## TL;DR

The agent downloads the Concur export on every run without checking whether it changed, so it reprocesses identical data in a loop. Store the export's etag (or checksum) from the last run and send it as If-None-Match; when Concur returns 304 Not Modified, skip the download and the reprocessing. The etag is the change signal; ignoring it is the bug.

## Error

```text
agent looped re-downloading the same concur export  -  etag ignored
```

## Steps

1. Confirm the loop: the agent log shows repeated full downloads with identical content. Expected: the downloads are byte-identical across runs.
2. Check whether the export endpoint returns an etag or last-modified header. Expected: the headers are available on the response.
3. Store the etag after each successful download and send it as If-None-Match on the next run. Expected: unchanged exports return 304.
4. On 304, skip the download and mark the data as current; on 200, process and store the new etag. Expected: the agent only processes changed exports.
5. Add a loop guard: alert if the agent processes the same checksum twice in a row. Expected: future ignore-the-etag regressions are caught.

## When to use

- An agent re-downloads the same Concur export every run.
- Audit runs reprocess identical data.
- The export endpoint supports etags or last-modified headers.

## When not to use

- The export genuinely changes between runs (the downloads are correct).
- The endpoint offers no change-detection headers (poll on a schedule instead).
- The loop is in a different stage of the pipeline.

## Tool compatibility

Applies to custom audit agents fetching Concur exports (Concur APIs, Python or Node agents; current 2026 releases).

### Variant phrasings

### agent reprocesses the same export daily

Honor the etag and skip unchanged downloads.

### concur export downloaded but never changes

The 304 path is missing. Add conditional requests.

### infinite re-download loop in the audit agent

Store the checksum and break the loop on identical content.

## Why it happens

Polling loops are the default agent pattern: fetch, process, repeat. Without conditional requests, every poll is a full download, and if the downstream processing has no idempotency, the same data gets re-audited forever. Etags exist to make polling cheap and correct; the agent just has to use them. The checksum guard is belt-and-suspenders for endpoints with weak header support.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_l1D4VzVF3R37wFfyLGRFcg