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Harden the dual-era stream loop's era-lock and rejection semantics (#3040)

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Max 2026-07-01 17:07:12 +01:00 • committed by GitHub
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229
tests/server/test_runner.py
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@ -30,6 +30,7 @@ from mcp_types import (
ErrorData,
Implementation,
InitializeRequestParams,
JSONRPCRequest,
ListToolsResult,
NotificationParams,
PaginatedRequestParams,
@ -1331,8 +1332,9 @@ async def test_dual_era_loop_initialize_after_modern_lock_without_a_parseable_ve
@pytest.mark.anyio
async def test_dual_era_loop_initialize_locks_legacy_and_rejects_modern_traffic(server: SrvT):
"""After a successful handshake the connection is legacy for its lifetime:
`server/discover` and envelope-bearing requests are rejected with
INVALID_REQUEST while plain legacy requests keep working."""
envelope-bearing requests (including a triple-stamped `server/discover`)
are rejected with INVALID_REQUEST while plain legacy requests keep
working."""
async with dual_era_client(server) as (client, _):
init = await client.send_raw_request("initialize", _initialize_params())
assert init["protocolVersion"] == LATEST_HANDSHAKE_VERSION
@ -1347,6 +1349,21 @@ async def test_dual_era_loop_initialize_locks_legacy_and_rejects_modern_traffic(
assert "locked to the legacy handshake era" in discover_exc.value.error.message
@pytest.mark.anyio
async def test_dual_era_loop_bare_discover_after_legacy_lock_is_byte_identical(server: SrvT):
"""A bare `server/discover` on a legacy-locked connection falls through to
the loop runner's per-version surface validation - the same
METHOD_NOT_FOUND shape a handshake-only server produced, byte for byte
(released probing clients key on it)."""
async with dual_era_client(server) as (client, _):
await client.send_raw_request("initialize", _initialize_params())
with pytest.raises(MCPError) as exc_info:
await client.send_raw_request("server/discover", None)
assert exc_info.value.error.code == METHOD_NOT_FOUND
assert exc_info.value.error.message == "Method not found"
assert exc_info.value.error.data == "server/discover"
@pytest.mark.anyio
async def test_dual_era_loop_unsupported_modern_version_rejects_without_locking(server: SrvT):
"""A probe at an unknown modern version gets -32022 with the supported
@ -1402,15 +1419,60 @@ async def test_dual_era_loop_modern_request_without_envelope_rejects(server: Srv
@pytest.mark.anyio
async def test_dual_era_loop_rejects_subscriptions_listen_on_modern(server: SrvT):
"""`subscriptions/listen` is rejected before dispatch on the stream-pair
modern path: the registered handler assumes the HTTP entry's stream
semantics."""
modern path (the registered handler assumes the HTTP entry's stream
semantics) - and like every failed request it does not lock the era, so
the legacy handshake stays available."""
async with dual_era_client(server) as (client, _):
with pytest.raises(MCPError) as exc_info:
await client.send_raw_request("subscriptions/listen", _modern_params())
init = await client.send_raw_request("initialize", _initialize_params())
assert init["protocolVersion"] == LATEST_HANDSHAKE_VERSION
assert exc_info.value.error.code == METHOD_NOT_FOUND
assert "not served over this transport" in exc_info.value.error.message
@pytest.mark.anyio
async def test_dual_era_loop_malformed_envelope_content_never_locks(server: SrvT):
"""The envelope triple with mis-shaped values fails the request but never
locks the era: the lock commits only when a modern request SUCCEEDS, so a
buggy client's initialize fallback still works (it must never see -32022
for a request that failed)."""
params: dict[str, Any] = {"_meta": {**_modern_envelope(), CLIENT_INFO_META_KEY: 42}}
async with dual_era_client(server) as (client, _):
with pytest.raises(MCPError) as exc_info:
await client.send_raw_request("tools/list", params)
init = await client.send_raw_request("initialize", _initialize_params())
assert init["protocolVersion"] == LATEST_HANDSHAKE_VERSION
assert exc_info.value.error.code == INVALID_PARAMS
assert exc_info.value.error.code != UNSUPPORTED_PROTOCOL_VERSION
@pytest.mark.anyio
async def test_dual_era_loop_failed_modern_request_never_locks(server: SrvT):
"""A well-formed modern request for an unknown method fails without
locking; the next modern request locks on its own success."""
async with dual_era_client(server) as (client, _):
with pytest.raises(MCPError) as exc_info:
await client.send_raw_request("nope/missing", _modern_params())
init = await client.send_raw_request("initialize", _initialize_params())
assert init["protocolVersion"] == LATEST_HANDSHAKE_VERSION
assert exc_info.value.error.code == METHOD_NOT_FOUND
@pytest.mark.anyio
async def test_dual_era_loop_initialize_with_envelope_takes_the_handshake_path(server: SrvT):
"""`initialize` is legacy-distinctive by definition - it does not exist at
modern versions - so stamping the envelope triple on it still runs the
handshake and locks legacy."""
init_params = {**_initialize_params(), **_modern_params()}
async with dual_era_client(server) as (client, _):
init = await client.send_raw_request("initialize", init_params)
assert init["protocolVersion"] == LATEST_HANDSHAKE_VERSION
with pytest.raises(MCPError) as exc_info:
await client.send_raw_request("tools/list", _modern_params())
assert exc_info.value.error.code == INVALID_REQUEST
@pytest.mark.anyio
async def test_dual_era_loop_modern_notification_dispatches_at_locked_version(server: SrvT):
"""Notifications carry no envelope, so on a modern-locked connection they
@ -1480,6 +1542,156 @@ async def test_dual_era_loop_modern_refuses_server_initiated_requests(server: Sr
assert "no back-channel" in exc_info.value.error.message
@pytest.mark.anyio
async def test_dual_era_loop_late_modern_success_does_not_overwrite_a_committed_legacy_lock():
"""The era settles exactly once, on the FIRST client-visible success: a
modern request that was already in flight when a legacy handshake
committed may still complete - its response stands - but the connection
stays legacy, so the handshaked client is never stranded."""
entered = anyio.Event()
release = anyio.Event()
async def list_tools(ctx: Ctx, params: PaginatedRequestParams | None) -> ListToolsResult:
entered.set()
await release.wait()
return ListToolsResult(tools=[Tool(name="t", input_schema={"type": "object"})])
parked = Server(name="parked-server", version="0.0.1", on_list_tools=list_tools)
async with dual_era_client(parked) as (client, _):
modern_result: dict[str, Any] = {}
async def modern_call() -> None:
modern_result.update(await client.send_raw_request("tools/list", _modern_params()))
async with anyio.create_task_group() as tg:
tg.start_soon(modern_call)
# The modern dispatch is parked in its handler before the
# handshake frame is even written, so the initialize commits first.
await entered.wait()
init = await client.send_raw_request("initialize", _initialize_params())
assert init["protocolVersion"] == LATEST_HANDSHAKE_VERSION
release.set()
assert modern_result["tools"][0]["name"] == "t"
# The straggler's success did not move the era: plain legacy requests
# still serve (a modern overwrite would demand the envelope triple).
result = await client.send_raw_request("tools/list", None)
assert result["tools"][0]["name"] == "t"
@pytest.mark.anyio
async def test_dual_era_loop_modern_success_cancelled_away_at_the_response_write_never_locks():
"""A peer cancel that lands while the handler is finishing means the
dispatcher replaces the computed result with "Request cancelled" - the
client never sees the success, so the era must not lock and the legacy
handshake must stay available."""
entered = anyio.Event()
release = anyio.Event()
async def list_tools(ctx: Ctx, params: PaginatedRequestParams | None) -> ListToolsResult:
entered.set()
# Survive the interrupt-mode scope cancel so the handler completes
# with the cancel pending - the cancellation is then delivered at the
# dispatcher's response-write checkpoint, after the era commit ran.
with anyio.CancelScope(shield=True):
await release.wait()
return ListToolsResult(tools=[])
parked = Server(name="parked-server", version="0.0.1", on_list_tools=list_tools)
async with dual_era_client(parked) as (client, _):
failures: list[MCPError] = []
async def modern_call() -> None:
with pytest.raises(MCPError) as exc_info:
await client.send_raw_request("tools/list", _modern_params())
failures.append(exc_info.value)
async with anyio.create_task_group() as tg:
tg.start_soon(modern_call)
await entered.wait()
# First request on a fresh dispatcher pair, so its id is 1.
await client.notify("notifications/cancelled", {"requestId": 1})
# The read loop handles frames in order: this marker's response
# proves the cancel was processed before the handler resumes.
with pytest.raises(MCPError):
await client.send_raw_request("probe/marker", None)
release.set()
assert failures[0].error.message == "Request cancelled"
# The cancelled-away success never locked the era.
init = await client.send_raw_request("initialize", _initialize_params())
assert init["protocolVersion"] == LATEST_HANDSHAKE_VERSION
@pytest.mark.anyio
async def test_dual_era_loop_maps_unmapped_handler_exceptions_like_the_modern_http_entry():
"""An unmapped handler exception on a modern request surfaces as the
generic INTERNAL_ERROR - the same boundary as the modern HTTP entry - so
handler internals never reach the wire. (The dispatcher's code-0
catch-all is a handshake-era compat pin and stays legacy-only.) The
failed request never locks, so the handshake stays available."""
async def list_tools(ctx: Ctx, params: PaginatedRequestParams | None) -> ListToolsResult:
raise RuntimeError("handler internals")
exploding = Server(name="exploding-server", version="0.0.1", on_list_tools=list_tools)
async with dual_era_client(exploding) as (client, _):
with pytest.raises(MCPError) as exc_info:
await client.send_raw_request("tools/list", _modern_params())
init = await client.send_raw_request("initialize", _initialize_params())
assert init["protocolVersion"] == LATEST_HANDSHAKE_VERSION
assert exc_info.value.error.code == INTERNAL_ERROR
assert exc_info.value.error.message == "Internal server error"
assert "handler internals" not in str(exc_info.value.error)
@pytest.mark.anyio
async def test_dual_era_loop_raise_exceptions_reraises_unmapped_modern_handler_exceptions():
"""Debug mode keeps its contract on the modern path: an unmapped handler
exception still propagates out of the loop instead of being swallowed
into the generic INTERNAL_ERROR mapping."""
async def list_tools(ctx: Ctx, params: PaginatedRequestParams | None) -> ListToolsResult:
raise RuntimeError("boom")
exploding = Server(name="exploding-server", version="0.0.1", on_list_tools=list_tools)
c2s_send, c2s_recv = anyio.create_memory_object_stream[SessionMessage | Exception](8)
s2c_send, s2c_recv = anyio.create_memory_object_stream[SessionMessage | Exception](8)
frame = JSONRPCRequest(jsonrpc="2.0", id=1, method="tools/list", params=_modern_params())
with pytest.RaisesGroup(RuntimeError, flatten_subgroups=True, allow_unwrapped=True):
async with anyio.create_task_group() as tg, c2s_send, c2s_recv, s2c_send, s2c_recv:
tg.start_soon(
partial(
serve_dual_era_loop, exploding, c2s_recv, s2c_send, lifespan_state=_LIFESPAN, raise_exceptions=True
)
)
with anyio.fail_after(5): # pragma: no branch - group exit misreports the with arcs
await c2s_send.send(SessionMessage(message=frame))
# The dispatcher answers on the wire before re-raising; waiting
# for the answer keeps the streams open until the handler ran.
await s2c_recv.receive()
@pytest.mark.anyio
async def test_dual_era_loop_custom_method_with_mis_shaped_envelope_values_still_routes():
"""A mis-shaped clientInfo envelope value degrades to not-supplied - the
`Connection.from_envelope` coercion the modern HTTP entry uses - so a
custom method (no kernel params surface to re-reject it) serves
identically on both transports, with `client_params is None`."""
seen: list[object] = []
async def greet(ctx: Ctx, params: RequestParams | None) -> dict[str, Any]:
seen.append(ctx.session.client_params)
return {"ok": True}
greeter = Server(name="greeter-server", version="0.0.1")
greeter.add_request_handler("custom/greet", RequestParams, greet)
params = _modern_params()
params["_meta"][CLIENT_INFO_META_KEY] = "not-an-object"
async with dual_era_client(greeter) as (client, _):
result = await client.send_raw_request("custom/greet", params)
assert result == {"ok": True}
assert seen == [None]
def test_has_modern_envelope_requires_the_full_key_triple():
assert not _has_modern_envelope(None)
assert not _has_modern_envelope({})
@ -1526,7 +1738,8 @@ async def test_no_server_requests_dispatch_context_denies_requests_and_delegates
inner = _RecordingInnerDctx()
wrapper = _NoServerRequestsDispatchContext(inner)
assert wrapper.can_send_request is False
assert wrapper.transport is inner.transport
# The transport metadata is masked to agree with the wrapper's denial.
assert wrapper.transport == TransportContext(kind="jsonrpc", can_send_request=False)
assert wrapper.request_id == 7
assert wrapper.message_metadata is None
assert wrapper.cancel_requested is inner.cancel_requested
@ -1538,6 +1751,12 @@ async def test_no_server_requests_dispatch_context_denies_requests_and_delegates
assert inner.progresses == [0.5]
def test_no_server_requests_dispatch_context_passes_an_already_denying_transport_through():
inner = _RecordingInnerDctx()
inner.transport = TransportContext(kind="jsonrpc", can_send_request=False)
assert _NoServerRequestsDispatchContext(inner).transport is inner.transport
@pytest.mark.anyio
async def test_notify_only_outbound_forwards_notifications_and_refuses_requests():
inner = _RecordingInnerDctx()