operator_ui.py called .replace() on last_update without checking type —
an integer value (written by the materializer) raised AttributeError and
silently fell back to os.path.getmtime(), which was stuck at 5/29 after a
deploy with preserved timestamps. web.py had the same class of bug but
worse: it unconditionally replaced last_update with mtime, ignoring the
JSON field entirely. Both now branch on isinstance(str) and cast numeric
values directly to float, with mtime only as a last-resort fallback.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Oskar Kapala
