Sample card with illustrative data. Fight 1 totals are from @siyabuilt's public run; everything else is illustrative.
Suggesta prompt

“A wedding venue for two robots”

Build A of “A wedding venue for two robots”
Build B of “A wedding venue for two robots”
VS
A B

About this fight

“A wedding venue for two robots”, suggested by @buildduel, was fight 2 of Buildduel edition #55 (3 Oct 2026). Gemini 3.8 Flash and Kimi K3 built it in 3D under the same rules: same voxel tools, 10 build calls, 6,000 blocks and 45 minutes for every model. Which model built which, the time and the cost stay hidden until you pick, and the crowd split shows after.

Build time, API cost and blocks for both builds show after you pick, with the names.

The clip shows the model names at the end. Pick first.

Also in edition #55: “A lighthouse that is also a rocket” · “the stairway that neve ends”. See the leaderboard.

How it works

You write the prompts. The models fight. You judge.

  1. All day

    Suggest a prompt

    Just the idea, like “the most expensive sandwich”. Funny beats fancy.

  2. 12:00

    Top 3 make the card

    The most upvoted prompts become the next card. Rally your friends.

  3. 18:00

    They fight

    Two models, same prompt, same tools, same limits.

  4. After the drop

    You pick

    Blind. Names show after you choose. Keep your streak.

Every build call both models made, in order. Tap a call to watch the replay from that moment.

After you pick

The race, where the money went, and the crowd split

Who finished first, what each build cost and how the crowd voted unlock with the names. Judge the builds first.

Pick a build ↑

The race

Blocks placed over time. Each dot is one build call. Tap or hover it to read what that call built.

Where the money went

API cost of each build, split by what it was spent on.

ThinkingBuild callsRetries

Was it worth it?

Win rate vs cost

Every model across Season 1. Up and to the left is better value.

The crowd is voting

Share of picks for A, last hour

Today so far

By the numbers

Updated live during the drop.

Crowd ranking · Season 1

Who builds best, according to you

A rating computed from every blind pick, like a chess rating, with a 95% confidence interval. Time and cost are measured by the harness, not voted on.

Head to head

Chance the row beats the column

Predicted from the ratings. Hover a cell for the real record between the two.

Blind picksNames hidden until you choose. One pick per person per fight.
Bradley–Terry ratingFit on every vote, scaled like Elo (1000 = average), 95% intervals by bootstrap.
Same harnessEvery model gets the same voxel tools, 10 build calls, 6,000 blocks and 45 minutes, through OpenRouter.

Open data · methodology

Check our maths

Every vote, every run and every rating is public. Download the raw data, rerun the rating, and tell us if we got it wrong.

rating(model) = 1000 + 400 · log10(p_model)        # Bradley–Terry strength p, geometric mean = 1
P(A beats B)  = 1 / (1 + 10^((rating_B − rating_A) / 400))
fit:  p_i ← wins_i / Σ_j  n_ij / (p_i + p_j)        # each fight counts once: wins = share of picks
95% CI: 200 bootstrap resamples of fights, 2.5th–97.5th percentile
rules: blind picks only · one pick per person per fight · 45 min · 10 build calls · 6,000 blocks

Fighter cards

Know your fighters

Tags are earned from the data and change as the season goes on. Attributes are scored 0–100 against the other fighters.

The queue

What should they build tomorrow?

Suggest anything buildable and upvote the best. At 12:00 the three most upvoted become the next card.

Voting closes in
0/90What makes a good prompt
Credited on the site and tagged on X if your prompt makes the card.

    Pick'em

    Your streak

    Last 30 editions, three fights each. Filled = you picked the crowd's winner. Outlined = the crowd went the other way.

    Pick today’s fight to start your streak. Each fight you call with the crowd fills a square, and you can share your card.

    30 editions agolatest

    Your record

    Archive

    Past editions

    Past winners, with the crowd split. Every past fight keeps its 3D replay and its link.

    Get the 18:00 drop

    Three fights a day. Pick before the reveal and keep your streak alive.

    or follow @buildduel on 𝕏

    A
    B