diff --git a/Jenkinsfile b/Jenkinsfile
index 72b3c8e..996ee45 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -196,11 +196,11 @@ if [ "${install_rc}" -eq 0 ]; then
     -m pytest -ra -vv --durations=20 --junitxml "${JUNIT_XML}"
   tests_rc=$?
   python -c "import json; payload=json.load(open('build/coverage.json', encoding='utf-8')); percent=(payload.get('summary') or {}).get('percent_covered'); print(f'Coverage summary: {percent:.2f}%' if percent is not None else 'Coverage summary unavailable')" || true
-  if [ -f "${COVERAGE_JSON}" ] && [ -f scripts/check_coverage_contract.py ] && [ -f ci/coverage_contract.json ]; then
-    python scripts/check_coverage_contract.py "${COVERAGE_JSON}" ci/coverage_contract.json
+  if [ -f "${COVERAGE_JSON}" ] && [ -f scripts/check_coverage_contract.py ]; then
+    python scripts/check_coverage_contract.py "${COVERAGE_JSON}" --source-root ariadne --threshold "${COVERAGE_MIN}"
     coverage_contract_rc=$?
   else
-    echo "coverage contract check skipped: checker, contract, or coverage report missing"
+    echo "coverage contract check skipped: checker or coverage report missing"
   fi
 fi
 printf '%s\n' "${docs_rc}" > build/docs-naming.rc
diff --git a/scripts/check_coverage_contract.py b/scripts/check_coverage_contract.py
new file mode 100644
index 0000000..6c4d1f7
--- /dev/null
+++ b/scripts/check_coverage_contract.py
@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+"""Enforce Ariadne's per-file source coverage contract."""
+
+from __future__ import annotations
+
+import argparse
+import json
+from pathlib import Path
+
+
+def _source_files(root: Path) -> list[str]:
+    files: list[str] = []
+    for path in sorted(root.rglob("*.py")):
+        if "__pycache__" in path.parts:
+            continue
+        files.append(path.as_posix())
+    return files
+
+
+def _coverage_percent(file_payload: object) -> float | None:
+    if not isinstance(file_payload, dict):
+        return None
+    summary = file_payload.get("summary")
+    if not isinstance(summary, dict):
+        return None
+    value = summary.get("percent_covered")
+    if isinstance(value, (int, float)):
+        return float(value)
+    return None
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("coverage_json")
+    parser.add_argument("--source-root", default="ariadne")
+    parser.add_argument("--threshold", type=float, default=95.0)
+    args = parser.parse_args()
+
+    coverage_path = Path(args.coverage_json)
+    source_root = Path(args.source_root)
+    payload = json.loads(coverage_path.read_text(encoding="utf-8"))
+    files = payload.get("files") if isinstance(payload, dict) else None
+    if not isinstance(files, dict):
+        print(f"{coverage_path}: missing files coverage map")
+        return 1
+
+    failures: list[str] = []
+    for source_file in _source_files(source_root):
+        percent = _coverage_percent(files.get(source_file))
+        if percent is None:
+            failures.append(f"{source_file}: missing from coverage report")
+        elif percent < args.threshold:
+            failures.append(f"{source_file}: {percent:.2f}% below {args.threshold:.2f}%")
+
+    if failures:
+        print("coverage contract failed:")
+        for failure in failures:
+            print(f" - {failure}")
+        return 1
+
+    print(f"coverage contract passed: {len(_source_files(source_root))} files >= {args.threshold:.2f}%")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())