CA taxes non-residents only on CA-source income. Income is "sourced" where the work is actually (physically) performed. So you only have to pay CA income tax on the portion of your income earned by actually working in CA.
CA law considers a person to be a CA resident (for tax purposes) if that person "is in California for other than a temporary or transient purpose." Since that's kind of vague, CA publishes a whole booklet on the issue of residency. The examples on pages 4-5 should help you determine your status: https://www.ftb.ca.gov/forms/2018/18_1031.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
