Okay, I need to generate a one-line commit message based on the provided diffs. Let me look at the changes carefully.

The first part of the diff shows a function `on_message` being defined. The code is inside an async function. I notice that the code block is indented, which is correct in Python. The function is decorated with `@async def`, so that's good.

Looking at the lines, I see that the function definition is followed by some code. The changes include adding a new parameter `max_length=1900` to the `ai()` function call. So the main change is modifying the `max_length` parameter from 50 to 1900.

Now, I need to determine the type of this change. Since it's adding a new parameter to a function, the appropriate commit type would be "feat" for a feature addition, "fix" if it's a bug fix, "build" for a build change, etc. In this case, it's a new parameter, so it's likely a feature enhancement.

Next, I need to craft a concise one-line message. The message should start with the correct prefix, like "feat:", and describe the change. The change is increasing the max_length from 50 to 1900, which allows longer responses.

Putting it together, the commit message should be "feat: Increase ai response length from 50 to 1900". I need to make sure it's under 72 characters. Let me count: "feat: Increase ai response length from 50 to 1900" is 40 characters, which is well within the limit.

So the final commit message is "feat: Increase ai response length from 50 to 1900".
</think>

feat: Increase ai response length from 50 to 1900