Claude Sonnet 5.5 (effort default (no --effort flag) · thinking on) on Animate a metronome that ticks a repeating two-tempo pattern 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: 13s
Human step-ins: 0
Outcome: Pass

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Exact prompt

# Animate a metronome that ticks a repeating two-tempo pattern in one self-contained HTML file Make a small animated scene: a metronome. 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): `{beats: <integer number of beats completed>, angle_deg: <arm angle, positive to the right>}`. Extra fields are fine. It must describe what is actually drawn. - Time 0 is `performance.now()` 0 (seconds = `performance.now()` / 1000). The tempo follows `pattern` in order: `beats` beats at the first `bpm`, then `beats` beats at the next, then the pattern repeats. A beat lasts 60 / bpm seconds, and the count starts at 0 before the first beat completes. The arm is at +`amplitude_deg` at time 0 and reaches the opposite side at each completed beat. `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. `beat_count`: at every sample `sceneState().beats` equals the number of beats completed since time 0 under spec.json `pattern` (a 30 ms margin either side of a beat is allowed). 5. `arm_follows_beats`: at every sample `angle_deg` is within 4° of `amplitude_deg` × cos(π × b), where b is the fractional number of beats since time 0. 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 metronome 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 (beat count; arm follows beats) 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: self_contained has_canvas_or_svg frames_change beat_count arm_follows_beats no_console_errors

Setup notes: Batch 30 case o08-metronome-tempo-pattern (offline, synthetic inputs, seed 399223806). 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 0.14 (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: $0.05085. 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: 13s
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	58,358	1,486	$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: self_contained has_canvas_or_svg frames_change beat_count arm_follows_beats no_console_errors
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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  "modelUsage": {
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    "contextWindow": 1000000,
    "maxOutputTokens": 128000,
    "thinkingTokens": 198,
    "canonicalModel": "claude-sonnet-5-5",
    "provider": "firstParty",
    "costBasis": "list"
   }
  },
  "permission_denials": [],
  "terminal_reason": "completed",
  "fast_mode_state": "off",
  "fast_mode_disabled_reason": "sdk_opt_in_required",
  "subagent_stats": {
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   "requested": {
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  "subtype": "success",
  "api_error_status": null,
  "result": "I wrote `out/scene.html`, but I haven't opened it in a browser or run any of the six checks against it.\n\n- **Stage:** it draws a 720x480 canvas with a metronome body, a swinging arm, a red weight on the arm and a beat counter. The page title is \"Metronome 360\".\n- **Timing:** `window.sceneState()` works out the fractional beat count from `performance.now()` at the moment it's called. It follows the pattern in order: 2 beats at 150 bpm, then 4 at 180, then repeats. It returns `beats` as the floor of that count and `angle_deg` as 30 \u00d7 cos(\u03c0 \u00d7 beats so far). The arm starts at +30\u00b0 at time 0 and reaches the opposite side at each completed beat.\n- **Animation:** the draw loop runs on `requestAnimationFrame` from load and draws from the same state function, so the drawn arm matches what `sceneState()` reports.\n- **Self-contained:** everything is inline, with no external URLs or scripts, and the file is small.\n\nI haven't confirmed that the page logs no errors.",
  "ttft_ms": 1578,
  "type": "result",
  "duration_ms": 12002,
  "uuid": "[REDACTED]",
  "ttft_stream_ms": 1005,
  "time_to_request_ms": 242,
  "first_content_frame_ms": 1006,
  "queued_turn_count": 0,
  "result_index": 0
 }
]