Incorrect reponse of Fitfit Intraday Heart Rate API endpoint

[pvannierop]

This issue has been reported upstream here.

Problem statement

The Intraday Heart Rate By Interval request returns data points that are outside of the requested time window appended to the end of the observation list. Since FB connector considers the last received observation to be the latest to derive the current offset, the offset never advances and newer data is not downloaded.

How to reproduce

Download Intraday Heart Rate data per second between times 00:00:57 and 23:59:59.9999999 with the following URL:

https://api.fitbit.com/1/user/CHRXHJ/activities/heart/date/2026-02-13/2026-02-13/1sec/time/00:00:57/23:59:59.json?timezone=UTC

Expected result

JSON with response body JSON that has observations in order from time 00:00:57 to 23:59:56 (time of last observation for the requested day).

Observed result

Note: actual heart rates were replaced by 00.

Response body: 
{ 
"activities-heart": [ ... ], 
 "activities-heart-intraday": {
   "dataset": [ 
      { "time": "00:01:04", "value": 00 },
      ... ... 
      { "time": "23:59:56", "value": 00 },
      { "time": "00:00:01", "value": 00 },
      { "time": "00:00:06", "value": 00 },
      { "time": "00:00:16", "value": 00 },
      { "time": "00:00:31", "value": 00 },
      { "time": "00:00:46", "value": 00 },
      { "time": "00:00:56", "value": 00 } 
  ], 
  "datasetInterval": 1, 
  "datasetType": "second"
}}

Notice the appended 00:00:01 to 00:00:56 observation times at the end.