diff --git a/src/services/lineageCoverage.js b/src/services/lineageCoverage.js
index b988e11..c3920a7 100644
--- a/src/services/lineageCoverage.js
+++ b/src/services/lineageCoverage.js
@@ -190,6 +190,7 @@ async function auditLatestCohort(sport, deps = {}) {
     const supabase = getClient();
     if (!supabase) return Object.freeze({ audit_available: false, reason: 'no_supabase_env', sport: sp, health: HEALTH.AUDIT_UNAVAILABLE });
 
+    // The head identifies the COHORT (snapshot_id), not one date within it.
     const { data: head, error: headErr } = await supabase
       .from('model_snapshots')
       .select('snapshot_id, game_date, captured_at, code_sha')
@@ -202,15 +203,22 @@ async function auditLatestCohort(sport, deps = {}) {
     const h = head[0];
 
     const { paginate } = require('../utils/safePaginate');
+    // A COHORT IS A snapshot_id, NOT A DATE SLICE OF ONE.
+    //
+    // Measured on the 2026-08-31 03:00Z run: the cohort held 1,970 rows across
+    // TWO game_dates (1,572 on 08-31 and 398 on 08-30, the late slot spanning
+    // midnight ET). Filtering to the head row's date measured 646 of 801
+    // eligible keys and still reported HEALTHY — so a whole date slice with
+    // zero lineage would have been invisible. The audit covers the cohort.
     const rows = await paginate(() => supabase
       .from('model_snapshots')
       .select(AUDIT_COLUMNS)
       .eq('snapshot_id', h.snapshot_id)
-      .eq('sport', sp)
-      .eq('game_date', h.game_date), { key: 'id', label: 'lineageCoverage.auditLatestCohort' });
+      .eq('sport', sp), { key: 'id', label: 'lineageCoverage.auditLatestCohort' });
 
     const audit = auditRows(rows, {
-      snapshot_id: h.snapshot_id, sport: sp, game_date: h.game_date,
+      snapshot_id: h.snapshot_id, sport: sp,
+      game_date: [...new Set(rows.map((r) => r.game_date))].sort().join(','),
       code_sha: h.code_sha, captured_at: h.captured_at,
       retention_terminal: deps.retentionTerminal ?? null,
     });
diff --git a/tests/unit/lineageProductization.test.js b/tests/unit/lineageProductization.test.js
index c04ef60..0d0cda9 100644
--- a/tests/unit/lineageProductization.test.js
+++ b/tests/unit/lineageProductization.test.js
@@ -354,6 +354,26 @@ describe('coverage observer', () => {
       .toEqual([...retention.VALID_LINEAGE_ACTION_FIELDS].sort());
   });
 
+  test('a cohort spanning two game_dates is audited whole, not one slice', () => {
+    // The real 2026-08-31 03:00Z shape: a late slot spanning midnight ET. Rows
+    // from BOTH dates are eligible and both must be counted, or a date slice
+    // with no lineage stays invisible behind a HEALTHY verdict.
+    const mk = (d, p, covered) => ({
+      sport: 'mlb', game_date: d, player_key: p, stat: 'hits', side: 'over',
+      line: 0.5, published: true,
+      ...(covered ? {
+        read_id: `r-${p}`, read_natural_key: `mlb|${d}|${p}|hits|over|0.500000`,
+        lineage_action: 'ORIGIN', claim_digest: 'd', revision_ordinal: 0,
+        lineage_state: 's', lineage_version: 'lin@1', claim_schema_version: 'claim@1',
+        digest_algorithm_version: 'sha256-json-sorted@1',
+      } : {}),
+    });
+    const a = coverage.auditRows([mk('2026-08-31', 'a', true), mk('2026-08-30', 'b', false)]);
+    expect(a.expected_keys).toBe(2);
+    expect(a.covered_keys).toBe(1);
+    expect(a.health).toBe(coverage.HEALTH.PARTIAL_COVERAGE);
+  });
+
   test('an unavailable audit is not a coverage claim', () => {
     expect(coverage.classify({ audit_available: false })).toBe(coverage.HEALTH.AUDIT_UNAVAILABLE);
   });