Context : Of the presently known \approx 3900 exoplanets , sparse spectral observations are available for \approx 100 .
Ultra-hot Jupiters have recently attracted interest from observers and theoreticians alike , as they provide observationally accessible test cases .

Aims : We aim to study cloud formation on the ultra-hot Jupiter HAT-P-7b , the resulting composition of the local gas phase , and how their global changes affect wavelength-dependent observations utilised to derive fundamental properties of the planet .

Methods : We apply a hierarchical modelling approach as a virtual laboratory to study cloud formation and gas-phase chemistry .
We utilise 97 vertical 1D profiles of a 3D GCM for HAT-P-7b to evaluate our kinetic cloud formation model consistently with the local equilibrium gas-phase composition .
We use maps and slice views to provide a global understanding of the cloud and gas chemistry .

Results : The day/night temperature difference on HAT-P-7b ( \Delta T \approx 2500 K ) causes clouds to form on the nightside ( dominated by \ce H2/He ) while the dayside ( dominated by H/He ) retains cloud-free equatorial regions .
The cloud particles vary in composition and size throughout the vertical extension of the cloud , but also globally . \ce TiO2 [ s ] / \ce Al2O3 [ s ] / \ce CaTiO3 [ s ] -particles of cm-sized radii occur in the higher dayside-latitudes , resulting in a dayside dominated by gas-phase opacity .
The opacity on the nightside , however , is dominated by 0.01 \ldots 0.1 ~ { } \mu m particles made of a material mix dominated by silicates .
The gas pressure at which the atmosphere becomes optically thick is \sim 10 ^ { -4 } bar in cloudy regions , and \sim 0.1 bar in cloud-free regions .

Conclusions : HAT-P-7b features strong morning/evening terminator asymmetries , providing an example of patchy clouds and azimuthally-inhomogeneous chemistry .
Variable terminator properties may be accessible by ingress/egress transmission photometry ( e.g. , CHEOPS and PLATO ) or spectroscopy .
The large temperature differences of \approx 2500 K result in an increasing geometrical extension from the night- to the dayside .
The chemcial equilibrium \ce H2O abundance at the terminator changes by < 1 dex with altitude and \lesssim 0.3 dex ( a factor of 2 ) across the terminator for a given pressure , indicating that \ce H2O abundances derived from transmission spectra can be representative of the well-mixed metallicity at P \gtrsim 10 bar .
We suggest the atmospheric C/O as an important tool to trace the presence and location of clouds in exoplanet atmospheres .
The atmospheric C/O can be sub- and supersolar due to cloud formation .
Phase curve variability of HAT-P-7b is unlikely to be caused by dayside clouds .