Keep the sampling conformance scenario live; fix roots example URIs

docs/clients/roots.mdx

@@ -24,7 +24,7 @@ from fastmcp import Client
 
 client = Client(
     "my_mcp_server.py",
-    roots=["/path/to/root1", "/path/to/root2"]
+    roots=["file:///path/to/root1", "file:///path/to/root2"]
 )
 ```
 
@@ -38,7 +38,7 @@ from fastmcp.client.roots import RequestContext
 
 async def roots_callback(context: RequestContext) -> list[str]:
     print(f"Server requested roots (Request ID: {context.request_id})")
-    return ["/path/to/root1", "/path/to/root2"]
+    return ["file:///path/to/root1", "file:///path/to/root2"]
 
 client = Client(
     "my_mcp_server.py",

tests/conformance/expected-failures.yml

@@ -21,9 +21,3 @@ server:
   # need the tool to declare which one it wants, which is an unmade API
   # decision rather than a bug.
   - tasks-mrtr-composition
-
-  # Server-initiated sampling was removed from the server API (SEP-2577), so the
-  # fixture has no `test_sampling` tool for this handshake-era scenario to drive.
-  # Modern sampling rides the guard pattern and is covered by
-  # input-required-result-basic-sampling.
-  - tools-call-sampling

tests/conformance/server.py

@@ -173,6 +173,31 @@ async def test_tool_with_progress(ctx: Context) -> str:
     return "Progress test complete."
 
 
+@server.tool(name="test_sampling")
+async def test_sampling(prompt: str, ctx: Context) -> str:
+    """Requests LLM sampling via the client.
+
+    `Context` has no `sample()` — server-initiated sampling is not part of
+    FastMCP's server API. The handshake-era wire path is still supported and
+    still shipped (the proxy relay uses it), so this fixture reaches the SDK
+    session directly to keep the scenario covered.
+    """
+    result = await ctx.session.create_message(  # ty: ignore[deprecated]
+        messages=[
+            mcp_types.SamplingMessage(
+                role="user",
+                content=mcp_types.TextContent(type="text", text=prompt),
+            )
+        ],
+        max_tokens=512,
+        related_request_id=ctx.origin_request_id,
+    )
+    text = (
+        result.content.text if isinstance(result.content, mcp_types.TextContent) else ""
+    )
+    return f"Sampling result: {text}"
+
+
 class _UserInfo(BaseModel):
     username: str
     email: str