New observables
- Leptonic kaon decays `BR(KL->mumu)`, `BR(KS->mumu)` (as well as the electronic modes)
- Lepton flavour violating kaon decays `BR(KL->emu,mue)`, `BR(KS->emu,mue)`
- π→μν total rate, `Gamma(pi+->munu)`
- Some additional Z and W pole observables, e.g. the LFU ratio `Rmue(W->lnu)`
Other improvements
- The B→D and B→D* form factor parameters have been improved: while still using the parametrization from [arXiv:1801.01112](https://arxiv.org/abs/1801.01112), the parameters have been updated from a fit where the LCSR input is taken from [arXiv:1811.00983](https://arxiv.org/abs/1811.00983) rather than [arXiv:0809.0222](https://arxiv.org/abs/0809.0222). This leads in particular to a more reliable prediction for R<sub>D</sub> and R<sub>D*</sub>.
- Various parametric updates, e.g. quark masses are now taken from [lattice QCD](https://arxiv.org/abs/1802.04248).
- Correlation among B meson bag parameters from FLAG now properly taken into account.
- Two-dimensional likelihoods of the CMS and ATLAS measurements of B<sub>s,d</sub>→μμ added (thanks Peter Stangl!)
Breaking change
- The CKM parameter `gamma` has been renamed to `delta` to more accuretely reflect the fact that this is treated internally precisely as the Dirac phase δ. Although this is numerically almost identical with the unitarity triangle angle γ, it is not equivalent.
Fixes
- Factor of 2 in `tau->emue` and `tau->muemu` fixed (thanks to Andrzej Buras!)
... and a couple of smaller fixes.