Claude Sonnet 5.5 (effort default (no --effort flag) · thinking off) on Recommend a vendor on three-year total cost when the cheapest first month is the wrong choice

AClaude Sonnet 5.5default · thinking off · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-21 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.05
Wall time: 11s
Human step-ins: 0
Outcome: Pass

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Exact prompt

# Recommend a vendor on three-year total cost Inputs: `offers.json` (each vendor's setup fee, monthly base fee, tiered per-unit prices, tier type and annual escalator), `forecast.json` (monthly volume for the next 36 months) and `status-quo.json` (what we pay today per month, fixed). Rules: - Tier type "all_units": every unit in the month is charged at the price of the tier the month's total volume falls in. "incremental": each unit is charged at the price of the tier it falls in (like tax brackets). A tier's `up_to` is inclusive; null means no upper limit. - The escalator raises the base fee and every unit price by that percentage at the start of month 13 and again at the start of month 25 (compounding). - Monthly cost = base fee + unit charges, rounded half-up to the cent each month. The setup fee is paid in month 1 on top of the monthly cost. - TCO = sum of the 36 monthly costs plus the setup fee. - recommended = the vendor with the lowest TCO. cheapest_first_month = the vendor with the lowest month-1 cost excluding the setup fee. - breakeven_month = the first month in which cumulative savings of the recommended vendor against the status quo (status-quo cost minus vendor cost, including setup in month 1) reach 0 or more; null if never within 36 months. - claims: `first_month_price_misleads` = true when cheapest_first_month is not recommended; `saves_vs_status_quo` = true when the recommended vendor's TCO is below 36 x the status-quo monthly cost. Write `out/memo.json`: `{"tco": {"<vendor>": <usd>, ...}, "recommended": "<vendor>", "cheapest_first_month": "<vendor>", "breakeven_month": <int|null>, "claims": {"first_month_price_misleads": <bool>, "saves_vs_status_quo": <bool>}}`. ## How this run works - Work on your own: nobody will answer questions in this task, and writing to `ask/` counts against the run. - Write only under `out/`. Create `out/` if it is missing. Inputs are synthetic; don't fetch anything from the network. - Scoring is partial credit: each listed check is pass/fail, and the score is the share passed. Numbers are compared to within 0.005 unless the task says otherwise.

Compare four offers over 36 months of growing volume. Offers mix all-units and incremental tier pricing, setup fees and compounding annual escalators. Report each vendor's total cost, the recommendation, the break-even month against the current supplier, and two derived claims. Every seed is drawn so the cheapest first month is not the cheapest over three years, and the top two totals are at least $200 apart, and the lowest headline unit price is not the winner either. 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). Folder-restore note: this run's output files under work/out/ were lost in a 1:22 AM ET restore on Oct 21, 2026. The trace, step-in exchanges and output-hash list were checked against the recorded SHA-256 values and match; the hashes of the individual output files inside that list can no longer be recomputed. Measured data unchanged.

Success criteria: tco_per_vendor incremental_tiers recommended cheapest_first_month breakeven claims

Setup notes: Batch 18 case t04-vendor-tco-memo (offline, synthetic inputs, seed 934918685). Autonomous case: no stand-in user and no step-ins expected; any file the solver wrote to ask/ is counted as a measured intervention (0) and blocks a pass. Prompt = TASK.md verbatim. Hidden key kept outside the solver's work dir. Scored with the case's scorer (python3 score.py WORKDIR KEYDIR, absolute paths); pass = every check true and no ask/ files. Tools: Read/Write/Edit/Glob/Grep/Bash, web disabled. Single run, no retries. 1-min load average at scoring 0.13 (8 cores). Time-zone results depend on the system time-zone database: tzdata 2026c-0+deb13u1 (Python zoneinfo). Claude Code's own reported cost for claude-sonnet-5.5: $0.050888. Score: 6/6. Cost is an ESTIMATE: measured tokens x pricing.json list price (Claude Pro subscription, nothing billed); input_tokens include cache reads and writes. Single run.

Estimated cost List-price estimate; not actually billed.

Metrics

Estimated cost: $0.05
Wall time: 11s
Human step-ins: 0
Turns: 3

Model usage
Model	Input tok	Output tok	Cost
AClaude Sonnet 5.5anthropic/claude-sonnet-5.5effort default (no --effort flag) · thinking off	59,132	1,296	$0.05

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 off) via Claude Code 2.1.299 (headless -p), cloud.
It counts as a success only if it meets every success criterion: tco_per_vendor incremental_tiers recommended cheapest_first_month breakeven claims
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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     "cache_creation": {
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      "ephemeral_1h_input_tokens": 1002
     },
     "type": "message"
    }
   ],
   "speed": "standard",
   "fallback_credit": null
  },
  "modelUsage": {
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    "inputTokens": 6,
    "outputTokens": 1296,
    "cacheReadInputTokens": 50920,
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    "webSearchRequests": 0,
    "costUSD": 0.050888,
    "contextWindow": 1000000,
    "maxOutputTokens": 128000,
    "thinkingTokens": 0,
    "canonicalModel": "claude-sonnet-5-5",
    "provider": "firstParty",
    "costBasis": "list"
   }
  },
  "permission_denials": [],
  "terminal_reason": "completed",
  "fast_mode_state": "off",
  "fast_mode_disabled_reason": "sdk_opt_in_required",
  "subagent_stats": {
   "spawned": 0,
   "requested": {
    "background": 0,
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   },
   "started_in_background": 0,
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   "killed": {
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   "by_type": {}
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  "safety_stops": 0,
  "is_error": false,
  "num_turns": 3,
  "subtype": "success",
  "api_error_status": null,
  "result": "I recommend Bluepeak. Its three-year TCO is $529,500.47, the lowest of the four vendors, and I wrote the memo to `out/memo.json`.\n\n| Vendor | 3-year TCO |\n|---|---|\n| Bluepeak | $529,500.47 |\n| Quillon | $530,698.72 |\n| Tessaly | $546,112.23 |\n| Corvana | $758,124.94 |\n\n- **Cheapest first month:** Tessaly has the lowest month-1 cost, so `first_month_price_misleads` is true.\n- **Against the status quo:** Bluepeak's TCO is well below 36 \u00d7 $15,575.91, so `saves_vs_status_quo` is true.\n- **Breakeven:** month 1. Bluepeak has no setup fee and its month-1 cost is below the $15,575.91 status-quo cost, so cumulative savings are positive from the start.\n\nI used exact decimal arithmetic with half-up rounding to the cent each month, so there is no floating-point drift in the totals. I did not independently check the figures beyond that single run.",
  "ttft_ms": 1887,
  "type": "result",
  "duration_ms": 10660,
  "uuid": "[REDACTED]",
  "ttft_stream_ms": 1112,
  "time_to_request_ms": 259,
  "first_content_frame_ms": 1112,
  "queued_turn_count": 0,
  "result_index": 0
 }
]