> framework-selection

<overview> LangChain, LangGraph, and Deep Agents are **layered**, not competing choices. Each builds on the one below it:

┌─────────────────────────────────────────┐
│              Deep Agents                │  ← highest level: batteries included
│   (planning, memory, skills, files)     │
├─────────────────────────────────────────┤
│               LangGraph                 │  ← orchestration: graphs, loops, state
│    (nodes, edges, state, persistence)   │
├─────────────────────────────────────────┤
│               LangChain                 │  ← foundation: models, tools, chains
│      (models, tools, prompts, RAG)      │
└─────────────────────────────────────────┘

Picking a higher layer does not cut you off from lower layers — you can use LangGraph graphs inside Deep Agents, and LangChain primitives inside both.

This skill should be loaded at the top of any project before selecting other skills or writing agent code. The framework you choose dictates which other skills to invoke next.

</overview>

---

Decision Guide

<decision-table>

Answer these questions in order:

Question	Yes →	No →
Does the task require breaking work into sub-tasks, managing files across a long session, persistent memory, or loading on-demand skills?	Deep Agents	↓
Does the task require complex control flow — loops, dynamic branching, parallel workers, human-in-the-loop, or custom state?	LangGraph	↓
Is this a single-purpose agent that takes input, runs tools, and returns a result?	LangChain (create_agent)	↓
Is this a pure model call, chain, or retrieval pipeline with no agent loop?	LangChain (LCEL / chain)	—

</decision-table>

---

Framework Profiles

<langchain-profile>

LangChain — Use when the task is focused and self-contained

Best for:

• Single-purpose agents that use a fixed set of tools
• RAG pipelines and document Q&A
• Model calls, prompt templates, output parsing
• Quick prototypes where agent logic is simple

Not ideal when:

• The agent needs to plan across many steps
• State needs to persist across multiple sessions
• Control flow is conditional or iterative

Skills to invoke next: langchain-models, langchain-rag, langchain-middleware

</langchain-profile> <langgraph-profile>

LangGraph — Use when you need to own the control flow

Best for:

• Agents with branching logic or loops (e.g. retry-until-correct, reflection)
• Multi-step workflows where different paths depend on intermediate results
• Human-in-the-loop approval at specific steps
• Parallel fan-out / fan-in (map-reduce patterns)
• Persistent state across invocations within a session

Not ideal when:

• You want planning, file management, and subagent delegation handled for you (use Deep Agents instead)
• The workflow is straightforward enough for a simple agent

Skills to invoke next: langgraph-fundamentals, langgraph-human-in-the-loop, langgraph-persistence

</langgraph-profile> <deep-agents-profile>

Deep Agents — Use when the task is open-ended and multi-dimensional

Best for:

• Long-running tasks that require breaking work into a todo list
• Agents that need to read, write, and manage files across a session
• Delegating subtasks to specialized subagents
• Loading domain-specific skills on demand
• Persistent memory that survives across multiple sessions

Not ideal when:

• The task is simple enough for a single-purpose agent
• You need precise, hand-crafted control over every graph edge (use LangGraph directly)

Middleware — built-in and extensible:

Deep Agents ships with a built-in middleware layer out of the box — you configure it, you don't implement it. The following come pre-wired; you can also add your own on top:

Middleware	What it provides	Always on?
TodoListMiddleware	write_todos tool — agent plans and tracks multi-step tasks	✓
FilesystemMiddleware	ls, read_file, write_file, edit_file, glob, grep tools	✓
SubAgentMiddleware	task tool — delegate work to named subagents	✓
SkillsMiddleware	Load SKILL.md files on demand from a skills directory	Opt-in
MemoryMiddleware	Long-term memory across sessions via a Store instance	Opt-in
HumanInTheLoopMiddleware	Interrupt and request human approval before sensitive tool calls	Opt-in

Skills to invoke next: deep-agents-core, deep-agents-memory, deep-agents-orchestration

</deep-agents-profile>

---

Mixing Layers

<mixing-layers> Because the frameworks are layered, they can be combined in the same project. The most common pattern is using Deep Agents as the top-level orchestrator while dropping down to LangGraph for specialized subagents.

When to mix

Scenario	Recommended pattern
Main agent needs planning + memory, but one subtask requires precise graph control	Deep Agents orchestrator → LangGraph subagent
Specialized pipeline (e.g. RAG, reflection loop) is called by a broader agent	LangGraph graph wrapped as a tool or subagent
High-level coordination but low-level graph for a specific domain	Deep Agents + LangGraph compiled graph as a subagent

How it works in practice

A LangGraph compiled graph can be registered as a subagent inside Deep Agents. This means you can build a tightly-controlled LangGraph workflow (e.g. a retrieval-and-verify loop) and hand it off to the Deep Agents task tool as a named subagent — the Deep Agents orchestrator delegates to it without caring about its internal graph structure.

LangChain tools, chains, and retrievers can be used freely inside both LangGraph nodes and Deep Agents tools — they are the shared building blocks at every level.

</mixing-layers>

---

Quick Reference

<quick-reference>

	LangChain	LangGraph	Deep Agents
Control flow	Fixed (tool loop)	Custom (graph)	Managed (middleware)
Middleware layer	Callbacks only	✗ None	✓ Explicit, configurable
Planning	✗	Manual	✓ TodoListMiddleware
File management	✗	Manual	✓ FilesystemMiddleware
Persistent memory	✗	With checkpointer	✓ MemoryMiddleware
Subagent delegation	✗	Manual	✓ SubAgentMiddleware
On-demand skills	✗	✗	✓ SkillsMiddleware
Human-in-the-loop	✗	Manual interrupt	✓ HumanInTheLoopMiddleware
Custom graph edges	✗	✓ Full control	Limited
Setup complexity	Low	Medium	Low
Flexibility	Medium	High	Medium

Middleware is a concept specific to LangChain (callbacks) and Deep Agents (explicit middleware layer). LangGraph has no middleware — you wire behavior directly into nodes and edges.

</quick-reference>