Pin LangChain version to less than 1.0

[Yuge Zhang (ultmaster)]

LangChain 1.0 has been released. It has broken many of our usages like AgentExecutor, langchain.hub, tool, create_react_agent. Due to the documentation is still under construction, I cannot easily find substitutes that I'm sure will work well.

So let's pin langchain for now and wait for upstream to be more mature.

[Copilot]

Pull Request Overview

This PR pins LangChain-related dependencies to versions less than 1.0 to avoid breaking changes introduced in the LangChain 1.0 release. The PR addresses compatibility issues with features like AgentExecutor, langchain.hub, tool, and create_react_agent by constraining package versions until upstream documentation and migration paths are more mature.

Key Changes:

• Version constraints added to LangChain ecosystem packages
• Import path updated to use langchain_core for callback handlers

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pyproject.toml	Added version constraints <1.0 to langgraph, langchain[openai], and langchain-text-splitters dependencies
agentlightning/tracer/base.py	Updated import path from langchain.callbacks.base to langchain_core.callbacks.base for better compatibility

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[Copilot]

The langchain-community package should also be pinned to <1.0 for consistency with other LangChain packages. LangChain 1.0 includes breaking changes across the ecosystem, and langchain-community is part of this ecosystem.

Suggested change

	"langchain-community",
	"langchain-community<1.0",