Think prix fixe means you’re locked in? Think again. While Restaurant Week Boston menus offer plenty of value on their own, lots of participating restaurants give diners the chance to customize their experience with add-ons and upgrades – everything from premium cuts and seafood to caviar and foie gras.

If you’re looking to indulge, there are plenty of ways to do it. Upgrade to coveted A5 Wagyu at any Gyu-Kaku location (Brookline, Burlington, Cambridge or Dorchester) during dinner, add seared foie gras at The Block at Woods Hill or add a dollop of caviar to your meal at The Berkeley. At Zuma, you can swap in a vibrant chirashi donburi at lunch, while Boqueria puts a sweet spin on customization with upgraded churro dipping sauces.

Steakhouses are getting in on the fun, too. Smith & Wollensky, The Capital Grille and Eddie V’s all offer premium cuts and upgraded entrées for guests looking to splurge, while Ocean Prime lets you layer on decadent additions like lobster tail, black truffle or black garlic butter and garlic shrimp scampi.

Not every upgrade has to break the bank, though. Add a grilled swordfish skewer at Bar Volpe for just $3, spring for a cheese course at Batifol or Petit Robert or elevate your meal with premium nigiri at any Fuji location (Somerville, Cambridge, South End, Newton and Quincy).

Whether you’re after a once-a-year splurge or just looking to personalize your prix fixe meal, these thoughtful add-ons prove Restaurant Week is anything but one-size-fits-all. Browse the Insider’s Guide to Restaurant Week to start planning your outings, and keep an eye out for exclusive upgrades as you’re perusing menus.