resilience

A guide to Polly, a .NET library for making HTTP calls more tolerant of temporary failures.

In plain words
What is it for?
Use it to configure retries, timeouts, circuit breakers, and limits for HTTP clients.
Why use it?
It helps applications handle slow or unavailable external services without failing immediately or repeatedly overwhelming them.

Cursor rule for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/goranerhartic/cursor-development-rules/resilience
Clone the repo
git clone --depth 1 https://github.com/GoranErhartic/cursor-development-rules

Made for: Cursor.

Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 741 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00017 $0.00741
Opus 5 $0.00009 $0.00370
Sonnet 5 $0.00003 $0.00148
Haiku 4.5 $0.00002 $0.00074

Measured 2d ago against content hash 997d951bc4cd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

resilience scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/languages/csharp/resilience.mdc · 109 lines

How it starts

The opening of the file, as written. The whole thing — 109 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Polly Resilience Patterns

HttpClient with Polly (.NET 10)

builder.Services.AddHttpClient<IPaymentGateway, PaymentGateway>(client =>
{
    client.BaseAddress = new Uri(builder.Configuration["PaymentGateway:BaseUrl"]!);
    client.Timeout = TimeSpan.FromSeconds(30);
})
.AddStandardResilienceHandler();

// Or with custom configuration
builder.Services.AddHttpClient<IExternalApi, ExternalApiClient>()
    .AddResilienceHandler("custom", builder =>
    {
        builder
            .AddRetry(new HttpRetryStrategyOptions
            {
                MaxRetryAttempts = 3,
                Delay = TimeSpan.FromMilliseconds(500),
                BackoffType = DelayBackoffType.Exponential,
                ShouldHandle = new PredicateBuilder<HttpResponseMessage>()
                    .Handle<HttpRequestException>()
                    .HandleResult(r => r.StatusCode >= HttpStatusCode.InternalServerError)
            })
            .AddCircuitBreaker(new HttpCircuitBreakerStrategyOptions
            {
                FailureRatio = 0.5,
                SamplingDuration = TimeSpan.FromSeconds(10),
                MinimumThroughput = 5,
                BreakDuration = TimeSpan.FromSeconds(30)
            })
            .AddTimeout(TimeSpan.FromSeconds(10));
    });

Resilience Strategies

Retry

.AddRetry(new RetryStrategyOptions<HttpResponseMessage>
{
    MaxRetryAttempts = 3,
    Delay = TimeSpan.FromMilliseconds(200),
    BackoffType = DelayBackoffType.Exponential,
    UseJitter = true, // Prevents thundering herd
    OnRetry = args =>
    {
        _logger.LogWarning("Retry {Attempt} after {Delay}ms", 
            args.AttemptNumber, args.RetryDelay.TotalMilliseconds);
        return ValueTask.CompletedTask;
    }
})

Circuit Breaker

.AddCircuitBreaker(new CircuitBreakerStrategyOptions<HttpResponseMessage>
{
    FailureRatio = 0.5,           // 50% failure rate triggers break
    SamplingDuration = TimeSpan.FromSeconds(10),
    MinimumThroughput = 10,       // Minimum requests before evaluating
    BreakDuration = TimeSpan.FromSeconds(30),
    OnOpened = args =>
    {
        _logger.LogError("Circuit breaker opened for {Duration}", args.BreakDuration);
        return ValueTask.CompletedTask;
    }
})

Read the full file on GitHub · 109 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 109 lines · 17 tokens per session scan A 997d951bc4cd

Subscribe to this mod's changes

resilience is a cursor rule published in the GitHub repository GoranErhartic/cursor-development-rules (19 stars, last pushed 6mo ago), licensed MIT. It adds 17 tokens to every session and 741 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.