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The microphysics of ~GeV cosmic ray (CR) transport on galactic scales remaindeeply uncertain, with almost all studies adopting simple prescriptions (e.g.constant-diffusivity). We explore different physically-motivated, anisotropic,dynamical CR transport scalings in high-resolution cosmological FIREsimulations of dwarf and ~$L_{\ast}$ galaxies where scattering rates vary withlocal plasma properties motivated by extrinsic turbulence (ET) orself-confinement (SC) scenarios, with varying assumptions about e.g. turbulentpower spectra on un-resolved scales, Alfven-wave damping, etc. Weself-consistently predict observables including $\gamma$-rays ($L_{\gamma}$),grammage, residence times, and CR energy densities to constrain the models. Wedemonstrate many non-linear dynamical effects (not captured in simpler models)tend to enhance confinement. For example, in multi-phase media, even allowingarbitrary fast transport in neutral gas does not substantially reduce CRresidence times (or $L_{\gamma}$), as transport is rate-limited by the ionizedWIM and 'inner CGM' gaseous halo ($10^{4}-10^{6}$ K gas within 10-30 kpc), and$L_{\gamma}$ can be dominated by trapping in small 'patches.' Most physical ETmodels contribute negligible scattering of ~1-10 GeV CRs, but it is crucial toaccount for anisotropy and damping (especially of fast modes) or elsescattering rates would violate observations. We show that the mostwidely-assumed scalings for SC models produce excessive confinement by factors>100 in the WIM and inner CGM, where turbulent and Landau damping dominate.This suggests either a breakdown of quasi-linear theory used to derive the CRtransport parameters in SC, or that other novel damping mechanisms dominate inintermediate-density ionized gas.

Testing Physical Models for Cosmic Ray Transport Coefficients on Galactic Scales: Self-Confinement and Extrinsic Turbulence at GeV Energies