Suspend the agent’s high-risk access, preserve the prompt and tool-call trail, and review the inputs that may have redirected its behaviour. Containment should happen before the session continues, because the same trust failure can propagate through every subsequent action.
Why immediate containment comes first
An AI agent that is behaving unpredictably should be treated as a live trust failure, not as a debugging exercise in progress. The first job is to stop further autonomous action while preserving evidence, because continued execution can widen the blast radius through additional tool calls, data access, or irreversible side effects.
That is why containment belongs before investigation. Teams need to separate the agent from high-risk permissions, suspend any active session or delegated access path, and keep the environment stable enough to examine what happened without letting the same failure keep propagating.
In practice, the most important question is not “what caused the odd behaviour?” but “what can this agent still do if we let it continue?” The answer determines whether the immediate response should be a hard stop, a scoped restriction, or a fully controlled handoff to a human operator.
What evidence to preserve and why it matters
The most useful artefacts are the prompt history, tool-call trail, intermediate outputs, policy decisions, and any context inputs that may have shifted the agent’s behaviour. Those records show whether the failure came from malicious input, confused instructions, a bad tool response, or an overbroad permission boundary.
For agent-heavy environments, observability is part of the control plane, not a post-incident luxury. NHIMG’s AI Agent Observability, Audit and Incident Response Guide is useful here because it focuses on attribution, kill-switch design, and the signals that show an agent has gone wrong.
Preservation should also include any external trust inputs that may have redirected the agent, such as retrieved content, user instructions, or tool responses. If those inputs are not retained, teams lose the ability to distinguish a genuine logic error from prompt injection, context poisoning, or a misleading downstream tool result.
How teams should contain the agent safely
The containment step should match the agent’s authority profile. A low-impact assistant may only need its current session terminated, while a production-facing agent may require credential revocation, tool isolation, and temporary disablement of the integration that lets it act.
NHIMG’s AI Agent Authorisation Guide is directly relevant because it frames task-scoped and just-in-time access, per-action policy decisions, and human approval as the baseline for limiting damage when behaviour becomes uncertain.
The containment choice should be driven by the highest-risk action the agent can still perform, not by the probability that it will repeat the bad behaviour. If a session token, tool credential, or delegated grant can still reach production systems, that path should be cut first. Only after the agent is fenced in should the team start tracing the root cause.
Risk and Threat Considerations
Unpredictable agent behaviour can turn a single bad instruction, poisoned context, or mis-scoped permission into rapid downstream exposure. Once an agent continues acting after trust has failed, it may exfiltrate data, trigger destructive tool calls, or amplify a bad decision across multiple systems before anyone notices.
Failure mechanism: The agent keeps operating with standing access after its inputs, policy state, or tool context have become unsafe, so every subsequent action inherits the original trust failure.
Impact: The result can be wider data exposure, unauthorized actions, broken auditability, and a much harder recovery because the incident has already propagated through legitimate tooling.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Agentic AI Top 10 addresses the attack and risk surface, while NIST SP 800-53 Rev 5 sets the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Agentic AI Top 10 | ASI03 — Identity & Privilege Abuse | Unpredictable agent behaviour often reflects unsafe authority or privilege use. |
| ASI02 — Tool Misuse | The issue centers on stopping harmful or unexpected tool actions quickly. | |
| ASI06 — Memory & Context Poisoning | Preserving prompts and inputs helps determine whether context manipulation redirected the agent. | |
| Recommendation — Constrain the agent’s authority and review any overbroad privilege paths before resuming. Disable the affected tool path and inspect recent tool invocations for unsafe use. Preserve context traces and check for poisoned or misleading inputs before re-enabling the agent. | ||
| NIST SP 800-53 Rev 5 | AU-2 — Audit Events | Prompt and tool-call trails are audit evidence needed to reconstruct the event. |
| AC-6 — Least Privilege | Immediate containment depends on removing excessive standing access from the agent. | |
| IA-5 — Authenticator Management | If a live token or credential can still act, it must be revoked to stop further damage. | |
| Recommendation — Retain the relevant audit trail so the agent’s actions can be reconstructed accurately. Reduce the agent to the minimum permissions needed, or revoke access entirely during investigation. Revoke or rotate any credential that still lets the agent reach sensitive systems. | ||
Practitioner Guidance
What to prioritise: Contain first, investigate second. If the agent has any path to sensitive systems, suspend that path before you spend time diagnosing the cause of the anomaly.
What to verify: Confirm that the session, delegated credential, or tool permission is actually inactive after the stop action. A partial shutdown that leaves a live token or integration in place is not real containment.
Common mistake: Teams often keep the agent running “just long enough” to gather more evidence. That usually trades away control for convenience and can turn a recoverable event into an incident with a larger blast radius.
Practitioner takeaway: Treat unpredictability as a boundary problem, not a curiosity problem. The safest default is to remove the agent’s ability to act, preserve the evidence, and only then decide whether the cause was input poisoning, misconfiguration, or over-privilege.