agenticweb.wiki

Secure Low-Latency Interactive Messaging (SLIM)

Last checked · 39 primary sources

This page is about Secure Low-Latency Interactive Messaging (SLIM), the AGNTCY project's secure messaging layer that carries agent protocols over gRPC with optional end-to-end encryption by Messaging Layer Security (MLS) [1][2][13]. It is not an agent protocol in its own right: the Agent2Agent Protocol (A2A) and the Model Context Protocol (MCP) can run over it [4][5]. It is not IBM's Agent Communication Protocol (ACP), and it is not AGNTCY's Agent Connect Protocol (AGNTCY) (ACP). For AGNTCY's agent records and directory, see the Open Agentic Schema Framework (OASF) and the Agent Directory Service (ADS); for the workload identity that SLIM can use, see SPIFFE [3].

Overview

Secure Low-Latency Interactive Messaging (SLIM) is a messaging layer that carries agent protocols such as A2A and MCP between agents across networks and organisations, built on gRPC and routed through SLIM nodes by hierarchical names [1][13]. It offers point-to-point and group sessions, with end-to-end encryption by Messaging Layer Security (MLS) that is optional for groups and the default for the A2A binding [2][22]. Outshift by Cisco started it within AGNTCY, which joined the Linux Foundation in July 2025, and four Cisco engineers have filed it at the IETF as an individual Internet-Draft with no formal standing [17][16][13][10]. A2A runs over it through an experimental binding hosted by the A2A project, while MCP runs over it through AGNTCY packages that the MCP specification does not name [4][20][5][29].

Architecture, IETF draft, and protocol bindings

Who uses it

Who reads it

Dated stances of the organisations around SLIM

Recent coverage

See also

References

  1. SLIM documentation (slim.agntcy.org), Introduction - SLIM, checked 2026-10-29: "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." "MLS (RFC 9420) encrypts data at the session layer — even a compromised routing node cannot read message content" "SPIRE-based identity federation lets agents in different organizations communicate with verified cryptographic identities" "SLIM is composed of five components:" "Built on gRPC over HTTP/2 — multiplexed, efficient, and NAT/firewall-friendly without any special configuration" — https://slim.agntcy.org/latest/slim/slim-overview/
  2. SLIM documentation (slim.agntcy.org), Groups - SLIM, checked 2026-10-29: "Groups optionally use the MLS protocol for end-to-end encryption." "Adding or removing a member triggers a key rotation, so former members lose access to future messages and new members cannot read past messages (forward and post-compromise security)" "When MLS is disabled, the group still has consistent membership state and reliable delivery, but messages are not end-to-end encrypted beyond whatever transport-layer TLS is in use." — https://slim.agntcy.org/latest/slim/architecture/sessions/group/
  3. SLIM documentation (slim.agntcy.org), Authentication - SLIM, checked 2026-10-29: "SLIM authentication has two distinct concerns that operate independently: transport security between network peers, and application identity used to authenticate messages between applications." — https://slim.agntcy.org/latest/slim/architecture/authentication/
  4. SLIM documentation (slim.agntcy.org), A2A - SLIM, checked 2026-10-29: "SLIM provides a fourth, experimental binding: SLIMRPC." "Instead of HTTP, it uses SLIM's encrypted session layer as the transport — bringing end-to-end encryption, built-in service discovery, and native multi-cloud routing to A2A without requiring ingress controllers or API gateways." — https://slim.agntcy.org/latest/slim/integrations/a2a/
  5. SLIM documentation (slim.agntcy.org), MCP - SLIM, checked 2026-10-29: "SLIM replaces that transport with an encrypted, identity-aware overlay — so MCP clients and servers can reach each other across networks and organizations without exposing every server to the internet." "no changes to MCP tool definitions or server logic are required" — https://slim.agntcy.org/latest/slim/integrations/mcp/
  6. agntcy/slim repository on GitHub (raw file): CHANGELOG.md (newest entry read live), checked 2026-10-29: "The Go control plane has been replaced by a full Rust implementation, enabling tighter integration with the data plane and removing the Go runtime dependency" — https://raw.githubusercontent.com/agntcy/slim/main/CHANGELOG.md
  7. agntcy/slim repository on GitHub (raw file): Maintainers (MAINTAINERS.md, 5 maintainers read live), checked 2026-10-29: "Mauro Sardara" "Michele Papalini" "Luca Muscariello" "Peter Balogh" "Zsolt Kacsandi" — https://raw.githubusercontent.com/agntcy/slim/main/MAINTAINERS.md
  8. GitHub API, repository metadata for agntcy/slim (created 2025-02-05, licence read live), checked 2026-10-29: ""full_name":"agntcy/slim"" ""created_at":"2025-02-05T19:44:53Z"" ""spdx_id":"Apache-2.0"" — https://api.github.com/repos/agntcy/slim
  9. GitHub API, release list for agntcy/slim, newest 100 releases (tags and publication dates read live), checked 2026-10-29: ""tag_name":"slimctl-v3.4.6"" ""tag_name":"slim-v3.4.6"" ""published_at":"2026-10-20T16:55:02Z"" — https://api.github.com/repos/agntcy/slim/releases?per_page=100
  10. IETF Datatracker, draft-mpsb-agntcy-slim-02 - Secure Low-Latency Interactive Messaging (SLIM), checked 2026-10-29: "Active Internet-Draft (individual)" "This I-D is not endorsed by the IETF and has no formal standing in the IETF standards process." "Last updated 2026-07-18"; the draft header shown on that page says "Intended status: Informational" and "Expires: 8 January 2027" (Datatracker expiry 2027-01-20 UTC) — https://datatracker.ietf.org/doc/draft-mpsb-agntcy-slim/
  11. IETF Datatracker API, document record for draft-mpsb-agntcy-slim (rev, time, expiry, group, stream and states read live), checked 2026-10-29: ""name": "draft-mpsb-agntcy-slim"" ""rev": "02"" ""time": "2026-07-19T04:37:05Z"" — https://datatracker.ietf.org/api/v1/doc/document/draft-mpsb-agntcy-slim/
  12. IETF Datatracker API, new-revision events for draft-mpsb-agntcy-slim (revision times read live, UTC), checked 2026-10-29: ""rev": "02"" ""time": "2026-07-19T04:37:05Z"" ""rev": "01"" ""time": "2026-02-24T22:24:54Z"" ""rev": "00"" ""time": "2025-10-16T13:34:11Z"" — https://datatracker.ietf.org/api/v1/doc/newrevisiondocevent/?doc__name=draft-mpsb-agntcy-slim&format=json
  13. L. Muscariello, M. Papalini, M. Sardara and S. Betts (Cisco), Secure Low-Latency Interactive Messaging (SLIM), Internet-Draft draft-mpsb-agntcy-slim-02, 2026-07-07, checked 2026-10-29: "Authors: L. Muscariello Cisco M. Papalini Cisco M. Sardara Cisco S. Betts Cisco" "Published: 7 July 2026" "SLIM provides the transport layer for agent protocols (for example, A2A and MCP), combining gRPC over HTTP/2 and HTTP/3 with secure messaging, group communication, and native RPC semantics." "The protocol leverages Message Layer Security (MLS) for end-to-end encryption, ensuring that messages remain confidential even when passing through intermediate nodes or experiencing TLS termination along the communication path." "The name structure follows a organization/namespace/service/instance pattern, supporting anycast and unicast routing as well as service discovery." — https://www.ietf.org/archive/id/draft-mpsb-agntcy-slim-02.html
  14. IETF Datatracker API, document record for draft-mpsb-agntcy-messaging (rev, time and title read live), checked 2026-10-29: ""name": "draft-mpsb-agntcy-messaging"" ""rev": "02"" ""time": "2026-07-19T04:36:18Z"" ""title": "An Overview of Messaging Systems and Their Applicability to Agentic AI"" — https://datatracker.ietf.org/api/v1/doc/document/draft-mpsb-agntcy-messaging/
  15. IETF 126, Minutes IETF126: dmsc: Wed 07:00 (DMSC session of 2026-07-22), checked 2026-10-29: "In LF Agntcy project we've been working on a protocol and implementation called SLIM which is a decentralised group messaging system based on MLS purpose built for Agents." "We can carry semantic protocols like A2A over the top, or simply direct messaging with group broadcast or point to point requests." — https://datatracker.ietf.org/doc/minutes-126-dmsc-202607220700/
  16. The Linux Foundation, Linux Foundation Welcomes the AGNTCY Project to Standardize Open Multi-Agent System Infrastructure and Break Down AI Agent Silos (press release), 2025-07-29, checked 2026-10-29: "today welcomed the AGNTCY project, an open source infrastructure that enables discovery, identity, messaging, and observability among AI agents from different vendors and frameworks." "Cisco, Dell Technologies, Google Cloud, Oracle, and Red Hat have joined as formative members of the AGNTCY project under Linux Foundation governance." — https://www.linuxfoundation.org/press/linux-foundation-welcomes-the-agntcy-project-to-standardize-open-multi-agent-system-infrastructure-and-break-down-ai-agent-silos
  17. Outshift by Cisco, AGNTCY | Internet of Agents | Outshift by Cisco (project history page, launch date 2025-03-06), checked 2026-10-29: "AGNTCY was created by Outshift and is now a Linux Foundation project." "Launch date: March 6, 2025" — https://outshift.cisco.com/the-internet-of-agents/agntcy
  18. agntcy/governance repository on GitHub (raw file): AGNTCY, a Series of LF Projects: Contributing Guide (CONTRIBUTING.md, TSC roster read live), checked 2026-10-29: "AGNTCY aims to create a common infrastructure layer for AI agent-to-agent collaboration across the complete multi-agent software lifecycle: from discovery and identification, to communication, deployment, observability, and evaluation." — https://raw.githubusercontent.com/agntcy/governance/main/CONTRIBUTING.md
  19. agntcy/governance repository on GitHub (raw file): OPERATING_MODEL.md, checked 2026-10-29: "The AGNTCY Technical Steering Committee (TSC) is responsible for the governance of projects jointly owned under AGNTCY and its sub-projects." — https://raw.githubusercontent.com/agntcy/governance/main/OPERATING_MODEL.md
  20. a2aproject/experimental-cpb-slimrpc on GitHub, SLIMRPC custom protocol binding for A2A (README), checked 2026-10-29: "Status: Experimental — This is a community-contributed custom protocol binding for A2A. It is not part of the core A2A specification." "https://a2a-protocol.org/bindings/experimental-slimrpc/v1" — https://github.com/a2aproject/experimental-cpb-slimrpc
  21. GitHub API, repository metadata for a2aproject/experimental-cpb-slimrpc (created 2026-05-14, licence read live), checked 2026-10-29: ""full_name":"a2aproject/experimental-cpb-slimrpc"" ""created_at":"2026-05-14T06:43:30Z"" — https://api.github.com/repos/a2aproject/experimental-cpb-slimrpc
  22. a2aproject/a2a-rs on GitHub, a2a-rs/a2a-slimrpc (crate README), checked 2026-10-29: "SLIMRPC bindings for A2A v1 client and server implementations." "The peer keys are set only when the session uses MLS (the SLIMRPC default), since MLS is what verifies the token." — https://github.com/a2aproject/a2a-rs/tree/main/a2a-slimrpc
  23. A2A Protocol documentation, Custom Protocol Bindings - A2A Protocol, checked 2026-10-29: "The A2A protocol ships with three standard bindings (JSON-RPC, gRPC, and HTTP+JSON/REST) that cover the majority of deployment scenarios." — https://a2a-protocol.org/latest/topics/custom-protocol-bindings/
  24. A2A Protocol, Agent2Agent (A2A) Protocol Specification (scanned live for SLIM), checked 2026-10-29: "Agent2Agent (A2A) Protocol Specification" — https://a2a-protocol.org/latest/specification/
  25. agntcy/slim-mcp-python repository on GitHub (raw file): README.md, checked 2026-10-29: "Leverage SLIM as a transport mechanism for MCP, enabling efficient load balancing and dynamic discovery across MCP servers." — https://raw.githubusercontent.com/agntcy/slim-mcp-python/main/README.md
  26. PyPI JSON API, slim-mcp (current version and upload time read live), checked 2026-10-29: ""version":"0.2.3"" ""upload_time":"2026-06-24T06:59:47"" — https://pypi.org/pypi/slim-mcp/json
  27. PyPI JSON API, slima2a (current version and upload time read live), checked 2026-10-29: ""version":"0.9.3"" ""upload_time":"2026-10-22T13:05:34"" — https://pypi.org/pypi/slima2a/json
  28. PyPI JSON API, slim-bindings (current version and upload time read live), checked 2026-10-29: ""version":"3.3.9"" ""upload_time":"2026-10-27T10:29:07"" — https://pypi.org/pypi/slim-bindings/json
  29. Model Context Protocol specification 2026-07-28, Transports (scanned live for SLIM), checked 2026-10-29: "It is also possible for clients and servers to implement custom transports." — https://modelcontextprotocol.io/specification/2026-07-28/basic/transports
  30. modelcontextprotocol/modelcontextprotocol on GitHub, SEP-2598: Pluggable Transports (pull request #2598; deferred 2026-05-05), checked 2026-10-29: "stdio and Streamable HTTP remain the only Standard transports." "This was reviewed by the Core Maintainers and the decision was to Defer." — https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2598
  31. Remaker-Digital/agntcy-on-azure on GitHub, Fix container crash issues and add real API integrations (commit e539bb3), checked 2026-10-29: "SLIM Gateway Fix (ExitCode 2, 294 restarts)" "SLIM requires --config /config.yaml, not --port" — https://github.com/Remaker-Digital/agntcy-on-azure/commit/e539bb37b5598dd5f8e376f3549429682c34ddab
  32. GitHub API, commit e539bb3 in Remaker-Digital/agntcy-on-azure (committed 2026-01-27), checked 2026-10-29: ""date":"2026-01-27T09:18:40Z"" — https://api.github.com/repos/Remaker-Digital/agntcy-on-azure/commits/e539bb37b5598dd5f8e376f3549429682c34ddab
  33. Outshift by Cisco, Transforming OpenAPI specs into AI agents with CAIPE Components and Komodor (LinkedIn post), 2025-10-23, checked 2026-10-29: "powerful new workflow using CAIPE Components, AGNTCY SLIM, LangGraph, and the A2A protocol" "We put it to the test with Komodor's Kubernetes API, proving the system's ability to handle real-world complexity with zero manual coding." — https://www.linkedin.com/posts/outshiftbycisco_building-ai-agents-just-got-faster-and-smarter-activity-7387159283827634177-KZa4
  34. AGNTCY Blogs, The Future of Travel: Building a Multi-Agent Ecosystem with the Internet of Agents, 2026-01-15, checked 2026-10-29: "We use SLIM to ensure every message is encrypted and authenticated via MLS." "uses Google's Agent Development Kit (ADK)" — https://blogs.agntcy.org/agents/kubernetes/demo/slim/open-telemetry/2026/01/15/blog-touring-scheduling-system.html
  35. Tech Mahindra, Agentic AI in Healthcare (Insights), 2025-11-27, checked 2026-10-29: "Integrating AGNTCY's SLIM (Secure Low-Latency Interactive Messaging) will reduce agent-to-agent communication latency, enabling near real-time orchestration." — https://www.techmahindra.com/insights/views/agentic-ai-healthcare/
  36. wolfSSL, SLIM: Securing AI Agent Communication with MLS (blog; published 2025-09-03 per page metadata), checked 2026-10-29: "here at wolfSSL we are closely monitoring developments in Agent to Agent communication protocols such as A2A and SLIM." "We are actively working on an MLS implementation" — https://www.wolfssl.com/slim-securing-ai-agent-communication-with-mls/
  37. Romain Valentin, AGNTCY: the open standard set to structure the Internet of Agents (Splunk blog), 2026-09-09, checked 2026-10-29: "SLIM is designed as a network-level messaging substrate on which application protocols like A2A, MCP or AGNTCY's ACP can rely." "The point of separating transport (SLIM) from semantics (A2A, MCP, ACP) is architectural: application protocols focus on what agents say to each other, while SLIM guarantees how the message travels, safely and efficiently." — https://www.splunk.com/en_us/blog/artificial-intelligence/agntcy-structure-the-internet-of-agents.html
  38. Mauro Sardara, SLIM v1.0: Secure Low-Latency Interactive Messaging for Agentic AI (AGNTCY Blogs), 2026-02-03, checked 2026-10-29: "While A2A defines what agents say (message formats, task semantics, coordination patterns), SLIM defines how these messages are securely delivered across distributed networks." "SLIM leverages the Message Layer Security (MLS) protocol (RFC 9420) to provide end-to-end encryption for all agent communications." — https://blogs.agntcy.org/technical/2026/02/03/slim-v1.html
  39. AGNTCY Blogs, SlimRPC Multicast: One Call, Every Agent, 2026-03-31, checked 2026-10-29: "Today we are releasing SlimRPC Multicast — also called Group RPC — as part of SLIM v1.3." — https://blogs.agntcy.org/technical/slim/agents/2026/03/31/slimrpc-multicast.html

JSON · Markdown · OKF v0.2