hyperguild#115: a session reported "old_str is empty" with old_str that
was never empty on their end. Server-side round-trip re-verified clean
(fresh brain_edit call, real content, succeeds) — the code path itself
isn't broken, but its error left no way to tell "client sent empty" apart
from "something between the client and here lost the field" without a
second investigation. The refusal now names the raw argument byte count.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
mathiasandClaude Sonnet 5
1e57f49595