deepagents-architecture

Deep Agents Architecture Decisions

When to Use Deep Agents

Use Deep Agents When You Need:

• Long-horizon tasks - Complex workflows spanning dozens of tool calls
• Planning capabilities - Task decomposition before execution
• Filesystem operations - Reading, writing, and editing files
• Subagent delegation - Isolated task execution with separate context windows
• Persistent memory - Long-term storage across conversations
• Human-in-the-loop - Approval gates for sensitive operations
• Context management - Auto-summarization for long conversations

Consider Alternatives When:

Scenario	Alternative	Why
Single LLM call	Direct API call	Deep Agents overhead not justified
Simple RAG pipeline	LangChain LCEL	Simpler abstraction
Custom graph control flow	LangGraph directly	More flexibility
No file operations needed	create_react_agent	Lighter weight
Stateless tool use	Function calling	No middleware needed

Backend Selection

Backend Comparison

Backend	Persistence	Use Case	Requires
StateBackend	Ephemeral (per-thread)	Working files, temp data	Nothing (default)
FilesystemBackend	Disk	Local development, real files	root_dir path
StoreBackend	Cross-thread	User preferences, knowledge bases	LangGraph store
CompositeBackend	Mixed	Hybrid memory patterns	Multiple backends

Backend Decision Tree

Need real disk access?
├─ Yes → FilesystemBackend(root_dir="/path")
└─ No
   └─ Need persistence across conversations?
      ├─ Yes → Need mixed ephemeral + persistent?
      │  ├─ Yes → CompositeBackend
      │  └─ No → StoreBackend
      └─ No → StateBackend (default)

CompositeBackend Routing

Route different paths to different storage backends:

from deepagents import create_deep_agent
from deepagents.backends import CompositeBackend, StateBackend, StoreBackend

agent = create_deep_agent(
    backend=CompositeBackend(
        default=StateBackend(),  # Working files (ephemeral)
        routes={
            "/memories/": StoreBackend(store=store),    # Persistent
            "/preferences/": StoreBackend(store=store), # Persistent
        },
    ),
)