Gemini 2.5 Pro vs. Claude 3.7 Sonnet: Coding Comparison

From my use case, the Gemini 2.5 is terrible. I have a complex Cython code in a single file (1500 lines) for a Sequence Labeling. Claude and o3 are very good in improving this code and following the commands. The Gemini always try to do unrelated changes. For example, I asked, separately, for small changes such as remove this unused function, or cache the arrays indexes. Every time it completely refactored the code and was obsessed with removing the gil. The output code is always broken, because removing the gil is not easy.

For me I had to upload the library's current documentation to it because it was using outdated references and changing everything that was working in the code to broken and not focusing on the parts I was trying to build upon.

If you don't mind me asking how do you go about this?

I hear people commonly mention doing this but I can't imagine people are manually adding every page of the docs for libraries or frameworks they're using since unfortunately most are not in one single tidy page easy to copy paste.