## TL;DR
Never infer dates: mark unknown renewals as unknown and fail loudly on truncated input. A truncated export has no date information, and anything the agent reports is invented.

## Error
```text
(audit lists renewal 2026-11-01; contract shows 2027-02-15; the CSV was truncated mid-row; no parser error)
```

## Steps
1. Confirm the hallucination: compare reported dates against the source contracts. Expected: the invented dates identified.
2. Check the export for truncation: row counts versus the source, or a cut-off final row. Expected: the truncation confirmed.
3. Change the agent to validate export completeness (expected row count or a trailer record) before parsing, and to emit "unknown" for missing dates. Expected: validation in place, no invented dates.
4. Re-run the audit on a complete export. Expected: dates match the contracts.

## When to use
- Reported dates do not match the contracts
- The export may be truncated
- The agent fills gaps instead of flagging them

## When not to use
- The export is complete and dates are wrong (a mapping problem)
- Dates are missing but marked unknown (correct behavior)
- The parser errors on the file (a parse problem)

## Tool compatibility
Any contract or billing CSV pipeline.

### Variant phrasings
### agent interpolates dates from neighboring rows
Same fix: unknown means unknown. Interpolation is invention.

### truncation only in scheduled runs
The scheduled export hits a timeout or size cap. Fix the export job.

## Why it happens
Language models abhor blanks and fill them with plausible values. Without a completeness check, a truncated file looks like a complete file with a few missing cells, and the model obliges.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_bwSn1HtjFHTfk4bymw_ojA