Claude Opus 5.5 (effort default (no --effort flag) · thinking on) on Decode a secondhand bookshop's pencilled cost and price codes and check each book's margin

AClaude Opus 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-26 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.12
Wall time: 18s
Human step-ins: 0
Outcome: Pass

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Exact prompt

# Decode a secondhand bookshop's pencilled cost and price codes and check each book's margin Inputs: `books.csv` (book_id, shelf_id, mark), `shelves.csv` (shelf_id, name) and `cipher.json` (code_word, repeat_letter). Each mark was pencilled inside a book's cover in the shop's private letter code and typed up by hand. The code word, books and shelves are synthetic; amounts are in dollars. These rules are the shop's; where `volunteer-notes.txt` disagrees, the rules win. Rules: - Normalising: remove every space and make letters upper case. A normalised mark is `<cost letters>/<price letters>`: exactly one `/` with at least one letter on each side. - Letter code: code_word has ten different letters. Its first letter stands for the digit 1, the second for 2, and so on up to the ninth for 9; the tenth letter stands for 0. repeat_letter stands for the same digit as the character just before it. Each side of the mark, read left to right, gives the amount in cents (so the digits 1250 mean 12.50). - Malformed: a mark that does not have the shape above, holds a character that is neither a code_word letter nor repeat_letter, or starts either side with repeat_letter is `malformed`; its cost and price are null. - Margins: a readable mark is `below_cost` when the price is less than the cost, then `thin_margin` when the price is less than 1.5 × the cost, and `ok` otherwise. Each book gets the first status that applies, in the order malformed, below_cost, thin_margin, ok. - Shelf value and margin: a shelf's value is the total price of its books whose status is `ok` or `thin_margin`. margin_total is the total of price minus cost over the `ok` books. - Write `out/decoded.json`: `{"books": {"<book_id>": {"status": "<status>", "cost": <dollars or null>, "price": <dollars or null>}, ...}, "status_counts": {"<status>": <number of books>, ...}, "shelf_value": {"<shelf_id>": <dollars>, ...}, "margin_total": <dollars>}`. `books` has one entry per row in books.csv. - Roll-ups: Statuses with no books are included at 0. Shelves in shelves.csv with no ok or thin_margin books are included at 0. ## 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.

Decode a synthetic secondhand bookshop's pencilled marks. Each mark gives a cost and a price in a ten-letter private code word: the first letter is 1, the ninth is 9 and the tenth is 0. A repeat letter stands for the digit before it, and amounts are in cents. Marks were typed by hand, so letter case and spaces must be normalised, and badly shaped marks, unknown letters or a side starting with the repeat letter are malformed. Each book gets the first status that applies: malformed, below_cost, thin_margin (price under 1.5 times cost) or ok. Report each book's status and amounts, status counts, shelf values and the margin total. The prompt says statuses with no books and shelves with no priced books are listed at 0. Prices at exactly 1.5 times cost are a decoy. Volunteer notes get the digit order, repeat letter and margin rules wrong. 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: statuses amounts status_counts shelf_value margin_total

Setup notes: Batch 42 case tu03-secondhand-bookshop-price-code-decoding (offline, synthetic inputs, seed 1363010752). 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 0.51 (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: $0.115589. Score: 5/5. 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: $0.12
Wall time: 18s
Human step-ins: 0
Turns: 3

Model usage
Model	Input tok	Output tok	Cost
AClaude Opus 5.5anthropic/claude-opus-5.5effort default (no --effort flag) · thinking on	58,611	1,791	$0.12

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: statuses amounts status_counts shelf_value margin_total
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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  "result": "I've decoded all 16 marks in `books.csv` and written the results to `out/decoded.json`. I checked the decoding against the printed per-book output; there's no answer key to test it against.\n\n**Status counts:**\n\n| Status | Books |\n|---|---|\n| ok | 12 |\n| thin_margin | 1 |\n| below_cost | 0 |\n| malformed | 3 |\n\n**Margin total:** $140.60\n\n**Shelf values:**\n\n| Shelf | Value |\n|---|---|\n| SH-3 Cookery | $76.00 |\n| SH-5 Local history | $87.00 |\n| SH-7 Poetry | $53.00 |\n| SH-9 Maps and travel | $16.30 |\n| SH-11 Art and design | $0.00 (its only book is malformed) |\n\n**The three malformed books:**\n- **BK-1272** (`xkv/gkv/XKV`) has two `/` characters.\n- **BK-1276** (`xkv/fvr`) contains R, which is neither a code-word letter nor the repeat letter.\n- **BK-1277** (`gvl/LBVV`) has a price side that starts with the repeat letter.\n\n**The only thin-margin book** is BK-1270: it costs $10.00 and is priced at $10.50.\n\nWhere `volunteer-notes.txt` disagreed with the rules, I followed the rules:\n- **Code word:** the first letter stands for 1 and the tenth for 0, not \"first letter is 0\".\n- **Repeat letter:** a mark containing it is still readable. It's only malformed when the letter starts a side. So BK-1270, BK-1224 and BK-1222 decode normally.\n- **Exactly 1.5\u00d7:** a price of exactly 1.5 times the cost counts as `ok`, not thin. BK-1267 ($1.00 cost, $1.50 price) and BK-1262 ($6.00 cost, $9.00 price) fall on that line. I compared in whole cents so rounding couldn't tip them either way.\n- **Empty totals:** below_cost and SH-11 are included at 0 rather than left out.",
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 }
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