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LangChain 1.x Migration Notes

Dependency Conflict with NeMo Guardrails

Problem

The josh/langchain_one_support branch adds support for langchain>=1.0.0, but this creates a dependency conflict:

  • trulens-apps-langgraph requires langchain>=1.0.0
  • trulens-apps-nemo depends on nemoguardrails>=0.9
  • nemoguardrails requires langchain>=0.2.14,<0.4.0 (incompatible with 1.x)

Solution

DEPRECATED and removed trulens-apps-nemo from langchain 1.x branches. The package has been moved to an optional dependency group that is excluded from the lock file until nemoguardrails adds langchain 1.x support.

Changes Made

1. pyproject.toml (root)

  • Removed trulens-apps-nemo from [tool.poetry.group.apps.dependencies]
  • Created separate [tool.poetry.group.nemo] marked as optional = true
  • Added deprecation comment

2. src/apps/nemo/pyproject.toml

  • Updated langchain constraint to match nemoguardrails: langchain = ">=0.2.14,<0.4.0"

3. Makefile

  • Updated env-tests-optional to use --without nemo flag
  • Added explanatory comment

4. src/apps/nemo/DEPRECATED.md

  • Created deprecation notice explaining the incompatibility
  • Documented workarounds for users who need NeMo Guardrails

4. DEVELOPMENT.md

  • Documented the incompatibility and install instructions

Installation Instructions

For langchain 1.x development (current branch):

# Nemo is automatically excluded (it's in an optional group)
poetry install --with dev --with apps
poetry lock  # Now works without conflicts

For nemo development (requires langchain <1.0):

# Switch to a pre-langchain-1.x branch first
git checkout <pre-1.x-branch>
poetry install --with dev --with nemo

For users (when packages are published):

# Default: includes langchain 1.x support, excludes nemo
pip install trulens[langchain,langgraph,llamaindex]

# For nemo (incompatible with langgraph on langchain 1.x):
pip install trulens[langchain,nemo]  # Will use langchain<1.0

CI/CD Impact

Local Development ✅ Documented

  • Developers working on langchain 1.x: poetry install --without nemo
  • Developers working on nemo: work on a pre-1.x branch

When Can We Re-enable Nemo?

Monitor nemoguardrails releases: https://pypi.org/project/nemoguardrails/

When they release a version supporting langchain>=1.0.0:

  1. Update src/apps/nemo/pyproject.toml langchain constraint
  2. Move trulens-apps-nemo back to [tool.poetry.group.apps.dependencies] in root pyproject.toml
  3. Update Makefile env-tests-optional to include nemo again
  4. Run poetry lock to regenerate lockfile

Testing

Run all tests (excluding nemo):

poetry install --with dev --with apps --without nemo
TEST_OPTIONAL=1 make test-unit

Verify OTEL tests with isolation:

poetry install --with dev --with apps --without nemo
TEST_OPTIONAL=1 make test-unit  # Uses pytest-xdist for OTEL test isolation