The two categories share a shelf in the buyer’s mind and almost nothing else. Read any procurement shortlist in the DACH region and you will find a Systemhaus sitting next to a product studio, because both answered a brief that said “we need software people”. The word Dienstleister covers both in German, which is exactly why the shortlist forms.
Start from the deliverable, because everything else follows from it. An IT service provider is paid to make sure things that already exist keep working: the network, the laptops, the file server, the cloud tenancy, the identity provider, the backups. Success is measured in uptime and response time. A software agency, also searched for as a software service provider or Softwaredienstleister, is paid to make something that does not exist yet work in production. Success is measured in whether the thing shipped, and whether it did what the business needed.
That difference propagates straight into the contract. Managed IT naturally sits on a Dienstvertrag or a framework agreement: an obligation of effort, with an availability promise bolted on. Custom software delivery naturally sits on a Werkvertrag: an obligation of result. Once you notice that, comparing day rates across the two stops making sense, because you are not buying the same kind of promise. A cheaper hourly rate attached to an effort obligation is not cheaper than a higher rate attached to a result obligation.
It also propagates into who is in the room. Operations organisations are staffed and rewarded for stability: predictable process, low change rate, clear escalation paths. Product organisations are staffed and rewarded for judgement under uncertainty: deciding what not to build, changing direction when evidence arrives. Both are legitimate engineering cultures. Neither converts easily into the other, which is why a vendor that genuinely does both usually runs them as two separate businesses with two separate hiring bars.
So when a firm from either category offers the other as a service line, the question is not whether they are honest. It is who staffs it. Ask how many people work on that line, whether they are the same people who handle the core business, and what they shipped most recently. The answer is usually informative and easy to get.
The healthy end state for most companies past a certain size is both, from two different vendors, with a clear handover boundary written down before the build starts. We have worked in exactly that arrangement: on the IKB engagement our work sat inside the utility’s own build, on infrastructure, devices and codecs, with a complete handover after year one. We were never the operator of the surrounding systems and never claimed to be.
Where does that leave Wavect? On one side of the line, deliberately. We build and hand over custom software. We do not run IT operations: no helpdesk, no workstation or network management, no 24/7 on-site desk, no operational SLA. If your actual problem is that nobody is keeping the lights on, we are the wrong call and an IT service provider is the right one. If your actual problem is that something needs to exist and reach production, that is our work, and the code transfers to you.