Abstention

Abstention

When Bivia isn’t confident enough to give a reliable answer, it abstains instead of guessing. This is a feature, not a failure — you always know whether to trust the answer.

How it works

Every response includes a status field:

• answered — the model is confident. value contains the answer.
• abstained — the model is not confident. value is null.

{
  "status": "abstained",
  "value": null,
  "abstain_reason": "low_confidence",
  "distribution": { "yes": 0.52, "no": 0.48 }
}

Even on abstention, the distribution is still returned so you can see how the probability mass was spread.

Abstention reasons

Reason	Meaning
low_confidence	Probability mass was too spread across options
readout_disagreement	Deep-mode verification found a conflict
insufficient_evidence	Not enough context to decide
unresolved_after_thinking	Reasoning did not resolve ambiguity

Controlling abstention

By default, allow_abstain is true. Set it to false to force a best-effort answer:

{ "question": "...", "allow_abstain": false }

In deep mode, abstention is always possible (the verification step may trigger it regardless of allow_abstain).