diff --git a/.changeset/clever-rams-march.md b/.changeset/clever-rams-march.md
new file mode 100644
index 000000000..3912be397
--- /dev/null
+++ b/.changeset/clever-rams-march.md
@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 1910
+---
+Fixed: probe-core's runProbeCli now fails closed on per-item adapter garbage inside a well-shaped report envelope, matching its documented 'fails closed on adapter garbage' contract.
diff --git a/src/probe-core.cts b/src/probe-core.cts
index 2ebd8a641..aca8b211f 100644
--- a/src/probe-core.cts
+++ b/src/probe-core.cts
@@ -96,16 +96,42 @@ function errMessage(e: unknown): string {
   return e instanceof Error ? e.message : String(e);
 }
 
+/**
+ * Structural guard for ONE item of the report `items[]` — enforces the `Item` contract (#1907).
+ * `analyzeCoverage` always emits fully-populated, category/status-validated Items, so this never
+ * rejects legitimate output; it catches an adapter that bypasses the merge and hands back per-item
+ * garbage (e.g. `items:[{}]`) inside a well-shaped envelope — which the container-only guard let
+ * sail through as green output despite the fail-closed docstring below.
+ */
+function isValidItem(item: unknown): item is Item {
+  if (item == null || typeof item !== 'object') return false;
+  const i = item as {
+    requirement_id?: unknown; category?: unknown; status?: unknown;
+    verification?: unknown; resolution?: unknown; reason?: unknown; probe?: unknown;
+  };
+  if (typeof i.requirement_id !== 'string' || !i.requirement_id.trim()) return false;
+  if (typeof i.category !== 'string' || !i.category.trim()) return false;
+  if (!VALID_STATUS.includes(i.status as Status)) return false;
+  if (typeof i.probe !== 'string') return false;
+  // The three nullable fields must be a string or null — never some other type.
+  if (i.verification !== null && typeof i.verification !== 'string') return false;
+  if (i.resolution !== null && typeof i.resolution !== 'string') return false;
+  if (i.reason !== null && typeof i.reason !== 'string') return false;
+  return true;
+}
+
 /**
  * Structural guard for the report an adapter's `analyze` returns. The scaffold types `analyze`
  * loosely (it runs over JSON-parsed input the adapter `as`-casts), so a future adapter (#644)
  * that forgets to validate inside its closure could hand back a malformed object. Rather than
- * stringify garbage as green output, `runProbeCli` checks the report shape and fails closed.
+ * stringify garbage as green output, `runProbeCli` checks the report shape — container AND every
+ * item — and fails closed.
  */
 function isValidReport(report: unknown): report is CoverageReport {
   if (report == null || typeof report !== 'object') return false;
   const r = report as { items?: unknown; coverage?: unknown };
   if (!Array.isArray(r.items)) return false;
+  if (!r.items.every(isValidItem)) return false;
   const c = r.coverage as
     | { applicable?: unknown; resolved?: unknown; unresolved?: unknown; byVerification?: unknown }
     | undefined;
diff --git a/tests/probe-core.test.cjs b/tests/probe-core.test.cjs
index 75f6a2ebb..1331af825 100644
--- a/tests/probe-core.test.cjs
+++ b/tests/probe-core.test.cjs
@@ -332,6 +332,31 @@ describe('probe-core: runProbeCli (generic I/O scaffold, injected io)', () => {
     });
     assert.deepEqual(JSON.parse(out), report);
   });
+  test('per-item garbage inside a well-shaped envelope (items:[{}]) → exits 2, writes nothing (#1907 — matches the "fails closed on adapter garbage" docstring)', () => {
+    // The container is well-shaped (items is an array, coverage has the right scalars) but an item
+    // is an empty object. Before #1907 this sailed through and stringified as green output, despite
+    // the docstring promising it fails closed. A future adapter (#644-class) returning per-item
+    // garbage inside a good envelope must fail closed, not emit garbage as valid coverage.
+    let code; let out = '';
+    pc.runProbeCli(() => ({ items: [{}], coverage: { applicable: 0, resolved: 0, unresolved: 0, byVerification: {} } }), {
+      usage: 'demo', argv: ['node', 'demo', '/req.json'],
+      readFile: () => '[]', write: (s) => { out += s; }, writeErr: () => {}, exit: (c) => { code = c; },
+    });
+    assert.equal(code, 2);
+    assert.equal(out, '');
+  });
+  test('a report with a fully-formed item still writes (per-item validation does not over-reject legitimate coverage)', () => {
+    let out = '';
+    const good = {
+      items: [{ requirement_id: 'R1', category: 'empty', status: 'unresolved', verification: null, resolution: null, reason: null, probe: 'edge' }],
+      coverage: { applicable: 1, resolved: 0, unresolved: 1, byVerification: {} },
+    };
+    pc.runProbeCli(() => good, {
+      usage: 'demo', argv: ['node', 'demo', '/req.json'],
+      readFile: () => '[]', write: (s) => { out += s; }, exit: () => {},
+    });
+    assert.deepEqual(JSON.parse(out), good);
+  });
 });
 
 // ─── CHK-07 (#1278): descriptor-less backward-compat byte-stability ──────────────────────────────