On main: imp87 prior attempt mixed

tests/test_phase_z2_imp30_first_render.py

@@ -1012,11 +1012,14 @@ def test_u6_empty_shell_unit_listed_with_empty_identifiers():
     assert entry["selection_path"] == "empty_shell"
     assert entry["fallback_reason"] == "no_v4_rank_1_for_any_section"
     assert entry["v4_rank"] is None
-    # full_mdx_coverage holds because shell.source_section_ids covers every
-    # aligned section id — u4 deliberately sets this so coverage stays True
-    # under the terminal first-render invariant.
-    assert status["full_mdx_coverage"] is True
-    assert status["overall"] == "PASS"
+    # IMP-87 u4 inversion (Stage 1 anchor c53722ad): empty-shell-only runs
+    # MUST NOT report PASS / full_mdx_coverage. u1 redefines coverage over
+    # content units (frame_template_id == "__empty__" excluded) and u2 routes
+    # empty_shell_dominant slides into the EMPTY_SHELL_NO_CONTENT branch
+    # before the legacy 4-way ladder. Aligned section ids covered only by
+    # the shell unit are surfaced in filtered_section_ids instead.
+    assert status["full_mdx_coverage"] is False
+    assert status["overall"] == "EMPTY_SHELL_NO_CONTENT"
 
 
 # ─── u6 case 4 : mixed selection — provisional + normal units coexist ──
@@ -1357,10 +1360,14 @@ def test_u7_e2e_zero_v4_empty_shell_status_surface(u7_patch_selector_deps):
     assert shell_entry["phase_z_status"] == "empty_shell"
     assert shell_entry["frame_template_id"] == "__empty__"
     assert shell_entry["source_section_ids"] == ["S1", "S2"]
-    # Coverage check — both sections counted as covered by the shell unit
-    # (rendered=True path; PASS enum unchanged by provisional qualifier).
-    assert status["full_mdx_coverage"] is True
-    assert status["overall"] == "PASS"
+    # IMP-87 u4 inversion (Stage 1 anchor c53722ad): even at the e2e level
+    # an empty-shell-only run must surface as EMPTY_SHELL_NO_CONTENT, not
+    # PASS. u1 excludes __empty__ frames from content coverage so the two
+    # aligned sections end up in filtered_section_ids; u2's
+    # empty_shell_dominant branch then short-circuits the overall ladder
+    # ahead of any visual_check verdict.
+    assert status["full_mdx_coverage"] is False
+    assert status["overall"] == "EMPTY_SHELL_NO_CONTENT"
 
 
 # ─── u7 case 3 : e2e normal path unchanged when opt-in flags both on ─────