Cosine

Cosine's Genie is trained on actual pull request data, which shows. Point it at a bug and it doesn't just suggest a fix—it writes the code, runs tests, iterates on failures, and opens a PR. The autonomy matters because you can hand off a GitHub issue at 6pm and wake up to a working branch. I've used it for gnarly multi-file refactors where the context spans five modules and three config files. It held the thread better than I expected. The sweet spot is tedious but well-scoped work: migrating a deprecated API across twenty call sites, fixing a flaky test that needs log analysis and retry logic, or backporting a feature to an older branch. Genie reads your codebase, proposes a plan, then executes without needing approval at every step. You review the final PR like you would from a junior engineer. Failure modes are predictable. If the task is vague ('make the app faster'), it flails. If your repo lacks tests, it can't verify its own work and you're back to manual QA. It also struggles with architectural decisions—don't expect it to choose between microservices and a monolith. The CLI is solid but the web interface feels like an afterthought; I spend most of my time in the terminal. Compared to Devin, Genie is narrower but more reliable. Devin tries to be a full engineering teammate; Genie is content being a very good intern. It doesn't do product thinking or talk to APIs it hasn't seen before. But for the bug-fix and refactor lane, it's faster and less likely to go off-piste. The PR training data is the differentiator—it writes code that looks like code a human would commit, not like a chatbot transcript. Pricing is steep for solo devs but reasonable for teams. You're paying for time saved, and on a three-hour refactor that Genie handles in forty minutes, the maths works. The async workflow is the real unlock: queue up tasks, let it churn overnight, review in the morning. If you're drowning in maintenance debt or shipping solo, it's worth the trial.