Merge pull request 'Bug: pattern.Detect has no minimum-interval floor, so four fast taps mint a permanent false routine' (#121) from task/468-bug-pattern-detect-has-no-minimum-interv into master

internal/pattern/detector.go

@@ -53,9 +53,31 @@ const MinOnPatternFraction = 0.7
 // a repeat. False negatives cost one more observation and nothing else.
 const MinEvents = 4
 
+// MinIntervalDays — the fastest rhythm that may be called a routine. Two
+// hours.
+//
+// Without a floor, four taps of the same key minutes apart give intervals near
+// 0.002 days. They all sit inside the ±50% band by construction, so the
+// detector proposed a routine and PhraseRoutine worded it as "каждый день"
+// (Vikunja #468). The damage outlives the mistake: UNIQUE(action, object)
+// means dismissing the bogus proposal burns that pair permanently, so the real
+// routine behind it can never be proposed again.
+//
+// Two hours rather than a day, because a genuine habit can run several times a
+// day — meals, water, a break. Anything faster than that is not a habit she
+// should be proposing to remind him about; the loop rules already cover that
+// range, and they are rules, not guesses. It is checked against the median, so
+// one quick repeat inside a real rhythm still counts.
+//
+// The other half of this is that hand-QA of the detector was unsafe: seeding a
+// pattern the obvious way, four chat turns in a row, poisoned the very pair
+// being tested.
+const MinIntervalDays = 2.0 / 24.0
+
 // Detect checks whether a sequence of events for the same action+object
 // forms a stable recurring pattern. Returns a ProposedRoutine when:
 //   - At least MinEvents events exist (≥3 intervals)
+//   - The median interval is at least MinIntervalDays
 //   - At least MinOnPatternFraction of the intervals sit within
 //     MaxIntervalRatio of the median interval
 //
@@ -88,8 +110,8 @@ func Detect(events []Event) (*ProposedRoutine, error) {
 	}
 
 	center := medianFloat(intervals)
-	if center <= 0 {
-		return nil, nil
+	if center <= 0 || center < MinIntervalDays {
+		return nil, nil // a burst, not a rhythm — see MinIntervalDays
 	}
 
 	// Keep the intervals that sit inside the band around the median. The

internal/pattern/detector_test.go

@@ -216,3 +216,46 @@ func TestDetectMedianBandNotExtremes(t *testing.T) {
 		})
 	}
 }
+
+// A burst is not a habit. Four taps of the same key minutes apart give
+// intervals near 0.002 days, all inside the ±50% band by construction, so the
+// detector called it a daily routine (Vikunja #468). Dismissing that proposal
+// burns the action+object pair permanently, which also made hand-QA of the
+// detector unsafe.
+func TestDetectRejectsABurst(t *testing.T) {
+	base := time.Date(2026, 8, 4, 9, 0, 0, 0, time.UTC)
+	var events []Event
+	for i := 0; i < 4; i++ {
+		events = append(events, Event{
+			Action: "refill", Object: "cat_water",
+			Ts: base.Add(time.Duration(i) * 7 * time.Minute),
+		})
+	}
+	r, err := Detect(events)
+	if err != nil {
+		t.Fatalf("Detect: %v", err)
+	}
+	if r != nil {
+		t.Fatalf("four taps minutes apart proposed a routine every %.3f days", r.IntervalDays)
+	}
+}
+
+// The floor is two hours, not a day: a habit that runs several times a day is
+// still a habit.
+func TestDetectKeepsASeveralTimesADayHabit(t *testing.T) {
+	base := time.Date(2026, 8, 4, 8, 0, 0, 0, time.UTC)
+	var events []Event
+	for i := 0; i < 5; i++ {
+		events = append(events, Event{
+			Action: "drink", Object: "water",
+			Ts: base.Add(time.Duration(i) * 4 * time.Hour),
+		})
+	}
+	r, err := Detect(events)
+	if err != nil {
+		t.Fatalf("Detect: %v", err)
+	}
+	if r == nil {
+		t.Fatal("a four-hour rhythm over five events is a habit, got nil")
+	}
+}