Claude Sonnet 5.5 on Fix three bugs in a Python repo so its tests pass

AClaude Sonnet 5.5 · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-14 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.04
Wall time: 8s
Human step-ins: 0
Outcome: Pass

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Exact prompt

You are working on the repository in ./repo. Fix the three bugs described in repo/ISSUES.md in textstats.py. Run the existing tests (python3 -m unittest in repo) and make sure they pass. Do not change function names or signatures.

Task prompt given to the agent (headless, offline, synthetic fixture inputs): You are working on the repository in ./repo. Fix the three bugs described in repo/ISSUES.md in textstats.py. Run the existing tests (python3 -m unittest in repo) and make sure they pass. Do not change function names or signatures. Inspired by https://x.com/bnjmn_marie/status/2089775546943312076 (unverified; not checked with the author). This is an independent re-run on a reproducible synthetic task; it does not report or reproduce the original post's numbers. Cost shown is a list-price API-equivalent estimate (run on a Claude Pro subscription, not billed).

Success criteria: All automated rubric checks pass: hidden test test_avg; hidden test test_mc; hidden test test_wc.

Setup notes: Cost is an ESTIMATE: Claude Code's list-price API-equivalent figure. The run used a Claude Pro subscription, so nothing was billed. input_tokens = all input incl. cache-creation and cache-read tokens; cached_tokens = cache reads (subset of input). Claude Code's cost bills cache writes at the 1h cache-write premium, so it can differ from a flat input-price recompute. Web disabled; tools Read/Write/Edit/Glob/Grep/Bash; single run; scored automatically (3/3 checks).

Estimated cost List-price estimate; not actually billed.

Metrics

Estimated cost: $0.04
Wall time: 8s
Human step-ins: 0
Turns: 3

Model usage
Model	Input tok	Output tok	Cost
AClaude Sonnet 5.5anthropic/claude-sonnet-5.5	55,053	591	$0.04

Reproduce this run

Use the use case prompt on the use case page.
Same setup: Claude Sonnet 5.5 (anthropic/claude-sonnet-5.5) via Claude Code 2.1.299 (headless -p), cloud.
It counts as a success only if it meets every success criterion: All automated rubric checks pass: hidden test test_avg; hidden test test_mc; hidden test test_wc.
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 fixed all three bugs in `textstats.py`, and the 3 existing tests pass. I kept the function names and signatures as they were.\n\n1. **`word_count`:** It now splits on any run of whitespace, so repeated spaces, newlines and tabs no longer inflate the count.\n2. **`avg_word_length`:** It returns `0.0` when the text has no words, instead of raising `ZeroDivisionError`.\n3. **`most_common`:** It lowercases the text before counting, so capitalized words are counted. Ties go to the alphabetically first word, and empty text returns `None`.\n\nI didn't add new tests for these cases. The existing tests are the only check I ran.",
 "ttft_ms": 2332,
 "type": "result",
 "duration_ms": 6799,
 "uuid": "[REDACTED]",
 "ttft_stream_ms": 1623,
 "time_to_request_ms": 332,
 "first_content_frame_ms": 1623,
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 "result_index": 0
}