The closure observation introduced in the previous commit appended every distribution importlib.metadata reported and then rejected duplicate names, so on any venv exposing both lib and lib64 on sys.path, which is the normal layout on the Linux hosts this rail runs on, the same dist-info was reported twice and the rail rejected the install state it had just created. The observation now dedupes on the canonical dist-info realpath before emitting facts, mirroring the mechanism _solstone_distributions in scripts/release_install_smoke.py already uses for the same reason. The duplicate check is not weakened: after deduping by realpath, the same distribution name arriving from two distinct dist-info realpaths is a genuine duplicate installation and still fails. The observation also previously dropped a distribution silently when it had no resolvable dist-info path or when its METADATA could not be read. An expected distribution then surfaced as missing, misattributing the fault, and an unexpected relevant distribution vanished entirely, defeating the unexpected-extra check the evidence depends on. Both are now loud with repair text naming the real fault: repair distribution <name> so it has a resolvable dist-info path, and repair distribution <name>'s dist-info METADATA so it can be read. The loudness is scoped to the distributions the closure covers so an unrelated third-party package with an odd layout does not fail the rail. The test evidence is three added tests: test_installed_distribution_observer_dedupes_lib64_dist_info_alias covers the alias succeeding with one entry, test_installed_closure_rejects_duplicate_distribution_realpaths covers the genuine duplicate failure, and test_installed_distribution_observer_reports_relevant_unreadable_metadata covers the specific METADATA repair text rather than missing. Focused suites passed: nvattest proof 50, proof host 20, candidate driver 181, public evidence 4, and ledger 52. Full gate make ci was green with 15488 passed and 17 skipped. Co-Authored-By: Codex <noreply@openai.com>