Don't lock into coding harnesses: build agent capabilities behind MCP interfaces

mostly_deterministic · reddit · 2026-09-28

A Reddit post argues that with Cursor, Claude Code, Codex, and opencode trading market share every few months, maintaining harness-specific cursor rules and plugins violates "program to an interface, not an implementation."

The author's proposal: treat frontier coding harnesses as the implementation and build your agentic capabilities behind a stable interface — make the harness swappable. Concretely: build local MCP servers or CLIs instead of harness-bound skill plugins; split the conversational harness from durable workflow/tool logic; use LangFuse for observability; a STDIO MCP server needs minimal boilerplate and distributes via your language's ecosystem. Harness-specific features stay as thin icing, while the complex capabilities you care about remain portable. The author reports this MCP-as-seam approach working well and sees early convergence in the ecosystem.

Related event: Developers Call for Decoupling Coding Skills from Harnesses via MCP(2 posts)→

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