emem-langmem

LangChain BaseStore backed by emem.dev — drop-in agent memory for LangGraph with ed25519 receipts and content-addressed recall.

Install

pip install emem-langmem

Use

from emem_langmem import EmemStore
from langgraph.graph import StateGraph

store = EmemStore(base_url="https://emem.dev", signing_key=SEED)

graph = StateGraph(...).compile(store=store)

SEED is a raw 32-byte ed25519 seed that you own and persist, for example os.urandom(32) once, then kept wherever the agent's other secrets live. It signs every write, and the responder requires that: an unattested write is refused unless the operator opened the responder with EMEM_MEMORY_OPEN=1. The key also decides where the store writes.

EmemStore implements the four BaseStore verbs by issuing MCP tools/call requests to the emem responder against the six Anthropic memory-tool verbs:

Namespaces

With a signing key, the store roots itself at /memories/by_attester/<pubkey8>/, where <pubkey8> is the first 8 characters of your base32 pubkey. Only that key can write there, so agents sharing one responder cannot overwrite each other. LangChain calls mget(("ns","key")) and the store reads /memories/by_attester/<pubkey8>/ns/key.

store.root              # '/memories/by_attester/aoqqpp7t'
store.signer.pubkey_b32 # the full base32 pubkey

A key that starts with / is taken as a literal absolute path and is left alone, which is how you reach outside your own root. Writing into another key's namespace is refused with a 403. Without a signing key the root stays /memories and writes go out unattested. See docs/memory.html for the wire format.

EmemSigner is public if you drive the memory tools yourself and need the same attester block:

from emem_langmem import EmemSigner

signer = EmemSigner(SEED)
signer.attester_block("create", f"{signer.namespace_root}/n.md", b"hi")
# {'pubkey_b32': '...', 'sig_b32': '...'}

Async variants amget / amset / amdelete / ayield_keys are implemented over httpx.AsyncClient.

Self-host

EmemStore(base_url="http://127.0.0.1:5051")

or set EMEM_BASE_URL in the environment.

Receipts

Every read and write returns an ed25519 receipt from the emem responder. The receipt is currently dropped at the BaseStore interface boundary (LangChain's contract has no receipt slot). To inspect receipts, call the underlying MCP tool directly:

import json, httpx, uuid
r = httpx.post(
    "https://emem.dev/mcp",
    json={
        "jsonrpc": "2.0",
        "id": str(uuid.uuid4()),
        "method": "tools/call",
        "params": {
            "name": "emem_memory_view",
            "arguments": {"path": "/memories/my/note.txt"},
        },
    },
).json()
print(r["result"]["structuredContent"]["receipt"])

License

Apache-2.0.