If you're looking for a Cosine alternative, Bito is worth a look. Bito is a suite of AI-powered coding tools that can speed up your workflow with tools like AI code reviews, chat help, code completions, prompt templates and automations. It can connect to GitHub and GitLab for a broad tool suite to help you write code more efficiently and accurately.
Another good choice is Sourcegraph. It's a service geared to help developers get more done with tools like Cody, Code Search, Batch Changes and Code Insights. Sourcegraph supports many programming languages and code hosts, and it can connect to many IDEs. It can be deployed in the cloud or self-hosted, too, so it's a flexible option for understanding your codebase and getting work done.
Metabob is another alternative worth considering. It uses graph-attention networks and generative AI to help with code review, refactoring and debugging. Its features include AI code review, software security scanning and debug and refactor tools. Metabob can be self-hosted, too, which can be important if you're worried about security or want to use it to maintain legacy code and validate AI-generated code.