---id: 0001-stateless-streamable-httptype: decisionowner: justinreviewed: 2026-10-13status: accepted---# 0001 Stateless Streamable HTTP## ContextMCP over HTTP can be stateful: the server hands out an `Mcp-Session-Id` on `initialize`, the client sends it on every later request, and a `GET` opens a long-lived SSE stream for server-to-client messages. On Workers that means pinning a session to one place, which needs a Durable Object per session (the `agents` package's `McpAgent` does this).Our tools need none of it. They do not send notifications, sample the client's model, ask for elicitation, or report progress. Every call is one request and one answer.## DecisionServe MCP statelessly with the SDK's `WebStandardStreamableHTTPServerTransport`: no session id generator, JSON responses instead of SSE, and a new `McpServer` and transport for each `POST`. `GET` and `DELETE` on `/mcp` return 405.## Consequences- Any isolate can answer any request. No Durable Object, no session storage, no session to expire or lose.- The only runtime dependency is `@modelcontextprotocol/sdk` (and `zod`); no `agents` package and no `nodejs_compat` flag.- `initialize` is a formality: nothing it negotiates is remembered. Clients are fine with that, since the spec allows servers without sessions.- If a tool ever needs server-to-client messages (progress on a slow call, for example), this decision has to be revisited, most likely by moving to `McpAgent` and a Durable Object per session.