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Implements agents using Deep Agents. Use when building agents with create_deep_agent, configuring backends, defining subagents, adding middleware, or setting...
---
name: deepagents-implementation
description: Implements agents using Deep Agents. Use when building agents with create_deep_agent, configuring backends, defining subagents, adding middleware, or setting up human-in-the-loop workflows.
---
# Deep Agents Implementation
## Core Concepts
Deep Agents provides a batteries-included agent harness built on LangGraph:
- **`create_deep_agent`**: Factory function that creates a configured agent
- **Middleware**: Injected capabilities (filesystem, todos, subagents, summarization)
- **Backends**: Pluggable file storage (state, filesystem, store, composite)
- **Subagents**: Isolated task execution via the `task` tool
The agent returned is a compiled LangGraph `StateGraph`, compatible with streaming, checkpointing, and LangGraph Studio.
## Essential Imports
```python
# Core
from deepagents import create_deep_agent
# Subagents
from deepagents import CompiledSubAgent
# Backends
from deepagents.backends import (
StateBackend, # Ephemeral (default)
FilesystemBackend, # Real disk
StoreBackend, # Persistent cross-thread
CompositeBackend, # Route paths to backends
)
# LangGraph (for checkpointing, store, streaming)
from langgraph.checkpoint.memory import InMemorySaver
from langgraph.checkpoint.postgres import PostgresSaver
from langgraph.store.memory import InMemoryStore
# LangChain (for custom models, tools)
from langchain.chat_models import init_chat_model
from langchain_core.tools import tool
```
## Basic Usage
### Minimal Agent
```python
from deepagents import create_deep_agent
# Uses Claude Sonnet 4 by default
agent = create_deep_agent()
result = agent.invoke({"messages": [{"role": "user", "content": "Hello!"}]})
```
### With Custom Tools
```python
from langchain_core.tools import tool
from deepagents import create_deep_agent
@tool
def web_search(query: str) -> str:
"""Search the web for information."""
return tavily_client.search(query)
agent = create_deep_agent(
tools=[web_search],
system_prompt="You are a research assistant. Search the web to answer questions.",
)
result = agent.invoke({"messages": [{"role": "user", "content": "What is LangGraph?"}]})
```
### With Custom Model
```python
from langchain.chat_models import init_chat_model
from deepagents import create_deep_agent
# OpenAI
model = init_chat_model("openai:gpt-4o")
# Or Anthropic with custom settings
from langchain_anthropic import ChatAnthropic
model = ChatAnthropic(model_name="claude-sonnet-4-5-20250929", max_tokens=8192)
agent = create_deep_agent(model=model)
```
### With Checkpointing (Persistence)
```python
from langgraph.checkpoint.memory import InMemorySaver
from deepagents import create_deep_agent
agent = create_deep_agent(checkpointer=InMemorySaver())
# Must provide thread_id with checkpointer
config = {"configurable": {"thread_id": "user-123"}}
result = agent.invoke({"messages": [...]}, config)
# Resume conversation
result = agent.invoke({"messages": [{"role": "user", "content": "Follow up"}]}, config)
```
## Streaming
The agent supports all LangGraph stream modes.
### Stream Updates
```python
for chunk in agent.stream(
{"messages": [{"role": "user", "content": "Write a report"}]},
stream_mode="updates"
):
print(chunk) # {"node_name": {"key": "value"}}
```
### Stream Messages (Token-by-Token)
```python
for chunk in agent.stream(
{"messages": [{"role": "user", "content": "Explain quantum computing"}]},
stream_mode="messages"
):
# Real-time token streaming
print(chunk.content, end="", flush=True)
```
### Async Streaming
```python
async for chunk in agent.astream(
{"messages": [...]},
stream_mode="updates"
):
print(chunk)
```
### Multiple Stream Modes
```python
for mode, chunk in agent.stream(
{"messages": [...]},
stream_mode=["updates", "messages"]
):
if mode == "messages":
print("Token:", chunk.content)
else:
print("Update:", chunk)
```
## Backend Configuration
### StateBackend (Default - Ephemeral)
Files stored in agent state, persist within thread only.
```python
# Implicit - this is the default
agent = create_deep_agent()
# Explicit
from deepagents.backends import StateBackend
agent = create_deep_agent(backend=lambda rt: StateBackend(rt))
```
### FilesystemBackend (Real Disk)
Read/write actual files on disk. Enables `execute` tool for shell commands.
```python
from deepagents.backends import FilesystemBackend
agent = create_deep_agent(
backend=FilesystemBackend(root_dir="/path/to/project"),
)
```
### StoreBackend (Persistent Cross-Thread)
Uses LangGraph Store for persistence across conversations.
```python
from langgraph.store.memory import InMemoryStore
from deepagents.backends import StoreBackend
store = InMemoryStore()
agent = create_deep_agent(
backend=lambda rt: StoreBackend(rt),
store=store, # Required for StoreBackend
)
```
### CompositeBackend (Hybrid Routing)
Route different paths to different backends.
```python
from langgraph.store.memory import InMemoryStore
from deepagents.backends import CompositeBackend, StateBackend, StoreBackend
store = InMemoryStore()
agent = create_deep_agent(
backend=CompositeBackend(
default=StateBackend(), # /workspace/* → ephemeral
routes={
"/memories/": StoreBackend(store=store), # persistent
"/preferences/": StoreBackend(store=store), # persistent
},
),
store=store,
)
# Files under /memories/ persist across all conversations
# Files under /workspace/ are ephemeral per-thread
```
## Subagents
### Using the Default General-Purpose Agent
By default, a `general-purpose` subagent is available with all main agent tools.
```python
agent = create_deep_agent(tools=[web_search])
# The agent can now delegate via the `task` tool:
# task(subagent_type="general-purpose", prompt="Research topic X in depth")
```
### Defining Custom Subagents
```python
from deepagents import create_deep_agent
research_agent = {
"name": "researcher",
"description": "Conducts deep research on complex topics with web search",
"system_prompt": """You are an expert researcher.
Search thoroughly, cross-reference sources, and synthesize findings.""",
"tools": [web_search, document_reader],
}
code_agent = {
"name": "coder",
"description": "Writes, reviews, and debugs code",
"system_prompt": "You are an expert programmer. Write clean, tested code.",
"tools": [code_executor, linter],
"model": "openai:gpt-4o", # Optional: different model per subagent
}
agent = create_deep_agent(
subagents=[research_agent, code_agent],
system_prompt="Delegate research to the researcher and coding to the coder.",
)
```
### Pre-compiled LangGraph Subagents
Use existing LangGraph graphs as subagents.
```python
from deepagents import CompiledSubAgent, create_deep_agent
from langgraph.prebuilt import create_react_agent
# Existing graph
custom_graph = create_react_agent(
model="anthropic:claude-sonnet-4-5-20250929",
tools=[specialized_tool],
prompt="Custom workflow instructions",
)
agent = create_deep_agent(
subagents=[CompiledSubAgent(
name="custom-workflow",
description="Runs my specialized analysis workflow",
runnable=custom_graph,
)]
)
```
### Subagent with Custom Middleware
```python
from langchain.agents.middleware import AgentMiddleware
class LoggingMiddleware(AgentMiddleware):
def transform_response(self, response):
print(f"Subagent response: {response}")
return response
agent_spec = {
"name": "logged-agent",
"description": "Agent with extra logging",
"system_prompt": "You are helpful.",
"tools": [],
"middleware": [LoggingMiddleware()], # Added after default middleware
}
```
## Human-in-the-Loop
### Basic Interrupt Configuration
Pause execution before specific tools for human approval.
```python
from deepagents import create_deep_agent
agent = create_deep_agent(
tools=[send_email, delete_file, web_search],
interrupt_on={
"send_email": True, # Simple interrupt
"delete_file": True, # Require approval before delete
# web_search not listed - runs without approval
},
checkpointer=checkpointer, # Required for interrupts
)
```
### Interrupt with Options
```python
agent = create_deep_agent(
tools=[send_email],
interrupt_on={
"send_email": {
"allowed_decisions": ["approve", "edit", "reject"]
},
},
checkpointer=checkpointer,
)
# Invoke - will pause at send_email
config = {"configurable": {"thread_id": "user-123"}}
result = agent.invoke({"messages": [...]}, config)
# Check state
state = agent.get_state(config)
if state.next: # Has pending interrupt
# Resume with approval
from langgraph.types import Command
agent.invoke(Command(resume={"approved": True}), config)
# Or resume with edit
agent.invoke(Command(resume={"edited_args": {"to": "new@email.com"}}), config)
# Or reject
agent.invoke(Command(resume={"rejected": True}), config)
```
### Interrupt on Subagent Tools
```python
# Interrupts apply to subagents too
agent = create_deep_agent(
subagents=[research_agent],
interrupt_on={
"web_search": True, # Interrupt even when subagent calls it
},
checkpointer=checkpointer,
)
```
## Custom Middleware
### Middleware Structure
```python
from langchain.agents.middleware.types import (
AgentMiddleware,
ModelRequest,
ModelResponse,
)
from langchain_core.tools import tool
class MyMiddleware(AgentMiddleware):
# Tools to inject
tools = []
# System prompt content to inject
system_prompt = ""
def transform_request(self, request: ModelRequest) -> ModelRequest:
"""Modify request before sending to model."""
return request
def transform_response(self, response: ModelResponse) -> ModelResponse:
"""Modify response after receiving from model."""
return response
```
### Injecting Tools via Middleware
```python
from langchain_core.tools import tool
@tool
def get_current_time() -> str:
"""Get the current time."""
from datetime import datetime
return datetime.now().isoformat()
class TimeMiddleware(AgentMiddleware):
tools = [get_current_time]
system_prompt = "You have access to get_current_time for time-sensitive tasks."
agent = create_deep_agent(middleware=[TimeMiddleware()])
```
### Context Injection Middleware
```python
class UserContextMiddleware(AgentMiddleware):
def __init__(self, user_preferences: dict):
self.user_preferences = user_preferences
@property
def system_prompt(self):
return f"User preferences: {self.user_preferences}"
agent = create_deep_agent(
middleware=[UserContextMiddleware({"theme": "dark", "language": "en"})]
)
```
### Response Logging Middleware
```python
import logging
class LoggingMiddleware(AgentMiddleware):
def transform_response(self, response: ModelResponse) -> ModelResponse:
logging.info(f"Agent response: {response.messages[-1].content[:100]}...")
return response
agent = create_deep_agent(middleware=[LoggingMiddleware()])
```
## MCP Tool Integration
Connect MCP (Model Context Protocol) servers to provide additional tools.
```python
from langchain_mcp_adapters.client import MultiServerMCPClient
from deepagents import create_deep_agent
async def main():
mcp_client = MultiServerMCPClient({
"filesystem": {
"command": "npx",
"args": ["-y", "@modelcontextprotocol/server-filesystem", "/path"],
},
"github": {
"command": "npx",
"args": ["-y", "@modelcontextprotocol/server-github"],
"env": {"GITHUB_TOKEN": os.environ["GITHUB_TOKEN"]},
},
})
mcp_tools = await mcp_client.get_tools()
agent = create_deep_agent(tools=mcp_tools)
async for chunk in agent.astream(
{"messages": [{"role": "user", "content": "List my repos"}]}
):
print(chunk)
```
## Implementation gates
Use this **sequenced** table for setups that touch **real disk, human interrupts, persistence, or MCP subprocesses** (skip for minimal `create_deep_agent()` smoke tests).
| Step | Pass condition |
|------|----------------|
| 1 | **FilesystemBackend or `execute`:** `root_dir` is deliberately scoped (not an accidental home or filesystem root); smoke-test in a disposable directory before trusting production paths. |
| 2 | **`interrupt_on` / resume:** A `checkpointer` is configured; every `invoke` / `astream` that may interrupt includes `config` with `configurable["thread_id"]`; after a pause, `agent.get_state(config)` shows pending interrupt state before `Command(resume=...)`, and the resume payload matches tool options (e.g. `allowed_decisions`) when set. |
| 3 | **Store, PostgreSQL saver, MCP:** Credentials come from environment or a secret manager, not committed source; MCP `command` / `args` / required `env` keys match what the deployment host actually provides (e.g. `npx`, tokens). |
## Additional References
For detailed reference documentation, see:
- **[Built-in Tools Reference](references/tools.md)** - Complete list of tools available on every agent (filesystem, task management, subagent delegation) with path requirements
- **[Common Patterns](references/patterns.md)** - Production-ready examples including research agents with memory, code assistants with disk access, multi-specialist teams, and production PostgreSQL setup
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