-
Notifications
You must be signed in to change notification settings - Fork 3.9k
Expand file tree
/
Copy pathtest_streamable_http.py
More file actions
970 lines (825 loc) · 43.2 KB
/
Copy pathtest_streamable_http.py
File metadata and controls
970 lines (825 loc) · 43.2 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
"""Unit tests for the streamable-HTTP client transport.
The full client<->server round trip is pinned by the interaction suite under
tests/interaction/transports/; these tests cover the transport's header encoding and the
per-message metadata-headers merge directly because the headers are an HTTP-seam observation
the public client never exposes.
"""
import base64
import json
from collections.abc import AsyncIterator, Callable, Mapping
from typing import Any
import anyio
import httpx2
import pytest
from inline_snapshot import snapshot
from mcp_types import (
CLIENT_CAPABILITIES_META_KEY,
CLIENT_INFO_META_KEY,
CONNECTION_CLOSED,
INVALID_REQUEST,
METHOD_NOT_FOUND,
PROTOCOL_VERSION_META_KEY,
JSONRPCError,
JSONRPCNotification,
JSONRPCRequest,
JSONRPCResponse,
ListToolsResult,
PaginatedRequestParams,
)
from mcp_types.version import LATEST_MODERN_VERSION
from starlette.applications import Starlette
from starlette.routing import Mount
from starlette.types import Receive, Scope, Send
from mcp import Client, MCPError
from mcp.client.streamable_http import (
MAX_RECONNECTION_ATTEMPTS,
RequestContext,
StreamableHTTPTransport,
streamable_http_client,
)
from mcp.server import Server, ServerRequestContext
from mcp.server._streamable_http_modern import handle_modern_request
from mcp.server.streamable_http_manager import StreamableHTTPSessionManager
from mcp.server.subscriptions import InMemorySubscriptionBus, ListenHandler, ServerEvent
from mcp.shared._context_streams import ContextSendStream, create_context_streams
from mcp.shared.dispatcher import CallOptions, DispatchContext
from mcp.shared.inbound import MCP_METHOD_HEADER, MCP_PROTOCOL_VERSION_HEADER, encode_header_value
from mcp.shared.jsonrpc_dispatcher import JSONRPCDispatcher
from mcp.shared.message import ClientMessageMetadata, ServerMessageMetadata, SessionMessage
from mcp.shared.transport_context import TransportContext
from tests.interaction.transports import StreamingASGITransport
from tests.shared.test_dispatcher import Recorder, echo_handlers
@pytest.mark.parametrize(
("raw", "expected", "wrapped"),
[
("add", snapshot("add"), False),
("", snapshot(""), False),
("tool with spaces", snapshot("tool with spaces"), False),
(" add", snapshot("=?base64?IGFkZA==?="), True),
("add ", snapshot("=?base64?YWRkIA==?="), True),
("résumé", snapshot("=?base64?csOpc3Vtw6k=?="), True),
("a\r\nb", snapshot("=?base64?YQ0KYg==?="), True),
("=?base64?Zm9v?=", snapshot("=?base64?PT9iYXNlNjQ/Wm05dj89?="), True),
],
)
def test_mcp_name_header_values_are_base64_wrapped_when_unsafe_for_an_http_field(
raw: str, expected: str, wrapped: bool
) -> None:
"""Printable-ASCII names pass verbatim; CR/LF, non-ASCII, edge-whitespace, and sentinel-shaped names are wrapped.
The ``=?base64?...?=`` sentinel is the spec's RFC 7230 safety gate for the ``Mcp-Name`` header.
Wrapped values round-trip through base64 so the server can recover the original name. A leading
or trailing space is wrapped because RFC 7230 forbids it in field-values (h11 rejects on real
transports); an empty value is allowed and passes verbatim.
"""
encoded = encode_header_value(raw)
assert encoded == expected
if wrapped:
assert encoded.startswith("=?base64?") and encoded.endswith("?=")
assert base64.b64decode(encoded.removeprefix("=?base64?").removesuffix("?=")).decode() == raw
else:
assert encoded == raw
@pytest.mark.anyio
async def test_post_request_merges_per_message_metadata_headers() -> None:
"""`ClientMessageMetadata.headers` on a `SessionMessage` are merged into the outgoing POST headers
(SDK-defined: the headers sidecar is the path the session uses to reach the transport)."""
recorded: list[httpx2.Request] = []
def handler(request: httpx2.Request) -> httpx2.Response:
recorded.append(request)
body = json.loads(request.content)
return httpx2.Response(200, json={"jsonrpc": "2.0", "id": body["id"], "result": {}})
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id=1, method="tools/list", params={}),
metadata=ClientMessageMetadata(headers={"x-test": "v"}),
)
)
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert [r.method for r in recorded] == ["POST"]
assert recorded[0].headers["x-test"] == "v"
@pytest.mark.anyio
async def test_pre_session_bare_404_maps_to_method_not_found() -> None:
"""A bare HTTP 404 (no JSON-RPC body) before any session-id is held maps to METHOD_NOT_FOUND.
Gateways and legacy servers 404 at the HTTP layer for unknown methods; with no session yet,
"Session terminated" is meaningless, and the discover→initialize fallback ladder keys on -32601.
"""
def handler(request: httpx2.Request) -> httpx2.Response:
return httpx2.Response(404)
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(SessionMessage(JSONRPCRequest(jsonrpc="2.0", id=1, method="server/discover", params={})))
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCError)
assert reply.message.error.code == METHOD_NOT_FOUND
@pytest.mark.anyio
async def test_initialize_post_clears_cached_pv_header_and_unstamped_posts_read_it() -> None:
"""``initialize`` discards the cached protocol-version header; every other POST reads it.
Steps:
1. A stamped probe POST caches its ``MCP-Protocol-Version`` header.
2. An ``initialize`` POST clears that cache before building headers, so the fallback
handshake never carries a probe-stamped value.
3. A subsequent stamped POST re-seeds the cache with the negotiated version.
4. An unstamped POST (a JSON-RPC response written by the dispatcher, which never
passes through the session's stamp) then reads the cache and carries the
negotiated version — the spec MUST for all post-initialization HTTP requests.
"""
recorded: list[httpx2.Request] = []
def handler(request: httpx2.Request) -> httpx2.Response:
recorded.append(request)
body = json.loads(request.content)
if "id" not in body or "result" in body:
return httpx2.Response(202)
return httpx2.Response(200, json={"jsonrpc": "2.0", "id": body["id"], "result": {}})
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id=1, method="server/discover", params={}),
metadata=ClientMessageMetadata(headers={MCP_PROTOCOL_VERSION_HEADER: "2026-07-28"}),
)
)
await read.receive()
await write.send(SessionMessage(JSONRPCRequest(jsonrpc="2.0", id=2, method="initialize", params={})))
await read.receive()
await write.send(
SessionMessage(
message=JSONRPCNotification(jsonrpc="2.0", method="notifications/initialized"),
metadata=ClientMessageMetadata(headers={MCP_PROTOCOL_VERSION_HEADER: "2025-11-25"}),
)
)
# An unstamped JSON-RPC response — what the dispatcher writes when answering
# a server-initiated request (sampling/elicitation/roots).
await write.send(SessionMessage(JSONRPCResponse(jsonrpc="2.0", id=99, result={})))
assert [r.method for r in recorded] == ["POST", "POST", "POST", "POST"]
assert recorded[0].headers[MCP_PROTOCOL_VERSION_HEADER] == "2026-07-28"
assert MCP_PROTOCOL_VERSION_HEADER not in recorded[1].headers
assert recorded[2].headers[MCP_PROTOCOL_VERSION_HEADER] == "2025-11-25"
assert recorded[3].headers[MCP_PROTOCOL_VERSION_HEADER] == "2025-11-25"
class _ParkedSSEStream(httpx2.AsyncByteStream):
"""An SSE response body that emits one comment line, then parks until closed.
`opened` fires once the transport is iterating the body (the POST is truly in
flight); `closed` fires when httpx2 tears the body down — the observable proof
that an abort, not a response, ended the stream.
"""
def __init__(self) -> None:
self.opened = anyio.Event()
self.closed = anyio.Event()
self._release = anyio.Event()
async def __aiter__(self) -> AsyncIterator[bytes]:
self.opened.set()
yield b": parked\n\n"
await self._release.wait()
async def aclose(self) -> None:
self.closed.set()
self._release.set()
def _sse_or_ack_handler(
parked: _ParkedSSEStream, posted: list[dict[str, Any]], frame_posted: anyio.Event
) -> Callable[[httpx2.Request], httpx2.Response]:
"""Requests get the parked SSE body; notifications get 202 and set `frame_posted`."""
def handler(request: httpx2.Request) -> httpx2.Response:
body = json.loads(request.content)
posted.append(body)
if "id" in body:
return httpx2.Response(200, headers={"content-type": "text/event-stream"}, stream=parked)
frame_posted.set()
return httpx2.Response(202)
return handler
@pytest.mark.anyio
async def test_modern_cancelled_frame_aborts_the_matching_in_flight_post() -> None:
"""At 2026 an outbound `notifications/cancelled` never POSTs — closing the named
request's response stream IS the wire's cancellation signal — so the transport
aborts the in-flight POST and swallows the frame."""
parked = _ParkedSSEStream()
posted: list[dict[str, Any]] = []
def handler(request: httpx2.Request) -> httpx2.Response:
posted.append(json.loads(request.content))
return httpx2.Response(200, headers={"content-type": "text/event-stream"}, stream=parked)
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (_read, write),
):
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id="listen-1", method="subscriptions/listen", params={}),
metadata=ClientMessageMetadata(headers={MCP_PROTOCOL_VERSION_HEADER: LATEST_MODERN_VERSION}),
)
)
await parked.opened.wait()
await write.send(
SessionMessage(
JSONRPCNotification(
jsonrpc="2.0", method="notifications/cancelled", params={"requestId": "listen-1"}
)
)
)
await parked.closed.wait()
assert [body["method"] for body in posted] == ["subscriptions/listen"]
@pytest.mark.anyio
@pytest.mark.parametrize("stamped_version", [None, "2025-11-25"], ids=["no-version-yet", "2025-11-25"])
async def test_legacy_cancelled_frame_posts_and_leaves_the_stream_open(stamped_version: str | None) -> None:
"""Below 2026 — or before any stamped POST has revealed the version — the frame is
the spec's cancellation signal: it POSTs, and the request's stream stays open
(a 2025 disconnect is explicitly not a cancel)."""
parked = _ParkedSSEStream()
posted: list[dict[str, Any]] = []
frame_posted = anyio.Event()
handler = _sse_or_ack_handler(parked, posted, frame_posted)
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (_read, write),
):
metadata = (
ClientMessageMetadata(headers={MCP_PROTOCOL_VERSION_HEADER: stamped_version})
if stamped_version is not None
else None
)
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id=1, method="tools/call", params={}),
metadata=metadata,
)
)
await parked.opened.wait()
await write.send(
SessionMessage(
JSONRPCNotification(jsonrpc="2.0", method="notifications/cancelled", params={"requestId": 1})
)
)
await frame_posted.wait()
# Checked before teardown: exiting the transport cancels the parked POST.
assert not parked.closed.is_set()
assert [body["method"] for body in posted] == ["tools/call", "notifications/cancelled"]
@pytest.mark.anyio
@pytest.mark.parametrize(
"params",
[
pytest.param({"requestId": 999}, id="unknown-id"),
pytest.param({"requestId": True}, id="bool-must-not-alias-request-id-1"),
pytest.param({"requestId": "1"}, id="string-1-must-not-match-int-1"),
pytest.param({}, id="no-request-id"),
pytest.param(None, id="no-params"),
],
)
async def test_modern_cancelled_frames_matching_no_post_are_swallowed(params: dict[str, Any] | None) -> None:
"""At 2026 the frame is swallowed even when it aborts nothing — the wire defines no
client-to-server notifications, so a late cancel racing the response must not leak
a POST — and a mismatched id must not abort someone else's stream."""
parked = _ParkedSSEStream()
posted: list[dict[str, Any]] = []
def handler(request: httpx2.Request) -> httpx2.Response:
body = json.loads(request.content)
posted.append(body)
if body.get("id") == 1:
return httpx2.Response(200, headers={"content-type": "text/event-stream"}, stream=parked)
return httpx2.Response(200, json={"jsonrpc": "2.0", "id": body["id"], "result": {}})
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id=1, method="subscriptions/listen", params={}),
metadata=ClientMessageMetadata(headers={MCP_PROTOCOL_VERSION_HEADER: LATEST_MODERN_VERSION}),
)
)
await parked.opened.wait()
await write.send(
SessionMessage(JSONRPCNotification(jsonrpc="2.0", method="notifications/cancelled", params=params))
)
# A follow-up request completing proves the loop moved past the swallowed frame.
await write.send(SessionMessage(JSONRPCRequest(jsonrpc="2.0", id=2, method="ping", params={})))
reply = await read.receive()
# Checked before teardown: exiting the transport cancels the parked POST.
assert not parked.closed.is_set()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCResponse)
assert reply.message.id == 2
assert [body["method"] for body in posted] == ["subscriptions/listen", "ping"]
@pytest.mark.anyio
async def test_handler_scoped_cancelled_frames_are_translated_at_modern_too() -> None:
"""A cancel carrying `ServerMessageMetadata` (a handler abandoning its own
back-channel request) still names one of OUR outbound ids — every spec-legal
cancel names a request its sender issued — so at 2026 it aborts that POST and
stays off the wire like any other."""
parked = _ParkedSSEStream()
posted: list[dict[str, Any]] = []
frame_posted = anyio.Event()
handler = _sse_or_ack_handler(parked, posted, frame_posted)
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (_read, write),
):
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id=1, method="tools/call", params={}),
metadata=ClientMessageMetadata(headers={MCP_PROTOCOL_VERSION_HEADER: LATEST_MODERN_VERSION}),
)
)
await parked.opened.wait()
await write.send(
SessionMessage(
message=JSONRPCNotification(
jsonrpc="2.0", method="notifications/cancelled", params={"requestId": 1}
),
metadata=ServerMessageMetadata(related_request_id=99),
)
)
await parked.closed.wait()
assert [body["method"] for body in posted] == ["tools/call"]
assert not frame_posted.is_set()
@pytest.mark.anyio
async def test_cancel_for_a_request_sent_under_2025_still_posts_after_modern_adoption() -> None:
"""The translation follows the era the NAMED request was sent under, not the
cache at cancel time: a request POSTed under 2025 keeps 2025 cancellation
semantics (frame on the wire, stream left open) even after a later message
flips the negotiated version to 2026."""
parked = _ParkedSSEStream()
posted: list[dict[str, Any]] = []
frame_posted = anyio.Event()
def handler(request: httpx2.Request) -> httpx2.Response:
body = json.loads(request.content)
posted.append(body)
if body.get("id") == 1:
return httpx2.Response(200, headers={"content-type": "text/event-stream"}, stream=parked)
if "id" in body:
return httpx2.Response(200, json={"jsonrpc": "2.0", "id": body["id"], "result": {}})
frame_posted.set()
return httpx2.Response(202)
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id=1, method="tools/call", params={}),
metadata=ClientMessageMetadata(headers={MCP_PROTOCOL_VERSION_HEADER: "2025-11-25"}),
)
)
await parked.opened.wait()
# A modern-stamped request flips the cached negotiated version.
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id=2, method="ping", params={}),
metadata=ClientMessageMetadata(headers={MCP_PROTOCOL_VERSION_HEADER: LATEST_MODERN_VERSION}),
)
)
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCResponse)
await write.send(
SessionMessage(
JSONRPCNotification(jsonrpc="2.0", method="notifications/cancelled", params={"requestId": 1})
)
)
await frame_posted.wait()
# Checked before teardown: exiting the transport cancels the parked POST.
assert not parked.closed.is_set()
assert [body["method"] for body in posted] == ["tools/call", "ping", "notifications/cancelled"]
class _SignalingBus(InMemorySubscriptionBus):
"""Signals subscribe/unsubscribe so a test observes the stream lifecycle through
the bus Protocol (the public seam) instead of polling handler internals."""
def __init__(self) -> None:
super().__init__()
self.subscribed = anyio.Event()
self.unsubscribed = anyio.Event()
def subscribe(self, listener: Callable[[ServerEvent], None]) -> Callable[[], None]:
unsubscribe = super().subscribe(listener)
self.subscribed.set()
def unsubscribe_and_signal() -> None:
unsubscribe()
self.unsubscribed.set()
return unsubscribe_and_signal
@pytest.mark.anyio
async def test_scope_cancel_aborts_a_modern_listen_post_end_to_end() -> None:
"""Over a real ASGI bridge: cancelling the caller of a parked `subscriptions/listen`
closes the POST's response stream — the server treats the disconnect as the cancel
and releases the subscription — and no `notifications/cancelled` crosses the wire."""
bus = _SignalingBus()
server = Server("test", on_subscriptions_listen=ListenHandler(bus))
async def app(scope: Scope, receive: Receive, send: Send) -> None:
async with server.lifespan(server) as lifespan_state:
await handle_modern_request(server, None, False, lifespan_state, scope, receive, send)
posted_methods: list[str] = []
async def record_request(request: httpx2.Request) -> None:
posted_methods.append(json.loads(request.content)["method"])
acked = anyio.Event()
async def on_notify(dctx: DispatchContext[TransportContext], method: str, params: Mapping[str, Any] | None) -> None:
assert method == "notifications/subscriptions/acknowledged"
acked.set()
on_request, _ = echo_handlers(Recorder())
with anyio.fail_after(15):
async with (
httpx2.AsyncClient(
transport=StreamingASGITransport(app),
base_url="http://testserver",
event_hooks={"request": [record_request]},
) as http,
streamable_http_client("http://testserver/mcp", http_client=http) as (read, write),
):
dispatcher: JSONRPCDispatcher[TransportContext] = JSONRPCDispatcher(read, write)
async with anyio.create_task_group() as tg: # pragma: no branch
await tg.start(dispatcher.run, on_request, on_notify)
listen_scope = anyio.CancelScope()
async def send_listen() -> None:
params: dict[str, Any] = {
"_meta": {
PROTOCOL_VERSION_META_KEY: LATEST_MODERN_VERSION,
CLIENT_INFO_META_KEY: {"name": "test-client", "version": "0"},
CLIENT_CAPABILITIES_META_KEY: {},
},
"notifications": {"toolsListChanged": True},
}
opts: CallOptions = {
"request_id": "listen-1",
"headers": {
MCP_PROTOCOL_VERSION_HEADER: LATEST_MODERN_VERSION,
MCP_METHOD_HEADER: "subscriptions/listen",
},
}
with listen_scope:
await dispatcher.send_raw_request("subscriptions/listen", params, opts)
tg.start_soon(send_listen)
await acked.wait()
assert bus.subscribed.is_set()
assert not bus.unsubscribed.is_set()
listen_scope.cancel()
await bus.unsubscribed.wait()
tg.cancel_scope.cancel()
assert posted_methods == ["subscriptions/listen"]
class _CompletingSSEStream(httpx2.AsyncByteStream):
"""An SSE body that delivers one JSON-RPC response, then parks in `aclose`.
Holding `aclose` keeps the finished POST task alive past its response, so a
test can re-register the same request id underneath it before releasing.
"""
def __init__(self, response_body: dict[str, Any]) -> None:
self._event = f"data: {json.dumps(response_body)}\n\n".encode()
self.release = anyio.Event()
async def __aiter__(self) -> AsyncIterator[bytes]:
yield self._event
async def aclose(self) -> None:
await self.release.wait()
@pytest.mark.anyio
async def test_a_finished_post_task_does_not_evict_a_reused_ids_new_registration() -> None:
"""Request ids are reusable once resolved; a finished POST task unwinding late
must not pop the successor's registration, or a cancel for the reused id would
find nothing to abort and the live POST would leak past the cancellation."""
completing = _CompletingSSEStream({"jsonrpc": "2.0", "id": "dup-1", "result": {}})
parked = _ParkedSSEStream()
posted: list[dict[str, Any]] = []
streams = [completing, parked]
def handler(request: httpx2.Request) -> httpx2.Response:
posted.append(json.loads(request.content))
return httpx2.Response(200, headers={"content-type": "text/event-stream"}, stream=streams.pop(0))
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
modern = ClientMessageMetadata(headers={MCP_PROTOCOL_VERSION_HEADER: LATEST_MODERN_VERSION})
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id="dup-1", method="tools/call", params={}),
metadata=modern,
)
)
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCResponse)
# The first task is now parked in `aclose`; reuse its id underneath it.
await write.send(
SessionMessage(
message=JSONRPCRequest(jsonrpc="2.0", id="dup-1", method="subscriptions/listen", params={}),
metadata=modern,
)
)
await parked.opened.wait()
completing.release.set()
await anyio.wait_all_tasks_blocked()
# The successor's registration survived: a cancel still aborts it.
await write.send(
SessionMessage(
JSONRPCNotification(jsonrpc="2.0", method="notifications/cancelled", params={"requestId": "dup-1"})
)
)
await parked.closed.wait()
assert [body["method"] for body in posted] == ["tools/call", "subscriptions/listen"]
class _DyingSSEStream(httpx2.AsyncByteStream):
"""Emits one id-less comment then breaks - a non-resumable stream dropping."""
def __init__(self) -> None:
self.opened = anyio.Event()
async def __aiter__(self) -> AsyncIterator[bytes]:
self.opened.set()
yield b": hello\n\n"
raise httpx2.ReadError("connection reset")
async def aclose(self) -> None:
pass
@pytest.mark.anyio
async def test_a_non_resumable_sse_drop_resolves_the_request_with_an_error() -> None:
"""A per-request SSE stream that dies having carried no event ids can never deliver its
response; the transport resolves the waiter with CONNECTION_CLOSED instead of hanging forever."""
dying = _DyingSSEStream()
def handler(request: httpx2.Request) -> httpx2.Response:
return httpx2.Response(200, headers={"content-type": "text/event-stream"}, stream=dying)
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(
SessionMessage(JSONRPCRequest(jsonrpc="2.0", id="listen-1", method="subscriptions/listen", params={}))
)
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCError)
assert reply.message.id == "listen-1"
assert reply.message.error.code == CONNECTION_CLOSED
class _DeliverOnCommandSSEStream(httpx2.AsyncByteStream):
"""Parks after opening, then delivers one JSON-RPC response when told."""
def __init__(self, response_body: dict[str, Any]) -> None:
self._event = f"data: {json.dumps(response_body)}\n\n".encode()
self.opened = anyio.Event()
self.deliver = anyio.Event()
async def __aiter__(self) -> AsyncIterator[bytes]:
self.opened.set()
await self.deliver.wait()
yield self._event
async def aclose(self) -> None:
pass
@pytest.mark.anyio
async def test_a_superseded_posts_late_real_response_cannot_answer_the_successor() -> None:
"""SDK-defined: re-issuing an id severs the superseded POST, so nothing from its
stream (a late real response, or a synthesized error for its death) can resolve
the reused id's waiter; only the successor's own response arrives."""
stale = _DeliverOnCommandSSEStream({"jsonrpc": "2.0", "id": "dup-1", "result": {"origin": "stale"}})
succeeding = _DeliverOnCommandSSEStream({"jsonrpc": "2.0", "id": "dup-1", "result": {"origin": "fresh"}})
streams: list[httpx2.AsyncByteStream] = [stale, succeeding]
def handler(request: httpx2.Request) -> httpx2.Response:
return httpx2.Response(200, headers={"content-type": "text/event-stream"}, stream=streams.pop(0))
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(SessionMessage(JSONRPCRequest(jsonrpc="2.0", id="dup-1", method="tools/call", params={})))
await stale.opened.wait()
await write.send(SessionMessage(JSONRPCRequest(jsonrpc="2.0", id="dup-1", method="tools/call", params={})))
await succeeding.opened.wait()
stale.deliver.set()
await anyio.wait_all_tasks_blocked()
succeeding.deliver.set()
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCResponse), reply.message
assert reply.message.result == {"origin": "fresh"}
@pytest.mark.anyio
async def test_a_202_to_a_request_resolves_the_waiter_with_an_error() -> None:
"""SDK-defined: a server that answers a request with 202 Accepted has declared no
response will follow (the spec requires SSE or JSON for requests); the transport
resolves the waiter with INVALID_REQUEST instead of parking the caller forever."""
def handler(request: httpx2.Request) -> httpx2.Response:
return httpx2.Response(202)
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(
SessionMessage(JSONRPCRequest(jsonrpc="2.0", id="listen-1", method="subscriptions/listen", params={}))
)
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCError)
assert reply.message.id == "listen-1"
assert reply.message.error.code == INVALID_REQUEST
def _abandoned_request_context(
http: httpx2.AsyncClient, send: ContextSendStream[SessionMessage | Exception]
) -> RequestContext:
return RequestContext(
client=http,
session_id=None,
session_message=SessionMessage(
JSONRPCRequest(jsonrpc="2.0", id="listen-1", method="subscriptions/listen", params={})
),
metadata=None,
read_stream_writer=send,
)
@pytest.mark.anyio
async def test_exhausted_reconnection_attempts_resolve_the_request_with_an_error() -> None:
"""An id-bearing stream that exhausts its reconnection budget also resolves the waiter with CONNECTION_CLOSED."""
transport = StreamableHTTPTransport("http://test/mcp")
send, receive = create_context_streams[SessionMessage | Exception](1)
async with httpx2.AsyncClient() as http:
with anyio.fail_after(5):
await transport._handle_reconnection( # pyright: ignore[reportPrivateUsage]
_abandoned_request_context(http, send), "evt-7", None, MAX_RECONNECTION_ATTEMPTS
)
reply = await receive.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCError)
assert reply.message.id == "listen-1"
assert reply.message.error.code == CONNECTION_CLOSED
send.close()
receive.close()
@pytest.mark.anyio
async def test_resolving_an_abandoned_request_after_the_reader_closed_is_contained() -> None:
"""Teardown race: a stream dying after the reader closed resolves best-effort and must not crash."""
transport = StreamableHTTPTransport("http://test/mcp")
send, receive = create_context_streams[SessionMessage | Exception](1)
receive.close()
async with httpx2.AsyncClient() as http:
with anyio.fail_after(5):
await transport._handle_reconnection( # pyright: ignore[reportPrivateUsage]
_abandoned_request_context(http, send), "evt-7", None, MAX_RECONNECTION_ATTEMPTS
)
send.close()
@pytest.mark.anyio
async def test_trailing_slash_redirect_within_origin_is_followed_by_the_transport() -> None:
"""SDK-defined: a redirect that stays on the endpoint's origin (here Starlette's Mount sending
/mcp to /mcp/) is followed by the transport itself, so a caller-supplied client left at
httpx2's no-follow default still connects."""
session_manager = StreamableHTTPSessionManager(app=Server("redirect-test"))
app = Starlette(routes=[Mount("/mcp", app=session_manager.handle_request)])
urls: list[str] = []
async def record(request: httpx2.Request) -> None:
urls.append(str(request.url))
with anyio.fail_after(5):
async with (
session_manager.run(),
httpx2.AsyncClient(transport=StreamingASGITransport(app), event_hooks={"request": [record]}) as http,
Client(streamable_http_client("http://mcp.example/mcp", http_client=http)) as client,
):
assert client.server_info is not None
assert client.server_info.name == "redirect-test"
assert urls[:2] == ["http://mcp.example/mcp", "http://mcp.example/mcp/"]
class _RedirectPromptsListElsewhere(httpx2.AsyncBaseTransport):
"""Serves `app` in process, except that a prompts/list POST is answered with a redirect to
another origin."""
def __init__(self, app: Starlette) -> None:
self.inner = StreamingASGITransport(app)
async def handle_async_request(self, request: httpx2.Request) -> httpx2.Response:
await request.aread()
if request.method == "POST" and json.loads(request.content).get("method") == "prompts/list":
return httpx2.Response(307, headers={"location": "http://other.example/mcp/"})
return await self.inner.handle_async_request(request)
async def __aenter__(self) -> "_RedirectPromptsListElsewhere":
await self.inner.__aenter__()
return self
async def __aexit__(self, *args: Any) -> None:
await self.inner.__aexit__(*args)
@pytest.mark.anyio
async def test_redirect_to_another_origin_fails_that_call_and_keeps_the_session() -> None:
"""SDK-defined: a redirect pointing outside the endpoint's origin is not followed, whatever the
caller's client is configured to do: the call it answered fails with MCPError naming the
location, nothing is sent to the other origin, and the session stays usable."""
async def list_tools(ctx: ServerRequestContext, params: PaginatedRequestParams | None) -> ListToolsResult:
return ListToolsResult(tools=[])
session_manager = StreamableHTTPSessionManager(app=Server("redirect-test", on_list_tools=list_tools))
app = Starlette(routes=[Mount("/mcp", app=session_manager.handle_request)])
urls: list[str] = []
async def record(request: httpx2.Request) -> None:
urls.append(str(request.url))
with anyio.fail_after(5):
async with (
session_manager.run(),
httpx2.AsyncClient(
transport=_RedirectPromptsListElsewhere(app), event_hooks={"request": [record]}, follow_redirects=True
) as http,
Client(streamable_http_client("http://mcp.example/mcp/", http_client=http)) as client,
):
with pytest.raises(MCPError) as exc_info:
await client.list_prompts()
assert (await client.list_tools()).tools == []
assert exc_info.value.error.code == INVALID_REQUEST
assert exc_info.value.error.message == snapshot(
"Redirect to http://other.example/mcp/ not followed; use that URL as the endpoint if it is the intended server"
)
assert [url for url in urls if "other.example" in url] == []
@pytest.mark.anyio
async def test_redirected_notification_is_dropped_and_the_next_message_still_goes_out() -> None:
"""SDK-defined: a notification whose POST is redirected outside the origin has no waiter to
resolve, so it is logged and dropped; the transport keeps serving the write stream."""
urls: list[str] = []
def handler(request: httpx2.Request) -> httpx2.Response:
urls.append(str(request.url))
return httpx2.Response(307, headers={"location": "http://other.example/mcp"})
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(
SessionMessage(JSONRPCNotification(jsonrpc="2.0", method="notifications/roots/list_changed"))
)
await write.send(SessionMessage(JSONRPCRequest(jsonrpc="2.0", id=7, method="tools/list", params={})))
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCError)
assert reply.message.id == 7
assert reply.message.error.code == INVALID_REQUEST
assert urls == ["http://test/mcp", "http://test/mcp"]
@pytest.mark.anyio
async def test_get_stream_gives_up_without_retrying_when_the_endpoint_redirects_elsewhere() -> None:
"""SDK-defined: the standalone GET stream is not opened through a redirect to another origin,
and since the same GET would be redirected again the transport logs it and stops instead of
spending its reconnection attempts."""
gets: list[str] = []
def handler(request: httpx2.Request) -> httpx2.Response:
gets.append(str(request.url))
return httpx2.Response(307, headers={"location": "http://other.example/mcp"})
transport = StreamableHTTPTransport("http://test/mcp")
transport.session_id = "session-1"
send, receive = create_context_streams[SessionMessage | Exception](1)
with anyio.fail_after(5):
async with httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http:
await transport.handle_get_stream(http, send)
assert gets == ["http://test/mcp"]
send.close()
receive.close()
@pytest.mark.anyio
async def test_resumption_redirected_elsewhere_resolves_that_request_with_an_error() -> None:
"""SDK-defined: a resumption GET answered with a redirect to another origin is not followed;
the resumed request is resolved with an error naming the location rather than left waiting."""
seen: list[tuple[str, str | None]] = []
def handler(request: httpx2.Request) -> httpx2.Response:
seen.append((f"{request.method} {request.url}", request.headers.get("last-event-id")))
return httpx2.Response(307, headers={"location": "http://other.example/mcp"})
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client("http://test/mcp", http_client=http) as (read, write),
):
await write.send(
SessionMessage(
JSONRPCRequest(jsonrpc="2.0", id="resume-1", method="tools/call", params={}),
metadata=ClientMessageMetadata(resumption_token="evt-41"),
)
)
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCError)
assert reply.message.id == "resume-1"
assert reply.message.error.code == INVALID_REQUEST
assert reply.message.error.message == snapshot(
"Redirect to http://other.example/mcp not followed; use that URL as the endpoint if it is the intended server"
)
assert seen == [("GET http://test/mcp", "evt-41")]
async def _redirected_call_error(url: str, location: str) -> str:
"""Send one request through streamable_http_client to a server answering `url` with a 307 to
`location`, and return the message of the error that resolves it."""
def handler(request: httpx2.Request) -> httpx2.Response:
return httpx2.Response(307, headers={"location": location})
with anyio.fail_after(5):
async with (
httpx2.AsyncClient(transport=httpx2.MockTransport(handler)) as http,
streamable_http_client(url, http_client=http) as (read, write),
):
await write.send(SessionMessage(JSONRPCRequest(jsonrpc="2.0", id=1, method="tools/list", params={})))
reply = await read.receive()
assert isinstance(reply, SessionMessage)
assert isinstance(reply.message, JSONRPCError)
return reply.message.error.message
@pytest.mark.anyio
async def test_https_endpoint_redirected_to_plain_http_is_explained_and_the_https_form_suggested() -> None:
"""SDK-authored text: a redirect of an HTTPS endpoint to plain HTTP on the same host (the usual
sign of a TLS-terminating proxy the server does not trust) never suggests the http:// URL."""
message = await _redirected_call_error("https://mcp.example/mcp", "http://mcp.example/mcp/")
assert message == snapshot("""\
Redirect to http://mcp.example/mcp/ not followed: it would downgrade this HTTPS endpoint to plain HTTP.
The server is likely behind a TLS-terminating proxy whose forwarded headers it does not trust,
often combined with a trailing-slash difference. Try https://mcp.example/mcp/ instead, or fix the proxy settings.\
""")
@pytest.mark.anyio
async def test_unfollowed_redirect_location_is_named_without_its_query_string() -> None:
"""SDK-authored text: the location is reported without query or userinfo, which may carry state
that does not belong in an error message or a log line."""
message = await _redirected_call_error("http://mcp.example/mcp", "https://sso.example/login?state=s3cr3t&nonce=n")
assert message == snapshot(
"Redirect to https://sso.example/login not followed; use that URL as the endpoint if it is the intended server"
)
@pytest.mark.anyio
async def test_https_endpoint_redirected_to_plain_http_elsewhere_never_suggests_the_http_url() -> None:
"""SDK-authored text: the downgrade explanation applies whatever host the http:// location names,
so the message never offers a plain-HTTP URL as the endpoint to configure."""
message = await _redirected_call_error("https://mcp.example/mcp", "http://backend.lan:8000/mcp/")
assert message == snapshot("""\
Redirect to http://backend.lan:8000/mcp/ not followed: it would downgrade this HTTPS endpoint to plain HTTP.
The server is likely behind a TLS-terminating proxy whose forwarded headers it does not trust,
often combined with a trailing-slash difference. Try https://backend.lan:8000/mcp/ instead, or fix the proxy settings.\
""")