Could you tell me if I want to inquire a person what he does and he answers that he writes fiction and I tell him "I thought you wrote poetry." Or "I thought you WRITE poetry.", the action is in the present - the writing .
In my view, without more context, the following sentence has three possible interpretations
I thought you wrote poetry
In the past the speaker knew, or they had been led to believe, that the listener wrote poetry. The speaker may be expressing their surprise (I was wrong!) or disbelief (where did I get this idea from?) that the listener is not a poet. The statement is equivalent to: “Someone told me you wrote poetry but I now realise that this is not true.”
The speaker expresses their uncertainty as to whether the listener writes poetry now (this may also include the past but we have no way of knowing). The speaker is using the past simple to suggest uncertainty in the present. It is the hesitant equivalent to the statement
“I think you write poetry” = “I think you are a poet"
The speaker discovers that the listener is indeed someone who writes poetry. By stressing the first verb (thought) the speaker is asserting that they had held this belief in the past but they were not certain, this contrasts with the “now”, their finding out the truth. In other words, their former belief has been confirmed. “I thought you wrote poetry (and I was right)"
/I thought you wrote poetry/. Thought [at some point in the past] and wrote occurred in the definite past. That is what I thought you did (for a living or in life), which implies, now that we are talking, this is either TRUE or NOT TRUE.
A sentence such as: /I though you wrote poetry/ is uttered at a present time when the person saying it is referring to a definite time when he or she thought a particular thing about someone or something. But, the utterance is uttered in the present. In other words, /I thought you wrote poetry/ is the past tense of /I think you write poetry/.
I thought you wrote poetry but now I see you're writing fiction.
Well, John, I think you write poetry [generally] even if you think it's fiction.
OR **Well, John, I think you're writing poetry [these days] even if you think it's fiction. OR [even if think you're writing fiction].
When you use the simple past thought/wrote, there is an implied comparison to the present, where you might think something different.
I think [something now]. I thought [something different about the past: wrote, were writing, had been writing]
Simple past (thought) plus simple present is not grammatical in English, afaik.
I'm thinking [as we're speaking] that you write poetry [generally] or are writing [these days] poetry.