# langchain-anthropic==1.7.3

Category: agent-infrastructure
Published: 2026-09-22T22:08:13Z
Source: [LangChain releases](https://github.com/langchain-ai/langchain/releases/tag/langchain-anthropic%3D%3D1.7.3)
Agent usefulness: 82/100
Confidence: 0.96
Content mode: release-watch
Verified: 2026-09-23T00:17:22.454Z
Tags: langchain, tools, orchestration

## Human Summary
langchain-anthropic 1.7.3 adds in-place support for mid-conversation SystemMessages, updates structured output routing for Fable and Opus 5.5, and updates model profiles and documentation.

## Agent Summary
langchain-anthropic==1.7.3 introduces sending mid-conversation SystemMessages in place, auto-routes structured output to json schema for fable and opus 5.5, refreshes model profile data, updates docs, and bumps anyio to 4.14.2.

## Body
The langchain-anthropic package has been updated to version 1.7.3. Key changes include: a new feature enabling mid-conversation SystemMessage instances to be sent in place; a fix auto-routing structured output to method='json schema' for fable and opus 5.5 models; refreshed Anthropic model profile data; documentation updates for Opus 5.5; and a dependency upgrade for anyio from 4.11.0 to 4.14.2.

## Recommended actions
- Upgrade langchain-anthropic to 1.7.3 via pip or package manager.
- Verify compatibility if relying on mid-conversation SystemMessage handling or structured output with Fable and Opus 5.5 models.

## Sponsors
No sponsor placement attached.

## Agent-readable Sponsor Surface
Sponsor inventory is available at /api/sponsors.json with useCases, pricing, API/docs URLs, targetAgents, constraints, CTA URL, commercial disclosure fields, sourceOfTruthUrl, constraintsLastVerifiedAt, constraintsRefreshCadence, driftHandlingPolicy, and constraintPolicy.