Claude Opus 5.5 (effort default (no --effort flag) · thinking on) on Build a csvq CLI (select/where/sort/limit/count, csv|json|table output, exact exit codes) from a written spec

AClaude Opus 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-17 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.22
Wall time: 55s
Human step-ins: 0
Outcome: Pass

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Exact prompt

# Task: build the `csvq` command-line tool Write `csvq.py` (Python 3 standard library only, run as `python3 csvq.py ...`). It reads CSV (RFC 4180 quoting, UTF-8, header row required) from a file argument or from stdin when the file is `-` or omitted, and writes to stdout. `people.csv` is a sample. Options (may appear in any order): - `--select COLS` comma-separated column names to output, in that order (default: all, original order). - `--where EXPR` repeatable; all must match. EXPR is `col OP value` with OP one of `=`, `!=`, `<`, `<=`, `>`, `>=`, `~` (case-insensitive substring). If both the cell and value parse as numbers, compare numerically, otherwise as strings. An empty cell never matches `<`,`<=`,`>`,`>=`. - `--sort COL` ascending; `--sort -COL` descending. Numeric if every non-empty value in the column is a number, else string. Empty cells always sort last (both directions). Sort is stable. - `--limit N` output at most N rows (after filtering and sorting). - `--format csv|json|table` (default csv). csv: header + rows, quoted as needed by Python's csv module, `\n` line endings. json: a JSON array of objects (keys in output column order, all values strings), `ensure_ascii=False`, followed by a newline. table: columns left-aligned, padded to the widest cell (header included) with two spaces between columns, no trailing spaces, a dashes line under the header the width of each column. - `--count` print only the number of matching rows (after --where, ignoring --limit) and a newline. - `-h/--help` usage, exit 0. Errors go to stderr with a one-line message and a non-zero exit: unknown column (in any option) exits 2; bad usage (unknown option, bad --where, non-integer/negative --limit, bad --format) exits 2; unreadable input file exits 1. Nothing is printed to stdout on error. No network.

Byte-exact output: RFC 4180 quoting, numeric-vs-string comparison, empty cells sorting last in both directions, stable descending sort, `--sort -COL` argument parsing, table padding without trailing spaces, and distinct exit codes with clean stdout on error. 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. 21 hidden invocations (alternating file argument and stdin) produce byte-identical stdout and exit code 0, or for error cases the exact exit code 2 with empty stdout and a stderr message. 2. A missing input file exits 1 with empty stdout and a stderr message. 3. -h exits 0 and its usage text mentions --where. 4. Reading stdin via '-' works.

Setup notes: Use Case Scout batch 5 case e04-csvq-cli (offline fixture). Prepared with batch5/prepare.sh; hidden key/tests kept outside the agent's work dir. Prompt = TASK.md verbatim. Scored with the scout's scorer: `python score.py WORKDIR KEYDIR`. Tools: Read/Write/Edit/Glob/Grep/Bash, web disabled. Single run, no retries. Claude Code's own reported cost for claude-opus-5.5: $0.217551. Score: 24/24. 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: $0.22
Wall time: 55s
Human step-ins: 0
Turns: 4

Model usage
Model	Input tok	Output tok	Cost
AClaude Opus 5.5anthropic/claude-opus-5.5effort default (no --effort flag) · thinking on	83,296	5,436	$0.22

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. 21 hidden invocations (alternating file argument and stdin) produce byte-identical stdout and exit code 0, or for error cases the exact exit code 2 with empty stdout and a stderr message. 2. A missing input file exits 1 with empty stdout and a stderr message. 3. -h exits 0 and its usage text mentions --where. 4. Reading stdin via '-' works.
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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  "stop_reason": "end_turn",
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   "output_tokens_details": {
    "thinking_tokens": 1052
   },
   "server_tool_use": {
    "web_search_requests": 0,
    "web_fetch_requests": 0
   },
   "service_tier": "standard",
   "cache_creation": {
    "ephemeral_1h_input_tokens": 11813,
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   "inference_geo": "global",
   "iterations": [
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     "output_tokens": 876,
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     "cache_creation": {
      "ephemeral_5m_input_tokens": 0,
      "ephemeral_1h_input_tokens": 1267
     },
     "type": "message"
    }
   ],
   "speed": "standard",
   "fallback_credit": null
  },
  "modelUsage": {
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    "inputTokens": 8,
    "outputTokens": 5436,
    "cacheReadInputTokens": 71475,
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    "webSearchRequests": 0,
    "costUSD": 0.217551,
    "contextWindow": 1000000,
    "maxOutputTokens": 128000,
    "thinkingTokens": 1052,
    "canonicalModel": "claude-opus-5-5",
    "provider": "firstParty",
    "costBasis": "list"
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  },
  "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
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   "started_in_background": 0,
   "max_depth": 0,
   "spawned_by_subagents": 0,
   "completed": 0,
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   "killed": {
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   "refused": {
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  "safety_stops": 0,
  "is_error": false,
  "num_turns": 4,
  "subtype": "success",
  "api_error_status": null,
  "result": "I've written `csvq.py`, using only the Python standard library. I ran it by hand against `people.csv` and every behaviour I checked matched the spec. I didn't write an automated test suite.\n\n**What I checked:**\n- **Output formats:** csv (including values that need quoting, like `\"Austin, TX\"` and `\"Faye \"\"Fi\"\" Ortiz\"`), json, and table with the dashes line.\n- **Sorting:** ascending and descending, numeric where the column is all numbers. The empty `age` cell sorts last both ways, and the two 28s keep their original order.\n- **`--where`:** numeric comparison (`age<30` gives 3), case-insensitive substring (`city~austin`), several `--where` options combined, and a value containing a comma (`city=Austin, TX`).\n- **Other options:** `--limit`, `--count`, reading from stdin with `-`, and `-h`, which exits 0.\n- **Errors:** an unknown column in `--select`, `--where` or `--sort`, an unknown option, a bad `--where`, a `--limit` of `-1` or `x`, and a bad `--format` all exit 2 with a one-line message on stderr and nothing on stdout. A missing file exits 1.\n\n**Choices I made where the spec is silent:**\n- **Number detection:** values like `-3`, `4.5` and `1e3` count as numbers; `nan`, `inf` and `1_000` don't.\n- **`--where` parsing:** spaces around the operator are ignored, and `!=`, `<=`, `>=` are matched before `=`, `<`, `>`. An empty value (`city=`) is allowed and matches empty cells.\n- **Short or long rows:** short rows are padded with empty cells, extra cells are ignored, and blank lines are skipped. A leading byte-order mark (BOM) is stripped.\n- **Unreadable input:** an empty input (no header), invalid UTF-8 or malformed CSV exits 1, the same as an unreadable file.\n- **Error order:** usage errors are checked before the file is read. So a bad option exits 2 even if the file is missing, but an unknown column with a missing file exits 1, since the columns can't be known.\n- **Extra syntax:** `--opt=value` works as well as `--opt value`, and `--` ends option parsing.\n- **`--count`:** it still checks the `--select` and `--sort` columns, so an unknown column there exits 2.",
  "ttft_ms": 3303,
  "type": "result",
  "duration_ms": 54841,
  "uuid": "[REDACTED]",
  "ttft_stream_ms": 2377,
  "time_to_request_ms": 280,
  "first_content_frame_ms": 2377,
  "queued_turn_count": 0,
  "result_index": 0
 }
]