0 shipped July 27 with client and server support, its changelog describing the target as the MCP 2026-07-28 release candidate, one day before the final revision published. Then on July 28 a second changelog entry stated that Cloudflare's product MCP servers support the new specification, with each request running on a fresh stateless server without an MCP protocol session or protocol-specific Durable Object.

On the client side, the SDK probes each connection for 2026-07-28 support with server/discover and, if the server does not speak the stateless protocol, continues with the legacy initialize handshake on the same connection, so existing addMcpServer calls need no protocol-version setting. Stateless elicitation flows through input_required via multi round-trip requests. On the server side, createMcpHandler accepts a factory that creates an isolated server per request from @modelcontextprotocol/server, and a new agents/mcp/server entry point keeps legacy modules out of stateless bundles.

Three existing APIs were deprecated in v0.20.0: McpAgent is feature-frozen with no removal date announced, createMcpHandler(v1Server, options) is scheduled for removal in the next major version, and the MCPClientManager.callTool() overloads accepting resultSchema become compatibility overloads.

For the transport story, the July 28 entry draws a precise line: historical /sse URLs continue to work as aliases for the same Streamable HTTP handler, but they no longer serve the deprecated HTTP+SSE transport. Clients that force SSE transport need to switch to Streamable HTTP or automatic detection, and /mcp is the recommended path for new connections. The entry does not enumerate which individual product servers received the change.