The build is not the expensive part. The second year is

There is a way these projects stop being maintained that has nothing to do with the code being bad. One person built it, one person understood it, and one person left.

What leaves with them is not the repository. It is the reasoning: why a particular refusal is worded that way, which two instructions must never be edited in the same week, what the experiment that did not work proved, which of the connected systems lies about its own field names. None of that was written down, because nobody writes it down while shipping. What remains is a service that still answers the phone and that nobody is willing to change, which is a slower and more expensive problem than an outage, because it looks fine from the outside for months.

The same shape applies to a supplier, and the question should be put to one. A vendor whose entire voice capability rests on a single engineer carries an identical concentration of risk, arriving with an invoice attached. The follow-up worth asking after any confident answer is who else there can do that. It is very hard to answer smoothly if the answer is nobody.

The two disciplines that dissolve most of this are unglamorous and observable from the outside: the evaluation set exists as a written artefact rather than as somebody's judgement, and there is a gate between a change and the live number. We describe both on how an agent gets verified before it speaks to a customer and where an agent's rules have to live.

Often enough that a page concluding otherwise from a supplier would be worth ignoring. Three conditions, and they have to hold together rather than individually. The calls are the product rather than a channel to it, which makes the conversation logic core intellectual property. There is a permanent team rather than a person, large enough that a rotation survives a resignation and a holiday. And the domain is idiosyncratic enough that the translation cost between your experts and anyone else exceeds the build. Two more conditions each settle it alone: a call volume at which the unit arithmetic stops favouring any service, a line whose position depends on your own call mix and which no supplier will calculate for you, including us; and a requirement that the audio never reaches a third party at all, which rules out most suppliers by construction rather than on merit.

If the three hold together, or if either of the other two does, build, and we would say so on a call. The architecture for one regulated vertical is set out on our guide to building a voice agent for debt collection, including the unglamorous layers that hold up launches.

Where exactly one of the three holds, the workable answer is usually a split rather than a choice: own the policy and the evaluation set, because that is where the knowledge is and it should never leave the business, and rent the operating burden, because that is where the headcount is.

Forty-five minutes on your actual call flow. We take the policies your front desk already follows, work through the edge cases that break them, and you keep the written version at the end whether or not anything else happens between us. It is the first draft of the evaluation set, and it is useful to a team that goes on to build the thing themselves. Where an engagement follows, it is one workflow, missed calls and after hours, roughly two weeks, before anything else moves.