Striff Tool Flags MCP C# SDK's Copilot Instructions Referencing a Class Deleted in December
zir093 · reddit · 2026-09-30
Developer richardbaxter launched Striff, a GitHub App that reads repo docs (README, AGENTS.md, CLAUDE.md, copilot-instructions.md), converts code-claiming sentences into rules, and checks them on every PR.
It flagged a real case in the official MCP CSDK:
- Line 258 of .github/copilot-instructions.md still says "Use McpServerFactory" — a class that no longer exists
- Timeline: marked obsolete Sep 16, 2025; Copilot wrote the instructions file Oct 13 (four weeks after deprecation); a Copilot-authored PR removed the class Dec 2 without touching the instructions; still on main today, fix PR #1892 opened
- Nobody erred: instruction reviewers saw a mostly-correct long file, deletion reviewers saw a diff without the file — that gap is what Striff checks
- Author asks: do you verify your agent instruction files against the code, or do they drift until something breaks?
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