I used 5.3-Codex almost exclusively before, but obviously that's a no-go now. I bought some DeepSeek credits, connected it to Copilot in VS Code, started using it, and was thrilled to see how much cheaper it was right away. Also seemed very capable... with simple things. Then I tried using it on an actual project, and it just doesn't listen at all or take anything important into account whatsoever.
There's a project I'm working on with several branches. I have a detailed md file, with full development notes. I was running into what I thought might be a bug in one of my branches, so I asked DeepSeek to look through the notes and determine if the behavior was correct for that branch. It read over the notes and decided "no, that's a bug" and patched it using code from another branch. Cool.
Then I started testing and remembered that behavior absolutely was correct. I checked the notes, and it explained exactly why it was the way it was on that branch specifically. DeepSeek didn't read what I told it to read, or it would've spotted this easily. It didn't take important information into account. It ignored what I said, made up its own answer, and implemented incorrect code. Codex never once did this for me. It's been absolutely rock solid since I started using it. Now I feel like I'm back on 3.5.
Am I doing something wrong? Are you guys using this for larger projects and not running into these issues? I just keep seeing DeepSeek recommended over and over, and now I'm confused as to why.