Was/is thinking

When a person says, “I am thinking of going…”, they are indicating an ongoing intention. The idea is still being contemplated but hasn’t been fully tested. By comparison, “I was thinking of going…”, sounds as though the decision was already made that it isn’t likely to happen. Sometimes the words indicate the person is asking for input.

Then, in the following conversation, should it be 'am' like the underlined part?

A: Are you going to buy a gift for Jason?
B: Yes. I am thinking of getting him a bicycle.
A: When are you going to buy one?

lucas21cA: When are you going to buy one?

Yes, the conversation is appropriate. However, discretion usually dictates that the response to "...am thinking of..." would be along the lines of "What are your limitations or reason for holding back? How much do you plan to spend?" The reason for this would be that the decision still hasn't been confirmed.

Then how about the following one?

A: Are you going to buy a gift for Jason?
B: Yes. I was thinking of getting him a bicycle.
A: When are you going to buy one?

No, that doesn’t change that there has been no decision. If the response from B had been “Yes. What do you think of my getting him a bicycle?” Then, A could follow-up with the comment, “That sounds ideal. When will you buy it?”

lucas21cCould you tell me which one is more natural between (A) and (B) in the following sentence? Thank you.I [ (A) am / (B) was ] thinking of going to Paris during this vacation.

You can also add I've been thinking. They are all natural, but to my ear, they suggest different levels of commitment to the idea of carrying out the project. From stronges