Program to an interface: keep agentic capabilities portable across coding harnesses via MCP
mostly_deterministic · reddit · 2026-09-28
A Reddit developer argues that the Cursor rules → Claude Code → Codex/pi/opencode churn keeps destroying harness-specific investments, and that as models converge, differentiation has shifted to the harness layer — with every vendor pushing lock-in.
His proposal applies "program to an interface, not an implementation" to agentic coding:
- Instead of Claude Code plugins (skill prose + ad-hoc code with no general distribution), build core capabilities as a local MCP server or CLI that any harness can expose as tools.
- He uses MCP as the seam between conversational harnesses and durable workflow/tool logic, with LangFuse for observability.
- Hooks go in your own code; a STDIO MCP server takes minimal boilerplate, and capabilities become portable across harnesses.
Harness-specific features can stay, but should be thin icing — the capabilities you really care about must travel.
Related event: Developers Call for Decoupling Coding Skills from Harnesses via MCP(2 posts)→
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