diff --git a/scripts/code_health/ts_measure.py b/scripts/code_health/ts_measure.py
index 6ed7fd436b..511eabdfe5 100644
--- a/scripts/code_health/ts_measure.py
+++ b/scripts/code_health/ts_measure.py
@@ -30,6 +30,33 @@ def _cache_root() -> Path:
     return Path(base) / "hermes-code-health"
 
 
+def _install(repo: Path, prefix: Path, pin: str) -> None:
+    npm = shutil.which("npm")
+    if not npm:
+        raise RuntimeError("code health needs node + npm to measure TypeScript files")
+    prefix.mkdir(parents=True, exist_ok=True)
+    # With --prefix, npm reads <prefix>/.npmrc as the project config and never the repo's, so
+    # the repo's install policy (min-release-age, registry) is copied in to apply here too.
+    npmrc = repo / ".npmrc"
+    if npmrc.is_file():
+        shutil.copyfile(npmrc, prefix / ".npmrc")
+    else:
+        (prefix / ".npmrc").unlink(missing_ok=True)
+    what = f"npm install typescript@{pin} into {prefix}"
+    try:
+        subprocess.run(
+            [npm, "install", "--no-save", "--no-package-lock", "--no-audit", "--no-fund",
+             "--prefix", str(prefix), f"typescript@{pin}"],
+            check=True, capture_output=True, text=True, encoding="utf-8", errors="replace",
+            timeout=300, stdin=subprocess.DEVNULL,
+        )
+    # cli.main reports a RuntimeError as a tool failure (exit 2), never as a finding.
+    except subprocess.CalledProcessError as exc:
+        raise RuntimeError(f"{what} failed: {(exc.stderr or '').strip()[-2000:]}") from exc
+    except subprocess.TimeoutExpired as exc:
+        raise RuntimeError(f"{what} timed out after {exc.timeout:.0f}s") from exc
+
+
 def resolve_typescript(repo: Path) -> Path:
     """Directory of the pinned ``typescript`` package, installing it into a cache if absent."""
     pin = pinned_typescript(repo)
@@ -41,14 +68,7 @@ def resolve_typescript(repo: Path) -> Path:
     prefix = _cache_root() / f"typescript-{pin}"
     cand = prefix / "node_modules" / "typescript"
     if _version_at(cand) != pin:
-        npm = shutil.which("npm")
-        if not npm:
-            raise RuntimeError("code health needs node + npm to measure TypeScript files")
-        subprocess.run(
-            [npm, "install", "--no-save", "--no-package-lock", "--no-audit", "--no-fund",
-             "--prefix", str(prefix), f"typescript@{pin}"],
-            check=True, capture_output=True, timeout=300, stdin=subprocess.DEVNULL,
-        )
+        _install(repo, prefix, pin)
     return cand
 
 
diff --git a/tests/scripts/test_code_health_identity.py b/tests/scripts/test_code_health_identity.py
index 98b4688f70..3019db5ef9 100644
--- a/tests/scripts/test_code_health_identity.py
+++ b/tests/scripts/test_code_health_identity.py
@@ -8,12 +8,13 @@ from __future__ import annotations
 
 import json
 import shutil
+import subprocess
 from pathlib import Path
 
 import pytest
 
-from scripts.code_health.ts_measure import pinned_typescript
-from tests.scripts.test_code_health import REPO, _commit, _repo, _verdict
+from scripts.code_health.ts_measure import pinned_typescript, resolve_typescript
+from tests.scripts.test_code_health import REPO, _commit, _git, _repo, _verdict
 
 
 # --- TypeScript identity ----------------------------------------------------------------
@@ -89,3 +90,28 @@ def test_ts_identity_ignores_comments(tmp_path, capsys, files, blocks):
     repo, base = _ts_base(tmp_path, {"web/l.ts": _TS_LEGACY})
     code, out = _verdict(repo, base, files, capsys)
     assert code == (1 if blocks else 0), out
+
+
+# --- m5: the TypeScript install honours the repo's .npmrc and fails as a RuntimeError -----
+
+def test_typescript_install_uses_repo_npmrc_and_fails_cleanly(tmp_path, monkeypatch):
+    npm = shutil.which("npm")
+    if npm is None:
+        pytest.skip("npm is not installed")
+    repo = tmp_path / "repo"
+    repo.mkdir()
+    _git(repo, "init", "-q", "-b", "main")
+    (repo / "package-lock.json").write_text(
+        json.dumps({"packages": {"node_modules/typescript": {"version": pinned_typescript(REPO)}}}),
+        encoding="utf-8")
+    # An unreachable registry and an empty npm cache: only the repo's .npmrc can say so.
+    (repo / ".npmrc").write_text(
+        f"registry=http://127.0.0.1:9/\nfetch-retries=0\ncache={tmp_path / 'npm-cache'}\nmin-release-age=14\n",
+        encoding="utf-8")
+    monkeypatch.setenv("XDG_CACHE_HOME", str(tmp_path / "cache"))
+    with pytest.raises(RuntimeError, match="typescript"):
+        resolve_typescript(repo)
+    prefix = next((tmp_path / "cache" / "hermes-code-health").iterdir())
+    got = subprocess.run([npm, "config", "get", "min-release-age", "--prefix", str(prefix)],
+                         cwd=prefix, capture_output=True, text=True, timeout=60, check=True).stdout.strip()
+    assert got == "14"