This is a comment left during a code review.
Path: nemoguardrails/actions/action_dispatcher.py
Line: 219-222

Comment:
**Duck-type check is broader than the original `Runnable` guard**

The old `isinstance(fn, Runnable)` only matched LangChain `Runnable` objects. The new check matches *any* registered action that has a callable `ainvoke` attribute, and then unconditionally calls it as `fn.ainvoke(input=params)` — the LangChain keyword argument convention. A custom action class that exposes `ainvoke` with a different signature (e.g. positional args, or no `input=` key) will never reach the `run()` fallback; it will raise a `TypeError` that is swallowed by the broad `except Exception` handler, returning `"failed"` silently.

If the intent is to keep this path strictly for LangChain `Runnable`-compatible objects, consider tightening the guard or documenting the expected calling convention in the comment:

```suggestion
                    elif hasattr(fn, "ainvoke") and callable(fn.ainvoke):  # type: ignore[union-attr]
                        # Duck-type check for objects that follow the LangChain Runnable
                        # protocol (ainvoke(input=...) signature) without importing langchain.
                        # Custom actions with a differently-signed ainvoke should use 'run' instead.
                        result = await fn.ainvoke(input=params)  # type: ignore[union-attr]
```

How can I resolve this? If you propose a fix, please make it concise.