🐛 Fixed Analytics > Growth MRR chart starting at zero at beginning of time range (#25694)

ref
https://linear.app/ghost/issue/NY-328/investigate-mrr-chart-showing-zero-for-blueshirt-banter

## Problem

In some cases, the MRR chart in Analytics > Growth will incorrectly
start at $0 for the very first data point.
<img width="1428" height="496" alt="Screenshot 2025-12-10 at 21 44
47@2x"
src="https://github.com/user-attachments/assets/f53a6abc-6f51-4abe-872f-694ca1efa7c7"
/>


## Cause

The `/stats/mrr` endpoint returns a sparse dataset, only including dates
in the response that had changes in MRR, so not every data point in the
chart is returned by the API. The frontend logic for calculating the
first data point was not accounting for this, and defaulting to $0.

## Fix

The fix is to check for this condition where there are missing data
points between the `dateFrom` parameter passed to the API (the first day
of the selected date range) and the first data point returned by the
API, and to fill in the earliest MRR value for this range.

Author: cmraible

apps/stats/src/hooks/use-growth-stats.ts

@@ -296,6 +296,14 @@ export const useGrowthStats = (range: number) => {
                         ...mostRecentBeforeRange,
                         date: dateFromMoment.format('YYYY-MM-DD')
                     });
+                } else if (result.length > 0) {
+                    // No data before range, use the earliest data point in the range
+                    // to fill in the start date (representing MRR at range start)
+                    const earliestInRange = [...result].sort((a, b) => new Date(a.date).getTime() - new Date(b.date).getTime())[0];
+                    result.unshift({
+                        ...earliestInRange,
+                        date: dateFromMoment.format('YYYY-MM-DD')
+                    });
                 }
             }
 

apps/stats/test/unit/hooks/use-growth-stats.test.tsx

@@ -279,6 +279,48 @@ describe('useGrowthStats', () => {
             expect(result.current.mrrData.length).toBeGreaterThan(1);
         });
 
+        it('uses earliest data point when no MRR data exists before dateFrom', async () => {
+            // Simulate the bug: API returns MRR data starting AFTER dateFrom
+            // For a 90-day range, dateFrom would be ~90 days ago
+            // But the MRR data only starts 15 days into that range
+            const startDate = moment().subtract(89, 'days');
+            const dateFrom = startDate.format('YYYY-MM-DD');
+
+            // MRR data starts 15 days AFTER dateFrom (no data before range)
+            const firstMrrDate = moment(startDate).add(15, 'days').format('YYYY-MM-DD');
+            const secondMrrDate = moment(startDate).add(16, 'days').format('YYYY-MM-DD');
+
+            const lateMrrData = [
+                {date: firstMrrDate, mrr: 17286, currency: 'usd'},
+                {date: secondMrrDate, mrr: 17286, currency: 'usd'}
+            ];
+
+            // Update getRangeDates mock to return predictable dates
+            mockedGetRangeDates.mockImplementation(() => ({
+                startDate,
+                endDate: moment()
+            }));
+
+            mockSuccess(mockedUseMrrHistory, {
+                stats: lateMrrData,
+                meta: {
+                    totals: [{mrr: 17286, currency: 'usd'}]
+                }
+            });
+
+            const {result} = renderHook(() => useGrowthStats(90));
+
+            await waitFor(() => {
+                expect(result.current.isLoading).toBe(false);
+            });
+
+            // The first data point should be at dateFrom (synthetic start point)
+            expect(result.current.mrrData[0].date).toBe(dateFrom);
+
+            // The MRR value should be the earliest available value (17286), NOT 0
+            expect(result.current.mrrData[0].mrr).toBe(17286);
+        });
+
         it('handles range=1 correctly', async () => {
             const {result} = renderHook(() => useGrowthStats(1));