Here is an optimized version of your code.  
Since your only function (`list_prompts`) just calls `list(self._prompts.values())`, and the profiling shows this is the main runtime, you can avoid creating a new list by returning a view (if the caller never mutates or sorts the result), or a tuple (with `tuple(self._prompts.values())`), which is slightly faster and uses less memory than a list. Document that this is a tuple now if you return it (the type annotation must be changed only if the function's return type changes).  
However, if you must keep the return type as `list`, this is basically optimal.  
To further optimize, you can return a statically cached empty list (avoid list allocation) if there are no items. This gives a minor speed boost in empty cases.

Here's the refactored code.

**Explanation:**  
- Checks for an empty dict to avoid allocating a new list in the common case of zero prompts.
- Retains list conversion for caller compatibility.
- Keeps fast native dict `values()` access.

If mutation of the returned list by the caller is never required and you control call sites, you *could*.
- Change return type to `tuple[Prompt, ...]`
- `return tuple(self._prompts.values())`  
This is slightly faster and smaller in memory, but not backward compatible.

No other meaningful optimizations can be made to this function given Python's built-in dict and memory model!