Is it okay to say "I thought breakfast IS ready"? Is it different from this one?

Native speaker’s answer
Rebecca
"I thought breakfast is ready" would be grammatically incorrect. "Thought" is past tense and therefore has to be used in conjunction with the past tense be verb "was". This is not a changeable rule. The be verb has to match the tense of the other verb in the sentence. Ex: I think breakfast is ready. Ex: I thought breakfast was ready. Ex: I think breakfast will be ready.