diff --git a/scripts/group_inconclusive_uncertainty.py b/scripts/group_inconclusive_uncertainty.py
new file mode 100755
index 0000000..b9f1b19
--- /dev/null
+++ b/scripts/group_inconclusive_uncertainty.py
@@ -0,0 +1,153 @@
+#!/usr/bin/env python3
+"""Group inconclusive IAMScope findings by uncertainty class for reporting only."""
+
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import sys
+from collections import OrderedDict
+from pathlib import Path
+from typing import Any
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+TEST_OVERRIDE_ENV = "IAMSCOPE_ALLOW_REPO_OUTPUT_FOR_TESTS"
+
+
+def _load_json(path: Path) -> dict[str, Any]:
+    with path.open(encoding="utf-8") as handle:
+        payload = json.load(handle)
+    if not isinstance(payload, dict):
+        raise ValueError(f"expected JSON object in {path}")
+    return payload
+
+
+def _is_relative_to(path: Path, parent: Path) -> bool:
+    try:
+        path.relative_to(parent)
+    except ValueError:
+        return False
+    return True
+
+
+def _reviewer_actions(expected_groups: Path | None) -> dict[str, str]:
+    if expected_groups is None:
+        return {}
+    payload = _load_json(expected_groups)
+    actions: dict[str, str] = {}
+    for group in payload.get("groups", []):
+        if not isinstance(group, dict):
+            continue
+        uncertainty_class = group.get("uncertainty_class")
+        reviewer_action = group.get("reviewer_action")
+        if isinstance(uncertainty_class, str) and isinstance(reviewer_action, str):
+            actions[uncertainty_class] = reviewer_action
+    return actions
+
+
+def group_inconclusive_uncertainty(
+    findings_payload: dict[str, Any],
+    *,
+    reviewer_actions: dict[str, str] | None = None,
+) -> dict[str, Any]:
+    """Return report-only grouping for inconclusive findings.
+
+    This function does not mutate findings, change verdicts, infer exploitability,
+    or make replay-equivalence claims.
+    """
+
+    actions = reviewer_actions or {}
+    grouped: OrderedDict[str, list[str]] = OrderedDict()
+    for finding in findings_payload.get("findings", []):
+        if not isinstance(finding, dict):
+            continue
+        if finding.get("verdict") != "inconclusive":
+            continue
+        uncertainty_class = finding.get("uncertainty_class")
+        finding_id = finding.get("finding_id")
+        if not isinstance(uncertainty_class, str) or not uncertainty_class:
+            uncertainty_class = "uncertainty_class_missing"
+        if not isinstance(finding_id, str) or not finding_id:
+            continue
+        grouped.setdefault(uncertainty_class, []).append(finding_id)
+
+    group_details: list[dict[str, Any]] = []
+    counts: dict[str, int] = {}
+    for uncertainty_class, finding_ids in grouped.items():
+        detail: dict[str, Any] = {
+            "uncertainty_class": uncertainty_class,
+            "count": len(finding_ids),
+            "finding_ids": finding_ids,
+        }
+        if uncertainty_class in actions:
+            detail["reviewer_action"] = actions[uncertainty_class]
+        group_details.append(detail)
+        counts[uncertainty_class] = len(finding_ids)
+
+    top_class = None
+    top_count = 0
+    if group_details:
+        top = max(group_details, key=lambda item: item["count"])
+        top_class = top["uncertainty_class"]
+        top_count = top["count"]
+
+    return {
+        "fixture_id": findings_payload.get("fixture_id"),
+        "report_only": True,
+        "groups": counts,
+        "group_details": group_details,
+        "top_uncertainty_class": top_class,
+        "top_uncertainty_count": top_count,
+        "non_claims": {
+            "does_not_mutate_findings": True,
+            "does_not_change_verdicts": True,
+            "does_not_infer_exploitability": True,
+            "does_not_claim_replay_equivalence": True,
+            "requires_aws_credentials": False,
+        },
+    }
+
+
+def _write_output(output_path: Path, text: str) -> None:
+    output_abs = output_path.resolve()
+    repo_abs = REPO_ROOT.resolve()
+    if _is_relative_to(output_abs, repo_abs) and os.environ.get(TEST_OVERRIDE_ENV) != "1":
+        raise ValueError(
+            f"refusing to write uncertainty grouping output inside repository tree: {output_abs}"
+        )
+    output_abs.parent.mkdir(parents=True, exist_ok=True)
+    output_abs.write_text(text, encoding="utf-8")
+
+
+def main(argv: list[str] | None = None) -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--findings", required=True, help="Path to findings.json")
+    parser.add_argument(
+        "--expected-groups",
+        default=None,
+        help="Optional expected groups JSON used only to enrich reviewer_action fields",
+    )
+    parser.add_argument("--out", default=None, help="Optional output JSON path; stdout if omitted")
+    args = parser.parse_args(argv)
+
+    findings_path = Path(args.findings)
+    expected_path = Path(args.expected_groups) if args.expected_groups else None
+    try:
+        payload = group_inconclusive_uncertainty(
+            _load_json(findings_path),
+            reviewer_actions=_reviewer_actions(expected_path),
+        )
+        text = json.dumps(payload, indent=2, sort_keys=True) + "\n"
+        if args.out:
+            _write_output(Path(args.out), text)
+        else:
+            print(text, end="")
+    except Exception as exc:
+        print(f"error: {exc}", file=sys.stderr)
+        return 1
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/tests/test_group_inconclusive_uncertainty.py b/tests/test_group_inconclusive_uncertainty.py
new file mode 100644
index 0000000..451abd5
--- /dev/null
+++ b/tests/test_group_inconclusive_uncertainty.py
@@ -0,0 +1,104 @@
+from __future__ import annotations
+
+import json
+import subprocess
+from pathlib import Path
+
+from scripts.group_inconclusive_uncertainty import group_inconclusive_uncertainty
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+HELPER = REPO_ROOT / "scripts" / "group_inconclusive_uncertainty.py"
+FIXTURE_DIR = REPO_ROOT / "tests" / "fixtures" / "demo" / "path_overcounting_shared_uncertainty"
+FINDINGS = FIXTURE_DIR / "findings.json"
+EXPECTED_GROUPS = FIXTURE_DIR / "expected_uncertainty_groups.json"
+EXPECTED_COUNTS = {
+    "shared_passrole_target_resource_scope_unknown": 8,
+    "shared_boundary_context_unresolved": 2,
+    "session_policy_context_missing": 1,
+}
+
+
+def _run_helper(*args: str) -> subprocess.CompletedProcess[str]:
+    return subprocess.run(
+        [str(HELPER), *args],
+        cwd=REPO_ROOT,
+        check=False,
+        text=True,
+        capture_output=True,
+    )
+
+
+def _load(path: Path) -> dict:
+    return json.loads(path.read_text())
+
+
+def test_groups_only_inconclusive_findings() -> None:
+    findings = _load(FINDINGS)
+    result = group_inconclusive_uncertainty(findings)
+    inconclusive_ids = {
+        finding["finding_id"] for finding in findings["findings"] if finding["verdict"] == "inconclusive"
+    }
+    grouped_ids = {finding_id for group in result["group_details"] for finding_id in group["finding_ids"]}
+    assert grouped_ids == inconclusive_ids
+    assert len(grouped_ids) == 11
+
+
+def test_demo_fixture_group_counts_and_finding_ids() -> None:
+    result = group_inconclusive_uncertainty(_load(FINDINGS))
+    expected = _load(EXPECTED_GROUPS)
+    expected_ids = {group["uncertainty_class"]: group["finding_ids"] for group in expected["groups"]}
+    actual_ids = {group["uncertainty_class"]: group["finding_ids"] for group in result["group_details"]}
+    assert result["groups"] == EXPECTED_COUNTS
+    assert actual_ids == expected_ids
+    assert result["top_uncertainty_class"] == "shared_passrole_target_resource_scope_unknown"
+    assert result["top_uncertainty_count"] == 8
+
+
+def test_expected_groups_enriches_reviewer_actions() -> None:
+    expected = _load(EXPECTED_GROUPS)
+    actions = {group["uncertainty_class"]: group["reviewer_action"] for group in expected["groups"]}
+    result = group_inconclusive_uncertainty(_load(FINDINGS), reviewer_actions=actions)
+    actual_actions = {group["uncertainty_class"]: group["reviewer_action"] for group in result["group_details"]}
+    assert actual_actions == actions
+
+
+def test_helper_does_not_mutate_input_findings() -> None:
+    before = FINDINGS.read_text()
+    group_inconclusive_uncertainty(_load(FINDINGS))
+    assert FINDINGS.read_text() == before
+
+
+def test_helper_prints_json_to_stdout() -> None:
+    result = _run_helper("--findings", str(FINDINGS), "--expected-groups", str(EXPECTED_GROUPS))
+    assert result.returncode == 0, result.stderr
+    payload = json.loads(result.stdout)
+    assert payload["groups"] == EXPECTED_COUNTS
+    assert payload["non_claims"]["does_not_mutate_findings"] is True
+    assert payload["non_claims"]["does_not_change_verdicts"] is True
+    assert payload["non_claims"]["does_not_infer_exploitability"] is True
+    assert payload["non_claims"]["does_not_claim_replay_equivalence"] is True
+    assert payload["non_claims"]["requires_aws_credentials"] is False
+
+
+def test_helper_writes_to_temp_output_path(tmp_path: Path) -> None:
+    output = tmp_path / "uncertainty-groups.json"
+    result = _run_helper(
+        "--findings",
+        str(FINDINGS),
+        "--expected-groups",
+        str(EXPECTED_GROUPS),
+        "--out",
+        str(output),
+    )
+    assert result.returncode == 0, result.stderr
+    assert json.loads(output.read_text())["groups"] == EXPECTED_COUNTS
+
+
+def test_helper_refuses_repository_output_path() -> None:
+    output = REPO_ROOT / "uncertainty-groups.json"
+    if output.exists():
+        output.unlink()
+    result = _run_helper("--findings", str(FINDINGS), "--out", str(output))
+    assert result.returncode == 1
+    assert "refusing to write uncertainty grouping output inside repository tree" in result.stderr
+    assert not output.exists()