Update the MCP integration to MCP Python SDK v2

[anakin87]

https://py.sdk.modelcontextprotocol.io/whats-new/
https://py.sdk.modelcontextprotocol.io/migration/

My initial impression is that this is a big change, so we cannot have an integration that woks with both v1 and v2. To be confirmed.

I recommend waiting some time from now (end of July 2026) to let v2 stabilize.

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Not open for external contributions

[YannikHinteregger]

Hi, just to add a datapoint here: our prod environment broke in relation to this.

We pined mcp-haystack==1.3.0 but since that version has no upper bound on mcp (>=1.8.0) our image builds picked up mcp 2.0.0 immediately. Through that a couple of our containers refused to start up with:

ImportError: cannot import name 'streamablehttp_client' from 'mcp.client.streamable_http'

Fix was easy for us. We just pinned to mcp==1.28.1 for the hotfix and later upgraded to mcp-haystack==1.4.1. Thanks for the quick fix on your side.

Would you be open to a smaller interim PR that just switches to streamable_http_client (the non-deprecated name, available since mcp 1.29) while staying on v1? I understand the full v2 migration isn't open for external contributions, but if the rename would help shrink that diff later, I'd be happy to contribute it. If you'd rather keep it all together in the v2 work, that's fine too. Thanks!

[anakin87]

Hey @YannikHinteregger, thanks for reaching out!

Does switching to streamable_http_client provide any immediate benefit for you? Just to better understand...

[YannikHinteregger]

Honestly, no immediate benefit for us :D we're pinned to mcp 1.x and running fine and other dependencies cap us below 2.0 anyway.

The rename would just get rid of the deprecation warning and maybe shrink your v2 diff a little. I'd just be happy to contribute if it's useful. If it makes more sense to keep it all in the v2 migration, no worries at all.

[anakin87]

I'd wait for the full refactor. Thanks anyway!