## TL;DR
Poll the backfill status with growing intervals and stop hammering the status endpoint, resuming from the last known job state, because the monitor itself exhausted the API rate limit by polling a long backfill too aggressively and then could not read the status it needed. Start with the Chronon backfill monitor polling interval and the job status endpoint responses, work on one affected call, record, or run first, and prove the fix there before running the full set. Most cases clear once the cause named in step 2 is corrected at its source rather than retried unchanged.

```text
Chronon API rate limit hit mid-backfill monitor error agent failed to poll status
```

## Use this when
- You see this exact message or symptom: Chronon API rate limit hit mid-backfill monitor error agent failed to poll status
- One run, record, call, or object is affected and you can name it
- A retry without changing anything reproduces the same result

## Not for this skill when
- The system fails with a different message and none of the signals here appear
- Nothing has failed yet and you are doing first time setup or general planning
- Every service from this vendor is down for all users, which is a vendor outage to wait out first

## Steps
1. Reproduce the failure once using the Chronon backfill monitor polling interval and the job status endpoint responses, and record the time, the workspace or account, and the one item it names. Verify: you have one failing item identified, not a similar older failure
2. Inspect the polling interval in the monitor, the number of status calls made, and the job id whose status is being tracked. Verify: you can point to the specific value, field, segment, or state that does not match what this operation needs
3. Apply the fix at that source: Poll the backfill status with growing intervals and stop hammering the status endpoint, resuming from the last known job state, because the monitor itself exhausted the API rate limit by polling a long backfill too aggressively and then could not read the status it needed. Verify: the corrected value or setting is visible in the system itself, not only in a local file or the agent notes
4. Re-run the original operation on the single affected item first. Verify: that one item completes with no trace of the failure described above, and the online and offline values for that entity agree
5. Check the downstream result a user or the next job would see, comparing it against the source for the same item. Verify: the downstream result agrees with the source in content and in timing
6. Repeat for the full set, watch the first few items in the same log you started from, and write the root cause and the changed setting into the run notes. Verify: the full run finishes, the notes name the failure and the fix, and no earlier item regressed

## Variant phrasings
### Chronon API rate limit hit mid-backfill monitor error agent failed to poll status
The subject-first phrasing of the same failure. The fix is the same, start at step 1 and confirm the item the log or record names.
### Tool-first phrasing of this failure
The phrasing searchers use once they know which system raised it. It is the same underlying problem, not a separate bug.
### Why does this keep happening after a retry
The repeat-occurrence phrasing. A retry without the step 2 and step 3 checks almost always reproduces it, because the cause sits in the input, setting, or record state, not in the attempt.

Compatibility: Chronon API, agent monitors for long running backfills.

## Why it happens
Status endpoints count against the same limits as work endpoints. A monitor that polls every few seconds for an hour long job becomes the load that locks it out.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_N9kc0pQf_sx9XCtOTJzIiw