The open standards that let agents, editors, tools, and frontends interoperate, stacking from wire transport up to interface events.
- A2A - Google’s open protocol for independent agents to interoperate, now under the Linux Foundation.
- A2UI - Google’s declarative generative-UI format that agents speak so clients render native interfaces from trusted component catalogs, v0.9.1 in production with v1.0 a release candidate.
- ACP - Zed’s protocol standardizing how editors talk to coding agents.
- AG-UI - CopilotKit’s agent-to-frontend event protocol, 1.0 since September 2026 with about 17.0 million monthly npm downloads, the rendering half of the protocol stack.
- Agent Host Protocol - Microsoft’s sessions-server spec with six-language SDKs, VS Code rebuilding its agent infrastructure on it, spec at v1.0.0 since 2026-10-02.
- Agent Protocol (LangChain) - LangChain’s MIT-licensed REST/OpenAPI serving spec for running agents in production (agents, threads, runs), which LangGraph Platform implements as a commercial superset.
- AGENTS.md - the open convention for repo-level agent instruction files.
- ANP - the community DID-based agent-interop suite betting on open-web agent discovery, specs at 1.2 with almost no adoption yet.
- llms.txt - the Answer.AI site-content-index convention for agents, at v2 since August 2026 with link-relation discovery, adopted by docs platforms and coding agents while search crawlers ignore it.
- MCP - the open protocol standardizing how AI applications connect to tools and data.
- PIC Standard - the Apache-2.0 pre-execution gating contract: agents prove intent, provenance, and evidence in signed proposals before high-impact tool calls, verified fail-closed locally, v0.9.0 with two implementations.
- Unified Harness Protocol (UHP) - the Responses-compatible HTTP draft for driving coding-agent harnesses as shared infrastructure, at its fourth version since August 2026 with HarnessRouter and SuperQode as the recorded implementations.
- WebMCP - the W3C Community Group draft that turns a web page into an MCP-style tool provider through
document.modelContext, in Chrome origin trial with Shopify and Cloudflare default-on.
Its members are compared on shared rows in the Protocols Feature Matrix.
Changes #
- 2026-08-24 - Added A2A.
- 2026-08-24 - Added ACP.
- 2026-08-24 - Added AGENTS.md.
- 2026-08-24 - Added MCP.
- 2026-08-30 - Added Agent Host Protocol.
- 2026-09-16 - Added AG-UI.
- 2026-10-05 - Added Agent Network Protocol (ANP).
- 2026-10-06 - Added A2UI.
- 2026-10-06 - Added WebMCP.
- 2026-10-07 - Added Agent Protocol (LangChain).
- 2026-10-07 - Added llms.txt.
- 2026-10-08 - Added Unified Harness Protocol (UHP).
- 2026-10-11 - Added PIC Standard.