diff --git a/hermes_cli/main_install_repair.py b/hermes_cli/main_install_repair.py
index 303e447ddc..e4626ae008 100644
--- a/hermes_cli/main_install_repair.py
+++ b/hermes_cli/main_install_repair.py
@@ -1206,12 +1206,17 @@ def _is_termux_env(env: dict[str, str] | None = None) -> bool:
 
 
 def _is_windows_npm_path(npm_path: str) -> bool:
-    """True if ``npm_path`` points at a Windows npm shim (WSL ``/mnt/c`` interop, ``.cmd``/``.exe``, UNC).
+    """True if ``npm_path`` points at a Windows npm shim (WSL drive interop, ``.cmd``/``.exe``, UNC).
 
     Callers use this only on a POSIX host — on native Windows ``npm.cmd`` is correct.
     """
     low = npm_path.lower()
-    return low.endswith((".exe", ".cmd", ".bat")) or low.startswith("/mnt/") or "\\" in npm_path
+    mount = low.split("/", 3)[2] if low.startswith("/mnt/") else ""
+    return (
+        low.endswith((".exe", ".cmd", ".bat"))
+        or (len(mount) == 1 and mount.isalpha())
+        or "\\" in npm_path
+    )
 
 
 def _resolve_node_runtime_npm() -> str | None:
@@ -1219,7 +1224,7 @@ def _resolve_node_runtime_npm() -> str | None:
 
     On WSL, PATH interop can hand back a Windows npm that fails with EISDIR / symlink errors over
     ``\\\\wsl.localhost\\...`` UNC paths. Refuse it on a POSIX host and re-scan PATH minus the
-    ``/mnt/*`` drive mounts. ``None`` when no suitable npm is reachable.
+    Windows drive mounts. ``None`` when no suitable npm is reachable.
 
     On WSL/Linux ``shutil.which("npm")`` may resolve a Windows npm exposed through PATH interop. See #30271.
     """
@@ -1232,7 +1237,7 @@ def _resolve_node_runtime_npm() -> str | None:
     if not _is_windows_npm_path(npm):
         return npm
     for directory in os.environ.get("PATH", "").split(os.pathsep):
-        if not directory or directory.lower().startswith("/mnt/"):
+        if not directory or _is_windows_npm_path(directory):
             continue
         candidate = shutil.which("npm", path=directory)
         if candidate and not _is_windows_npm_path(candidate):
diff --git a/tests/hermes_cli/test_node_runtime_npm_resolution.py b/tests/hermes_cli/test_node_runtime_npm_resolution.py
new file mode 100644
index 0000000000..e2532701eb
--- /dev/null
+++ b/tests/hermes_cli/test_node_runtime_npm_resolution.py
@@ -0,0 +1,50 @@
+"""Regression coverage for POSIX npm path classification."""
+
+from __future__ import annotations
+
+from unittest.mock import patch
+
+from hermes_cli.main_install_repair import (
+    _is_windows_npm_path,
+    _resolve_node_runtime_npm,
+)
+
+
+def test_windows_npm_path_classifies_only_windows_drive_mounts():
+    assert _is_windows_npm_path("/mnt/c/nodejs/npm")
+    assert not _is_windows_npm_path("/mnt/data/node/bin/npm")
+
+
+def test_resolve_node_runtime_npm_accepts_native_mnt_data_path():
+    native_npm = "/mnt/data/node/bin/npm"
+    with (
+        patch("hermes_cli.main._is_windows", return_value=False),
+        patch("hermes_constants.find_node_executable", return_value=native_npm),
+    ):
+        assert _resolve_node_runtime_npm() == native_npm
+
+
+def test_resolve_node_runtime_npm_rejects_windows_drive_mount(monkeypatch):
+    monkeypatch.setenv("PATH", "/mnt/c/Program Files/nodejs")
+    with (
+        patch("hermes_cli.main._is_windows", return_value=False),
+        patch(
+            "hermes_constants.find_node_executable",
+            return_value="/mnt/c/nodejs/npm",
+        ),
+    ):
+        assert _resolve_node_runtime_npm() is None
+
+
+def test_resolve_node_runtime_npm_rescans_native_mnt_data_path(monkeypatch):
+    native_npm = "/mnt/data/node/bin/npm"
+    monkeypatch.setenv("PATH", "/mnt/data/node/bin")
+    with (
+        patch("hermes_cli.main._is_windows", return_value=False),
+        patch(
+            "hermes_constants.find_node_executable",
+            return_value="/mnt/c/nodejs/npm",
+        ),
+        patch("hermes_cli.main_install_repair.shutil.which", return_value=native_npm),
+    ):
+        assert _resolve_node_runtime_npm() == native_npm