The "Conversation started:" line carried a bare date (%A, %B %d, %Y). Tools
that accept instants -- nutrition, calendar and similar MCP servers -- reject
naive datetimes and require an explicit UTC offset, so the model had to infer
EST vs EDT from the date alone. Near a DST boundary that is a coin flip, and a
wrong guess does not error: it silently writes the record onto the wrong day.
Append the IANA zone (when configured), the zone abbreviation and the UTC
offset, e.g.:
Conversation started: Saturday, August 15, 2026 (America/New_York, EDT, UTC-04:00)
get_timezone() returns None when no timezone is configured; in that case the
line falls back to the abbreviation and offset of the server-local (still
tz-aware) time, so behaviour is unchanged for users who never set one:
Conversation started: Saturday, August 15, 2026 (EDT, UTC-04:00)
Daily byte-stability is preserved -- the property the date-only format exists
to protect (PR #20451). Zone name, abbreviation and offset are all constant for
the whole day; they shift only at a DST transition, where a change is correct.
The static-prefix reconstruction guard in _restore_plugin_sections matches on
"\n\nConversation started:" and is unaffected by a suffix after the date.
test_datetime_is_date_only_not_minute_precision used `re.search(r":\d{2}")`
over the whole line as a proxy for "no time-of-day". A UTC offset also matches
that pattern, so the check now applies to the date portion (everything before
the zone parenthetical) and the invariant is tightened rather than relaxed:
- test_datetime_includes_utc_offset asserts the offset is present
- test_datetime_line_is_stable_across_rebuilds asserts two rebuilds in the
same day produce a byte-identical line
Fixes#87403
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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