Claude Sonnet 5.5 (effort default (no --effort flag) · thinking on) on Animate a mass on a damped spring released from rest in one self-contained HTML file

AClaude Sonnet 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-23 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.05
Wall time: 14s
Human step-ins: 0
Outcome: Pass

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Exact prompt

# Animate a mass on a damped spring released from rest in one self-contained HTML file Make a small animated scene: a damped mass-spring oscillator. Write one file, `out/scene.html`, that works opened straight from disk with no network access. `spec.json` gives the page title, the stage size and the scene parameters. **Looks are not scored**: the page is opened in a headless browser (800x600 window, UTC time zone, network blocked) and checked by objective tests only. ## Scene contract - Draw the scene on one `<canvas>` or `<svg>` stage of `width` x `height` CSS pixels (spec.json), visible on load, with `<title>` containing spec.json `title`. - Animate continuously from load (`requestAnimationFrame` or timers); no click is needed unless stated below. - Expose `window.sceneState()`, returning the scene's current state in stage pixel coordinates (origin top-left of the stage): `{x: <displacement of the mass from rest, px, positive = stretched>, v: <velocity, px/s>}`. Extra fields are fine. It must describe what is actually drawn. - Time 0 is `performance.now()` 0 (seconds = `performance.now()` / 1000). Treat px as the length unit for displacement (the dynamics only need the rate constants: damping rate = damping_ns_per_m / (2 × mass_kg), natural frequency = √(k_n_per_m / mass_kg)). The mass is released from rest, so its velocity at time 0 is 0. Draw the spring from a fixed anchor to the mass, `rest_length_px` long at rest. `sceneState()` must return the state at the moment it is called. - The page must log no errors and throw no exceptions. Keep the file at most 200,000 bytes; no external scripts, fonts, images or URLs (inline everything). ## Checks (partial credit = share passed) 1. `self_contained`: `out/scene.html` exists, is at most 200,000 bytes, references no http(s) or protocol-relative URL, and requests nothing from the network when opened. 2. `has_canvas_or_svg`: a visible `<canvas>` or `<svg>` of at least 300x200 CSS pixels is on the page. 3. `frames_change`: over 3 s, some later screenshot differs from the first in at least 0.1% of pixels, and at least 3 of 30 screenshots differ. 4. `damped_position`: at every sample, `x` is within 1.5 px of the exact displacement of a damped mass-spring released from rest at `x0_px` at time 0 (mass `mass_kg`, stiffness `k_n_per_m`, damping `damping_ns_per_m`). 5. `damped_velocity`: at every sample, `v` is within 3 px/s + 2% of `x0_px` × the damped angular frequency of the exact velocity. 6. `no_console_errors`: no uncaught exception, `console.error` or browser error is logged during the run. ## How this run works - Work on your own: nobody will answer questions in this task, and writing to `ask/` counts against the run. - Write only under `out/`. Create `out/` if it is missing. Inputs are synthetic; don't fetch anything from the network. - Scoring is partial credit: each listed check is pass/fail, and the score is the share passed. Numbers are compared to within 0.005 unless the task says otherwise.

Make a damped mass-spring oscillator animation as one self-contained HTML file. A headless browser checks objective facts only: the file is offline and small, a canvas or SVG stage is drawn, frames change, the scene follows a timed specification (damped position; damped velocity) and nothing errors. A poster PNG and a short MP4 are captured for the gallery. Looks are not scored. Original benchmark task written for usecaserank.com (not based on a specific public post). Headless, offline run on a reproducible fixture. Each run's notes say how its cost was measured (estimates are marked).

Success criteria: Passes the case's automated scorer (hidden tests / answer key, run after the agent finished).

Setup notes: Batch 31 case ta07-damped-spring-oscillator (offline, synthetic inputs, seed 612511471). Autonomous case: no stand-in user and no step-ins expected; any file the solver wrote to ask/ is counted as a measured intervention (0) and blocks a pass. Prompt = TASK.md verbatim. Hidden key kept outside the solver's work dir. Scored with the case's scorer (python3 score.py WORKDIR KEYDIR, absolute paths); pass = every check true and no ask/ files. Tools: Read/Write/Edit/Glob/Grep/Bash, web disabled. Single run, no retries. 1-min load average at scoring 0.58 (8 cores). Creative case: looks are not scored; objective checks run in headless google-chrome (800x600, UTC, network blocked, Date mocked). Gallery media (3 s capture: poster.png + clip.mp4) written by the scorer to a fresh MEDIA_DIR per run (media/<run>/), SHA-256 in evidence.media; a single failed scene check is rescored once (both recorded in rescore). Time-zone results depend on the system time-zone database: tzdata 2026c-0+deb13u1 (Python zoneinfo). Claude Code's own reported cost for claude-sonnet-5.5: $0.047596. Score: 6/6. Cost is an ESTIMATE: measured tokens x pricing.json list price (Claude Pro subscription, nothing billed); input_tokens include cache reads and writes. Single run.

Estimated cost List-price estimate; not actually billed.

Output

Metrics

Estimated cost: $0.05
Wall time: 14s
Human step-ins: 0
Turns: 3

Model usage
Model	Input tok	Output tok	Cost
AClaude Sonnet 5.5anthropic/claude-sonnet-5.5effort default (no --effort flag) · thinking on	58,220	1,245	$0.05

Reproduce this run

Use the use case prompt on the use case page.
Same setup: Claude Sonnet 5.5 (anthropic/claude-sonnet-5.5, effort default (no --effort flag) · thinking on) via Claude Code 2.1.299 (headless -p), cloud.
It counts as a success only if it meets every success criterion: Passes the case's automated scorer (hidden tests / answer key, run after the agent finished).
Log model, tokens, wall time, human step-ins and the evidence log, then submit it as a reproduction. A different model? Submit a head-to-head rerun.

How runs are scored: Methodology.

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Automated checks

Trust 80% comes from these checks (how Trust % works).

Run date is not in the future : passed
Model is in the dated pricing table : passed
Cost recomputed from tokens matches : passed
Cached tokens are consistent : passed
Output throughput is plausible : passed
Autonomy matches step-ins : passed
Step-ins do not exceed turns : passed
Retries agree with first-try result : passed
Evidence log SHA-256 matches : passed
Evidence log is substantial : passed

Evidence log

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    "canonicalModel": "claude-sonnet-5-5",
    "provider": "firstParty",
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  "permission_denials": [],
  "terminal_reason": "completed",
  "fast_mode_state": "off",
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  "subagent_stats": {
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  "result": "I wrote `out/scene.html`, but I haven't opened it in a browser or run any of the checks, so it's untested.\n\n- **Dynamics:** `window.sceneState()` computes `x` and `v` from the exact damped-spring solution for released-from-rest at `x0_px` = 130, using the current `performance.now()`.\n- **Constants:** it uses the spec values (mass 1.0, stiffness 40, damping 0.8, rest length 288), which I hard-coded rather than reading `spec.json`. That gives a damping rate of 0.4 and a damped frequency of about 6.31 rad/s.\n- **Drawing:** the animation loop calls the same function every frame, so what's drawn matches what `sceneState()` returns. It draws a 720x480 canvas with a wall anchor, a zigzag spring and a square mass. At rest the mass sits 288 px from the anchor.\n- **Self-contained:** everything is inline, with the title \"Damped Spring 276\" and no external URLs or resources. The file is a few hundred bytes, far under the 200,000-byte limit.",
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  "uuid": "[REDACTED]",
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  "time_to_request_ms": 249,
  "first_content_frame_ms": 1030,
  "queued_turn_count": 0,
  "result_index": 0
 }
]