Error message
In the message, %s marks a value that the engine fills in when it raises the error.
The story
The engine stopped at birth because it could not read its own description of parsing. Rush parses everything the same way: a shell command, a script, or a whole project, in one pass made of four moves. It also needs to know where a command came from, a shell or a script. The roots, their provenance, where each tree starts, the four moves and their order, and what the parser must never do: all of it is declared in parse.feml. This time, the file was unreadable, or it was missing roots, provenance, moves or prohibitions, or two moves shared a position. The order is not decoration, it is the law. Enrichment has to happen during parsing, while the original script is still at hand. That is what lets the final step be a simple consumer instead of a second parser. If the declaration cannot say what comes before what, that guarantee falls apart. The engine will not fall back on a default hidden in code. Check the path in the message, repair parse.feml, and run again.
Text from the Rush engine's error catalogue.