01INTAKE
Tech writes up the truck.
A tech rolls up on the call, opens /diagnose on the FSM tablet, and posts the symptom — text, photo, voice note, or a fault code straight off the control board. The intake is four fields; nothing else is gated.
// /how-it-works · diagnostic loop · 5 stages
From the truck to a bench-signed verdict in five stages.
This is the loop the founder built the shop around: the tech posts a symptom on the tablet, the engine returns ranked probable causes, the bench escalates whenever the AI is uncertain or a callback is on the line, and the verdict ships signed inline.
How the loop closes
// 5 stages · same tape /diagnose reads
02SCORING
The deterministic engine ranks.
Lowercased word tokens are scored against the seeded library of HVAC, plumbing, electrical, and appliance fault fingerprints. A clean fault-code match contributes +5; corroborating photo or voice hints contribute +2 each.
03RANK OUTPUT
Top three probable causes ship.
The engine returns the top three causes with confidence, a written remedy, and a parts cross-reference anchored to the leading cause’s repair path. Bench updates this list once a real run completes.
04ESCALATE-TO-BENCH
A specialist reads the tape when confidence dips.
If any ranked cause sits under 65%, the ticket is on a warranty job, or a callback is on the line, the ticket escalates to the bench. A diagnostic specialist reads the transcript and writes a signed second opinion that lands inline with the AI output.
05CALLBACK-PREVENTION OUTCOME
One trip. The verdict ships signed.
Tech ships one trip with the ranked cause, the bench-signed second opinion, and the parts cross-reference already in the cab. No return ticket, no callback dispatch, no Sunday-night phone call for the owner.
What a ticket looks like end-to-end
// same shape /demo renders
The left card is what the tech wrote up on the truck — prefilled so a service manager can read along. The right column is what the engine returns: ranked probable causes once the deterministic scoring runs, with a parts cross-reference and a procedure on the bench tape underneath.
INTAKE
// pre-loaded · read-onlyWhat the tech wrote up.
The same four inputs the live /diagnose form collects — locked here so the loop reads top-to-bottom.
Photo
attached · ir-led-receipt.jpg
Voice note
none
// seeded from /lib/data/demo-scenario · E3 furnace no-cool
RANKED OUTPUT
// result panel reused from /demoRANKED
// top 3 of seedProbable causes, in order.
Each card shows the confidence the engine placed on this fault.
01
HVAC
Blower motor failure
confidence
100%
No airflow at the supply registers; motor is hot, surging, or completely dead.
remedyPull the blower door, watch the module for flashing LEDs, then bench-test the motor windings.
02
HVAC
Low refrigerant charge
confidence
68%
Suction line ices, delta-T collapses at the return, and superheat climbs above design.
remedyRecover the remaining charge, leak-search at the evaporator and line set, then weigh in by spec.
03
HVAC
Bad run/start capacitor
confidence
42%
Outdoor fan hums but does not spin, or hard-starts under load; microfarads drift from nameplate.
remedyDischarge safely, measure MFD against rating (±5%); replace both caps if dual-rated.
// Ready to run it?
Pick the lane your trucks are in — Starter, Bench, or Multi-Trade.
The intake on the right is read by an owner within one business day. For Multi-Trade shops, drop the verticals in the follow-up email and the bench pool gets scoped on the call.