Technical guide
Why HVAC agents must abstain when no exact OEM source exists
A field-service copilot that guesses on inverter boards destroys trust faster than it saves truck rolls. Abstention with audit trail is a product requirement, not a nice-to-have.
Updated 30 August 2026
The cost of a confident wrong answer
Replacing the wrong board or authorising a refrigerant charge without an OEM page costs more than API fees. LLMs default to fluency — HVAC needs provenance.
What abstention looks like in API v2
When strict source_policy cannot bind document_id + page_start from manufacturer authority, the API returns an explicit non-answer — not a paraphrase of forum posts.
Implication for your agent stack
Wire abstention into escalation: ticket remains open, human sees the missing source, Marcel Inside or tier-2 takes over. See /api/docs/quickstart for sourced vs abstain examples.