LangChain Skills

---
name: ecosystem-primer
description: "INVOKE FIRST for any LangChain / LangGraph / Deep Agents agent building project before consulting other skills or writing any agent code. Required starting point for up to date info on framework selection (LangChain vs LangGraph vs Deep Agents vs hybrid composition), agent patterns, install, environment setup, and which skill to load next."
---

<overview>
LangChain Inc. maintains three layered open-source tools for building agents, plus LangSmith for observability. The stack, top-down:

- **Deep Agents** (top layer, *harness*) — batteries-included toolkit built on LangChain + LangGraph. Ships with planning, file management, subagent spawning, and memory out of the box.
- **LangGraph** (middle layer, *runtime*) — low-level orchestration for durable execution, custom control flow, and stateful workflows. LangChain agents run on top of LangGraph.
- **LangChain** (bottom layer, *framework*) — abstractions for models, tools, and the agent loop. Provider-agnostic, easiest to start with.
- **LangSmith** (cross-cutting) — observability and evaluation platform. Framework-agnostic; always recommended alongside any of the above.

Higher layers depend on lower ones, but you don't need to use lower layers directly. Deep Agents gives you LangGraph's durable execution without writing graph code. LangChain gives you models and tools without managing graph edges.
</overview>

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## Step 1 — Choose Your Tool

<decision-table>

Evaluate these conditions in order and stop at the first match:

1. If the task needs planning, file management across a long session, persistent memory, subagent delegation, or on-demand skills → **Deep Agents**
2. Else, if the task needs custom control flow (deterministic loops, branching logic) → **LangGraph**
3. Else, if it's a single-purpose agent with a fixed set of tools → **LangChain** (`create_agent` function)
4. Else, if it's a pure model call, retrieval pipeline, or simple prompt chain with no agent loop → **LangChain** (direct model / chain)

This is your **layer**. BUT you are not done: later in Step 4, you MUST load the layer-specific skill before writing any agent code.

</decision-table>

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## Tool Profiles

<langchain-profile>

### LangChain — agent framework