---

name: langchain description: "Work on the LangChain Python monorepo: package routing, core primitives, v1 agents and middleware, classic APIs, partner integrations, standard tests, model profiles, and safe validation workflows." disable-model-invocation: true metadata: disco-role: operating license: MIT

LangChain Python Monorepo

Use this skill when a task targets the LangChain Python repository, its package-local development workflow, or one of its maintained Python packages.

Start Here

1. Identify the package and workflow with repository-map.md.
2. Use the sub-skill that owns the change instead of scanning the whole monorepo.
3. Follow development-commands.md for package-local uv, pytest, lint, type, import, and version checks.
4. Use troubleshooting.md for environment, import, optional dependency, integration-test, and source-layout failures.
5. Check repo-provenance.md when deciding whether this skill is stale relative to the current checkout.

Route by Task

• Monorepo navigation, package metadata, validation commands, public API guardrails, PR conventions, and docs/model-reference rules: use monorepo-development.
• langchain-core primitives such as runnables, messages, prompts, tools, documents, embeddings, vector stores, model interfaces, callbacks, parsers, serialization, and deprecation utilities: use core-primitives.
• Actively maintained langchain v1 APIs such as init_chat_model, create_agent, structured output, tools, middleware, embeddings, provider routing, and agent runtime customization: use agents-and-middleware.
• langchain-classic chains, retrievers, document loaders/transformers, memory, indexes, classic agents, evaluation, and legacy maintenance or migration: use classic-chains.
• Partner packages under libs/partners, provider SDK dependencies, credentials, unit/integration test split, cassettes, vector-store services, and provider model profile data: use integrations.
• langchain-tests, native verification selection, pytest marker/snapshot safety, model-profile CLI internals, and safe test/profile command planning: use testing-and-profiles.

Package Boundaries

• libs/core publishes langchain-core, the stable abstraction layer used by other packages.
• libs/langchain_v1 publishes langchain, the actively maintained high-level package.
• libs/langchain publishes langchain-classic, a legacy compatibility package; avoid new feature work there unless explicitly requested.
• libs/text-splitters publishes langchain-text-splitters, focused on chunking documents and text.
• libs/partners/<provider> publish maintained provider integrations such as OpenAI, Anthropic, Ollama, Qdrant, Chroma, DeepSeek, Fireworks, Groq, Hugging Face, MistralAI, Nomic, Perplexity, OpenRouter, xAI, and Exa.
• libs/standard-tests publishes langchain-tests, shared conformance tests for integrations.
• libs/model-profiles contains the model profile refresh CLI and provider profile tooling.

Default Development Workflow

Run commands from the owning package directory unless a package reference says otherwise:

cd libs/<package>
uv sync --group test
uv run --group test pytest tests/unit_tests/path/to/test_file.py
make lint_package
make type

Use narrower commands first. Add --group lint, --group typing, --group test_integration, or --all-groups only when the package metadata and task require those dependencies. Do not use pip, poetry, conda, or ad-hoc virtual environments for normal LangChain development.

Safety and Validation

• Preserve public function/class signatures, argument order, names, defaults, and exported symbols unless the user accepts a breaking change.
• Add deterministic unit tests for bug fixes and feature changes; avoid network, credentials, provider services, or long-running checks by default.
• Use integration tests only when explicitly requested and credentials/services are available.
• For provider model examples in docs, verify current generally available model IDs against provider docs before updating examples.
• Use bundled scripts only as local helpers; they are read-only smoke/inspection utilities and do not replace package test suites.

Bundled References and Scripts

• Repository map gives the capability-to-package map and sub-skill ownership.
• Development commands gives command patterns and validation escalation rules.
• Troubleshooting covers cross-cutting failures and recovery decisions.
• Repo provenance records the source snapshot and evidence paths.
• Skill health check validates generated skill links and common leakage patterns.