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: