DoubleShot

When the retry works. Twice.

An interactive simulator showing what happens when an AI agent's retry logic fires on a non-idempotent operation. The agent reports success. The customer is charged twice.

Agent Failure Series #6 · Live demo →

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What It Shows

You're watching two views of the same operation:

AGENT VIEW	REALITY
1 API call (the retry "corrected" the first)	2 API calls (both executed)
HTTP 200 — succeeded	$198 charged / 2 emails / 2 orders
0 errors in logs	1 support ticket

The agent sees clean logs. The backend sees duplicates.

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The Three Scenarios

💳 Payment Processing

A Stripe charge call times out at 1,300ms. Retry fires. Both calls reach the processor. Neither has an idempotency key. Customer is charged $99 twice.

📧 Email Dispatch

A password reset email is queued. SMTP relay doesn't acknowledge in time. Retry generates a new token and sends again. Customer receives two emails with two different reset links — first link is now invalid.

📦 Order Placement

An e-commerce order write times out mid-transaction. Retry creates a second order. Warehouse fulfillment queue sees two orders for the same customer. $224 in goods shipped twice.

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Why Your Evals Miss This

Test environments use fast, reliable networks. Retries never trigger. Coverage shows 100%. Production has packet loss, cold-start latency, and overloaded dependencies.

The bug only appears at real-world p99 latencies — exactly when you can't afford it.

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The Fix

Every non-idempotent tool must accept an idempotency_key. Generate it once, before the first attempt. Pass it on every retry.

# Wrong: each retry generates a new request object
def charge_customer(amount):
    for attempt in range(3):
        try:
            return stripe.create_charge(amount=amount)  # no idempotency key
        except TimeoutError:
            continue

# Right: idempotency key generated once, shared across all retries
def charge_customer(amount, order_id):
    idempotency_key = f"charge_{order_id}_{amount}"
    for attempt in range(3):
        try:
            return stripe.create_charge(
                amount=amount,
                idempotency_key=idempotency_key  # same key every time
            )
        except TimeoutError:
            continue

Stripe, Braintree, Twilio, and modern email APIs all support this natively. If your internal API doesn't — that's the first thing to fix.

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Agent Failure Series

#	Name	Failure Mode	Demo
3	RaceFloor	Race conditions	Two agents, one resource, no coordination
4	ConfidenceGap	Silent HTTP 200 failures	The API says OK. The data wasn't saved.
5	PromptJack	Prompt injection	Malicious input hijacks agent behavior
6	DoubleShot	Retry amplification	The retry worked. Twice.

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Stack

Pure static HTML/CSS/JS — no build step, no framework, no dependencies. Self-contained single file. Open index.html in any browser.

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Built by Harel Asaf