feat(mcp): assemble the 8-tool toolkit with capability gating, proven via real dispatch

Also fixes async-test DB isolation: test_mcp_toolkit.py drives real MCP
dispatch, which runs tool functions' ORM calls on a sync_to_async worker
thread outside pytest-django's per-test atomic transaction, so writes
committed there weren't rolled back and leaked into later tests. Sets
DJANGO_ALLOW_ASYNC_UNSAFE for the async ORM setup calls and flushes the
Printer table after this file's tests via conftest.py.

tests/conftest.py

@@ -0,0 +1,30 @@
+"""Suite-wide test fixtures.
+
+test_mcp_toolkit.py drives real MCP dispatch through `mcp.client.Client`,
+which routes each tool call's synchronous Django ORM work through
+`sync_to_async` onto its own dedicated worker thread rather than the test's
+own thread. pytest-django's `db` fixture isolates each test by wrapping it in
+an outer atomic transaction on *its* thread's connection and rolling that
+back afterwards -- but the worker thread opens a separate, thread-local
+connection that was never part of that transaction, so writes made through
+it commit for real and survive into later tests (e.g. Printer rows from
+test_mcp_toolkit.py leaking into test_resolve_printer_device.py's counts).
+
+This fixture flushes bambu_run's Printer table after each test in that file
+specifically, restoring isolation without touching the test file itself
+(which mirrors mcp-gate's proven end-to-end test pattern verbatim).
+"""
+from __future__ import annotations
+
+import pytest
+
+
+@pytest.fixture(autouse=True)
+def _isolate_async_mcp_dispatch_writes(request, django_db_blocker):
+    yield
+    if request.node.module.__name__ != "tests.test_mcp_toolkit":
+        return
+    with django_db_blocker.unblock():
+        from bambu_run.models import Printer
+
+        Printer.objects.all().delete()

tests/settings.py

@@ -1,4 +1,16 @@
 """Minimal Django settings for running bambu_run's pytest suite (in-memory SQLite)."""
+import os
+
+# test_mcp_toolkit.py drives real MCP dispatch through `mcp.client.Client`,
+# which runs the test body on the asyncio event loop (via pytest-anyio) while
+# still using plain synchronous Django ORM calls (Printer.objects.create(),
+# and the ORM calls inside the tool functions themselves). Django's asyncio
+# safety net treats any sync ORM call made while an event loop is running as
+# unsafe by default. It's genuinely safe here: sqlite is in-memory, tests run
+# single-threaded, and there's no concurrent request interleaving to corrupt
+# a shared connection. Set at settings-import time (before any test body
+# runs) rather than per-test, since Django reads this env var at call time.
+os.environ.setdefault("DJANGO_ALLOW_ASYNC_UNSAFE", "1")
 
 SECRET_KEY = "test-secret-key"
 

tests/test_mcp_toolkit.py

@@ -0,0 +1,83 @@
+"""Proves this toolkit's capability assignments are wired correctly through
+real MCP dispatch -- not by calling tool functions directly. See
+~/src/mcp-gate/tests/test_end_to_end.py for the pattern this is modeled on;
+mcp-gate's own HTTP-shaped dispatch machinery is already tested there, so
+this file only needs the stdio-shaped Client, which is enough to drive
+server.middleware and prove which tools this toolkit's capability tags
+actually gate.
+"""
+import pytest
+from mcp.client import Client
+from mcp.shared.exceptions import MCPError
+
+from mcp_gate import Gate, OpenIdentity
+
+from bambu_run.mcp.toolkit import build_toolkit
+from bambu_run.models import Printer
+
+pytestmark = pytest.mark.anyio
+
+
+@pytest.fixture
+def anyio_backend():
+    return "asyncio"
+
+
+async def test_full_capability_caller_sees_all_eight_tools(db):
+    Printer.objects.create(name="RNL-H2C", model="H2C", is_active=True)
+    gate = Gate(
+        name="test",
+        toolkits=[build_toolkit()],
+        identity=OpenIdentity(["read_printer", "read_print_history", "read_filament"]),
+    )
+    server = gate.build_server()
+
+    async with Client(server, mode="legacy") as client:
+        result = await client.list_tools()
+
+    names = {t.name for t in result.tools}
+    assert names == {
+        "get_printer_status", "get_metrics_history", "get_hardware_health",
+        "list_print_jobs", "get_print_job", "get_print_statistics",
+        "list_filaments", "get_filament",
+    }
+
+
+async def test_read_printer_only_caller_cannot_see_or_call_filament_tool(db):
+    Printer.objects.create(name="RNL-H2C", model="H2C", is_active=True)
+    gate = Gate(
+        name="test",
+        toolkits=[build_toolkit()],
+        identity=OpenIdentity(["read_printer"]),
+    )
+    server = gate.build_server()
+
+    async with Client(server, mode="legacy") as client:
+        visible = await client.list_tools()
+        visible_names = {t.name for t in visible.tools}
+        assert "list_filaments" not in visible_names
+        assert "get_printer_status" in visible_names
+
+        with pytest.raises(MCPError):
+            await client.call_tool("list_filaments", {})
+
+
+async def test_read_printer_caller_can_call_get_printer_status(db):
+    Printer.objects.create(name="RNL-H2C", model="H2C", is_active=True)
+    gate = Gate(
+        name="test",
+        toolkits=[build_toolkit()],
+        identity=OpenIdentity(["read_printer"]),
+    )
+    server = gate.build_server()
+
+    async with Client(server, mode="legacy") as client:
+        result = await client.call_tool("get_printer_status", {})
+        assert result is not None
+
+
+def test_build_toolkit_has_no_name_collisions():
+    # Toolkit.tool() raises ValueError on a name collision at registration
+    # time -- building it twice without raising is itself the assertion.
+    build_toolkit()
+    build_toolkit()