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Implement SEP-2663 tasks extension: TasksExtension, poll-based task lifecycle
TasksExtension serves io.modelcontextprotocol/tasks on the extension API: a decide-and-task tools/call interceptor (era-gated to modern connections), tasks/get with inlined results and inputRequests, tasks/update delivering poll-based in-task elicitation, tasks/cancel, durable creation, and auth-scoped task isolation. Wire models validate against the vendored ext-tasks schema. Worker-side Context hooks are refcounted so sibling servers cannot strand each other's workers. Co-Authored-By: Claude <noreply@anthropic.com>
This commit is contained in:
Jeremiah Lowin
parent
6fce4e538f
commit
5fa2883670
72 changed files with 3908 additions and 6512 deletions
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@ -1,37 +1,54 @@
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"""
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Tests for MCP SEP-1686 task protocol behavior through proxy servers.
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Tests for SEP-2663 task behavior through proxy servers.
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Proxy servers explicitly forbid task-augmented execution. All proxy components
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(tools, prompts, resources) have task_config.mode="forbidden".
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Clients connecting through proxies can:
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- Execute tools/prompts/resources normally (sync execution)
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- NOT use task-augmented execution (task=True fails gracefully for tools,
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raises MCPError for prompts/resources)
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SEP-2663 tasks are tools-only. Proxy servers force every proxied tool to
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`task_config.mode="forbidden"`, so a tool that is `task=True` on the backend
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runs *synchronously* through the proxy and is never tasked — even when the
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client opts the tasks extension in for the request.
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"""
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import pytest
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from mcp.shared.exceptions import MCPError
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from mcp_types import TextContent, TextResourceContents
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from docket import Docket
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from fastmcp_tasks.models import CreateTaskResult
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from fastmcp import FastMCP
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from fastmcp.client import Client
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from fastmcp.client.transports import FastMCPTransport
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from fastmcp.server import create_proxy
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pytestmark = pytest.mark.skip(
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reason="Phase 3: requires TasksExtension (SEP-2663 adapter)"
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from fastmcp.tools.base import ToolResult
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from fastmcp_tasks import TasksExtension
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from tests.tasks.task_helpers import (
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_opted_in_request,
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auth_scope,
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running_task_server,
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)
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@pytest.fixture(autouse=True)
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def reset_docket_memory_server():
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"""Force a fresh memory:// Docket server bound to each test's event loop."""
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if hasattr(Docket, "_memory_server"):
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delattr(Docket, "_memory_server")
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yield
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if hasattr(Docket, "_memory_server"):
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delattr(Docket, "_memory_server")
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async def call_tool_with_optin(server: FastMCP, name: str, arguments: dict):
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"""Run a `tools/call` with the tasks opt-in bound into the request context."""
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with auth_scope(None), _opted_in_request(name, arguments, None):
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return await server.call_tool(name, arguments)
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@pytest.fixture
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def backend_server() -> FastMCP:
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"""Create a backend server with task-enabled components.
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"""A backend server with a task-enabled tool.
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The backend has tasks enabled, but the proxy should NOT forward
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task execution - it should treat all components as forbidden.
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The backend has tasks enabled, but the proxy must NOT forward task
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execution — it treats every proxied tool as forbidden.
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"""
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mcp = FastMCP("backend-server")
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mcp.add_extension(TasksExtension())
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@mcp.tool(task=True)
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async def add_numbers(a: int, b: int) -> int:
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@ -43,154 +60,57 @@ def backend_server() -> FastMCP:
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"""Tool that only supports synchronous execution."""
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return f"sync: {message}"
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@mcp.prompt(task=True)
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async def greeting_prompt(name: str) -> str:
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"""A prompt that can execute as a task."""
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return f"Hello, {name}! Welcome to the system."
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@mcp.resource("data://info.txt", task=True)
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async def info_resource() -> str:
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"""A resource that can be read as a task."""
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return "Important information from the backend"
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@mcp.resource("data://user/{user_id}.json", task=True)
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async def user_resource(user_id: str) -> str:
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"""A resource template that can execute as a task."""
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return f'{{"id": "{user_id}", "name": "User {user_id}"}}'
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return mcp
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@pytest.fixture
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def proxy_server(backend_server: FastMCP) -> FastMCP:
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"""Create a proxy server that forwards to the backend."""
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return create_proxy(FastMCPTransport(backend_server))
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"""A proxy server that forwards to the backend, with tasks advertised."""
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proxy = create_proxy(FastMCPTransport(backend_server))
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proxy.add_extension(TasksExtension())
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return proxy
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class TestProxyToolsSyncExecution:
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"""Test that tools work normally through proxy (sync execution)."""
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"""Tools work normally through the proxy (synchronous execution)."""
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async def test_tool_sync_execution_works(self, proxy_server: FastMCP):
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"""Tool called without task=True works through proxy."""
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async with Client(proxy_server, mode="legacy") as client:
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"""A tool called without opting in works through the proxy."""
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async with Client(proxy_server) as client:
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result = await client.call_tool("add_numbers", {"a": 5, "b": 3})
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assert "8" in str(result)
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async def test_sync_only_tool_works(self, proxy_server: FastMCP):
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"""Sync-only tool works through proxy."""
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async with Client(proxy_server, mode="legacy") as client:
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"""A sync-only tool works through the proxy."""
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async with Client(proxy_server) as client:
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result = await client.call_tool("sync_only_tool", {"message": "test"})
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assert "sync: test" in str(result)
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class TestProxyToolsTaskForbidden:
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"""Test that tools with task=True are forbidden through proxy."""
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"""A proxied tool never tasks, even when the client opts in."""
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async def test_tool_task_returns_error_immediately(self, proxy_server: FastMCP):
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"""Tool called with task=True through proxy returns error immediately."""
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async with Client(proxy_server, mode="legacy") as client:
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task = await client.call_tool(
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"add_numbers", {"a": 5, "b": 3}, task=True, raise_on_error=False
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)
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# Should return immediately (forbidden behavior)
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assert task.returned_immediately
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# Result should be an error
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result = await task.result()
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assert result.is_error
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async def test_sync_only_tool_task_returns_error_immediately(
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async def test_task_enabled_tool_runs_sync_through_proxy(
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self, proxy_server: FastMCP
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):
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"""Sync-only tool with task=True also returns error immediately."""
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async with Client(proxy_server, mode="legacy") as client:
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task = await client.call_tool(
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"sync_only_tool",
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{"message": "test"},
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task=True,
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raise_on_error=False,
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"""A backend `task=True` tool runs sync through the forbidden proxy."""
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async with running_task_server(proxy_server):
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result = await call_tool_with_optin(
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proxy_server, "add_numbers", {"a": 5, "b": 3}
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)
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assert task.returned_immediately
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result = await task.result()
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assert result.is_error
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# The forbidden proxy tool declines to task even with the opt-in.
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assert not isinstance(result, CreateTaskResult)
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assert isinstance(result, ToolResult)
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assert result.structured_content == {"result": 8}
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async def test_sync_only_tool_runs_sync_through_proxy(self, proxy_server: FastMCP):
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"""A sync-only tool also runs sync through the proxy with the opt-in."""
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async with running_task_server(proxy_server):
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result = await call_tool_with_optin(
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proxy_server, "sync_only_tool", {"message": "test"}
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)
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class TestProxyPromptsSyncExecution:
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"""Test that prompts work normally through proxy (sync execution)."""
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async def test_prompt_sync_execution_works(self, proxy_server: FastMCP):
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"""Prompt called without task=True works through proxy."""
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async with Client(proxy_server, mode="legacy") as client:
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result = await client.get_prompt("greeting_prompt", {"name": "Alice"})
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assert isinstance(result.messages[0].content, TextContent)
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assert "Hello, Alice!" in result.messages[0].content.text
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class TestProxyPromptsTaskForbidden:
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"""Test that prompts with task=True are forbidden through proxy."""
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@pytest.mark.xfail(
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reason="SDK v2 has no `task` field on GetPromptRequestParams / "
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"ReadResourceRequestParams; prompt/resource task submission is not "
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"wire-expressible and always graceful-degrades (sdk-feedback #3).",
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strict=True,
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)
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async def test_prompt_task_raises_mcp_error(self, proxy_server: FastMCP):
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"""Prompt called with task=True through proxy raises MCPError."""
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async with Client(proxy_server, mode="legacy") as client:
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with pytest.raises(MCPError) as exc_info:
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await client.get_prompt("greeting_prompt", {"name": "Alice"}, task=True)
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assert "does not support task-augmented execution" in str(exc_info.value)
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class TestProxyResourcesSyncExecution:
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"""Test that resources work normally through proxy (sync execution)."""
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async def test_resource_sync_execution_works(self, proxy_server: FastMCP):
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"""Resource read without task=True works through proxy."""
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async with Client(proxy_server, mode="legacy") as client:
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result = await client.read_resource("data://info.txt")
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assert isinstance(result[0], TextResourceContents)
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assert "Important information from the backend" in result[0].text
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async def test_resource_template_sync_execution_works(self, proxy_server: FastMCP):
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"""Resource template without task=True works through proxy."""
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async with Client(proxy_server, mode="legacy") as client:
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result = await client.read_resource("data://user/42.json")
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assert isinstance(result[0], TextResourceContents)
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assert '"id": "42"' in result[0].text
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class TestProxyResourcesTaskForbidden:
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"""Test that resources with task=True are forbidden through proxy."""
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@pytest.mark.xfail(
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reason="SDK v2 has no `task` field on GetPromptRequestParams / "
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"ReadResourceRequestParams; prompt/resource task submission is not "
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"wire-expressible and always graceful-degrades (sdk-feedback #3).",
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strict=True,
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)
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async def test_resource_task_raises_mcp_error(self, proxy_server: FastMCP):
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"""Resource read with task=True through proxy raises MCPError."""
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async with Client(proxy_server, mode="legacy") as client:
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with pytest.raises(MCPError) as exc_info:
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await client.read_resource("data://info.txt", task=True)
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assert "does not support task-augmented execution" in str(exc_info.value)
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@pytest.mark.xfail(
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reason="SDK v2 has no `task` field on GetPromptRequestParams / "
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"ReadResourceRequestParams; prompt/resource task submission is not "
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"wire-expressible and always graceful-degrades (sdk-feedback #3).",
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strict=True,
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)
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async def test_resource_template_task_raises_mcp_error(self, proxy_server: FastMCP):
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"""Resource template with task=True through proxy raises MCPError."""
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async with Client(proxy_server, mode="legacy") as client:
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with pytest.raises(MCPError) as exc_info:
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await client.read_resource("data://user/42.json", task=True)
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assert "does not support task-augmented execution" in str(exc_info.value)
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assert not isinstance(result, CreateTaskResult)
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assert isinstance(result, ToolResult)
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assert result.structured_content == {"result": "sync: test"}
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