Claude Sonnet 5.5 (effort default (no --effort flag) · thinking on) on Make a unified-diff patch applier correct (offset search, no-newline markers, create/delete, atomic failure)

AClaude Sonnet 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-19 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.14
Wall time: 1m
Human step-ins: 0
Outcome: Pass

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# Task: make the patch applier correct `patcher.py` provides `apply_patch(diff_text, root)` which applies a unified diff to the files under directory `root`. It works for the simplest diffs but breaks on real ones and can leave a half-patched tree behind. Fix it (rewrite freely) so it follows `PATCH_RULES.md` exactly. Keep the names `apply_patch` and `PatchError`. Python standard library only; do not shell out to `patch` or `git`. No network. The grader runs a hidden unittest suite that builds small directory trees in temporary folders, calls `apply_patch`, and checks the return value, the exact bytes of every file afterwards, and that `PatchError` is raised (with the tree unchanged) where the rules say so.

The starting applier strips paths wrongly, requires explicit counts, ignores offsets and newline markers, rewrites files hunk by hunk (half-patched trees on failure) and accepts malformed hunks. Tests check exact bytes and an unchanged tree after every failure. 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. All 13 hidden unittest cases pass (git headers and tab timestamps, omitted counts, offset search with carry, +1 before -1, +/-50 limit, no match before previous hunk, no fuzz, no-newline markers, CRLF content and blank context lines, create/delete, failing create/delete/modify, atomic multi-file failure, malformed diffs and unsafe paths).

Setup notes: Use Case Scout batch 7 case g03-unified-diff-apply (offline fixture). Prepared with batch7/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`. Tools: Read/Write/Edit/Glob/Grep/Bash, web disabled. Single run, no retries. Claude Code's own reported cost for claude-sonnet-5.5: $0.138797. Score: 13/13. 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: $0.14
Wall time: 1m
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 on	64,958	7,611	$0.14

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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. All 13 hidden unittest cases pass (git headers and tab timestamps, omitted counts, offset search with carry, +1 before -1, +/-50 limit, no match before previous hunk, no fuzz, no-newline markers, CRLF content and blank context lines, create/delete, failing create/delete/modify, atomic multi-file failure, malformed diffs and unsafe paths).
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.

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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 rewrote `patcher.py` to follow `PATCH_RULES.md`. `apply_patch` and `PatchError` keep their names, and it uses only the standard library. I ran one scenario in a temp directory, not the hidden suite, and it behaved as expected. One diff had a modify (CRLF line, missing final newline) and a create with a new parent directory. A second diff whose first hunk didn't match raised `PatchError` and left the tree unchanged.\n\n- **Parsing:** it reads and writes bytes, and splits only on `\\n`, so `\\r` stays ordinary content. Each hunk body is read by the header's line counts. A hunk with too few or too many lines raises `PatchError`.\n- **Sections:** a section with no hunks, a duplicate path, or both paths `/dev/null` raises `PatchError`. So does a diff with no sections.\n- **Matching:** hunks apply in order to the progressively patched content, using the base, offset and \u00b150 search from rule 6. A hunk can't match before the end of the previous hunk's new lines. The final line's missing-newline state must also match.\n- **Delete:** the patched content has to be empty, which means the removed lines equal the whole file.\n- **Atomicity:** it computes every result in memory first and writes only if all sections succeed. If a write fails partway, it undoes the writes, deletions, created files and created directories, then raises `PatchError`.\n\nI made two choices where the rules were silent. A stray `+`, `-` or space line after a hunk's counts are met raises `PatchError`, unless it begins the next section's `---`/`+++` header pair. A blank line after the counts is ignored. After a successful delete, empty parent directories are left in place.",
  "ttft_ms": 1834,
  "type": "result",
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  "uuid": "[REDACTED]",
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  "time_to_request_ms": 245,
  "first_content_frame_ms": 1073,
  "queued_turn_count": 0,
  "result_index": 0
 }
]