Claude Sonnet 5.5 (effort default (no --effort flag) · thinking on) on Write an atomic, idempotent SQLite v1→v2 migration with dedupe, FK and CHECK constraints

AClaude Sonnet 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-16 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.09
Wall time: 32s
Human step-ins: 0
Outcome: Pass

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Exact prompt

# Task: write a safe schema migration (SQLite) `app.db` is at schema v1: `users(id, full_name, email, created 'DD/MM/YYYY')`, `orders(id, user_email, total_cents, status)`. Write `migrate.py` (stdlib sqlite3) that upgrades `app.db` IN PLACE to v2: - `users(id INTEGER PRIMARY KEY, first_name TEXT NOT NULL, last_name TEXT NOT NULL, email TEXT NOT NULL UNIQUE, created_at TEXT NOT NULL)` — trim names; first_name = first word, last_name = the rest ("Chloé de Vries" → "Chloé", "de Vries"); email lowercased+trimmed; created_at ISO `YYYY-MM-DD`. - Users whose emails differ only by case/whitespace are duplicates: keep the LOWEST id, delete the others, and re-point their orders. - `orders(id INTEGER PRIMARY KEY, user_id INTEGER NOT NULL REFERENCES users(id), total_cents INTEGER NOT NULL, status TEXT NOT NULL CHECK(status IN ('paid','refunded','pending')))` — user_id resolved via email (case-insensitive); status normalised (trim + lowercase). - Table `schema_version(version INTEGER)` containing exactly one row `2`. - Must be atomic (all-or-nothing in one transaction) and idempotent: running `python migrate.py` again on a v2 database must change nothing and exit 0. Keep order ids and kept user ids unchanged. Run it once so `app.db` is migrated. No network.

Scorer re-runs migrate.py twice on a fresh v1 db (dump hash must not change), checks exact schema, constraints, merged duplicate users and re-pointed orders. 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. Scorer builds a fresh v1 database, runs migrate.py twice: both runs exit 0 and the database dump is identical after run 1 and run 2 (idempotent). 2. users schema exactly: id INTEGER, first_name TEXT NOT NULL, last_name TEXT NOT NULL, email TEXT NOT NULL, created_at TEXT NOT NULL (in that order); orders columns id, user_id, total_cents, status with the stated types; orders has a foreign key to users. 3. CHECK constraint rejects an invalid status; UNIQUE constraint rejects a duplicate email. 4. schema_version contains exactly one row with value 2. 5. User and order counts match the key (duplicates merged); orders per user and total cents per user match exactly (orders re-pointed to the kept lowest id); status counts after normalisation match. 6. Every kept user row (names split, email lowercased, ISO date) matches exactly. 7. The agent's own migrated app.db must also pass all the data/schema checks.

Setup notes: Use Case Scout batch 4 case d04-sqlite-schema-migration (offline fixture). Prepared with batch4/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/key.json`. Tools: Read/Write/Edit/Glob/Grep/Bash, web disabled. Single run, no retries. Claude Code's own reported cost for claude-sonnet-5.5: $0.090531. Score: 13/13 checks. 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: $0.09
Wall time: 32s
Human step-ins: 0
Turns: 4

Model usage
Model	Input tok	Output tok	Cost
AClaude Sonnet 5.5anthropic/claude-sonnet-5.5effort default (no --effort flag) · thinking on	85,765	3,377	$0.09

Reproduce this run

Use the use case prompt on the use case page.
Same setup: Claude Sonnet 5.5 (anthropic/claude-sonnet-5.5, effort default (no --effort flag) · thinking on) via Claude Code 2.1.299 (headless -p), cloud.
It counts as a success only if it meets every success criterion: 1. Scorer builds a fresh v1 database, runs migrate.py twice: both runs exit 0 and the database dump is identical after run 1 and run 2 (idempotent). 2. users schema exactly: id INTEGER, first_name TEXT NOT NULL, last_name TEXT NOT NULL, email TEXT NOT NULL, created_at TEXT NOT NULL (in that order); orders columns id, user_id, total_cents, status with the stated types; orders has a foreign key to users. 3. CHECK constraint rejects an invalid status; UNIQUE constraint rejects a duplicate email. 4. schema_version contains exactly one row with value 2. 5. User and order counts match the key (duplicates merged); orders per user and total cents per user match exactly (orders re-pointed to the kept lowest id); status counts after normalisation match. 6. Every kept user row (names split, email lowercased, ISO date) matches exactly. 7. The agent's own migrated app.db must also pass all the data/schema checks.
Log model, tokens, wall time, human step-ins and the evidence log, then submit it as a reproduction. A different model? Submit a head-to-head rerun.

How runs are scored: Methodology.

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Automated checks

Trust 80% comes from these checks (how Trust % works).

Run date is not in the future : passed
Model is in the dated pricing table : passed
Cost recomputed from tokens matches : passed
Cached tokens are consistent : passed
Output throughput is plausible : passed
Autonomy matches step-ins : passed
Step-ins do not exceed turns : passed
Retries agree with first-try result : passed
Evidence log SHA-256 matches : passed
Evidence log is substantial : passed

Evidence log

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  "result": "I wrote `migrate.py` and ran it once, so `app.db` is now at schema v2. A second run printed \"already at v2; nothing to do\", exited 0, and left the file's checksum unchanged.\n\n- **Users:** 200 became 170. 30 duplicate rows were removed, and the lowest id of each duplicate group was kept. Names are trimmed and split, for example \"  Eva de Vries \" became `Eva` / `de Vries`. Emails are lowercased and trimmed. Dates are now ISO.\n- **Orders:** All 1000 are kept with their original ids and totals. Each one now points at the kept user for its email. Statuses are normalised to `paid`, `pending` or `refunded`.\n- **Checks:** After migrating, `PRAGMA foreign_key_check` reported no violations and `integrity_check` returned ok.\n- **Atomicity:** The whole migration runs in one transaction. Any failure, such as a bad date or an order whose email has no user, rolls back and exits 1 with the database untouched.\n- **Idempotency:** The script checks `schema_version` first and exits 0 without writing if it already says 2.\n\n- **Kept row wins:** When emails are duplicated, the name and `created_at` come from the kept (lowest-id) row. The other rows' values are discarded.\n- **Single-word names:** A name with no space gets an empty `last_name`, because the column is NOT NULL. None of the current data hits this.\n- **Backup:** I copied the original to `/tmp/app.bak` before running, if you want to compare or roll back.",
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