diff --git a/CHANGELOG.md b/CHANGELOG.md
index 35124a4..15916ef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 ## [Unreleased]
 
+### 수정
+- SARIF 출력 견고성: (1) `startLine`을 방어적으로 coerce합니다 — 외부 엔진(Trivy 등)이 `"12-14"`·`"n/a"` 같은 비정수 line을 내면 `int()`가 던져 리포트 전체가 크래시했습니다(불량 finding 1개 → 리포트 전멸). (2) 공백만 있는 message의 shortDescription 추출 시 IndexError를 방지합니다. (3) `ruleIndex` 계산을 O(n²)에서 O(1)로 바꿨습니다(대량 finding 성능).
+
 ### 추가
 - `appguardrail fix` 명령 — 안전하고 결정적인 자동 수정을 적용합니다(기본 dry-run diff, `--apply`로 기록). 의미를 바꾸지 않는 순수 additive 변환만 수행하며, 첫 변환으로 외부 `target="_blank"` 링크에 `rel="noopener noreferrer"`를 추가합니다(reverse tabnabbing 방지). 동작을 바꾸는 수정(시크릿→env 등)은 위험하므로 자동 적용하지 않고 fix-pack 프롬프트로 남깁니다. scan→fix→verify 루프를 안전하게 닫습니다.
 
diff --git a/appguardrail_core/sarif.py b/appguardrail_core/sarif.py
index 70c10e1..c32e79a 100644
--- a/appguardrail_core/sarif.py
+++ b/appguardrail_core/sarif.py
@@ -32,6 +32,24 @@ def _tags(finding: dict[str, Any]) -> list[str]:
     return tags
 
 
+def _safe_line(value: Any) -> int:
+    """SARIF startLine must be a positive int; external tools emit ranges
+    ("12-14") or "n/a", so coerce defensively — one bad line must not sink
+    the whole report."""
+    try:
+        return max(1, int(value))
+    except (ValueError, TypeError):
+        return 1
+
+
+def _first_line(message: str) -> str:
+    """First non-empty line of a message, capped; never IndexErrors on blanks."""
+    for line in message.splitlines():
+        if line.strip():
+            return line.strip()[:200]
+    return message.strip()[:200] or "Security finding"
+
+
 def findings_to_sarif(
     findings: Iterable[dict[str, Any]], *, tool_version: str = "0.0.0"
 ) -> dict[str, Any]:
@@ -45,10 +63,11 @@ def findings_to_sarif(
         severity = f["severity"]
         refs = f.get("references") or ()
         if rule_id not in rules:
+            rule_index = len(rules)
             rule: dict[str, Any] = {
                 "id": rule_id,
                 "name": rule_id,
-                "shortDescription": {"text": f["message"].strip().splitlines()[0][:200]},
+                "shortDescription": {"text": _first_line(f["message"])},
                 "fullDescription": {"text": f["message"].strip()},
                 "helpUri": refs[0] if refs else "https://github.com/ContextualWisdomLab/appguardrail",
                 "defaultConfiguration": {"level": _LEVEL.get(severity, "note")},
@@ -57,19 +76,20 @@ def findings_to_sarif(
                     "security-severity": _SECURITY_SEVERITY.get(severity, "2.0"),
                 },
             }
+            rule["_index"] = rule_index
             rules[rule_id] = rule
 
         results.append(
             {
                 "ruleId": rule_id,
-                "ruleIndex": list(rules).index(rule_id),
+                "ruleIndex": rules[rule_id]["_index"],
                 "level": _LEVEL.get(severity, "note"),
                 "message": {"text": f["message"].strip()},
                 "locations": [
                     {
                         "physicalLocation": {
                             "artifactLocation": {"uri": f["file"]},
-                            "region": {"startLine": max(1, int(f["line"] or 1))},
+                            "region": {"startLine": _safe_line(f["line"])},
                         }
                     }
                 ],
@@ -96,7 +116,7 @@ def findings_to_sarif(
                         "name": "AppGuardrail",
                         "informationUri": "https://github.com/ContextualWisdomLab/appguardrail",
                         "version": tool_version,
-                        "rules": list(rules.values()),
+                        "rules": [{k: v for k, v in r.items() if k != "_index"} for r in rules.values()],
                     }
                 },
                 "results": results,
diff --git a/tests/test_sarif.py b/tests/test_sarif.py
index d989019..904b3ea 100644
--- a/tests/test_sarif.py
+++ b/tests/test_sarif.py
@@ -54,3 +54,40 @@ def test_empty_findings_valid():
     run = findings_to_sarif([])["runs"][0]
     assert run["results"] == []
     assert run["tool"]["driver"]["rules"] == []
+
+
+# ---- robustness: one malformed finding must not sink the report ----
+
+def test_non_integer_line_does_not_crash():
+    from appguardrail_core.sarif import findings_to_sarif
+    log = findings_to_sarif([
+        {"severity": "HIGH", "rule_id": "trivy-range", "message": "range",
+         "file": "a.tf", "line": "12-14", "context": "app-code"},
+        {"severity": "INFO", "rule_id": "na", "message": "x",
+         "file": "b", "line": "n/a", "context": "doc"},
+    ])
+    regions = [r["locations"][0]["physicalLocation"]["region"]["startLine"]
+               for r in log["runs"][0]["results"]]
+    assert regions == [1, 1]  # coerced, not crashed
+
+
+def test_blank_message_gets_fallback_short_description():
+    from appguardrail_core.sarif import findings_to_sarif
+    log = findings_to_sarif([
+        {"severity": "HIGH", "rule_id": "blank", "message": "   ",
+         "file": "a", "line": 3, "context": "app-code"},
+    ])
+    rule = log["runs"][0]["tool"]["driver"]["rules"][0]
+    assert rule["shortDescription"]["text"]  # non-empty, no IndexError
+
+
+def test_private_index_not_leaked_and_ruleindex_correct():
+    from appguardrail_core.sarif import findings_to_sarif
+    log = findings_to_sarif([
+        {"severity": "HIGH", "rule_id": "a", "message": "m", "file": "f", "line": 1, "context": "app-code"},
+        {"severity": "HIGH", "rule_id": "b", "message": "m", "file": "f", "line": 2, "context": "app-code"},
+        {"severity": "HIGH", "rule_id": "a", "message": "m", "file": "f", "line": 3, "context": "app-code"},
+    ])
+    run = log["runs"][0]
+    assert all("_index" not in r for r in run["tool"]["driver"]["rules"])
+    assert [r["ruleIndex"] for r in run["results"]] == [0, 1, 0]  # deduped, stable