MCP SSE server transport support

[xierenyuan]

There's a lot of stock mcp internally and the sse protocol is still in use Streamable HTTP is great but it's going to take a while to get it right If it's possible I can propose a pr to support the sse protocol.

[seratch]

Thanks for sharing this feedback. I hear there could be still SSE needs while the transport is already deprecated.

If you're willing to work on the feature addition, we're happy to review and have the change. You'll touch these files:

• packages/agents-core/src/shims/mcp-server/*
• packages/agents-core/src/mcp.ts
• add one more example to examples/mcp/