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Introduction

SLIM (Secure Low-Latency Interactive Messaging) is the transport layer for the agentic AI era — a secure, peer-to-peer messaging framework that lets agents communicate across networks, organizations, and trust boundaries without rebuilding the same infrastructure every time.

Why SLIM?

Modern agentic workloads share three characteristics that make communication hard:

  • Collaborative

    Agents share high volumes of context in real time and coordinate complex multi-step tasks. Communication must be bidirectional, low-latency, and support multiparty interaction patterns natively.

  • Sensitive

    Agents share sensitive data — code, plans, personal information, business logic. Network-level TLS is not enough: if a middlebox is compromised, traffic can be read. Data must be encrypted end-to-end.

  • Distributed

    Agents run across multiple clouds, organizations, and networks. Communication must traverse NAT, firewalls, and organizational boundaries without requiring agents to be directly internet-exposed.

The gap in existing solutions

No single existing technology addresses all three requirements:

System Gap
Message queues (SQS, RabbitMQ, Kafka, NATS) One-directional; no E2E encryption; can't cross org boundaries; no native RPC
HTTP / gRPC No group communication; no E2E encryption; requires agents to be directly internet-exposed

The result: developers keep re-implementing the missing pieces in every application.

What SLIM brings

SLIM is built from the ground up for agentic workloads:

Capability How SLIM delivers it
Bidirectional, low-latency transport Built on gRPC over HTTP/2 — multiplexed, efficient, and NAT/firewall-friendly without any special configuration
End-to-end encryption MLS (RFC 9420) encrypts data at the session layer — even a compromised routing node cannot read message content
Group communication Native multicast and group sessions; agents join shared channels identified by hierarchical names
Cross-org federation SPIRE-based identity federation lets agents in different organizations communicate with verified cryptographic identities
No central broker Peer-to-peer architecture; no single point of failure or trust
Native RPC SLIMRPC provides Protobuf RPC over SLIM — all the capabilities of gRPC, plus multicast RPC over group channels

Interaction Patterns

SLIM natively supports four interaction patterns between agents:

Pattern Description
Point-to-Point One agent sends directly to another, identified by a hierarchical DID-based name
Group / Multicast One agent broadcasts to a shared channel; all members receive the message
RPC (P2P) Request-response between two agents — like gRPC but over SLIM's encrypted overlay
RPC (Multicast) One client calls many servers simultaneously — fan-out requests to a group channel

Agents are identified using a hierarchical naming scheme based on Decentralized Identifiers:

organization/namespace/service/<hash-of-public-key>

Group channels use the same four-component scheme. The last component is a UUID derived from the moderator's key material. Each group gets two channel names — a data channel and a control channel — that differ only in their final UUID component.

SLIM vs. Message Queues

Capability Message Queue SLIM
Bidirectional communication ❌ Needs a response topic ✅ Native
End-to-end encryption ❌ Broker can read all traffic ✅ MLS E2E
Cross-org / internet exposure ❌ Many impossible to expose ✅ Works across organizations
Native RPC ❌ Not natively supported ✅ SLIMRPC
Group sessions (multi-party) ❌ Topic fan-out only ✅ MLS groups
Multi-org federation ❌ Complex bespoke work ✅ Built-in with SPIRE
Works behind NAT / firewalls ⚠️ Depends on deployment ✅ Registration model

Components

SLIM is composed of five components:

  • Data Plane — high-performance message routing node that forwards messages between applications
  • Controller — manages route tables, node registration, and group membership across clusters
  • Channel Manager — operator-managed service for creating and moderating group channels
  • CLI (slimctl) — command-line tool for operating and interacting with SLIM nodes
  • SDK — language-native bindings (Python, Go, .NET, JavaScript, Java, Kotlin) for building applications on SLIM

For a detailed breakdown of how the layers fit together, see Architecture.

Next Steps

  • Getting Started — install all components and send your first message
  • Architecture — understand the four-layer SLIM stack
  • Components — explore each component in depth
  • Deployment — choose a deployment topology for your use case