diff --git a/hermes_cli/main.py b/hermes_cli/main.py
index 375561ad6d..b2b181ac68 100644
--- a/hermes_cli/main.py
+++ b/hermes_cli/main.py
@@ -830,7 +830,7 @@ def _print_tui_exit_summary(session_id: Optional[str], active_session_file: Opti
 
 
 def _tui_need_npm_install(root: Path) -> bool:
-    """True when @hermes/ink is missing or node_modules is behind package-lock.json (post-pull)."""
+    """True when @hermes/ink is missing or node_modules is behind package-lock.json."""
     ink = root / "node_modules" / "@hermes" / "ink" / "package.json"
     if not ink.is_file():
         return True
@@ -840,7 +840,32 @@ def _tui_need_npm_install(root: Path) -> bool:
     marker = root / "node_modules" / ".package-lock.json"
     if not marker.is_file():
         return True
-    return lock.stat().st_mtime > marker.stat().st_mtime
+
+    try:
+        wanted = json.loads(lock.read_text(encoding="utf-8")).get("packages") or {}
+        installed = json.loads(marker.read_text(encoding="utf-8")).get("packages") or {}
+    except (OSError, json.JSONDecodeError):
+        return lock.stat().st_mtime > marker.stat().st_mtime
+
+    ignored = {"ideallyInert"}
+
+    def comparable(pkg: dict) -> dict:
+        return {k: v for k, v in pkg.items() if k not in ignored}
+
+    for name, pkg in wanted.items():
+        if name == "":
+            continue
+
+        if name not in installed:
+            if isinstance(pkg, dict) and (pkg.get("optional") or pkg.get("peer")):
+                continue
+            return True
+
+        if isinstance(pkg, dict) and isinstance(installed[name], dict):
+            if comparable(pkg) != comparable(installed[name]):
+                return True
+
+    return False
 
 
 def _find_bundled_tui(tui_dir: Path) -> Optional[Path]:
diff --git a/tests/hermes_cli/test_tui_npm_install.py b/tests/hermes_cli/test_tui_npm_install.py
index bceaf9de0b..e56196e07e 100644
--- a/tests/hermes_cli/test_tui_npm_install.py
+++ b/tests/hermes_cli/test_tui_npm_install.py
@@ -1,4 +1,4 @@
-"""_tui_need_npm_install: auto npm when lockfile ahead of node_modules."""
+"""_tui_need_npm_install: auto npm when node_modules is behind the lockfile."""
 
 import os
 from pathlib import Path
@@ -36,15 +36,39 @@ def test_need_install_when_ink_missing(tmp_path: Path, main_mod) -> None:
     assert main_mod._tui_need_npm_install(tmp_path) is True
 
 
-def test_need_install_when_lock_newer_than_marker(tmp_path: Path, main_mod) -> None:
+def test_no_install_when_lock_newer_but_hidden_lock_matches(tmp_path: Path, main_mod) -> None:
     _touch_ink(tmp_path)
-    (tmp_path / "package-lock.json").write_text("{}")
-    (tmp_path / "node_modules" / ".package-lock.json").write_text("{}")
+    (tmp_path / "package-lock.json").write_text('{"packages":{"node_modules/foo":{"version":"1.0.0"}}}')
+    (tmp_path / "node_modules" / ".package-lock.json").write_text(
+        '{"packages":{"node_modules/foo":{"version":"1.0.0","ideallyInert":true}}}'
+    )
     os.utime(tmp_path / "package-lock.json", (200, 200))
     os.utime(tmp_path / "node_modules" / ".package-lock.json", (100, 100))
+    assert main_mod._tui_need_npm_install(tmp_path) is False
+
+
+def test_need_install_when_required_package_missing_from_hidden_lock(tmp_path: Path, main_mod) -> None:
+    _touch_ink(tmp_path)
+    (tmp_path / "package-lock.json").write_text(
+        '{"packages":{"node_modules/foo":{"version":"1.0.0"},"node_modules/bar":{"version":"1.0.0"}}}'
+    )
+    (tmp_path / "node_modules" / ".package-lock.json").write_text(
+        '{"packages":{"node_modules/foo":{"version":"1.0.0"}}}'
+    )
     assert main_mod._tui_need_npm_install(tmp_path) is True
 
 
+def test_no_install_when_only_optional_peer_package_missing_from_hidden_lock(tmp_path: Path, main_mod) -> None:
+    _touch_ink(tmp_path)
+    (tmp_path / "package-lock.json").write_text(
+        '{"packages":{"node_modules/foo":{"version":"1.0.0"},"node_modules/optional":{"version":"1.0.0","optional":true,"peer":true}}}'
+    )
+    (tmp_path / "node_modules" / ".package-lock.json").write_text(
+        '{"packages":{"node_modules/foo":{"version":"1.0.0"}}}'
+    )
+    assert main_mod._tui_need_npm_install(tmp_path) is False
+
+
 def test_no_install_when_lock_older_than_marker(tmp_path: Path, main_mod) -> None:
     _touch_ink(tmp_path)
     (tmp_path / "package-lock.json").write_text("{}")