cad-mcp-cleanroom

cad-mcp-cleanroom is a cleanroom acceptance harness for CAD-style MCP command surfaces. It proves that a server's commands are deterministic, honestly declared read-only, and idempotent under replay, then emits a machine-readable PASS or REJECT report. The pitch is that if an agent will drive a CAD server unattended, this audit should run before letting it run anything.

The audited server implements a tiny protocol, execute(name, args) returning ok, data and error, plus state_hash(). Commands in a JSON manifest declare purity as read-only or mutating, and the harness checks determinism (run a read-only command N times and compare SHA-256 hashes of canonical output), purity (hash state before and after a read-only command), idempotence (apply a mutating command, hash, re-apply, hash), schema (output keys against declared types), and session drift (replay the manifest through two fresh sessions and compare outputs).

The README states its confidence plainly: high (85 percent) that replay-based purity and idempotence probing catches the mutation bugs agent loops actually hit, and medium (65 percent) that the bundled demo server resembles a real server's failure modes, both marked as estimates. The harness ships with a demo server; it audits a command surface, not a CAD design.