Constant MAX_PATCH_FILE_BYTES 

pub const MAX_PATCH_FILE_BYTES: usize = _; // 5_242_880usize

Largest file apply_patch will read to apply a patch against. Deliberately well above MAX_RESPONSE_CHARS (which caps model-visible output) so a legitimately large source file stays patchable; a file past this is refused rather than patched from a partial read.