They can assign you to the California office, but you have to make sure that they do not report any California wages or withhold any California tax. Being a Texas resident will not stop them from reporting California wages. A resident of Texas (or any other state) who travels to the California office and works there has California income and has to pay California tax. There's a good chance that your employer has never had an employee who was assigned to the California office but didn't actually work in California. The payroll system might not be set up to handle that. It probably, by default, reports wages as being from the office you are assigned to, not from where you live.
If your W-2 shows California wages or withholding, California will assume that you worked in California, and will expect you to pay California tax. Being a Texas resident will not prevent that. As I said earlier, incorrect reporting can be difficult to fix after the fact. And California has a reputation for being particularly aggressive about collecting tax from anyone who they think should be paying it.
