MCP Streamable HTTP Transport

[dt-atmosic]

What feature do you want to see added?

Version 0.11.0 of https://github.com/modelcontextprotocol/java-sdk has been released. It now includes HttpServletStreamableServerTransportProvider, which seems to work quite well. It also avoids all the tool call timeout issues associated with clients that start a new SSE session but don't go through the initialization steps.

Would you please add a streamable version of Endpoint.java?

Upstream changes

No response

Are you interested in contributing this feature?

Yes, I can perform this port and/or test it.

[olamy]

@dt-atmosic I was planning to implement as well :)
Do you want to take it? I'm happy to help with review and testing.
I wonder if we need to keep sse implementation?

[dt-atmosic]

I have an implementation of streamable HTTP working in the plugin today, but I'm getting stuck on the unit test. There seems to be a disagreement in modelcontextprotocol/java-sdk 0.11.0 about the protocol version between its streaming client and server.

My intent was to make this work along with the sse transport - the only real trick seems to be making sure that there is only one RootAction. Perhaps I will place that on the streaming side so it will be trivial to just remove Endpoint.java in the future.

Anyway, I'll put what I have up on a fork and solicit your input.

[dt-atmosic]

This is what I have so far:
dt-atmosic@6d11a33

[olamy]

@dt-atmosic Thanks I will have a look! would you mind make a PR (draft mode)
Maybe make a branch in your fork for it?
Thanks a lot.

[dt-atmosic]

Done: #25
And done: https://github.com/dt-atmosic/mcp-server-plugin/tree/streamable_http_transport

[olamy]

@dt-atmosic Thanks! Great work!
I had a look and fixed a few little things to get it working along with SSE here olamy@f32604d

Actually, the new streamable endpoint was not used :)
Not easy to use multiple RootAction
Please note you must now use: "url": "http://localhost:8080/jenkins/mcp-server/streamable" (I was thinking about being more explicit about the protocol in the URL. wdyt?)

I have done manual testing, and it looks great.
I suspect test failures are a bit of flakiness due to the async nature (but need to dig into this a bit more)

I can see a lot of duplicated code between Now the question is more about do we keep sse endpoint or just provide streamable (I would say yes, but I'm not a maintainer here :))

@topikachu WDYT

[olamy]

@dt-atmosic unit tests now fixed see PR #26
I can make a PR against your branch to get everything in #25 or we can use #26
let me know what do you prefer. We might need to implement and add some tests for streamable and authz (as currently authz is ignored)

[olamy]

@dt-atmosic I have added user management. I made a PR against your branch so you can see the differences. dt-atmosic#1

[hellosaumil]

I think standard url used for Streamable HTTP is /mcp, I'd suggest if we can use that stay consistent with other MCP servers. Thank you.

[olamy]

I think standard url used for Streamable HTTP is /mcp, I'd suggest if we can use that stay consistent with other MCP servers. Thank you.

sounds good and more usual. But frankly no real strong opinion :) (usually the RootAction handle uri path related to plugn id but not sure if it's really mandatory though)

[batmat]

standard url used for Streamable HTTP is /mcp

@hellosaumil while I would personally see the "beauty" of a single endpoint like /mcp and then content/protocol negotiation happening on this single one (streamable), I also know how hard it can be sometimes to get things working.

And having, say, /mcp/sse, then /mcp/streamable or whatever, while less "clean", would allow one to be sure that when they're configuring Goose, Copilot, Amazon Q, Claude etc., they're hitting the endpoint with protocol/transport layer expectation that are crystal clear 😅.

Because, let's face it, MCP is 9 months old, so it's a-changin, and I'd rather reduce the amount of time we waste spend configuring all these various agents out there by being more explicit (at least until the dust kinda starts to settle a bit on this subject).

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Apart from GitHub, I couldn't find another example (Atlassian only has SSE yet currently, AFAICT, but given there current SSE URL is https://mcp.atlassian.com/v1/sse, I could well assume streamable will be something like https://mcp.atlassian.com/v1/streamable or something, given the mcp part is in the subdomain already).

[topikachu]

implemented by #28