Confusion about HSA eligibility rules when family members have different health insurance plans

People with Health Savings Accounts struggle to understand complex IRS rules about whether they can use HSA funds for dependents or spouses covered under different health insurance plans. Current solutions fail because HSA rules are counterintuitive (you can't use HSA funds for someone on a non-HDHP plan, even if they're your dependent), and people waste time researching or make costly mistakes by withdrawing funds incorrectly and facing tax penalties.