What causes "Value must be less than or equal to one." in App-vNext/Polly?

Pass a ratio in (0,1]; divide percentages by 100.

App-vNext/Polly · error · ArgumentOutOfRangeException

Value must be less than or equal to one.

Error message

Value must be less than or equal to one.

What it means

Thrown by the async AdvancedCircuitBreaker syntax when failureThreshold exceeds 1. failureThreshold is a ratio, so >1 (>100% failures) is invalid. Fires at policy build time.

Source

Thrown at src/Polly/CircuitBreaker/AsyncAdvancedCircuitBreakerSyntax.cs:236

    public static AsyncCircuitBreakerPolicy AdvancedCircuitBreakerAsync(
        this PolicyBuilder policyBuilder,
        double failureThreshold,
        TimeSpan samplingDuration,
        int minimumThroughput,
        TimeSpan durationOfBreak,
        Action<Exception, CircuitState, TimeSpan, Context> onBreak,
        Action<Context> onReset, Action onHalfOpen)
    {
        var resolutionOfCircuit = TimeSpan.FromTicks(AdvancedCircuitController<EmptyStruct>.ResolutionOfCircuitTimer);

        if (failureThreshold <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(failureThreshold), "Value must be greater than zero.");
        }

        if (failureThreshold > 1)
        {
            throw new ArgumentOutOfRangeException(nameof(failureThreshold), "Value must be less than or equal to one.");
        }

        if (samplingDuration < resolutionOfCircuit)
        {
            throw new ArgumentOutOfRangeException(nameof(samplingDuration), $"Value must be equal to or greater than {resolutionOfCircuit.TotalMilliseconds} milliseconds. This is the minimum resolution of the CircuitBreaker timer.");
        }

        if (minimumThroughput <= 1)
        {
            throw new ArgumentOutOfRangeException(nameof(minimumThroughput), "Value must be greater than one.");
        }

        if (durationOfBreak < TimeSpan.Zero)
        {
            throw new ArgumentOutOfRangeException(nameof(durationOfBreak), "Value must be greater than zero.");
        }

        if (onBreak == null)

View on GitHub (pinned to d0e46bdb1e)

Solutions

Pass a ratio in (0,1]; divide percentages by 100.
Clamp the configured value into (0,1] at startup.

Example fix

// before
.AdvancedCircuitBreakerAsync(failureThreshold: 75, ...)

// after
.AdvancedCircuitBreakerAsync(failureThreshold: 0.75, ...)

Defensive patterns

Strategy: validation

Validate before calling

if (failureThreshold is <= 0 or > 1)
    throw new ArgumentOutOfRangeException(nameof(failureThreshold), "failureThreshold must be in (0,1].");

Type guard

static bool IsValidFailureThreshold(double t) => t > 0 && t <= 1;

Prevention

Convert percentage config to a ratio at the binding boundary.
Add an assertion test that construction succeeds with 1.0 and fails above it.
Keep one validation helper shared across sync/async/generic overloads.

When it happens

Trigger: Calling AdvancedCircuitBreakerAsync(failureThreshold: 100, ...) expecting percent semantics. The check is `failureThreshold > 1`.

Common situations: Passing a percentage integer (50, 100) instead of a fraction (0.5, 1.0).

Related errors

AI-assisted analysis of App-vNext/Polly@d0e46bdb1e (2026-08-13). Data as JSON: /api/errors/d1b9b9c3b0524e12. Report an issue: GitHub.