Function shape_hash 

pub fn shape_hash(
    hunk: &Hunk,
    disposition_letter: u8,
    generated: bool,
    lang: &dyn Language,
) -> String

Shape key: normalised removed + added lines, the file disposition, and whether the file is generated. Returns the 12-hex sha1 used as the class key.

The disposition is in the key because a whole-file-add hunk and a modification with identical text are different shapes.

generated is in the key because a class is a unit of routing, not only a unit of text. A lockfile line and a source line can normalise to the same shape, and without this they became one class — a mixed class, neither generated nor not. The noise tier could then only ask “is every member generated?”, which such a class answers no, so it went to the model and its lockfile hunks went wherever the model put the class. That was how a generated hunk reached a focus group.

With the flag in the key, every class is wholly generated or wholly not. plan::class_is_generated becomes exact rather than a membership test that fails on the one case that matters.

The cost is stated plainly: generated is a hint (built-in list, gitattributes, repo config), so a [classify] glob now moves a class boundary rather than only a routing decision. That is config tuning classification, which is what config is for (ADR 0012); it still cannot add or remove a hunk. The gain is that the routing decision is exact.