Limit the version registry to released protocol versions

KNOWN_PROTOCOL_VERSIONS now lists only released revisions
(2024-11-05 through 2025-11-25). Drop DRAFT_PROTOCOL_VERSION,
STATEFUL_PROTOCOL_VERSIONS, and is_stateful_protocol_version: nothing
uses them yet, and with no post-2025-11-25 revision in the registry the
stateful classification is vacuous. They can return alongside the code
that needs them.

Author: maxisbey

src/mcp/shared/version.py

@@ -1,4 +1,4 @@
-"""Protocol-version registry and comparison/classification helpers.
+"""Protocol-version registry and comparison helpers.
 
 Date-string protocol revisions happen to sort lexicographically, but versions
 are an enumerated set, not an ordered scalar: future identifiers are not
@@ -16,34 +16,12 @@
     "2025-03-26",
     "2025-06-18",
     "2025-11-25",
-    "2026-07-28",  # draft: recognized for ordering/classification, NOT negotiable
 )
-"""Every protocol revision this SDK knows about, oldest to newest."""
-
-DRAFT_PROTOCOL_VERSION: Final[str] = "2026-07-28"
-"""The in-progress spec revision.
-
-Recognized by the helpers in this module but absent from
-SUPPORTED_PROTOCOL_VERSIONS until the SDK actually implements it.
-"""
+"""Every released protocol revision, oldest to newest."""
 
 SUPPORTED_PROTOCOL_VERSIONS: list[str] = ["2024-11-05", "2025-03-26", "2025-06-18", LATEST_PROTOCOL_VERSION]
 """Protocol revisions this SDK can negotiate."""
 
-STATEFUL_PROTOCOL_VERSIONS: Final[frozenset[str]] = frozenset({"2024-11-05", "2025-03-26", "2025-06-18", "2025-11-25"})
-"""Revisions that negotiate via the initialize handshake.
-
-Closed by design: every revision after 2025-11-25 is stateless and negotiates
-per-request, never via initialize. Hardcoded - do not derive from
-SUPPORTED_PROTOCOL_VERSIONS. (Matches typescript-sdk's
-STATEFUL_PROTOCOL_VERSIONS / isStatefulProtocolVersion.)
-"""
-
-
-def is_stateful_protocol_version(version: str) -> bool:
-    """Return True if `version` negotiates via the initialize handshake."""
-    return version in STATEFUL_PROTOCOL_VERSIONS
-
 
 def is_version_at_least(version: str, minimum: str) -> bool:
     """Return True if `version` is a known revision at least as new as `minimum`.

tests/client/test_auth.py

@@ -825,7 +825,6 @@ async def test_resource_param_included_with_protected_resource_metadata(self, oa
         ("2025-03-26", False),
         ("2025-06-18", True),
         ("2025-11-25", True),
-        ("2026-07-28", True),
         # Unrecognized strings gate conservatively, even ones sorting after 2025-06-18.
         ("zzz", False),
         ("9999-99-99", False),

tests/shared/test_version.py

@@ -3,14 +3,10 @@
 import pytest
 
 from mcp.shared.version import (
-    DRAFT_PROTOCOL_VERSION,
     KNOWN_PROTOCOL_VERSIONS,
-    STATEFUL_PROTOCOL_VERSIONS,
     SUPPORTED_PROTOCOL_VERSIONS,
-    is_stateful_protocol_version,
     is_version_at_least,
 )
-from mcp.types import LATEST_PROTOCOL_VERSION
 
 
 @pytest.mark.parametrize(
@@ -21,10 +17,10 @@
         ("2024-11-05", "2024-11-05", True),
         # above
         ("2025-11-25", "2025-06-18", True),
-        ("2026-07-28", "2024-11-05", True),
+        ("2025-06-18", "2024-11-05", True),
         # below
         ("2025-06-18", "2025-11-25", False),
-        ("2024-11-05", "2026-07-28", False),
+        ("2024-11-05", "2025-03-26", False),
     ],
 )
 def test_is_version_at_least_ordering(version: str, minimum: str, expected: bool) -> None:
@@ -52,28 +48,9 @@ def test_is_version_at_least_matches_lexicographic_for_known_versions(version: s
     assert is_version_at_least(version, minimum) is (version >= minimum)
 
 
-def test_draft_version_is_known_but_not_negotiable_and_not_stateful() -> None:
-    assert DRAFT_PROTOCOL_VERSION in KNOWN_PROTOCOL_VERSIONS
-    assert DRAFT_PROTOCOL_VERSION not in SUPPORTED_PROTOCOL_VERSIONS
-    assert not is_stateful_protocol_version(DRAFT_PROTOCOL_VERSION)
-
-
-def test_draft_version_is_at_least_every_released_version() -> None:
-    for released in SUPPORTED_PROTOCOL_VERSIONS:
-        assert is_version_at_least(DRAFT_PROTOCOL_VERSION, released)
-
-
-def test_every_supported_version_is_stateful() -> None:
-    for version in SUPPORTED_PROTOCOL_VERSIONS:
-        assert is_stateful_protocol_version(version)
-
-
-def test_supported_versions_are_a_strict_subset_of_known() -> None:
-    assert set(SUPPORTED_PROTOCOL_VERSIONS) < set(KNOWN_PROTOCOL_VERSIONS)
-
-
-def test_latest_version_is_stateful() -> None:
-    assert LATEST_PROTOCOL_VERSION in STATEFUL_PROTOCOL_VERSIONS
+def test_supported_versions_are_known() -> None:
+    """Every negotiable revision must be in the ordering registry."""
+    assert set(SUPPORTED_PROTOCOL_VERSIONS) <= set(KNOWN_PROTOCOL_VERSIONS)
 
 
 def test_known_versions_are_strictly_ordered() -> None: