a time slot naming no hour is asked about, never filled (V-579)

Both parsers answer a bare day word with that day at the current minute, so "на
завтра" set a reminder at 01:38, the minute he happened to be speaking. The gate
is textual now: NamesAnHour reads the sentence, and the slot stays empty when
nobody said an hour.

Beside it, NamesAnInterval and HourIsAmbiguous, which the owner's commit rule
reads. "на" joins "в" as a frame around a spoken hour in both parsers, a clock
keeps its meaning with a full stop after it, and the stub applies a day word and
a part-of-day qualifier from anywhere in the sentence rather than only from the
token after the hour.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/router/dateparser.go

@@ -54,7 +54,9 @@ try:
     # часов" is read as seven hours from now. Only a qualifier (already an
     # am/pm above) or a colon makes it read the hour, so give it the colon.
     # English "at 7" fails identically, so both prepositions are rewritten.
-    text = re.sub(r'(?<![\w:])(в|во|at)\s+([01]?\d|2[0-3])(?:\s+час(?:а|ов)?)?(?![\d:.\w])',
+    # "на 9" is the same hour said with the other preposition, and it was not
+    # read at all until V-579: "в 9" set the reminder and "на 9" did not.
+    text = re.sub(r'(?<![\w:])(в|во|на|at)\s+([01]?\d|2[0-3])(?:\s+час(?:а|ов)?)?(?![\d:.\w])',
                   lambda m: '%s %02d:00' % (m.group(1), int(m.group(2))), text, flags=re.IGNORECASE)
     settings = {'PREFER_DATES_FROM': 'future', 'RELATIVE_BASE': now}
     # Two-step: search_dates finds the date substring in text,

internal/router/slots.go

@@ -55,7 +55,11 @@ func (e Extractor) Extract(ctx context.Context, intent Intent, utterance string,
 	switch intent {
 	case IntentReminder:
 		if e.Time != nil {
-			if t, ok, err := e.Time.Parse(ctx, utterance, now); err == nil && ok {
+			// NamesAnHour is the gate, not the parser's ok (V-577, V-579). A
+			// sentence that names a day and no hour parses to that day at the
+			// current minute, and filling the slot with it invents the answer
+			// she asked for. Left empty, the daemon asks.
+			if t, ok, err := e.Time.Parse(ctx, utterance, now); err == nil && ok && NamesAnHour(utterance) {
 				s.Time = t
 				s.HasTime = true
 			}
@@ -171,6 +175,11 @@ func afterWord(s, w string) string {
 	return ""
 }
 
+// hourPrepositions — the words a spoken hour sits behind. Three, and no more:
+// the lexicon's frame set is much wider, and a word goes in here only when the
+// number after it is an hour of the day rather than a count of anything.
+var hourPrepositions = map[string]bool{"в": true, "во": true, "на": true}
+
 // StubDateTimeParser — a tiny relative/absolute parser standing in for
 // `dateparser` until the i18n module lands. Handles "in Nh"/"in Nm"/"in Ns" and
 // "at HH:MM" / "HH:MM". The production path replaces this wholesale; the
@@ -210,18 +219,27 @@ func (StubDateTimeParser) Parse(_ context.Context, text string, now time.Time) (
 	// after the hour moves it into the afternoon: "в 7 вечера" is 19:00, and
 	// with SpellOutDigits in front of this that is what "в семь вечера" reads
 	// as too (Vikunja #469).
+	//
+	// "на" and "во" frame a spoken hour the same way, and until V-579 only "в"
+	// did: "в 9" set the reminder and "на 9" was not read at all.
 	for i := 0; i+1 < len(toks); i++ {
-		if toks[i] != "в" {
+		if !hourPrepositions[toks[i]] {
 			continue
 		}
 		t, ok := parseClock(toks[i+1], now)
 		if !ok {
 			continue
 		}
-		if i+2 < len(toks) {
-			t = applyRuQualifier(t, toks[i+2], now)
+		// The qualifier is looked for anywhere in the sentence, not only right
+		// after the hour. It arrives on its own turn when she asks which half of
+		// the day he meant, and "на 9" plus "вечера" is one time (V-579).
+		if qual := ruQualifierIn(toks); qual != "" {
+			t = applyRuQualifier(t, qual, now)
 		}
-		return t, true, nil
+		// A day word anywhere in the sentence moves the hour onto that day. This
+		// scan runs before the calendar one below, so without this "напомни
+		// завтра в 15:00" landed today and V-579 asks about exactly that gap.
+		return applyRuDayShift(t, toks, now), true, nil
 	}
 
 	// "через <N> <unit>" / "через <unit>" (bare = 1) / "через полчаса".
@@ -307,6 +325,10 @@ func sortDescByLen(ss []string) {
 // parseClock — "7", "7:30" → today at that time; if already past today, roll
 // to tomorrow (a "wake me 7" at 8pm fires tomorrow 7). Used by the stub scan.
 func parseClock(clock string, now time.Time) (time.Time, bool) {
+	// Speech arrives with its punctuation attached: "на 9." ends a sentence and
+	// still names nine o'clock (V-579). The colon is kept, since it is the one
+	// mark that is part of a clock.
+	clock = strings.Trim(clock, ".,!?;")
 	parts := strings.SplitN(clock, ":", 2)
 	h, err := strconv.Atoi(parts[0])
 	if err != nil || h < 0 || h > 23 {
@@ -480,6 +502,39 @@ func midnight(now time.Time, days int) time.Time {
 //
 // The date is recomputed rather than shifted, so an hour that parseClock
 // already pushed to tomorrow does not land two days out.
+// applyRuDayShift moves an hour onto the day the sentence names, if it names
+// one. The hour is kept exactly as read: the day word says which day and says
+// nothing about when in it.
+// ruQualifierIn returns the first part-of-day word in the sentence, or "".
+func ruQualifierIn(toks []string) string {
+	for _, tok := range toks {
+		switch cleanWord(tok) {
+		case "утра", "вечера", "дня", "ночи":
+			return cleanWord(tok)
+		}
+	}
+	return ""
+}
+
+func applyRuDayShift(t time.Time, toks []string, now time.Time) time.Time {
+	for _, tok := range toks {
+		days := 0
+		switch cleanWord(tok) {
+		case "сегодня":
+			days = 0
+		case "завтра":
+			days = 1
+		case "послезавтра":
+			days = 2
+		default:
+			continue
+		}
+		base := now.AddDate(0, 0, days)
+		return time.Date(base.Year(), base.Month(), base.Day(), t.Hour(), t.Minute(), 0, 0, now.Location())
+	}
+	return t
+}
+
 func applyRuQualifier(t time.Time, qualifier string, now time.Time) time.Time {
 	h := t.Hour()
 	switch strings.Trim(strings.ToLower(qualifier), ".,!?;:") {

internal/router/timementions.go

@@ -81,6 +81,148 @@ func NamesADay(text string) bool {
 	return false
 }
 
+// NamesAnHour reports whether the sentence names a time of day or an interval
+// away from now: a written clock, a numeral, a half or quarter past, or one of
+// the words an interval is built from. A day word alone is not one — "завтра"
+// says which day and says nothing about when in it.
+//
+// It is the gate on the reminder's time slot (V-577, V-579). A time slot that
+// names no hour is never filled, it is asked about. Both parsers answer a bare
+// day word with that day at the current minute, so "что у меня сегодня?" set a
+// reminder at 01:28 and "на завтра" set one at 01:38 — the minute he happened
+// to be speaking, in a request that never named one. The stub answers with
+// midnight instead, which is a different invented hour and no better.
+//
+// Same discipline as MentionsTime above: every signal is a closed lexicon class
+// or a digit, so this reads data and decides nothing about meaning.
+func NamesAnHour(text string) bool {
+	toks := strings.Fields(strings.ToLower(text))
+	for i, raw := range toks {
+		tok := cleanWord(raw)
+		if isDigitClock(tok) || isAllDigits(tok) {
+			return true
+		}
+		if _, ok := numeralDigit(tok); ok {
+			return true
+		}
+		if hourMarkers[tok] {
+			return true
+		}
+		if _, _, ok := halfPastAt(toks, i); ok {
+			return true
+		}
+		if _, _, _, ok := quarterToAt(toks, i); ok {
+			return true
+		}
+	}
+	return false
+}
+
+// NamesAnInterval reports whether the sentence measures the time from now
+// instead of naming it: "через час", "через 10 минут", "in 30 minutes".
+//
+// An interval resolves to one instant, so it answers the hour and the day
+// together and nothing about it is ambiguous. Callers that ask which day or
+// which nine o'clock have to skip it (V-579).
+func NamesAnInterval(text string) bool {
+	for _, raw := range strings.Fields(strings.ToLower(text)) {
+		switch cleanWord(raw) {
+		case "через", "спустя", "in":
+			return true
+		}
+	}
+	return false
+}
+
+// HourIsAmbiguous reports whether the hour named could be either half of the
+// day: "в 3" is three in the afternoon or three at night, and only he knows
+// which (V-579, owner's rule of 2026-08-06).
+//
+// Three things settle it and any one is enough. A qualifier - "вечера", "pm",
+// "полдень" - says which half. A written clock says it by being written. An
+// hour above twelve says it by arithmetic. An interval names no hour at all.
+func HourIsAmbiguous(text string) bool {
+	if NamesAnInterval(text) {
+		return false
+	}
+	toks := strings.Fields(strings.ToLower(text))
+	for _, raw := range toks {
+		tok := cleanWord(raw)
+		if hourQualifiers[tok] || isDigitClock(tok) {
+			return false
+		}
+	}
+	for _, raw := range toks {
+		tok := cleanWord(raw)
+		d, ok := numeralDigit(tok)
+		if !ok && isAllDigits(tok) {
+			d, ok = tok, true
+		}
+		if !ok {
+			continue
+		}
+		n, err := strconv.Atoi(d)
+		if err == nil && n >= 1 && n <= 12 {
+			return true
+		}
+	}
+	return false
+}
+
+// hourQualifiers — the words that pin an hour to one half of the day. Closed,
+// and every member is a lexicon class or the two English markers.
+var hourQualifiers = buildHourQualifiers()
+
+func buildHourQualifiers() map[string]bool {
+	m := map[string]bool{
+		"утра": true, "вечера": true, "дня": true, "ночи": true,
+		"полдень": true, "полночь": true, "полудня": true,
+		"am": true, "pm": true, "noon": true, "midnight": true,
+	}
+	for _, w := range lexicon.PartsOfDay() {
+		m[w] = true
+	}
+	return m
+}
+
+func isAllDigits(tok string) bool {
+	if tok == "" {
+		return false
+	}
+	for _, r := range tok {
+		if r < '0' || r > '9' {
+			return false
+		}
+	}
+	return true
+}
+
+// hourMarkers — timeMarkers minus the day words and the weekdays, which name a
+// day and not an hour, and minus "сейчас", which IS the clock and so can never
+// be the evidence that the clock was meant.
+var hourMarkers = buildHourMarkers()
+
+func buildHourMarkers() map[string]bool {
+	m := map[string]bool{
+		"утра": true, "вечера": true, "дня": true, "ночи": true,
+		"часа": true, "часов": true, "час": true, "часу": true,
+		"минут": true, "минуты": true, "минуту": true,
+		"через": true, "спустя": true, "полчаса": true,
+		"полдень": true, "полночь": true,
+		"am": true, "pm": true, "noon": true, "midnight": true, "in": true,
+	}
+	for _, w := range lexicon.PartsOfDay() {
+		m[w] = true
+	}
+	for _, w := range lexicon.HalfHourWords() {
+		m[w] = true
+	}
+	for w := range minutesTo {
+		m[w] = true
+	}
+	return m
+}
+
 // isMonth reports whether the token is a month name. The lexicon holds the
 // genitive, which is the form a spoken date uses: "10 июля".
 func isMonth(tok string) bool {

internal/router/timementions_test.go

@@ -1,6 +1,10 @@
 package router
 
-import "testing"
+import (
+	"context"
+	"testing"
+	"time"
+)
 
 func TestMentionsTime(t *testing.T) {
 	for _, s := range []string{
@@ -21,6 +25,87 @@ func TestMentionsTime(t *testing.T) {
 	}
 }
 
+// TestNamesAnHour — the gate on the reminder's time slot (V-577, V-579). A day
+// word is not an hour, and a sentence that names no hour is asked about rather
+// than completed from the clock.
+func TestNamesAnHour(t *testing.T) {
+	for _, s := range []string{
+		"в 11:00", "на 9", "в 9", "в девять", "в 9 утра", "завтра в 9",
+		"через час", "через двадцать минут", "в половине восьмого",
+		"без четверти восемь", "remind me at noon", "вечером",
+	} {
+		if !NamesAnHour(s) {
+			t.Errorf("NamesAnHour(%q) = false; this names an hour or an interval", s)
+		}
+	}
+	for _, s := range []string{
+		"на завтра", "что у меня сегодня?", "напомни завтра позвонить маме",
+		"в пятницу", "позвонить маме", "",
+	} {
+		if NamesAnHour(s) {
+			t.Errorf("NamesAnHour(%q) = true; no hour was spoken, so she has to ask", s)
+		}
+	}
+}
+
+// TestHourIsAmbiguous — the owner's rule of 2026-08-06. A bare hour is either
+// half of the day and gets asked about; a qualifier, a written clock, an hour
+// above twelve or an interval settles it and goes straight through.
+func TestHourIsAmbiguous(t *testing.T) {
+	for _, s := range []string{
+		"напомни завтра в 3 заказать цветы", "в 9", "на 9", "в девять", "в 11 позвонить маме",
+	} {
+		if !HourIsAmbiguous(s) {
+			t.Errorf("HourIsAmbiguous(%q) = false; the hour could be either half of the day", s)
+		}
+	}
+	for _, s := range []string{
+		"напомни в 9 вечера разгрузить стиралку", "завтра в 15:00", "в 21", "в 11:00",
+		"через час", "через 10 минут", "remind me at noon", "напомни позвонить маме",
+	} {
+		if HourIsAmbiguous(s) {
+			t.Errorf("HourIsAmbiguous(%q) = true; this time reads only one way", s)
+		}
+	}
+}
+
+// TestNamesAnInterval — an interval resolves to one instant, so it answers the
+// hour and the day at once and is never asked about.
+func TestNamesAnInterval(t *testing.T) {
+	for _, s := range []string{"через час", "через 10 минут", "через полчаса", "in 30 minutes"} {
+		if !NamesAnInterval(s) {
+			t.Errorf("NamesAnInterval(%q) = false", s)
+		}
+	}
+	for _, s := range []string{"завтра в 15:00", "в 9 вечера", ""} {
+		if NamesAnInterval(s) {
+			t.Errorf("NamesAnInterval(%q) = true", s)
+		}
+	}
+}
+
+// TestReminderSlotRefusesAnHourNobodySaid — the same rule where it bites. The
+// parser answers a bare day word with that day at the current minute, and the
+// slot must stay empty so the daemon asks.
+func TestReminderSlotRefusesAnHourNobodySaid(t *testing.T) {
+	now := time.Date(2026, 8, 6, 1, 38, 0, 0, time.UTC)
+	ex := Extractor{Time: clockEchoParser{}}
+	if got := ex.Extract(context.Background(), IntentReminder, "на завтра", now); got.HasTime {
+		t.Errorf("«на завтра» filled the time slot with %s, which is the clock", got.Time.Format("15:04"))
+	}
+	if got := ex.Extract(context.Background(), IntentReminder, "на 9", now); !got.HasTime {
+		t.Error("«на 9» names an hour and must still fill the slot")
+	}
+}
+
+// clockEchoParser stands in for what both real parsers do with a bare day word:
+// it answers with the current time of day.
+type clockEchoParser struct{}
+
+func (clockEchoParser) Parse(_ context.Context, _ string, now time.Time) (time.Time, bool, error) {
+	return now.AddDate(0, 0, 1), true, nil
+}
+
 // A sentence with no time in it must not read as one, or a real follow-up stops
 // inheriting the hour it meant.
 func TestMentionsTimeIgnoresSentencesWithoutOne(t *testing.T) {