chore: tighten mcp source typing

AGENTS.md

@@ -4,6 +4,10 @@
 
 Python baseline is 3.14 (`requires-python = ">=3.14"`). Python 3.14 syntax is allowed; do not "fix" valid new syntax just because it looks unusual.
 
+Example new syntax:
+
+- Parentheses-Free Exceptions (PEP 758) <!-- coderabbit -->
+
 ## extra fields
 
 prefer asserts actual['field'] == expected['field'] over assert actual == expected unless we know better (eg. no extra fields allowed)

src/wf_cli/context.py

@@ -282,7 +282,7 @@ def _rpc_timeout_from_optional_config(
         return override
     try:
         config = load_workflow_config(path)
-    except (FileNotFoundError, json.JSONDecodeError, ValidationError):
+    except FileNotFoundError, json.JSONDecodeError, ValidationError:
         return 30.0
     target = config.client.target
     if isinstance(target, RpcHttpTargetConfig):

src/wf_mcp/broker/service/adapters.py

@@ -12,4 +12,9 @@ from wf_sources_mcp.adapters import (
     require_adapter,
 )
 
-__all__ = ["AdapterLookupRef", "LegacyAdapterRef", "SourceAdapterRef", "require_adapter"]
+__all__ = [
+    "AdapterLookupRef",
+    "LegacyAdapterRef",
+    "SourceAdapterRef",
+    "require_adapter",
+]

src/wf_sources_mcp/adapters.py

@@ -59,4 +59,9 @@ def require_adapter(
     return adapter
 
 
-__all__ = ["AdapterLookupRef", "LegacyAdapterRef", "SourceAdapterRef", "require_adapter"]
+__all__ = [
+    "AdapterLookupRef",
+    "LegacyAdapterRef",
+    "SourceAdapterRef",
+    "require_adapter",
+]

src/wf_sources_mcp/client/source_client.py

@@ -8,9 +8,11 @@ from mcp.types import (
     CallToolResult,
     ClientNotification,
     ClientRequest,
+    GetPromptResult,
     ListPromptsResult,
     ListResourcesResult,
     ListToolsResult,
+    ReadResourceResult,
 )
 from pydantic import AnyUrl
 
@@ -21,33 +23,41 @@ if TYPE_CHECKING:
         DiscoveredPrompt,
         DiscoveredResource,
         DiscoveredTool,
-        )
+    )
     from wf_sources_mcp.sdk.protocols import ToolCallResult
 
 
 class McpClientSession(Protocol):
-    """Subset of MCP SDK ClientSession operations used by source clients."""
+    """Subset of MCP SDK ClientSession operations used by source clients.
 
+    This protocol targets the low-level MCP SDK ``ClientSession`` shape, not
+    ``fastmcp.client.Client``. FastMCP exposes higher-level convenience methods
+    with different return types; if we use it here later, wrap it in an adapter
+    instead of pretending it satisfies this session protocol.
+    """
+
+    # ClientSession stuff. we dont even use their Pagination system...
     async def list_tools(self) -> ListToolsResult: ...
 
     async def list_resources(self) -> ListResourcesResult: ...
 
     async def list_prompts(self) -> ListPromptsResult: ...
 
-    async def read_resource(self, uri: AnyUrl) -> Any: ...
+    async def read_resource(self, uri: AnyUrl) -> ReadResourceResult: ...
 
     async def get_prompt(
         self,
         name: str,
         arguments: dict[str, str] | None = None,
         /,
-    ) -> Any: ...
+    ) -> GetPromptResult: ...
 
+    # BaseSession stuff. not even complete signature, thats crazy
     async def send_request(
         self,
         request: ClientRequest,
         result_type: type[ClientResult],
-    ) -> Any: ...
+    ) -> ClientResult: ...
 
     async def send_notification(self, notification: ClientNotification) -> None: ...
 
@@ -59,6 +69,16 @@ class McpClientSession(Protocol):
     ) -> CallToolResult: ...
 
 
+if TYPE_CHECKING:
+    from mcp.client.session import ClientSession as SdkClientSession
+
+    def _typecheck_sdk_client_session(
+        session: SdkClientSession,
+    ) -> McpClientSession:
+        """Static-only guard: MCP SDK ClientSession must satisfy our subset."""
+        return session
+
+
 @dataclass(slots=True)
 class McpSourceClient:
     """Operation facade over an initialized MCP SDK ClientSession.

src/wf_sources_mcp/connections.py

@@ -131,9 +131,7 @@ def _transport_from_connection_metadata(
                 args=tuple(str(arg) for arg in cast("tuple[object, ...]", args_raw)),
                 env={
                     str(key): str(value)
-                    for key, value in cast(
+                    for key, value in cast("dict[str, object]", env_raw).items()
-                        "dict[str, object]", env_raw
-                    ).items()
                 },
                 cwd=(
                     str(connection.metadata["cwd"])
@@ -148,9 +146,7 @@ def _transport_from_connection_metadata(
                 url=url if isinstance(url, str) else str(url),  # type: ignore[arg-type]
                 headers={
                     str(key): str(value)
-                    for key, value in cast(
+                    for key, value in cast("dict[str, object]", headers_raw).items()
-                        "dict[str, object]", headers_raw
-                    ).items()
                 },
             )
         raise ValueError(

src/wf_sources_mcp/discovery.py

@@ -36,7 +36,9 @@ async def discover_connection_capabilities(
     resources = await _list_optional_capabilities(
         lambda: adapter.list_resources(connection, auth)
     )
-    prompts = await _list_optional_capabilities(lambda: adapter.list_prompts(connection, auth))
+    prompts = await _list_optional_capabilities(
+        lambda: adapter.list_prompts(connection, auth)
+    )
     metadata = await adapter.get_connection_metadata(connection, auth)
     return DiscoveredConnectionCapabilities(
         tools=tools,

tests/wf_cli/test_artifacts.py

@@ -117,9 +117,7 @@ def test_artifact_delete_confirmed_succeeds(monkeypatch) -> None:
         lambda _ctx: _Context(handlers=handlers),
     )
 
-    result = CliRunner().invoke(
+    result = CliRunner().invoke(app, ["artifact", "delete", "echo", "1", "--confirm"])
-        app, ["artifact", "delete", "echo", "1", "--confirm"]
-    )
 
     assert result.exit_code == 0, result.output
     payload = json.loads(result.output)
@@ -136,9 +134,7 @@ def test_artifact_delete_blocked_returns_blocker_ids(monkeypatch) -> None:
         lambda _ctx: _BlockedContext(handlers=handlers),
     )
 
-    result = CliRunner().invoke(
+    result = CliRunner().invoke(app, ["artifact", "delete", "echo", "1", "--confirm"])
-        app, ["artifact", "delete", "echo", "1", "--confirm"]
-    )
 
     assert result.exit_code == 0, result.output
     payload = json.loads(result.output)

tests/wf_cli/test_remote_target.py

@@ -290,7 +290,9 @@ def _patch_rpc_client_to_server(monkeypatch, server) -> None:
             ),
         )
 
-    monkeypatch.setattr(cli_context, "rpc_client_from_target", fake_rpc_client_from_target)
+    monkeypatch.setattr(
+        cli_context, "rpc_client_from_target", fake_rpc_client_from_target
+    )
 
 
 def test_wf_cap_commands_use_rpc_url_override(monkeypatch, tmp_path) -> None:
@@ -742,7 +744,9 @@ def test_wf_draft_delete_succeeds_with_confirm(monkeypatch, tmp_path) -> None:
         ],
     )
 
-    result = runner.invoke(app, [*base_args, "draft", "delete", "delete-me", "--confirm"])
+    result = runner.invoke(
+        app, [*base_args, "draft", "delete", "delete-me", "--confirm"]
+    )
 
     assert result.exit_code == 0, result.output
     payload = json.loads(result.output)

tests/wf_mcp/test_auth.py

@@ -13,7 +13,6 @@ from wf_mcp.auth import (
     neutral_auth_from_mcp,
 )
 from wf_mcp.models import AuthRecord as McpAuthRecord
-from wf_mcp.models import ConnectionConfig
 from wf_mcp.storage import FileStore
 from wf_sources_mcp.connections import McpSourceConnection
 from wf_sources_mcp.transports import StdioSourceTransport

tests/wf_mcp/test_sdk_adapter.py

@@ -40,7 +40,11 @@ class _ToolsOnlyAdapter:
         raise McpError(ErrorData(code=-32601, message="Method not found"))
 
     async def get_connection_metadata(self, connection, auth):
-        return {"server": getattr(connection, "provider", getattr(connection, "server", None))}
+        return {
+            "server": getattr(
+                connection, "provider", getattr(connection, "server", None)
+            )
+        }
 
     async def read_resource(self, connection, auth, uri):
         raise NotImplementedError

tests/wf_mcp/test_support.py

@@ -12,7 +12,7 @@ from wf_core import RuntimeContext
 from wf_core.models.steps import InputPathBinding, OutputBinding
 from wf_core.paths import GraphSourcePath, LocalPath, StatePath
 from wf_mcp.capabilities import DiscoveredPrompt, DiscoveredResource, DiscoveredTool
-from wf_mcp.models import AuthRecord, ConnectionConfig
+from wf_mcp.models import ConnectionConfig
 from wf_mcp.sdk import ToolCallResult
 
 
@@ -186,7 +186,9 @@ class FakeAdapter:
         auth,
     ) -> dict[str, Any]:
         return {
-            "server": getattr(connection, "provider", getattr(connection, "server", None)),
+            "server": getattr(
+                connection, "provider", getattr(connection, "server", None)
+            ),
             "account": connection.account,
             "auth_scheme": auth.scheme if auth is not None else None,
         }

tests/wf_mcp/workflow_surface/conftest.py

@@ -14,7 +14,6 @@ from wf_artifacts import (
 from wf_authoring import node, reducer
 from wf_mcp.broker import WfMcpService
 from wf_mcp.capabilities import DiscoveredTool
-from wf_mcp.models import AuthRecord, ConnectionConfig
 from wf_mcp.sdk import ToolCallResult
 from wf_mcp.storage import FileStore
 from wf_mcp.workflow_surface import WorkflowSurfaceHandlers
@@ -104,7 +103,11 @@ class ContentOnlyOutputAdapter:
         connection,
         auth,
     ) -> dict[str, Any]:
-        return {"server": getattr(connection, "provider", getattr(connection, "server", None))}
+        return {
+            "server": getattr(
+                connection, "provider", getattr(connection, "server", None)
+            )
+        }
 
     async def call_tool(
         self,

tests/wf_sources_mcp/test_catalog_aggregate.py

@@ -104,7 +104,11 @@ def test_combined_catalog_sorts_entries_and_serializes_payload() -> None:
     first = snapshot_from_specs(
         "zeta.default",
         specs={"echo": _echo_spec()},
-        resources=[DiscoveredResource(uri="zeta://guide", name="guide", title=None, description=None)],
+        resources=[
+            DiscoveredResource(
+                uri="zeta://guide", name="guide", title=None, description=None
+            )
+        ],
         prompts=[DiscoveredPrompt(name="prompt", title=None, description=None)],
         metadata={"order": "second"},
         fetched_at_epoch_ms=2,
@@ -113,7 +117,11 @@ def test_combined_catalog_sorts_entries_and_serializes_payload() -> None:
     second = snapshot_from_specs(
         "alpha.default",
         specs={"echo": _echo_spec()},
-        resources=[DiscoveredResource(uri="alpha://guide", name="guide", title=None, description=None)],
+        resources=[
+            DiscoveredResource(
+                uri="alpha://guide", name="guide", title=None, description=None
+            )
+        ],
         prompts=[DiscoveredPrompt(name="prompt", title=None, description=None)],
         metadata={"order": "first"},
         fetched_at_epoch_ms=1,

tests/wf_sources_mcp/test_client_transport.py

@@ -6,6 +6,7 @@ from dataclasses import dataclass
 from typing import Any
 
 import pytest
+from pydantic import AnyHttpUrl
 
 from wf_sources_mcp.auth import AuthRecord
 from wf_sources_mcp.client.transport import open_mcp_session
@@ -35,9 +36,7 @@ async def _fake_streamable_http_client(
 
 
 @asynccontextmanager
-async def _fake_client_session(
+async def _fake_client_session(read: Any, write: Any) -> AsyncIterator[_FakeSession]:
-    read: Any, write: Any
-) -> AsyncIterator[_FakeSession]:
     yield _FakeSession()
 
 
@@ -70,7 +69,7 @@ def _http_connection(
         provider="test",
         account="server",
         transport=HttpSourceTransport(
-            url=url,
+            url=AnyHttpUrl(url),
             headers=headers or {},
         ),
     )
@@ -90,6 +89,7 @@ async def test_stdio_session_initializes_before_yielding() -> None:
     connection = _stdio_connection()
 
     async with open_mcp_session(connection, None) as session:
+        assert isinstance(session, _FakeSession)
         assert session.initialized is True
 
 
@@ -116,6 +116,7 @@ async def test_stdio_env_merges_transport_and_auth_wins_on_duplicate() -> None:
     mod.stdio_client = _capturing_stdio_client  # type: ignore[assignment]
 
     async with open_mcp_session(connection, auth) as session:
+        assert isinstance(session, _FakeSession)
         assert session.initialized is True
 
     params = captured_params[0]
@@ -142,6 +143,7 @@ async def test_stdio_cwd_propagated_to_server_parameters() -> None:
     mod.stdio_client = _capturing_stdio_client  # type: ignore[assignment]
 
     async with open_mcp_session(connection, None) as session:
+        assert isinstance(session, _FakeSession)
         assert session.initialized is True
 
     assert captured_params[0].cwd == "/workspace"
@@ -152,6 +154,7 @@ async def test_http_session_initializes_before_yielding() -> None:
     connection = _http_connection()
 
     async with open_mcp_session(connection, None) as session:
+        assert isinstance(session, _FakeSession)
         assert session.initialized is True
 
 
@@ -184,6 +187,7 @@ async def test_http_auth_headers_passed_to_client(
     monkeypatch.setattr(mod, "httpx", _PatchedHttpx())
 
     async with open_mcp_session(connection, auth) as session:
+        assert isinstance(session, _FakeSession)
         assert session.initialized is True
 
     assert len(captured_clients) == 1

tests/wf_sources_mcp/test_connections.py

@@ -48,9 +48,7 @@ def test_stdio_source_transport_is_typed() -> None:
 
 
 def test_http_source_transport_is_typed() -> None:
-    transport = HttpSourceTransport.model_validate(
+    transport = HttpSourceTransport.model_validate({"url": "http://127.0.0.1:8000/mcp"})
-        {"url": "http://127.0.0.1:8000/mcp"}
-    )
 
     assert transport.kind == "http"
     assert str(transport.url) == "http://127.0.0.1:8000/mcp"

tests/wf_sources_mcp/test_discovery.py

@@ -155,7 +155,9 @@ class _BrokenResourceAdapter(_Adapter):
         raise RuntimeError("resource listing broke")
 
 
-async def test_discover_connection_capabilities_collects_all_capability_families() -> None:
+async def test_discover_connection_capabilities_collects_all_capability_families() -> (
+    None
+):
     adapter = _Adapter()
     connection = _connection()
 
@@ -172,7 +174,9 @@ async def test_discover_connection_capabilities_collects_all_capability_families
     assert adapter.seen_connections == [connection]
 
 
-async def test_discover_connection_capabilities_treats_missing_optional_families_as_empty() -> None:
+async def test_discover_connection_capabilities_treats_missing_optional_families_as_empty() -> (
+    None
+):
     capabilities = await discover_connection_capabilities(
         connection=_connection(),
         auth=None,
@@ -184,7 +188,9 @@ async def test_discover_connection_capabilities_treats_missing_optional_families
     assert capabilities.prompts == []
 
 
-async def test_discover_connection_capabilities_reraises_non_method_not_found_errors() -> None:
+async def test_discover_connection_capabilities_reraises_non_method_not_found_errors() -> (
+    None
+):
     with pytest.raises(RuntimeError, match="resource listing broke"):
         await discover_connection_capabilities(
             connection=_connection(),

tests/wf_sources_mcp/test_source_registry.py

@@ -165,7 +165,9 @@ def test_connection_config_to_registry_entry_accepts_flat_http_metadata() -> Non
 
 
 def test_connection_config_to_registry_entry_requires_transport_metadata() -> None:
-    connection = _LegacyConnectionLike(id="github.work", server="github", account="work")
+    connection = _LegacyConnectionLike(
+        id="github.work", server="github", account="work"
+    )
 
     with pytest.raises(ValueError, match="requires metadata.transport"):
         connection_config_to_registry_entry(connection)

tests/wf_transport_rpc_http/test_structure.py

@@ -40,7 +40,9 @@ def test_rpc_client_mixins_share_one_call_contract() -> None:
     for module_info in pkgutil.iter_modules(rpc_client_package.__path__):
         if module_info.name in {"__init__", "base"}:
             continue
-        module = importlib.import_module(f"wf_transport_rpc_http.client.{module_info.name}")
+        module = importlib.import_module(
+            f"wf_transport_rpc_http.client.{module_info.name}"
+        )
         for _name, value in inspect.getmembers(module, inspect.isclass):
             if value.__module__ == module.__name__:
                 assert "_call" not in value.__dict__