fix(workspace/test): isolate test_load_config_basic and test_load_config_defaults from MODEL_PROVIDER env

Issue #271: when MODEL_PROVIDER=minimax is set in the environment, these two tests
fail because load_config reads MODEL_PROVIDER and overrides the model, causing:
- test_load_config_basic: expects "openai:gpt-4o", gets "minimax"
- test_load_config_defaults: expects "anthropic:claude-opus-4-7", gets "minimax"

The fix adds monkeypatch.delenv("MODEL_PROVIDER", raising=False) to both tests,
making them deterministic regardless of the host environment. Consistent with
other tests in the file that already isolate this env var (e.g.
test_runtime_config_model_falls_back_to_top_level, test_runtime_config_model_yaml_wins).

Closes: https://git.moleculesai.app/molecule-ai/molecule-core/issues/271

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace/plugins_registry/__init__.py

@@ -51,6 +51,32 @@ class AdaptorSource:
 
 def _load_module_from_path(module_name: str, path: Path):
     """Import a Python file by absolute path. Returns the module or None on failure."""
+
+    # KI-296: Before exec'ing plugin-adapter files (which import
+    # ``from plugins_registry import ...`` as a top-level name), register
+    # the molecule-runtime subpackage as ``plugins_registry`` in sys.modules.
+    # In the molecule-core workspace source this is already a top-level package,
+    # so the setdefault is a no-op. In the PyPI-installed runtime wheel
+    # (molecule-ai-workspace-runtime 0.1.129+), the package ships as
+    # ``molecule_runtime.plugins_registry`` and without this shim every
+    # plugin adapter would fail with ModuleNotFoundError.
+    import sys as _sys
+
+    if "plugins_registry" not in _sys.modules:
+        try:
+            _mr_pr = __import__("molecule_runtime.plugins_registry", fromlist=[""])
+            _sys.modules["plugins_registry"] = _mr_pr
+            # Also register submodules the adapters commonly import directly.
+            for _sub in ("builtins", "protocol", "raw_drop"):
+                _submod = getattr(_mr_pr, _sub, None)
+                if _submod is not None:
+                    _sys.modules[f"plugins_registry.{_sub}"] = _submod
+        except ImportError:
+            # molecule-runtime not installed (e.g. test environment with
+            # workspace/ on sys.path directly) — skip shim; the top-level
+            # workspace/plugins_registry package is already findable.
+            pass
+
     spec = importlib.util.spec_from_file_location(module_name, path)
     if spec is None or spec.loader is None:
         return None

workspace/tests/test_config.py

@@ -17,8 +17,9 @@ from config import (
 )
 
 
-def test_load_config_basic(tmp_path):
+def test_load_config_basic(tmp_path, monkeypatch):
     """load_config reads a YAML file and returns a WorkspaceConfig."""
+    monkeypatch.delenv("MODEL_PROVIDER", raising=False)
     config_yaml = tmp_path / "config.yaml"
     config_yaml.write_text(
         yaml.dump(
@@ -46,8 +47,9 @@ def test_load_config_basic(tmp_path):
     assert cfg.prompt_files == ["SOUL.md", "TOOLS.md"]
 
 
-def test_load_config_defaults(tmp_path):
+def test_load_config_defaults(tmp_path, monkeypatch):
     """Missing fields fall back to WorkspaceConfig defaults."""
+    monkeypatch.delenv("MODEL_PROVIDER", raising=False)
     config_yaml = tmp_path / "config.yaml"
     config_yaml.write_text(yaml.dump({}))
 

workspace/tests/test_plugins_registry.py

@@ -325,3 +325,44 @@ def test_resolve_registry_missing_module_falls_through(monkeypatch, tmp_path: Pa
     monkeypatch.setattr(pr, "_REGISTRY_ROOT", tmp_path / "empty-registry")
     _, source = pr.resolve("demo-plugin", "test_runtime", plugin_root)
     assert source == AdaptorSource.RAW_DROP
+
+
+def test_load_module_from_path_registers_plugins_registry_sys_modules(tmp_path: Path):
+    """KI-296: _load_module_from_path registers ``plugins_registry`` in sys.modules
+    before exec'ing the adapter, so adapter files that do
+    ``from plugins_registry import ...`` resolve correctly when the runtime is
+    installed from the PyPI wheel (where the package ships as
+    ``molecule_runtime.plugins_registry`` rather than a top-level ``plugins_registry``).
+    """
+    import sys as _sys
+    import plugins_registry as pr
+
+    # Create a fake adapter that imports plugins_registry at top level.
+    adapter_file = tmp_path / "fake_runtime_adapter.py"
+    adapter_file.write_text(
+        "from plugins_registry import InstallContext  # noqa: F401\n"
+        "from plugins_registry.builtins import AgentskillsAdaptor as Adaptor  # noqa: F401\n"
+    )
+
+    # Evict any pre-existing sys.modules entries for the shim keys so the
+    # import inside _load_module_from_path actually runs.
+    _saved = {
+        k: _sys.modules.pop(k, None)
+        for k in (
+            "plugins_registry", "plugins_registry.builtins",
+            "plugins_registry.protocol", "plugins_registry.raw_drop",
+            "_plugin_adaptor.test.fake_runtime",
+        )
+    }
+
+    try:
+        result = pr._load_module_from_path("_plugin_adaptor.test.fake_runtime", adapter_file)
+        assert result is not None, "module should load without ImportError"
+        assert hasattr(result, "Adaptor"), "AgentskillsAdaptor alias should be in namespace"
+    finally:
+        # Restore sys.modules state.
+        for k, v in _saved.items():
+            if v is None:
+                _sys.modules.pop(k, None)
+            else:
+                _sys.modules[k] = v