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Dictionary

Guardrails

Runtime checks that constrain LLM inputs and outputs to keep behavior safe and on-spec.

1 min readupdated 2026-06-21

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Guardrails are programmatic policies wrapped around an LLM: input filters (PII, prompt-injection detection), output validators (schema, toxicity, factuality), and fallback behaviors. They turn a probabilistic model into a system you can ship to production with predictable failure modes. Runtime checks that constrain LLM inputs and outputs to keep behavior safe and on-spec.

Runtime checks that constrain LLM inputs and outputs to keep behavior safe and on-spec. Guardrails are programmatic policies wrapped around an LLM: input filters (PII, prompt-injection detection), output validators (schema, toxicity, factuality), and fallback behaviors. They turn a probabilistic model into a system you can ship to production with predictable failure modes. In practice: Before a support agent sends a reply, a guardrail strips customer PII from logs, validates the reply matches a JSON schema, and blocks responses that violate the refund policy.
Definition
Guardrails are programmatic policies wrapped around an LLM: input filters (PII, prompt-injection detection), output validators (schema, toxicity, factuality), and fallback behaviors. They turn a probabilistic model into a system you can ship to production with predictable failure modes.
Example
Before a support agent sends a reply, a guardrail strips customer PII from logs, validates the reply matches a JSON schema, and blocks responses that violate the refund policy.
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What is Guardrails?

Guardrails are programmatic policies wrapped around an LLM: input filters (PII, prompt-injection detection), output validators (schema, toxicity, factuality), and fallback behaviors. They turn a probabilistic model into a system you can ship to production with predictable failure modes.

What is an example of Guardrails?

Before a support agent sends a reply, a guardrail strips customer PII from logs, validates the reply matches a JSON schema, and blocks responses that violate the refund policy.

Why does Guardrails matter?

Runtime checks that constrain LLM inputs and outputs to keep behavior safe and on-spec.

What should I learn after Guardrails?

Open the related workflows and prompts further down this page: they show how this idea is applied in a real task, step by step.

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