Calendar reminders open the event; phones get the Calendar panel

A reminder notification links to its day, event and occurrence
(/p/calendar?date=…&event=…&start=…). The calendar opens on that day with the
event's details showing — the full calendar on a computer; on a phone any
calendar link leads to Mail with the Calendar panel slid in (the big-screen
page never opens there), scrolled to the event, details open.

The panel's agenda kept no scroll position across re-renders: opening an
event's details lower down jumped the list back to the top. It stays put now.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/tests/plugins/test_calendar_reminders.py

@@ -104,7 +104,7 @@ async def test_due_reminders_are_sent_once(ctx) -> None:  # type: ignore[no-unty
     assert await run(MON_9 - timedelta(minutes=60)) == 1  # the 1-hour reminder
     assert sent[-1]["title"] == "Dentist"
     assert sent[-1]["body"] == "In 1 hour, 09:00 · Main St 4"
-    assert sent[-1]["url"] == "/p/calendar?date=2031-06-02" and sent[-1]["sticky"] is True
+    assert sent[-1]["url"].startswith("/p/calendar?date=2031-06-02&event=") and sent[-1]["sticky"] is True
     assert await run(MON_9 - timedelta(minutes=59)) == 0  # not again
     # The worker was down when the 10-minute reminder came due: sent late, once.
     assert await run(MON_9 - timedelta(minutes=4)) == 1

frontend/src/components/mail/RightPanel.tsx

@@ -19,6 +19,8 @@ import { usePluginContext } from "../../plugins/context";
 import { isPreviewable } from "../thread/previewKind";
 
 interface InviteSignal { guests: string[]; n: number }
+/** A day (YYYY-MM-DD) and optionally one event occurrence to show in the calendar. */
+export interface CalendarFocus { date: string; event?: string; start?: string; n: number }
 
 // Lazy: the preview bundles pdf.js — loaded only when a preview is opened.
 const AttachmentPreview = lazy(() =>
@@ -66,6 +68,7 @@ export function RightPanel({
   onClose,
   thread,
   single = false,
+  calendarFocus = null,
 }: {
   tab: PanelTab;
   onTab: (t: PanelTab) => void;
@@ -74,6 +77,8 @@ export function RightPanel({
   /** Opened as Calendar or Contacts on its own (the phone's menu): a title
    *  instead of the tabs, and Contacts starts on all contacts. */
   single?: boolean;
+  /** Calendar: open on this day with this event's details (a reminder). */
+  calendarFocus?: CalendarFocus | null;
 }) {
   const t = useT();
   // "Invite all to new event" (People tab) opens the SHARED calendar event form in
@@ -110,7 +115,7 @@ export function RightPanel({
       </div>
       {/* Calendar stays mounted (keeps its state) while hidden, so switching tabs is instant. */}
       <div className={`min-h-0 flex-1 ${tab === "calendar" ? "" : "hidden"}`}>
-        <PanelCalendar invite={invite} />
+        <PanelCalendar invite={invite} focus={calendarFocus} />
       </div>
       {tab !== "calendar" && (
         <div className="min-h-0 flex-1 overflow-y-auto">
@@ -134,13 +139,15 @@ export function RightPanel({
 // This is the shared surface: the agenda, mini-month, event popover, event form
 // and search results are the calendar app's own code, so future changes propagate.
 const CAL_BUNDLE = "/api/plugins/calendar/ui/page.js";
-function PanelCalendar({ invite }: { invite: InviteSignal | null }) {
+function PanelCalendar({ invite, focus }: { invite: InviteSignal | null; focus: CalendarFocus | null }) {
   const ref = useRef<HTMLDivElement>(null);
   const ctx = usePluginContext("calendar");
   // A phone has no use for "Open calendar in new tab".
   const mobile = useIsMobile();
-  // Remount when a new "Invite all" fires so the form opens with those guests.
+  // Remount when a new "Invite all" fires so the form opens with those guests,
+  // and when asked to show a day / event (a reminder notification).
   const inviteN = invite?.n ?? 0;
+  const focusN = focus?.n ?? 0;
   useEffect(() => {
     let alive = true;
     let cleanup: (() => void) | void;
@@ -151,11 +158,12 @@ function PanelCalendar({ invite }: { invite: InviteSignal | null }) {
         embed: "panel",
         newEventGuests: invite?.guests,
         newTabLink: !mobile,
+        focus: focus ? { date: focus.date, event: focus.event, start: focus.start } : null,
       });
     });
     return () => { alive = false; if (typeof cleanup === "function") cleanup(); };
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [ctx, inviteN, mobile]);
+  }, [ctx, inviteN, focusN, mobile]);
   return <div ref={ref} className="h-full" />;
 }
 

frontend/src/plugins/PluginPage.tsx

@@ -8,6 +8,7 @@ import { useEffect, useMemo, useRef } from "react";
 import { Navigate, useLocation } from "react-router-dom";
 
 import { useT } from "../i18n";
+import { useIsMobile } from "../lib/useIsMobile";
 import { loadBundle } from "./bundleLoader";
 import { usePluginContext } from "./context";
 import { usePluginManifest, usePluginPages } from "./manifest";
@@ -48,11 +49,20 @@ export function PluginPage() {
   const location = useLocation();
   const { data, isLoading } = usePluginManifest();
   const pages = usePluginPages();
+  const mobile = useIsMobile();
 
   // Sub-path under "/p" (e.g. "/calendar/2026-07"); match the longest page route.
   const subpath = location.pathname.replace(/^\/p/, "") || "/";
   const match = pages.find((p) => subpath === p.route || subpath.startsWith(`${p.route}/`));
 
+  // The calendar page is made for a big screen: a phone gets Mail with the
+  // Calendar panel slid in instead (a reminder's link included, with its day and
+  // event).
+  if (mobile && subpath.startsWith("/calendar")) {
+    const params = new URLSearchParams(location.search);
+    params.set("panel", "calendar");
+    return <Navigate to={`/mail?${params.toString()}`} replace />;
+  }
   if (isLoading || !data) {
     return <div className="p-8 text-app-muted">{t("common.loading")}</div>;
   }

frontend/src/routes/MailLayout.tsx

@@ -35,7 +35,7 @@ import { BackfillBanner } from "../components/BackfillBanner";
 import { Clock, NotSavedOffline, OfflineIndicator } from "../components/Offline";
 import { ThreadView } from "../components/thread/ThreadView";
 import { MailboxDisplay } from "../components/mail/MailboxDisplay";
-import { RightPanel, type PanelTab } from "../components/mail/RightPanel";
+import { RightPanel, type CalendarFocus, type PanelTab } from "../components/mail/RightPanel";
 import { ScheduledSendPane } from "../components/mail/ScheduledSendPane";
 import { useT } from "../i18n";
 import type { MessageKey } from "../i18n/en";
@@ -873,6 +873,27 @@ export function MailLayout() {
   // Deep link (e.g. Contacts "Compose"): /mail?compose=1&to=<email> opens a new,
   // maximized composer prefilled with the recipient, then strips the params.
   const [searchParams, setSearchParams] = useSearchParams();
+  // ?panel=calendar[&date=&event=&start=]: the phone's way to the calendar (the
+  // calendar page sends it here; a reminder's link carries its day and event).
+  const [calendarFocus, setCalendarFocus] = useState<CalendarFocus | null>(null);
+  useEffect(() => {
+    if (searchParams.get("panel") !== "calendar") return;
+    const date = searchParams.get("date");
+    setCalendarFocus(
+      date
+        ? {
+            date,
+            event: searchParams.get("event") ?? undefined,
+            start: searchParams.get("start") ?? undefined,
+            n: Date.now(),
+          }
+        : null,
+    );
+    if (mobile) openFromMenu("calendar");
+    else openPanel("calendar");
+    setSearchParams({}, { replace: true });
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [searchParams]);
   useEffect(() => {
     if (searchParams.get("compose") !== "1") return;
     const first = accountsQuery.data?.[0];
@@ -1713,6 +1734,7 @@ export function MailLayout() {
               onClose={() => setSheetOpen(false)}
               thread={detailQuery.data}
               single={sheetSingle}
+              calendarFocus={calendarFocus}
             />
           </div>
         </>
@@ -1721,7 +1743,13 @@ export function MailLayout() {
         <>
           <Resizer onDelta={(dx) => setRightW((w) => clampRight(w - dx))} />
           <div style={{ width: rightW }} className="shrink-0 border-l border-app-border">
-            <RightPanel tab={rightTab} onTab={setRightTab} onClose={() => setRightOpen(false)} thread={detailQuery.data} />
+            <RightPanel
+              tab={rightTab}
+              onTab={setRightTab}
+              onClose={() => setRightOpen(false)}
+              thread={detailQuery.data}
+              calendarFocus={calendarFocus}
+            />
           </div>
         </>
       )}

plugins/webmail_plugin_calendar/webmail_plugin_calendar/reminders.py

@@ -16,6 +16,7 @@ import uuid
 from collections import defaultdict
 from datetime import UTC, datetime, timedelta
 from typing import Any
+from urllib.parse import quote
 from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
 from sqlalchemy import text
@@ -94,7 +95,10 @@ async def _notify_user(
             user_id,
             title=title,
             body=body,
-            url=f"/p/calendar?date={_day(start, inst['all_day'], tz)}",
+            url=(
+                f"/p/calendar?date={_day(start, inst['all_day'], tz)}"
+                f"&event={inst['id']}&start={quote(inst['start'])}"
+            ),
             # One notification per occurrence: a later reminder replaces an earlier one.
             tag=f"event-{inst['id']}-{inst['start']}",
             sticky=True,

plugins/webmail_plugin_calendar/webmail_plugin_calendar/ui/page.js

@@ -456,6 +456,9 @@ export default function mount(el, ctx, props) {
   // any change here propagates to both places.
   const embed = !!(props && props.embed === "panel");
   const newEventGuests = (props && props.newEventGuests) || null;
+  // Open on a day, with one event's details showing (a reminder notification):
+  // { date: "YYYY-MM-DD", event: id, start: ISO of the occurrence }.
+  const focus = (props && props.focus) || null;
   // Embed: the host can drop the "Open calendar in new tab" footer (Mail on a
   // phone, where a new tab is no use).
   const newTabLink = !(props && props.newTabLink === false);
@@ -1095,6 +1098,10 @@ export default function mount(el, ctx, props) {
   // Compact single-column layout for Mail's right panel. Reuses miniMonth/agenda/
   // searchPanelHtml + the form/popover/confirm overlays exactly as the full app.
   function renderEmbed() {
+    // Re-rendering replaces the agenda: keep where it was scrolled to (else
+    // opening an event's details lower down jumped the list back to the top).
+    const prevBody = el.querySelector(".cal-embed-body");
+    const prevScroll = prevBody ? prevBody.scrollTop : 0;
     el.innerHTML = `<div class="cal-app cal-embed">
       ${panelBar()}
       ${state.search ? "" : `<div class="cal-embed-mini">${miniMonth()}</div>`}
@@ -1107,6 +1114,8 @@ export default function mount(el, ctx, props) {
       ${state.confirm ? confirmHtml() : ""}
     </div>`;
     wire();
+    const body0 = el.querySelector(".cal-embed-body");
+    if (body0 && prevScroll && !state.scrollToAnchor) body0.scrollTop = prevScroll;
     if (state.scrollToAnchor) {
       state.scrollToAnchor = false;
       const a = state.anchor;
@@ -1850,20 +1859,46 @@ export default function mount(el, ctx, props) {
   (async () => {
     await loadChrome();
     await loadCalendars();
-    // Deep link (a reminder notification): /p/calendar?date=YYYY-MM-DD opens that
+    // Deep link (a reminder notification): /p/calendar?date=YYYY-MM-DD[&event=id&start=iso]
-    // day, then strips the param so refresh is clean.
+    // opens that day with the event's details; in the panel, the same comes as
+    // props.focus. The params are stripped so a refresh is clean.
+    let target = focus;
     try {
-      const day = new URLSearchParams(window.location.search).get("date");
+      const params = new URLSearchParams(window.location.search);
-      if (!state.embed && day && /^\d{4}-\d{2}-\d{2}$/.test(day)) {
+      if (!state.embed && params.get("date")) {
-        const [y, m, d] = day.split("-").map(Number);
+        target = { date: params.get("date"), event: params.get("event"), start: params.get("start") };
-        state.anchor = startOfDay(new Date(y, m - 1, d));
-        state.mini = startOfMonth(state.anchor);
-        state.view = "day";
         window.history.replaceState({}, "", window.location.pathname);
       }
     } catch { /* ignore */ }
+    if (target && /^\d{4}-\d{2}-\d{2}$/.test(target.date || "")) {
+      const [y, m, d] = target.date.split("-").map(Number);
+      state.anchor = startOfDay(new Date(y, m - 1, d));
+      state.mini = startOfMonth(state.anchor);
+      if (state.embed) state.scrollToAnchor = true;
+      else state.view = "day";
+    }
     await loadEvents();
     render();
+    if (target && target.event) {
+      const ev = state.events.find((x) => x.id === target.event && (!target.start || x.start === target.start))
+        || state.events.find((x) => x.id === target.event);
+      if (ev) {
+        // In the panel, wait for it to finish sliding in (a phone's sheet), then
+        // bring the event into view so the details sit beside it.
+        await new Promise((r) => setTimeout(r, state.embed ? 400 : 50));
+        const block = el.querySelector(`[data-ev="${ev.id}"][data-start="${ev.start}"]`);
+        if (block) {
+          block.scrollIntoView({ block: "center" });
+          await new Promise((r) => requestAnimationFrame(() => requestAnimationFrame(r)));
+          openEvent(ev, block);
+        } else {
+          const view = el.querySelector(".cal-view") || el;
+          const r = view.getBoundingClientRect();
+          state.eventPopover = { ev, rect: { top: r.top + 24, left: r.left + 16, right: r.left + 60, bottom: r.top + 44 } };
+          render();
+        }
+      }
+    }
     // Embed mode ("Invite all to new event" from Mail's People tab): open a new-event
     // form with the given guests, using the SAME form as the calendar app.
     if (state.embed && newEventGuests && newEventGuests.length) {