Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
A step in your script met a text that did not fit in its window, and rush chose to stop. Here is the story. Some builtins do their work inside a fixed-size window. The path builtin joins its pieces inside one. Sort compares its members inside one. Usually your text fits comfortably. But when a text is wider than the window, there is a tempting shortcut: cut it at the edge and carry on. Rush never takes that shortcut, because the consequences can be quiet and serious. A clipped path points to a different file than the one you meant. A clipped member sorts into the wrong place, and your list looks fine but is wrong. So it refuses, naming the step in the message and the window that was too narrow in the second slot. Picture joining a folder name with a file name that is thousands of characters long. The fix is to shorten the text, or split the work into smaller pieces. If the text is that long because of a bug, perhaps a loop that kept appending, this message just helped you find it.
Text from the Rush engine's error catalogue.