Expose create_mcp_http_client and McpHttpClientFactory as public API (2.0 made them private-only)

Summary

Customizing the HTTP client for streamable_http_client (custom headers, auth, timeout, proxy, etc.) is a common and legitimate need, but as of 2.0.0 the only supported way to build a conforming client is through helpers that live in the private module mcp.shared._httpx_utils. Users are therefore forced to depend on a private API.

What changed in 2.0

In 1.x, streamable_http_client accepted convenience kwargs directly:

streamable_http_client(url, headers=..., timeout=..., sse_read_timeout=..., auth=...)

2.0 (via #2972, which replaced httpx/httpx-sse with httpx2) removed those kwargs. The signature is now:

async def streamable_http_client(
    url: str,
    *,
    http_client: httpx2.AsyncClient | None = None,
    terminate_on_close: bool = True,
) -> ...

So the only way to pass custom headers/auth/timeout is to build an httpx2.AsyncClient yourself and pass it as http_client=. The standardized factory for doing so is create_mcp_http_client — but it is only available at the private path:

from mcp.shared._httpx_utils import create_mcp_http_client  # private module

The same applies to McpHttpClientFactory: in 1.x it was importable from the public mcp.client.streamable_http, but in 2.0 it is defined in mcp.shared._httpx_utils and is no longer re-exported from any public module.

Why this is a problem

• "Connect to an MCP server that requires auth headers / a custom timeout / a proxy" is a standard use case, not an edge case.
• The leading underscore on mcp.shared._httpx_utils signals "private, may change without notice", so every downstream project that needs a custom client has to take on that fragility.
• It's inconsistent: the consumption side (streamable_http_client(url, http_client=...)) is public, but the construction side (create_mcp_http_client, McpHttpClientFactory) is private.

Suggestion

Re-export create_mcp_http_client and McpHttpClientFactory from a public module — e.g. mcp.client.streamable_http (where McpHttpClientFactory used to live) or mcp.shared — so building a custom HTTP client does not require importing a private module.

(Related: because the HTTP layer now uses httpx2, a short note in the migration docs on how to build/pass a custom http_client would also help.)

先檢查 mcp/shared/_httpx_utils.py 和 mcp/client/streamable_http.py，以比較目前的定義和公開匯出。從公開模組重新匯出 create_mcp_http_client 和 McpHttpClientFactory，並考慮 issue 中提到的遷移文件註記。完成的標準是使用者可以建構並傳入自訂用戶端，而不必匯入私有模組。