Summary

Draft SEP proposing the removal of protocol-level sessions from MCP, replacing implicit session-scoped state with explicit, server-minted state handles. Builds on SEP-1442 (stateless-by-default) but argues the opt-in stateful path should not exist at all.

Core claims:

• Application state is better served by explicit identifiers
• The mere possibility of session-scoped tools/list forces O(subagents × servers) re-fetches on everyone, even when ~zero servers actually use it
• Session cardinality of exactly-one prevents mixed shared/isolated state (e.g., subagents sharing a cart but isolating browser state)
• Explicit handles are strictly more expressive and make list endpoints cacheable at (deployment, auth) granularity

What changes:

• No session/create, session/destroy, or Mcp-Session-Id header
• tools/list / resources/list / prompts/list MUST NOT depend on per-connection or prior-tool-call state
• Stateful workflows use create_*() -> handle + threaded parameters (guidance, not a protocol construct)

Imported from modelcontextprotocol/transports-wg#25.