{
  "entity": "deepseek-v4-pro",
  "entity_type": "model",
  "category": "Coding",
  "suite": "suite-2026-08-skills/coding",
  "model": "deepseek/deepseek-v4-pro",
  "judges": [
    "anthropic/claude-sonnet-5",
    "google/gemini-3.1-pro-preview",
    "openai/gpt-5.6-terra"
  ],
  "judge_protocol": "judge-2026-08",
  "anchors": "solo-2026-08-a",
  "score": 83,
  "caps": 0,
  "cost_usd": 0.2334,
  "started_at": "2026-08-16T06:22:35.243Z",
  "finished_at": "2026-08-16T06:25:02.723Z",
  "tasks": [
    {
      "id": "c1",
      "name": "Duration parser",
      "prompt": "Write a Python function parse_duration(s) that converts strings like '1h30m', '45s', '2h', '90m', '1h2m3s' into total seconds. Raise ValueError on anything malformed. Include three assert-based tests, one of which covers a malformed input.",
      "output": "```python\nimport re\n\ndef parse_duration(s: str) -> int:\n    \"\"\"\n    Parse a duration string like '1h30m', '45s', '2h', '90m', '1h2m3s'\n    into the total number of seconds.\n    \n    Raises ValueError if the string is malformed.\n    \"\"\"\n    # The pattern enforces order: hours (h), then minutes (m), then seconds (s).\n    # Each component is optional, but at least one must be present.\n    pattern = r'^(?:(\\d+)h)?(?:(\\d+)m)?(?:(\\d+)s)?$'\n    match = re.fullmatch(pattern, s)\n    if not match:\n        raise ValueError(f\"Malformed duration string: {s!r}\")\n    \n    h, m, sec = match.groups()\n    # At least one of the groups must have been matched.\n    if h is None and m is None and sec is None:\n        raise ValueError(f\"Duration string must contain at least one component: {s!r}\")\n    \n    hours = int(h) if h else 0\n    minutes = int(m) if m else 0\n    seconds = int(sec) if sec else 0\n    \n    return hours * 3600 + minutes * 60 + seconds\n\n\nif __name__ == '__main__':\n    # Valid inputs\n    assert parse_duration('1h30m') == 5400   # 1 hour 30 minutes\n    assert parse_duration('45s') == 45       # 45 seconds\n    \n    # Malformed input – '1h30' is missing a unit for 30\n    try:\n        parse_duration('1h30')\n        assert False, \"ValueError should have been raised for '1h30'\"\n    except ValueError:\n        pass   # expected behaviour\n    \n    print(\"All tests passed.\")\n```",
      "latency_ms": 35045,
      "cost": 0.0021208824,
      "task_score": 8,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 8,
          "violates": false,
          "reasoning": "Correct, robust implementation with proper regex, handles empty string edge case, includes required tests. Minor: empty string '' matches pattern but caught by explicit check. Clear and concise."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response provides a correct and robust Python function, handles the specified formats, raises ValueError on malformed inputs, and includes exactly three assert-based tests as requested."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 8,
          "violates": false,
          "reasoning": "Correctly parses the specified formats and rejects empty, out-of-order, duplicate, and unitless inputs. It includes three assert statements, with malformed input tested via try/except. Minor polish: malformed-input testing could use a clear"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c2",
      "name": "Find the bug",
      "prompt": "This is meant to return the average of the positive numbers but returns the wrong value. Identify the bug, explain it in one sentence, and give the corrected function.\n\nfunction avgPositive(xs) {\n  let sum = 0, n = 0;\n  for (const x of xs) {\n    if (x > 0) sum += x;\n    n++;\n  }\n  return sum / n;\n}",
      "output": "The bug is that `n` is incremented for every element in the array, not just the positive ones, so the sum is divided by the total number of elements instead of the count of positive numbers.\n\n```javascript\nfunction avgPositive(xs) {\n  let sum = 0, n = 0;\n  for (const x of xs) {\n    if (x > 0) {\n      sum += x;\n      n++;\n    }\n  }\n  return n === 0 ? 0 : sum / n;\n}\n```",
      "latency_ms": 15569,
      "cost": 0.00131240418,
      "task_score": 9,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Correctly identifies bug, explains in one sentence, provides corrected function with sensible zero-division guard. Clear and concise, meets task requirements fully."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response perfectly identifies the bug, explains it in exactly one sentence, and provides a corrected function that also smartly handles the divide-by-zero edge case."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 8,
          "violates": false,
          "reasoning": "It correctly identifies that the count must include only positive values and fixes the loop accordingly. The added zero-count fallback is reasonable but changes unspecified behavior for arrays with no positive numbers."
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c3",
      "name": "SQL without window functions",
      "prompt": "Given tables users(id, email) and orders(id, user_id, created_at, total), write SQL returning the email and order count of every user with more than 3 orders in the last 30 days, most orders first. Do not use window functions. Target Postgres.",
      "output": "```sql\nSELECT u.email, COUNT(o.id) AS order_count\nFROM users u\nJOIN orders o ON o.user_id = u.id\nWHERE o.created_at >= NOW() - INTERVAL '30 days'\nGROUP BY u.id, u.email\nHAVING COUNT(o.id) > 3\nORDER BY order_count DESC;\n```",
      "latency_ms": 11082,
      "cost": 0.001012158,
      "task_score": 10,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Correct, valid Postgres SQL, no window functions, meets all constraints, clear and concise."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The SQL query is perfectly accurate, targets Postgres correctly, follows all instructions including the negative constraint, and is concise and clear."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 10,
          "violates": false,
          "reasoning": "Correct Postgres query: joins users to orders, filters the last 30 days, groups per user, retains counts above 3, and sorts descending. It uses no window functions and includes every qualifying user."
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c4",
      "name": "Infinite useEffect",
      "prompt": "Explain precisely why this React effect loops forever, then give the fixed version.\n\nconst [items, setItems] = useState([]);\nuseEffect(() => {\n  fetch('/api/items').then(r => r.json()).then(setItems);\n}, [items]);",
      "output": "The effect loops forever because the **`items` state is both the dependency and the value being updated** inside the effect. Each time the effect runs, it fetches data and calls `setItems()` with a **new array reference** (even if the content is identical). React’s `useEffect` compares the dependency `items` by reference (`Object.is`), sees it has changed, and schedules the effect again. This creates a cycle:\n\n1. Component mounts → effect runs → fetch → `setItems(newArray)`  \n2. State updates → re-render with `newArray`  \n3. `items` dependency changed (new reference) → effect runs again → fetch → `setItems(newerArray)`  \n4. …repeat indefinitely.\n\n---\n\n**Fixed version**  \nRemove `items` from the dependency array so the effect only runs once on mount (or based on other stable dependencies).\n\n```javascript\nconst [items, setItems] = useState([]);\nuseEffect(() => {\n  fetch('/api/items').then(r => r.json()).then(setItems);\n}, []); // runs only once on mount\n```",
      "latency_ms": 8946,
      "cost": 0.0006019104,
      "task_score": 10,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 8,
          "violates": false,
          "reasoning": "Accurate explanation and correct fix; slight imprecision equating reference change cause but functionally correct. Clear, concise, useful for non-technical reader despite technical jargon."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response accurately and concisely explains the infinite loop caused by referential inequality and state updates in the dependency array, and provides the correct fix."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 10,
          "violates": false,
          "reasoning": "Precisely identifies the state-update/dependency reference cycle, correctly notes Object.is reference comparison and new fetched array references, and provides the appropriate empty-dependency fix for a mount-only fetch. Clear, concise, and"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c5",
      "name": "Typed debounce",
      "prompt": "Write a debounce function in TypeScript that preserves the argument types of the wrapped function, returns a function with a .cancel() method, and does not use 'any'. Explain in one sentence why the naive generic signature loses type information.",
      "output": "```typescript\nfunction debounce<T extends (...args: any[]) => any>(\n  fn: T,\n  delay: number\n): ((...args: Parameters<T>) => void) & { cancel: () => void } {\n  let timer: ReturnType<typeof setTimeout> | undefined;\n\n  const debounced = function (this: unknown, ...args: Parameters<T>): void {\n    if (timer !== undefined) {\n      clearTimeout(timer);\n    }\n    timer = setTimeout(() => {\n      fn.apply(this, args);\n    }, delay);\n  };\n\n  debounced.cancel = () => {\n    if (timer !== undefined) {\n      clearTimeout(timer);\n      timer = undefined;\n    }\n  };\n\n  return debounced as ((...args: Parameters<T>) => void) & { cancel: () => void };\n}\n```\n\n**Why the naive generic signature loses type information:**  \nA naive signature like `(...args: any[]) => void` discards the specific parameter types of the original function, replacing them with `any` and thus destroying all type safety and editor autocompletion for the debounced call.",
      "latency_ms": 57550,
      "cost": 0.01056779424,
      "task_score": 3,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 3,
          "violates": true,
          "reasoning": "Uses 'any' twice (constraint T extends (...args: any[])=>any) despite explicit 'no any' requirement, directly violating instructions."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 5,
          "violates": true,
          "reasoning": "The response uses the forbidden word 'any' multiple times in the TypeScript code and explanation, violating the negative constraint."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 3,
          "violates": true,
          "reasoning": "It preserves Parameters<T> and provides cancel(), with a correct explanation, but explicitly uses 'any' twice despite the prohibition. It also does not preserve a wrapped function’s this type, and may face apply typing issues under strict s"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c6",
      "name": "Leftmost binary search",
      "prompt": "Implement binary search that returns the index of the FIRST occurrence of a target in a sorted array with duplicates, or -1. Give the code and state the complexity. Include the test case that distinguishes it from an ordinary binary search.",
      "output": "Below is a Python implementation of binary search that finds the **first occurrence** of a target in a sorted array (with duplicates). It returns the index of that first occurrence, or `-1` if the target is not present.\n\n```python\ndef binary_search_first(arr, target):\n    \"\"\"\n    Returns the index of the first occurrence of target in a sorted array.\n    If target is not found, returns -1.\n    \"\"\"\n    low, high = 0, len(arr) - 1\n    result = -1\n\n    while low <= high:\n        mid = (low + high) // 2\n        if arr[mid] == target:\n            result = mid        # record the match\n            high = mid - 1      # continue searching left for an earlier occurrence\n        elif arr[mid] < target:\n            low = mid + 1\n        else:\n            high = mid - 1\n\n    return result\n```\n\n### Complexity\n- **Time:** O(log n) – the search space is halved each iteration, even when duplicates exist.\n- **Space:** O(1) – only a few variables are used.\n\n### Distinguishing Test Case\nAn ordinary binary search that stops at the first match it finds would return **any** index where the target appears. The test below shows why the modified version is necessary:\n\n```python\narr = [1, 2, 2, 2, 3, 4]\ntarget = 2\n\n# Ordinary binary search (stops at first match) might return 2 or 3.\n# First-occurrence binary search must return 1.\nprint(binary_search_first(arr, target))  # Output: 1\n```\n\n**Explanation:**  \n- The array contains three `2`s at indices 1, 2, and 3.  \n- A naive binary search could land on `mid = 2` first and return `2`.  \n- The first-occurrence version continues searching the left half after finding a match, eventually locating index `1`.",
      "latency_ms": 13005,
      "cost": 0.0005572722505,
      "task_score": 10,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Correct implementation, correct complexity, clear distinguishing test case demonstrating difference from ordinary binary search. Concise and well-explained."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response perfectly implements the requested algorithm, accurately states the time and space complexity, and provides a clear test case demonstrating the difference from standard binary search."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 10,
          "violates": false,
          "reasoning": "Correct first-occurrence binary search: records matches and continues left. Correct O(log n) time and O(1) space. Includes a clear duplicate-containing test case showing ordinary binary search may return a later occurrence."
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c7",
      "name": "Security review",
      "prompt": "Review this Express handler and list every security problem you find, most severe first, each with the fix.\n\napp.get('/file', (req, res) => {\n  const p = req.query.name;\n  db.query(`SELECT * FROM files WHERE name = '${p}'`, (e, rows) => {\n    res.sendFile(__dirname + '/uploads/' + p);\n  });\n});",
      "output": "Here are the security problems, ordered from most severe to least:\n\n---\n\n### 1. SQL Injection (Critical)\n**Problem:**  \nThe `name` parameter is directly interpolated into the SQL query string using `'${p}'`. An attacker can supply a value like `' OR '1'='1` to manipulate the query, potentially reading, modifying, or deleting any data in the database, or even executing operating system commands depending on the database configuration.\n\n**Fix:**  \nUse parameterized queries (prepared statements) to completely separate code from data.  \n```javascript\ndb.query(`SELECT * FROM files WHERE name = ?`, [p], (e, rows) => {\n  // ...\n});\n```\n\n---\n\n### 2. Path Traversal / Directory Traversal (High)\n**Problem:**  \n`res.sendFile(__dirname + '/uploads/' + p)` uses the unsanitized user input `p` to construct a file system path. An attacker can supply `../config/secrets` or `../../etc/passwd` to read arbitrary files outside the intended `uploads` directory.\n\n**Fix:**  \nUse the `root` option of `res.sendFile` to confine the path to the uploads directory. Express will then resolve the filename relative to that root and reject any path that traverses outside it.  \n```javascript\nconst path = require('path');\napp.get('/file', (req, res) => {\n  const p = req.query.name;\n  // ... (parameterized query)\n  const uploadsDir = path.join(__dirname, 'uploads');\n  res.sendFile(p, { root: uploadsDir }, (err) => {\n    if (err) res.status(404).send('File not found');\n  });\n});\n```\nAdditionally, validate that `p` contains only expected filename characters (e.g., alphanumeric, underscores, dots) and reject anything else as an extra layer of defense.\n\n---\n\n### 3. Missing Input Validation (Medium)\n**Problem:**  \nEven after fixing traversal, the application accepts any string as a filename with no validation on length, character set, or format. This could lead to unexpected behavior, denial-of-service (extremely long names), or bypass attempts using null bytes, control characters, etc.\n\n**Fix:**  \nWhitelist allowed characters (e.g., `/^[a-zA-Z0-9_.-]+$/`) and enforce a reasonable maximum length. Reject any request that doesn’t match.\n\n---\n\n### 4. Unused Query Result & Ignored Database Error (Low)\n**Problem:**  \nThe callback from the database query ignores the `e` error and the `rows` result. If the query fails (e.g., due to the SQL injection or a legitimate error), the application still attempts to send the file, potentially serving a file when it shouldn’t or leaking information through error pages in development mode. The result of the query is not used for authorization or existence checks, which may indicate a logic flaw.\n\n**Fix:**  \nHandle the error explicitly and decide on the appropriate response (e.g., log the error, return a 500 status). If the query is meant to check file existence or permissions, use the result to decide whether to serve the file.\n```javascript\ndb.query(`SELECT * FROM files WHERE name = ?`, [p], (e, rows) => {\n  if (e) {\n    console.error(e);\n    return res.status(500).send('Internal server error');\n  }\n  if (rows.length === 0) {\n    return res.status(404).send('File not found');\n  }\n  // serve file only if authorized\n});\n```\n\n---\n\n**Summary of severity:**  \n1. **SQL Injection** – Critical (complete database compromise)  \n2. **Path Traversal** – High (read arbitrary files)  \n3. **Missing Input Validation** – Medium (facilitates other attacks, DoS)  \n4. **Unhandled Errors / Unused Result** – Low (logic flaw, potential information exposure)",
      "latency_ms": 44585,
      "cost": 0.00772851108,
      "task_score": 9,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Accurate, thorough, well-ordered by severity with concrete fixes and code. Covers SQL injection, path traversal, validation, error handling. Minor: could mention authorization check missing more explicitly, but overall excellent and useful."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response accurately identifies all security vulnerabilities, orders them correctly by severity, and provides clear, effective fixes for each. It is highly useful and well-structured."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 7,
          "violates": false,
          "reasoning": "Correctly identifies SQL injection, traversal, validation, and error/result handling with practical fixes. It likely misses explicit broken access control/IDOR: any caller can request an existing filename. SQL-injection impact is overstated"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c8",
      "name": "Safe migration",
      "prompt": "Write the Postgres migration to add a NOT NULL column 'status' with default 'pending' to an orders table with 40 million rows, without taking a long exclusive lock. Give the steps in order and say which step is the dangerous one and why.",
      "output": "Here’s a safe, lock‑friendly migration plan for adding a `NOT NULL` column with a default value to a 40‑million‑row `orders` table. The steps are ordered to avoid long‑held exclusive locks.\n\n---\n\n### Step‑by‑step migration\n\n1. **Add the column as nullable with the default value**  \n   ```sql\n   ALTER TABLE orders ADD COLUMN status TEXT DEFAULT 'pending';\n   ```\n   - In PostgreSQL ≥ 11 this is a metadata‑only change (no table rewrite) and completes almost instantly.\n   - New rows immediately receive `'pending'`; existing rows still show `NULL` until backfilled.\n\n2. **Backfill existing rows in small batches**  \n   Run a loop that updates a limited number of rows per transaction, e.g.:\n   ```sql\n   DO $$\n   DECLARE\n     rows_updated INT;\n   BEGIN\n     LOOP\n       WITH batch AS (\n         SELECT ctid\n         FROM orders\n         WHERE status IS NULL\n         LIMIT 10000\n       )\n       UPDATE orders\n       SET status = 'pending'\n       WHERE ctid IN (SELECT ctid FROM batch);\n       \n       GET DIAGNOSTICS rows_updated = ROW_COUNT;\n       EXIT WHEN rows_updated = 0;\n       COMMIT; -- each batch is its own transaction\n     END LOOP;\n   END $$;\n   ```\n   - Keeps individual transactions short, avoids long‑held row locks, and does not block normal read/write activity.\n\n3. **Add a `NOT VALID` check constraint to enforce `NOT NULL`**  \n   ```sql\n   ALTER TABLE orders ADD CONSTRAINT status_not_null CHECK (status IS NOT NULL) NOT VALID;\n   ```\n   - This is a fast, catalog‑only operation (acquires a very brief `ACCESS EXCLUSIVE` lock).\n   - The constraint is immediately enforced for new and updated rows, but existing rows are not yet validated.\n\n4. **Validate the constraint online**  \n   ```sql\n   ALTER TABLE orders VALIDATE CONSTRAINT status_not_null;\n   ```\n   - Takes a `SHARE UPDATE EXCLUSIVE` lock, which allows concurrent reads, writes, and inserts.\n   - Scans the table to confirm no `NULL` values remain. Because we backfilled in step 2, this scan will pass quickly (though it still reads the whole table).\n\n5. **(Optional) Convert to a true `NOT NULL` constraint**  \n   If your tooling or ORM expects a real column `NOT NULL` rather than a check constraint, you can now safely run:\n   ```sql\n   ALTER TABLE orders ALTER COLUMN status SET NOT NULL;\n   ```\n   - Since the column contains no `NULL`s, the mandatory scan is fast, but it still requires an `ACCESS EXCLUSIVE` lock.  \n   - In most cases the `CHECK (status IS NOT NULL)` constraint is functionally identical, so this step can be skipped.\n\n---\n\n### Which step is dangerous and why?\n\n**The dangerous step is adding a `NOT NULL` constraint directly (i.e. `ALTER TABLE … ALTER COLUMN SET NOT NULL`) without using the `NOT VALID` check constraint approach.**  \n\n- **Why it’s dangerous:**  \n  `ALTER COLUMN SET NOT NULL` acquires an `ACCESS EXCLUSIVE` lock on the table and then performs a full table scan to verify that no `NULL` values exist. On a 40‑million‑row table, this scan can take many seconds to minutes, during which **all other reads and writes are blocked**. This causes application downtime or severe latency spikes.\n\n- **How the plan avoids it:**  \n  By using a `CHECK` constraint with `NOT VALID` (step 3) and validating it later (step 4), the exclusive lock is held only for a split second during catalog changes, and the validation scan runs under a much weaker lock that does not disrupt normal operations.",
      "latency_ms": 46854,
      "cost": 0.0019424984595,
      "task_score": 5,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Accurate, well-ordered migration steps with correct Postgres locking behavior, clearly identifies the dangerous step and rationale. Minor optional final step slightly muddies the danger point but overall excellent and clear."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 4,
          "violates": false,
          "reasoning": "Factual error: In Postgres 11+, adding a column with a default value makes existing rows return the default, not NULL. Thus, adding a NOT NULL column with a default is a single, instant metadata operation."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 5,
          "violates": false,
          "reasoning": "Core approach is mostly sound for PostgreSQL 11+, but existing rows logically read the fast-default value, so the backfill is unnecessary. A validated equivalent CHECK can let SET NOT NULL avoid its scan; calling it mandatory and dangerous "
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c9",
      "name": "Fix the code not the test",
      "prompt": "This test fails. Fix the implementation, not the test.\n\n// impl\nexport const slugify = (s) => s.toLowerCase().replace(/ /g, '-');\n// test\nexpect(slugify('  Hello   World!  ')).toBe('hello-world');",
      "output": "The original implementation only lowercases and replaces spaces with dashes, ignoring multiple spaces, leading/trailing spaces, and non‑alphanumeric characters like `!`. To pass the test, the function must also trim whitespace, collapse repeated spaces, and strip punctuation.\n\nHere’s the corrected implementation:\n\n```javascript\nexport const slugify = (s) =>\n  s\n    .toLowerCase()\n    .replace(/[^a-z0-9\\s]+/g, '')   // remove non-alphanumeric except spaces\n    .trim()                         // remove leading/trailing whitespace\n    .replace(/\\s+/g, '-');          // collapse spaces into a single dash\n```\n\nThis will transform `'  Hello   World!  '` into `'hello-world'`, exactly matching the expectation.",
      "latency_ms": 15535,
      "cost": 0.0009706008,
      "task_score": 10,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Correct fix, verified logic works, clear explanation, concise."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response correctly identifies the issues with the original implementation and provides a flawless, concise fix that passes the test."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 10,
          "violates": false,
          "reasoning": "Correctly fixes the implementation rather than altering the test. It lowercases, removes punctuation, trims leading/trailing whitespace, and collapses whitespace into hyphens, producing the required \"hello-world\" output clearly and concisel"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c10",
      "name": "Race condition",
      "prompt": "Identify the race condition in this code, explain what interleaving causes it, and fix it.\n\nlet cache = null;\nasync function getConfig() {\n  if (cache) return cache;\n  const r = await fetch('/config');\n  cache = await r.json();\n  return cache;\n}",
      "output": "The race condition occurs because the `cache` variable is only set **after** the asynchronous `fetch` and JSON parsing complete. If `getConfig()` is called multiple times before the first call finishes, each caller will see `cache === null` and initiate its own network request.\n\n### Interleaving that triggers the bug\nConsider two concurrent calls, `A` and `B`:\n\n1. **Call A** checks `if (cache)` → `cache` is `null`, so it proceeds.\n2. **Call A** reaches `await fetch('/config')` and suspends.\n3. **Call B** checks `if (cache)` → `cache` is still `null` (A hasn’t set it yet), so it also proceeds.\n4. **Call B** starts its own `fetch('/config')`.\n5. Both requests complete; each parses the JSON and writes to `cache`. The last write “wins,” but two network requests were made unnecessarily, and if the server returned different data, the final cached value might be inconsistent.\n\n### Fix\nStore the **promise** of the in-flight operation, not just the final result. When a second caller arrives while a fetch is ongoing, it should await that same promise instead of starting a new request.\n\n```javascript\nlet cachePromise = null;\n\nasync function getConfig() {\n  if (!cachePromise) {\n    cachePromise = fetch('/config').then(r => r.json());\n  }\n  return cachePromise;\n}\n```\n\nNow the first call creates the promise and all subsequent calls (even concurrent ones) will wait for that single promise. Once it resolves, `cachePromise` holds the resolved value (a promise retains its result), so future calls will immediately return the cached config without any network request. This eliminates the race condition and prevents duplicate fetches.",
      "latency_ms": 15720,
      "cost": 0.000640520767,
      "task_score": 9,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Correctly identifies race condition, explains interleaving clearly, provides accurate fix using promise caching. Minor: could mention error handling reset, but otherwise strong and clear."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response perfectly identifies the race condition, clearly explains the exact interleaving that causes it, and provides an elegant, idiomatic fix by caching the promise."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 9,
          "violates": false,
          "reasoning": "Correctly identifies concurrent cache misses, gives a valid interleaving, and fixes duplicate requests by caching the in-flight promise. Clear and practical. Minor omission: a rejected fetch leaves a permanently rejected cached promise, so "
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c11",
      "name": "Retry with backoff",
      "prompt": "Write an async retry wrapper in TypeScript: exponential backoff with jitter, a maximum attempt count, and it must NOT retry on 4xx responses other than 429. Maximum 30 lines. State what happens on the final failure.",
      "output": "```typescript\nconst retry = async <T>(\n  fn: () => Promise<T>,\n  { maxAttempts = 3, baseDelayMs = 1000, maxDelayMs = 30000, jitter = 0.1 }: {\n    maxAttempts?: number; baseDelayMs?: number; maxDelayMs?: number; jitter?: number;\n  } = {}\n): Promise<T> => {\n  for (let attempt = 0; attempt < maxAttempts; attempt++) {\n    try {\n      return await fn();\n    } catch (error) {\n      if (attempt === maxAttempts - 1) throw error;\n      if (error && typeof error === 'object' && 'status' in error) {\n        const status = (error as any).status;\n        if (typeof status === 'number' && status >= 400 && status < 500 && status !== 429) throw error;\n      }\n      const delay = Math.min(maxDelayMs, baseDelayMs * Math.pow(2, attempt));\n      await new Promise(r => setTimeout(r, delay * (1 - jitter + Math.random() * jitter * 2)));\n    }\n  }\n  throw new Error('Unreachable');\n};\n```\n\n**On final failure:** The error from the last attempt is thrown (no further retries). If that error carries a 4xx status (except 429), it will have been thrown immediately on that attempt without retrying.",
      "latency_ms": 27445,
      "cost": 0.007846056,
      "task_score": 9,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 8,
          "violates": false,
          "reasoning": "Correct exponential backoff with jitter, respects 4xx exclusion except 429, within 30 lines, explains final failure clearly. Minor: unreachable throw slightly awkward but harmless."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response perfectly fulfills all requirements, including exponential backoff, jitter, max attempts, and the specific 4xx logic. It stays under the 30-line limit and clearly states the final failure behavior."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 9,
          "violates": false,
          "reasoning": "Correct async retry logic with capped exponential backoff, symmetric jitter, and proper exclusion of non-429 4xx errors. It clearly states final-failure behavior and stays within 30 lines. Minor edge case: maxAttempts <= 0 yields an unrelat"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c12",
      "name": "Recursive type",
      "prompt": "Write a TypeScript type DeepPartial<T> that makes every nested property optional, and explain in one sentence how it must handle arrays differently from plain objects.",
      "output": "```typescript\ntype DeepPartial<T> = T extends object\n  ? T extends any[]\n    ? T\n    : { [K in keyof T]?: DeepPartial<T[K]> }\n  : T;\n```\n\n**One‑sentence explanation:**  \nIt must treat arrays as a special case and return them unchanged, because applying a mapped type with optional properties would destroy their array nature, turning them into index‑signature objects instead of preserving their built‑in methods and numeric indexing.",
      "latency_ms": 12918,
      "cost": 0.0007783464,
      "task_score": 5,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 7,
          "violates": false,
          "reasoning": "Correct, concise, and explains array handling, though ideally arrays should map DeepPartial over elements rather than leave unchanged."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 5,
          "violates": false,
          "reasoning": "Fails to make nested properties inside arrays optional. The explanation relies on outdated TypeScript behavior (pre-3.1); modern TS preserves array types when mapping, so arrays don't need to be skipped to avoid becoming plain objects."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 3,
          "violates": false,
          "reasoning": "It fails to deep-partialize objects contained in arrays, so not every nested property becomes optional. The explanation is also inaccurate: mapped types generally preserve array structure; arrays should typically recurse on their element ty"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c13",
      "name": "Bash one-liner",
      "prompt": "Give me a single shell command that finds the ten largest files under the current directory recursively and prints them human-readable, largest first. It must handle filenames containing spaces. Explain each part briefly.",
      "output": "```sh\nfind . -type f -exec du -h {} + | sort -hr | head -n 10\n```\n\nExplanation:\n\n- `find . -type f` — recursively finds all regular files under the current directory.\n- `-exec du -h {} +` — runs `du -h` on the found files, passing many filenames as separate arguments. This is safe for spaces because the shell never re-parses the names.\n- `du -h` — prints each file’s disk usage in a human-readable format like `12M`, `4.0K`.\n- `sort -hr` — sorts the output by human-readable size, largest first.\n- `head -n 10` — prints only the top ten results.",
      "latency_ms": 50106,
      "cost": 0.0030218516925,
      "task_score": 9,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Command is correct, handles spaces via -exec +, sorts human-readable sizes, and explanation is clear and accurate. Minor edge case: multiple du invocations for huge file counts, but still correct."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response provides a flawless, robust shell command that perfectly meets all requirements, including handling spaces and sorting human-readable sizes. The explanations are clear, concise, and accurate."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 8,
          "violates": false,
          "reasoning": "Correctly finds regular files recursively, handles spaces, sorts human-readable disk usage descending, and limits output to ten. Minor caveats: it measures disk usage rather than apparent file size, depends on GNU-style human-readable sorti"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c14",
      "name": "Explain and cost",
      "prompt": "Explain what this does and give its time and space complexity, then rewrite it to be O(n).\n\ndef has_dup(xs):\n    for i in range(len(xs)):\n        for j in range(i+1, len(xs)):\n            if xs[i] == xs[j]:\n                return True\n    return False",
      "output": "The function `has_dup(xs)` checks whether a list `xs` contains any duplicate elements. It does this by comparing every element with all later elements using two nested loops. If it finds two equal elements, it returns `True`; otherwise, after checking all pairs, it returns `False`.\n\n**Time complexity:** O(n²) – for a list of length n, the inner loop runs roughly n²/2 comparisons in the worst case.  \n**Space complexity:** O(1) – only a few variables are used, no extra data structures.\n\nTo achieve O(n) time, we can trade space for time by using a set to remember elements we’ve already seen. As we iterate through the list once, we check if the current element is already in the set; if so, we have a duplicate. Otherwise, we add it to the set and continue.\n\nHere’s the O(n) version:\n\n```python\ndef has_dup(xs):\n    seen = set()\n    for x in xs:\n        if x in seen:\n            return True\n        seen.add(x)\n    return False\n```\n\n**Time complexity:** O(n) – each element is processed once, and set lookups/insertions are O(1) on average.  \n**Space complexity:** O(n) – in the worst case (no duplicates), the set stores all n elements.",
      "latency_ms": 7955,
      "cost": 0.0003945457105,
      "task_score": 9,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Accurate explanation, correct complexities, correct O(n) rewrite with set, clear and concise."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response perfectly explains the function, correctly identifies the time and space complexity, and provides an accurate O(n) rewrite using a set. It is clear, concise, and highly useful."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 9,
          "violates": false,
          "reasoning": "Accurately explains pairwise duplicate checking, worst-case O(n²) time and O(1) extra space, then provides the standard expected-O(n) set-based rewrite with O(n) space. Minor caveat: the rewrite requires hashable elements."
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c15",
      "name": "Regex with limits",
      "prompt": "Write a regex that validates UK postcodes, give a one-line explanation of each part, and then state two valid UK postcodes your regex would reject or two invalid ones it would accept. Do not claim it is perfect.",
      "output": "**Regex**  \n`^([A-Z]{1,2}[0-9][A-Z0-9]?|[A-Z][0-9]{1,2}) [0-9][A-Z]{2}$`\n\n**Explanation of each part**  \n- `^` – match the start of the string.  \n- `( ... | ... )` – a group that matches the outward code in two possible formats.  \n- `[A-Z]{1,2}` – one or two uppercase letters (the postcode area).  \n- `[0-9]` – a single digit (first part of the district).  \n- `[A-Z0-9]?` – an optional letter or digit (second part of the district, allowing formats like `AA9A`).  \n- `|` – alternation to the other outward‑code pattern.  \n- `[A-Z]` – a single uppercase letter (area).  \n- `[0-9]{1,2}` – one or two digits (district).  \n- ` ` – a literal space separating outward and inward codes.  \n- `[0-9]` – a single digit (inward code sector).  \n- `[A-Z]{2}` – two uppercase letters (inward code unit).  \n- `$` – match the end of the string.\n\n**Imperfections**  \nThis regex is deliberately simplified and **not perfect**. For instance, it would **reject** these two valid UK postcodes:  \n- `W1A 1AA` (the single‑letter area plus `digit + letter` outward format `A9A` is not supported)  \n- `GIR 0AA` (the special Girobank code is not handled)\n\nIt would also **accept** these two invalid postcodes:  \n- `Q1 1AA` (uses `Q`, which is never a valid first area letter)  \n- `AA1 1CV` (contains `V` in the inward code; inward code letters exclude `C, I, K, M, O, V`)",
      "latency_ms": 63447,
      "cost": 0.0040726296,
      "task_score": 8,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 8,
          "violates": false,
          "reasoning": "Accurate regex, clear explanations, correctly identifies limitations without claiming perfection; minor technical nitpicks but overall well-executed and useful."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 8,
          "violates": false,
          "reasoning": "Follows all instructions, but contains a factual error: the regex provided actually *would* accept 'W1A 1AA', contradicting the claim that it rejects it. Otherwise, excellent and clear."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 6,
          "violates": false,
          "reasoning": "The regex and component explanations are broadly useful, and it correctly gives two invalid postcodes it would accept. However, it falsely claims `W1A 1AA` would be rejected; the first alternative accepts it. This is a notable factual error"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c16",
      "name": "Callback to async",
      "prompt": "Refactor this to async/await with correct error propagation. Errors must not be swallowed.\n\ngetUser(id, (e, user) => {\n  if (e) return cb(e);\n  getOrders(user.id, (e2, orders) => {\n    if (e2) return cb(e2);\n    getTotals(orders, (e3, totals) => cb(e3, totals));\n  });\n});",
      "output": "```js\nconst { promisify } = require('util');\n\nconst getUserAsync = promisify(getUser);\nconst getOrdersAsync = promisify(getOrders);\nconst getTotalsAsync = promisify(getTotals);\n\nasync function getUserTotals(id) {\n  const user = await getUserAsync(id);\n  const orders = await getOrdersAsync(user.id);\n  const totals = await getTotalsAsync(orders);\n  return totals;\n}\n```\n\nIf you must keep the callback API:\n\n```js\nasync function getUserTotals(id, cb) {\n  try {\n    const user = await getUserAsync(id);\n    const orders = await getOrdersAsync(user.id);\n    const totals = await getTotalsAsync(orders);\n    cb(null, totals);\n  } catch (err) {\n    cb(err);\n  }\n}\n```\n\nKey points:\n\n- Errors propagate automatically through rejected promises in `async/await`.\n- Do not swallow errors in an empty `catch`.\n- If `getUser`, `getOrders`, and `getTotals` already return promises, you can drop `promisify` and call them directly.",
      "latency_ms": 33376,
      "cost": 0.002324012817,
      "task_score": 9,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 9,
          "violates": false,
          "reasoning": "Correct, clear async/await refactor with proper error propagation, covers both promise-based and callback-compatible versions, concise and useful."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response perfectly refactors the code to async/await, handles error propagation correctly (both returning a promise and keeping the callback), and provides clear, concise explanations."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 8,
          "violates": false,
          "reasoning": "Correctly promisifies Node-style callbacks and uses sequential awaits so rejections propagate. The callback wrapper forwards errors, but making it async can produce an ignored rejected promise if cb throws; otherwise it fully meets the task"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c17",
      "name": "Diagnose from a trace",
      "prompt": "Given this Node stack trace, state the most likely root cause and the first thing you would check:\n\nTypeError: Cannot read properties of undefined (reading 'map')\n    at renderRows (/app/src/table.js:42:19)\n    at Table (/app/src/table.js:12:5)\n    at renderWithHooks (/app/node_modules/react-dom/cjs/react-dom.development.js:16305:18)\n\nThe component works in dev and fails only on the production build's first paint.",
      "output": "Most likely root cause: `renderRows` is trying to call `.map()` on `undefined`. The collection it expects — usually a prop like `props.rows` or `props.items`, or something from an API response — hasn’t been initialized or hasn’t loaded before the first render.\n\nThe first thing I’d check is `src/table.js:42`:\n\n```js\n// something like\nrows.map(...)\n// or\ndata.items.map(...)\n```\n\nThen trace where that value comes from. In most cases it’s either:\n\n- a parent passing `rows={undefined}` because its state starts empty, or\n- an API/SSR data fetch hasn’t resolved before first paint, or\n- the value comes from client-only data like `localStorage`/`window` and isn’t available during server rendering.\n\nFix it by defaulting to an array or guarding the render:\n\n```js\nfunction renderRows(rows = []) {\n  return rows.map(...)\n}\n```\n\nor:\n\n```js\n{(rows ?? []).map(row => ...)}\n```\n\nAlso verify that the production data source/API is actually returning the expected shape, not `undefined`.",
      "latency_ms": 44868,
      "cost": 0.003696021,
      "task_score": 9,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 8,
          "violates": false,
          "reasoning": "Accurate, actionable root cause and fix, addresses dev/prod difference briefly via SSR/timing; clear and concise, minor lack of deeper focus on prod-specific cause."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response accurately identifies the root cause and the first step to check. It is highly useful, clear, and concise, perfectly addressing the scenario described."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 9,
          "violates": false,
          "reasoning": "Correctly identifies an undefined collection being mapped and appropriately prioritizes inspecting table.js line 42 and its data flow. Production-first-paint causes are plausible. Slightly more expansive than necessary, but clear and useful"
        }
      ],
      "machine_checks": null,
      "machine_violation": false,
      "machine_reasons": []
    },
    {
      "id": "c18",
      "name": "Idempotency",
      "prompt": "Design an idempotent POST /payments endpoint so a client retry cannot charge twice. Describe the key, where it is stored, what happens on a concurrent duplicate, and what you return the second time. Maximum 200 words. Name the failure mode your design still has.",
      "output": "Require the client to send an `Idempotency-Key` header. Store it in an `idempotency_keys` table with a unique constraint, including request hash, state (`processing` or `completed`), response status/body, and timestamps.\n\nFirst request inserts a `processing` row, calls the payment provider, then updates the row to `completed` with the provider result. On a concurrent duplicate, one insert wins; the other hits the unique constraint, fetches the row, and sees `processing`. Return `409 Conflict` with `Retry-After`; if already `completed`, return the stored response. On the second call after completion, return the stored response body and status — no second charge.\n\nFailure mode: a crash after the provider charges but before persisting `completed` can leave the key `processing` or absent, so a retry may double charge without reconciliation.",
      "latency_ms": 14804,
      "cost": 0.000788826825,
      "task_score": 8,
      "judges": [
        {
          "judge": "anthropic/claude-sonnet-5",
          "score": 7,
          "violates": false,
          "reasoning": "Clear, mostly correct idempotency design with key storage, concurrency handling, and named failure mode; concise under 200 words. Minor detail gaps (request hash mismatch handling) but solid overall."
        },
        {
          "judge": "google/gemini-3.1-pro-preview",
          "score": 10,
          "violates": false,
          "reasoning": "The response perfectly answers all parts of the prompt within the word limit. It accurately describes a standard and robust idempotency design and correctly identifies a valid edge-case failure mode."
        },
        {
          "judge": "openai/gpt-5.6-terra",
          "score": 8,
          "violates": false,
          "reasoning": "Covers key, durable unique storage, concurrent handling, replayed completed response, and a real crash/atomicity failure mode. Minor caveat: a persisted processing row normally causes 409 rather than an immediate double charge; duplication "
        }
      ],
      "machine_checks": {
        "max_words": 200
      },
      "machine_violation": false,
      "machine_reasons": []
    }
  ],
  "recapped_at": "2026-08-16T08:16:35.201Z",
  "recap_note": "Machine constraint caps applied retroactively under protocol judge-2026-08b; judge verdicts unchanged, task scores capped where a deterministic check failed."
}