- Task Planning: TodoListMiddleware for breaking down complex tasks
- Context Management: Filesystem tools with pluggable backends
- Task Delegation: SubAgent middleware for spawning specialized agents
- Long-term Memory: Persistent storage across threads via Store
- Human-in-the-loop: Approval workflows for sensitive operations
- Skills: On-demand loading of specialized capabilities
The agent harness provides these capabilities automatically - you configure, not implement.
| Use Deep Agents When |
Use LangChain's create_agent When |
| Multi-step tasks requiring planning |
Simple, single-purpose tasks |
| Large context requiring file management |
Context fits in a single prompt |
| Need for specialized subagents |
Single agent is sufficient |
| Persistent memory across sessions |
Ephemeral, single-session work |
| If you need to... |
Middleware |
Notes |
| Track complex tasks |
TodoListMiddleware |
Default enabled |
| Manage file context |
FilesystemMiddleware |
Configure backend |
| Delegate work |
SubAgentMiddleware |
Add custom subagents |
| Add human approval |
HumanInTheLoopMiddleware |
Requires checkpointer |
| Load skills |
SkillsMiddleware |
Provide skill directories |
| Access memory |
MemoryMiddleware |
Requires Store instance |
@tool
def get_weather(city: str) -> str:
"""Get the weather for a given city."""
return f"It is always sunny in {city}"
agent = create_deep_agent(
model="claude-sonnet-4-5-20250929",
tools=[get_weather],
system_prompt="You are a helpful assistant"
)
config = {"configurable": {"thread_id": "user-123"}}
result = agent.invoke({
"messages": [{"role": "user", "content": "What's the weather in Tokyo?"}]
}, config=config)
</python>
<typescript>
Create a basic deep agent with a custom tool and invoke it with a user message.
```typescript
import { createDeepAgent } from "deepagents";
import { tool } from "@langchain/core/tools";
import { z } from "zod";
const getWeather = tool(
async ({ city }) => `It is always sunny in ${city}`,
{ name: "get_weather", description: "Get weather for a city", schema: z.object({ city: z.string() }) }
);
const agent = await createDeepAgent({
model: "claude-sonnet-4-5-20250929",
tools: [getWeather],
systemPrompt: "You are a helpful assistant"
});
const config = { configurable: { thread_id: "user-123" } };
const result = await agent.invoke({
messages: [{ role: "user", content: "What's the weather in Tokyo?" }]
}, config);
agent = create_deep_agent(
name="my-assistant",
model="claude-sonnet-4-5-20250929",
tools=[custom_tool1, custom_tool2],
system_prompt="Custom instructions",
subagents=[research_agent, code_agent],
backend=FilesystemBackend(root_dir=".", virtual_mode=True),
interrupt_on={"write_file": True},
skills=["./skills/"],
checkpointer=MemorySaver(),
store=InMemoryStore()
)
</python>
<typescript>
Configure a deep agent with all available options including subagents, skills, and persistence.
```typescript
import { createDeepAgent, FilesystemBackend } from "deepagents";
import { MemorySaver, InMemoryStore } from "@langchain/langgraph";
const agent = await createDeepAgent({
name: "my-assistant",
model: "claude-sonnet-4-5-20250929",
tools: [customTool1, customTool2],
systemPrompt: "Custom instructions",
subagents: [researchAgent, codeAgent],
backend: new FilesystemBackend({ rootDir: ".", virtualMode: true }),
interruptOn: { write_file: true },
skills: ["./skills/"],
checkpointer: new MemorySaver(),
store: new InMemoryStore()
});
- Planning:
write_todos - Track multi-step tasks
- Filesystem:
ls, read_file, write_file, edit_file, glob, grep
- Delegation:
task - Spawn specialized subagents
SKILL.md Format
Directory Structure
skills/
└── my-skill/
├── SKILL.md # Required: main skill file
├── examples.py # Optional: supporting files
└── templates/ # Optional: templates
SKILL.md Format
---
name: my-skill
description: Clear, specific description of what this skill does
---
# Skill Name
## Overview
Brief explanation of the skill's purpose.
## When to Use
Conditions when this skill applies.
## Instructions
Step-by-step guidance for the agent.
| Skills |
Memory (AGENTS.md) |
| On-demand loading |
Always loaded at startup |
| Task-specific instructions |
General preferences |
| Large documentation |
Compact context |
| SKILL.md in directories |
Single AGENTS.md file |
agent = create_deep_agent(
backend=FilesystemBackend(root_dir=".", virtual_mode=True),
skills=["./skills/"],
checkpointer=MemorySaver()
)
result = agent.invoke({
"messages": [{"role": "user", "content": "Use the python-testing skill"}]
}, config={"configurable": {"thread_id": "session-1"}})
</python>
<typescript>
Set up an agent with skills directory and filesystem backend for on-demand skill loading.
```typescript
import { createDeepAgent, FilesystemBackend } from "deepagents";
import { MemorySaver } from "@langchain/langgraph";
const agent = await createDeepAgent({
backend: new FilesystemBackend({ rootDir: ".", virtualMode: true }),
skills: ["./skills/"],
checkpointer: new MemorySaver()
});
const result = await agent.invoke({
messages: [{ role: "user", content: "Use the python-testing skill" }]
}, { configurable: { thread_id: "session-1" } });
store = InMemoryStore()
Load skill content into store
skill_content = """---
name: python-testing
description: Best practices for Python testing with pytest
Python Testing Skill
..."""
store.put(
namespace=("filesystem",),
key="/skills/python-testing/SKILL.md",
value=create_file_data(skill_content)
)
agent = create_deep_agent(
backend=lambda rt: StoreBackend(rt),
store=store,
skills=["/skills/"]
)
</python>
</ex-skills-with-store-backend>
<boundaries>
### What Agents CAN Configure
- Model selection and parameters
- Additional custom tools
- System prompt customization
- Backend storage strategy
- Which tools require approval
- Custom subagents with specialized tools
### What Agents CANNOT Configure
- Core middleware removal (TodoList, Filesystem, SubAgent always present)
- The write_todos, task, or filesystem tool names
- The SKILL.md frontmatter format
</boundaries>
<fix-checkpointer-for-interrupts>
<python>
Interrupts require a checkpointer.
```python
# WRONG
agent = create_deep_agent(interrupt_on={"write_file": True})
# CORRECT
agent = create_deep_agent(interrupt_on={"write_file": True}, checkpointer=MemorySaver())
// CORRECT
const agent = await createDeepAgent({ interruptOn: { write_file: true }, checkpointer: new MemorySaver() });
</typescript>
</fix-checkpointer-for-interrupts>
<fix-store-for-memory>
<python>
StoreBackend requires a Store instance for persistent memory across threads.
```python
# WRONG
agent = create_deep_agent(backend=lambda rt: StoreBackend(rt))
# CORRECT
agent = create_deep_agent(backend=lambda rt: StoreBackend(rt), store=InMemoryStore())
// CORRECT
const agent = await createDeepAgent({ backend: (config) => new StoreBackend(config), store: new InMemoryStore() });
</typescript>
</fix-store-for-memory>
<fix-thread-id-for-conversations>
<python>
Use consistent thread_id to maintain conversation context across invocations.
```python
# WRONG: Each invocation is isolated
agent.invoke({"messages": [{"role": "user", "content": "Hi"}]})
agent.invoke({"messages": [{"role": "user", "content": "What did I say?"}]})
# CORRECT
config = {"configurable": {"thread_id": "user-123"}}
agent.invoke({"messages": [...]}, config=config)
agent.invoke({"messages": [...]}, config=config)
// CORRECT
const config = { configurable: { thread_id: "user-123" } };
await agent.invoke({ messages: [...] }, config);
await agent.invoke({ messages: [...] }, config);
</typescript>
</fix-thread-id-for-conversations>
<fix-frontmatter-required>
```markdown
# WRONG: Missing frontmatter in SKILL.md
# My Skill
This is my skill...
# CORRECT: Include YAML frontmatter
---
name: my-skill
description: Python testing best practices with pytest fixtures and mocking
---
# My Skill
This is my skill...
CORRECT: Use FilesystemBackend for local skills
agent = create_deep_agent(
backend=FilesystemBackend(root_dir=".", virtual_mode=True),
skills=["./skills/"]
)
</python>
</fix-backend-for-skills>
<fix-specific-skill-descriptions>
Use specific descriptions to help agents decide when to use a skill.
```markdown
# WRONG: Vague description
---
name: helper
description: Helpful skill
---
# CORRECT: Specific description
---
name: python-testing
description: Python testing best practices with pytest fixtures, mocking, and async patterns
---
CORRECT: Provide skills explicitly
agent = create_deep_agent(
skills=["/main-skills/"],
subagents=[{"name": "helper", "skills": ["/helper-skills/"], ...}]
)
</python>
</fix-subagent-skills>
