LangChain 1.0 for JavaScript: the legacy modules moved to @langchain/classic

LangChain 1.0 cut langchain down to the agent building blocks and published the rest as @langchain/classic. Imports of chains, legacy agents, retrievers, memory, document loaders, output parsers or stores from a langchain/... subpath stop resolving on upgrade. The code behind them did not change; the package name in front of the subpath did.

What changed

• 85 subpaths moved to @langchain/classic, same names. langchain/agents, langchain/chains, langchain/retrievers/*, langchain/memory, langchain/document_loaders/*, langchain/output_parsers, langchain/text_splitter, langchain/tools/*, langchain/stores/*, langchain/vectorstores/memory, langchain/evaluation, langchain/smith, the experimental tree and the util helpers. The map was derived by comparing the exports of langchain 0.3.36 with 1.0.1 and keeping every subpath @langchain/classic 1.0.0 publishes.
• Ten subpaths stayed. langchain, langchain/hub and langchain/chat_models/universal are unaffected.
• One subpath was removed. langchain/runnables/remote and its RemoteRunnable have no replacement in the v1 packages.

Before and after

A v0 program built from parts that moved:

import { createRetrievalChain } from 'langchain/chains/retrieval';
import { EnsembleRetriever } from 'langchain/retrievers/ensemble';
import { RecursiveCharacterTextSplitter } from 'langchain/text_splitter';
import { StructuredOutputParser } from 'langchain/output_parsers';

After npx emendant fix, only the package in front of each subpath changes:

import { createRetrievalChain } from '@langchain/classic/chains/retrieval';
import { EnsembleRetriever } from '@langchain/classic/retrievers/ensemble';
import { RecursiveCharacterTextSplitter } from '@langchain/classic/text_splitter';
import { StructuredOutputParser } from '@langchain/classic/output_parsers';

There is no after for RemoteRunnable.

Migration guidance and its limits

Apply the patch, then install @langchain/classic. The patch rewrites specifiers and does not touch your manifest, so until the package is installed the verification run reports it as failing. Add the dependency and run the fix again.

A langchain/... subpath the map does not name went somewhere other than @langchain/classic, or was never public, and Emendant reports nothing for it rather than guessing. langchain/runnables/remote is report only. The new agent API in langchain 1.0 is outside this page: a clean scan says your imports still resolve, not that your agents behave as before.

What Emendant detects, fixes and verifies

2 changes in langchain 1.0.1. 1 patched by a transform, 0 patched only with a model provider you name, 1 report only. Every patch is proved in a copy of your repository before it is offered, and its header names the checks that passed. This table is generated from the feed entry, so it cannot claim more than the entry does.

emendant explain <change-id> prints any row's entry, guidance and sources at the terminal.

Coverage

Snapshot

2026-08-28.1, sequence 11, signed 28 August 2026

Minimum CLI

emendant@0.1.0

Feed entry

feed/npm/langchain/1.0.1.json

emendant feed status shows the snapshot your machine holds, and emendant feed update fetches the latest.

Primary sources

Every claim above was checked against these, each pinned to the release rather than to a default branch.

• Langchain v1langchain-ai/docs at commit bff16d7f
• @langchain/classic@1.0.0npm, the published package

Scan your repository

Runs locally, reads your lockfile and source, sends nothing anywhere.

npx emendant scan

Then npx emendant fix writes the patches the table says exist. The getting started guide covers the flags and the patch grades.