- library-mode, library-contract (cache dir plus the tmpdir npm root), and library-asyncfree now carry a plain/san path segment: both flavors run the same ordinary builds, and the nightly's concurrent both-flavor recipe raced ar/ranlib in the shared dirs ("can't open file ... lib.lib.a"); the per-build -san tag stays, it distinguishes explicitly-sanitized builds within one suite
- the same flavor split lands on npm-static's fixed npm-static-workspace dir (the two flavors even build with different sanitize flags there), provenance's shared outDir, and diagnostics' $TMPDIR/scriptc-diag scratch (some entries emit backend artifacts before failing)
- dec-oracle publishes in the differential/llvm/linux/windows lanes are now atomic (write tmp, rename): the content-keyed path is shared across flavors and lanes, and a truncate-and-rewrite could expose a torn oracle to a concurrent reader
- every other suite already keys its build dirs by a content hash that includes the flavor, and the CAS build cache folds the sanitized flags into its key, so those stay as they are
- proof: three consecutive concurrent both-flavor library-mode runs from a wiped cache all pass 45/45 with zero ar/ranlib failures, and a concurrent both-flavor run of all four library suites passes 125/125 in each flavor
- buf.compare / buf.equals / Buffer.compare arguments that are not statically bytes route through checked-dynamic validators (buffer.compareChk / bytes.equalsChk / bytes.compareChk) running Node's own ladders: ERR_INVALID_ARG_TYPE with the API's argument names and determineSpecificType renders, validateOffset's ERR_OUT_OF_RANGE, undefined slots taking Node defaults — and well-typed dyn values still compute real answers.
- The bytes range ladders (validateOffset, boundsError, checkInt, swap, fill, randomBytes, fs.readSync) stamp their Node codes (ERR_OUT_OF_RANGE / ERR_BUFFER_OUT_OF_BOUNDS / ERR_INVALID_BUFFER_SIZE / ERR_INVALID_ARG_VALUE); validateOffset renders ±Infinity as 'an integer' like Number.isInteger.
- The deprecated `new Buffer(number, enc)` string arm throws Node's ERR_INVALID_ARG_TYPE (the throwing path fires no DEP0005, so compiled silence matches); other ctor forms keep their fences.
- assert.throws/rejects accepts a plain expected object held in a variable (the shared `{ code: ... }` expectation record) through the errValue key walk.
- scr_dyn_specific_type/scr_dyn_arg_type_fail move beside the DOM core (scr_json.c) so always-linked validators render through them; the handle unit keeps the listener gate.
- The differential lanes learn `// @no-deprecation` (Node oracle runs --no-deprecation) for fixtures pinning deprecated-API error paths; corpus 2556 pins the whole ladder byte-identically on both backends.
Chris Tate