.. index:: single: mcp_server_streamable_http_transport
.. _mcp_server_streamable_http_transport/0:

.. rst-class:: right

**object**

``mcp_server_streamable_http_transport``
========================================

Implements the Streamable HTTP transport for MCP servers. Uses Logtalk ``http_server::serve_until_shutdown/5`` and a dedicated ``http_handler_protocol`` handler object. Supports specs 2025-06-18, 2025-11-25, and 2026-07-28 selected via the ``spec/1`` option and delegated to the matching ``mcp_server_*_spec`` object. Supports optional OAuth protection and protected-resource metadata publication using the ``oauth/4`` option. Long-lived subscriptions/listen streams emit periodic SSE comment keep-alives (``http_sse_keepalive/1``). Requires a multi-threaded backend for subscriptions/listen.

| **Availability:** 
|    ``logtalk_load(mcp_server(loader))``

| **Author:** Paulo Moura
| **Version:** 1:0:0
| **Date:** 2026-09-02

| **Compilation flags:**
|    ``static, context_switching_calls, threaded``


| **Implements:**
|    ``public`` :ref:`mcp_server_transport_protocol <mcp_server_transport_protocol/0>`
| **Imports:**
|    ``public`` :ref:`mcp_server_application <mcp_server_application/0>`
| **Uses:**
|    :ref:`format <format/0>`
|    :ref:`http_oauth <http_oauth/0>`
|    :ref:`http_oauth_metadata <http_oauth_metadata/0>`
|    :ref:`http_server <http_server/0>`
|    :ref:`json <json/0>`
|    :ref:`json_rpc <json_rpc/0>`
|    :ref:`list <list/0>`
|    :ref:`mcp_server_2025_06_18_spec <mcp_server_2025_06_18_spec/0>`
|    :ref:`mcp_server_2025_11_25_spec <mcp_server_2025_11_25_spec/0>`
|    :ref:`mcp_server_2026_07_28_spec <mcp_server_2026_07_28_spec/0>`
|    :ref:`os <os/0>`
|    :ref:`term_io <term_io/0>`
|    :ref:`type <type/0>`

| **Remarks:**
|    (none)

| **Inherited public predicates:**
|     :ref:`options_protocol/0::check_option/1`  :ref:`options_protocol/0::check_options/1`  :ref:`mcp_server_transport_protocol/0::cleanup/0`  :ref:`options_protocol/0::default_option/1`  :ref:`options_protocol/0::default_options/1`  :ref:`mcp_server_transport_protocol/0::notify/1`  :ref:`options_protocol/0::option/2`  :ref:`options_protocol/0::option/3`  :ref:`mcp_server_transport_protocol/0::spec/1`  :ref:`mcp_server_transport_protocol/0::start/4`  :ref:`mcp_server_application/0::tool_descriptors_to_json/3`  :ref:`options_protocol/0::valid_option/1`  :ref:`options_protocol/0::valid_options/1`  

.. contents::
   :local:
   :backlinks: top

Public predicates
-----------------

.. index:: prepare/2
.. _mcp_server_streamable_http_transport/0::prepare/2:

``prepare/2``
^^^^^^^^^^^^^

Initializes adapter state for ``Application`` with ``Options`` without opening a listener. Used by unit tests and by embeddings by pairing with ``handle_mcp_request/4`` and ``cleanup/0``.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``prepare(Application,Options)``
| **Mode and number of proofs:**
|    ``prepare(+object_identifier,+list)`` - ``one_or_error``

| **Exceptions:**
|    ``Options`` is a variable:
|        ``instantiation_error``
|    ``Options`` is neither a variable nor a list:
|        ``type_error(list,Options)``
|    An element ``Option`` of the list ``Options`` is a variable:
|        ``instantiation_error``
|    An element ``Option`` of the list ``Options`` is neither a variable nor a compound term:
|        ``type_error(compound,Option)``
|    An element ``Option`` of the list ``Options`` is a compound term but not a valid option:
|        ``domain_error(option,Option)``


------------

.. index:: attach_sse_stream/1
.. _mcp_server_streamable_http_transport/0::attach_sse_stream/1:

``attach_sse_stream/1``
^^^^^^^^^^^^^^^^^^^^^^^

Registers a live output stream for incremental SSE writes. Headers must already have been written. Each ``emit_progress/5`` call writes and flushes immediately.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``attach_sse_stream(Stream)``
| **Mode and number of proofs:**
|    ``attach_sse_stream(+stream)`` - ``one``


------------

.. index:: detach_sse_stream/0
.. _mcp_server_streamable_http_transport/0::detach_sse_stream/0:

``detach_sse_stream/0``
^^^^^^^^^^^^^^^^^^^^^^^

Clears any live SSE output stream registration.

| **Compilation flags:**
|    ``static``

| **Mode and number of proofs:**
|    ``detach_sse_stream`` - ``one``


------------

.. index:: sse_headers/1
.. _mcp_server_streamable_http_transport/0::sse_headers/1:

``sse_headers/1``
^^^^^^^^^^^^^^^^^

HTTP headers for an SSE response body.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``sse_headers(Headers)``
| **Mode and number of proofs:**
|    ``sse_headers(-list)`` - ``one``


------------

.. index:: current_options/1
.. _mcp_server_streamable_http_transport/0::current_options/1:

``current_options/1``
^^^^^^^^^^^^^^^^^^^^^

Unified with the options list established by ``prepare/2`` or ``start/4``.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``current_options(Options)``
| **Mode and number of proofs:**
|    ``current_options(-list)`` - ``zero_or_one``


------------

.. index:: handle_mcp_request/4
.. _mcp_server_streamable_http_transport/0::handle_mcp_request/4:

``handle_mcp_request/4``
^^^^^^^^^^^^^^^^^^^^^^^^

Handles one MCP HTTP request. ``Method`` is an uppercase HTTP method atom. ``Headers`` is a list of ``Name-Value`` pairs. ``Body`` is the raw request body atom. ``HTTPResponse`` is ``http_response(Status, Headers, BodyAtom)`` or ``http_response(already_sent, Headers, BodyAtom)``.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``handle_mcp_request(Method,Headers,Body,HTTPResponse)``
| **Mode and number of proofs:**
|    ``handle_mcp_request(+atom,+list,+atom,-compound)`` - ``one``


------------

.. index:: emit_progress/5
.. _mcp_server_streamable_http_transport/0::emit_progress/5:

``emit_progress/5``
^^^^^^^^^^^^^^^^^^^

Emits a notifications/progress event. In live mode the SSE record is written and flushed immediately on the attached stream. In buffered mode the event is queued until ``finalize_response/4``.

| **Compilation flags:**
|    ``static``

| **Template:**
|    ``emit_progress(Token,RequestId,ProgressValue,Total,Message)``
| **Mode and number of proofs:**
|    ``emit_progress(+term,+term,+number,+number,+atom)`` - ``one``


------------

Protected predicates
--------------------

(no local declarations; see entity ancestors if any)

Private predicates
------------------

.. index:: running_/0
.. _mcp_server_streamable_http_transport/0::running_/0:

``running_/0``
^^^^^^^^^^^^^^

True while the adapter has been prepared or is serving requests.

| **Compilation flags:**
|    ``dynamic``

| **Mode and number of proofs:**
|    ``running_`` - ``zero_or_one``


------------

.. index:: server_options_/1
.. _mcp_server_streamable_http_transport/0::server_options_/1:

``server_options_/1``
^^^^^^^^^^^^^^^^^^^^^

Merged server options for the active prepare/start session.

| **Compilation flags:**
|    ``dynamic``

| **Template:**
|    ``server_options_(Options)``
| **Mode and number of proofs:**
|    ``server_options_(-list)`` - ``zero_or_one``


------------

.. index:: shutdown_control_/1
.. _mcp_server_streamable_http_transport/0::shutdown_control_/1:

``shutdown_control_/1``
^^^^^^^^^^^^^^^^^^^^^^^

Token passed to ``http_server::request_shutdown/1`` when stopping the listener.

| **Compilation flags:**
|    ``dynamic``

| **Template:**
|    ``shutdown_control_(Control)``
| **Mode and number of proofs:**
|    ``shutdown_control_(-nonvar)`` - ``zero_or_one``


------------

.. index:: subscription_/4
.. _mcp_server_streamable_http_transport/0::subscription_/4:

``subscription_/4``
^^^^^^^^^^^^^^^^^^^

Active subscriptions/listen registration. Synchronization uses ``threaded_wait/1`` and ``threaded_notify/1`` tagged by ``SubscriptionId``.

| **Compilation flags:**
|    ``dynamic``

| **Template:**
|    ``subscription_(SubscriptionId,RequestId,Filters,Stream)``
| **Mode and number of proofs:**
|    ``subscription_(-atom,-nonvar,-list,-nonvar)`` - ``zero_or_more``


------------

.. index:: progress_events_/1
.. _mcp_server_streamable_http_transport/0::progress_events_/1:

``progress_events_/1``
^^^^^^^^^^^^^^^^^^^^^^

Buffered notifications/progress events when SSE mode is not live.

| **Compilation flags:**
|    ``dynamic``

| **Template:**
|    ``progress_events_(Events)``
| **Mode and number of proofs:**
|    ``progress_events_(-list)`` - ``zero_or_one``


------------

.. index:: progress_token_/1
.. _mcp_server_streamable_http_transport/0::progress_token_/1:

``progress_token_/1``
^^^^^^^^^^^^^^^^^^^^^

progressToken from the current request, or none.

| **Compilation flags:**
|    ``dynamic``

| **Template:**
|    ``progress_token_(Token)``
| **Mode and number of proofs:**
|    ``progress_token_(-nonvar)`` - ``zero_or_one``


------------

.. index:: sse_output_/1
.. _mcp_server_streamable_http_transport/0::sse_output_/1:

``sse_output_/1``
^^^^^^^^^^^^^^^^^

Live response stream for incremental SSE writes.

| **Compilation flags:**
|    ``dynamic``

| **Template:**
|    ``sse_output_(Stream)``
| **Mode and number of proofs:**
|    ``sse_output_(-stream)`` - ``zero_or_one``


------------

.. index:: sse_mode_/1
.. _mcp_server_streamable_http_transport/0::sse_mode_/1:

``sse_mode_/1``
^^^^^^^^^^^^^^^

Current SSE delivery mode: live, buffered, or none.

| **Compilation flags:**
|    ``dynamic``

| **Template:**
|    ``sse_mode_(Mode)``
| **Mode and number of proofs:**
|    ``sse_mode_(-atom)`` - ``zero_or_one``


------------

Operators
---------

(none)

