fix: message scheduling 404 and date/time picker UX

API fix: delay was embedded in the path string causing 404 — moved to
proper query param object; prefix changed from '' to the full MSC4140
unstable prefix so authedRequest builds the correct URL. Cancel and
restart endpoints fixed the same way.

Date/time picker: replaced single datetime-local (hard to use time
portion) with separate date + time inputs side by side; colorScheme:'dark'
hints the browser to render calendar/clock popups in dark mode to match
the app. Preview row now shows as a styled Primary.Container chip with
clock icon. Relative time ("in 2h 15m") shown below the label.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/features/room/ScheduleMessageModal.tsx

@@ -57,14 +57,32 @@ function formatSendAt(sendAt: Date): string {
   return `${sendAt.toLocaleDateString()} at ${timeStr}`;
 }
 
-function toLocalDatetimeValue(date: Date): string {
+function toLocalDate(date: Date): string {
   const pad = (n: number) => String(n).padStart(2, '0');
-  return (
-    `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}` +
-    `T${pad(date.getHours())}:${pad(date.getMinutes())}`
-  );
+  return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}`;
 }
 
+function toLocalTime(date: Date): string {
+  const pad = (n: number) => String(n).padStart(2, '0');
+  return `${pad(date.getHours())}:${pad(date.getMinutes())}`;
+}
+
+// Shared style for date/time inputs — dark-mode calendar/clock popup via colorScheme.
+const pickerInputStyle = (c: typeof color, cfg: typeof config): React.CSSProperties => ({
+  background: c.SurfaceVariant.Container,
+  color: c.SurfaceVariant.OnContainer,
+  border: `${cfg.borderWidth.B300} solid ${c.SurfaceVariant.ContainerLine}`,
+  borderRadius: cfg.radii.R300,
+  padding: `${cfg.space.S200} ${cfg.space.S300}`,
+  fontSize: '0.875rem',
+  width: '100%',
+  boxSizing: 'border-box',
+  outline: 'none',
+  fontFamily: 'inherit',
+  // Hint browser to render the calendar/clock popup in dark mode
+  colorScheme: 'dark',
+});
+
 export function ScheduleMessageModal({
   roomId,
   initialBody,
@@ -84,42 +102,43 @@ export function ScheduleMessageModal({
     return d;
   };
 
-  const [datetimeValue, setDatetimeValue] = useState<string>(() =>
-    toLocalDatetimeValue(defaultDate()),
-  );
+  const def = defaultDate();
+  const [dateValue, setDateValue] = useState<string>(() => toLocalDate(def));
+  const [timeValue, setTimeValue] = useState<string>(() => toLocalTime(def));
+
+  const getSendAt = useCallback((): Date | null => {
+    if (!dateValue || !timeValue) return null;
+    const dt = new Date(`${dateValue}T${timeValue}:00`);
+    return Number.isNaN(dt.getTime()) ? null : dt;
+  }, [dateValue, timeValue]);
 
   const [preview, setPreview] = useState<{ label: string; relative: string } | null>(null);
 
-  const updatePreview = useCallback((value: string) => {
-    if (!value) {
+  const updatePreview = useCallback(() => {
+    const sendAt = getSendAt();
+    if (!sendAt) {
       setPreview(null);
       return;
     }
-    const sendAt = new Date(value);
-    const now = Date.now();
-    const diffMs = sendAt.getTime() - now;
-    if (Number.isNaN(sendAt.getTime()) || diffMs < 60_000) {
+    const diffMs = sendAt.getTime() - Date.now();
+    if (diffMs < 60_000) {
       setPreview(null);
       return;
     }
     setPreview({ label: formatSendAt(sendAt), relative: formatRelativeTime(diffMs) });
-  }, []);
+  }, [getSendAt]);
 
   useEffect(() => {
-    updatePreview(datetimeValue);
-  }, [datetimeValue, updatePreview]);
+    updatePreview();
+  }, [updatePreview]);
 
   const handleSubmit: FormEventHandler<HTMLFormElement> = async (e) => {
     e.preventDefault();
     if (submitting) return;
 
-    if (!datetimeValue) {
-      setError('Please select a date and time.');
-      return;
-    }
-    const sendAt = new Date(datetimeValue);
-    if (Number.isNaN(sendAt.getTime())) {
-      setError('Invalid date/time.');
+    const sendAt = getSendAt();
+    if (!sendAt) {
+      setError('Please select a valid date and time.');
       return;
     }
     const diffMs = sendAt.getTime() - Date.now();
@@ -127,7 +146,6 @@ export function ScheduleMessageModal({
       setError('Scheduled time must be at least 1 minute in the future.');
       return;
     }
-
     if (!messageText.trim()) {
       setError('Please enter a message to schedule.');
       return;
@@ -222,42 +240,65 @@ export function ScheduleMessageModal({
                 />
               </Box>
 
-              {/* Datetime picker */}
+              {/* Date + Time pickers */}
               <Box direction="Column" gap="100">
-                <Text as="label" htmlFor="schedule-datetime" size="L400">
-                  Send at
-                </Text>
-                <input
-                  id="schedule-datetime"
-                  type="datetime-local"
-                  value={datetimeValue}
-                  onChange={(e) => setDatetimeValue(e.target.value)}
-                  style={{
-                    background: color.SurfaceVariant.Container,
-                    color: color.SurfaceVariant.OnContainer,
-                    border: `${config.borderWidth.B300} solid ${color.SurfaceVariant.ContainerLine}`,
-                    borderRadius: config.radii.R300,
-                    padding: `${config.space.S200} ${config.space.S300}`,
-                    fontSize: '0.875rem',
-                    width: '100%',
-                    boxSizing: 'border-box',
-                    outline: 'none',
-                  }}
-                />
+                <Text size="L400">Send at</Text>
+                <Box gap="200">
+                  <Box direction="Column" gap="100" style={{ flex: 1 }}>
+                    <Text as="label" htmlFor="schedule-date" size="T200" style={{ opacity: 0.7 }}>
+                      Date
+                    </Text>
+                    <input
+                      id="schedule-date"
+                      type="date"
+                      value={dateValue}
+                      onChange={(e) => setDateValue(e.target.value)}
+                      style={pickerInputStyle(color, config)}
+                    />
+                  </Box>
+                  <Box direction="Column" gap="100" style={{ flex: 1 }}>
+                    <Text as="label" htmlFor="schedule-time" size="T200" style={{ opacity: 0.7 }}>
+                      Time
+                    </Text>
+                    <input
+                      id="schedule-time"
+                      type="time"
+                      value={timeValue}
+                      onChange={(e) => setTimeValue(e.target.value)}
+                      style={pickerInputStyle(color, config)}
+                    />
+                  </Box>
+                </Box>
               </Box>
 
               {/* Preview */}
               {preview ? (
-                <Box direction="Column" gap="100">
-                  <Text size="T300" style={{ opacity: 0.7 }}>
-                    {preview.label}
-                  </Text>
-                  <Text size="T200" style={{ opacity: 0.5 }}>
-                    ({preview.relative})
-                  </Text>
+                <Box
+                  alignItems="Center"
+                  gap="200"
+                  style={{
+                    padding: `${config.space.S100} ${config.space.S200}`,
+                    borderRadius: config.radii.R300,
+                    background: color.Primary.Container,
+                    border: `1px solid ${color.Primary.ContainerLine}`,
+                  }}
+                >
+                  <Icon
+                    src={Icons.Clock}
+                    size="100"
+                    style={{ color: color.Primary.OnContainer, flexShrink: 0 }}
+                  />
+                  <Box direction="Column">
+                    <Text size="T300" style={{ color: color.Primary.OnContainer }}>
+                      {preview.label}
+                    </Text>
+                    <Text size="T200" style={{ color: color.Primary.OnContainer, opacity: 0.7 }}>
+                      {preview.relative}
+                    </Text>
+                  </Box>
                 </Box>
               ) : (
-                datetimeValue && (
+                (dateValue || timeValue) && (
                   <Text size="T200" style={{ color: color.Critical.Main }}>
                     Must be at least 1 minute in the future
                   </Text>

src/app/utils/scheduledMessages.ts

@@ -14,11 +14,12 @@ export async function scheduleMessage(
   content: IContent,
   sendAtMs: number,
 ): Promise<string> {
-  const delayMs = sendAtMs - Date.now();
+  const delayMs = Math.max(1000, Math.round(sendAtMs - Date.now()));
   const txnId = `sched_${Date.now()}_${Math.random().toString(36).slice(2)}`;
-  const path = `/_matrix/client/unstable/org.matrix.msc4140/rooms/${encodeURIComponent(roomId)}/send/m.room.message/${txnId}?delay=${Math.max(1000, Math.round(delayMs))}`;
-  const res = (await mx.http.authedRequest(Method.Put, path, undefined, content, {
-    prefix: '',
+  // Use the path relative to the MSC4140 prefix — authedRequest prepends prefix to path.
+  const path = `/rooms/${encodeURIComponent(roomId)}/send/m.room.message/${txnId}`;
+  const res = (await mx.http.authedRequest(Method.Put, path, { delay: delayMs }, content, {
+    prefix: '/_matrix/client/unstable/org.matrix.msc4140',
   })) as { delay_id: string };
   return res.delay_id;
 }
@@ -29,17 +30,27 @@ export async function scheduleMessage(
  * @param delayId - The delay_id from scheduleMessage
  */
 export async function cancelScheduledMessage(mx: MatrixClient, delayId: string): Promise<void> {
-  const path = `/_matrix/client/unstable/org.matrix.msc4140/delayed_events/${encodeURIComponent(delayId)}`;
-  await mx.http.authedRequest(Method.Post, path, undefined, { action: 'cancel' }, { prefix: '' });
+  const path = `/delayed_events/${encodeURIComponent(delayId)}`;
+  await mx.http.authedRequest(
+    Method.Post,
+    path,
+    undefined,
+    { action: 'cancel' },
+    {
+      prefix: '/_matrix/client/unstable/org.matrix.msc4140',
+    },
+  );
 }
 
-/**
- * Restart (refresh heartbeat) a scheduled message via MSC4140.
- * Resets the delay timer from now.
- * @param mx - Matrix client instance
- * @param delayId - The delay_id from scheduleMessage
- */
 export async function restartScheduledMessage(mx: MatrixClient, delayId: string): Promise<void> {
-  const path = `/_matrix/client/unstable/org.matrix.msc4140/delayed_events/${encodeURIComponent(delayId)}`;
-  await mx.http.authedRequest(Method.Post, path, undefined, { action: 'restart' }, { prefix: '' });
+  const path = `/delayed_events/${encodeURIComponent(delayId)}`;
+  await mx.http.authedRequest(
+    Method.Post,
+    path,
+    undefined,
+    { action: 'restart' },
+    {
+      prefix: '/_matrix/client/unstable/org.matrix.msc4140',
+    },
+  );
 }