## TL;DR
An unsigned message has no DKIM result, and any system reporting pass for it is inventing evidence, usually because a language model filled a plausible verdict where a check should have run. Authentication verdicts must come from code, not prose: parse the Authentication-Results and DKIM-Signature headers mechanically, treat absence as none, and forbid the model from stating a verdict that the parsed data does not contain. Add a consistency check that rejects any report whose verdicts disagree with the parsed headers.

```text
the triage agent hallucinated a dkim pass verdict on an unsigned message; the verification step failed
```

## Use this when
- An agent report says dkim=pass for a message with no DKIM-Signature header.
- Verdict fields in reports do not match the raw headers on audit.

## Not for this skill when
- The header exists and the dispute is over alignment. That is an alignment analysis task.
- A gateway strips signatures after verification and stamps results. Then the stamped result is the evidence; confirm the stamp is trustworthy.

## Steps
1. Audit a sample of agent verdicts against mechanical header parsing and count mismatches. Verify: the hallucination rate is measured.
2. Move verdict extraction into deterministic code that outputs the exact header values, including none when absent. Verify: unsigned test mail yields a none verdict.
3. Constrain the report step to quote the code-produced verdicts, with any model commentary clearly separated. Verify: the report template has no free-text verdict field.
4. Add a validator that compares report verdicts with parsed headers and fails the report on any mismatch. Verify: a planted wrong verdict is caught in testing.
5. Re-run the audited sample set. Verify: zero verdict mismatches between reports and headers.

## Variant phrasings
### agent invented dkim pass unsigned message verification
The invented verdict variant.
### authentication verdicts from headers not llm triage
The deterministic verdict variant.

Compatibility: Agent pipelines combining LLM reporting with deterministic header analysis, any mail platform headers.

## Why it happens
Language models complete patterns, and dkim=pass is a very common pattern next to well-behaved mail. Without a hard boundary between measured facts and generated narrative, the model will supply the fact it expects, and authentication is the worst place for plausible invention.

## Edge cases / pitfalls
- The same risk applies to SPF, DMARC and sandbox verdicts. Mechanise all of them.
- Absence of a header is data. Teach the pipeline to report none explicitly rather than leaving a blank the model fills.
- Spot-audit verdicts forever, at a low rate. This class of error returns silently.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_Qsbe4YRTkEjVq1SueYn10g