The best AI workbench is not an IDE

There is a common beginner mistake in AI-assisted development: picking a single tool and asking it to do everything. That is how people end up defending editors as if they were operating systems. An editor is not a strategy. It is a window. What matters is the execution surface behind the window: authentication, tool access, agent reliability, MCP support, and whether team knowledge can survive a change of shell. After using Cursor, Cursor CLI, IntelliJ IDEA with AI Assistant wired to external providers, IntelliJ with Kilo Code, and Codex CLI, I arrived at a conclusion that is not fashionable but is practical: IntelliJ should remain the workbench. Codex should become the primary agent. Cursor should be mined for what it does well, mostly skills and rules. Kilo Code should be demoted to utility work such as autocomplete and commit message generation. This is not a benchmark of clever demos. It is a benchmark of operational friction. This is also a personal conclusion, not a team mandate