  The production cross section of $t\bar{t}\gamma$ is measured in the dilepton
channel using 138 fb$^{-1}$ of proton-proton collision data recorded by the CMS
experiment at $\sqrt{s}= 13 $ TeV during the 2016-2018 data-taking period of
the CERN LHC. A fiducial phase space is defined at the particle level in which
both inclusive and differential results are provided. The $t\bar{t}\gamma$
process is sensitive to EFT operators that modify the top-photon coupling, so
that tight constraints on the $c_{tZ}$ and $c_{tZ}^{\mathrm{I}}$ Wilson
coefficients can be extracted. Finally, the EFT interpretation is repeated on a
combination of this result and a measurement of $t\bar{t}\gamma$ production in
the lepton+jets channel.
