diff --git a/scripts/sample_coverage_report.py b/scripts/sample_coverage_report.py
new file mode 100644
index 00000000..b899d31a
--- /dev/null
+++ b/scripts/sample_coverage_report.py
@@ -0,0 +1,71 @@
+from __future__ import annotations
+
+import argparse
+import json
+from collections import Counter, defaultdict
+from pathlib import Path
+from typing import Dict, List, Set
+
+from mod_regression.sample_inventory import inventory_samples
+
+
+def build_coverage(inventory: List[dict]) -> dict:
+    containers = Counter()
+    captions = Counter()
+    matrix: Dict[str, Counter] = defaultdict(Counter)
+
+    for item in inventory:
+        container = item.get("container") or "unknown"
+        containers[container] += 1
+
+        cap_types = item.get("caption_types_detected") or []
+        if not cap_types:
+            captions["none"] += 1
+            matrix[container]["none"] += 1
+            continue
+
+        for c in cap_types:
+            captions[c] += 1
+            matrix[container][c] += 1
+
+    return {
+        "total_samples": len(inventory),
+        "containers": dict(containers),
+        "captions": dict(captions),
+        "matrix": {k: dict(v) for k, v in matrix.items()},
+    }
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Sample coverage report")
+    parser.add_argument("sample_root", type=Path, help="Root directory containing samples")
+    parser.add_argument("--json-out", type=Path, default=None, help="Write report as JSON to this path")
+    args = parser.parse_args()
+
+    inv = inventory_samples(args.sample_root)
+    report = build_coverage(inv)
+
+    if args.json_out:
+        args.json_out.parent.mkdir(parents=True, exist_ok=True)
+        args.json_out.write_text(json.dumps(report, indent=2), encoding="utf-8")
+
+    # Human-friendly summary
+    print(f"Total samples: {report['total_samples']}")
+    print("\nContainer coverage:")
+    for k, v in sorted(report["containers"].items(), key=lambda x: (-x[1], x[0])):
+        print(f"  {k}: {v}")
+
+    print("\nCaption-type coverage:")
+    for k, v in sorted(report["captions"].items(), key=lambda x: (-x[1], x[0])):
+        print(f"  {k}: {v}")
+
+    print("\nContainer x Caption matrix (counts):")
+    for container, caps in sorted(report["matrix"].items()):
+        caps_str = ", ".join(f"{c}={n}" for c, n in sorted(caps.items()))
+        print(f"  {container}: {caps_str}")
+
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/tests/test_regression/test_sample_coverage_report.py b/tests/test_regression/test_sample_coverage_report.py
new file mode 100644
index 00000000..a60fa529
--- /dev/null
+++ b/tests/test_regression/test_sample_coverage_report.py
@@ -0,0 +1,26 @@
+from scripts.sample_coverage_report import build_coverage
+
+
+def test_build_coverage_basic():
+    inventory = [
+        {"container": "mpegts", "caption_types_detected": ["CEA-608"]},
+        {"container": "mpegts", "caption_types_detected": ["CEA-708"]},
+        {"container": "matroska", "caption_types_detected": []},
+        {"container": None, "caption_types_detected": None},
+    ]
+
+    report = build_coverage(inventory)
+
+    assert report["total_samples"] == 4
+    assert report["containers"]["mpegts"] == 2
+    assert report["containers"]["matroska"] == 1
+    assert report["containers"]["unknown"] == 1
+
+    assert report["captions"]["CEA-608"] == 1
+    assert report["captions"]["CEA-708"] == 1
+    assert report["captions"]["none"] == 2
+
+    assert report["matrix"]["mpegts"]["CEA-608"] == 1
+    assert report["matrix"]["mpegts"]["CEA-708"] == 1
+    assert report["matrix"]["matroska"]["none"] == 1
+    assert report["matrix"]["unknown"]["none"] == 1