Terminal Bench shows that a coding agent harness with only terminal input/output tools can match or outperform much more feature-rich harnesses, including native model harnesses. This suggests that added file tools, sub-agents, and built-in workflow features may introduce context pollution and confusion rather than improving capability.
Architects should consider stripping the agent-tool interface to the minimum necessary and letting the model use a generic terminal, instead of building many specialized tools; this can improve benchmark performance and reduce context bloat.
A minimal, generic tool interface (e.g., terminal keystrokes and screen reading) may be a better default for coding agents than a large set of explicit file/edit/sub-agent tools.
All it gives the model is a tool to send keystrokes to a tmux session, and read the output of that tmux session. There's no file tools, no sub-agents, none of that stuff. And it's one of the best performing harnesses in the leaderboard.
Irrespective of model family, Terminus scores higher, mostly higher, even higher than the native harness of that model.