Claude Sonnet 5.5 (effort default (no --effort flag) · thinking off) on Bouncing logo screensaver in one self-contained HTML file

AClaude Sonnet 5.5default · thinking off · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-20 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.04
Wall time: 10s
Human step-ins: 0
Outcome: Pass

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Exact prompt

# Bouncing logo screensaver in one self-contained HTML file Make a classic bouncing-logo screensaver: a logo of your own design that bounces off the edges of the window. Style, colours and technique (CSS, SVG, canvas) are up to you. **Looks are not scored**; only the objective checks below are. Write one file, `logo.html`, in the working directory. ## Checks (all must pass; partial credit = fraction passed) 1. `file_exists_under_size_limit`: `logo.html` exists and is at most 50,000 bytes (50 KB). 2. `no_external_requests`: fully self-contained. No `http://`, `https://` or `//` URLs in `src`, `href`, `srcset`, `poster`, `action`, `data` or `url()`, no asset URLs anywhere, no `@import`, `fetch(`, `XMLHttpRequest`, `WebSocket`, `EventSource`, `sendBeacon`, JS `import`, `<script src>` or `<link href>` (inline everything; `data:` URIs are fine). When a browser is used, any non-file request the page attempts also fails this check. 3. `animation_present`: CSS `@keyframes` plus an `animation`/`animation-name` property, or `requestAnimationFrame(` / `setInterval(`. 4. `loops_forever`: an `infinite` CSS animation (`animation-iteration-count: infinite` or `infinite` in the `animation` shorthand), or rAF/`setInterval` with no `cancelAnimationFrame`/`clearInterval` anywhere; when a browser is used, the page must also still change between ~6 s and ~7 s after load. 5. `page_animates`: when a headless Chrome/Chromium is available, the page is opened once with the network blocked at 800x600, and screenshots at ~1.5 s and ~2.5 s after load must differ. Without a browser (or if it fails to start) this and the browser part of check 4 fall back to the static checks 3-4; the scorer reports `check_mode` (`headless-browser` or `static-fallback`). 6. `required_id_and_title`: an element with `id="logo"` and a `<title>` containing "Bouncing Logo" (case-insensitive). No other files, no build step, no network. Run time limit for scoring: 120 s.

Recreate the classic bouncing-logo screensaver as one self-contained HTML file with a tighter 50 KB size limit. The scorer checks only that it makes no network requests, animates continuously, visibly changes in headless Chrome, and carries the required id and title. Looks are not scored and are left to a public poll. 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: 1. file_exists_under_size_limit 2. no_external_requests 3. animation_present 4. loops_forever 5. page_animates 6. required_id_and_title

Setup notes: Use Case Scout batch 11 case l05-bouncing-logo (offline, open-ended creative brief). Prepared with batch11/prepare.sh; hidden checker kept outside the agent's work dir. Prompt = TASK.md verbatim. Scored with the case's scorer (`python score.py WORKDIR KEYDIR`, headless Chrome over a CDP pipe, network blocked). Tools: Read/Write/Edit/Glob/Grep/Bash, web disabled. Single run, no retries. Output rendered offline (google-chrome headless, network blocked): PNG 1280x800 at ~3 s after load; MP4 1280x720 H.264 ~6 s. Claude Code's own reported cost for claude-sonnet-5.5: $0.041135. 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: $0.04
Wall time: 10s
Human step-ins: 0
Turns: 2

Model usage
Model	Input tok	Output tok	Cost
AClaude Sonnet 5.5anthropic/claude-sonnet-5.5effort default (no --effort flag) · thinking off	38,123	1,014	$0.04

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 off) via Claude Code 2.1.299 (headless -p), cloud.
It counts as a success only if it meets every success criterion: 1. file_exists_under_size_limit 2. no_external_requests 3. animation_present 4. loops_forever 5. page_animates 6. required_id_and_title
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

[
 {
  "duration_api_ms": 9246,
  "stop_reason": "end_turn",
  "session_id": "[REDACTED]",
  "total_cost_usd": 0.0411351,
  "usage": {
   "input_tokens": 4,
   "cache_creation_input_tokens": 6968,
   "cache_read_input_tokens": 31151,
   "output_tokens": 1014,
   "output_tokens_details": {
    "thinking_tokens": 0
   },
   "server_tool_use": {
    "web_search_requests": 0,
    "web_fetch_requests": 0
   },
   "service_tier": "standard",
   "cache_creation": {
    "ephemeral_1h_input_tokens": 6968,
    "ephemeral_5m_input_tokens": 0
   },
   "inference_geo": "global",
   "iterations": [
    {
     "input_tokens": 2,
     "output_tokens": 204,
     "cache_read_input_tokens": 18612,
     "cache_creation_input_tokens": 895,
     "cache_creation": {
      "ephemeral_5m_input_tokens": 0,
      "ephemeral_1h_input_tokens": 895
     },
     "type": "message"
    }
   ],
   "speed": "standard",
   "fallback_credit": null
  },
  "modelUsage": {
   "claude-sonnet-5-5": {
    "inputTokens": 4,
    "outputTokens": 1014,
    "cacheReadInputTokens": 31151,
    "cacheCreationInputTokens": 6968,
    "webSearchRequests": 0,
    "costUSD": 0.0411351,
    "contextWindow": 1000000,
    "maxOutputTokens": 128000,
    "thinkingTokens": 0,
    "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": {
   "spawned": 0,
   "requested": {
    "background": 0,
    "foreground": 0,
    "unset": 0
   },
   "started_in_background": 0,
   "max_depth": 0,
   "spawned_by_subagents": 0,
   "completed": 0,
   "failed": 0,
   "killed": {
    "parent": 0,
    "user": 0,
    "system": 0
   },
   "refused": {
    "depth_limit": 0,
    "concurrency_limit": 0,
    "budget": 0
   },
   "by_type": {}
  },
  "safety_stops": 0,
  "is_error": false,
  "num_turns": 2,
  "subtype": "success",
  "api_error_status": null,
  "result": "I wrote `logo.html` in the working directory, but I haven't opened it in a browser or run any of the checks.\n\nIt's a red rounded rectangle with a white circle and the word \"BOUNCE\", drawn as inline SVG in a `div` with `id=\"logo\"`. A `requestAnimationFrame` loop moves it across the window and bounces it off all four edges. The loop never stops, and the logo changes colour on each bounce. The page has no external resources, and the title is \"Bouncing Logo\".\n\nThe file is well under 50 KB. By reading the code, it should meet the static checks (animation present, loops forever, required id and title).",
  "ttft_ms": 5518,
  "type": "result",
  "duration_ms": 9540,
  "uuid": "[REDACTED]",
  "ttft_stream_ms": 1163,
  "time_to_request_ms": 265,
  "first_content_frame_ms": 1163,
  "queued_turn_count": 0,
  "result_index": 0
 }
]