The W3C XML Schema Test Suite (2006-11-06, ~13k groups; W3C Document
License, never vendored) runs opt-in via XSTS_ROOT: schemaTests must
compile or be rejected per their expected validity, instanceTests
validate against their group's schema, hrefs resolve against the
referencing file, and include/import locations from disk relative to
the schema. Disagreement counts are asserted exactly; baselines are
pending the first measurement (scheduled 2026-06-14), and failures
are written to /tmp/xsts-failures.txt for the burn-down. Building the
runner immediately caught a denial of service: maxOccurs in the
trillions (groupF009v) OOM-killed the process because the content
automaton unrolled occurrence counts literally; unrolling is capped
at 16384 with larger repetitions treated as unbounded, the libxml2
posture. Roadmap mermaid records the closed behavioral-parity set
(#141-#144, collation), the #139 performance epic, and XSTS moving
to runner-in. Advances #129.