# `Raxol.MCP.Transport.SSE`
[🔗](https://github.com/DROOdotFOO/raxol/blob/v2.8.0/lib/raxol/mcp/transport/sse.ex#L2)

HTTP/SSE transport for MCP.

Plug-based router providing JSON-RPC over HTTP POST and server-sent events
for notifications. No Phoenix dependency.

## Endpoints

- `POST /mcp` -- receive JSON-RPC request, return response
- `GET /mcp/sse` -- server-sent events stream for notifications
- `GET /health` -- health check

## Connection identity

Unlike stdio, this transport serves many clients at once, and each POST is
a separate short-lived process with nothing tying it to a stream. That
matters for elicitation: an approval prompt belongs to the client that
triggered it, and only that client may answer it.

`GET /mcp/sse` therefore mints a session id and emits it as the stream's
first event:

    event: endpoint
    data: {"sessionId":"..."}

A client echoes it on every POST via the `mcp-session-id` header. Requests
that carry it are attributed to that connection; requests without it are
unidentified, which is safe but limited -- an unidentified caller can make
ordinary requests and simply cannot elicit (an ASK resolves to the
machine-readable deny). It can never answer someone else's prompt, because
every unidentified request is a DISTINCT anonymous connection that owns
nothing.

## Usage

Mount in a Plug pipeline or start standalone with `Plug.Cowboy`:

    Plug.Cowboy.http(Raxol.MCP.Transport.SSE, [server: Raxol.MCP.Server], port: 4001)

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*Consult [api-reference.md](api-reference.md) for complete listing*