Claude Opus 5.5 in Claude Code 2.1.280
skills off
We ended the run ourselves before any output. Not a model failure.
Wall time 42m 59sCost $5.81 reported
Generation timelapse
Generation timelapse (the agent's screen during the run, sped up). This is not the finished video. Download video (329 KB).
Review
No verdict yet.
The full review
Stopped by us. Stopped by us (box row cap reached (2866s); stopped by the box lane so the run ships as partial); not a model failure.
Attempt 1 of 2
Every try of this model in this harness on this prompt, oldest first. A later attempt is the cell's result: attempt 2.
- Attempt 1 Stopped by us this run42m 59s$5.812026-09-26
- Attempt 2 OK the cell's result2h 48m$25.182026-09-26
Scores
Not scored: only runs that finished on their own are scored.
Downloads
Files actually published for this run. Original output, site-made previews and post-run conversions are labelled separately.
The exact prompt
as run, 725 characters. Every result for this prompt
Build a conceptual X-16 engine in 3D with Three.js: four cylinder banks, one crankshaft and exposed mechanics inspired by experimental multi-bank engine architectures. Make it animate (pistons, rods and crank moving in sync) with orbit controls. Everything is built in code from Three.js geometry, shaders and materials; no external models or textures. Build it as a single self-contained index.html in the current directory. Three.js may load from a CDN or be vendored. You may serve it locally and open it in headless chromium (/usr/bin/chromium, software WebGL, no GPU) to screenshot and inspect your own output, and iterate on your own before finishing. Close any browser you open as soon as you've taken your screenshot.
How it was made
Step by step
The prompt, every agent turn and tool call (tool name and a one-line summary; inputs and outputs are not shown), then the final message. The full machine-format transcript is published as a scrubbed download.
Show all 19 steps
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Download the full transcript Claude Code session JSONL, 492 KB. Scrubbed: anything that looks like a key, token, e-mail address or phone number is replaced, and account details and the test machine's file paths are removed.
Cost breakdown
Headline cost $5.81, as reported by Claude Code (its own bill for the run). The list-price estimate from the token counts is $5.84.
| Tokens by type | Tokens | $ per 1M | Cost |
|---|---|---|---|
| Input (uncached) | 34 | $4.00 | $0.0001 |
| Cache write | 232,468 | $5.00 | $1.1623 |
| Cache read | 883,232 | $0.20 | $0.1766 |
| Output | 225,234 | $20.00 | $4.5047 |
| of which reasoning | 218,216 | billed as output |
- Total computed from tokens
- $5.8438
- Total reported by the harness
- $5.8084
- Difference
- computed $5.84 vs reported $5.81 (diff +0.04)
Claude Code 2.1.280 reported its own total; token counts x list prices shown beside it.
Prices: Project price table (vendor list prices), 2026-09-22.
Run notes
- frozen prompt (written): engine/prompts_written/x16_engine.txt: a new test's prompt written by us from the project lead's brief (zero results)
- plain wave-1-equivalent cc_config copy (settings.json + .claude.json; no ECC files)
- Mode: interactive TUI in tmux (160x48), inside bubblewrap sandbox
- Context setting: 1M ([1m] model name)
- Isolation audit: outside paths seen