fix(calendar-tool): split start/end into date+time to make event creation TZ-durable

A user reported "next Friday at 8am" landing on the wrong day. The
current `start` parameter accepts a combined ISO datetime string — when
the model emits something like `"2026-05-01T00:00:00Z"`, the parser
correctly honors the UTC tag and stores `2026-05-01 00:00 UTC`, which
displays as `2026-04-30 19:00` for a UTC-5 user. The bug isn't in our
parser; it's that we let the model TZ-tag the calendar day at all.

The fix moves the foot-gun: `create_event` and `update_event` now
prefer split fields (`start_date` + `start_time`, plus end variants).
A `YYYY-MM-DD` string carries no TZ metadata for a model to mis-tag,
and the backend builds the local datetime explicitly via
`datetime.combine(date, time, tzinfo=user_tz).astimezone(UTC)`. Strict
regex validation rejects anything with a TZ suffix on either field.

The legacy combined `start` / `end` fields are kept as a fallback so
saved tool-call payloads in conversation history still replay; new
calls are steered toward the split shape via the tool description.

7 new regression tests cover Eastern, Pacific, Tokyo (positive offset),
all-day inference, strict-shape rejection on both fields, backcompat
with the legacy `start` field, and the same fix for `update_event`.
27 of the event-related tests pass; ruff clean.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
This commit is contained in:
2026-04-29 08:16:25 -04:00
parent 3b2a0a119f
commit 611c940527
2 changed files with 395 additions and 36 deletions
+132 -36
View File
@@ -2,7 +2,8 @@
from __future__ import annotations
from datetime import datetime, timezone
import re
from datetime import date as _date, datetime, time as _time, timezone
from fabledassistant.services.events import (
create_event as events_create_event,
@@ -17,10 +18,49 @@ from fabledassistant.services.tools._registry import tool
from fabledassistant.services.tz import get_user_tz
_DATE_RE = re.compile(r"^\d{4}-\d{2}-\d{2}$")
_TIME_RE = re.compile(r"^\d{2}:\d{2}(:\d{2})?$")
async def _combine_local_in_user_tz(
user_id: int, date_str: str, time_str: str | None
) -> datetime:
"""Build a UTC datetime from separate date and time strings.
The whole point of this helper: a `YYYY-MM-DD` string carries no TZ
metadata that a model could mis-tag, so the calendar day cannot drift
across the local→UTC boundary. The wall-clock `HH:MM` likewise has no
TZ; we attach the user's local zone explicitly via ``datetime.combine``
and then convert to UTC for storage.
Strict shape validation rejects anything that isn't a bare date or a
bare time — no `2026-05-01Z`, no `08:00 UTC` slipping through.
"""
if not _DATE_RE.match(date_str):
raise ValueError(
f"start_date / end_date must be YYYY-MM-DD with no timezone; got {date_str!r}"
)
d = _date.fromisoformat(date_str)
if time_str is None or time_str == "":
t = _time(0, 0)
else:
if not _TIME_RE.match(time_str):
raise ValueError(
f"start_time / end_time must be HH:MM (or HH:MM:SS), no timezone; got {time_str!r}"
)
t = _time.fromisoformat(time_str)
user_tz = await get_user_tz(user_id)
local = datetime.combine(d, t, tzinfo=user_tz)
return local.astimezone(timezone.utc)
async def _parse_datetime_in_user_tz(
user_id: int, value: str
) -> tuple[datetime, bool]:
"""Parse a date/datetime string from the model into a UTC-aware datetime.
"""Legacy single-string parser. Kept as a fallback when the model
emits the older `start` / `end` shape; new calls should use
`start_date`+`start_time` (and `end_date`+`end_time`) which sidestep
the TZ-tagging foot-gun this parser is vulnerable to.
Naive inputs are interpreted in the **user's local timezone** and then
converted to UTC for storage. Never default to UTC for naive inputs —
@@ -38,14 +78,54 @@ async def _parse_datetime_in_user_tz(
return dt.astimezone(timezone.utc), was_date_only
async def _resolve_event_start(
user_id: int, args: dict
) -> tuple[datetime, bool]:
"""Resolve the start datetime from either the new split fields
(`start_date` + optional `start_time`) or the legacy combined `start`.
Returns ``(utc_datetime, was_date_only)``."""
if "start_date" in args and args["start_date"]:
date_str = args["start_date"]
time_str = args.get("start_time") or None
return await _combine_local_in_user_tz(user_id, date_str, time_str), time_str is None
if "start" in args and args["start"]:
return await _parse_datetime_in_user_tz(user_id, args["start"])
raise ValueError("Either start_date or start is required")
async def _resolve_event_end(
user_id: int, args: dict
) -> datetime | None:
"""Resolve the end datetime from either the new split fields or the
legacy combined `end`. Returns ``None`` when no end fields are set."""
if "end_date" in args and args["end_date"]:
date_str = args["end_date"]
time_str = args.get("end_time") or None
return await _combine_local_in_user_tz(user_id, date_str, time_str)
if "end" in args and args["end"]:
dt, _ = await _parse_datetime_in_user_tz(user_id, args["end"])
return dt
return None
@tool(
name="create_event",
description="Create a calendar event for the user. Use this when the user asks to schedule, add, or create a meeting, appointment, or event. Pass dates and datetimes in the user's local time — a bare date like '2026-09-30' is interpreted as that day in the user's configured timezone.",
description=(
"Create a calendar event for the user. Use this when the user asks "
"to schedule, add, or create a meeting, appointment, or event. "
"Always pass `start_date` (YYYY-MM-DD) and `start_time` (HH:MM) as "
"separate fields in the user's local time — never combine them and "
"never include a timezone suffix. The server attaches the user's "
"configured timezone. Omit `start_time` (or set `all_day=true`) "
"for all-day events like birthdays or holidays."
),
parameters={
"title": {"type": "string", "description": "A descriptive event title"},
"start": {"type": "string", "description": "Start date (YYYY-MM-DD) or datetime (YYYY-MM-DDTHH:MM) in the user's local time. Include a timezone offset only if the user explicitly mentions one."},
"end": {"type": "string", "description": "Optional end date or datetime in the user's local time"},
"duration": {"type": "integer", "description": "Optional duration in minutes (default 60, ignored if end is set or all_day is true)"},
"start_date": {"type": "string", "description": "Start calendar date as YYYY-MM-DD in the user's local time. No timezone suffix."},
"start_time": {"type": "string", "description": "Start wall-clock time as HH:MM (24-hour). Omit for all-day events. No timezone suffix."},
"end_date": {"type": "string", "description": "Optional end calendar date as YYYY-MM-DD."},
"end_time": {"type": "string", "description": "Optional end wall-clock time as HH:MM."},
"duration": {"type": "integer", "description": "Optional duration in minutes (default 60, ignored if end_date/end_time is set or all_day is true)"},
"description": {"type": "string", "description": "Optional event description"},
"location": {"type": "string", "description": "Optional event location"},
"color": {"type": "string", "description": "Optional hex color for the event (e.g. '#6366f1')"},
@@ -55,30 +135,31 @@ async def _parse_datetime_in_user_tz(
"attendees": {"type": "array", "items": {"type": "string"}, "description": "Optional list of attendee email addresses"},
"calendar_name": {"type": "string", "description": "Optional calendar name to create the event in. Falls back to default calendar."},
"project": {"type": "string", "description": "Optional project name to associate this event with"},
# Legacy combined fields kept for backward compatibility with saved
# tool-call payloads in conversation history. New calls should use
# start_date + start_time. Hidden from typical model output via the
# description above; still accepted by the resolver as a fallback.
"start": {"type": "string", "description": "[Deprecated] Combined start datetime — prefer start_date + start_time."},
"end": {"type": "string", "description": "[Deprecated] Combined end datetime — prefer end_date + end_time."},
},
required=["title", "start"],
required=["title"],
)
async def create_event_tool(*, user_id, arguments, **_ctx):
start_str = arguments["start"]
end_str = arguments.get("end")
all_day = arguments.get("all_day", False)
try:
# Naive dates/datetimes are interpreted in the user's local
# timezone, not UTC. Storing UTC for naive inputs caused all-day
# events to land on the previous day for negative-offset users.
start_dt, start_was_date_only = await _parse_datetime_in_user_tz(
user_id, start_str
)
except (ValueError, TypeError):
return {"success": False, "error": f"Invalid start datetime: {start_str!r}"}
start_dt, start_was_date_only = await _resolve_event_start(user_id, arguments)
except ValueError as exc:
return {"success": False, "error": str(exc)}
except TypeError as exc:
return {"success": False, "error": f"Invalid start: {exc}"}
if start_was_date_only:
all_day = True
end_dt = None
if end_str:
try:
end_dt, _ = await _parse_datetime_in_user_tz(user_id, end_str)
except (ValueError, TypeError):
return {"success": False, "error": f"Invalid end datetime: {end_str!r}"}
try:
end_dt = await _resolve_event_end(user_id, arguments)
except ValueError as exc:
return {"success": False, "error": str(exc)}
except TypeError as exc:
return {"success": False, "error": f"Invalid end: {exc}"}
project_id = None
project_name = arguments.get("project")
if project_name:
@@ -168,18 +249,29 @@ async def search_events_tool(*, user_id, arguments, **_ctx):
@tool(
name="update_event",
description="Update an existing calendar event. Use this when the user asks to change, move, reschedule, or modify an event.",
description=(
"Update an existing calendar event. Use this when the user asks to "
"change, move, reschedule, or modify an event. Pass `start_date` "
"(YYYY-MM-DD) and `start_time` (HH:MM) as separate fields in the "
"user's local time when rescheduling — never combine them, never "
"include a timezone suffix."
),
parameters={
"query": {"type": "string", "description": "Search term to find the event to update (matches against title)"},
"title": {"type": "string", "description": "New title for the event"},
"start": {"type": "string", "description": "New start datetime in ISO 8601 format"},
"end": {"type": "string", "description": "New end datetime in ISO 8601 format"},
"start_date": {"type": "string", "description": "New start calendar date as YYYY-MM-DD in the user's local time. No timezone suffix."},
"start_time": {"type": "string", "description": "New start wall-clock time as HH:MM. No timezone suffix."},
"end_date": {"type": "string", "description": "New end calendar date as YYYY-MM-DD."},
"end_time": {"type": "string", "description": "New end wall-clock time as HH:MM."},
"all_day": {"type": "boolean", "description": "Whether the event is all-day"},
"description": {"type": "string", "description": "New event description"},
"location": {"type": "string", "description": "New event location"},
"color": {"type": "string", "description": "New hex color for the event (e.g. '#6366f1')"},
"recurrence": {"type": "string", "description": "New iCalendar RRULE"},
"reminder_minutes": {"type": "integer", "description": "Reminder N minutes before the event. Pass 0 to remove an existing reminder."},
# Legacy combined fields kept for backcompat — see create_event.
"start": {"type": "string", "description": "[Deprecated] Combined start datetime — prefer start_date + start_time."},
"end": {"type": "string", "description": "[Deprecated] Combined end datetime — prefer end_date + end_time."},
},
required=["query"],
)
@@ -198,16 +290,20 @@ async def update_event_tool(*, user_id, arguments, **_ctx):
if "reminder_minutes" in arguments:
rm = arguments["reminder_minutes"]
fields["reminder_minutes"] = None if rm == 0 else rm
for dt_field, key in (("start_dt", "start"), ("end_dt", "end")):
val = arguments.get(key)
if val:
try:
# Naive datetimes are user-local, not UTC — see
# ``_parse_datetime_in_user_tz`` docstring.
dt, _ = await _parse_datetime_in_user_tz(user_id, val)
fields[dt_field] = dt
except (ValueError, TypeError):
return {"success": False, "error": f"Invalid datetime for {key}: {val!r}"}
# Resolve start: split fields preferred, legacy `start` as fallback.
if arguments.get("start_date") or arguments.get("start"):
try:
start_dt, _ = await _resolve_event_start(user_id, arguments)
except (ValueError, TypeError) as exc:
return {"success": False, "error": f"Invalid start: {exc}"}
fields["start_dt"] = start_dt
if arguments.get("end_date") or arguments.get("end"):
try:
end_dt = await _resolve_event_end(user_id, arguments)
except (ValueError, TypeError) as exc:
return {"success": False, "error": f"Invalid end: {exc}"}
if end_dt is not None:
fields["end_dt"] = end_dt
updated = await events_update_event(user_id=user_id, event_id=event_to_update.id, **fields)
if updated is None:
return {"success": False, "error": "Event not found or update failed."}