[FanWu-ai]

subset('1.0.0 || >2 <1', '>=1 <2') returns false, while reversing the two branches returns true. The contradictory branch matches no versions and should not change the union.

The sawNonNull flag persists between outer-loop iterations. After a valid subset branch sets it to true, a later empty branch inherits that state and causes the whole check to fail. Initialize the flag separately for each candidate branch.

The regressions cover contradictory bounds, incompatible exact versions, exact versions excluded by bounds, branch permutations, multiple superset alternatives, loose/prerelease options, and a genuinely non-subset branch that must still return false.

This is separate from #854 and #894, which address coverage by a union of superset branches. Their current patches retain the cross-branch flag state; the minimal example here has only one superset branch.

Validation on Linux / Node 24.19.0:

• Full pristine npm test: 51 test files passing, 100% statement/branch/function/line coverage, ESLint and template checks passing.
• Full regression run with unchanged source: nine new assertions fail in test/ranges/subset.js; 50 other test files pass.
• Final npm test: all 51 test files pass, 100% coverage, ESLint and template checks pass.
• 134,784 additional assertions cover empty-branch invariance and an independent finite exact-version union oracle.
• git diff --check passes.

The remote CI platform/Node-version matrix has not been run locally. No dependencies, coverage requirements, or tooling are changed.

AI assistance was used to prepare the implementation and regression tests.