Claude Opus 5.5 (effort default (no --effort flag) · thinking on) on Build a step-by-step interactive explainer web app that teaches a beginner how to choose an LED's series resistor

AClaude Opus 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-22 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.20
Wall time: 39s
Human step-ins: 0
Outcome: Pass

Compare with other models on this task →

Exact prompt

# Build a step-by-step explainer web app: choosing a series resistor for an LED Make a small interactive web app that teaches a beginner one hardware topic, one step at a time: how to pick the series resistor for an LED. `spec.json` gives the page title, the steps (each with a title and a fact sentence), and the standard resistor series to use (`series_base`, one decade of values, repeated across `decades`). Look, layout and wording beyond the spec are up to you; **looks are not scored**. The page is scored in a headless browser (800x600 window, network blocked) by objective checks only. Write one file, `out/explainer.html`, that works opened straight from disk. ## Steps - Show one step at a time. On load, step 1 is shown. Put the current step's title in `#step-title`, its text in `#step-body` and a counter in `#step-count`. - Buttons `#prev` and `#next` move one step back or forward. - Every step title must appear in `#step-title` in the order given in spec.json, and `#step-count` reads "Step <i> of <N>". - `#prev` is disabled (the `disabled` property) on step 1 and `#next` is disabled on the last step; neither moves past the ends. - `#step-body` for each step contains that step's fact sentence from spec.json exactly as written (extra text around it is fine). ## Calculator Inputs `#in-supply` (supply volts), `#in-vf` (LED forward volts), `#in-ma` (LED current in mA) and `#in-count` (LEDs in series, a whole number); outputs `#out-ohms`, `#out-standard`, `#out-mw` and `#out-error`. The calculator is visible on every step and recalculates on each `input` or `change` event (a `#calc` button is optional; it is clicked too if present). - For supply V, forward voltage F, current I mA and count n: R = (V - n x F) / (I / 1000). `#out-ohms` shows R rounded half-up to a whole ohm. - `#out-standard` shows the smallest standard series value that is at or above the exact R, never a smaller one. - `#out-mw` shows the resistor's power, (V - n x F) x I, in mW rounded half-up to a whole number. - Show numbers as plain digits (for example `1200`, not `1.2k`); a unit after the number is fine. - If any input is missing or not positive, or V is not greater than n x F, `#out-error` shows a non-empty message and `#out-ohms`, `#out-standard` and `#out-mw` are empty. Otherwise `#out-error` is empty. ## Checks (partial credit = share passed) 1. `self_contained`: `out/explainer.html` exists, is at most 150,000 bytes, references no http(s) or protocol-relative URL, and requests nothing from the network when opened. 2. `required_elements`: every element id named above is present, and the `<title>` contains spec.json's `title`. 3. `steps_in_order`: Every step title must appear in `#step-title` in the order given in spec.json, and `#step-count` reads "Step <i> of <N>". 4. `navigation_limits`: `#prev` is disabled (the `disabled` property) on step 1 and `#next` is disabled on the last step; neither moves past the ends. 5. `step_facts`: `#step-body` for each step contains that step's fact sentence from spec.json exactly as written (extra text around it is fine). 6. `calculator_values`: on hidden test inputs, `#out-ohms`, `#out-standard` and `#out-mw` all match the rules above. 7. `invalid_input`: If any input is missing or not positive, or V is not greater than n x F, `#out-error` shows a non-empty message and `#out-ohms`, `#out-standard` and `#out-mw` are empty. No build step and no other files are scored. ## 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.

Build a one-file web app that walks a beginner through choosing an LED's series resistor, one step at a time, with a live calculator. A headless browser clicks through the steps and feeds hidden inputs to the calculator, checking step order, the button limits at both ends, the given facts, the calculated values (including rounding up to a standard resistor value) and the error state. 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 required_elements steps_in_order navigation_limits step_facts calculator_values invalid_input

Setup notes: Batch 26 case b01-led-resistor-explainer (offline, synthetic inputs, seed 3119113257). 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 0.28 (8 cores). Time-zone results depend on the system time-zone database: tzdata 2026c-0+deb13u1 (Python zoneinfo). Claude Code's own reported cost for claude-opus-5.5: $0.195093. Score: 7/7. 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.

Metrics

Estimated cost: $0.20
Wall time: 39s
Human step-ins: 0
Turns: 5

Model usage
Model	Input tok	Output tok	Cost
AClaude Opus 5.5anthropic/claude-opus-5.5effort default (no --effort flag) · thinking on	107,293	4,187	$0.20

Reproduce this run

Use the use case prompt on the use case page.
Same setup: Claude Opus 5.5 (anthropic/claude-opus-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 required_elements steps_in_order navigation_limits step_facts calculator_values invalid_input
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.

Was this useful?

⇄ Rerun on another model

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": 37578,
  "stop_reason": "end_turn",
  "session_id": "[REDACTED]",
  "total_cost_usd": 0.1950926,
  "usage": {
   "input_tokens": 10,
   "cache_creation_input_tokens": 11520,
   "cache_read_input_tokens": 95763,
   "output_tokens": 4187,
   "output_tokens_details": {
    "thinking_tokens": 633
   },
   "server_tool_use": {
    "web_search_requests": 0,
    "web_fetch_requests": 0
   },
   "service_tier": "standard",
   "cache_creation": {
    "ephemeral_1h_input_tokens": 11520,
    "ephemeral_5m_input_tokens": 0
   },
   "inference_geo": "global",
   "iterations": [
    {
     "input_tokens": 2,
     "output_tokens": 719,
     "cache_read_input_tokens": 22620,
     "cache_creation_input_tokens": 1046,
     "cache_creation": {
      "ephemeral_5m_input_tokens": 0,
      "ephemeral_1h_input_tokens": 1046
     },
     "type": "message"
    }
   ],
   "speed": "standard",
   "fallback_credit": null
  },
  "modelUsage": {
   "claude-opus-5-5": {
    "inputTokens": 10,
    "outputTokens": 4187,
    "cacheReadInputTokens": 95763,
    "cacheCreationInputTokens": 11520,
    "webSearchRequests": 0,
    "costUSD": 0.1950926,
    "contextWindow": 1000000,
    "maxOutputTokens": 128000,
    "thinkingTokens": 633,
    "canonicalModel": "claude-opus-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": 5,
  "subtype": "success",
  "api_error_status": null,
  "result": "I built `out/explainer.html` and checked it in headless Chrome. Everything I tested came out right, but I tested with a copy of the page plus my own test script, not with the hidden scoring inputs.\n\n- **Steps:** Step 1 shows on load and the counter reads \"Step 1 of 6\". On the first step `#prev` is disabled; after clicking `#next` eight times the page stops at \"Step 6 of 6\" with `#next` disabled. Each step's title and fact sentence are written in exactly as they appear in `spec.json`.\n- **Calculator:** It recalculates on every `input` and `change` event, and the `#calc` button does the same. Some results from the test run:\n\n| Supply V | Forward V | mA | LEDs | Ohms | Standard | mW |\n|---|---|---|---|---|---|---|\n| 5 | 3.3 | 27 | 1 | 63 | 68 | 46 |\n| 12 | 2 | 20 | 3 | 300 | 300 | 120 |\n| 9 | 2 | 10 | 2 | 500 | 510 | 50 |\n| 5 | 1.8 | 16 | 1 | 200 | 200 | 51 |\n\n  An exact match (like 300) is returned as is, never rounded down to a smaller value.\n- **Invalid input:** A blank or negative input, or a supply voltage not above the LEDs' total drop (for example 5 V for two 2.5 V LEDs), shows an error message and clears all three outputs.\n- **Self-contained:** The file is about 5 KB, has no `http` references, and doesn't load anything from the network.\n\n**Choices the spec doesn't cover:**\n- **Non-whole LED count:** a count like 1.5 is treated as an error.\n- **Above the series:** if the resistance is above the largest value in the series (910,000 \u03a9), the standard-value box is left empty rather than showing a smaller part.\n- **Starting values:** the calculator opens filled in with the worked example from step 5 (5 V, 3.3 V, 27 mA, one LED).",
  "ttft_ms": 1814,
  "type": "result",
  "duration_ms": 38638,
  "uuid": "[REDACTED]",
  "ttft_stream_ms": 942,
  "time_to_request_ms": 252,
  "first_content_frame_ms": 942,
  "queued_turn_count": 0,
  "result_index": 0
 }
]