exactly one candidate-keyed health assertion is required

Error message

exactly one candidate-keyed health assertion is required

What it means

from_evidence requires the health map of RecordedEvidence to contain exactly one candidate-keyed health assertion. This error is thrown when the evidence has zero health entries (missing assertion) or more than one (multiple candidates asserted healthy). The recorded evaluator supports only a single promoted candidate's health result.

Solutions

Ensure evidence.health contains exactly one entry: the candidate id that will be promoted.
Remove extra health entries for non-promoted candidates before calling from_evidence.
Run the health check during evidence recording and record its single boolean result.
Validate the evidence struct (health.len() == 1) before passing it to from_evidence.

Example fix

// before
evidence.health.insert(candidate_a.clone(), true);
evidence.health.insert(candidate_b.clone(), false); // two entries -> bails
let eval = RecordedEvaluator::from_evidence(evidence)?;

// after
evidence.health.clear();
evidence.health.insert(promoted_candidate_id.clone(), true);
assert_eq!(evidence.health.len(), 1);
let eval = RecordedEvaluator::from_evidence(evidence)?;

Defensive patterns

Strategy: validation

Validate before calling

if evidence.health.len() != 1 {
    return Err("exactly one candidate-keyed health assertion is required");
}

Prevention

Record health only for the single promoted candidate.
Never merge health maps from multiple evidence runs.
Assert health.len() == 1 as an invariant when constructing RecordedEvidence.

When it happens

Trigger: Calling RecordedEvaluator::from_evidence with evidence.health being an empty map, or with health entries for two or more distinct candidate ids.

Common situations: Recording evidence without running any health check; merging evidence from multiple candidates into one RecordedEvidence; building the evidence struct by hand and populating health for every candidate instead of only the promoted one.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of affaan-m/ECC@8321021c54 (2026-09-16). Data as JSON: /api/errors/81d0399a4f93bc13. Report an issue: GitHub.

Appendix: source

Thrown at ecc2/src/harness_eval.rs:383

        Self {
            name: "recorded-v1".into(),
            scores,
            health_ok,
            health_candidate: None,
            calls: Vec::new(),
        }
    }

    pub fn from_evidence(evidence: RecordedEvidence) -> Result<Self> {
        if evidence.evaluator != "recorded-v1" {
            bail!("CLI evidence evaluator must be recorded-v1");
        }
        let score_count = evidence.scores.values().map(BTreeMap::len).sum::<usize>();
        if score_count > 20_000 || evidence.scores.keys().any(|id| id.len() != 64) {
            bail!("recorded evidence exceeds bounded score or candidate limits");
        }
        if evidence.health.len() != 1 {
            bail!("exactly one candidate-keyed health assertion is required");
        }
        let (health_candidate, health_ok) = evidence
            .health
            .into_iter()
            .next()
            .context("candidate-keyed health evidence is required")?;
        let scores = evidence
            .scores
            .into_iter()
            .flat_map(|(id, values)| {
                values
                    .into_iter()
                    .map(move |(seed, score)| ((id.clone(), seed), score))
            })
            .collect();
        Ok(Self {
            name: evidence.evaluator,
            scores,

View on GitHub (pinned to 8321021c54)