The trip plans backwards from the dinner, and the restaurant pick is the most-binding constraint — not just because all five carry a 2–3 month lead time for May–October bookings, but because each of the five stars sits in a different micro-geography that decides the rest of the day. Akelarre is on top of Monte Igueldo; you ride the 1912 funicular up there at sunset anyway, so the dinner doubles as the panorama. Arzak is in Gros, walkable from a Zurriola surf lesson at Pukas and a stop at Bar Bergara on the way. Amelia is inside Hotel Villa Favorita directly on La Concha — pair with La Perla thalasso and a Monte Urgull loop. Mugaritz in Errenteria sits on the E20 bus line via Pasaia, so the Camino del Faro de la Plata cliff path to Pasai Donibane becomes the natural afternoon. Berasategui in Lasarte-Oria is the outlier with no walking pairing — a 15–20 min taxi each way and that’s it; book it for the technique, not the day plan.
The closures map is the second filter, and it’s strict enough to invalidate a naive itinerary. Avoid Mondays: most pintxo bars and San Telmo Museoa close; Chillida-Leku is closed Tue–Wed; Berasategui serves Wed–Sun only; and Mugaritz runs May 1 – October 25 only. Late May — the date of this run — is also Donostia’s tactical shoulder: the official txotx sidrería season ended May 3 so Astigarraga needs a year-round house like Petritegi (€44.50), and the Santa Clara motora is on reduced service until 1 June so paddle yourself across with AloKayak instead.
If the dates are flexible, the IT-conference layer is a real lever rather than a footnote. EuskalHack Security Congress IX, 19–20 June at Olarain, is the next pairable event and falls inside Mugaritz’s open window — a clean Friday-talks + Saturday-dinner stack with the venue on Paseo de Ondarreta, walkable from the bay. Zinemaldia & Technology, 18–26 September during the 74th Film Festival, inverts the booking order: lodging vanishes and prices spike during the festival, so the Michelin slot has to be chosen around the festival window, not vice versa. Donostia Week-INN in November is the only autumn anchor with city-wide programming, but it lands after Mugaritz closes — drop to the three-star shortlist plus Amelia.
What this run does not decide for you is which restaurant to book. Pick that first — date, neighborhood, and at least one afternoon’s category fall out of it automatically.