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Claude Sonnet 5.5 (effort default (no --effort flag) · thinking on) on Work out a tax year's realised gains with FIFO lots, a stock split, cancelled trades, fees and euro-priced shares

AClaude Sonnet 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-21 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first try
Estimated cost
$0.07
Wall time
25s
Human step-ins
0
Outcome
Pass

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Summary

Exact prompt

# Realised gains for the 2026 tax year Inputs: `trades.csv` (every buy, sell and cancellation since the account opened, in no order), `splits.csv`, `fx.csv` (USD per EUR on each EUR trade date) and `request.json`. Report realised gains for sales in the tax year, by symbol, matching each sale to the oldest shares still held (FIFO). - A row with side `cancel` voids the trade named in its `cancels` column; the voided trade never happened. - Sales before the tax year still use up the oldest shares, but their gains aren't reported. - A split with ratio `2:1` doubles the shares held before its effective date and halves their per-share cost; total cost is unchanged. Quantities on trades after the split are already in post-split shares. - Cost basis includes the buy fee; proceeds are net of the sell fee. Fees are in the trade's currency. - Convert EUR trades to USD at that trade date's rate in `fx.csv`, for both cost and proceeds. - Shares held 365 days or fewer are short term; more than 365 days is long term. Holding days = sale date minus buy date. When one sale uses shares from several lots, split its proceeds across them in proportion to the shares. - Work exactly; round only the reported figures to cents, half-up. Write `out/gains.json`: `{"gain_by_symbol": {"<symbol>": <gain, negative for a loss>, ... every symbol with a sale in the tax year}, "short_term_total": <amount>, "long_term_total": <amount>}`. ## 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.

Match 25-50 shuffled trades across 4-6 symbols to FIFO lots and report the tax year's realised gains, split into short and long term. Earlier-year sales use up lots without being reported, one symbol has a 2:1 split, one buy was later cancelled, fees adjust basis and proceeds, and some shares trade in euros at per-day rates. Average cost, keeping the cancelled buy, or ignoring fees and FX each gives different gains. 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: gain_by_symbol short_term long_term costs_fx_and_cancels

Setup notes: Batch 20 case v05-fifo-realised-gains (offline, synthetic inputs, seed 155022302). 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 2.12 (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-sonnet-5.5: $0.068787. Score: 4/4. 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
$0.07
Wall time
25s
Human step-ins
0
Turns
4
Model usage
ModelInput tokOutput tokCost
AClaude Sonnet 5.5anthropic/claude-sonnet-5.5effort default (no --effort flag) · thinking on81,1562,157$0.07

Reproduce this run

  1. Use the use case prompt on the use case page.
  2. 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.
  3. It counts as a success only if it meets every success criterion: gain_by_symbol short_term long_term costs_fx_and_cancels
  4. 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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Evidence log
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  "result": "I wrote `out/gains.json` with the 2026 realised gains by symbol, plus short-term and long-term totals.\n\n| Symbol | Gain (USD) |\n|---|---|\n| KLVA | -3085.75 |\n| LUMA-EU | 399.56 |\n| NRDX | 46.95 |\n| PTRN | -78.93 |\n| VERD-EU | -1129.92 |\n| VNTR | 541.54 |\n\n- **Short-term total:** -153.37\n- **Long-term total:** -3153.17\n\nThe by-symbol gains sum to -3306.55, against -3306.54 for the two totals. That one-cent gap is rounding, since each figure is rounded separately from exact values.\n\nI did not hand-check any lot matching. The only check was that the script ran without errors.\n\n- **Cancellation:** the only cancel row voids PTRN buy `T1216`, so that buy is excluded.\n- **Split:** the single split (LUMA-EU 2:1 on 2025-07-10) doubles the shares of LUMA-EU buys made before that date.\n- **Holding period:** the holding period uses the original buy date.\n- **Sales out of order:** trades are processed in date order, and a buy and a sale on the same day are processed buy first.\n- **Sells before 2026:** they use up the oldest shares but add nothing to the reported gains.",
  "ttft_ms": 5982,
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  "time_to_request_ms": 241,
  "first_content_frame_ms": 5138,
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  "result_index": 0
 }
]

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