@langchain/core 1.0.0: predict and predictMessages removed, and what else went

@langchain/core 1.0.0 sits under every v1 provider package, so a repository picks it up when it upgrades @langchain/openai, @langchain/anthropic or langchain. What breaks: the pre-LCEL entry points on a chat model, four legacy subpaths, and 24 named exports the 0.3.x declaration files carried and 1.0.0 does not.

What changed

• predict and predictMessages are gone from chat models. Both were deprecated in favour of invoke long before v1. Emendant attributes the calls through the provider packages, so a call on a ChatOpenAI, ChatAnthropic, ChatGoogleGenerativeAI or @langchain/community model is reported.
• Four legacy subpaths were removed. runnables/remote, tracers/initialize, tracers/tracer_langchain_v1 and the two utils/hash utilities, all superseded by LangSmith’s tracing, none with a replacement.
• 24 named exports were removed and two deprecated. Found by diffing the two packages’ declaration files, not the migration guide, which does not list them. Most are content block and *FieldsWith* types in @langchain/core/messages; the rest include getCacheKey, TraceGroup, traceAsGroup, createChatMessageChunkEncoderStream, LoadOptions, SerializableLike, BaseStoreInterface, getRuntimeEnvironmentSync and insecureHash. isToolMessage and isToolMessageChunk gained a deprecation marker.

Before and after

The two pre-LCEL calls on models held in variables, which is what makes the receiver attributable:

import { ChatAnthropic } from '@langchain/anthropic';
import { ChatOpenAI } from '@langchain/openai';

const openai = new ChatOpenAI({ model: 'gpt-4o' });
const anthropic = new ChatAnthropic({ model: 'claude-sonnet-4-5' });

export async function summarise(text: string): Promise<string> {
  return openai.predict(text);
}

export async function reply(messages: never[]) {
  return anthropic.predictMessages(messages);
}

The migration is to invoke, which returns a message. The string-returning call reads its text; the other is a rename:

export async function summarise(text: string): Promise<string> {
  return (await openai.invoke(text)).text;
}

export async function reply(messages: never[]) {
  return anthropic.invoke(messages);
}

A plain rename would typecheck in the second case and silently change the return type in the first, which is why this is an assisted patch rather than a transform.

Migration guidance and its limits

Most findings here are for you to act on rather than for the tool to patch. The predict migration is written only when you name a model provider; read the diff and let your typecheck confirm it followed what invoke returns.

The 24 removed exports and four removed subpaths are report only. The scan’s value is naming the files and names before you upgrade. Whether your code needs a removed content block type at all is a question about your code; several have public replacements in the 1.0 message types, and the entry does not claim to know which. The two deprecations keep working and are reported so you can schedule them.

The langchain package’s own reduction has a page of its own. Behaviour changes in the v1 message model that keep the same names are not in this entry.

What Emendant detects, fixes and verifies

55 changes in @langchain/core 1.0.0. 0 patched by a transform, 1 patched only with a model provider you name, 54 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

2026-09-09.5, sequence 17, signed 9 September 2026

Minimum CLI

emendant@0.1.0

Feed entry

feed/npm/@langchain/core/1.0.0.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/core@1.0.0npm, the published package
• @langchain/core@1.0.0npm registry, the published package
• @langchain/core@0.3.80npm registry, 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.