All core components: broker (hierarchical topic tree with ring buffer replay), configuration (YAML loading with path hierarchy lookups), signature verification (HMAC-SHA256/SHA1), query filters (dot-path equality matching), HTTP server (POST to publish, GET SSE to subscribe, CORS, auth), and the main entrypoint with signal handling. 100% test coverage (excluding main.go) enforced by check-coverage script. 68 tests across 7 test files. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>