Use nothing abrasive on solid stainless or anodised surfaces, where a scratch is permanent and visible. Combi-steam models need descaling on the manufacturer's schedule. On an appliance at this price the real consideration is who is insured if a panel is damaged.
Gaggenau sits at the top of BSH, above Bosch and Neff, and it is usually the most expensive single appliance in the house.
That changes the nature of the advice.
Insurance is the headline, not a footnote
On a mass-market oven, a scratched panel or a cracked glass is annoying and inexpensive. On a Gaggenau it is a four figure part and frequently a special order with a wait.
So the question worth asking before anyone touches it, yourself included, is who carries that risk. If you clean it and damage a fascia, you carry it. If a contractor does and they are not insured, you very likely still carry it, because recovering from an uninsured sole trader is a theoretical remedy rather than a practical one.
This is the single most important thing to get right on this brand, and it has nothing to do with cleaning products.
Surfaces that do not forgive
Gaggenau uses solid stainless and anodised finishes rather than the painted and printed surfaces further down the market. They look superb and they mark permanently.
Nothing abrasive, ever. No cream cleanser, no scourer, no pad rougher than a soft cloth on any external surface. Stainless is worked along the brushed grain, never across it, because a swirl pattern on a large flat panel at eye level is visible from across the room and cannot be polished out selectively.
Combi-steam wants descaling
Many Gaggenau ovens are combi-steam, with a water circuit and a reservoir. That circuit scales, and a scaled circuit delivers less steam while the appliance reports normal operation.
Use the manufacturer's descaling procedure and product rather than a general kettle descaler, because the circuit runs through components a strong acid will damage. On an appliance of this value that is not a place to improvise.
The cavity
Follow whatever the cavity surface calls for, which our oven cleaning guide covers. What changes here is not the method but the tolerance for error.
Why these are cleaned less often than they should be
There is a pattern worth naming on Gaggenau specifically, and it runs opposite to what you would expect.
An expensive appliance tends to be cleaned less thoroughly, not more, because the owner is nervous about it. People who would happily attack a mass-market oven with a pad and a strong cleaner will approach a Gaggenau with a damp cloth and hope, and a damp cloth does not remove baked carbon from a cavity roof.
So these accumulate quietly while being wiped regularly, and the appliance that could most afford proper maintenance often gets the least.
The resolution is not more aggression, it is the right method: the correct product for the cavity surface, applied with a genuine dwell so the chemistry does the work, and nothing abrasive anywhere near the external finishes. That combination is entirely safe on a Gaggenau and it is what a nervous damp cloth never achieves.
What actually goes wrong
A scratched fascia or panel, permanent and expensive.
A descaling shortcut with the wrong product.
Swirl marks on stainless, from working across the grain.
Should you do it yourself?
Do it yourself for routine wiping, along the grain, with a soft cloth.
Get someone in for anything more, and check they are insured before they start. See how to clean a Gaggenau cooktop and how to clean a Gaggenau rangehood.