Struct GuardrailHook 

pub struct GuardrailHook { /* private fields */ }

An ObservabilityHook that runs guardrails on LLM input and output.

Built with a builder pattern. Input guardrails fire on HookEvent::PreLlmCall, output guardrails fire on HookEvent::PostLlmCall. All other events pass through with HookAction::Continue.

Guardrail result mapping

• GuardrailResult::Pass -> HookAction::Continue
• GuardrailResult::Tripwire -> HookAction::Terminate with the reason
• GuardrailResult::Warn -> logs a warning via tracing::warn! and continues

Example

use neuron_runtime::{GuardrailHook, InputGuardrail, OutputGuardrail, GuardrailResult};

struct NoSecrets;
impl InputGuardrail for NoSecrets {
    fn check(&self, input: &str) -> impl Future<Output = GuardrailResult> + Send {
        async move {
            if input.contains("sk-") {
                GuardrailResult::Tripwire("secret in input".to_string())
            } else {
                GuardrailResult::Pass
            }
        }
    }
}

let hook = GuardrailHook::new()
    .input_guardrail(NoSecrets);

Implementations

impl GuardrailHook

pub fn new() -> Self

Create an empty GuardrailHook with no guardrails.

pub fn input_guardrail<G>(self, guardrail: G) -> Self

where G: ErasedInputGuardrail + 'static,

Add an input guardrail.

Input guardrails run on HookEvent::PreLlmCall, checking the last user message text in the request.

pub fn output_guardrail<G>(self, guardrail: G) -> Self

where G: ErasedOutputGuardrail + 'static,

Add an output guardrail.

Output guardrails run on HookEvent::PostLlmCall, checking the assistant response text from the response message.

Trait Implementations

impl Default for GuardrailHook

fn default() -> Self

Returns the “default value” for a type.

impl ObservabilityHook for GuardrailHook

fn on_event( &self, event: HookEvent<'_>, ) -> impl Future<Output = Result<HookAction, HookError>> + WasmCompatSend

Called for each event in the agentic loop.