Builder Base Bonanza runs May 17–31, 2026 with 50% off all upgrade costs and timers plus a 4x Star Bonus. Here's what's discounted, the exact upgrade priority sequence, and how to use the event to unlock B.O.B. faster than any other window in CoC history.
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Builder Base Finally Has Its Own Hammer Jam — And It's Better Than Expected
I've been sitting on two Builder Base hero levels for two months because the cost-to-value ratio at full price made me keep delaying them. That changes on May 17. Builder Base Bonanza is exactly what it sounds like — a 50% reduction across all upgrade costs and timers in Builder Base, combined with a 4x Star Bonus that makes resource farming faster than it's been in years. The community is already calling it Builder Base Hammer Jam, and honestly, the comparison holds up. This is the event where you cash in on whatever you've been putting off.
The event runs May 17 to May 31, 2026, which means 14 days of discounted upgrades, accelerated timers, and faster resource cycling. It celebrates nine years since Builder Base was first introduced, and Supercell delivered something genuinely impactful for the occasion rather than the usual cosmetic milestone event. If you have been delaying Builder Base upgrades because of long timers or expensive hero levels, this is the window. Don't log in on May 17 without a queue planned. For Gems to keep Builders active or grab the Gold Pass discount stack, LootBar has competitive rates worth checking before buying in-game.
Builder Base Bonanza — Full Event Overview
Detail | Builder Base Bonanza — Skeleton Kingdom Season |
Event Window | May 17 – May 31, 2026. Celebrating nine years since Builder Base was first introduced |
Upgrade Cost Reduction | 50% off ALL Builder Base upgrade costs — buildings, defenses, heroes, Star Laboratory research, and walls |
Upgrade Timer Reduction | 50% off ALL Builder Base upgrade timers — same scope as cost reduction. Builders free up twice as fast as normal |
Star Bonus Multiplier | 4x Builder Base Star Bonus — resource farming from battles produces 4x normal yield. Largest resource acceleration of the event |
Event Tasks | Rotating challenges every 5 days — rewards include Builder Star Jars, Clock Tower Potions, and Rune of Builder Elixir |
Key Use Case | Fastest B.O.B. (6th Builder) grind the game has ever offered — hero upgrades, troop research, and building timers all discounted simultaneously |
Gold Pass Stacking | Gold Pass adds 20% builder and research discounts on top of the 50% event discount — time resource dumps for when both are active simultaneously |
Running Alongside | Clan Games (May 22–28): additional resource window mid-event. Unlimited Dragon Duke (May 27–31): use Dragon Duke during upgrades at full power |
Bone Idol Deco | Available May 18–31 in the Shop — 3x3 Super Deco that sprouts a fresh artifact with every tap. Skeleton Kingdom aesthetic, cosmetic only |
Context | Described by community as 'Builder Base Hammer Jam' — the equivalent impact for Builder Base that Hammer Jam has for Home Village |
Everything That Gets the 50% Discount
The discount applies broadly — here's the full scope and priority breakdown:
Category | Cost Discount | Timer Discount | Priority for Max |
Builder Base Buildings | 50% off | 50% off | High — all buildings discounted, no exceptions |
Builder Base Defenses | 50% off | 50% off | High — push highest-level defenses first for BH progression |
Builder Base Heroes (Battle Machine, B.B. Royal Champion) | 50% off | 50% off | Highest — hero levels are the most expensive and time-consuming upgrades normally |
Star Laboratory Research | 50% off | 50% off | High — research timers can be days normally. Half-time makes this achievable in one event window |
Builder Base Walls | 50% off | 50% off | Medium — upgrade walls after heroes and buildings are prioritized |
B.O.B. (6th Builder) Requirements | Costs reduced via hero/research discounts | Timers halved — B.O.B. grind significantly faster | Critical — the event makes B.O.B. unlock requirements dramatically more achievable |
The scope of the discount is unusually comprehensive. Previous boost events often carved out exceptions for specific upgrade types. Builder Base Bonanza applies the reduction to buildings, defenses, heroes, research, and walls simultaneously. The only thing not discounted is the Gem rush option, which was never worth using at full price and isn't worth using during the event either.
B.O.B. (6th Builder) — Why Now Is the Time
B.O.B. — the Builder Machine Bot, your sixth builder for the Home Village — is locked behind a set of Builder Base progression milestones. Reaching Builder Hall 9, leveling your heroes to specific thresholds, completing Star Laboratory research, and hitting combined hero level targets are the gates. At full price, the hero upgrades and research timers are the bottleneck that keeps most players from finishing the grind. At 50% off both cost and time, those specific bottlenecks shrink dramatically.
GamingOnPhone's analysis puts it directly: this is the easiest the B.O.B. grind has ever been. The combined hero level requirement — where Battle Machine and Builder Base Royal Champion's levels together need to hit a target — becomes achievable in one event window rather than spanning multiple months of passive upgrades. If you're already close to Builder Hall 9 or have been casually progressing Builder Base for a year or two, this is the moment to fully commit and close out the unlock.
Requirement Category | What's Needed | How Bonanza Helps |
Builder Hall Level | Builder Hall 9 required to unlock B.O.B. | Building and defense upgrades are 50% faster — push BH9 during the event window if close |
Battle Machine Level | Battle Machine must reach a minimum level threshold | Hero upgrade costs and timers are both halved — the most expensive B.O.B. requirement becomes significantly faster |
Star Laboratory | Specific troop research levels required | 50% off research timers means multi-day research completes in half the time. Stack Clock Tower Potions from event tasks for additional acceleration |
Combined Hero Level (45) | Battle Machine + BB Royal Champion combined level targets | Both heroes benefit from the 50% discount simultaneously. Farming resources is faster via 4x Star Bonus. This is the key gate B.O.B. unlock depends on |
Resource Farming | Builder Gold and Builder Elixir needed for upgrades | 4x Star Bonus produces 4x normal resource yield from battles. Quick two-star attack strategies are the most efficient farming approach during the event |
Quick Two-Star Strategy for 4x Star Bonus Farming
T
he 4x Star Bonus is the resource engine that funds the upgrade queue. A quick two-star attack in Builder Base gives you the full Star Bonus without needing to three-star, which means faster attack cycles and higher resource throughput per hour than grinding for perfect attacks. The strategy: rush the Builder Hall and one or two nearby high-value buildings for two stars, collect the bonus, queue next attack. Repeat.
With 4x multiplier active, you're generating Builder Gold and Builder Elixir at a rate that makes keeping builders idle between upgrades the only real waste during this event. Farm aggressively from May 17 and keep that queue full.
Upgrade Priority Sequence — Do This in Order
Planning your sequence before May 17 is what separates players who max out the event's value from players who waste the first three days deciding what to upgrade next:
Order | Upgrade Type | Why This Sequence |
1st | Shorter upgrades first | Builders free up faster with 50% timer reduction. Planning next upgrades in advance means no idle builder time. Queue shorter upgrades first to keep builders constantly cycling |
2nd | Heroes (Battle Machine + BB Royal Champion) | Most expensive and time-consuming upgrades at full price. The 50% discount makes the biggest relative difference here. Prioritize these as soon as builders are free |
3rd | Star Laboratory research | Long research timers become manageable. Stack Clock Tower Potions from event tasks on top of the 50% timer reduction for additional speed. Don't leave the Lab idle |
4th | High-level buildings and defenses | These have the longest base timers at full price — the 50% reduction saves the most total hours on highest-level upgrades. Push to maximum level for your BH before moving to walls |
5th | Walls | Still discounted but lower priority than heroes, research, and buildings. Upgrade walls in remaining builder downtime after higher-priority upgrades are running |
Last | Longest single upgrade | Save your biggest remaining upgrade for the very end of the event window. Starting a long upgrade last means the 50% timer reduction is still active for its full duration rather than finishing before the event ends |
Key Factors That Maximize the Event's Value
•Don't start long upgrades the day before May 17 — Any upgrade running when the event starts at full cost is a wasted opportunity. If you have something close to completing that will finish before May 17, queue it normally. If it would still be running on May 17, wait and start it during the event at half price.
•Stack Clock Tower Potions on Research — Clock Tower Potions speed up Star Laboratory research. The event tasks reward them as rotating prizes every five days. Save them and drop them on your longest active research during the event window rather than using them on short research that would finish anyway
•Gold Pass 20% discount stacks on top of the 50% event discount — Gold Pass holders unlock additional builder and research discounts on the pass progression track. Timing your largest resource dumps for when both the Gold Pass discount and the Bonanza 50% are simultaneously active gives the highest combined value. Check your pass progression and plan the timing accordingly
•Rune of Builder Elixir from event tasks is immediately useful — Builder Elixir is the bottleneck resource for hero upgrades in Builder Base. A full Rune drops your entire Elixir need for the next upgrade. Complete the rotating tasks on Day 1, Day 5, and Day 10 of the event to claim all three potential reward cycles before May 31
•Builder Star Jars reduce the Stars needed for B.O.B. unlock — If you're chasing B.O.B., Builder Star Jars from event tasks directly reduce the grind. Each jar counts as a set of stars earned without requiring a battle, which is pure progress toward the unlock threshold
•Keep the Lab running — The Star Laboratory is easy to forget during an upgrade frenzy focused on buildings and heroes. The 50% research timer reduction makes multi-day research completable in single days during this event. Don't leave it idle while focusing on builders
How Builder Base Bonanza Fits Into May 2026
Builder Base Bonanza doesn't run in isolation — it overlaps with two other significant events in the second half of May. Clan Games (May 22–28) adds another resource and reward window mid-event. Extra Clan Games points are earnable through Builder Base activity during the overlap, which means your Builder Base grinding during Bonanza also contributes to Clan Games reward tracks simultaneously.
The Unlimited Dragon Duke Event (May 27–31) runs in the final days of Builder Base Bonanza. During that window, Dragon Duke and his equipment are available at full power even while they're being upgraded in your Home Village. The timing means the last five days of Bonanza coincide with a free Dragon Duke usage window — you're pushing Builder Base upgrades and getting full Dragon Duke access in Home Village at the same time. Efficient scheduling of whatever you want to do with Dragon Duke in that window should account for the Bonanza still being active.
Should You Gem Any Builder Base Upgrades During This Event?
Gemming upgrades is almost never worth it at full price. At 50% cost and 50% time, the math changes slightly but the conclusion doesn't fundamentally shift. The event already cuts your upgrade time in half — gemming to instant-complete a discounted upgrade costs more Gems for less total time saved than just letting the timer run at 50% speed.
The exception: if a specific upgrade would miss the May 31 deadline by hours and it's a high-priority upgrade you specifically need for B.O.B. or a key building threshold, a small gem rush on the final hours is defensible. Outside that specific scenario, let the timers run and keep the Gem spend for Gem-denominated items that don't have a time reduction analog — like Magic Items from the shop that don't scale with the Bonanza discount.
Final Thoughts
Builder Base Bonanza is the right event at the right time. Nine years in, Builder Base progression has always been the part of Clash of Clans that most players treat as an afterthought — too slow, too expensive, not worth the focused attention that Home Village gets. A 50% discount on everything simultaneously, combined with a 4x farming multiplier, is the event that makes ignoring Builder Base the wrong call for 14 days.
Have a queue planned before May 17. Heroes first, research second, buildings third, walls last. Farm aggressively during the 4x Star Bonus window. Complete the rotating tasks for Clock Tower Potions and Rune of Builder Elixir. And if you're close to B.O.B., this is your best shot at finishing it without months of additional grinding.
For Gems to keep Builders active through the full event window, the Clash of Clans top up page on LootBar has the rates I use. Don't let a builder sit idle on May 17. Chief.
