knowledge: 4 verified insights — surviving-mutant triage, source-text wiring assertions, query state vs fetch state, python text-io encoding

log.md

@@ -43,3 +43,7 @@ Append-only. Format: `## [YYYY-MM-DD] <ingest|revise|lint|gap|contradiction|drif
 ## [2026-08-06] revise | Union-merged amendments from the same 15 PRs into 24 existing pages (largest: tests-that-cannot-fail — 7 PRs: per-assertion mutation granularity, restore-mechanism-by-commit-state, suite-total-drop detection; portable-shell-scripts — 8 PRs: POSIX inline set-- reordering, ${VAR:-} vs ${VAR-} colon semantics, quote-by-what-the-text-is; test-data-and-isolation — 6 PRs: env-derived write paths, absent-variable cases, exec-bit fixtures, leak attribution; change-impact/call-site-enumeration — 8 unique additions from 7 path-variants: rename-in-place, same-type reorder, *args forwarding, two-searches-agree fallacy, codemod, coverage completion check). All non-canonical cross-page ids remapped to canonical pages; every added line traced to its source PR hunk (fabricated worker output was detected by orphan-line verification and replaced with true PR content).
 ## [2026-08-06] dedup | Cross-PR duplicate clusters collapsed: client-side rate limiting (8 PR versions at 3 paths → 1), call-site enumeration (7 versions at 7 paths → additions folded into the already-merged canonical page), stderr/exit-0 diagnostics (4 versions at 4 paths → 1), macOS sysroot (2→1), env-var off switch (2→1), completion predicates (2→1), robots.txt (2→1), harness-mediated results (2→1), leaked test artifacts (2→1), orchestration category naming (orchestration vs agent-orchestration → agent-orchestration). Kept distinct after trigger comparison: differential-testing vs differential-run-agreement (setup vs interpretation), unset-versus-empty-parameters vs env-var-off-switches (semantics vs design, cross-linked), import-time-side-effects vs test-level-choice edge (tactics vs level choice, cross-linked). Merged-main near-dup scan (Jaccard over title+trigger, 141 pages): 0 pairs — no duplication among previously merged content.
 ## [2026-08-06] ingest | Reconciled post-consolidation flush PRs #42–#43 (created against pre-#44 main). Folded unique content: platforms/filesystems/permissions-and-exec-bits (+`sh "$SCRIPT"` interpreter-invocation rows — stubs need no exec bit, avoids EDR chmod+x heuristics), platforms/shells/command-text-inspected-before-execution (+gate-AUTHOR step 8: parse all three POSIX quoting forms, expand only ~/$HOME/${HOME}; red-then-green bats evidence), testing/quality/checks-that-cannot-pass (+vacuously-green pre-implementation test row), platforms/processes/tool-diagnostics-without-a-failing-exit-code (+repeat-suppression edge, +clang reproduction source), infrastructure/ci-cd/secrets-handling (+independent credential channels row: gh token vs git SSH vs API token, git push --dry-run / author:@me probes), testing/mocking/what-to-mock (+ESM read-only-bindings DI rows, +PATH-emptied tripwire negative-proof). Dropped as duplicates of the #44 state: #42's rate-limit row (already in timeouts-and-retries + client-side-rate-limiting), #42's warning-only-diagnostics page (same trigger as tool-diagnostics-without-a-failing-exit-code), #42's leak-attribution row (already in test-data-and-isolation).
+## [2026-08-07] ingest | knowledge-flush of 4 queued insights — 4 new pages, 7 existing pages cross-linked. New: testing/quality/surviving-mutant-equivalence-triage (classify a live mutant as missing-test / equivalent / no-coverage before writing anything; when equivalent, delete the redundant branch and correct the justification comment that the equivalence just disproved — Stryker's documented remedy is "try to rewrite the code so it won't occur"), testing/quality/source-text-wiring-assertions (a `>= n` / `toHaveLength(n)` count assertion over a call appearing at several sites stays green when the one site the guard was written for is deleted — enumerate the sites and bind each to a bounded order anchor that occurs exactly once in the file, or to a function-body slice; prove each by deleting only its own site, and run a reformat control. Measured: greedy vs lazy quantifiers give identical verdicts, so the bound and the anchor's uniqueness are what constrain the match), frontend/data-fetching/query-state-vs-fetch-state (a `data | undefined` component prop collapses TanStack Query's two orthogonal axes; a disabled or offline-paused query is `status: pending` with `isLoading === false` and `isError === false`, so "undefined means loading" renders a spinner no fetch will resolve — pass status+fetchStatus or an explicit union and test one case per cell), backend/python/language/default-encoding-in-text-io (a byte round-trip cannot prove an `encoding=` fix on a UTF-8 locale — run the real entry point under `-X warn_default_encoding -W always::EncodingWarning` and assert zero warning lines naming that file). Merged into existing: tests-that-cannot-fail (whole-suite edge row now routes surviving mutants through classification instead of reading them all as missing tests), harness-reverse-controls, behavior-not-implementation, guard-shape-vs-consequence, async-ui-states (+disabled/paused edge row), bytecode-cache-staleness, timezone-and-locale — related links both ways. All cited URLs opened this session; two local reproductions (CPython 3.14.6 EncodingWarning discriminator vs byte-identical round-trip; `@tanstack/query-core@5.100.14` queryObserver.js:308-332 `isLoading = isPending && isFetching`).
+## [2026-08-07] revise | testing/quality/guard-shape-vs-consequence — corrected a misattributed citation found by the pre-PR adversarial pass: the sentence "you cannot safely refactor code if you know you need to adapt the tests afterwards to get them passing again" was presented as the Google Testing Blog article's own, but re-fetching the page shows it is a reader comment (2015-02-04) with different wording ("refactor stuff", "know for sure"). The article body was not retrievable in full, so the bullet now cites the URL for the change-detector category without quoting it, and states the correction inline. The same quote had been copied into a new page in this flush before verification — the lesson being that a citation already present in the wiki is not a verified citation.
+
+## [2026-08-10] ingest | Folded one queued insight into this PR's page rather than opening a sibling: testing/quality/source-text-wiring-assertions +step 2 (make the assertion's subject the comment-stripped file, taking comment ranges from the language's tokenizer — ESLint: "While comments are not technically part of the AST", so a rule reaches them via `sourceCode.getAllComments()` instead of node traversal), +4 edge-case rows (comment-only change reddens the guard; negative `not.toMatch` and count assertions are the shapes comments flip; no parser available; the code under test is itself about comments), +3 Instead-of rows, and a step-6 note that with step 2 the comment control is green by construction so a red one indicts the stripper. Verification corrected the queued directive: measured 2026-08-10 in Node, `src.replace(/\/\*[\s\S]*?\*\//g,'').replace(/\/\/.*$/gm,'')` truncates `"https://api.example.com//v2/items"` to `"https:` and a string-aware variant still truncates `/a//b/` to `/a` — so the page prescribes the tokenizer and records the regex forms only as Instead-of rows with that measurement. Field basis: three guards in one rtb-unified PR reddened on correct code from a JSDoc, a `Number.isFinite` comment, and a `SOURCE.slice(...)` comment. Independent adversarial review then corrected the fold itself: `ts.createSourceFile` yields `comments === undefined` and no comment nodes (so it strips nothing — step 2 now names `getLeadingCommentRanges`/`espree`/`@babel/parser`), the step-6 "green by construction" claim covered only the comment half (a reformat still reddens the bound), the no-parser fallback had to cut each line to EOL because filtering whole comment lines misses trailing comments, and N must be measured on the stripped subject.

wiki/backend/python/index.md

@@ -30,3 +30,4 @@ Match your situation to a "load when" line; load only matching pages.
 |------|-----------|
 | [mutable-state-traps](language/mutable-state-traps.md) | State persists or leaks across calls/requests in a long-lived Python process — one user's data appears for another, values "remembered" between calls; loop-built callbacks all use the last value; reviewing function signatures (mutable defaults), class bodies (class attributes), or module-level objects for hidden sharing; choosing contextvars vs thread-locals for request context |
 | [bytecode-cache-staleness](language/bytecode-cache-staleness.md) | A script or harness rewrites `.py` files and re-runs them in a loop (mutation testing, edit/test/revert, codegen check, bisect) and the result stops tracking what is on disk — a revert that `git diff` reports clean still fails, or an injected change has no effect; choosing between clearing `__pycache__`, refreshing mtime, and hash-based `.pyc` (PEP 552); designing byte-length-preserving mutations |
+| [default-encoding-in-text-io](language/default-encoding-in-text-io.md) | Python opens a text file without `encoding=` (`open`, `Path.read_text`, `subprocess` text mode) and you are adding the argument or writing the regression test that keeps it there; a file-writing bug reproduces on Windows, a `LANG=C` container, or a cp949/cp932 desktop but not on your machine; choosing a test discriminator that does not depend on the runner's locale |

wiki/backend/python/language/bytecode-cache-staleness.md

@@ -9,7 +9,7 @@ sources:
   - https://peps.python.org/pep-0552/
   - https://docs.python.org/3/library/py_compile.html
 last_verified: 2026-08-04
-related: [testing-quality-harness-reverse-controls, testing-quality-tests-that-cannot-fail, backend-python-language-mutable-state-traps]
+related: [backend-python-language-default-encoding-in-text-io, testing-quality-harness-reverse-controls, testing-quality-tests-that-cannot-fail, backend-python-language-mutable-state-traps]
 ---
 
 # Edited Python Source the Interpreter Keeps Ignoring