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senko | on: Claude Opus 4.8
My fav coding benchmark for frontier models is to build a simple RTS game in one file (js/html/css). Claude Code with Opus 4.8 in ultracode mode nailed it, the best result so far:

https://bsky.app/profile/senko.net/post/3mmwnrkwboc2v

The prompt was: Create a simple but functional real time strategy (RTS) game similar to old WarCraft, StarCraft or Command & Conquer games. The player should be able to build buildings, create units, gather resources and should uncover the whole map. No AI or multiplayer needed. Use simple but nice-looking graphics. No sound. Implement everything in HTML/CSS/JS, everything in a single file (you can use 3rd-party js or css libraries/frameworks via CDN).

egeozcan | parent | next
I've been tasking LLMs to write a traditional AI for a full vibe-coded RTS. I remove the human players and let them battle. I don't know why but I enjoy watching AI players battle so much :)

In the repo, I even have a tournament script that calculates ELOs. So far, codex was unmatched. I'll try with Opus 4.8 too.

https://egeozcan.github.io/unnamed_rts/game/

https://github.com/egeozcan/unnamed_rts/blob/main/src/script...

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calebgcc | parent | next
I wonder if your previous prompts were part of the new RL fine tuning, and that’s why is now better at this specific question
jclay | parent | next
It almost appears as if the code was minified. The variable names are short and formatting looks like it's written to minimize whitespace. Did it write it in this compact format all on it's own?
dilap | root | parent | next
Doesn't look minified, just very dense, almost like progcomp code. First time I've seen an LLM spit out that style of code, I'm impressed!
senko | root | parent | next
Yeah looks extremely compact. I didn't instruct it or told it to use as few lines of code or characters or nothing of the sort.

Not sure why it did that. Its own rationale (which is highly suspect, but the only lead I have) is that it defaults to dense style if it has to write a file in a single go. May be a kernel of truth somewhere in there.

bombcar | root | parent | next
And much code on the web “in production” is minimized.
AdamN | root | parent
minified is fewer tokens than the human-readable version that we would write. It only really makes sense to write in minified js - it's also where alot of code in the wild is since every production site minifies their js which is then consumed by training.
syspec | root | parent | next
I just had Opis 4.8 code up something and actually that's exactly how it coded it!

It looked gross and minimized, the result was awesome but the code looked pretty awful visually

andai | root | parent | next
A friend sent me something he vibe coded which included a massive webassembly blob in the HTML file. My friend is not a programmer so he was not able to explain to me how it did that.
rphv | root | parent
"Readability by humans" may no longer be as important as it once was.
lionkor | root | parent | next
Maybe it would benefit Anthropic if AI generated code worked, but wasn't readable by humans. That's a nice moat.
selcuka | root | parent | next
Good variable names are still useful for LLMs to understand context when refactoring.
orphea | root | parent
Only if LLMs will start to output object code, skipping text representation.
apitman | parent | next
I like that benchmark. You should throw the results up on GitHub pages so people can try out the games.
brandly | root | parent
Yeah! Host on GitHub pages, so it's easy to click a link and play!
senko | root | parent
Great idea!

I have a static server of my own, so here's my list (of all the tests I published so far): https://senko.net/vibecode-bench/

apitman | root | parent | next
Forget GH pages. Indiehosted ftw.
paulirish | root | parent
Would love to see the prompts, too!
jmtame | root | parent
Same!
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skolos | parent | next
How many times did you try? Same model running multiple times can produce both very good and very bad results. In my benchmark even 10 runs often not enough to tell for sure if one model is better than another.
senko | root | parent
Usually just once (and I did just one test for this particular one), but I've found the overall quality to be relatively consistent.

There's too many confounding variables here, randomness just one of them. So I don't think of it as a definitive test (and reliable ordering), just another data point (along with actual benchmarks, pelicans, etc) to get a sense of the capabilities.

For example, I managed to get something out of DeepSeek 4 Flash quantized to 2-bit with Antirez' DwarfStar, used via Pi. Almost kinda worked! :) Which makes me optimistic for using local models for serious development soon - I'd say within a year.

RobinL | parent | next
Nice, I recently found something like this was possible too. Gpt-5.5 one shotted the basic game, but then I added some ai generated graphics/sounds/music and asked it to write then up.

It's a vocab building game, playable here (desktop only): https://rupertlinacre.com/vocab_annihilation/

It kind of blows my mind I can go from: 'I want a fun way to help him learn vocabulary, and I loved total annihilation as a kid' to 'heres a game that's he finds genuinely fun that helps him learn something ' in a few prompts.

elAhmo | parent | next
What is ultracode mode?
senko | root | parent | next
It's a combination of reasoning effort (max) + enabling workflow that orchestrates multiple sub-agents.

After some interrogation, here's how it organized the work:

1. Design workflow (rts-game-design, 11 agents, ~13 min) ran first, produced SPEC.md + DESIGN.md:

1.1. Proposals (3 parallel agents): each designed a complete RTS from a different philosophy

1.2 Judge (1 agent): evaluated all three and synthesized one unified design, committing to specific numbers (costs, HP, map size, etc.).

1.3 Deep-dives (6 parallel agents): each wrote an implementation-ready spec for one subsystem, all consistent with the chosen design

1.4 Synthesis (1 agent): merged the design + all six subsystem specs into one conflict-free master spec

2. Code-review workflow (rts-code-review, 25 agents, ~5 min), ran after the main agent had written and tested the code:

2.1 Review (6 agents, read-only Explore type): each scrutinized one dimension and returned structured findings.

2.2. Verify (19 agents): every finding got its own skeptic agent told to try to refute it, Result: 19 flagged → 16 confirmed, 3 rejected as non-bugs.

What the main agent did in the main loop:

- Wrote all ~2,400 lines of index.html by hand from the spec.

- All browser testing/debugging via headless Chrome (I told it to use rodney by @simonw, love the tool :)

- Applied all 16 fixes from the review and re-verified them in the browser.

33MHz-i486 | root | parent | next
seems like a rube-goldberg esque way to consume 10x tokens. is this really where the industry is heading?
e12e | root | parent | next
I like to think of it like the difference between dropping a ball on a roulette wheel (get one random number/sequence of repeated) - vs dropping a ball on a carved topographic map, where valleys guide the ball to a particular outcome.

If you can stand a little AI expansion - here are a few points Gemini came up with - I think the idea has some merit:

https://g.co/gemini/share/b5b97867eeb1

(Maybe the better analogy is roulette vs pinball machine)

derac | root | parent
Why is it Rube Goldbergesque? The process doesn't seem arbitrary.
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artur_makly | root | parent | next
Just to confirm - you did not generate this plan/orchestration/harness - it did all that on its own?
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chrisweekly | root | parent | next
Did you start with a clean slate or do you have global ~/.claude/CLAUDE.md and/or specific skills, plugins, etc?
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jmtame | root | parent
Thanks for sharing this. Going to try it out on a game inspired by Rust. It's helpful re: the point on rodney - I've had a hard time getting the testing to work well in the browser.
tcoff91 | root | parent | next
it's a brand new mode
colechristensen | root | parent
Biases the model to solve problems with teams of agents
H3X_K1TT3N | parent | next
Thanks for also sharing the prompt. I've been testing claude by asking it to make similar things, so it's useful to see what other people are doing.

I do find it interesting that the visual style is pretty similar to things it's produced for me.

dash2 | root | parent
If you look on the page of games, the style of chatgpt 5.5 is almost identical to the Claude style.
digdugdirk | parent | next
Do you have a collection of these benchmark apps saved anywhere? I'd be particularly interested in seeing the relative cost differences between different models in a use case like this.
senko | root | parent
I'm saving them all as gists here: https://gist.github.com/senko

But I just vibe-coded a handy list of all the tests I did (unfortunately without the commentary I usually leave in social media posts -- I should add those at some point): https://senko.net/vibecode-bench/

ammar_x | parent | next
Is there some sort of a leaderboard for this test? Like if you'd give each of Opus 4.8 and GPT 5.5 a score out of 100, what would the scores be?
senko | root | parent
There isn't, as I wasn't going for strictness, more like a playful challenge in the vein of Simon's SVG pelican.

Between the two, Opus 4.8 seems more capable. But, I suspect the harness plays a large role here. It's possible the result would be as good if Codex ran 10+ agents and spent an hour on it.

OpenAI and Anthropic usually fast-follow each other, so I wouldn't be surprised if Codex got the same capability in a couple of days (and even an update to the model), then it'll be a better test.

Sooo, let's say, winging it, vibes-based: 85% for Opus 4.8, 75% for GPT 5.5. Compare with GPT 5.3 (let's say 25%) here: https://senko.net/vibecode-bench/2026/rts-codex-5.3.html

jryan49 | parent | next
Kinda buggy, but impressively nonetheless. How long did it take?
senko | root | parent
It took 50 minutes, would be ~$20 in API costs (I'm on a Pro sub).
senko | root | parent
(Correction: I'm on a Max ($100/mo) sub. Realized the mistake too late, so can't edit my comment.)
jmtame | parent | next
Wow, that's impressive. Had fun playing it for 10 minutes locally. Found myself wanting to discover an enemy base :)
zuzululu | parent | next
some reason that website is showing up as high risk and i cannot view it , I had to open it from my mobile phone.

it looks quite impressive, I don't use claude currently but hearing good things about it...from codex users ironically

senko | root | parent
Is that for bsky.app (BlueSky platform) or my personal site (senko.net) where I put up the list of tests? What browser/device was that?
fireant | parent | next
Wow that looks really impressive. Both the UI and the content looks good, the game is a bit buggy but still nice!
Madmallard | parent | next
Okay now have it implement an authoritative server with reliable netcode and reconnection/disconnection logic, lobbies, and finding games, in-game chat, synchronized state around starting and ending games, resignations and such
shlewis | parent | next
How much did it cost?
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l3x4ur1n | parent | next
Played it to the end. Pretty neat!