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"""Tests for the unified Client class."""
from __future__ import annotations
import contextvars
from collections.abc import AsyncIterator, Iterator
from contextlib import asynccontextmanager, contextmanager
from unittest.mock import patch
import anyio
import mcp_types as types
import pytest
from inline_snapshot import snapshot
from mcp_types import (
CallToolResult,
EmptyResult,
GetPromptResult,
ListPromptsResult,
ListResourcesResult,
ListResourceTemplatesResult,
ListToolsResult,
Prompt,
PromptArgument,
PromptMessage,
PromptsCapability,
ReadResourceResult,
Resource,
ResourcesCapability,
ServerCapabilities,
TextContent,
TextResourceContents,
Tool,
ToolsCapability,
)
from mcp_types.version import LATEST_HANDSHAKE_VERSION
from pydantic import FileUrl
from mcp import MCPError
from mcp.client._memory import InMemoryTransport
from mcp.client._transport import TransportStreams
from mcp.client.client import Client
from mcp.client.session import ClientRequestContext
from mcp.client.streamable_http import streamable_http_client
from mcp.server import Server, ServerRequestContext
from mcp.server.mcpserver import Context, MCPServer
from mcp.shared.memory import MessageStream, create_client_server_memory_streams
from mcp.shared.message import SessionMessage
from tests.interaction._connect import BASE_URL, mounted_app
pytestmark = pytest.mark.anyio
@pytest.fixture
def simple_server() -> Server:
"""Create a simple MCP server for testing."""
async def handle_list_resources(
ctx: ServerRequestContext, params: types.PaginatedRequestParams | None
) -> ListResourcesResult:
return ListResourcesResult(
resources=[Resource(uri="memory://test", name="Test Resource", description="A test resource")]
)
async def handle_subscribe_resource(ctx: ServerRequestContext, params: types.SubscribeRequestParams) -> EmptyResult:
return EmptyResult()
async def handle_unsubscribe_resource(
ctx: ServerRequestContext, params: types.UnsubscribeRequestParams
) -> EmptyResult:
return EmptyResult()
async def handle_set_logging_level(ctx: ServerRequestContext, params: types.SetLevelRequestParams) -> EmptyResult:
return EmptyResult()
async def handle_completion(ctx: ServerRequestContext, params: types.CompleteRequestParams) -> types.CompleteResult:
return types.CompleteResult(completion=types.Completion(values=[]))
return Server( # pyright: ignore[reportDeprecated]
name="test_server",
on_list_resources=handle_list_resources,
on_subscribe_resource=handle_subscribe_resource,
on_unsubscribe_resource=handle_unsubscribe_resource,
on_set_logging_level=handle_set_logging_level,
on_completion=handle_completion,
)
@pytest.fixture
def app() -> MCPServer:
"""Create an MCPServer server for testing."""
server = MCPServer("test")
@server.tool()
def greet(name: str) -> str:
"""Greet someone by name."""
return f"Hello, {name}!"
@server.resource("test://resource")
def test_resource() -> str:
"""A test resource."""
return "Test content"
@server.prompt()
def greeting_prompt(name: str) -> str:
"""A greeting prompt."""
return f"Please greet {name} warmly."
return server
async def test_client_is_initialized(app: MCPServer):
"""Test that the client is initialized after entering context."""
async with Client(app, mode="legacy") as client:
assert client.server_capabilities == snapshot(
ServerCapabilities(
experimental={},
prompts=PromptsCapability(list_changed=False),
resources=ResourcesCapability(subscribe=False, list_changed=False),
tools=ToolsCapability(list_changed=False),
)
)
assert client.server_info.name == "test"
async def test_client_exposes_negotiated_protocol_version(app: MCPServer):
"""The negotiated protocol version is readable after initialization."""
async with Client(app, mode="legacy") as client:
assert client.protocol_version == LATEST_HANDSHAKE_VERSION
async def test_client_with_simple_server(simple_server: Server):
"""Test that from_server works with a basic Server instance."""
async with Client(simple_server) as client:
resources = await client.list_resources()
assert resources == snapshot(
ListResourcesResult(
resources=[Resource(name="Test Resource", uri="memory://test", description="A test resource")]
)
)
async def test_client_send_ping(app: MCPServer):
async with Client(app, mode="legacy") as client:
result = await client.send_ping() # pyright: ignore[reportDeprecated]
assert result == snapshot(EmptyResult())
async def test_client_list_tools(app: MCPServer):
async with Client(app) as client:
result = await client.list_tools()
assert result == snapshot(
ListToolsResult(
tools=[
Tool(
name="greet",
description="Greet someone by name.",
input_schema={
"properties": {"name": {"title": "Name", "type": "string"}},
"required": ["name"],
"title": "greetArguments",
"type": "object",
},
output_schema={
"properties": {"result": {"title": "Result", "type": "string"}},
"required": ["result"],
"title": "greetOutput",
"type": "object",
},
)
]
)
)
async def test_client_call_tool(app: MCPServer):
async with Client(app) as client:
result = await client.call_tool("greet", {"name": "World"})
assert result == snapshot(
CallToolResult(
content=[TextContent(text="Hello, World!")],
structured_content={"result": "Hello, World!"},
)
)
async def test_read_resource(app: MCPServer):
"""Test reading a resource."""
async with Client(app) as client:
result = await client.read_resource("test://resource")
assert result == snapshot(
ReadResourceResult(
contents=[TextResourceContents(uri="test://resource", mime_type="text/plain", text="Test content")]
)
)
async def test_read_resource_error_propagates():
"""MCPError raised by a server handler propagates to the client with its code intact."""
async def handle_read_resource(
ctx: ServerRequestContext, params: types.ReadResourceRequestParams
) -> ReadResourceResult:
raise MCPError(code=404, message="no resource with that URI was found")
server = Server("test", on_read_resource=handle_read_resource)
async with Client(server) as client:
with pytest.raises(MCPError) as exc_info:
await client.read_resource("unknown://example")
assert exc_info.value.error.code == 404
async def test_raise_exceptions_propagates_handler_error_on_modern_inproc_path():
"""`raise_exceptions=True` on the modern in-process path: an unmapped handler
exception reaches the client with its original type chained, instead of being
sanitized to an opaque `INTERNAL_ERROR`."""
async def handle_call_tool(ctx: ServerRequestContext, params: types.CallToolRequestParams) -> CallToolResult:
raise ValueError("boom")
server = Server("test", on_call_tool=handle_call_tool)
async with Client(server, mode="2026-07-28", raise_exceptions=True) as client:
with pytest.raises(MCPError) as exc_info:
await client.call_tool("explode", {})
# The original exception is chained — not swallowed into a generic "Internal server error".
assert isinstance(exc_info.value.__cause__, ValueError)
assert str(exc_info.value.__cause__) == "boom"
async def test_raise_exceptions_false_sanitizes_handler_error_on_modern_inproc_path():
"""`raise_exceptions=False` (the default) on the modern in-process path: an
unmapped handler exception is sanitized to an opaque `INTERNAL_ERROR` so the
in-process path matches the wire path's leak guard."""
async def handle_call_tool(ctx: ServerRequestContext, params: types.CallToolRequestParams) -> CallToolResult:
raise ValueError("boom")
server = Server("test", on_call_tool=handle_call_tool)
async with Client(server, mode="2026-07-28", raise_exceptions=False) as client:
with pytest.raises(MCPError) as exc_info:
await client.call_tool("explode", {})
assert exc_info.value.error.code == types.INTERNAL_ERROR
assert exc_info.value.error.message == "Internal server error"
assert exc_info.value.__cause__ is None
async def test_get_prompt(app: MCPServer):
"""Test getting a prompt."""
async with Client(app) as client:
result = await client.get_prompt("greeting_prompt", {"name": "Alice"})
assert result == snapshot(
GetPromptResult(
description="A greeting prompt.",
messages=[PromptMessage(role="user", content=TextContent(text="Please greet Alice warmly."))],
)
)
def test_client_session_property_before_enter(app: MCPServer):
"""Test that accessing session before context manager raises RuntimeError."""
client = Client(app)
with pytest.raises(RuntimeError, match="Client must be used within an async context manager"):
client.session
async def test_client_reentry_raises_runtime_error(app: MCPServer):
"""Test that reentering a client raises RuntimeError."""
async with Client(app) as client:
with pytest.raises(RuntimeError, match="Client is already entered"):
await client.__aenter__()
async def test_client_send_progress_notification():
"""Test sending progress notification."""
received_from_client = None
event = anyio.Event()
async def handle_progress(ctx: ServerRequestContext, params: types.ProgressNotificationParams) -> None:
nonlocal received_from_client
received_from_client = {"progress_token": params.progress_token, "progress": params.progress}
event.set()
server = Server(name="test_server", on_progress=handle_progress) # pyright: ignore[reportDeprecated]
with anyio.fail_after(5):
async with Client(server, mode="legacy") as client:
await client.send_progress_notification(progress_token="token123", progress=50.0) # pyright: ignore[reportDeprecated]
await event.wait()
assert received_from_client == snapshot({"progress_token": "token123", "progress": 50.0})
async def test_client_subscribe_resource(simple_server: Server):
async with Client(simple_server, mode="legacy") as client:
result = await client.subscribe_resource("memory://test")
assert result == snapshot(EmptyResult())
async def test_client_unsubscribe_resource(simple_server: Server):
async with Client(simple_server, mode="legacy") as client:
result = await client.unsubscribe_resource("memory://test")
assert result == snapshot(EmptyResult())
async def test_client_set_logging_level(simple_server: Server):
"""Test setting logging level."""
async with Client(simple_server, mode="legacy") as client:
result = await client.set_logging_level("debug") # pyright: ignore[reportDeprecated]
assert result == snapshot(EmptyResult())
async def test_client_list_resources_with_params(app: MCPServer):
"""Test listing resources with params parameter."""
async with Client(app) as client:
result = await client.list_resources()
assert result == snapshot(
ListResourcesResult(
resources=[
Resource(
name="test_resource",
uri="test://resource",
description="A test resource.",
mime_type="text/plain",
)
]
)
)
async def test_client_list_resource_templates(app: MCPServer):
"""Test listing resource templates with params parameter."""
async with Client(app) as client:
result = await client.list_resource_templates()
assert result == snapshot(ListResourceTemplatesResult(resource_templates=[]))
async def test_list_prompts(app: MCPServer):
"""Test listing prompts with params parameter."""
async with Client(app) as client:
result = await client.list_prompts()
assert result == snapshot(
ListPromptsResult(
prompts=[
Prompt(
name="greeting_prompt",
description="A greeting prompt.",
arguments=[PromptArgument(name="name", required=True)],
)
]
)
)
async def test_complete_with_prompt_reference(simple_server: Server):
"""Test getting completions for a prompt argument."""
async with Client(simple_server) as client:
ref = types.PromptReference(type="ref/prompt", name="test_prompt")
result = await client.complete(ref=ref, argument={"name": "arg", "value": "test"})
assert result == snapshot(types.CompleteResult(completion=types.Completion(values=[])))
def test_client_with_url_initializes_streamable_http_transport():
with patch("mcp.client.client.streamable_http_client") as mock:
_ = Client("http://localhost:8000/mcp")
mock.assert_called_once_with("http://localhost:8000/mcp")
async def test_client_uses_transport_directly(app: MCPServer):
transport = InMemoryTransport(app)
async with Client(transport, mode="legacy") as client:
result = await client.call_tool("greet", {"name": "Transport"})
assert result == snapshot(
CallToolResult(
content=[TextContent(text="Hello, Transport!")],
structured_content={"result": "Hello, Transport!"},
)
)
_TEST_CONTEXTVAR = contextvars.ContextVar("test_var", default="initial")
@contextmanager
def _set_test_contextvar(value: str) -> Iterator[None]:
token = _TEST_CONTEXTVAR.set(value)
try:
yield
finally:
_TEST_CONTEXTVAR.reset(token)
async def test_context_propagation():
"""Sender's contextvars.Context is propagated to the server handler."""
server = MCPServer("test")
@server.tool()
async def check_context() -> str:
"""Return the contextvar value visible to the handler."""
return _TEST_CONTEXTVAR.get()
async with Client(server) as client:
with _set_test_contextvar("client_value"):
result = await client.call_tool("check_context", {})
assert result.content[0].text == "client_value", ( # type: ignore[union-attr]
"Server handler did not see the sender's contextvars.Context"
)
async def test_client_auto_mode_probes_discover_then_adopts(simple_server: Server) -> None:
"""`mode='auto'` over an in-process HTTP transport: the `server/discover` probe
reaches the modern entry and the negotiated protocol version is adopted without
an `initialize` handshake. Runs over HTTP because the in-memory runner gates
`server/discover` behind the init handshake."""
with anyio.fail_after(5):
async with (
mounted_app(simple_server) as (http, _),
Client(streamable_http_client(f"{BASE_URL}/mcp", http_client=http), mode="auto") as client,
):
assert client.protocol_version == "2026-07-28"
assert (await client.list_resources()).resources[0].name == "Test Resource"
@pytest.mark.parametrize("code", [types.METHOD_NOT_FOUND, types.REQUEST_TIMEOUT, types.INTERNAL_ERROR])
async def test_client_auto_mode_falls_back_to_initialize_on_legacy_signal(code: int) -> None:
"""`mode='auto'`: any JSON-RPC error from `server/discover` makes
`Client.__aenter__` run the legacy `initialize()` handshake and land at a
handshake-era protocol version. The denylist policy treats every server-sent
rpc-error as "not modern" — including INTERNAL_ERROR, since a legacy server
may crash on the unknown method before reaching its router. A real `Server`
always implements `server/discover`, so the server side is hand-played."""
methods_seen: list[str] = []
async def scripted_server(streams: MessageStream) -> None:
server_read, server_write = streams
async for message in server_read:
assert isinstance(message, SessionMessage)
frame = message.message
assert isinstance(frame, types.JSONRPCRequest | types.JSONRPCNotification)
methods_seen.append(frame.method)
if isinstance(frame, types.JSONRPCNotification):
continue
if frame.method == "server/discover":
error = types.ErrorData(code=code, message="nope")
await server_write.send(SessionMessage(types.JSONRPCError(jsonrpc="2.0", id=frame.id, error=error)))
elif frame.method == "initialize": # pragma: no branch
result = types.InitializeResult(
protocol_version=LATEST_HANDSHAKE_VERSION,
capabilities=ServerCapabilities(),
server_info=types.Implementation(name="legacy-only", version="0.0.1"),
)
await server_write.send(
SessionMessage(
types.JSONRPCResponse(
jsonrpc="2.0",
id=frame.id,
result=result.model_dump(by_alias=True, mode="json", exclude_none=True),
)
)
)
@asynccontextmanager
async def scripted_transport() -> AsyncIterator[TransportStreams]:
async with (
create_client_server_memory_streams() as ((client_read, client_write), server_streams),
anyio.create_task_group() as tg,
):
tg.start_soon(scripted_server, server_streams)
yield client_read, client_write
tg.cancel_scope.cancel()
with anyio.fail_after(5):
async with Client(scripted_transport(), mode="auto") as client:
assert client.protocol_version == LATEST_HANDSHAKE_VERSION
assert client.server_info.name == "legacy-only"
assert methods_seen == ["server/discover", "initialize", "notifications/initialized"]
@pytest.mark.anyio
async def test_modern_list_tools_drops_tools_with_invalid_x_mcp_header_but_legacy_does_not() -> None:
"""At 2026-07-28 the spec requires clients to exclude tools whose `x-mcp-header`
annotation is malformed; handshake-era sessions surface them unchanged. Two
tools are advertised — one valid, one with a non-RFC-9110-token header name —
and the modern client sees only the valid one."""
valid = types.Tool(
name="ok",
input_schema={"type": "object", "properties": {"a": {"type": "string", "x-mcp-header": "Region"}}},
)
bad = types.Tool(
name="dropme",
input_schema={"type": "object", "properties": {"a": {"type": "string", "x-mcp-header": "bad name"}}},
)
async def on_list_tools(
ctx: ServerRequestContext, params: types.PaginatedRequestParams | None
) -> types.ListToolsResult:
return types.ListToolsResult(tools=[valid, bad])
server = Server("test", on_list_tools=on_list_tools)
with anyio.fail_after(5):
async with Client(server) as client:
result = await client.list_tools()
assert [t.name for t in result.tools] == ["ok"]
async with Client(server, mode="legacy") as client:
result = await client.list_tools()
assert [t.name for t in result.tools] == ["ok", "dropme"]
def test_client_rejects_handshake_era_mode_at_construction() -> None:
"""A handshake-era protocol-version string passed as `mode=` is rejected by
`__post_init__` with a hint to use `mode='legacy'` — the version-pin path is
modern-only."""
server = MCPServer("test")
with pytest.raises(ValueError, match=r"handshake-era version; use mode='legacy'"):
Client(server, mode="2025-06-18")
with pytest.raises(ValueError, match=r"mode must be 'legacy', 'auto', or one of"):
Client(server, mode="not-a-version")
# ── SEP-2322 multi-round-trip auto-loop ────────────────────────────────────────
_NAME_SCHEMA = {"type": "object", "properties": {"name": {"type": "string"}}, "required": ["name"]}
def _name_elicitation(message: str = "What is your name?") -> types.ElicitRequest:
return types.ElicitRequest(params=types.ElicitRequestFormParams(message=message, requested_schema=_NAME_SCHEMA))
async def test_call_tool_auto_loop_dispatches_elicitation_then_returns_final_result() -> None:
"""When the server returns `InputRequiredResult` carrying an elicitation,
`Client.call_tool` routes it to `elicitation_callback` and retries
automatically — the caller sees only the terminal `CallToolResult`."""
server = MCPServer("test")
@server.tool()
async def greet(ctx: Context) -> str | types.InputRequiredResult:
responses = ctx.input_responses
if responses and "user_name" in responses:
answer = responses["user_name"]
assert isinstance(answer, types.ElicitResult)
assert answer.content is not None
return f"Hello, {answer.content['name']}!"
return types.InputRequiredResult(input_requests={"user_name": _name_elicitation()})
callback_params: list[types.ElicitRequestParams] = []
async def elicitation_callback(
context: ClientRequestContext, params: types.ElicitRequestParams
) -> types.ElicitResult | types.ErrorData:
callback_params.append(params)
assert context.request_id == "user_name" # the inputRequests key is the request id
return types.ElicitResult(action="accept", content={"name": "Ada"})
with anyio.fail_after(5):
async with Client(server, elicitation_callback=elicitation_callback) as client:
result = await client.call_tool("greet")
assert result == snapshot(
CallToolResult(content=[TextContent(text="Hello, Ada!")], structured_content={"result": "Hello, Ada!"})
)
assert len(callback_params) == 1
assert isinstance(callback_params[0], types.ElicitRequestFormParams)
assert callback_params[0].message == "What is your name?"
assert callback_params[0].requested_schema == _NAME_SCHEMA
async def test_call_tool_auto_loop_dispatches_sampling_then_returns_final_result() -> None:
"""`InputRequiredResult` with an embedded `CreateMessageRequest` is routed
to `sampling_callback` and the call retried with the model's reply."""
server = MCPServer("test")
@server.tool()
async def ask(ctx: Context) -> str | types.InputRequiredResult:
responses = ctx.input_responses
if responses and "q" in responses:
answer = responses["q"]
assert isinstance(answer, types.CreateMessageResult)
assert answer.content.type == "text"
return f"Model said: {answer.content.text}"
return types.InputRequiredResult(
input_requests={
"q": types.CreateMessageRequest(
params=types.CreateMessageRequestParams(
messages=[types.SamplingMessage(role="user", content=TextContent(text="Capital of France?"))],
max_tokens=10,
)
)
}
)
callback_params: list[types.CreateMessageRequestParams] = []
async def sampling_callback(
context: ClientRequestContext, params: types.CreateMessageRequestParams
) -> types.CreateMessageResult | types.ErrorData:
callback_params.append(params)
return types.CreateMessageResult(role="assistant", content=TextContent(text="Paris"), model="echo")
with anyio.fail_after(5):
async with Client(server, sampling_callback=sampling_callback) as client:
result = await client.call_tool("ask")
assert result == snapshot(
CallToolResult(
content=[TextContent(text="Model said: Paris")], structured_content={"result": "Model said: Paris"}
)
)
assert len(callback_params) == 1
assert callback_params[0].messages[0].content == TextContent(text="Capital of France?")
async def test_call_tool_auto_loop_dispatches_list_roots_then_returns_final_result() -> None:
"""`InputRequiredResult` with an embedded `ListRootsRequest` is routed to
`list_roots_callback` and the call retried with the returned roots."""
server = MCPServer("test")
@server.tool()
async def count_roots(ctx: Context) -> str | types.InputRequiredResult:
responses = ctx.input_responses
if responses and "roots" in responses:
answer = responses["roots"]
assert isinstance(answer, types.ListRootsResult)
return f"Client exposed {len(answer.roots)} root(s)."
return types.InputRequiredResult(input_requests={"roots": types.ListRootsRequest()})
callback_called: list[ClientRequestContext] = []
async def list_roots_callback(context: ClientRequestContext) -> types.ListRootsResult | types.ErrorData:
callback_called.append(context)
return types.ListRootsResult(roots=[types.Root(uri=FileUrl("file:///workspace"))])
with anyio.fail_after(5):
async with Client(server, list_roots_callback=list_roots_callback) as client:
result = await client.call_tool("count_roots")
assert result == snapshot(
CallToolResult(
content=[TextContent(text="Client exposed 1 root(s).")],
structured_content={"result": "Client exposed 1 root(s)."},
)
)
assert len(callback_called) == 1
assert callback_called[0].request_id == "roots"
async def test_call_tool_auto_loop_round_trips_evolving_request_state_across_three_rounds() -> None:
"""A three-round flow where each `InputRequiredResult.request_state`
encodes the round number: the driver echoes it back byte-exact, the server
advances per round, and the elicitation callback runs once per round."""
server = MCPServer("test")
@server.tool()
async def multi(ctx: Context) -> str | types.InputRequiredResult:
# Round number is the integer the server stashed in `request_state` last leg.
round_num = int(ctx.request_state) if ctx.request_state else 0
if round_num == 3:
return "done after 3 rounds"
next_round = round_num + 1
return types.InputRequiredResult(
input_requests={f"step{next_round}": _name_elicitation(f"Round {next_round}?")},
request_state=str(next_round),
)
messages: list[str] = []
async def elicitation_callback(
context: ClientRequestContext, params: types.ElicitRequestParams
) -> types.ElicitResult | types.ErrorData:
assert isinstance(params, types.ElicitRequestFormParams)
messages.append(params.message)
return types.ElicitResult(action="accept", content={"name": "x"})
with anyio.fail_after(5):
async with Client(server, elicitation_callback=elicitation_callback) as client:
result = await client.call_tool("multi")
assert result.content == [TextContent(text="done after 3 rounds")]
assert messages == ["Round 1?", "Round 2?", "Round 3?"]
async def test_call_tool_auto_loop_raises_mcp_error_when_no_callback_registered() -> None:
"""SDK-defined: with no `elicitation_callback`, the default returns
`ErrorData(INVALID_REQUEST, ...)` and the driver raises it as `MCPError`
rather than retrying."""
server = MCPServer("test")
@server.tool()
async def needs_input(ctx: Context) -> str | types.InputRequiredResult:
if ctx.input_responses:
raise NotImplementedError # unreachable: client errors before retrying
return types.InputRequiredResult(input_requests={"ask": _name_elicitation()})
async with Client(server) as client:
with anyio.fail_after(5), pytest.raises(MCPError) as exc:
await client.call_tool("needs_input")
assert exc.value.error.code == types.INVALID_REQUEST
async def test_get_prompt_auto_loop_resolves_input_required_via_callbacks() -> None:
"""`Client.get_prompt` runs the same driver as `call_tool`: an
`InputRequiredResult` from `prompts/get` is fulfilled and retried."""
async def handler(
ctx: ServerRequestContext, params: types.GetPromptRequestParams
) -> types.GetPromptResult | types.InputRequiredResult:
assert params.name == "summary"
if params.input_responses and "ask" in params.input_responses:
return GetPromptResult(messages=[PromptMessage(role="user", content=TextContent(text="ok"))])
return types.InputRequiredResult(input_requests={"ask": _name_elicitation()})
server = Server("test")
server.add_request_handler("prompts/get", types.GetPromptRequestParams, handler)
async def elicitation_callback(
context: ClientRequestContext, params: types.ElicitRequestParams
) -> types.ElicitResult | types.ErrorData:
return types.ElicitResult(action="accept", content={"name": "x"})
with anyio.fail_after(5):
async with Client(server, mode="2026-07-28", elicitation_callback=elicitation_callback) as client:
result = await client.get_prompt("summary")
assert result == snapshot(GetPromptResult(messages=[PromptMessage(role="user", content=TextContent(text="ok"))]))
async def test_read_resource_auto_loop_resolves_input_required_via_callbacks() -> None:
"""`Client.read_resource` runs the same driver as `call_tool`: an
`InputRequiredResult` from `resources/read` is fulfilled and retried."""
async def handler(
ctx: ServerRequestContext, params: types.ReadResourceRequestParams
) -> types.ReadResourceResult | types.InputRequiredResult:
assert params.uri == "memory://gated"
if params.input_responses and "ask" in params.input_responses:
return ReadResourceResult(contents=[TextResourceContents(uri="memory://gated", text="unlocked")])
return types.InputRequiredResult(input_requests={"ask": _name_elicitation()})
server = Server("test")
server.add_request_handler("resources/read", types.ReadResourceRequestParams, handler)
async def elicitation_callback(
context: ClientRequestContext, params: types.ElicitRequestParams
) -> types.ElicitResult | types.ErrorData:
return types.ElicitResult(action="accept", content={"name": "x"})
with anyio.fail_after(5):
async with Client(server, mode="2026-07-28", elicitation_callback=elicitation_callback) as client:
result = await client.read_resource("memory://gated")
assert result == snapshot(
ReadResourceResult(contents=[TextResourceContents(uri="memory://gated", text="unlocked")])
)