Claude Opus 5.5 (effort default (no --effort flag) · thinking on) on Trace a desktop app's Export feature from its packaged bytecode, with no source code

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

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.32
Wall time: 22s
Human step-ins: 0
Outcome: Pass

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Exact prompt

# Trace how one feature of a desktop app works, from its packaged files only The `*.pyz` file in this folder is a small desktop app, built only for this test, shipped the way it would reach a user: a zipped Python application containing compiled bytecode (`.pyc`) and no source code. It runs on the Python 3.13 installed here. `data/project.json` is a project the user has open, and `settings.ini` is their settings file. You may unpack, disassemble, import and run the app's code however you like, but don't modify the `.pyz`. There is no display, so the window itself won't open. Trace what happens when the user picks File > Export... in the app's window and write `out/trace.json`: - `call_chain`: List the call chain from the menu handler behind File > Export... down to the function that calls `open()` to write the export. Use qualified names, `<package>.<module>.<Class>.<method>` for methods and `<package>.<module>.<function>` for plain functions, in call order, starting with the handler; each entry calls the next. - `output_path`: Give the full path of the finished export file (after any temporary file is renamed) for this project and settings when the user's home directory is `/home/user` and today is 2026-10-21. - `delimiter` and `header`: Give the field delimiter and the header labels in order. `header` is a list of strings. Write `out/predicted_export.txt` with exactly the bytes the export would write for this project and these settings on 2026-10-21 (same line endings, no extra trailing newline). ## 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.

A small desktop app built only for this test ships as a zipped bytecode bundle with no source. Starting from the File > Export... menu entry, the solver must name the real call chain down to the file write, the final output path, the delimiter and header, and predict the exported bytes. A hidden legacy exporter, a settings file that overrides the defaults, filtered records and a delimiter inside a field separate a real trace from a guess. 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: call_chain output_path format predicted_export

Setup notes: Batch 21 case w01-trace-export-from-packaged-app (offline, synthetic inputs, seed 3255912926). 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 0.63 (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-opus-5.5: $0.317225. Score: 4/4. 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: $0.32
Wall time: 22s
Human step-ins: 0
Turns: 5

Model usage
Model	Input tok	Output tok	Cost
AClaude Opus 5.5anthropic/claude-opus-5.5effort default (no --effort flag) · thinking on	143,659	2,121	$0.32

Reproduce this run

Use the use case prompt on the use case page.
Same setup: Claude Opus 5.5 (anthropic/claude-opus-5.5, effort default (no --effort flag) · thinking on) via Claude Code 2.1.299 (headless -p), cloud.
It counts as a success only if it meets every success criterion: call_chain output_path format predicted_export
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

[
 {
  "duration_api_ms": 21133,
  "stop_reason": "end_turn",
  "session_id": "[REDACTED]",
  "total_cost_usd": 0.31722520000000004,
  "usage": {
   "input_tokens": 10,
   "cache_creation_input_tokens": 31543,
   "cache_read_input_tokens": 112106,
   "output_tokens": 2121,
   "output_tokens_details": {
    "thinking_tokens": 197
   },
   "server_tool_use": {
    "web_search_requests": 0,
    "web_fetch_requests": 0
   },
   "service_tier": "standard",
   "cache_creation": {
    "ephemeral_1h_input_tokens": 31543,
    "ephemeral_5m_input_tokens": 0
   },
   "inference_geo": "global",
   "iterations": [
    {
     "input_tokens": 2,
     "output_tokens": 791,
     "cache_read_input_tokens": 42248,
     "cache_creation_input_tokens": 1441,
     "cache_creation": {
      "ephemeral_5m_input_tokens": 0,
      "ephemeral_1h_input_tokens": 1441
     },
     "type": "message"
    }
   ],
   "speed": "standard",
   "fallback_credit": null
  },
  "modelUsage": {
   "claude-opus-5-5": {
    "inputTokens": 10,
    "outputTokens": 2121,
    "cacheReadInputTokens": 112106,
    "cacheCreationInputTokens": 31543,
    "webSearchRequests": 0,
    "costUSD": 0.31722520000000004,
    "contextWindow": 1000000,
    "maxOutputTokens": 128000,
    "thinkingTokens": 197,
    "canonicalModel": "claude-opus-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,
    "foreground": 0,
    "unset": 0
   },
   "started_in_background": 0,
   "max_depth": 0,
   "spawned_by_subagents": 0,
   "completed": 0,
   "failed": 0,
   "killed": {
    "parent": 0,
    "user": 0,
    "system": 0
   },
   "refused": {
    "depth_limit": 0,
    "concurrency_limit": 0,
    "budget": 0
   },
   "by_type": {}
  },
  "safety_stops": 0,
  "is_error": false,
  "num_turns": 5,
  "subtype": "success",
  "api_error_status": null,
  "result": "I've written `out/trace.json` and `out/predicted_export.txt`. I read the app's disassembled bytecode to find the path, then ran the app's own export functions on your project and settings with the date set to 2026-10-21 and the home directory set to `/home/user`. Nothing was written outside `out/`, and the `.pyz` is unchanged.\n\n**Call chain** (File > Export... is connected to `handle_export` in `MainWindow.build`):\n1. `tallybook.gui.MainWindow.handle_export`\n2. `tallybook.exporter.ExportJob.execute`\n3. `tallybook.exporter.ExportJob._write`\n4. `tallybook.diskio.write_atomically`, which opens `<path>.part`, writes the text, then renames it to the final path.\n\n**Output path:** `/home/user/Tallybook/exports/spring-fair-export-2026-10-21.dat`. The folder `~/Tallybook/exports` and the `.dat` extension come from the app's built-in defaults; the date in the filename is today's date in `%Y-%m-%d` form.\n\n**Delimiter and header:** `;`, with the header `Ref, Day, Description, Client, Amount`. Your `settings.ini` only sets `date_format` and `legacy_menu`, so everything else uses the defaults. Those defaults cover the columns and their order (description comes before client) and skipping `draft` rows.\n\n**Export content:**\n- **Rows:** the 8 non-draft records, sorted by date and then id.\n- **Line endings:** CRLF, including after the last line.\n- **Dates:** written as `%m-%d-%Y`.\n- **Amounts:** shown as decimals, e.g. `-4028.30`.\n- **Delimiter inside text:** a `;` inside a field becomes `_`, so `Site visit ; extra` becomes `Site visit _ extra`.\n\nTwo other things in the app don't affect this export. The \"Export (legacy)\" item, which writes a CSV through `export_v1`, only appears when `legacy_menu = yes`, and yours is `no`. The `APP_TODAY` setting I used to fix the date is something the app's clock reads itself, so I didn't need to patch anything.",
  "ttft_ms": 2831,
  "type": "result",
  "duration_ms": 21570,
  "uuid": "[REDACTED]",
  "ttft_stream_ms": 1462,
  "time_to_request_ms": 268,
  "first_content_frame_ms": 1462,
  "queued_turn_count": 0,
  "result_index": 0
 }
]