{
 "measurement": "Whether ponytail changes what the model writes on a task with real structure to choose, Claude Code 2.1.243",
 "claude_code_version": "2.1.243",
 "trial_date": "2026-08-25",
 "subject": {
  "repo": "DietrichGebert/ponytail",
  "commit": "2ed6c52",
  "version": "4.9.0",
  "its_claim": "The best code is the code you never wrote.",
  "cost_corpus": "/ponytail-session-cost-2-1-243.json",
  "one_liner_corpus": "/ponytail-behaviour-2-1-243.json"
 },
 "task": "Write a Python program in this directory that reads a CSV file of orders (columns: order_id, customer, amount) and reports the total revenue per customer, sorted highest first. Create the files you need.",
 "headline": "On real work the arms do NOT overlap: ponytail wrote 37 to 60 lines against 73 to 88, a gap of 13. The baseline built an argparse CLI in 8 of 8 runs and ponytail in 0 of 8.",
 "this_reverses_the_one_liner_corpus": {
  "what_that_one_found": "ponytail dropped the docstring 8 of 8, and the line counts OVERLAPPED.",
  "what_this_one_finds": "ponytail KEEPS the docstring 8 of 8, and the line counts do NOT overlap.",
  "reading": "Both halves reverse. The effect is real in both trials but expresses differently: on a trivial task the only thing left to cut is cosmetic, so a docstring goes; on a task with structure the docstring stays and an unrequested CLI is what does not get built. The one-liner was the misleading case.",
  "why_it_was_run": "The one-liner corpus named this exact gap as its own limit."
 },
 "method": {
  "task": "Read a CSV of orders and report revenue per customer. Chosen because it leaves room for a CLI, error handling, type hints, a class, a dependency and a test file, so both arms have somewhere to go.",
  "arms": "baseline: empty project, no settings file. ponytail: same, with .claude/settings.json registering hooks/ponytail-activate.js on SessionStart, mode full.",
  "isolation": "--setting-sources project asserted onto the command line on every run.",
  "tools": "--allowedTools Write Read Edit.",
  "metric": "Declared in the harness before any run. Primary: non-blank, non-comment-only lines across every file created, excluding .claude. Features are mechanical regex checks.",
  "not_measured": "Whether the shorter program is BETTER, and whether either program is correct on real data. This counts lines and features.",
  "controls": {
   "arrival": "Each round asked, with the hook installed, which ponytail level was active. 8 of 8 named a level.",
   "rounds_added_before_drafting": "Five rounds were run, then three more before anything was written. On the one-liner task that step reversed the headline; here it held.",
   "usable": "result_guard rejects a run with empty modelUsage or a reported error."
  }
 },
 "results": {
  "baseline": {
   "runs": 8,
   "code_lines": [
    73,
    73,
    75,
    76,
    82,
    83,
    88,
    88
   ],
   "code_lines_range": [
    73,
    88
   ],
   "file_count": [
    2,
    2,
    2,
    2,
    2,
    2,
    2,
    2
   ],
   "features": {
    "has_argparse": 8,
    "has_docstring": 8,
    "has_class": 0,
    "has_test_file": 0,
    "has_try_except": 8,
    "has_type_hints": 0,
    "imports_pandas": 0
   },
   "function_count": [
    2,
    3,
    3,
    3,
    3,
    3,
    3,
    4
   ]
  },
  "ponytail": {
   "runs": 8,
   "code_lines": [
    37,
    37,
    38,
    46,
    49,
    50,
    58,
    60
   ],
   "code_lines_range": [
    37,
    60
   ],
   "file_count": [
    1,
    1,
    1,
    1,
    2,
    2,
    2,
    2
   ],
   "features": {
    "has_argparse": 0,
    "has_docstring": 8,
    "has_class": 0,
    "has_test_file": 1,
    "has_try_except": 8,
    "has_type_hints": 0,
    "imports_pandas": 0
   },
   "function_count": [
    2,
    2,
    3,
    3,
    3,
    3,
    3,
    3
   ]
  },
  "code_lines_overlap": false,
  "gap_between_arms": 13,
  "features_totally_separated": {
   "has_argparse": {
    "baseline": 8,
    "ponytail": 0
   }
  },
  "features_that_did_not_separate": {
   "has_docstring": {
    "baseline": 8,
    "ponytail": 8
   },
   "has_class": {
    "baseline": 0,
    "ponytail": 0
   },
   "has_test_file": {
    "baseline": 0,
    "ponytail": 1
   },
   "has_try_except": {
    "baseline": 8,
    "ponytail": 8
   },
   "has_type_hints": {
    "baseline": 0,
    "ponytail": 0
   },
   "imports_pandas": {
    "baseline": 0,
    "ponytail": 0
   }
  },
  "arrival_control": {
   "named_a_level": 8,
   "of": 8
  },
  "runs_excluded": 0
 },
 "known_limits": {
  "one_task_still": "One CSV-aggregation task. Two tasks now sit behind these claims rather than one, and two is not a survey of programming work.",
  "argparse_is_one_choice_of_many": "The CLI is the single clearest thing the baseline built that nobody asked for. Whether ponytail declines OTHER unrequested structure is not established by one feature.",
  "shorter_is_not_shown_to_be_better": "Neither program was run against real data and neither was reviewed for correctness. A 40 percent shorter program that drops a needed guard would score the same here.",
  "the_baseline_is_not_a_neutral_control": "The baseline is Claude Code with no instructions at all, not a careful engineer. It builds a CLI every time, which is itself a default worth knowing about and is not evidence that ponytail is right.",
  "one_machine_one_release": "Claude Code 2.1.243, one machine, mode full, project scope only."
 },
 "runs": [
  {
   "reply": "The two files are written, but the sandbox blocked running `python3`, so I haven't executed it \u2014 you'll need to run it yourself:\n\n```\npython3 revenue_report.py orders.csv\n```\n\n**`revenue_report.py`** \u2014 takes the CSV path as an argument, sums `amount` per `customer`, prints an aligned table sorted hi",
   "turns": 5,
   "files": [
    "orders.csv",
    "revenue_report.py"
   ],
   "file_count": 2,
   "code_lines": 73,
   "function_count": 3,
   "has_argparse": true,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1001,Alice Chen,249.99\n1002,Bob Ortiz,32.50\n1003,Alice Chen,1120.00\n1004,Dana Feld,87.25\n1005,Bob Ortiz,410.75\n1006,Carlos Reyes,15.00\n1007,Dana Feld,940.10\n1008,Alice Chen,60.01\n1009,Carlos Reyes,205.40\n1010,Bob Ortiz,99.99\n\n#!/usr/bin/env python3\n\"\"\"Report total revenue per customer from a CSV of orders.\n\nUsage: python revenue_report.py orders.csv\n\"\"\"\n\nimport argparse\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\nREQUIRED_COLUMNS = (\"order_id\", \"customer\", \"amount\")\n\n\ndef load_totals(path):\n    \"\"\"Return {customer: Decimal(total)} for the orders in the CSV at `path`.\"\"\"\n    totals = defaultdict(Decimal)\n\n    with open(path, newline=\"\", encoding=\"utf-8-sig\") as f:\n        reader = csv.DictReader(f)\n\n        if reader.fieldnames is None:\n            raise ValueError(\"file is empty (no header row)\")\n\n        missing = [c for c in REQUIRED_COLUMNS if c not in reader.fieldnames]\n        if missing:\n            raise ValueError(f\"missing required column(s): {', '.join(missing)}\")\n\n        for row in reader:\n            customer = (row[\"customer\"] or \"\").strip()\n            raw_amount = (row[\"amount\"] or",
   "cell": "baseline",
   "round": 0,
   "status": "ok",
   "hook_installed": false
  },
  {
   "reply": "`revenue.py` \u2014 one file, stdlib `csv` + `Decimal`, `python3 revenue.py orders.csv`.\n\nSelf-check is built in (`--selfcheck`), but the run was declined by the permission prompt, so it's **unverified** \u2014 run it yourself to confirm.\n\nSkipped: sample CSV, argparse, encoding flag \u2014 add when you need more ",
   "turns": 4,
   "files": [
    "revenue.py"
   ],
   "file_count": 1,
   "code_lines": 38,
   "function_count": 3,
   "has_argparse": false,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "#!/usr/bin/env python3\n\"\"\"Total revenue per customer from an orders CSV (order_id, customer, amount).\"\"\"\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\n\ndef totals(lines):\n    \"\"\"lines: any iterable of CSV text lines. Returns [(customer, total)] desc.\"\"\"\n    per_customer = defaultdict(Decimal)\n    for n, row in enumerate(csv.DictReader(lines), start=2):  # 2 = first data line\n        try:\n            per_customer[row[\"customer\"]] += Decimal(row[\"amount\"].strip())\n        except (InvalidOperation, AttributeError, KeyError):\n            sys.exit(f\"line {n}: bad row {row!r}\")\n    return sorted(per_customer.items(), key=lambda kv: -kv[1])\n\n\ndef main(path):\n    with open(path, newline=\"\") as f:\n        for customer, total in totals(f):\n            print(f\"{customer}\\t{total:.2f}\")\n\n\ndef _selfcheck():\n    rows = \"\"\"order_id,customer,amount\n1,alice,10.50\n2,bob,5\n3,alice,0.01\n4,carol,-2\n\"\"\".splitlines()\n    assert totals(rows) == [\n        (\"alice\", Decimal(\"10.51\")),\n        (\"bob\", Decimal(\"5\")),\n        (\"carol\", Decimal(\"-2\")),\n    ], totals(rows)\n    print(\"ok\")\n\n\nif __name__ == \"__main__\":\n    if len(sys.argv) == 2 and sys.arg",
   "cell": "ponytail",
   "round": 0,
   "status": "ok",
   "hook_installed": true
  },
  {
   "reply": "full",
   "turns": 1,
   "cell": "arrival",
   "round": 0,
   "status": "ok"
  },
  {
   "reply": "Created two files in the working directory:\n\n**`revenue_report.py`** \u2014 the program:\n- `read_orders()` parses the CSV with `csv.DictReader`, validates that `order_id`/`customer`/`amount` are all present, and accumulates per-customer totals using `Decimal` so money doesn't drift the way floats do. Row",
   "turns": 6,
   "files": [
    "orders.csv",
    "revenue_report.py"
   ],
   "file_count": 2,
   "code_lines": 82,
   "function_count": 3,
   "has_argparse": true,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1001,Acme Corp,250.00\n1002,Globex,1200.50\n1003,Acme Corp,99.99\n1004,Initech,430.25\n1005,Globex,75.00\n1006,Hooli,1875.10\n1007,Initech,12.50\n1008,Acme Corp,640.00\n\n#!/usr/bin/env python3\n\"\"\"Report total revenue per customer from a CSV of orders.\n\nUsage:\n    python revenue_report.py orders.csv\n\"\"\"\n\nimport argparse\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\nREQUIRED_COLUMNS = (\"order_id\", \"customer\", \"amount\")\n\n\ndef read_orders(path):\n    \"\"\"Return {customer: total} as Decimals, plus a list of skipped-row warnings.\"\"\"\n    totals = defaultdict(Decimal)\n    warnings = []\n\n    with open(path, newline=\"\", encoding=\"utf-8-sig\") as f:\n        reader = csv.DictReader(f)\n        if reader.fieldnames is None:\n            raise ValueError(f\"{path} is empty\")\n\n        missing = [c for c in REQUIRED_COLUMNS if c not in reader.fieldnames]\n        if missing:\n            raise ValueError(\n                f\"{path} is missing required column(s): {', '.join(missing)}\"\n            )\n\n        for row in reader:\n            customer = (row.get(\"customer\") or \"\").strip()\n            raw_amount = (row.get(\"amount\") or \"\")",
   "cell": "baseline",
   "round": 1,
   "status": "ok",
   "hook_installed": false
  },
  {
   "reply": "`revenue.py` \u2014 one file, stdlib only:\n\n```\npython3 revenue.py orders.csv   # report\npython3 revenue.py --selfcheck  # asserts\n```\n\nDecimal, not float, so `10.05 + 10.10` is exactly `20.15`; ties break alphabetically. Bad amount / blank customer error with the line number instead of silently summing ",
   "turns": 4,
   "files": [
    "revenue.py"
   ],
   "file_count": 1,
   "code_lines": 58,
   "function_count": 3,
   "has_argparse": false,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "#!/usr/bin/env python3\n\"\"\"Total revenue per customer from an orders CSV, highest first.\"\"\"\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\n\ndef totals(rows):\n    \"\"\"rows: dicts with 'customer' and 'amount'. -> [(customer, total)] desc.\"\"\"\n    out = defaultdict(Decimal)\n    for lineno, row in enumerate(rows, 2):  # line 1 is the header\n        customer = (row.get(\"customer\") or \"\").strip()\n        if not customer:\n            raise ValueError(f\"line {lineno}: missing customer\")\n        try:\n            out[customer] += Decimal((row.get(\"amount\") or \"\").strip())\n        except InvalidOperation:\n            raise ValueError(f\"line {lineno}: bad amount {row.get('amount')!r}\") from None\n    return sorted(out.items(), key=lambda kv: (-kv[1], kv[0]))\n\n\ndef report(path):\n    with open(path, newline=\"\", encoding=\"utf-8-sig\") as f:\n        reader = csv.DictReader(f)\n        missing = {\"customer\", \"amount\"} - set(reader.fieldnames or ())\n        if missing:\n            raise ValueError(f\"{path}: missing column(s): {', '.join(sorted(missing))}\")\n        rows = totals(reader)\n    width = max((len(c) for c, _ in rows), default=0)\n    for c",
   "cell": "ponytail",
   "round": 1,
   "status": "ok",
   "hook_installed": true
  },
  {
   "reply": "full",
   "turns": 1,
   "cell": "arrival",
   "round": 1,
   "status": "ok"
  },
  {
   "reply": "Both files are created. Running them to verify needed a permission I don't have here, so the output below is not verified execution \u2014 just the code as written.\n\n**`revenue_report.py`** \u2014 CLI: `python3 revenue_report.py orders.csv`\n\n- Reads with `csv.DictReader`, `utf-8-sig` encoding so a BOM-prefixe",
   "turns": 6,
   "files": [
    "orders.csv",
    "revenue_report.py"
   ],
   "file_count": 2,
   "code_lines": 88,
   "function_count": 4,
   "has_argparse": true,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1001,Alice Chen,249.99\n1002,Bob Ortiz,45.00\n1003,Alice Chen,1200.50\n1004,Priya Nair,899.95\n1005,Bob Ortiz,310.25\n1006,Dana Whitfield,75.00\n1007,Priya Nair,120.00\n1008,Alice Chen,15.75\n1009,Dana Whitfield,640.10\n1010,Bob Ortiz,88.40\n\n#!/usr/bin/env python3\n\"\"\"Report total revenue per customer from a CSV of orders.\n\nUsage:\n    python revenue_report.py orders.csv\n\"\"\"\n\nimport argparse\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\nREQUIRED_COLUMNS = (\"order_id\", \"customer\", \"amount\")\n\n\ndef read_orders(path):\n    \"\"\"Return {customer: total} as Decimals, plus a list of skipped-row warnings.\"\"\"\n    totals = defaultdict(Decimal)\n    warnings = []\n\n    with open(path, newline=\"\", encoding=\"utf-8-sig\") as f:\n        reader = csv.DictReader(f)\n        if reader.fieldnames is None:\n            raise ValueError(\"file is empty (no header row)\")\n\n        missing = [c for c in REQUIRED_COLUMNS if c not in reader.fieldnames]\n        if missing:\n            raise ValueError(\n                \"missing required column(s): %s (found: %s)\"\n                % (\", \".join(missing), \", \".join(reader.fieldnames))\n            )\n\n",
   "cell": "baseline",
   "round": 2,
   "status": "ok",
   "hook_installed": false
  },
  {
   "reply": "`revenue.py` \u2014 one file, stdlib `csv` + `Decimal` (exact money), sorted by total desc then name.\n\n```\npython revenue.py orders.csv   # report\npython revenue.py              # self-check (asserts totals + rejects bad amounts)\n```\n\nI couldn't run the self-check \u2014 the Bash call needs approval, so it's ",
   "turns": 4,
   "files": [
    "revenue.py"
   ],
   "file_count": 1,
   "code_lines": 46,
   "function_count": 3,
   "has_argparse": false,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "\"\"\"Total revenue per customer from an orders CSV, highest first.\n\nUsage: python revenue.py orders.csv\nSelf-check: python revenue.py\n\"\"\"\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\n\ndef revenue_by_customer(lines):\n    \"\"\"lines: any iterable of CSV text lines with header order_id,customer,amount.\"\"\"\n    totals = defaultdict(Decimal)\n    for n, row in enumerate(csv.DictReader(lines), start=2):  # header is line 1\n        customer = (row.get(\"customer\") or \"\").strip()\n        amount = (row.get(\"amount\") or \"\").strip()\n        if not customer or not amount:\n            raise ValueError(f\"line {n}: missing customer or amount\")\n        try:\n            totals[customer] += Decimal(amount)\n        except InvalidOperation:\n            raise ValueError(f\"line {n}: bad amount {amount!r}\") from None\n    return sorted(totals.items(), key=lambda kv: (-kv[1], kv[0]))\n\n\ndef main(path):\n    with open(path, newline=\"\", encoding=\"utf-8\") as f:\n        for customer, total in revenue_by_customer(f):\n            print(f\"{customer}\\t{total}\")\n\n\ndef demo():\n    rows = \"\"\"order_id,customer,amount\n1,alice,10.50\n2,bob,3\n3,alice,0.50\n4,carol,11\n\"\"\".s",
   "cell": "ponytail",
   "round": 2,
   "status": "ok",
   "hook_installed": true
  },
  {
   "reply": "full",
   "turns": 1,
   "cell": "arrival",
   "round": 2,
   "status": "ok"
  },
  {
   "reply": "Both files are written. I tried to run it to verify the output, but the command needed approval and wasn't granted, so the sample run below is untested.\n\n**`revenue_report.py`** \u2014 takes the CSV path as an argument:\n- Uses `csv.DictReader`, so column order doesn't matter; validates that `order_id`, `",
   "turns": 5,
   "files": [
    "orders.csv",
    "revenue_report.py"
   ],
   "file_count": 2,
   "code_lines": 75,
   "function_count": 3,
   "has_argparse": true,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1001,Acme Corp,250.00\n1002,Bluebird LLC,99.50\n1003,Acme Corp,1200.75\n1004,Cypress Ltd,430.10\n1005,Bluebird LLC,15.25\n1006,Acme Corp,60.00\n1007,Cypress Ltd,890.00\n1008,Delta Partners,1750.00\n\n#!/usr/bin/env python3\n\"\"\"Report total revenue per customer from a CSV of orders.\n\nUsage:\n    python revenue_report.py orders.csv\n\"\"\"\n\nimport argparse\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\nREQUIRED_COLUMNS = (\"order_id\", \"customer\", \"amount\")\n\n\ndef read_orders(path):\n    \"\"\"Return {customer: total} as Decimals, plus a list of skipped-row messages.\"\"\"\n    totals = defaultdict(Decimal)\n    problems = []\n\n    with open(path, newline=\"\", encoding=\"utf-8-sig\") as f:\n        reader = csv.DictReader(f)\n        if reader.fieldnames is None:\n            raise ValueError(f\"{path} is empty\")\n\n        headers = [(h or \"\").strip() for h in reader.fieldnames]\n        missing = [c for c in REQUIRED_COLUMNS if c not in headers]\n        if missing:\n            raise ValueError(\n                f\"{path} is missing required column(s): {', '.join(missing)}\"\n            )\n\n        for row in reader:\n            customer = (r",
   "cell": "baseline",
   "round": 3,
   "status": "ok",
   "hook_installed": false
  },
  {
   "reply": "`revenue.py` (+ `orders.csv` sample). `python3 revenue.py orders.csv`; `--demo` runs the assert self-check.\n\nBoth run attempts needed approval, so I haven't executed it \u2014 run `python3 revenue.py --demo` to confirm.\n\nDecimal not float (money); skipped streaming/chunking and CLI flags \u2014 add when a fil",
   "turns": 6,
   "files": [
    "orders.csv",
    "revenue.py"
   ],
   "file_count": 2,
   "code_lines": 37,
   "function_count": 3,
   "has_argparse": false,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1,ann,10.10\n2,bob,5\n3,ann,0.20\n\n\"\"\"Total revenue per customer from an orders CSV (order_id, customer, amount).\"\"\"\n\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\n\ndef revenue_by_customer(rows):\n    \"\"\"rows: iterable of dicts. Returns [(customer, total)] highest first.\"\"\"\n    totals = defaultdict(Decimal)\n    for lineno, row in enumerate(rows, start=2):  # header is line 1\n        try:\n            totals[row[\"customer\"].strip()] += Decimal(row[\"amount\"].strip())\n        except (AttributeError, KeyError, InvalidOperation, TypeError):\n            raise SystemExit(f\"line {lineno}: bad customer/amount in {row!r}\")\n    return sorted(totals.items(), key=lambda kv: -kv[1])\n\n\ndef main(path):\n    with open(path, newline=\"\") as f:\n        for customer, total in revenue_by_customer(csv.DictReader(f)):\n            print(f\"{total:>12.2f}  {customer}\")\n\n\ndef demo():\n    rows = [\n        {\"order_id\": \"1\", \"customer\": \"ann\", \"amount\": \"10.10\"},\n        {\"order_id\": \"2\", \"customer\": \"bob\", \"amount\": \"5\"},\n        {\"order_id\": \"3\", \"customer\": \"ann\", \"amount\": \"0.20\"},\n    ]\n    assert revenue_by_customer(rows) == [(\"a",
   "cell": "ponytail",
   "round": 3,
   "status": "ok",
   "hook_installed": true
  },
  {
   "reply": "full",
   "turns": 1,
   "cell": "arrival",
   "round": 3,
   "status": "ok"
  },
  {
   "reply": "Two files created; running it needs your approval, so I haven't executed it yet.\n\n**`revenue_report.py`** \u2014 CLI script:\n- Reads with `csv.DictReader`, validates the header has `order_id`, `customer`, `amount` (clear error if not).\n- Accumulates per-customer totals in a `defaultdict(float)`; tolerate",
   "turns": 5,
   "files": [
    "orders.csv",
    "revenue_report.py"
   ],
   "file_count": 2,
   "code_lines": 88,
   "function_count": 3,
   "has_argparse": true,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1001,Alice Chen,249.99\n1002,Bob Ortiz,89.50\n1003,Alice Chen,1200.00\n1004,Dana Whitfield,45.00\n1005,Bob Ortiz,310.25\n1006,Chris Nakamura,780.10\n1007,Alice Chen,15.75\n1008,Dana Whitfield,999.99\n1009,Chris Nakamura,120.00\n1010,Bob Ortiz,60.00\n\n#!/usr/bin/env python3\n\"\"\"Report total revenue per customer from a CSV of orders.\n\nUsage:\n    python revenue_report.py orders.csv\n\"\"\"\n\nimport argparse\nimport csv\nimport sys\nfrom collections import defaultdict\n\nREQUIRED_COLUMNS = (\"order_id\", \"customer\", \"amount\")\n\n\ndef read_orders(path):\n    \"\"\"Return {customer: total} for the orders in the CSV at `path`.\n\n    Rows with a blank customer or an unparseable amount are skipped with a\n    warning on stderr, so one bad line doesn't sink the whole report.\n    \"\"\"\n    totals = defaultdict(float)\n\n    with open(path, newline=\"\", encoding=\"utf-8-sig\") as f:\n        reader = csv.DictReader(f)\n\n        if reader.fieldnames is None:\n            raise ValueError(\"file is empty (no header row)\")\n\n        missing = [c for c in REQUIRED_COLUMNS if c not in reader.fieldnames]\n        if missing:\n            raise ValueError(\n                \"missing required column(s): {}; found: {}\".form",
   "cell": "baseline",
   "round": 4,
   "status": "ok",
   "hook_installed": false
  },
  {
   "reply": "Files: `revenue.py`, `orders.csv` (sample).\n\n```\npython3 revenue.py orders.csv     # report\npython3 revenue.py --selfcheck    # asserts\n```\n\nDecimal for money, ties broken by name. I couldn't run the self-check \u2014 the command needed approval \u2014 so it's untested locally.\n\nskipped: argparse, output form",
   "turns": 5,
   "files": [
    "orders.csv",
    "revenue.py"
   ],
   "file_count": 2,
   "code_lines": 60,
   "function_count": 3,
   "has_argparse": false,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1001,Alice,250.00\n1002,Bob,75.50\n1003,Alice,120.25\n1004,Carol,999.99\n1005,Bob,10.00\n\n\"\"\"Total revenue per customer from an orders CSV (order_id, customer, amount).\"\"\"\n\nimport csv\nimport sys\nfrom collections import Counter\nfrom decimal import Decimal\n\n\ndef totals(rows):\n    \"\"\"rows: iterable of dicts. Returns [(customer, Decimal), ...] highest first.\"\"\"\n    t = Counter()\n    for i, row in enumerate(rows, start=2):  # header is line 1\n        customer = (row.get(\"customer\") or \"\").strip()\n        amount = (row.get(\"amount\") or \"\").strip()\n        if not customer or not amount:\n            raise ValueError(f\"line {i}: missing customer or amount\")\n        try:\n            t[customer] += Decimal(amount)\n        except ArithmeticError as e:\n            raise ValueError(f\"line {i}: bad amount {amount!r}\") from e\n    return sorted(t.items(), key=lambda kv: (-kv[1], kv[0]))\n\n\ndef main(path):\n    with open(path, newline=\"\") as f:\n        reader = csv.DictReader(f)\n        missing = {\"customer\", \"amount\"} - set(reader.fieldnames or [])\n        if missing:\n            sys.exit(f\"{path}: missing column(s): {', '.join(sorted(missing))}\")\n        try:\n            report =",
   "cell": "ponytail",
   "round": 4,
   "status": "ok",
   "hook_installed": true
  },
  {
   "reply": "full",
   "turns": 1,
   "cell": "arrival",
   "round": 4,
   "status": "ok"
  },
  {
   "reply": "Both files are created, but I wasn't able to execute the script \u2014 the Bash call needs your approval, so the output below is what it will print, not verified output.\n\n**`revenue_report.py`** \u2014 CLI script:\n- `csv.DictReader`, validates the header has `order_id`, `customer`, `amount` and errors out cle",
   "turns": 5,
   "files": [
    "orders.csv",
    "revenue_report.py"
   ],
   "file_count": 2,
   "code_lines": 83,
   "function_count": 3,
   "has_argparse": true,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1001,Alice Chen,249.99\n1002,Bob Diaz,89.50\n1003,Alice Chen,1200.00\n1004,Carol Nwosu,45.25\n1005,Bob Diaz,310.75\n1006,Dan Iyer,999.99\n1007,Carol Nwosu,610.00\n1008,Alice Chen,75.00\n1009,Dan Iyer,12.49\n1010,Bob Diaz,1500.00\n\n#!/usr/bin/env python3\n\"\"\"Report total revenue per customer from a CSV of orders.\n\nUsage:\n    python revenue_report.py orders.csv\n\"\"\"\n\nimport argparse\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\nREQUIRED_COLUMNS = (\"order_id\", \"customer\", \"amount\")\n\n\ndef read_totals(path):\n    \"\"\"Return {customer: Decimal total} and a list of skipped-row messages.\"\"\"\n    totals = defaultdict(Decimal)\n    problems = []\n\n    with open(path, newline=\"\", encoding=\"utf-8\") as f:\n        reader = csv.DictReader(f)\n        if reader.fieldnames is None:\n            raise ValueError(\"file is empty (no header row)\")\n\n        headers = [h.strip() for h in reader.fieldnames]\n        missing = [c for c in REQUIRED_COLUMNS if c not in headers]\n        if missing:\n            raise ValueError(f\"missing required column(s): {', '.join(missing)}\")\n\n        for row in reader:\n            customer = (row.get(\"custome",
   "cell": "baseline",
   "round": 0,
   "status": "ok",
   "hook_installed": false
  },
  {
   "reply": "`revenue.py` + a sample `orders.csv`:\n\n```\npython3 revenue.py orders.csv     # Ada 130.75 / Bob 104.75 / Cleo 99.00\npython3 revenue.py --selftest\n```\n\nstdlib `csv` + `Counter`; `Decimal` so money doesn't drift; sort is amount desc, name asc for ties.\n\nI couldn't run either command \u2014 permission was d",
   "turns": 5,
   "files": [
    "orders.csv",
    "revenue.py"
   ],
   "file_count": 2,
   "code_lines": 50,
   "function_count": 3,
   "has_argparse": false,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1,Ada,10.50\n2,Bob,99.00\n3,Ada,120.25\n4,Cleo,99.00\n5,Bob,5.75\n\n\"\"\"Total revenue per customer from an orders CSV (order_id, customer, amount).\"\"\"\n\nimport csv\nimport sys\nfrom collections import Counter\nfrom decimal import Decimal, InvalidOperation\n\n\ndef totals(rows):\n    \"\"\"{customer: Decimal} summed from dict rows, ignoring blank customers.\"\"\"\n    out = Counter()\n    for i, row in enumerate(rows, start=2):  # line 1 is the header\n        customer = (row.get(\"customer\") or \"\").strip()\n        try:\n            amount = Decimal((row.get(\"amount\") or \"\").strip())\n        except InvalidOperation:\n            raise SystemExit(f\"line {i}: bad amount {row.get('amount')!r}\")\n        if not customer:\n            raise SystemExit(f\"line {i}: missing customer\")\n        out[customer] += amount\n    return out\n\n\ndef main(path):\n    with open(path, newline=\"\", encoding=\"utf-8-sig\") as f:\n        reader = csv.DictReader(f)\n        missing = {\"customer\", \"amount\"} - set(reader.fieldnames or ())\n        if missing:\n            raise SystemExit(f\"{path}: missing column(s) {', '.join(sorted(missing))}\")\n        result = totals(reader)\n    # sort by amount desc, then name for a st",
   "cell": "ponytail",
   "round": 0,
   "status": "ok",
   "hook_installed": true
  },
  {
   "reply": "full",
   "turns": 1,
   "cell": "arrival",
   "round": 0,
   "status": "ok"
  },
  {
   "reply": "Created two files:\n\n**`revenue_report.py`** \u2014 the program:\n- Reads the CSV with `csv.DictReader`, validates that `order_id`, `customer`, `amount` are all present, and errors out cleanly if not.\n- Sums amounts per customer using `Decimal` so money math doesn't accumulate float drift.\n- Skips rows wit",
   "turns": 4,
   "files": [
    "orders.csv",
    "revenue_report.py"
   ],
   "file_count": 2,
   "code_lines": 73,
   "function_count": 2,
   "has_argparse": true,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1001,Alice Chen,249.99\n1002,Bob Ortiz,89.50\n1003,Alice Chen,1200.00\n1004,Priya Nair,45.25\n1005,Bob Ortiz,310.75\n1006,Priya Nair,999.99\n1007,Alice Chen,15.00\n1008,Dana Weiss,500.00\n\n#!/usr/bin/env python3\n\"\"\"Report total revenue per customer from a CSV of orders.\n\nUsage:\n    python revenue_report.py orders.csv\n\"\"\"\n\nimport argparse\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\nREQUIRED_COLUMNS = (\"order_id\", \"customer\", \"amount\")\n\n\ndef read_totals(path):\n    \"\"\"Return {customer: Decimal total} and a list of skipped-row messages.\"\"\"\n    totals = defaultdict(Decimal)\n    problems = []\n\n    with open(path, newline=\"\", encoding=\"utf-8-sig\") as f:\n        reader = csv.DictReader(f)\n        if reader.fieldnames is None:\n            raise ValueError(f\"{path} is empty\")\n\n        missing = [c for c in REQUIRED_COLUMNS if c not in reader.fieldnames]\n        if missing:\n            raise ValueError(\n                f\"{path} is missing required column(s): {', '.join(missing)}\"\n            )\n\n        # start=2 so the number matches the line in the file (row 1 is the header)\n        for line_no, row in enumerate(re",
   "cell": "baseline",
   "round": 1,
   "status": "ok",
   "hook_installed": false
  },
  {
   "reply": "`revenue.py` (stdlib `csv` + `Counter.most_common`, `Decimal` so money doesn't drift) and `test_revenue.py`.\n\n```\npython3 revenue.py orders.csv\npython3 test_revenue.py   # prints \"ok\"\n```\n\nI couldn't run either \u2014 bash approval was declined, so the check is unrun.\n\nSkipped: CLI flags, currency format",
   "turns": 5,
   "files": [
    "revenue.py",
    "test_revenue.py"
   ],
   "file_count": 2,
   "code_lines": 37,
   "function_count": 2,
   "has_argparse": false,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": true,
   "content": "\"\"\"Total revenue per customer from an orders CSV (order_id, customer, amount).\"\"\"\n\nimport csv\nimport sys\nfrom collections import Counter\nfrom decimal import Decimal, InvalidOperation\n\n\ndef revenue_by_customer(rows):\n    \"\"\"Sum amount per customer. Raises ValueError on a bad amount.\"\"\"\n    totals = Counter()\n    for i, row in enumerate(rows, start=2):  # line 1 is the header\n        try:\n            totals[row[\"customer\"]] += Decimal(row[\"amount\"].strip())\n        except (InvalidOperation, AttributeError, TypeError, KeyError):\n            raise ValueError(f\"line {i}: bad amount {row.get('amount')!r}\")\n    return totals.most_common()\n\n\ndef main(path):\n    with open(path, newline=\"\") as f:\n        for customer, total in revenue_by_customer(csv.DictReader(f)):\n            print(f\"{customer}\\t{total:.2f}\")\n\n\nif __name__ == \"__main__\":\n    if len(sys.argv) != 2:\n        sys.exit(\"usage: revenue.py orders.csv\")\n    main(sys.argv[1])\n\nfrom decimal import Decimal\n\nfrom revenue import revenue_by_customer\n\nrows = [\n    {\"order_id\": \"1\", \"customer\": \"ana\", \"amount\": \"10.10\"},\n    {\"order_id\": \"2\", \"customer\": \"bo\", \"amount\": \"99.00\"},\n    {\"order_id\": \"3\", \"customer\": \"ana\", \"amount\": \"0.20\"},",
   "cell": "ponytail",
   "round": 1,
   "status": "ok",
   "hook_installed": true
  },
  {
   "reply": "full",
   "turns": 1,
   "cell": "arrival",
   "round": 1,
   "status": "ok"
  },
  {
   "reply": "Created two files:\n\n**`revenue_report.py`** \u2014 the program:\n- `read_totals()` (revenue_report.py:17) parses with `csv.DictReader`, validates the three required columns up front, and sums amounts per customer using `Decimal` so money doesn't drift from float rounding. Rows with an unparseable `amount`",
   "turns": 5,
   "files": [
    "orders.csv",
    "revenue_report.py"
   ],
   "file_count": 2,
   "code_lines": 76,
   "function_count": 3,
   "has_argparse": true,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "order_id,customer,amount\n1001,Alice Chen,249.99\n1002,Bob Ortiz,89.50\n1003,Alice Chen,1200.00\n1004,Dana Weiss,45.25\n1005,Bob Ortiz,310.75\n1006,Carlos Reyes,999.00\n1007,Dana Weiss,45.25\n1008,Alice Chen,15.00\n1009,Carlos Reyes,120.40\n1010,Bob Ortiz,7.99\n\n#!/usr/bin/env python3\n\"\"\"Report total revenue per customer from a CSV of orders.\n\nUsage: python revenue_report.py orders.csv\n\"\"\"\n\nimport argparse\nimport csv\nimport sys\nfrom collections import defaultdict\nfrom decimal import Decimal, InvalidOperation\n\nREQUIRED_COLUMNS = (\"order_id\", \"customer\", \"amount\")\n\n\ndef read_totals(path):\n    \"\"\"Return {customer: Decimal(total)} for the orders in the CSV at `path`.\"\"\"\n    totals = defaultdict(Decimal)\n\n    with open(path, newline=\"\", encoding=\"utf-8-sig\") as f:\n        reader = csv.DictReader(f)\n\n        missing = [c for c in REQUIRED_COLUMNS if c not in (reader.fieldnames or [])]\n        if missing:\n            raise SystemExit(\n                f\"{path}: missing required column(s): {', '.join(missing)}\"\n            )\n\n        for row in reader:\n            customer = (row[\"customer\"] or \"\").strip()\n            raw_amount = (row[\"amount\"] or \"\").strip()\n\n            if not customer and not raw_",
   "cell": "baseline",
   "round": 2,
   "status": "ok",
   "hook_installed": false
  },
  {
   "reply": "`revenue.py` \u2014 stdlib `csv` + `Counter` + `Decimal`, sorted by total desc (ties by name).\n\n```\npython3 revenue.py orders.csv     # customer<TAB>total\npython3 revenue.py --selftest     # assert-based check\n```\n\nI couldn't run the self-test \u2014 the Bash calls needed approval and I didn't want to keep re",
   "turns": 5,
   "files": [
    "revenue.py"
   ],
   "file_count": 1,
   "code_lines": 49,
   "function_count": 2,
   "has_argparse": false,
   "has_type_hints": false,
   "imports_pandas": false,
   "has_try_except": true,
   "has_class": false,
   "has_docstring": true,
   "has_test_file": false,
   "content": "\"\"\"Total revenue per customer from an orders CSV (order_id, customer, amount).\"\"\"\n\nimport csv\nimport sys\nfrom collections import Counter\nfrom decimal import Decimal, InvalidOperation\n\n\ndef revenue_by_customer(lines):\n    \"\"\"lines: any iterable of CSV text lines. Returns [(customer, total)] highest first.\"\"\"\n    totals = Counter()\n    reader = csv.DictReader(lines)\n    for n, row in enumerate(reader, start=2):  # header is line 1\n        customer = (row.get(\"customer\") or \"\").strip()\n        raw = (row.get(\"amount\") or \"\").strip()\n        if not customer or not raw:\n            raise ValueError(f\"line {n}: missing customer or amount: {row!r}\")\n        try:\n            totals[customer] += Decimal(raw)\n        except InvalidOperation:\n            raise ValueError(f\"line {n}: bad amount {raw!r}\") from None\n    return sorted(totals.items(), key=lambda kv: (-kv[1], kv[0]))\n\n\ndef _selftest():\n    rows = [\n        \"order_id,customer,amount\",\n        \"1,alice,10.50\",\n        \"2,bob,99.99\",\n        \"3,alice,0.01\",\n        \"4,carol,99.99\",\n    ]\n    assert revenue_by_customer(rows) == [\n        (\"bob\", Decimal(\"99.99\")),\n        (\"carol\", Decimal(\"99.99\")),  # ties break by name\n        (\"ali",
   "cell": "ponytail",
   "round": 2,
   "status": "ok",
   "hook_installed": true
  },
  {
   "reply": "full",
   "turns": 1,
   "cell": "arrival",
   "round": 2,
   "status": "ok"
  }
 ]
}