Ask Claude to Add Error Handling to Code That Only Covers the Happy Path

First drafts of code usually handle the success case and nothing else. That works until it doesn't — and "it doesn't" always happens in production. Claude reads your happy-path code and adds the error handling it needs.

"Read the checkout flow and add error handling for every failure mode"

Claude traces each step that can fail — network calls, database writes, payment processing, email sending — and wraps them with proper error handling:

// Before: happy path only
$charge = $stripe->charges->create($params);
$order->update(['status' => 'paid']);
Mail::send(new OrderConfirmation($order));

// After: Claude adds real error handling
try {
    $charge = $stripe->charges->create($params);
} catch (CardException $e) {
    return back()->with('error', 'Your card was declined. Please try another.');
} catch (ApiException $e) {
    Log::error('Stripe API error', ['error' => $e->getMessage()]);
    return back()->with('error', 'Payment processing is temporarily unavailable.');
}

$order->update(['status' => 'paid']);

try {
    Mail::send(new OrderConfirmation($order));
} catch (Throwable $e) {
    Log::warning('Order confirmation email failed', ['order' => $order->id]);
    // Don't fail the checkout — the order succeeded
}

You can focus on specific types of failures:

# External service failures
"Add error handling for when the API is down, slow, or returns unexpected data"

# Database errors
"Handle constraint violations, deadlocks, and connection timeouts in the repository layer"

# User input edge cases
"Add validation and error handling for all the ways user input can be wrong or malicious"

# Graceful degradation
"Make the dashboard work even when the analytics service is unavailable — show cached data or a helpful message"

Claude distinguishes between errors that should block the operation and ones that should be logged but not stop the flow — a failed notification shouldn't cancel a successful purchase.

The happy path is a demo. Error handling is what makes it production code — let Claude add the safety nets you forgot.

via Claude Code