Here is a general question, I am planning a project and will eventually get
all proper permits but I want some advice to determine if this step is
necessary

I am planning to install a steam room in a new bathroom and it requires a
35A, 220V dedicated breaker. My house has a 100A service panel with one 50A
to the range, one 35A to the drier and about a dozen 20A wall plug circuits.

The question is: Is it likly that I will need to simultaniously upgrade the
service panel to 150A when adding this circuit? What is the rule about the
maximum capacity of a service panel?

I know it depends on where I live (CA) etc. I am just looking for direction
before I go in for permits and get rejected for omitting something
important.