fix(claude_code): resume incremental collection from the last collected day

backend/plugins/claude_code/tasks/collector_utils.go

@@ -82,12 +82,14 @@ func utcDate(t time.Time) time.Time {
 // computeUsageDateRange returns the [start, until] date range for incremental collection.
 // The Anthropic Analytics API only serves data from 2026-01-01 onwards and requires
 // dates to be at least three days old, so the current day and previous two days are skipped.
+// since is the start time of the last successful run, so collection resumes from the last
+// day that run collected.
 func computeUsageDateRange(now time.Time, since *time.Time) (start, until time.Time) {
 	apiFloor := time.Date(2026, 1, 1, 0, 0, 0, 0, time.UTC)
 	until = utcDate(now).AddDate(0, 0, -claudeCodeAvailabilityLagDays)
 	start = until.AddDate(0, 0, -(claudeCodeInitialBackfillDays - 1))
 	if since != nil {
-		start = utcDate(*since).AddDate(0, 0, 1)
+		start = utcDate(*since).AddDate(0, 0, -claudeCodeAvailabilityLagDays)
 		minStart := until.AddDate(0, 0, -(claudeCodeInitialBackfillDays - 1))
 		if start.Before(minStart) {
 			start = minStart
@@ -96,6 +98,9 @@ func computeUsageDateRange(now time.Time, since *time.Time) (start, until time.T
 	if start.Before(apiFloor) {
 		start = apiFloor
 	}
+	if start.After(until) {
+		start = until
+	}
 	return start, until
 }
 

backend/plugins/claude_code/tasks/collector_utils_test.go

@@ -42,14 +42,57 @@ func TestComputeUsageDateRangeHonorsApiFloor(t *testing.T) {
 	assert.Equal(t, time.Date(2026, 3, 16, 0, 0, 0, 0, time.UTC), until)
 }
 
-func TestComputeUsageDateRangeProducesEmptyWindowInsideLag(t *testing.T) {
+func TestComputeUsageDateRangeResumesFromLastCollectedDay(t *testing.T) {
 	now := time.Date(2026, 6, 19, 14, 30, 0, 0, time.UTC)
 	since := time.Date(2026, 6, 16, 12, 0, 0, 0, time.UTC)
 
 	start, until := computeUsageDateRange(now, &since)
 
-	assert.Equal(t, time.Date(2026, 6, 17, 0, 0, 0, 0, time.UTC), start)
+	assert.Equal(t, time.Date(2026, 6, 13, 0, 0, 0, 0, time.UTC), start)
 	assert.Equal(t, time.Date(2026, 6, 16, 0, 0, 0, 0, time.UTC), until)
-	assert.False(t, newClaudeCodeDayIterator(start, until).HasNext())
-	assert.False(t, newClaudeCodeDateRangeIterator(start, until, claudeCodeSummaryMaxDays).HasNext())
+}
+
+func TestComputeUsageDateRangeCollectsWhenSinceIsNow(t *testing.T) {
+	now := time.Date(2026, 9, 10, 12, 31, 0, 0, time.UTC)
+
+	start, until := computeUsageDateRange(now, &now)
+
+	assert.Equal(t, time.Date(2026, 9, 7, 0, 0, 0, 0, time.UTC), start)
+	assert.Equal(t, time.Date(2026, 9, 7, 0, 0, 0, 0, time.UTC), until)
+	assert.True(t, newClaudeCodeDayIterator(start, until).HasNext())
+	assert.True(t, newClaudeCodeDateRangeIterator(start, until, claudeCodeSummaryMaxDays).HasNext())
+}
+
+func TestComputeUsageDateRangeCapsBackfillHorizon(t *testing.T) {
+	now := time.Date(2026, 9, 10, 12, 31, 0, 0, time.UTC)
+	since := time.Date(2026, 2, 1, 0, 0, 0, 0, time.UTC)
+
+	start, until := computeUsageDateRange(now, &since)
+
+	assert.Equal(t, time.Date(2026, 6, 10, 0, 0, 0, 0, time.UTC), start)
+	assert.Equal(t, time.Date(2026, 9, 7, 0, 0, 0, 0, time.UTC), until)
+}
+
+func TestComputeUsageDateRangeCollectsEveryDayAcrossRuns(t *testing.T) {
+	first := time.Date(2026, 8, 6, 7, 0, 0, 0, time.UTC)
+	for _, interval := range []int{1, 2, 3, 7} {
+		collected := map[time.Time]bool{}
+		var since *time.Time
+		var now time.Time
+		for run := 0; run < 6; run++ {
+			now = first.AddDate(0, 0, run*interval)
+			start, until := computeUsageDateRange(now, since)
+			for d := start; !d.After(until); d = d.AddDate(0, 0, 1) {
+				collected[d] = true
+			}
+			runStart := now
+			since = &runStart
+		}
+
+		start, _ := computeUsageDateRange(first, nil)
+		_, until := computeUsageDateRange(now, nil)
+		for d := start; !d.After(until); d = d.AddDate(0, 0, 1) {
+			assert.Truef(t, collected[d], "interval %d: %s not collected", interval, d.Format(claudeCodeDateLayout))
+		}
+	}
 }