opus 5.5 vs fable 5.1 vs gpt-6 astra – three post-apocalyptic films, one html file each

the setup: the same ~100k-token prompt for every model – a three.js skill pack, the brief and a mandatory delivery checklist. gpt-6 astra got one prompt and one reply on @OpenRouter, no agent loop. opus 5.5 and fable 5.1 ran as agents in claude code: write the file, open it in a browser, look at the frames, fix, repeat. opus tokens come from the session log and are priced at openrouter rates ($4 / $20 per million, cache reads $0.20). fable cost and tokens are estimates from file size, its wall clock is measured

every film is one html file, three.js 0.170 from a cdn, every texture generated in code. four shots on an auto-playing timeline, ~90 seconds, letterbox and fades, keys 1-4 jump between shots

tasks:
1. amusement park – a fogbound park at sunset: through the gate, a dolly around the carousel, a coaster pov over the first drop, a crane up the ferris wheel
2. ghost town – a mojave town at sunset: highway drone shot, main street dolly, a diner interior lit like a film set, a crane reveal over the whole grid
3. nuclear plant – a night sky as the hero: 30,000+ stars and a structured milky way over two 150 m cooling towers, the workers' town, the control room

models:
@AnthropicAI claude opus 5.5, claude fable 5.1, @OpenAI gpt-6 astra

all 36 shots render. opus and fable land all 12 on brief, astra lands 11 – its plant has almost no stars, and the sky was the whole point of that task

total cost, three films
#1 gpt-6 astra – $8.43
#2 claude fable 5.1 – ~$9.20
#3 claude opus 5.5 – $19.38

cost per film, opus vs astra
amusement park – $4.85 vs $2.54
ghost town – $9.94 vs $3.08
nuclear plant – $4.59 vs $2.81

wall clock, three films
#1 gpt-6 astra – 27m 16s
#2 claude fable 5.1 – 40m 3s
#3 claude opus 5.5 – 69m 18s

output tokens
#1 gpt-6 astra – 93,905
#2 claude fable 5.1 – ~98k
#3 claude opus 5.5 – 373,076

lines of code shipped
#1 gpt-6 astra – 4,714
#2 claude opus 5.5 – 2,580
#3 claude fable 5.1 – 1,691

observations:

- opus 5.5 found its own bugs by looking at its own frames: a nan in the light shafts that drew black dashed lines in the diner, "patch" used as a variable name (a reserved word in glsl), a camera that ended the control room shot staring into the console, trees that hid the blinking stack light at the end of the avenue
- the loop gets cheaper as it goes. opus built the ghost town first – 46 model calls and $9.94 – then the amusement park in 16 calls for $4.85 and the nuclear plant in 17 calls for $4.59, reusing its own kit from the first film
- $8.8 of the opus $19.38 is cache reads – every agent step re-reads a 200k-450k context
- gpt-6 astra is the fastest and the cheapest, 7m 18s to 10m 32s per film in one reply with no browser. its amusement park and ghost town run all four shots
- only opus put shafts of sun through dusty blinds in the diner and reflected its 38,000 stars in the cooling channel. fable matched it on the sky – 42,000 stars and a milky way with dust lanes

watch the full test via link: