Claude Opus 5.5 (effort default (no --effort flag) · thinking on) on Reconcile a messy CSV ledger against bank statements

AClaude Opus 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-16 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.34
Wall time: 1m
Human step-ins: 0
Outcome: Pass

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Exact prompt

You are the bookkeeper for Bramble & Oak Bakery LLC. This folder contains ledger.csv (the general ledger for the business checking account, July-September 2026; amount > 0 is a deposit, amount < 0 is a payment; the opening book balance on July 1, 2026 was 48,213.57 and agreed with the bank) and three bank statement PDFs (statement_2026-07.pdf, statement_2026-08.pdf, statement_2026-09.pdf). pdftotext is installed. Reconcile the ledger against the bank statements for the whole quarter. Ledger entries are often dated 0-3 days before the bank posts them, and ledger descriptions differ from bank descriptions; neither of those is a discrepancy. Report only real discrepancies. Write two files in this folder: 1. discrepancies.csv with header: type,ledger_entry_ids,bank_date,bank_amount,ledger_amount,explanation - type is one of: duplicate_in_ledger, amount_mismatch, sign_error, missing_in_ledger (on the bank statement but not in the ledger), missing_in_bank (in the ledger but never on any statement) - ledger_entry_ids: the ledger entry_id(s) involved, separated by ';' (empty for missing_in_ledger) - bank_date as YYYY-MM-DD (empty if not on the bank statement); amounts as signed numbers without $ or commas 2. reconciliation.json with keys: bank_closing_balance_2026_09_30, ledger_closing_balance_2026_09_30 (opening balance plus all ledger entries), sum_of_adjustments (the net amount your discrepancies add to the ledger balance to reach the bank balance), unexplained_difference (bank closing minus ledger closing minus sum_of_adjustments).

Reconciling a bakery's three-month checking-account ledger (about 1,800 rows) against three PDF bank statements. Twenty-five discrepancies are seeded (duplicates, transposed digits, sign errors and items missing on either side), plus legitimate look-alike purchases as false-positive traps. The agent must list every discrepancy and make the balances reconcile to zero. 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: Finds all 25 seeded discrepancies with ≤ 2 false positives; totals match.

Setup notes: Synthetic bakery checking account: ledger.csv (1821 rows, Jul-Sep 2026) and 3 bank statement PDFs (reportlab) generated by batch2/p07/gen.py (seed 7071026) with 25 seeded discrepancies (6 duplicates, 6 transposed amounts, 3 sign errors, 6 bank-only items, 4 ledger-only items) plus 3 legitimate identical same-day purchases as false-positive traps. Tools: Read/Write/Edit/Glob/Grep/Bash (pdftotext available), web disabled. Scored by batch2/p07/score_p07.py. The financial documents were generated synthetically by a script (not real records). Claude Code's own reported cost for claude-opus-5.5: $0.337514. Score: 25/25 found, 0 false positives. 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: $0.34
Wall time: 1m
Human step-ins: 0
Turns: 9

Model usage
Model	Input tok	Output tok	Cost
AClaude Opus 5.5anthropic/claude-opus-5.5effort default (no --effort flag) · thinking on	220,120	6,827	$0.34

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: Finds all 25 seeded discrepancies with ≤ 2 false positives; totals match.
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 reconciled the quarter and written both files. All discrepancies together account for the full gap between the books and the bank, so the unexplained difference is **0.00**.\n\n**Balances at 9/30/2026**\n- Bank closing balance: 233,555.55. The totals and running balance on each monthly statement add up correctly.\n- Ledger closing balance (opening 48,213.57 plus all 1,821 entries): 230,221.86.\n- Net adjustment from the discrepancies: +3,333.69.\n\n**Discrepancies (25 rows in `discrepancies.csv`)**\n- **Duplicates in ledger (6):** the same charge was entered twice but the bank shows it once:\n  - L00003/L00004\n  - L00228/L00229\n  - L00334/L00335\n  - L00350/L00351\n  - L01222/L01223\n  - L01496/L01497\n- **Amount mismatches (6):** all look like two digits swapped during entry:\n  - L00215: ledger \u221219.71, bank \u221217.91\n  - L00439: ledger \u221233.84, bank \u221238.34\n  - L00478: ledger \u221237.57, bank \u221237.75\n  - L00573: ledger \u221294.49, bank \u221294.94\n  - L00833: ledger 2,659.80, bank 2,659.08 (Square)\n  - L01304: ledger 4,509.82, bank 4,508.92 (Square)\n- **Sign errors (3):** these were entered as payments, but the bank shows them as deposits:\n  - L00100: Costco refund, 226.88\n  - L00534: Amazon refund, 148.27\n  - L00927: customer check, 1,401.38\n- **Missing in ledger (6):** on the bank statement but never recorded:\n  - wire transfer fee, \u221225.00 (7/22)\n  - monthly service fee, \u221235.00 (7/31)\n  - NSF returned item fee, \u221236.00 (8/14)\n  - monthly service fee, \u221235.00 (8/31)\n  - ADP insurance premium, \u2212612.40 (9/9)\n  - interest, +4.18 (9/30)\n- **Missing in bank (4):** in the ledger but on no statement:\n  - L00852: Home Depot, \u221248.19 (8/11)\n  - L01050: Amazon, \u2212137.58 (8/22)\n  - L01120: Costco, \u221249.23 (8/25)\n  - L01739: Shell, \u221252.75 (9/25)\n\n  The first three are well past the normal 0\u20133 day clearing window, so they look like bad entries. L01739 is dated 9/25 and should have posted by 9/28, so it's worth watching the October statement in case it's just late.\n\nNone of these have been corrected in `ledger.csv` itself; the entries are still as they were.",
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