Ask Claude to Harden Your Happy-Path Code by Adding Error Handling for Every Failure Mode

Code that works perfectly in development falls apart in production because real-world conditions are messy. Claude reads your happy-path implementation and systematically adds error handling for every way things can go wrong.

> read the checkout flow in app/Services/CheckoutService.php and
> add error handling for every failure mode — what happens if the
> payment provider is down, the user's cart is empty, the product
> is out of stock, or the database write fails?

Claude traces every operation that can fail — external API calls, database queries, file operations, user input — and wraps each one with appropriate error handling that's specific to the failure, not just a generic catch-all.

Before Claude:

$charge = $stripe->charges->create(['amount' => $total]);
$order = Order::create(['user_id' => $user->id, 'total' => $total]);
Mail::send(new OrderConfirmation($order));

After Claude:

try {
    $charge = $stripe->charges->create(['amount' => $total]);
} catch (CardException $e) {
    return response()->json(['error' => 'Your card was declined.'], 422);
} catch (ApiConnectionException $e) {
    Log::error('Stripe unreachable', ['error' => $e->getMessage()]);
    return response()->json(['error' => 'Payment service temporarily unavailable.'], 503);
}

$order = Order::create(['user_id' => $user->id, 'charge_id' => $charge->id]);

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

Notice how Claude makes different decisions for each failure — the payment failure blocks the checkout, but the email failure is logged and swallowed because the order already succeeded.

You can target specific areas:

> add timeout handling to every external HTTP call in this service

> add null checks for all the optional relationships this
> controller accesses — user->profile, user->subscription, etc.

> wrap the file upload in error handling — check file size,
> mime type, disk space, and permissions before writing

Happy-path code is a first draft. Error handling is what makes it production-ready — let Claude add it before your users find the gaps.

via Claude Code