---

What is Membrane?

Membrane is a programmable memory runtime for AI agents.

Memory should be managed like a computational resource, not retrieved like a document collection.

Traditional RAG is usually:

query → embed → vector search → context

Membrane is:

query / event
      ↓
memory controller
      ↓
read · write · update · forget
      ↓
memory query planner
      ↓
memory router
      ↓
structured · semantic · temporal · graph · KV · episodic
      ↓
rank · merge · budget · explain
      ↓
working context

The core is LLM-optional. Deterministic memory management works locally without an API key or mandatory vector database.

Quickstart

pip install membrane-memory

from membrane import Memory

memory = Memory()

memory.remember(
    "The user prefers concise technical explanations.",
    user_id="alice_123",
)

result = memory.recall(
    "How should I communicate with this user?",
    user_id="alice_123",
)

print(result.memories[0].content)

SQLite is the default local substrate.

---

Architecture

The architecture separates the memory control plane from the memory data plane.

flowchart TB
    Q[User Query q_t]
    X[New Information x_t]
    C[Context c_t]
    O[Outcome / Feedback]

    Q --> G
    X --> G
    C --> G
    O --> G

    subgraph G[Memory Cell / LSTM-inspired Controller]
        F[Forget Gate f_t]
        I[Write Gate i_t]
        M[Candidate Memory M_tilde]
        U[Update Gate u_t]
        R[Read Gate o_t]
    end

    G --> P[Memory Query Planner]
    P --> RT[Memory Router]

    RT --> S[Structured]
    RT --> V[Semantic]
    RT --> T[Temporal]
    RT --> GR[Graph]
    RT --> K[KV / Working]
    RT --> E[Episodic]

    S --> W[Working Context]
    V --> W
    T --> W
    GR --> W
    K --> W
    E --> W

    W --> A[Agent / LLM]
    A --> O

Critical design distinction

The LSTM-inspired component is a memory controller, not an LSTM-shaped database.

A vanilla LSTM has a dense cell state. Membrane uses a compact controller state to produce policies over external, heterogeneous memory.

This makes the LSTM analogy useful without pretending SQL rows, graph nodes, and vector records are literally an LSTM cell tensor.

---

Memory Gates

Define:

z_t = [q_t ; x_t ; c_t ; h_{t-1}]

Forget gate

f_t = σ(W_f z_t + b_f)

Controls retention, decay, expiration, and removal from active memory.

Write gate

i_t = σ(W_i z_t + b_i)

Controls admission of new observations.

Candidate memory

M̃_t = φ(W_m z_t + b_m)

Represents proposed new memory.

Update gate

u_t = σ(W_u z_t + b_u)

Controls revision and supersession.

LSTM-inspired state update

M̄_t = f_t ⊙ M_{t-1} + i_t ⊙ M̃_t

M_t = (1-u_t) ⊙ M_{t-1} + u_t ⊙ M̄_t

Read gate

o_t = σ(W_o [h_t ; q_t] + b_o)

R_t = o_t ⊙ Retrieve(Plan(q_t, c_t), M)

The read gate controls how much selected memory enters working context.

---

Memory Lifecycle

CANDIDATE
    │
    ├── accepted ───────► ACTIVE
    │                       │
    │                       ├── revised ──► UPDATED / SUPERSEDED
    │                       ├── stale ────► ARCHIVED
    │                       └── expired ──► FORGOTTEN
    │
    └── unsafe ─────────► QUARANTINED

Every transition is intended to be auditable rather than silently destructive.

---

Memory Query Planner

Not every memory query is semantic search.

Query	Preferred substrate
What does the user prefer?	Semantic
What is the current price?	Structured / KV
What changed last week?	Temporal
Who is connected to this project?	Graph
What happened during the previous run?	Episodic
What is the latest state?	KV / Structured
Why was this decision made?	Hybrid + Provenance

The planner produces an inspectable plan before execution.

---

Memory Substrates

Substrate	Purpose	Example
Structured	exact facts and attributes	SQLite / PostgreSQL
Semantic	conceptual similarity	Qdrant / pgvector
Temporal	history and point-in-time state	SQL / event log
Graph	relationships and causal links	Neo4j
KV / Working	current state and fast lookup	Redis / SQLite
Episodic	events and artifacts	object store / filesystem

Membrane does not require all substrates to be installed.

---

Temporal Memory

Current truth and historical truth are different queries.

memory.remember(
    "SKU 123 price is $10",
    structured={"entity": "sku_123", "attribute": "price", "value": 10},
)

memory.remember(
    "SKU 123 price is $12",
    structured={"entity": "sku_123", "attribute": "price", "value": 12},
)

memory.recall("current price", entity="sku_123")
memory.timeline("sku_123")

The current record can supersede the previous record while the historical record remains recoverable.

---

Provenance and Outcome Memory

Membrane tracks the path:

source
  ↓
observation
  ↓
memory candidate
  ↓
gate decision
  ↓
stored / superseded memory
  ↓
retrieval plan
  ↓
working context
  ↓
agent decision
  ↓
outcome

This enables outcome-based reinforcement:

decision → action → outcome → utility → memory policy update

---

Security

Memory is an attack surface.

Untrusted instruction-like observations should be isolated:

untrusted observation
        ↓
   trust / policy gate
       / \
      /   \
 trusted  suspicious
   ↓          ↓
 ACTIVE   QUARANTINED

Policies can control tenant isolation, source trust, retention, write permissions, sensitive fields, and retrieval scope.

---

Research Direction

The central research question is:

Can an AI system dynamically manage heterogeneous memory as a computational resource?

Potential research dimensions:

• learned memory gating
• temporal contradiction resolution
• adaptive forgetting
• consolidation
• outcome-based reinforcement
• substrate routing
• context-budget optimization
• LLM-free memory control
• replay

A future MemoryBench should measure retrieval quality, temporal correctness, contradiction rate, write/forget precision, consolidation quality, latency, storage growth, and token consumption.

Design Principles

1. Memory is not RAG. Semantic retrieval is only one mechanism.
2. Control and storage are separate.
3. Exact facts should remain structured.
4. History should be preserved.
5. Memory should be budget-aware.
6. LLMs are optional infrastructure.
7. Important decisions should be explainable.

Contributing

git clone https://github.com/dcsgod/membrane.git
cd membrane
pip install -e ".[dev]"
pytest

License

Apache 2.0.