Support MCP client session resumption (sessionId reuse) in Python SDK

Description

Summary

The Python MCP SDK currently appears to create a new session whenever a client is instantiated. It would be valuable to support resuming an existing MCP session using a previously issued sessionId, similar to functionality discussed and addressed in the C# SDK (see modelcontextprotocol/csharp-sdk#946).

This would enable persistent and stateful workflows in agent-based systems.

Problem

At present, there does not appear to be a documented way in the Python SDK to:

• Reuse an existing sessionId
• Resume a previously established MCP session
• Control session lifecycle independently of the client object's lifetime

Why This Is Important

• In agent-driven architectures , session continuity allows:
• More efficient orchestration
• Reduced overhead from repeated session initialization

As MCP adoption grows across SDKs (C#, TypeScript, Python), having consistent session lifecycle capabilities improves cross-language parity and developer experience.

References

https://github.com/modelcontextprotocol/csharp-sdk/issues/946

Inizia tracciando il modo in cui Python SDK crea e gestisce le sessioni client, quindi esamina la issue collegata di C# SDK per il contesto della ripresa della sessione. Il lavoro sarà completato quando sarà disponibile un modo supportato per riutilizzare una sessionId emessa in precedenza, riprendere una sessione indipendentemente dal ciclo di vita del client e documentare il comportamento.