Sentinel

A stateless MCP server, and the conformance harness that grades it.

On 28 July 2026 the Model Context Protocol shipped the largest breaking revision in its history: it converted MCP from a stateful, session-based, bidirectional protocol into a stateless request/response protocol. Sessions are gone. The initialize handshake is gone. server/discover is mandatory. Server-initiated requests were replaced wholesale by Multi Round-Trip Requests. CacheableResult became required. Sampling, Roots, Logging, HTTP+SSE transport and OAuth Dynamic Client Registration were all deprecated on a twelve-month clock.

Every MCP server in the wild was written against the old idioms. This repository is two things sold together:

They are coupled deliberately. The harness's credibility comes from grading a server that is not its own; the server's credibility comes from being graded. The harness never imports server internals and runs against any endpoint URL.

Status

Work in progress. See docs/superpowers/plans/2026-08-22-sentinel-mvp.md for the work-package plan and docs/HANDOFF.md for the specification this implements.

Related MCP server: FlowMCP

Quick start

make up          # postgres + broker + envoy + smokescreen + otel-collector
make check       # golangci-lint, go test, ruff, mypy, pytest
make scan-broker # grade the broker against its own harness

Requires Go 1.23+, Python 3.12, uv ≥ 0.5, and Docker. No model API key is required anywhere — the broker serves tools, it does not call models, which is why CI is fast, free, and never flaky for a reason outside this repository.

Documentation

• docs/HANDOFF.md — the implementation specification (SN-HND-001).

• docs/MIGRATION.md — what changed in MCP 2026-07-28 and what it costs you. (WP-12)

• CLAUDE.md — the four rules and the single-source-file constraints.

Precedence

Where this repository and the MCP specification disagree, the specification wins and this repository is wrong.

License

MIT — see LICENSE.