Claude Opus 5.5 (effort default (no --effort flag) · thinking on) on Refactor a legacy freight tariff into structured output while preserving its quirks for old orders

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

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.21
Wall time: 42s
Human step-ins: 0
Outcome: Pass

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Exact prompt

# Refactor a legacy freight tariff without changing old invoices `legacy/tariff.py` is a 2019 script that prints one total per order from a pipe-separated file (`python legacy/tariff.py orders.txt`). Old invoices depend on its **exact** output, quirks included. Write `solve.py` (Python 3 standard library only): `python solve.py input.json answer.json`, where `input.json` has `orders` (each `id`, `date`, `zone`, `kg`, `declared`, `flags`; `orders.txt` holds the same orders in the legacy format). **The `legacy/` directory is deleted before scoring**, so `solve.py` must not import or run it. Fresh order sets are generated. ## Required behaviour 1. Orders dated **before 2027-01-01**: reproduce the legacy script exactly. That covers its `total` string and its `ERROR zone` cases, and every intermediate value as the legacy code computes it: billable kg, the rate it uses, base (after the express doubling), fuel, insurance, discount and the remote charge. Floating-point and formatting quirks included. 2. Orders dated **on or after 2027-01-01** follow the same legacy calculation, except: a. the zone rate is always the order's own zone rate (A, B or C; zone is case-insensitive), with no weight-based switch; any other zone is an error; b. flag `H` (hazmat) adds a flat 15.00 after everything else (not discounted). Before 2027 `H` is ignored, like any unknown flag. 3. Output per order, in input order: `{"id", "billable_kg", "rate", "base", "fuel", "insurance", "discount", "remote", "hazmat", "total"}` with numbers as JSON numbers and `total` as the string the legacy code would print (`"%.2f"`). An error order is `{"id", "error": "zone"}`. `hazmat` is 0 for orders without it, and `remote` is 9.99 or 0. ## answer.json `{"quotes": [...]}` ## Scoring Hidden checks (partial credit; all must pass; values must be equal exactly): `legacy_totals_preserved`, `legacy_breakdown` (pre-2027 orders), `new_rules_totals`, `new_rules_breakdown` (2027+ orders) on the given orders; `fresh_run_1`, `fresh_run_2` (all fields, all orders). 30-second limit per run.

A 'clean' rewrite with exact decimal rounding, or one that fixes the zone bug everywhere, breaks old totals; the legacy file is removed before scoring, so it must be reimplemented. 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. legacy_totals_preserved 2. legacy_breakdown 3. new_rules_totals 4. new_rules_breakdown 5. fresh_run_1 6. fresh_run_2

Setup notes: Use Case Scout batch 12 case m09-legacy-freight-refactor (offline, synthetic fixture). Prepared with batch12/prepare.sh; hidden key/checker kept outside the agent's work dir (temp dir during the run). Prompt = TASK.md verbatim. Scored with the case's scorer: `python score.py WORKDIR KEYDIR` (python3, run from the case dir). Tools: Read/Write/Edit/Glob/Grep/Bash, web disabled. Single run, no retries. 1-min load average at scoring 3.32 (8 cores). Claude Code's own reported cost for claude-opus-5.5: $0.214603. 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.

Metrics

Estimated cost: $0.21
Wall time: 42s
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	109,334	4,164	$0.21

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: 1. legacy_totals_preserved 2. legacy_breakdown 3. new_rules_totals 4. new_rules_breakdown 5. fresh_run_1 6. fresh_run_2
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": "`solve.py` is written, and the pre-2027 totals it produces match the legacy script exactly in both tests I ran:\n\n- **The given orders:** every pre-2027 order matches `legacy/tariff.py` line for line, including the `ERROR zone` cases.\n- **A random fuzz test:** I generated 20,000 random 2026 orders, covering mixed-case and unknown zones, weights around the 30 kg boundary, edge declared values (100, 100.01, 142.85\u2026), and every combination of D/X/R/H flags. There were 0 mismatches against the legacy output.\n\nI only compared printed totals against the legacy script, since that's all it outputs. The pre-2027 breakdown fields come from the same steps that produce those totals, so they should also be right.\n\nThe legacy quirks it keeps:\n- **Unknown zone over 30 kg:** if billable weight is over 30 kg, any zone other than A gets the B rate. So C or `Z` at 40 kg is billed at 5.35, and `Z` is not an error there.\n- **Several discount flags:** only the last `D<n>` flag counts.\n- **Express orders (`X`):** the discount is taken on base + fuel + insurance, not just base + fuel.\n- **Rounding:** each step is rounded with `float('%.2f' % x)`, but the final total adds unrounded floats and is only formatted at the end.\n- **Insurance:** charged only when declared value is over 100, with a minimum of 0.50.\n\nFor orders dated 2027-01-01 or later:\n- The rate is the order's own zone rate (A, B or C, any case), and any other zone returns `{\"id\", \"error\": \"zone\"}`.\n- `H` adds 15.00 after the remote charge and is not discounted. Before 2027 `H` is ignored.\n\nOutput is written as `{\"quotes\": [...]}` in input order. `remote` is 9.99 or 0, `hazmat` is 15.0 or 0, and `total` is the `\"%.2f\"` string. The script uses only the standard library and doesn't touch `legacy/`.",
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