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Failure posture

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What a guardrail, guardian agent or tool gateway does when it cannot reach a decision: fail open lets the call through, fail closed blocks it. The reference guardian of the OWASP Agent Control Standard starts at proceed unless set to deny 1. The posture is a governance decision, set per operation class and recorded in the agent's Policy Card.

Developed in
ch. 23, Runtime guardrails for tool calls
Chapters
ch. 23, AI Agents
Source
1 numbered reference, listed below

Where it is used

One chapter of the Body of Knowledge uses the term. Each link opens the first section that does.

  • Guardian agent

    An AI agent whose job is to supervise, check or constrain other agents at runtime; Gartner predicts guardian-agent technologies will account for at least 10…

  • Guardrail

    A runtime control that inspects or mediates a model's or agent's inputs, outputs or tool calls and blocks, rewrites or escalates what breaks a policy, logging…

  • Policy Card

    A JSON-schema, machine-readable governance artefact that declares an agent's allowed and forbidden behaviours for runtime enforcement.

Sources

  1. [1] Agent Control Standard (ACS) repository (a wire specification that lets a separate guardian agent permit, deny or modify an agent's action before it happens; the reference guardian's failure posture defaults to proceed, overridable to deny; donated to the OWASP GenAI Security Project, announced 1 Sep 2026). OWASP GenAI Security Project (GitHub). 2026-09-01. https://github.com/GenAI-Security-Project/agent-control-standard (verified: primary)

Definitions of legal terms paraphrase the cited text, which governs. Dated statements are as of .

Cite this term

García Aibar, J. (2026). Failure posture. In AI Governance Engineering: The Thesis & Body of Knowledge (v0.5.0), Glossary. https://doi.org/10.5281/zenodo.22956197. https://aigovernanceengineer.com/glossary/failure-posture. CC BY 4.0

BibTeX

@misc{aige2026failureposture,
  author  = {Jorge García Aibar},
  title   = {{Failure posture}},
  note    = {Glossary, AI Governance Engineering: The Thesis \& Body of Knowledge, version 0.5.0},
  year    = {2026},
  doi     = {10.5281/zenodo.22956197},
  url     = {https://aigovernanceengineer.com/glossary/failure-posture}
}