Seed the pagination cursor and preserve request _meta across skills pages

`list_skills`/`read_directory` now seed the seen-cursor set with a
caller-supplied starting cursor, so a server echoing that cursor is caught on
the first page instead of being chased a second time. Rebuilding each page
request from the caller's own params (via model_copy) also carries `_meta`
forward to every page rather than dropping it after the first.

Author: vijay

src/mcp/client/skills.py

@@ -57,11 +57,14 @@ async def list_skills(session: ClientSession, params: ListSkillsParams | None =
             its response is not SEP-2640 conformant.
     """
     _require_extension(session)
-    cursor = params.cursor if params is not None else None
+    base = params if params is not None else ListSkillsParams()
+    cursor = base.cursor
     skills: list[Skill] = []
-    seen_cursors: set[str] = set()
+    seen_cursors: set[str] = {cursor} if cursor is not None else set()
     while True:
-        page = await session.send_request(ListSkillsRequest(params=ListSkillsParams(cursor=cursor)), ListSkillsResult)
+        page = await session.send_request(
+            ListSkillsRequest(params=base.model_copy(update={"cursor": cursor})), ListSkillsResult
+        )
         validate_list_result(page)
         skills.extend(page.skills)
         if page.next_cursor is None:
@@ -109,12 +112,13 @@ async def read_directory(session: ClientSession, uri: str, params: ReadDirectory
             setting, or its response is not a valid child listing of `uri`.
     """
     _require_extension(session, directory_read=True)
-    cursor = params.cursor if params is not None else None
+    base = params if params is not None else ReadDirectoryParams(uri=uri)
+    cursor = base.cursor
     resources: list[Resource] = []
-    seen_cursors: set[str] = set()
+    seen_cursors: set[str] = {cursor} if cursor is not None else set()
     while True:
         page = await session.send_request(
-            ReadDirectoryRequest(params=ReadDirectoryParams(uri=uri, cursor=cursor)), ReadDirectoryResult
+            ReadDirectoryRequest(params=base.model_copy(update={"uri": uri, "cursor": cursor})), ReadDirectoryResult
         )
         validate_directory_result(uri, page)
         resources.extend(page.resources)

tests/client/test_skills.py

@@ -253,3 +253,46 @@ async def test_list_skills_starts_from_a_caller_supplied_cursor() -> None:
     async with Client(_server()) as client:
         skills = await list_skills(client.session, ListSkillsParams(cursor="page-2"))
     assert [s.uri for s in skills] == ["skill://other/SKILL.md"]
+
+
+async def test_list_skills_detects_a_server_repeating_the_caller_supplied_cursor() -> None:
+    """The starting cursor seeds the seen-cursor set: a server that hands back the very cursor
+    the caller resumed from is caught as a repeat on the first page, not chased a second time."""
+    calls = 0
+
+    async def handler(ctx: ServerRequestContext[Any, Any], params: ListSkillsParams) -> ListSkillsResult:
+        nonlocal calls
+        calls += 1
+        return ListSkillsResult(skills=[_skill()], next_cursor="resume-here")
+
+    server = MCPServer("catalog", extensions=[Skills(list_skills=handler, get_skill=_get_skill)])
+    async with Client(server) as client:
+        with pytest.raises(ValueError, match="repeated"):
+            await list_skills(client.session, ListSkillsParams(cursor="resume-here"))
+    assert calls == 1
+
+
+async def test_list_skills_threads_request_meta_onto_every_page() -> None:
+    """A caller-supplied `_meta` rides along with each page request, not just the first."""
+    seen_meta: list[Any] = []
+
+    async def handler(ctx: ServerRequestContext[Any, Any], params: ListSkillsParams) -> ListSkillsResult:
+        seen_meta.append(params.meta)
+        if params.cursor is None:
+            return ListSkillsResult(skills=[_skill()], next_cursor="page-2")
+        return ListSkillsResult(
+            skills=[
+                Skill(
+                    uri="skill://other/SKILL.md", frontmatter={"name": "other", "description": "d"}, resources="dynamic"
+                )
+            ],
+            next_cursor=None,
+        )
+
+    server = MCPServer("catalog", extensions=[Skills(list_skills=handler, get_skill=_get_skill)])
+    async with Client(server) as client:
+        await list_skills(client.session, ListSkillsParams(meta={"progressToken": "t"}))
+    # The transport enriches `_meta` with its own keys; what matters is the caller's token
+    # reaching the server on both the first page and the cursor-following second one.
+    assert len(seen_meta) == 2
+    assert all(m is not None and m.get("progress_token") == "t" for m in seen_meta)