Middleware packages for express and node

[mattzcarey]

node: node-based transports (streamable-http and sse)
express: common stuff for servers using express.

Motivation and Context

Reduces dependencies in Server package down to the minimum

How Has This Been Tested?

all tests pass and added standalone tests for the new base streamable-http server transport (renamed http.ts for brevity)

Breaking Changes

users will need to import StreamableHTTPServerTransport (and SSE equivalent) from @modelcontextprotocol/node
users should use HTTPServerTransport from @modelcontextprotocol/server for the web standards based transport

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

Removed the fixtures in server package sice they were duplicated from the test-helpers package. We should make custom lint rules to catch this stuff in future.

[changeset-bot]

🦋 Changeset detected

Latest commit: a87c0c5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
@modelcontextprotocol/express	Patch
@modelcontextprotocol/node	Patch
@modelcontextprotocol/test-integration	Patch
@modelcontextprotocol/server	Patch

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[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1336

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1336

commit: a87c0c5