yoi/.yoi/tickets/00001KVHR3WRY/item.md

title	state	created_at	updated_at	assignee	readiness	risk_flags	queued_by	queued_at
MCP: implement stdio JSON-RPC lifecycle client	closed	2026-06-20T05:30:04Z	2026-06-20T07:59:30Z	null	implementation_ready	mcp stdio json-rpc process-lifecycle diagnostics	workspace-panel	2026-06-20T05:58:54Z

Background

After MCP local stdio server config exists, Yoi needs a lifecycle client that can start a configured server, speak newline-delimited JSON-RPC over stdio, perform MCP initialize/capability negotiation, and shut down safely.

This Ticket creates the protocol/lifecycle foundation only. It does not expose MCP tools/resources/prompts to the model-visible ToolRegistry.

Requirements

• Spawn configured local stdio MCP servers from explicit config only.
• Use stdin/stdout newline-delimited JSON-RPC.
• Treat stdout as protocol messages.
• Treat stderr as bounded diagnostics/logging, not automatic protocol failure.
• Implement initialize, capability negotiation, and notifications/initialized.
• Track server name and startup phase in diagnostics.
• Implement graceful shutdown, terminate, and kill fallback.
• Handle process exit/disconnect/startup failure with bounded diagnostics.
• Do not declare sampling or elicitation client capabilities initially.
• Add local mock MCP server tests.

Acceptance criteria

• Mock local stdio MCP server initializes successfully.
• Initialize failure reports server name and phase.
• stderr is bounded and redacted where needed.
• Shutdown is safe and deterministic.
• Sampling/elicitation are not advertised and fail closed if requested.
• No tools/resources/prompts are registered by this Ticket.

Non-goals

• tools/list ToolRegistry registration.
• tools/call execution.
• resources/prompts operations.
• Streamable HTTP/OAuth/remote MCP.

Related work

• Depends on 00001KVHR3WRF.
• Objective: 00001KTR80WMN.