router: a reminder with no subject asks instead of guessing (V-383)

Slots.Text was the raw utterance for every intent, so a reminder could not
have an empty subject. StillMissing never reported SlotText, the question
"О чём напомнить?" was unaskable, and the branch in PendingQuestion.Answer
that fills a text slot could only overwrite the whole request.

The LLM path now keeps the model's own text, empty included, and the gate
turns a subjectless reminder into a question. The classifier path is
unchanged: it has no subject parser, so the utterance is the only signal it
has.

internal/router/llmrouter.go

@@ -210,7 +210,11 @@ func (lr *LLMRouter) Route(ctx context.Context, utterance string, now time.Time)
 		d.Slots.HasKey = a.Key != ""
 	case IntentReminder:
 		d.Intent = IntentReminder
-		d.Slots.Text = firstNonEmpty(a.Text, utterance)
+		// No utterance fallback here, unlike every other intent below. The
+		// model returning no text for a reminder means it found no subject,
+		// and "напомни в 11" is not a subject. Leaving Text empty is what
+		// lets the gate turn that into a question (Vikunja #383).
+		d.Slots.Text = a.Text
 	case IntentNote:
 		d.Intent = IntentNote
 		d.Slots.Text = firstNonEmpty(a.Text, utterance)

internal/router/llmrouter_test.go

@@ -356,3 +356,35 @@ func TestRouterLLMFactWithResolvedKeyStaysConfident(t *testing.T) {
 		t.Fatalf("a fact the parser could key must not clarify: %+v", d)
 	}
 }
+
+// A reminder with a time and no subject must come back empty and gated, not
+// backfilled with the raw words. "напомни в 11" carries an hour and nothing to
+// say at that hour; parking the utterance in Text made the request look
+// complete, so the daemon set a reminder that fires saying "напомни в 11"
+// (Vikunja #383).
+func TestLLMReminderWithoutSubjectAsksInsteadOfGuessing(t *testing.T) {
+	r := newLLMTestRouter(t, `{"intent":"reminder"}`)
+	d, err := r.Route(context.Background(), "напомни в 11", refNow())
+	if err != nil {
+		t.Fatalf("route: %v", err)
+	}
+	if d.Slots.Text != "" {
+		t.Fatalf("subject backfilled from the utterance: %q", d.Slots.Text)
+	}
+	if !d.Clarify {
+		t.Fatalf("a subjectless reminder was accepted, confidence %v", d.Confidence)
+	}
+}
+
+// The gate is about the subject, not about reminders in general: one that has
+// both halves still runs without a question.
+func TestLLMReminderWithSubjectIsNotGated(t *testing.T) {
+	r := newLLMTestRouter(t, `{"intent":"reminder","text":"позвонить маме"}`)
+	d, err := r.Route(context.Background(), "напомни в 11 позвонить маме", refNow())
+	if err != nil {
+		t.Fatalf("route: %v", err)
+	}
+	if d.Clarify {
+		t.Fatalf("a complete reminder was sent back as a question: %+v", d.Slots)
+	}
+}

internal/router/router.go

@@ -147,7 +147,15 @@ func (r *Router) fillSlots(ctx context.Context, d *Decision, now time.Time) {
 			d.Slots.Fn, d.Slots.Args, d.Slots.HasFn = fn, args, true
 		}
 	}
-	if d.Slots.Text == "" {
+	// The extractor's Text is the raw utterance, which is the payload for a
+	// note, a query or a chat turn but not for a reminder — there Text is the
+	// subject, what she says at the hour. Backfilling it made Text impossible
+	// to be empty, so StillMissing never reported SlotText and "О чём
+	// напомнить?" was unaskable; the answer to a question she did manage to
+	// ask then overwrote the whole request instead of filling one gap
+	// (Vikunja #383). A reminder with no subject stays empty and is gated
+	// below into a question.
+	if d.Slots.Text == "" && d.Intent != IntentReminder {
 		d.Slots.Text = ex.Text
 	}
 	// Stage stays 1: it says who decided the route, and that was the LLM.
@@ -177,6 +185,12 @@ func (r *Router) gateLLMDecision(d *Decision) {
 	if d.Intent == IntentAct && !d.Slots.HasFn && d.Confidence > llmThinConfidence {
 		d.Confidence = llmThinConfidence
 	}
+	// A reminder with no subject: she knows when but not what to say then.
+	// Setting it anyway fires an empty reminder at the hour, which reads as a
+	// bug to him and cannot be repaired after the fact. Ask (Vikunja #383).
+	if d.Intent == IntentReminder && d.Slots.Text == "" && d.Confidence > llmThinConfidence {
+		d.Confidence = llmThinConfidence
+	}
 	if d.Confidence < r.threshold {
 		d.Clarify = true
 	}