During the middle of a divorce from hell that has been going on for 2 years, I switched jobs in CA and my new employer is going to pay me a large signing bonus. I already get bonuses every year that are and will be calculated with an Ostler Smith percentage.

Is this one time, non recurring signing bonus payment subject to the Ostler Smith? Is it subject to some other calculation? Is she entitled to any of it all?

No - any post-separation bonuses that may have increased your standard of living above what you had when married are not considered in the basis for awarding support. A one-time signing bonus is just that, and can't be considered part of your regular pre-separation income stream.

What does your court order say about what types of bonuses apply to the order? If there is a variable setting in your alimony/child support amount then it may apply. Mostly it is going to depend on how your order reads as far as details.

Hanson Crawford article | Practical Solutions for Obtaining Ostler/Smith Orders Following Marriage of Hall