<overview>
Deep Agents use pluggable backends for file operations and memory:
</backend-selection>
<ex-default-state-backend>
<python>
Default StateBackend stores files ephemerally within a thread.
Short-term (StateBackend): Persists within a single thread, lost when thread ends Long-term (StoreBackend): Persists across threads and sessions Hybrid (CompositeBackend): Route different paths to different backends
FilesystemMiddleware provides tools: ls, read_file, write_file, edit_file, glob, grep
</overview>
| Use Case | Backend | Why |
|---|---|---|
| Temporary working files | StateBackend | Default, no setup |
| Local development CLI | FilesystemBackend | Direct disk access |
| Cross-session memory | StoreBackend | Persists across threads |
| Hybrid storage | CompositeBackend | Mix ephemeral + persistent |
from deepagents import create_deep_agent
agent = create_deep_agent() # Default: StateBackend
result = agent.invoke({
"messages": [{"role": "user", "content": "Write notes to /draft.txt"}]
}, config={"configurable": {"thread_id": "thread-1"}})
# /draft.txt is lost when thread ends
import { createDeepAgent } from "deepagents";
const agent = await createDeepAgent(); // Default: StateBackend
const result = await agent.invoke({
messages: [{ role: "user", content: "Write notes to /draft.txt" }]
}, { configurable: { thread_id: "thread-1" } });
// /draft.txt is lost when thread ends
from deepagents import create_deep_agent
from deepagents.backends import CompositeBackend, StateBackend, StoreBackend
from langgraph.store.memory import InMemoryStore
store = InMemoryStore()
composite_backend = lambda rt: CompositeBackend(
default=StateBackend(rt),
routes={"/memories/": StoreBackend(rt)}
)
agent = create_deep_agent(backend=composite_backend, store=store)
# /draft.txt -> ephemeral (StateBackend)
# /memories/user-prefs.txt -> persistent (StoreBackend)
import { createDeepAgent, CompositeBackend, StateBackend, StoreBackend } from "deepagents";
import { InMemoryStore } from "@langchain/langgraph";
const store = new InMemoryStore();
const agent = await createDeepAgent({
backend: (config) => new CompositeBackend(
new StateBackend(config),
{ "/memories/": new StoreBackend(config) }
),
store
});
// /draft.txt -> ephemeral (StateBackend)
// /memories/user-prefs.txt -> persistent (StoreBackend)
# Using CompositeBackend from previous example
config1 = {"configurable": {"thread_id": "thread-1"}}
agent.invoke({"messages": [{"role": "user", "content": "Save to /memories/style.txt"}]}, config=config1)
config2 = {"configurable": {"thread_id": "thread-2"}}
agent.invoke({"messages": [{"role": "user", "content": "Read /memories/style.txt"}]}, config=config2)
# Thread 2 can read file saved by Thread 1
// Using CompositeBackend from previous example
const config1 = { configurable: { thread_id: "thread-1" } };
await agent.invoke({ messages: [{ role: "user", content: "Save to /memories/style.txt" }] }, config1);
const config2 = { configurable: { thread_id: "thread-2" } };
await agent.invoke({ messages: [{ role: "user", content: "Read /memories/style.txt" }] }, config2);
// Thread 2 can read file saved by Thread 1
from deepagents import create_deep_agent
from deepagents.backends import FilesystemBackend
from langgraph.checkpoint.memory import MemorySaver
agent = create_deep_agent(
backend=FilesystemBackend(root_dir=".", virtual_mode=True), # Restrict access
interrupt_on={"write_file": True, "edit_file": True},
checkpointer=MemorySaver()
)
# Agent can read/write actual files on disk
import { createDeepAgent, FilesystemBackend } from "deepagents";
import { MemorySaver } from "@langchain/langgraph";
const agent = await createDeepAgent({
backend: new FilesystemBackend({ rootDir: ".", virtualMode: true }),
interruptOn: { write_file: true, edit_file: true },
checkpointer: new MemorySaver()
});
Security: Never use FilesystemBackend in web servers - use StateBackend or sandbox instead. </ex-filesystem-backend-local-dev>
<ex-store-in-custom-tools> <python> Access the store directly in custom tools for long-term memory operations.from langchain.tools import tool, ToolRuntime
from langchain.agents import create_agent
from langgraph.store.memory import InMemoryStore
@tool
def get_user_preference(key: str, runtime: ToolRuntime) -> str:
"""Get a user preference from long-term storage."""
store = runtime.store
result = store.get(("user_prefs",), key)
return str(result.value) if result else "Not found"
@tool
def save_user_preference(key: str, value: str, runtime: ToolRuntime) -> str:
"""Save a user preference to long-term storage."""
store = runtime.store
store.put(("user_prefs",), key, {"value": value})
return f"Saved {key}={value}"
store = InMemoryStore()
agent = create_agent(
model="gpt-4.1",
tools=[get_user_preference, save_user_preference],
store=store
)
- Backend type and configuration
- Routing rules for CompositeBackend
- Root directory for FilesystemBackend
- Human-in-the-loop for file operations
What Agents CANNOT Configure
- Tool names (ls, read_file, write_file, edit_file, glob, grep)
- Access files outside virtual_mode restrictions
- Cross-thread file access without proper backend setup </boundaries>
# WRONG
agent = create_deep_agent(backend=lambda rt: StoreBackend(rt))
# CORRECT
agent = create_deep_agent(backend=lambda rt: StoreBackend(rt), store=InMemoryStore())
// WRONG
const agent = await createDeepAgent({ backend: (c) => new StoreBackend(c) });
// CORRECT
const agent = await createDeepAgent({ backend: (c) => new StoreBackend(c), store: new InMemoryStore() });
# WRONG: thread-2 can't read file from thread-1
agent.invoke({"messages": [...]}, config={"configurable": {"thread_id": "thread-1"}}) # Write
agent.invoke({"messages": [...]}, config={"configurable": {"thread_id": "thread-2"}}) # File not found!
// WRONG: thread-2 can't read file from thread-1
await agent.invoke({ messages: [...] }, { configurable: { thread_id: "thread-1" } }); // Write
await agent.invoke({ messages: [...] }, { configurable: { thread_id: "thread-2" } }); // File not found!
# With routes={"/memories/": StoreBackend(rt)}:
agent.invoke(...) # /prefs.txt -> ephemeral (no match)
agent.invoke(...) # /memories/prefs.txt -> persistent (matches route)
// With routes: { "/memories/": StoreBackend }:
await agent.invoke(...); // /prefs.txt -> ephemeral (no match)
await agent.invoke(...); // /memories/prefs.txt -> persistent (matches route)
# WRONG # CORRECT
store = InMemoryStore() store = PostgresStore(connection_string="postgresql://...")
// WRONG // CORRECT
const store = new InMemoryStore(); const store = new PostgresStore({ connectionString: "..." });
backend = FilesystemBackend(root_dir="/project", virtual_mode=True) # Secure
routes = {"/mem/": StoreBackend(rt), "/mem/temp/": StateBackend(rt)}
# /mem/file.txt -> StoreBackend, /mem/temp/file.txt -> StateBackend (longer match)
