Dashboard plugin API routes (web_server._mount_plugin_api_routes) and
gateway event hooks (gateway.hooks.HookRegistry.discover_and_load) both
loaded Python files via importlib.util.spec_from_file_location +
exec_module without registering the resulting module in sys.modules.
That breaks any plugin or hook handler that uses `from __future__ import
annotations` together with a Pydantic BaseModel / dataclass / anything
that introspects `__module__`: at first request Pydantic tries to
resolve string-form type hints against the defining module's namespace,
can't find it by name, and raises:
PydanticUserError: TypeAdapter[...] is not fully defined;
you should define ... and all referenced types,
then call `.rebuild()` on the instance.
This is what broke the kanban dashboard's 'triage' button — POST
/api/plugins/kanban/tasks validated against CreateTaskBody (a Pydantic
model in a file using `from __future__ import annotations`) and
returned 500 on every click.
The fix, applied symmetrically to both loaders:
1. Compute module_name once.
2. Register the module in sys.modules BEFORE exec_module.
3. On exec_module failure, pop the half-initialized stub so subsequent
reloads don't pick up broken state.
GETs were unaffected because they don't build a body TypeAdapter, which
is why this only surfaced when users started POSTing.
718e4e2e7e