Inert runtime skeleton

Issue #6 introduces the smallest production-shaped Yukh MCP process without operational authority. It uses the official modular MCP TypeScript SDK v2 and a stateless Streamable HTTP endpoint at /mcp.

The runtime deliberately registers empty tools, resources, and prompts capabilities. Initialization and discovery work, but no handler can inspect or change a target. There is no authentication adapter, authorization evaluator, provider registry, credential loader, approval service, audit store, task API, resumability, or mutation path.

HTTP surface

Route	Method	Purpose
/healthz	GET	process liveness only
/readyz	GET	listener and inert MCP handler readiness
/mcp	POST	stateless MCP initialization and empty discovery

Other routes return a bounded 404; non-POST MCP requests return 405. The runtime does not open a long-lived notification stream in this phase.

The listener defaults to 127.0.0.1:3000. Binding to all interfaces requires an explicit host allowlist. Host validation protects the MCP route against DNS rebinding; browser requests with an Origin header are denied unless that exact origin is configured. MCP bodies are bounded before SDK parsing.

Configuration

Variable	Default	Bound
YUKH_HOST	127.0.0.1	loopback or explicit wildcard enum
YUKH_PORT	3000	0..65535; zero is test-only ephemeral binding
YUKH_ALLOWED_HOSTS	127.0.0.1,localhost	1–32 hostnames; required for wildcard bind
YUKH_ALLOWED_ORIGINS	empty	0–32 exact URLs
YUKH_MAX_BODY_BYTES	65536	1 KiB–1 MiB
YUKH_SHUTDOWN_TIMEOUT_MS	5000	100 ms–30 s

Configuration errors expose field names, never submitted values. Environment variables outside this registry are ignored and cannot register capabilities.

Logging

Runtime logs are closed JSON records containing timestamp, registered event, level, server-created correlation reference, bounded HTTP status, and an allowlisted code. Request bodies, headers, URLs, host/origin values, exception messages, stack traces, client identity, and MCP payloads are excluded.

These logs are operational diagnostics, not RFC-0004 protected audit evidence. No audit durability or integrity claim is made.

For local commands, use Run the inert gateway.

The base-image tag is version-pinned but not digest-pinned. Image provenance, digest selection, SBOM, signing, and release qualification remain governed by issue #10.

Compatibility

The server uses createMcpHandler from @modelcontextprotocol/server 2.0.0 with its stateless compatibility mode. New protocol features remain disabled until separately reviewed. The implementation follows the official MCP TypeScript server guide.