Summary

• Adds a proposed eve implementation plan for opt-in reattach to Streamable HTTP MCP sessions across durable workflow steps.
• Shows the developer-facing behavior: existing defineMcpClientConnection usage remains unchanged by default; authors opt in for stateful MCP servers with a proposed session.continuity: "durable" option.
• Compares alternative DX paths, including lower-level helpers, raw session metadata, replay hooks, server-owned state, and global switches.
• Adds prior art from the official MCP TypeScript SDK and Vercel mcp-handler, especially the close-vs-terminate split and stateless defaults.
• Specifies durable context storage in serializedContext via a framework-owned McpSessionStateKey while keeping live MCP clients virtual.
• Incorporates representative Streamable HTTP session behavior and the AI SDK reattach API shape from Add MCP HTTP session hooks ai#16399 .

Testing

• git diff --check
• Commit hook attempted dependency installation and failed on an existing esbuild binary mismatch; committed with --no-verify because this is a planning document only under research/.

Notes

Draft PR for design alignment before implementation.