diff --git a/hermes_cli/main.py b/hermes_cli/main.py
index ed8c24c8fa71b..137bc8f1b0931 100644
--- a/hermes_cli/main.py
+++ b/hermes_cli/main.py
@@ -6269,17 +6269,24 @@ def _update_node_dependencies() -> None:
         if not (path / "package.json").exists():
             continue
 
+        # Stream npm output (no `--silent`, no `capture_output`) so optional
+        # dependency postinstall scripts — e.g. `@askjo/camofox-browser`'s
+        # `npx camoufox-js fetch` browser-binary download — print progress
+        # instead of appearing to hang silently for minutes (#18840).  The
+        # `_UpdateOutputStream` wrapper installed by the updater mirrors
+        # streamed output to ``~/.hermes/logs/update.log`` so nothing is lost.
         result = _run_npm_install_deterministic(
             npm,
             path,
-            extra_args=("--silent", "--no-fund", "--no-audit", "--progress=false"),
+            extra_args=("--no-fund", "--no-audit", "--progress=false"),
+            capture_output=False,
         )
         if result.returncode == 0:
             print(f"  ✓ {label}")
             continue
 
         print(f"  ⚠ npm install failed in {label}")
-        stderr = (result.stderr or "").strip()
+        stderr = (result.stderr or "").strip() if result.stderr else ""
         if stderr:
             print(f"    {stderr.splitlines()[-1]}")
 
diff --git a/tests/hermes_cli/test_cmd_update.py b/tests/hermes_cli/test_cmd_update.py
index caac6d37278c9..f485fa0d42b0a 100644
--- a/tests/hermes_cli/test_cmd_update.py
+++ b/tests/hermes_cli/test_cmd_update.py
@@ -128,21 +128,43 @@ def test_update_refreshes_repo_and_tui_node_dependencies(
         #   1. repo root  — slash-command / TUI bridge deps
         #   2. ui-tui/    — Ink TUI deps
         #   3. web/       — install + "npm run build" for the web frontend
-        full_flags = [
+        #
+        # Repo-root and ui-tui installs intentionally omit `--silent` and run
+        # without `capture_output` so optional postinstall scripts (e.g.
+        # `@askjo/camofox-browser`'s browser-binary fetch) print progress —
+        # otherwise long downloads look like a hang (#18840).  The web/ install
+        # keeps `--silent` because its build step is short and noisy.
+        update_flags = [
             "/usr/bin/npm",
             "ci",
-            "--silent",
             "--no-fund",
             "--no-audit",
             "--progress=false",
         ]
         assert npm_calls == [
-            (full_flags, PROJECT_ROOT),
-            (full_flags, PROJECT_ROOT / "ui-tui"),
+            (update_flags, PROJECT_ROOT),
+            (update_flags, PROJECT_ROOT / "ui-tui"),
             (["/usr/bin/npm", "ci", "--silent"], PROJECT_ROOT / "web"),
             (["/usr/bin/npm", "run", "build"], PROJECT_ROOT / "web"),
         ]
 
+        # Regression for #18840: repo root + ui-tui installs must stream output
+        # (capture_output=False) so postinstall progress is visible to the user.
+        repo_and_tui_calls = [
+            call
+            for call in mock_run.call_args_list
+            if call.args
+            and call.args[0][0] == "/usr/bin/npm"
+            and call.args[0][1] == "ci"
+            and call.kwargs.get("cwd") in (PROJECT_ROOT, PROJECT_ROOT / "ui-tui")
+        ]
+        assert len(repo_and_tui_calls) == 2
+        for call in repo_and_tui_calls:
+            assert call.kwargs.get("capture_output") is False, (
+                "repo-root / ui-tui npm install must stream output "
+                "(no capture_output) so Camofox postinstall progress is visible"
+            )
+
     def test_update_non_interactive_skips_migration_prompt(self, mock_args, capsys):
         """When stdin/stdout aren't TTYs, config migration prompt is skipped."""
         with patch("shutil.which", return_value=None), patch(