## TL;DR
Align the two reports before comparing them: the agent failed to compare Evidently drift reports across dates after a parse error, so extract both reports through the same parser version, normalise metric names, and only then diff the drift results. Cross-date comparison fails when the two reports were produced or parsed differently. A report format change between the dates is the usual hidden difference.

```text
agent failed to compare evidently drift reports across two dates after report parse error
```

## Use this when
- The check or run fails with this symptom: an agent fails to compare Evidently drift reports across two dates after a report parse error.
- You are working on an agent workflow tracking Evidently drift over time for a model or a table and the failure repeats on the same data or configuration.
- You need the failing rows, rule, or stage isolated before changing thresholds or code.

## Not for this skill when
- Reports from the same day and version that still fail to parse, which points at a damaged report file.
- The error text names a different tool, stage, or root cause. Match the verbatim error first and use that skill.

## Steps
1. Record the Evidently version that produced each report. Verify: the versions match, or the difference is named
2. Parse both reports with one extractor and export both to the same flat metric table. Verify: both dates produce rows in the identical shape
3. Normalise metric and column names across the two exports. Verify: the same drift metric has one name on both dates
4. Diff the flat tables by column and metric. Verify: drift changes between the dates are listed
5. Save the flat export with each report. Verify: the next comparison starts from parsed data, not from the reports

## Variant phrasings
### agent failed compare evidently drift reports two dates parse
The shorter phrasing focused on the named failure.
### evidently drift report comparison parse error
The symptom phrasing a searcher tries next.
### compare drift reports across dates fix
The variant naming the failing stage or tool directly.

Compatibility: Evidently report versions and JSON exports, agent comparison workflows

## Why it happens
Evidently report internals evolve between versions, so a parser fitted to the newer report fails or misreads the older one. Comparison code that assumes one format across a version boundary breaks even though both reports are individually valid.

## Edge cases / pitfalls
- Store the parsed metrics at report time; future format changes then never reach historical comparisons.
- A missing column in one date is a finding about the feature set, not a parse failure; keep absent and unparsable distinct in the output.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_q_UHIdT80Sf9RQc34GUWNA