fix(cli): add Edge-not-found error handling and document --browser option

- Wrap launch_persistent_context to catch missing Edge with a helpful
  message pointing to microsoft.com/edge
- Document --browser option in docs/cli-reference.md (Session: login)
- Add test for Edge-not-installed error path

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: chkp-roniz

docs/cli-reference.md

@@ -38,7 +38,7 @@ See [Configuration](configuration.md) for details on environment variables and C
 
 | Command | Description | Example |
 |---------|-------------|---------|
-| `login` | Authenticate via browser | `notebooklm login` |
+| `login` | Authenticate via browser | `notebooklm login` / `notebooklm login --browser msedge` |
 | `use <id>` | Set active notebook | `notebooklm use abc123` |
 | `status` | Show current context | `notebooklm status` |
 | `status --paths` | Show configuration paths | `notebooklm status --paths` |
@@ -232,11 +232,24 @@ These CLI capabilities are not available in NotebookLM's web interface:
 Authenticate with Google NotebookLM via browser.
 
 ```bash
-notebooklm login
+notebooklm login [OPTIONS]
 ```
 
 Opens a Chromium browser with a persistent profile. Log in to your Google account, then press Enter in the terminal to save the session.
 
+**Options:**
+- `--storage PATH` - Where to save storage_state.json (default: `$NOTEBOOKLM_HOME/storage_state.json`)
+- `--browser [chromium|msedge]` - Browser to use for login (default: `chromium`). Use `msedge` for Microsoft Edge.
+
+**Examples:**
+```bash
+# Default (Chromium)
+notebooklm login
+
+# Use Microsoft Edge (for orgs that require Edge for SSO)
+notebooklm login --browser msedge
+```
+
 ### Session: `use`
 
 Set the active notebook for subsequent commands.

src/notebooklm/cli/session.py

@@ -227,7 +227,21 @@ def login(storage, browser):
             if browser == "msedge":
                 launch_kwargs["channel"] = "msedge"
 
-            context = p.chromium.launch_persistent_context(**launch_kwargs)
+            try:
+                context = p.chromium.launch_persistent_context(**launch_kwargs)
+            except Exception as e:
+                if browser == "msedge" and (
+                    "executable doesn't exist" in str(e).lower()
+                    or "no such file" in str(e).lower()
+                    or "failed to launch" in str(e).lower()
+                ):
+                    console.print(
+                        "[red]Microsoft Edge not found.[/red]\n"
+                        "Install from: https://www.microsoft.com/edge\n"
+                        "Or use the default Chromium browser: notebooklm login"
+                    )
+                    raise SystemExit(1) from None
+                raise
 
             page = context.pages[0] if context.pages else context.new_page()
             page.goto(NOTEBOOKLM_URL)

tests/unit/cli/test_session.py

@@ -148,6 +148,32 @@ def test_login_chromium_default_no_channel(self, runner, mock_login_browser):
         mock_ensure.assert_called_once()
         assert "channel" not in mock_launch.call_args[1]
 
+    def test_login_msedge_not_installed_shows_helpful_error(self, runner, tmp_path):
+        """Test --browser msedge shows helpful error when Edge is not installed."""
+        with (
+            patch("notebooklm.cli.session._ensure_chromium_installed"),
+            patch("playwright.sync_api.sync_playwright") as mock_pw,
+            patch(
+                "notebooklm.cli.session.get_storage_path", return_value=tmp_path / "storage.json"
+            ),
+            patch(
+                "notebooklm.cli.session.get_browser_profile_dir",
+                return_value=tmp_path / "profile",
+            ),
+        ):
+            mock_launch = (
+                mock_pw.return_value.__enter__.return_value.chromium.launch_persistent_context
+            )
+            mock_launch.side_effect = Exception(
+                "Executable doesn't exist at /ms-edge\nFailed to launch"
+            )
+
+            result = runner.invoke(cli, ["login", "--browser", "msedge"])
+
+        assert result.exit_code == 1
+        assert "Microsoft Edge not found" in result.output
+        assert "microsoft.com/edge" in result.output
+
 
 # =============================================================================
 # USE COMMAND TESTS