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Claude Haiku 5.5 (effort default (no --effort flag) · thinking on) on Fix cache invalidation in an incremental static-site builder (transitive partials, config, deletions, same-second edits)

AClaude Haiku 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-17 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first try
Estimated cost
$0.0095
Wall time
44s
Human step-ins
0
Outcome
Pass

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Summary

Exact prompt

# Task: fix the incremental builder's cache invalidation `minibuild.py` builds `site/out/*.html` from `site/src/*.md` and caches what it built in `site/.cache.json`. Users report stale pages: editing a partial (even one included indirectly) doesn't update pages, changing `config.json` doesn't either, quick successive edits within the same second are missed, deleted pages leave their HTML behind, and deleting or hand-editing an output file isn't repaired. Fix the caching in `minibuild.py` so that after **any** sequence of changes, `python3 minibuild.py site` leaves `out/` exactly equal to a clean full build (same files, same bytes, no extra files), while still being incremental: a page is rewritten only if its output would change or its output file is missing/modified. Pages unaffected by a change must not be rewritten at all (the grader checks output file timestamps). Note: the grader resets the timestamps of all output files to an old value before each build, so detect missing/modified outputs by their content (e.g. a hash), not by their timestamps. Only config keys a page actually uses (`site_title` is used by every page; `{{var KEY}}` by the pages containing it, directly or through partials) should cause it to rebuild. Keep the rendering output and the command line unchanged; `build()` should still return the list of rebuilt page names. Standard library only. No network.

Over-invalidating fails the minimal-rebuild checks; under-invalidating fails correctness. Mtime-based caches miss same-second edits, dependency tracking must be transitive and config-key aware, and outputs must be repaired and pruned. 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. clean_build_correct: a first build produces out/ identical to a clean build by the original renderer. 2. For each of 11 change scenarios (indirect partial edit, used config var, site_title, same-mtime source edit, deleted page, deleted output, hand-edited output, new page, no change, touch with identical content, unrelated config key) <scenario>_correct: out/ is byte-identical to a clean full build with no extra files. 3. For each of those 11 scenarios <scenario>_minimal: exactly the expected set of output files is rewritten (others keep their timestamps).

Setup notes: Use Case Scout batch 6 case f06-incremental-build-cache (offline fixture). Prepared with batch6/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. 1-min load average at scoring: 1.36. Claude Code's own reported cost for claude-haiku-5.5: $0.009527. Score: 23/23 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
$0.0095
Wall time
44s
Human step-ins
0
Turns
8
Model usage
ModelInput tokOutput tokCost
AClaude Haiku 5.5anthropic/claude-haiku-5.5effort default (no --effort flag) · thinking on199,6878,011$0.0095

Reproduce this run

  1. Use the use case prompt on the use case page.
  2. Same setup: Claude Haiku 5.5 (anthropic/claude-haiku-5.5, effort default (no --effort flag) · thinking on) via Claude Code 2.1.299 (headless -p), cloud.
  3. It counts as a success only if it meets every success criterion: 1. clean_build_correct: a first build produces out/ identical to a clean build by the original renderer. 2. For each of 11 change scenarios (indirect partial edit, used config var, site_title, same-mtime source edit, deleted page, deleted output, hand-edited output, new page, no change, touch with identical content, unrelated config key) <scenario>_correct: out/ is byte-identical to a clean full build with no extra files. 3. For each of those 11 scenarios <scenario>_minimal: exactly the expected set of output files is rewritten (others keep their timestamps).
  4. 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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Evidence log
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  "result": "I rewrote the caching in `minibuild.py` so it no longer uses `.cache.json`. Every page is rendered in memory and compared byte-for-byte with its file in `out/`, and it is written only if the bytes differ. The change is in `build()`, plus a small `read_bytes` helper and a `shutil` import.\n\nAcross the scenarios I tested in temporary copies of `site/`, `out/` matched a clean build after every step. The steps were: initial build, no-op rerun, an indirect partial edit, quick successive edits, a `year` change, a `site_title` change, a deleted page, a deleted and a hand-edited output, a stray file in `out/`, and adding a page. Unaffected pages kept their timestamps, and `build()` returned the expected lists (for example `[]` on an unchanged rerun, `['about']` after a `year` change).\n\nWhat this means for your requirements:\n- **Partials and config:** a change to any partial, including indirect ones, or to a config key a page uses changes that page's output, so the page is rewritten. A `year` change rebuilds only `about`, because only that page's output changes.\n- **Same-second edits:** there are no mtime checks anymore, so they can't be missed.\n- **Deleted pages and stray files:** `out/` is pruned to exactly the files a clean build would produce.\n- **Hand-edited or deleted outputs:** a differing or missing output is rewritten; the grader's timestamp reset doesn't matter because the check is by content.\n\nChoices I made that you may want to review:\n- Output is now written as explicit UTF-8 bytes, not via text-mode `open(...).write`. On a UTF-8 locale the output is identical; on other locales the bytes could differ from the old script, but the comparison and the clean build use the same code, so they stay consistent.\n- `.cache.json` is no longer read or written. An existing one in `site/` is ignored and can be deleted.\n- Since the cache is gone, the \"which config keys does a page use\" question is answered by the output comparison itself rather than by dependency tracking.\n\nI didn't run the builder in the real `site/` directory, so it still has no `out/` directory. I didn't commit anything, since this isn't a git repository.",
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]

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