diff --git a/README.md b/README.md
index 9b0ce21..448832e 100644
--- a/README.md
+++ b/README.md
@@ -241,6 +241,11 @@ python -m seedpass_gui
 seedpass-gui
 ```
 
+Install a platform-specific BeeWare backend before running these commands. Only
+the headless `toga-dummy` backend is bundled for tests. Linux users should
+install `toga-gtk`, Windows users need `toga-winforms`, and macOS users require
+`toga-cocoa`.
+
 The GUI works with the same vault and configuration files as the CLI.
 
 ```mermaid
@@ -555,6 +560,10 @@ If the checksum file is missing, generate it manually:
 python scripts/update_checksum.py
 ```
 
+If SeedPass prints a "script checksum mismatch" warning on startup, regenerate
+the checksum with `seedpass util update-checksum` or select "Generate Script
+Checksum" from the Settings menu.
+
 To run mutation tests locally, generate coverage data first and then execute `mutmut`:
 
 ```bash
diff --git a/docs/docs/content/01-getting-started/01-advanced_cli.md b/docs/docs/content/01-getting-started/01-advanced_cli.md
index 1c0bed6..3c86dcc 100644
--- a/docs/docs/content/01-getting-started/01-advanced_cli.md
+++ b/docs/docs/content/01-getting-started/01-advanced_cli.md
@@ -116,6 +116,10 @@ Miscellaneous helper commands.
 | Verify script checksum | `util verify-checksum` | `seedpass util verify-checksum` |
 | Update script checksum | `util update-checksum` | `seedpass util update-checksum` |
 
+If you see a startup warning about a script checksum mismatch,
+run `seedpass util update-checksum` or choose "Generate Script Checksum"
+from the Settings menu to update the stored value.
+
 ### API Commands
 
 Run or stop the local HTTP API.
diff --git a/docs/docs/content/01-getting-started/06-gui_adapter.md b/docs/docs/content/01-getting-started/06-gui_adapter.md
index 779fec4..e2c4917 100644
--- a/docs/docs/content/01-getting-started/06-gui_adapter.md
+++ b/docs/docs/content/01-getting-started/06-gui_adapter.md
@@ -14,6 +14,11 @@ python -m seedpass_gui
 seedpass-gui
 ```
 
+Install a platform-specific BeeWare backend before launching the GUI. The
+distribution only bundles the headless `toga-dummy` backend for automated
+tests. Linux users should install `toga-gtk`, Windows users need
+`toga-winforms`, and macOS users require `toga-cocoa`.
+
 The GUI shares the same encrypted vault and configuration as the command line tool.
 
 To generate a packaged binary, run `briefcase build` (after the initial `briefcase create`).
diff --git a/docs/docs/content/index.md b/docs/docs/content/index.md
index 35b069d..d272206 100644
--- a/docs/docs/content/index.md
+++ b/docs/docs/content/index.md
@@ -497,6 +497,10 @@ If the checksum file is missing, generate it manually:
 python scripts/update_checksum.py
 ```
 
+If SeedPass reports a "script checksum mismatch" warning on startup,
+regenerate the checksum with `seedpass util update-checksum` or select
+"Generate Script Checksum" from the Settings menu.
+
 To run mutation tests locally, generate coverage data first and then execute `mutmut`:
 
 ```bash
diff --git a/src/seedpass/cli.py b/src/seedpass/cli.py
index df7f56c..bddc7ee 100644
--- a/src/seedpass/cli.py
+++ b/src/seedpass/cli.py
@@ -24,6 +24,7 @@ import uvicorn
 from . import api as api_module
 
 import importlib
+import importlib.util
 
 app = typer.Typer(
     help="SeedPass command line interface",
@@ -95,6 +96,14 @@ def _get_nostr_service(ctx: typer.Context) -> NostrService:
     return NostrService(pm)
 
 
+def _gui_backend_available() -> bool:
+    """Return True if a platform-specific BeeWare backend is installed."""
+    for pkg in ("toga_gtk", "toga_winforms", "toga_cocoa"):
+        if importlib.util.find_spec(pkg) is not None:
+            return True
+    return False
+
+
 @app.callback(invoke_without_command=True)
 def main(ctx: typer.Context, fingerprint: Optional[str] = fingerprint_option) -> None:
     """SeedPass CLI entry point.
@@ -740,6 +749,14 @@ def api_stop(ctx: typer.Context, host: str = "127.0.0.1", port: int = 8000) -> N
 @app.command()
 def gui() -> None:
     """Launch the BeeWare GUI."""
+    if not _gui_backend_available():
+        typer.echo(
+            "No BeeWare GUI backend found. Install 'toga-gtk' (Linux), "
+            "'toga-winforms' (Windows) or 'toga-cocoa' (macOS) to run the GUI.",
+            err=True,
+        )
+        raise typer.Exit(1)
+
     from seedpass_gui.app import main
 
     main()
diff --git a/src/tests/test_typer_cli.py b/src/tests/test_typer_cli.py
index c2db4da..fc48c82 100644
--- a/src/tests/test_typer_cli.py
+++ b/src/tests/test_typer_cli.py
@@ -557,6 +557,14 @@ def test_gui_command(monkeypatch):
         "seedpass_gui.app",
         SimpleNamespace(main=fake_main),
     )
+    monkeypatch.setattr(cli.importlib.util, "find_spec", lambda n: True)
     result = runner.invoke(app, ["gui"])
     assert result.exit_code == 0
     assert called.get("called") is True
+
+
+def test_gui_command_no_backend(monkeypatch):
+    monkeypatch.setattr(cli.importlib.util, "find_spec", lambda n: None)
+    result = runner.invoke(app, ["gui"])
+    assert result.exit_code == 1
+    assert "BeeWare GUI backend" in result.stderr