langchain-mcp-adapters is archived: what changes for Sume

If your LangChain agent loads Sume's tools through langchain-mcp-adapters, the package is now read-only: the repository was archived on September 17, 2026, and its README tells users to migrate to langchain[mcp], where the tools live under the langchain.mcp namespace. Nothing about Sume's side changes: the hosted server is still https://mcp.sume.com/mcp, and the credential is still either OAuth or a Sume API key. What you re-check is your pin, your auth wiring and your paid-call handling.

LangChain's side comes from the archived repository, its release list and the LangChain MCP docs. Sume's side comes from the MCP quickstart, OAuth and API keys, tools and gates and jobs and results. All were read on 2026-10-01.

What did LangChain announce, and what did it not?

The archive banner says the repository is no longer actively maintained, and the README points to the in-tree replacement. The last adapter releases were 0.3.2 on August 6, 2026, which capped mcp below 2.0.0 to prevent import failures, 0.3.1 on July 27, and 0.3.0 on June 10, which moved to the non-deprecated streamable HTTP client and surfaced MCP tool execution errors as failed tool output.

That last point matters for Sume. Sume tools refuse bad calls with named codes such as insufficient_scope, so make sure the agent sees those as failed tool output. How the new namespace treats errors is a thing to test, not assume.

What should I re-test on the Sume side?

First, the handshake. Sume's hosted server negotiates the 2025-03-26, 2025-06-18 and 2025-11-25 protocol revisions, so whichever MCP client library the new package pulls in, run a tools_list call before anything paid. mcp_health is also read-only and reports the auth source, which tells you whether your header arrived.

Second, the credential. An API key sent as a bearer or x-api-key header sees the full tool set. An OAuth token defaults to mcp:read, so paid tools such as generate_image return insufficient_scope until the user turns Write on at consent. For an unattended LangChain job, an API key avoids the consent step.

Third, paid calls. Every write or paid Sume tool needs an idempotency_key. If your wrapper retries a failed tool, reuse the same key so a retry returns the original job. Wait on long renders with jobs_wait, which holds at most 55 seconds per call; on wait_slice_expired, call it again with the same ids rather than resubmitting.

Limits of this post

This post does not reproduce LangChain's new API surface, because the archived README and docs are the only sources read and they describe the move at a high level. Use LangChain's own migration guide for exact class names, and keep one smoke test that lists Sume's tools and runs one dry-run cost preview before you cut over.