# ACS vs AOS > Clarifying the relationship between Agent Control Standard and Agent Observability Standard - **Category**: guardrails-acs - **Canonical URL**: https://designpattern.fyi/guardrails-acs/acs-vs-aos/ --- ## Description Clarifying the relationship between Agent Control Standard and Agent Observability Standard ## Additional Notes # What ACS Actually Is — and How It Relates to AOS ## The Naming Confusion This is worth being precise about, because the two names get used almost interchangeably in vendor content, and there's a second, unrelated naming collision to watch for. ### The Agent Observability Standard (AOS) - **Status:** OWASP-incubated open specification (Apache 2.0) - **Hosted at:** [aos.owasp.org](https://aos.owasp.org) - **GitHub:** `trustworthyagents` organization, mirrored at `OWASP/www-project-agent-observability-standard` - **Definition:** Defines the technical contract — the hook methods, event schemas, verdict objects, and extensions to OpenTelemetry, OCSF, CycloneDX, SPDX, and SWID that make an agent "instrumentable, traceable, and inspectable" ### The Agent Control Standard (ACS) - **Status:** Applied, governance-framed expression of the AOS specification - **Launch:** v0.1.0 on May 27, 2026, announced at AI Agent Security Summit in San Francisco - **GitHub:** `Agent-Control-Standard/ACS` (MIT-licensed) - **Definition:** The runtime-governance framing, reference architecture (Guardian Agent pattern, three-tier control model), and community push built on top of AOS --- ## The Structural Relationship ### ACS as a Fork of AOS The ACS repository is, structurally, a fork of the OWASP AOS repository: - The rationale, key components, and version roadmap are close to identical across both projects - ACS's own site points back to `aos.owasp.org` as "the Specification" - Licensing differs (Apache 2.0 for the OWASP repo, MIT for the ACS repo) - Both are community-governed with no single vendor owning the spec ### Key Contributors The initiative is coordinated by contributors including: - **Michael Bargury** — co-creator of ACS, co-founder and CTO of Zenity (AI-agent-security firm) - **Rock Lambros** — director of AI standards and governance at Zenity - A broader community of founding contributors ### The Launch Philosophy As Bargury put it at launch: > "Governance cannot rely on soft guardrails or wishful system prompts." This statement captures the ACS philosophy: runtime enforcement, not just documentation or guidelines. --- ## The Practical Takeaway ### Treat AOS as the Specification AOS provides the technical foundation: - Hook methods and event schemas - Verdict objects and response shapes - Extensions to OpenTelemetry, OCSF, CycloneDX, SPDX, and SWID - The "instrumentable, traceable, and inspectable" contract ### Treat ACS as the Governance Framing ACS provides the implementation guidance: - Reference architecture (Guardian Agent pattern) - Three-tier control model - Implementation roadmap and best practices - Community governance and ecosystem ### When You Implement "ACS" When you implement "ACS," you are: - Implementing AOS's instrument/trace/inspect contract - With a control-plane mindset - Following the ACS reference architecture - Participating in the ACS community governance --- ## The Microsoft Naming Collision ### A Separate "Agent Control Specification" Microsoft introduced its own, similarly-named **"Agent Control Specification"** as part of its Build 2026 Agent Governance Toolkit: - **Distinct effort** with a different set of interception points - **Not affiliated** with the OWASP/Zenity-led ACS covered in this guide - **Different architecture** and implementation approach ### Why This Matters Some early blog coverage conflates the two, leading to confusion: | Aspect | OWASP/Zenity ACS | Microsoft ACS | |---|---|---| | **Governance** | Community-led (OWASP, Zenity) | Microsoft-controlled | | **Specification** | Built on AOS | Independent specification | | **Licensing** | MIT + Apache 2.0 (AOS) | Microsoft's licensing terms | | **Interception Points** | AOS hook methods | Microsoft-defined hooks | | **Ecosystem** | Open-source community | Microsoft ecosystem | ### Recommendation When you read vendor material referencing "ACS," confirm which one is meant: - Check if it references [aos.owasp.org](https://aos.owasp.org) or [agentcontrolstandard.org](https://agentcontrolstandard.org) - Look for mentions of OWASP or Zenity - Verify the GitHub repository being referenced --- ## AOS vs ACS: A Practical Mapping | Layer | AOS (Specification) | ACS (Governance) | |---|---|---| | **Technical Contract** | Hook methods, event schemas, verdict objects | Uses AOS specification | | **Observability** | OpenTelemetry extensions, OCSF mapping | Implements AOS tracing | | **Inventory** | CycloneDX/SPDX/SWID extensions | AgBOM implementation guidance | | **Architecture** | Core concepts (Observed Agent, Guardian Agent) | Reference architecture patterns | | **Implementation** | Technical definitions | 12-step implementation guide | | **Governance** | OWASP community governance | ACS community governance | | **Ecosystem** | Framework integrations | Enterprise deployment patterns | --- ## Key Takeaways 1. **AOS is the specification** — the technical contract for making agents instrumentable, traceable, and inspectable 2. **ACS is the governance framing** — the reference architecture and implementation guidance built on AOS 3. **ACS is structurally a fork of AOS** — they share the same technical foundation and roadmap 4. **The Microsoft naming collision is real** — verify which "ACS" vendor material is referencing 5. **When implementing ACS, you're implementing AOS** — with a control-plane mindset and governance framing --- ## Next Steps - **Three Pillars** — understand the core AOS concepts that ACS builds upon - **Three-Tier Architecture** — see the ACS reference architecture - **Implementation Guide** — follow the step-by-step deployment process