An overabundance of single-transiting Kepler planets suggests the existence of a sub-population of intrinsically multi-planet systems possessing large mutual inclinations .
However , the origin of these mutual inclinations remains unknown .
Recent work has demonstrated that mutual inclinations can be excited soon after protoplanetary disk-dispersal due to the oblateness of the rapidly-rotating host star , provided the star is tilted .
Alternatively , distant giant planets , which are common in systems of close-in Kepler planets , could drive up mutual inclinations .
The relative importance of each of these mechanisms has not been investigated .
Here , we show that the influence of the stellar oblateness typically exceeds that of an exterior giant soon after planet formation .
However , the magnitude of the resulting mutual inclinations depends critically upon the timescale over which the natal disk disperses .
Specifically , we find that if the disk vanishes over a timescale shorter than \sim 10 ^ { 3 - 4 } years , comparable to the viscous timescale of the inner \sim 0.2 AU , the inner planets impulsively acquire misalignments that scale with the stellar obliquity .
In contrast , if the disk disperses slowly , the inner planets remain coplanar .
They first align with the stellar equator but subsequently realign with the distant giant ’ s plane as the star spins down .
Our findings are consistent with recent observations that giants tend to be aligned with close-in multis but misaligned with singles .
Stellar obliquity measurements offer a promising test of our proposed framework .