Agent-to-agent trust

Expanded Definition

Agent-to-agent trust describes the policy and technical conditions under which one NIST AI Risk Management Framework view of an AI system can safely permit another agent to authenticate, delegate actions, or receive shared context. In practice, it spans identity proofing, credential scope, session duration, consent boundaries, and the rules that decide whether an agent may act on behalf of another agent.

Definitions vary across vendors because some products treat this as a workflow feature, while others frame it as federated identity for autonomous systems. In NHI terms, the distinction matters: an agent is not just an integration client, but an entity with execution authority, tool access, and the ability to create downstream trust chains. That makes agent-to-agent trust closely related to OWASP Agentic AI Top 10 guidance on unauthorized action propagation and to the governance concerns highlighted in OWASP NHI Top 10. The most common misapplication is treating delegation like ordinary service-to-service integration, which occurs when an agent is allowed to inherit trust without explicit policy checks.

Examples and Use Cases

Implementing agent-to-agent trust rigorously often introduces latency and policy overhead, requiring organisations to weigh autonomous coordination against tighter control of delegated authority.

• An orchestration agent requests a planning agent to summarise a ticket, but the trust policy limits context sharing to non-sensitive fields and short-lived sessions.
• A coding agent can invoke a testing agent only after identity verification and scoped consent, reducing the chance that a compromised agent can pivot into build systems. NHI teams often review this pattern alongside lessons from the Analysis of Claude Code Security.
• A support agent delegates to a retrieval agent for customer history, but NIST AI Risk Management Framework principles require a clear boundary around what data may be returned and how it is logged.
• A multi-agent workflow permits only one agent to mint a transient token for another, using just-in-time authorization rather than standing access, which aligns with zero standing privilege design.
• Security reviewers trace whether trust was established by human approval, policy engine decision, or automatic agent inference, because those paths carry very different audit and containment implications. The OWASP Agentic Applications Top 10 is useful when evaluating those propagation paths.

Why It Matters in NHI Security

Agent-to-agent trust becomes a security issue whenever one compromised agent can multiply access across systems, especially when secrets, tokens, or context bundles are passed without tight expiry or audience restrictions. That is why NHI governance treats it as an identity control problem, not just an API design choice. NHI Mgmt Group research shows that Ultimate Guide to NHIs — 2025 Outlook and Predictions reports only 5.7% of organisations have full visibility into their service accounts, which means hidden agent trust paths are often invisible until incident response begins.

Unchecked trust propagation also complicates accountability. If one agent can delegate to another without explicit policy, investigators may not be able to prove which entity made a harmful decision or accessed a protected secret. That risk is amplified in environments already exposed to the patterns described in AI LLM hijack breach reporting and in broader OWASP NHI Top 10 risk analysis. Organisations typically encounter the operational impact only after an agent misuse event or lateral movement investigation, at which point agent-to-agent trust becomes unavoidable to unwind.

Related resources from NHI Mgmt Group

• AI Agent Authentication
• How do trust registries help AI agent and NHI governance?
• Human-Agent Trust Exploitation (ASI09)
• Inter-Agent Trust Protocol (IATP)