Function write_atomic 

pub fn write_atomic(
    path: &Path,
    bytes: &[u8],
    subject: &str,
) -> Result<(), WorktreeCopyError>

What: Writes one private file atomically beside its final name; a failure names subject and leaves no temporary. Why: Journals and stage claims share one rule: a reader sees a complete file or none.

In TS you’d write (pseudocode):

await writeFileAtomically({ path, bytes, subject });