diff --git a/changes/1115.feature.rst b/changes/1115.feature.rst
new file mode 100644
index 000000000..76c59fe7f
--- /dev/null
+++ b/changes/1115.feature.rst
@@ -0,0 +1 @@
+The ``-C``/``--config`` option can now be used to override app settings from the command line.
diff --git a/docs/reference/commands/index.rst b/docs/reference/commands/index.rst
index 9579131bf..c3d8573a5 100644
--- a/docs/reference/commands/index.rst
+++ b/docs/reference/commands/index.rst
@@ -20,6 +20,31 @@ Common options
 
 The following options are available to all commands:
 
+``-C <KEY=VALUE>`` / ``--config <KEY=VALUE>``
+---------------------------------------------
+
+Override the value of an app's configuration in ``pyproject.toml`` with the provided
+value.
+
+The key will be applied *after* (and will therefore take precedence over) any platform
+or backend-specific configuration has been merged into the app's configuration. The key
+must be a "top level" TOML key. The use of `dotted keys
+<https://toml.io/en/v1.0.0#keys>`__ to define nested configuration structures is not
+permitted.
+
+The value passed to the setting should be valid TOML. If the value being overridden is a
+string, this means you must quote the value. This may require the use of escape
+sequences at the command line to ensure the value provided to Briefcase by the shell
+includes the quotes.
+
+For example, to override the template used by the create command, you can use ``-C
+template=...``, but the value must be quoted::
+
+    briefcase create -C template=\"https://example.com/template\"
+
+The only app key that *cannot* be overridden with ``-C`` is ``app_name``, as it is used
+to identify apps.
+
 ``-h`` / ``--help``
 -------------------
 
diff --git a/src/briefcase/__main__.py b/src/briefcase/__main__.py
index a868c422d..703052fde 100644
--- a/src/briefcase/__main__.py
+++ b/src/briefcase/__main__.py
@@ -20,8 +20,11 @@ def main():
     try:
         Command, extra_cmdline = parse_cmdline(sys.argv[1:])
         command = Command(logger=logger, console=console)
-        options = command.parse_options(extra=extra_cmdline)
-        command.parse_config(Path.cwd() / "pyproject.toml")
+        options, overrides = command.parse_options(extra=extra_cmdline)
+        command.parse_config(
+            Path.cwd() / "pyproject.toml",
+            overrides=overrides,
+        )
         command(**options)
     except HelpText as e:
         logger.info()
diff --git a/src/briefcase/commands/base.py b/src/briefcase/commands/base.py
index 9c511c18a..c776f957b 100644
--- a/src/briefcase/commands/base.py
+++ b/src/briefcase/commands/base.py
@@ -11,6 +11,7 @@
 from abc import ABC, abstractmethod
 from argparse import RawDescriptionHelpFormatter
 from pathlib import Path
+from typing import Any
 
 from cookiecutter import exceptions as cookiecutter_exceptions
 from cookiecutter.repository import is_repo_url
@@ -103,6 +104,38 @@ def split_passthrough(args):
         return args[:pos], args[pos + 1 :]
 
 
+def parse_config_overrides(config_overrides: list[str] | None) -> dict[str, Any]:
+    """Parse command line -C/--config option overrides.
+
+    :param config_overrides: The values passed in as configuration overrides. Each value
+        *should* be a "key=<valid TOML>" string.
+    :returns: A dictionary of app configuration keys to override and their new values.
+    :raises BriefcaseCommandError: if any of the values can't be parsed as valid TOML.
+    """
+    overrides = {}
+    if config_overrides:
+        for override in config_overrides:
+            try:
+                # Do initial checks of the key being overridden.
+                # These catch cases that would be valid TOML, but would result
+                # in invalid app configurations.
+                key, _ = override.split("=", 1)
+                if "." in key:
+                    raise BriefcaseConfigError(
+                        "Can't override multi-level configuration keys."
+                    )
+                elif key == "app_name":
+                    raise BriefcaseConfigError("The app name cannot be overridden.")
+
+                # Now actually parse the value
+                overrides.update(tomllib.loads(override))
+            except ValueError as e:
+                raise BriefcaseConfigError(
+                    f"Unable to parse configuration override {override}"
+                ) from e
+    return overrides
+
+
 class BaseCommand(ABC):
     cmd_line = "briefcase {command} {platform} {output_format}"
     supported_host_os = {"Darwin", "Linux", "Windows"}
@@ -614,7 +647,8 @@ def parse_options(self, extra):
 
         :param extra: the remaining command line arguments after the initial
             ArgumentParser runs over the command line.
-        :return: dictionary of parsed arguments for Command
+        :return: dictionary of parsed arguments for Command, and a dictionary of parsed
+            configuration overrides.
         """
         default_format = getattr(
             get_platforms().get(self.platform), "DEFAULT_OUTPUT_FORMAT", None
@@ -674,7 +708,10 @@ def parse_options(self, extra):
         self.logger.verbosity = options.pop("verbosity")
         self.logger.save_log = options.pop("save_log")
 
-        return options
+        # Parse the configuration overrides
+        overrides = parse_config_overrides(options.pop("config_overrides"))
+
+        return options, overrides
 
     def clone_options(self, command):
         """Clone options from one command to this one.
@@ -687,12 +724,20 @@ def add_default_options(self, parser):
 
         :param parser: a stub argparse parser for the command.
         """
+        parser.add_argument(
+            "-C",
+            "--config",
+            dest="config_overrides",
+            action="append",
+            metavar="KEY=VALUE",
+            help="Override the value of the app configuration item KEY with VALUE",
+        )
         parser.add_argument(
             "-v",
             "--verbosity",
             action="count",
             default=0,
-            help="Enable verbose logging. Use -vv and -vvv to increase logging verbosity.",
+            help="Enable verbose logging. Use -vv and -vvv to increase logging verbosity",
         )
         parser.add_argument("-V", "--version", action="version", version=__version__)
         parser.add_argument(
@@ -780,7 +825,7 @@ def add_options(self, parser):
         :param parser: a stub argparse parser for the command.
         """
 
-    def parse_config(self, filename):
+    def parse_config(self, filename, overrides):
         try:
             with open(filename, "rb") as config_file:
                 # Parse the content of the pyproject.toml file, extracting
@@ -792,6 +837,8 @@ def parse_config(self, filename):
                     output_format=self.output_format,
                 )
 
+                # Create the global config
+                global_config.update(overrides)
                 self.global_config = create_config(
                     klass=GlobalConfig,
                     config=global_config,
@@ -801,6 +848,7 @@ def parse_config(self, filename):
                 for app_name, app_config in app_configs.items():
                     # Construct an AppConfig object with the final set of
                     # configuration options for the app.
+                    app_config.update(overrides)
                     self.apps[app_name] = create_config(
                         klass=AppConfig,
                         config=app_config,
diff --git a/src/briefcase/commands/create.py b/src/briefcase/commands/create.py
index 44b938afc..4baa19caf 100644
--- a/src/briefcase/commands/create.py
+++ b/src/briefcase/commands/create.py
@@ -831,7 +831,11 @@ def verify_app_tools(self, app: AppConfig):
         super().verify_app_tools(app)
         NativeAppContext.verify(tools=self.tools, app=app)
 
-    def __call__(self, app: AppConfig | None = None, **options) -> dict | None:
+    def __call__(
+        self,
+        app: AppConfig | None = None,
+        **options,
+    ) -> dict | None:
         # Confirm host compatibility, that all required tools are available,
         # and that the app configuration is finalized.
         self.finalize(app)
diff --git a/src/briefcase/commands/dev.py b/src/briefcase/commands/dev.py
index 5380c2b16..ee1a30ffb 100644
--- a/src/briefcase/commands/dev.py
+++ b/src/briefcase/commands/dev.py
@@ -1,8 +1,9 @@
+from __future__ import annotations
+
 import os
 import subprocess
 import sys
 from pathlib import Path
-from typing import List, Optional
 
 from briefcase.commands.run import RunAppMixin
 from briefcase.config import AppConfig
@@ -112,7 +113,7 @@ def run_dev_app(
         app: AppConfig,
         env: dict,
         test_mode: bool,
-        passthrough: List[str],
+        passthrough: list[str],
         **options,
     ):
         """Run the app in the dev environment.
@@ -174,11 +175,11 @@ def get_environment(self, app, test_mode: bool):
 
     def __call__(
         self,
-        appname: Optional[str] = None,
-        update_requirements: Optional[bool] = False,
-        run_app: Optional[bool] = True,
-        test_mode: Optional[bool] = False,
-        passthrough: Optional[List[str]] = None,
+        appname: str | None = None,
+        update_requirements: bool | None = False,
+        run_app: bool | None = True,
+        test_mode: bool | None = False,
+        passthrough: list[str] | None = None,
         **options,
     ):
         # Which app should we run? If there's only one defined
diff --git a/src/briefcase/commands/new.py b/src/briefcase/commands/new.py
index aa24ce22b..7979aa5bc 100644
--- a/src/briefcase/commands/new.py
+++ b/src/briefcase/commands/new.py
@@ -1,7 +1,8 @@
+from __future__ import annotations
+
 import re
 import unicodedata
 from email.utils import parseaddr
-from typing import Optional
 from urllib.parse import urlparse
 
 from packaging.version import Version
@@ -75,7 +76,7 @@ def binary_path(self, app):
         """A placeholder; New command doesn't have a binary path."""
         raise NotImplementedError()
 
-    def parse_config(self, filename):
+    def parse_config(self, filename, overrides):
         """There is no configuration when starting a new project; this implementation
         overrides the base so that no config is parsed."""
         pass
@@ -432,8 +433,8 @@ def build_app_context(self):
 
     def new_app(
         self,
-        template: Optional[str] = None,
-        template_branch: Optional[str] = None,
+        template: str | None = None,
+        template_branch: str | None = None,
         **options,
     ):
         """Ask questions to generate a new application, and generate a stub project from
@@ -520,8 +521,8 @@ def verify_tools(self):
 
     def __call__(
         self,
-        template: Optional[str] = None,
-        template_branch: Optional[str] = None,
+        template: str | None = None,
+        template_branch: str | None = None,
         **options,
     ):
         # Confirm host compatibility, and that all required tools are available.
diff --git a/src/briefcase/commands/open.py b/src/briefcase/commands/open.py
index ec8f38906..5d7b34629 100644
--- a/src/briefcase/commands/open.py
+++ b/src/briefcase/commands/open.py
@@ -44,7 +44,11 @@ def open_app(self, app: AppConfig, **options):
 
         return state
 
-    def __call__(self, app: AppConfig | None = None, **options):
+    def __call__(
+        self,
+        app: AppConfig | None = None,
+        **options,
+    ):
         # Confirm host compatibility, that all required tools are available,
         # and that the app configuration is finalized.
         self.finalize(app)
diff --git a/src/briefcase/commands/publish.py b/src/briefcase/commands/publish.py
index 689089f8f..c710fdee0 100644
--- a/src/briefcase/commands/publish.py
+++ b/src/briefcase/commands/publish.py
@@ -55,7 +55,11 @@ def _publish_app(self, app: AppConfig, channel: str, **options) -> dict | None:
 
         return state
 
-    def __call__(self, channel=None, **options):
+    def __call__(
+        self,
+        channel: str | None = None,
+        **options,
+    ):
         # Confirm host compatibility, that all required tools are available,
         # and that all app configurations are finalized.
         self.finalize()
diff --git a/src/briefcase/commands/upgrade.py b/src/briefcase/commands/upgrade.py
index c130d3847..c432a0b22 100644
--- a/src/briefcase/commands/upgrade.py
+++ b/src/briefcase/commands/upgrade.py
@@ -1,6 +1,7 @@
+from __future__ import annotations
+
 import sys
 from operator import attrgetter
-from typing import List, Set, Type
 
 from briefcase.exceptions import (
     BriefcaseCommandError,
@@ -50,12 +51,12 @@ def add_options(self, parser):
             help="The Briefcase-managed tool to upgrade. If no tool is named, all tools will be upgraded.",
         )
 
-    def get_tools_to_upgrade(self, tool_list: Set[str]) -> List[ManagedTool]:
+    def get_tools_to_upgrade(self, tool_list: set[str]) -> list[ManagedTool]:
         """Returns set of managed Tools that can be upgraded.
 
         Raises ``BriefcaseCommandError`` if user list contains any invalid tool names.
         """
-        upgrade_list: set[Type[Tool]]
+        upgrade_list: set[type[Tool]]
         tools_to_upgrade: set[ManagedTool] = set()
 
         # Validate user tool list against tool registry
@@ -94,7 +95,7 @@ def get_tools_to_upgrade(self, tool_list: Set[str]) -> List[ManagedTool]:
 
         return sorted(list(tools_to_upgrade), key=attrgetter("name"))
 
-    def __call__(self, tool_list: List[str], list_tools: bool = False, **options):
+    def __call__(self, tool_list: list[str], list_tools: bool = False, **options):
         """Perform tool upgrades or list tools qualifying for upgrade.
 
         :param tool_list: List of tool names from user to upgrade.
diff --git a/src/briefcase/platforms/linux/appimage.py b/src/briefcase/platforms/linux/appimage.py
index ceaa4c85f..09447cebc 100644
--- a/src/briefcase/platforms/linux/appimage.py
+++ b/src/briefcase/platforms/linux/appimage.py
@@ -70,9 +70,9 @@ def add_options(self, parser):
 
     def parse_options(self, extra):
         """Extract the use_docker option."""
-        options = super().parse_options(extra)
+        options, overrides = super().parse_options(extra)
         self.use_docker = options.pop("use_docker")
-        return options
+        return options, overrides
 
     def clone_options(self, command):
         """Clone the use_docker option."""
diff --git a/src/briefcase/platforms/linux/system.py b/src/briefcase/platforms/linux/system.py
index 12792e869..5b0615524 100644
--- a/src/briefcase/platforms/linux/system.py
+++ b/src/briefcase/platforms/linux/system.py
@@ -365,10 +365,10 @@ def add_options(self, parser):
 
     def parse_options(self, extra):
         """Extract the target_image option."""
-        options = super().parse_options(extra)
+        options, overrides = super().parse_options(extra)
         self.target_image = options.pop("target")
 
-        return options
+        return options, overrides
 
     def clone_options(self, command):
         """Clone the target_image option."""
diff --git a/src/briefcase/platforms/windows/__init__.py b/src/briefcase/platforms/windows/__init__.py
index dc2821702..deed7bb9e 100644
--- a/src/briefcase/platforms/windows/__init__.py
+++ b/src/briefcase/platforms/windows/__init__.py
@@ -229,9 +229,9 @@ def add_options(self, parser):
 
     def parse_options(self, extra):
         """Require the Windows SDK tool if an `identity` is specified for signing."""
-        options = super().parse_options(extra=extra)
+        options, overrides = super().parse_options(extra=extra)
         self._windows_sdk_needed = options["identity"] is not None
-        return options
+        return options, overrides
 
     def sign_file(
         self,
diff --git a/tests/commands/base/test_parse_config.py b/tests/commands/base/test_parse_config.py
index 7f89c5a72..03fa549f6 100644
--- a/tests/commands/base/test_parse_config.py
+++ b/tests/commands/base/test_parse_config.py
@@ -9,7 +9,7 @@ def test_missing_config(base_command):
     """If the configuration file doesn't exit, raise an error."""
     filename = base_command.base_path / "does_not_exist.toml"
     with pytest.raises(BriefcaseConfigError, match="Configuration file not found"):
-        base_command.parse_config(filename)
+        base_command.parse_config(filename, {})
 
 
 def test_incomplete_global_config(base_command):
@@ -32,7 +32,7 @@ def test_incomplete_global_config(base_command):
         BriefcaseConfigError,
         match=r"Global configuration is incomplete \(missing 'bundle', 'project_name'\)",
     ):
-        base_command.parse_config(filename)
+        base_command.parse_config(filename, {})
 
 
 def test_incomplete_config(base_command):
@@ -56,11 +56,11 @@ def test_incomplete_config(base_command):
         BriefcaseConfigError,
         match=r"Configuration for 'my-app' is incomplete \(missing 'sources'\)",
     ):
-        base_command.parse_config(filename)
+        base_command.parse_config(filename, {})
 
 
 def test_parse_config(base_command):
-    """A well-formed configuration file can be augmented by the command line."""
+    """A well-formed configuration file can turned into a set of configurations."""
     filename = base_command.base_path / "pyproject.toml"
     create_file(
         filename,
@@ -82,8 +82,8 @@ def test_parse_config(base_command):
     """,
     )
 
-    # Parse the configuration
-    base_command.parse_config(filename)
+    # Parse the configuration, no overrides
+    base_command.parse_config(filename, {})
 
     # There is a global configuration object
     assert repr(base_command.global_config) == "<Sample project v1.2.3 GlobalConfig>"
@@ -113,3 +113,104 @@ def test_parse_config(base_command):
     assert base_command.apps["secondapp"].bundle == "org.beeware"
     assert base_command.apps["secondapp"].mystery == "sekrits"
     assert base_command.apps["secondapp"].extra == "something"
+
+
+def test_parse_config_with_overrides(base_command):
+    """A well-formed configuration file can be augmented by the command line."""
+    filename = base_command.base_path / "pyproject.toml"
+    create_file(
+        filename,
+        """
+        [tool.briefcase]
+        project_name = "Sample project"
+        version = "1.2.3"
+        description = "A sample app"
+        bundle = "org.beeware"
+        mystery = 'default'
+
+        [tool.briefcase.app.firstapp]
+        sources = ['src/firstapp']
+
+        [tool.briefcase.app.secondapp]
+        sources = ['src/secondapp']
+        extra = 'something'
+        mystery = 'sekrits'
+    """,
+    )
+
+    # Parse the configuration, with overrides
+    base_command.parse_config(
+        filename,
+        {
+            "version": "2.3.4",
+            "custom": "something special",
+            "mystery": "overridden",
+        },
+    )
+
+    # There is a global configuration object. It picks up the override values.
+    assert repr(base_command.global_config) == "<Sample project v2.3.4 GlobalConfig>"
+    assert base_command.global_config.project_name == "Sample project"
+    assert base_command.global_config.bundle == "org.beeware"
+    assert base_command.global_config.version == "2.3.4"
+    assert base_command.global_config.custom == "something special"
+    assert base_command.global_config.mystery == "overridden"
+
+    # The first app will have all the base attributes required by an app,
+    # defined in the config file, with the values from the overrides taking precedence.
+    assert (
+        repr(base_command.apps["firstapp"]) == "<org.beeware.firstapp v2.3.4 AppConfig>"
+    )
+    assert base_command.apps["firstapp"].project_name == "Sample project"
+    assert base_command.apps["firstapp"].app_name == "firstapp"
+    assert base_command.apps["firstapp"].bundle == "org.beeware"
+    assert base_command.apps["firstapp"].version == "2.3.4"
+    assert base_command.apps["firstapp"].custom == "something special"
+    assert base_command.apps["firstapp"].mystery == "overridden"
+    assert not hasattr(base_command.apps["firstapp"], "extra")
+
+    # The second app is much the same. The value for `mystery`` is overridden by the
+    # command line (superseding the app override); but the `extra` app-specific value
+    # is preserved.
+    assert (
+        repr(base_command.apps["secondapp"])
+        == "<org.beeware.secondapp v2.3.4 AppConfig>"
+    )
+    assert base_command.apps["secondapp"].project_name == "Sample project"
+    assert base_command.apps["secondapp"].app_name == "secondapp"
+    assert base_command.apps["secondapp"].bundle == "org.beeware"
+    assert base_command.apps["secondapp"].version == "2.3.4"
+    assert base_command.apps["secondapp"].custom == "something special"
+    assert base_command.apps["secondapp"].mystery == "overridden"
+    assert base_command.apps["secondapp"].extra == "something"
+
+
+def test_parse_config_with_invalid_override(base_command):
+    """If an override value doesn't pass validation, an exception is raised."""
+    filename = base_command.base_path / "pyproject.toml"
+    create_file(
+        filename,
+        """
+        [tool.briefcase]
+        project_name = "Sample project"
+        version = "1.2.3"
+        description = "A sample app"
+        bundle = "org.beeware"
+        mystery = 'default'
+
+        [tool.briefcase.app.firstapp]
+        sources = ['src/firstapp']
+    """,
+    )
+
+    # Parse the configuration, with overrides
+    with pytest.raises(
+        BriefcaseConfigError,
+        match=r"Version numbers must be PEP440 compliant",
+    ):
+        base_command.parse_config(
+            filename,
+            {
+                "version": "not-a-version-number",
+            },
+        )
diff --git a/tests/commands/base/test_parse_config_overrides.py b/tests/commands/base/test_parse_config_overrides.py
new file mode 100644
index 000000000..6c7cb1f3b
--- /dev/null
+++ b/tests/commands/base/test_parse_config_overrides.py
@@ -0,0 +1,79 @@
+import pytest
+
+from briefcase.commands.base import parse_config_overrides
+from briefcase.exceptions import BriefcaseConfigError
+
+
+@pytest.mark.parametrize(
+    "overrides, values",
+    [
+        # No content
+        (None, {}),
+        ([], {}),
+        # Boolean
+        (["key=true"], {"key": True}),
+        # Integers
+        (["key=42"], {"key": 42}),
+        (["key=-42"], {"key": -42}),
+        # Integers
+        (["key=42.37"], {"key": 42.37}),
+        (["key=-42.37"], {"key": -42.37}),
+        # Strings
+        (["key='hello'"], {"key": "hello"}),
+        (["key=''"], {"key": ""}),
+        (["key='42'"], {"key": "42"}),
+        (['key="hello"'], {"key": "hello"}),
+        (['key=""'], {"key": ""}),
+        (['key="42"'], {"key": "42"}),
+        # List
+        (['key=[1, "two", true]'], {"key": [1, "two", True]}),
+        # Dictionary
+        (['key={a=1, b="two", c=true}'], {"key": {"a": 1, "b": "two", "c": True}}),
+        # Multiple values
+        (
+            [
+                "key1=42",
+                'key2="hello"',
+                'key3=[1, "two", true]',
+                'key4={a=1, b="two", c=true}',
+            ],
+            {
+                "key1": 42,
+                "key2": "hello",
+                "key3": [1, "two", True],
+                "key4": {"a": 1, "b": "two", "c": True},
+            },
+        ),
+    ],
+)
+def test_valid_overrides(overrides, values):
+    """Valid values can be parsed as config overrides."""
+    assert parse_config_overrides(overrides) == values
+
+
+@pytest.mark.parametrize(
+    "overrides, message",
+    [
+        # Bare string
+        (["foobar"], r"Unable to parse configuration override "),
+        # Unquoted string
+        (["key=foobar"], r"Unable to parse configuration override "),
+        # Unbalanced quote
+        (["key='foobar"], r"Unable to parse configuration override "),
+        # Unmatched brackets
+        (['key=[1, "two",'], r"Unable to parse configuration override "),
+        # Unmatches parentheses
+        (['key={a=1, b="two"'], r"Unable to parse configuration override "),
+        # Valid value followed by invalid
+        (["good=42", "key=foobar"], r"Unable to parse configuration override "),
+        # Space in the key.
+        (["spacy key=42"], r"Unable to parse configuration override "),
+        # Multi-level key. This is legal TOML, but difficult to merge.
+        (["multi.level.key=42"], r"Can't override multi-level configuration keys\."),
+        # Key that can't be overridden
+        (["app_name='foobar'"], r"The app name cannot be overridden\."),
+    ],
+)
+def test_invalid_overrides(overrides, message):
+    with pytest.raises(BriefcaseConfigError, match=message):
+        parse_config_overrides(overrides)
diff --git a/tests/commands/base/test_parse_options.py b/tests/commands/base/test_parse_options.py
index 684e59dd1..326d41049 100644
--- a/tests/commands/base/test_parse_options.py
+++ b/tests/commands/base/test_parse_options.py
@@ -3,15 +3,51 @@
 from briefcase.console import LogLevel
 
 
-def test_parse_options(base_command):
-    """Command line options are parsed if provided."""
-    options = base_command.parse_options(extra=("-x", "wibble", "-r", "important"))
+def test_parse_options_no_overrides(base_command):
+    """Command line options are parsed if provided without overrides."""
+    options, overrides = base_command.parse_options(
+        extra=(
+            "-x",
+            "wibble",
+            "-r",
+            "important",
+        )
+    )
 
     assert options == {
         "extra": "wibble",
         "mystery": None,
         "required": "important",
     }
+    assert overrides == {}
+    assert base_command.input.enabled
+    assert base_command.logger.verbosity == LogLevel.INFO
+
+
+def test_parse_options_with_overrides(base_command):
+    """Command line options and overrides are parsed if provided."""
+    options, overrides = base_command.parse_options(
+        extra=(
+            "-x",
+            "wibble",
+            "-r",
+            "important",
+            "-C",
+            "width=10",
+            "-C",
+            "height=20",
+        )
+    )
+
+    assert options == {
+        "extra": "wibble",
+        "mystery": None,
+        "required": "important",
+    }
+    assert overrides == {
+        "width": 10,
+        "height": 20,
+    }
     assert base_command.input.enabled
     assert base_command.logger.verbosity == LogLevel.INFO
 
diff --git a/tests/commands/build/test_call.py b/tests/commands/build/test_call.py
index 826afb250..3a5caa040 100644
--- a/tests/commands/build/test_call.py
+++ b/tests/commands/build/test_call.py
@@ -12,7 +12,7 @@ def test_specific_app(build_command, first_app, second_app):
     }
 
     # Configure no command line options
-    options = build_command.parse_options([])
+    options, _ = build_command.parse_options([])
 
     # Run the build command
     build_command(first_app, **options)
@@ -43,7 +43,7 @@ def test_multiple_apps(build_command, first_app, second_app):
     }
 
     # Configure no command line options
-    options = build_command.parse_options([])
+    options, _ = build_command.parse_options([])
 
     # Run the build command
     build_command(**options)
@@ -81,7 +81,7 @@ def test_non_existent(build_command, first_app_config, second_app):
     }
 
     # Configure no command line options
-    options = build_command.parse_options([])
+    options, _ = build_command.parse_options([])
 
     # Run the build command
     build_command(**options)
@@ -125,7 +125,7 @@ def test_unbuilt(build_command, first_app_unbuilt, second_app):
     }
 
     # Configure no command line options
-    options = build_command.parse_options([])
+    options, _ = build_command.parse_options([])
 
     # Run the build command
     build_command(**options)
@@ -163,7 +163,7 @@ def test_update_app(build_command, first_app, second_app):
     }
 
     # Configure a -a command line option
-    options = build_command.parse_options(["-u"])
+    options, _ = build_command.parse_options(["-u"])
 
     # Run the build command
     build_command(**options)
@@ -227,7 +227,7 @@ def test_update_app_requirements(build_command, first_app, second_app):
     }
 
     # Configure update command line options
-    options = build_command.parse_options(["-r"])
+    options, _ = build_command.parse_options(["-r"])
 
     # Run the build command
     build_command(**options)
@@ -291,7 +291,7 @@ def test_update_app_resources(build_command, first_app, second_app):
     }
 
     # Configure update command line options
-    options = build_command.parse_options(["--update-resources"])
+    options, _ = build_command.parse_options(["--update-resources"])
 
     # Run the build command
     build_command(**options)
@@ -355,7 +355,7 @@ def test_update_non_existent(build_command, first_app_config, second_app):
     }
 
     # Configure no command line options
-    options = build_command.parse_options(["-u"])
+    options, _ = build_command.parse_options(["-u"])
 
     # Run the build command
     build_command(**options)
@@ -415,7 +415,7 @@ def test_update_unbuilt(build_command, first_app_unbuilt, second_app):
     }
 
     # Configure no command line options
-    options = build_command.parse_options(["-u"])
+    options, _ = build_command.parse_options(["-u"])
 
     # Run the build command
     build_command(**options)
@@ -479,7 +479,7 @@ def test_build_test(build_command, first_app, second_app):
     }
 
     # Configure command line options
-    options = build_command.parse_options(["--test"])
+    options, _ = build_command.parse_options(["--test"])
 
     # Run the build command
     build_command(**options)
@@ -544,7 +544,7 @@ def test_build_test_no_update(build_command, first_app, second_app):
     }
 
     # Configure command line options
-    options = build_command.parse_options(["--test", "--no-update"])
+    options, _ = build_command.parse_options(["--test", "--no-update"])
 
     # Run the build command
     build_command(**options)
@@ -587,7 +587,7 @@ def test_build_test_update_dependencies(build_command, first_app, second_app):
     }
 
     # Configure command line options
-    options = build_command.parse_options(["--test", "-r"])
+    options, _ = build_command.parse_options(["--test", "-r"])
 
     # Run the build command
     build_command(**options)
@@ -652,7 +652,7 @@ def test_build_test_update_resources(build_command, first_app, second_app):
     }
 
     # Configure command line options
-    options = build_command.parse_options(["--test", "--update-resources"])
+    options, _ = build_command.parse_options(["--test", "--update-resources"])
 
     # Run the build command
     build_command(**options)
@@ -716,7 +716,7 @@ def test_build_invalid_update(build_command, first_app, second_app):
     }
 
     # Configure command line options
-    options = build_command.parse_options(["-u", "--no-update"])
+    options, _ = build_command.parse_options(["-u", "--no-update"])
 
     # Run the build command
     with pytest.raises(
@@ -736,7 +736,7 @@ def test_build_invalid_update_requirements(build_command, first_app, second_app)
     }
 
     # Configure command line options
-    options = build_command.parse_options(["-r", "--no-update"])
+    options, _ = build_command.parse_options(["-r", "--no-update"])
 
     # Run the build command
     with pytest.raises(
@@ -756,7 +756,7 @@ def test_build_invalid_update_resources(build_command, first_app, second_app):
     }
 
     # Configure command line options
-    options = build_command.parse_options(["--update-resources", "--no-update"])
+    options, _ = build_command.parse_options(["--update-resources", "--no-update"])
 
     # Run the build command
     with pytest.raises(
@@ -776,7 +776,7 @@ def test_build_invalid_update_support(build_command, first_app, second_app):
     }
 
     # Configure command line options
-    options = build_command.parse_options(["--update-support", "--no-update"])
+    options, _ = build_command.parse_options(["--update-support", "--no-update"])
 
     # Run the build command
     with pytest.raises(
@@ -795,7 +795,7 @@ def test_test_app_non_existent(build_command, first_app_config, second_app):
     }
 
     # Configure command line options
-    options = build_command.parse_options(["-u", "--test"])
+    options, _ = build_command.parse_options(["-u", "--test"])
 
     # Run the build command
     build_command(**options)
@@ -856,7 +856,7 @@ def test_test_app_unbuilt(build_command, first_app_unbuilt, second_app):
     }
 
     # Configure command line options
-    options = build_command.parse_options(["-u", "--test"])
+    options, _ = build_command.parse_options(["-u", "--test"])
 
     # Run the build command
     build_command(**options)
diff --git a/tests/commands/dev/test_call.py b/tests/commands/dev/test_call.py
index 075122a0a..3b1293c09 100644
--- a/tests/commands/dev/test_call.py
+++ b/tests/commands/dev/test_call.py
@@ -65,7 +65,7 @@ def test_no_args_one_app(dev_command, first_app):
     }
 
     # Configure no command line options
-    options = dev_command.parse_options([])
+    options, _ = dev_command.parse_options([])
 
     # Run the run command
     dev_command(**options)
@@ -94,7 +94,7 @@ def test_no_args_two_apps(dev_command, first_app, second_app):
     }
 
     # Configure no command line options
-    options = dev_command.parse_options([])
+    options, _ = dev_command.parse_options([])
 
     # Invoking the run command raises an error
     with pytest.raises(BriefcaseCommandError):
@@ -112,7 +112,7 @@ def test_with_arg_one_app(dev_command, first_app):
     }
 
     # Configure a -a command line option
-    options = dev_command.parse_options(["-a", "first"])
+    options, _ = dev_command.parse_options(["-a", "first"])
 
     # Run the run command
     dev_command(**options)
@@ -141,7 +141,7 @@ def test_with_arg_two_apps(dev_command, first_app, second_app):
     }
 
     # Configure a --app command line option
-    options = dev_command.parse_options(["--app", "second"])
+    options, _ = dev_command.parse_options(["--app", "second"])
 
     # Run the run command
     dev_command(**options)
@@ -171,7 +171,7 @@ def test_bad_app_reference(dev_command, first_app, second_app):
     }
 
     # Configure a --app command line option
-    options = dev_command.parse_options(["--app", "does-not-exist"])
+    options, _ = dev_command.parse_options(["--app", "does-not-exist"])
 
     # Invoking the run command raises an error
     with pytest.raises(BriefcaseCommandError):
@@ -189,7 +189,7 @@ def test_update_requirements(dev_command, first_app):
     }
 
     # Configure a requirements update
-    options = dev_command.parse_options(["-r"])
+    options, _ = dev_command.parse_options(["-r"])
 
     # Run the run command
     dev_command(**options)
@@ -219,7 +219,7 @@ def test_run_uninstalled(dev_command, first_app_uninstalled):
     }
 
     # Configure no command line options
-    options = dev_command.parse_options([])
+    options, _ = dev_command.parse_options([])
 
     # Run the run command
     dev_command(**options)
@@ -250,7 +250,7 @@ def test_update_uninstalled(dev_command, first_app_uninstalled):
     }
 
     # Configure a requirements update
-    options = dev_command.parse_options(["-r"])
+    options, _ = dev_command.parse_options(["-r"])
 
     # Run the run command
     dev_command(**options)
@@ -280,7 +280,7 @@ def test_no_run(dev_command, first_app_uninstalled):
     }
 
     # Configure an update without run
-    options = dev_command.parse_options(["--no-run"])
+    options, _ = dev_command.parse_options(["--no-run"])
 
     # Run the run command
     dev_command(**options)
@@ -308,7 +308,7 @@ def test_run_test(dev_command, first_app):
     }
 
     # Configure the test option
-    options = dev_command.parse_options(["--test"])
+    options, _ = dev_command.parse_options(["--test"])
 
     # Run the run command
     dev_command(**options)
@@ -336,7 +336,7 @@ def test_run_test_uninstalled(dev_command, first_app_uninstalled):
     }
 
     # Configure the test option
-    options = dev_command.parse_options(["--test"])
+    options, _ = dev_command.parse_options(["--test"])
 
     # Run the run command
     dev_command(**options)
diff --git a/tests/commands/new/test_call.py b/tests/commands/new/test_call.py
index 8e3e1890c..04648626e 100644
--- a/tests/commands/new/test_call.py
+++ b/tests/commands/new/test_call.py
@@ -21,14 +21,14 @@ def monkeypatch_verify_git(*a, **kw):
 
 def test_parse_config(new_command):
     """Attempting to parse the config is a no-op when invoking new."""
-    assert new_command.parse_config("some_file.toml") is None
+    assert new_command.parse_config("some_file.toml", {}) is None
 
 
 def test_new_app(new_command):
     """A new application can be created."""
 
     # Configure no command line options
-    options = new_command.parse_options([])
+    options, _ = new_command.parse_options([])
 
     # Run the run command
     new_command(**options)
diff --git a/tests/commands/open/test_call.py b/tests/commands/open/test_call.py
index ce6f3c404..ed500e601 100644
--- a/tests/commands/open/test_call.py
+++ b/tests/commands/open/test_call.py
@@ -1,7 +1,7 @@
 def test_open(open_command, first_app, second_app):
     """The open command can be called."""
     # Configure no command line options
-    options = open_command.parse_options([])
+    options, _ = open_command.parse_options([])
 
     open_command(**options)
 
@@ -32,7 +32,7 @@ def test_open(open_command, first_app, second_app):
 def test_open_single(open_command, first_app):
     """The open command can be called to open a single app from the config."""
     # Configure no command line options
-    options = open_command.parse_options([])
+    options, _ = open_command.parse_options([])
 
     open_command(app=open_command.apps["first"], **options)
 
@@ -56,7 +56,7 @@ def test_open_single(open_command, first_app):
 def test_create_before_open(open_command, tmp_path):
     """If the app doesn't exist, it will be created before opening."""
     # Configure no command line options
-    options = open_command.parse_options([])
+    options, _ = open_command.parse_options([])
 
     open_command(app=open_command.apps["first"], **options)
 
diff --git a/tests/commands/package/test_call.py b/tests/commands/package/test_call.py
index 096236dce..a4a1d10a3 100644
--- a/tests/commands/package/test_call.py
+++ b/tests/commands/package/test_call.py
@@ -9,7 +9,7 @@ def test_no_args_package_one_app(package_command, first_app, tmp_path):
     }
 
     # Configure no command line options
-    options = package_command.parse_options([])
+    options, _ = package_command.parse_options([])
 
     # Run the run command
     package_command(**options)
@@ -53,7 +53,7 @@ def test_package_one_explicit_app(package_command, first_app, second_app, tmp_pa
     }
 
     # Configure no command line arguments
-    options = package_command.parse_options([])
+    options, _ = package_command.parse_options([])
 
     # Run the build command on a specific app
     package_command(first_app, **options)
@@ -98,7 +98,7 @@ def test_no_args_package_two_app(package_command, first_app, second_app, tmp_pat
     }
 
     # Configure no command line options
-    options = package_command.parse_options([])
+    options, _ = package_command.parse_options([])
 
     # Run the package command
     package_command(**options)
@@ -159,7 +159,7 @@ def test_identity_arg_package_one_app(package_command, first_app, tmp_path):
     }
 
     # Configure an identity option
-    options = package_command.parse_options(["--identity", "test"])
+    options, _ = package_command.parse_options(["--identity", "test"])
 
     # Run the run command
     package_command(**options)
@@ -203,7 +203,7 @@ def test_adhoc_sign_package_one_app(package_command, first_app, tmp_path):
     }
 
     # Configure an ad-hoc signing option
-    options = package_command.parse_options(["--adhoc-sign"])
+    options, _ = package_command.parse_options(["--adhoc-sign"])
 
     # Run the run command
     package_command(**options)
@@ -252,7 +252,7 @@ def test_adhoc_sign_args_package_two_app(
     }
 
     # Configure adhoc command line options
-    options = package_command.parse_options(["--adhoc-sign"])
+    options, _ = package_command.parse_options(["--adhoc-sign"])
 
     # Run the package command
     package_command(**options)
@@ -316,7 +316,7 @@ def test_identity_sign_args_package_two_app(
     }
 
     # Configure an identity option
-    options = package_command.parse_options(["--identity", "test"])
+    options, _ = package_command.parse_options(["--identity", "test"])
 
     # Run the run command
     package_command(**options)
@@ -376,7 +376,7 @@ def test_package_alternate_format(package_command, first_app, tmp_path):
     }
 
     # Configure command line options with an alternate format
-    options = package_command.parse_options(["--packaging-format", "box"])
+    options, _ = package_command.parse_options(["--packaging-format", "box"])
 
     # Run the run command
     package_command(**options)
@@ -419,7 +419,7 @@ def test_create_before_package(package_command, first_app_config, tmp_path):
     }
 
     # Configure no command line options
-    options = package_command.parse_options([])
+    options, _ = package_command.parse_options([])
 
     # Run the run command
     package_command(**options)
@@ -482,7 +482,7 @@ def test_update_package_one_app(package_command, first_app, tmp_path):
     }
 
     # Configure an update option
-    options = package_command.parse_options(["-u"])
+    options, _ = package_command.parse_options(["-u"])
 
     # Run the run command
     package_command(**options)
@@ -549,7 +549,7 @@ def test_update_package_two_app(package_command, first_app, second_app, tmp_path
     }
 
     # Configure an update option
-    options = package_command.parse_options(["--update"])
+    options, _ = package_command.parse_options(["--update"])
 
     # Run the package command
     package_command(**options)
@@ -662,7 +662,7 @@ def test_build_before_package(package_command, first_app_unbuilt, tmp_path):
     }
 
     # Configure no command line options
-    options = package_command.parse_options([])
+    options, _ = package_command.parse_options([])
 
     # Run the run command
     package_command(**options)
@@ -719,7 +719,7 @@ def test_already_packaged(package_command, first_app, tmp_path):
     create_file(artefact_path, "Packaged app")
 
     # Configure no command line options
-    options = package_command.parse_options([])
+    options, _ = package_command.parse_options([])
 
     # Run the run command
     package_command(**options)
diff --git a/tests/commands/publish/test_call.py b/tests/commands/publish/test_call.py
index 59b271833..4b5544388 100644
--- a/tests/commands/publish/test_call.py
+++ b/tests/commands/publish/test_call.py
@@ -12,7 +12,7 @@ def test_publish(publish_command, first_app, second_app):
     }
 
     # Configure no command line options
-    options = publish_command.parse_options([])
+    options, _ = publish_command.parse_options([])
 
     # Run the publish command
     publish_command(**options)
@@ -50,7 +50,7 @@ def test_publish_alternative_channel(publish_command, first_app, second_app):
     }
 
     # Configure no command line options
-    options = publish_command.parse_options(["-c", "alternative"])
+    options, _ = publish_command.parse_options(["-c", "alternative"])
 
     # Run the publish command
     publish_command(**options)
@@ -88,7 +88,7 @@ def test_non_existent(publish_command, first_app_config, second_app):
     }
 
     # Configure no command line options
-    options = publish_command.parse_options([])
+    options, _ = publish_command.parse_options([])
 
     # Invoking the publish command raises an error
     with pytest.raises(BriefcaseCommandError):
@@ -116,7 +116,7 @@ def test_unbuilt(publish_command, first_app_unbuilt, second_app):
     }
 
     # Configure no command line options
-    options = publish_command.parse_options([])
+    options, _ = publish_command.parse_options([])
 
     # Invoking the publish command raises an error
     with pytest.raises(BriefcaseCommandError):
diff --git a/tests/commands/run/test_call.py b/tests/commands/run/test_call.py
index 6145f9f78..899bdb611 100644
--- a/tests/commands/run/test_call.py
+++ b/tests/commands/run/test_call.py
@@ -11,7 +11,7 @@ def test_no_args_one_app(run_command, first_app):
     }
 
     # Configure no command line options
-    options = run_command.parse_options([])
+    options, _ = run_command.parse_options([])
 
     # Run the run command
     run_command(**options)
@@ -42,7 +42,7 @@ def test_no_args_one_app_with_passthrough(run_command, first_app):
     }
 
     # Configure no command line options
-    options = run_command.parse_options(["--", "foo", "--bar"])
+    options, _ = run_command.parse_options(["--", "foo", "--bar"])
 
     # Run the run command
     run_command(**options)
@@ -73,7 +73,7 @@ def test_no_args_two_apps(run_command, first_app, second_app):
     }
 
     # Configure no command line options
-    options = run_command.parse_options([])
+    options, _ = run_command.parse_options([])
 
     # Invoking the run command raises an error
     with pytest.raises(BriefcaseCommandError):
@@ -91,7 +91,7 @@ def test_with_arg_one_app(run_command, first_app):
     }
 
     # Configure a -a command line option
-    options = run_command.parse_options(["-a", "first"])
+    options, _ = run_command.parse_options(["-a", "first"])
 
     # Run the run command
     run_command(**options)
@@ -122,7 +122,7 @@ def test_with_arg_two_apps(run_command, first_app, second_app):
     }
 
     # Configure a --app command line option
-    options = run_command.parse_options(["--app", "second"])
+    options, _ = run_command.parse_options(["--app", "second"])
 
     # Run the run command
     run_command(**options)
@@ -154,7 +154,7 @@ def test_bad_app_reference(run_command, first_app, second_app):
     }
 
     # Configure a --app command line option
-    options = run_command.parse_options(["--app", "does-not-exist"])
+    options, _ = run_command.parse_options(["--app", "does-not-exist"])
 
     # Invoking the run command raises an error
     with pytest.raises(BriefcaseCommandError):
@@ -172,7 +172,7 @@ def test_create_app_before_start(run_command, first_app_config):
     }
 
     # Configure no command line options
-    options = run_command.parse_options([])
+    options, _ = run_command.parse_options([])
 
     # Run the run command
     run_command(**options)
@@ -220,7 +220,7 @@ def test_build_app_before_start(run_command, first_app_unbuilt):
     }
 
     # Configure no command line options
-    options = run_command.parse_options([])
+    options, _ = run_command.parse_options([])
 
     # Run the run command
     run_command(**options)
@@ -267,7 +267,7 @@ def test_update_app(run_command, first_app):
     }
 
     # Configure an update option
-    options = run_command.parse_options(["-u"])
+    options, _ = run_command.parse_options(["-u"])
 
     # Run the run command
     run_command(**options)
@@ -314,7 +314,7 @@ def test_update_app_requirements(run_command, first_app):
     }
 
     # Configure an update option
-    options = run_command.parse_options(["-r"])
+    options, _ = run_command.parse_options(["-r"])
 
     # Run the run command
     run_command(**options)
@@ -361,7 +361,7 @@ def test_update_app_resources(run_command, first_app):
     }
 
     # Configure an update option
-    options = run_command.parse_options(["--update-resources"])
+    options, _ = run_command.parse_options(["--update-resources"])
 
     # Run the run command
     run_command(**options)
@@ -408,7 +408,7 @@ def test_update_unbuilt_app(run_command, first_app_unbuilt):
     }
 
     # Configure an update option
-    options = run_command.parse_options(["-u"])
+    options, _ = run_command.parse_options(["-u"])
 
     # Run the run command
     run_command(**options)
@@ -456,7 +456,7 @@ def test_update_non_existent(run_command, first_app_config):
     }
 
     # Configure an update option
-    options = run_command.parse_options(["-u"])
+    options, _ = run_command.parse_options(["-u"])
 
     # Run the run command
     run_command(**options)
@@ -504,7 +504,7 @@ def test_test_mode_existing_app(run_command, first_app):
     }
 
     # Configure the test option
-    options = run_command.parse_options(["--test"])
+    options, _ = run_command.parse_options(["--test"])
 
     # Run the run command
     run_command(**options)
@@ -551,7 +551,7 @@ def test_test_mode_existing_app_with_passthrough(run_command, first_app):
     }
 
     # Configure the test option
-    options = run_command.parse_options(["--test", "--", "foo", "--bar"])
+    options, _ = run_command.parse_options(["--test", "--", "foo", "--bar"])
 
     # Run the run command
     run_command(**options)
@@ -602,7 +602,7 @@ def test_test_mode_existing_app_no_update(run_command, first_app):
     }
 
     # Configure the test option
-    options = run_command.parse_options(["--test", "--no-update"])
+    options, _ = run_command.parse_options(["--test", "--no-update"])
 
     # Run the run command
     run_command(**options)
@@ -637,7 +637,7 @@ def test_test_mode_existing_app_update_requirements(run_command, first_app):
     }
 
     # Configure the test option
-    options = run_command.parse_options(["--test", "--update-requirements"])
+    options, _ = run_command.parse_options(["--test", "--update-requirements"])
 
     # Run the run command
     run_command(**options)
@@ -684,7 +684,7 @@ def test_test_mode_existing_app_update_resources(run_command, first_app):
     }
 
     # Configure the test option
-    options = run_command.parse_options(["--test", "--update-resources"])
+    options, _ = run_command.parse_options(["--test", "--update-resources"])
 
     # Run the run command
     run_command(**options)
@@ -731,7 +731,7 @@ def test_test_mode_update_existing_app(run_command, first_app):
     }
 
     # Configure the test option
-    options = run_command.parse_options(["-u", "--test"])
+    options, _ = run_command.parse_options(["-u", "--test"])
 
     # Run the run command
     run_command(**options)
@@ -778,7 +778,7 @@ def test_test_mode_non_existent(run_command, first_app_config):
     }
 
     # Configure a test option
-    options = run_command.parse_options(["--test"])
+    options, _ = run_command.parse_options(["--test"])
 
     # Run the run command
     run_command(**options)
diff --git a/tests/commands/update/test_call.py b/tests/commands/update/test_call.py
index cd48396e5..2ca085fc5 100644
--- a/tests/commands/update/test_call.py
+++ b/tests/commands/update/test_call.py
@@ -22,7 +22,7 @@ def monkeypatch_verify_git(*a, **kw):
 def test_update(update_command, first_app, second_app):
     """The update command can be called."""
     # Configure no command line options
-    options = update_command.parse_options([])
+    options, _ = update_command.parse_options([])
 
     update_command(**options)
 
@@ -51,7 +51,7 @@ def test_update(update_command, first_app, second_app):
 def test_update_single(update_command, first_app, second_app):
     """The update command can be called to update a single app from the config."""
     # Configure no command line options
-    options = update_command.parse_options([])
+    options, _ = update_command.parse_options([])
 
     update_command(app=update_command.apps["first"], **options)
 
@@ -74,7 +74,7 @@ def test_update_single(update_command, first_app, second_app):
 def test_update_with_requirements(update_command, first_app, second_app):
     """The update command can be called, requesting a requirements update."""
     # Configure a requirements update
-    options = update_command.parse_options(["-r"])
+    options, _ = update_command.parse_options(["-r"])
 
     update_command(**options)
 
@@ -105,7 +105,7 @@ def test_update_with_requirements(update_command, first_app, second_app):
 def test_update_with_resources(update_command, first_app, second_app):
     """The update command can be called, requesting a resources update."""
     # Configure no command line options
-    options = update_command.parse_options(["--update-resources"])
+    options, _ = update_command.parse_options(["--update-resources"])
 
     update_command(**options)
 
@@ -136,7 +136,7 @@ def test_update_with_resources(update_command, first_app, second_app):
 def test_update_with_support(update_command, first_app, second_app):
     """The update command can be called, requesting an app support update."""
     # Configure no command line options
-    options = update_command.parse_options(["--update-support"])
+    options, _ = update_command.parse_options(["--update-support"])
 
     update_command(**options)
 
diff --git a/tests/platforms/android/gradle/test_run.py b/tests/platforms/android/gradle/test_run.py
index 3549bbcfd..3db1db2ed 100644
--- a/tests/platforms/android/gradle/test_run.py
+++ b/tests/platforms/android/gradle/test_run.py
@@ -80,7 +80,7 @@ def test_binary_path(run_command, first_app_config, tmp_path):
 
 def test_device_option(run_command):
     """The -d option can be parsed."""
-    options = run_command.parse_options(["-d", "myphone"])
+    options, overrides = run_command.parse_options(["-d", "myphone"])
 
     assert options == {
         "device_or_avd": "myphone",
@@ -95,11 +95,12 @@ def test_device_option(run_command):
         "extra_emulator_args": None,
         "shutdown_on_exit": False,
     }
+    assert overrides == {}
 
 
 def test_extra_emulator_args_option(run_command):
     """The -d option can be parsed."""
-    options = run_command.parse_options(
+    options, overrides = run_command.parse_options(
         ["--Xemulator=-no-window", "--Xemulator=-no-audio"]
     )
 
@@ -116,11 +117,12 @@ def test_extra_emulator_args_option(run_command):
         "extra_emulator_args": ["-no-window", "-no-audio"],
         "shutdown_on_exit": False,
     }
+    assert overrides == {}
 
 
 def test_shutdown_on_exit_option(run_command):
     """The -d option can be parsed."""
-    options = run_command.parse_options(["--shutdown-on-exit"])
+    options, overrides = run_command.parse_options(["--shutdown-on-exit"])
 
     assert options == {
         "device_or_avd": None,
@@ -135,6 +137,7 @@ def test_shutdown_on_exit_option(run_command):
         "extra_emulator_args": None,
         "shutdown_on_exit": True,
     }
+    assert overrides == {}
 
 
 def test_unsupported_template_version(run_command, first_app_generated):
diff --git a/tests/platforms/iOS/xcode/test_run.py b/tests/platforms/iOS/xcode/test_run.py
index 6f858af10..bb7896760 100644
--- a/tests/platforms/iOS/xcode/test_run.py
+++ b/tests/platforms/iOS/xcode/test_run.py
@@ -39,7 +39,7 @@ def mock_stream_app_logs(app, stop_func, **kwargs):
 
 def test_device_option(run_command):
     """The -d option can be parsed."""
-    options = run_command.parse_options(["-d", "myphone"])
+    options, overrides = run_command.parse_options(["-d", "myphone"])
 
     assert options == {
         "udid": "myphone",
@@ -52,6 +52,7 @@ def test_device_option(run_command):
         "passthrough": [],
         "appname": None,
     }
+    assert overrides == {}
 
 
 def test_run_multiple_devices_input_disabled(run_command, first_app_config):
diff --git a/tests/platforms/linux/appimage/test_create.py b/tests/platforms/linux/appimage/test_create.py
index 62674398c..0ab0bd169 100644
--- a/tests/platforms/linux/appimage/test_create.py
+++ b/tests/platforms/linux/appimage/test_create.py
@@ -21,18 +21,20 @@ def create_command(first_app_config, tmp_path):
 
 def test_default_options(create_command):
     """The default options are as expected."""
-    options = create_command.parse_options([])
+    options, overrides = create_command.parse_options([])
 
     assert options == {}
+    assert overrides == {}
 
     assert create_command.use_docker
 
 
 def test_options(create_command):
     """The extra options can be parsed."""
-    options = create_command.parse_options(["--no-docker"])
+    options, overrides = create_command.parse_options(["--no-docker"])
 
     assert options == {}
+    assert overrides == {}
 
     assert not create_command.use_docker
 
diff --git a/tests/platforms/linux/system/test_create.py b/tests/platforms/linux/system/test_create.py
index 2039dcaed..12a212a7d 100644
--- a/tests/platforms/linux/system/test_create.py
+++ b/tests/platforms/linux/system/test_create.py
@@ -7,18 +7,22 @@
 
 def test_default_options(create_command):
     """The default options are as expected."""
-    options = create_command.parse_options([])
+    options, overrides = create_command.parse_options([])
 
     assert options == {}
+    assert overrides == {}
 
     assert create_command.target_image is None
 
 
 def test_options(create_command):
     """The extra options can be parsed."""
-    options = create_command.parse_options(["--target", "somevendor:surprising"])
+    options, overrides = create_command.parse_options(
+        ["--target", "somevendor:surprising"]
+    )
 
     assert options == {}
+    assert overrides == {}
 
     assert create_command.target_image == "somevendor:surprising"
 
diff --git a/tests/platforms/macOS/app/test_package.py b/tests/platforms/macOS/app/test_package.py
index 93dda82fa..fbc158ed7 100644
--- a/tests/platforms/macOS/app/test_package.py
+++ b/tests/platforms/macOS/app/test_package.py
@@ -38,7 +38,7 @@ def test_package_formats(package_command):
 
 def test_device_option(package_command):
     """The -d option can be parsed."""
-    options = package_command.parse_options(["--no-notarize"])
+    options, overrides = package_command.parse_options(["--no-notarize"])
 
     assert options == {
         "adhoc_sign": False,
@@ -47,6 +47,7 @@ def test_device_option(package_command):
         "packaging_format": "dmg",
         "update": False,
     }
+    assert overrides == {}
 
 
 def test_package_app(package_command, first_app_with_binaries, tmp_path, capsys):
diff --git a/tests/platforms/web/static/test_run.py b/tests/platforms/web/static/test_run.py
index 04e54f1db..dea04baa5 100644
--- a/tests/platforms/web/static/test_run.py
+++ b/tests/platforms/web/static/test_run.py
@@ -28,7 +28,7 @@ def run_command(tmp_path):
 
 def test_default_options(run_command):
     """The default options are as expected."""
-    options = run_command.parse_options([])
+    options, overrides = run_command.parse_options([])
 
     assert options == {
         "appname": None,
@@ -43,11 +43,12 @@ def test_default_options(run_command):
         "port": 8080,
         "open_browser": True,
     }
+    assert overrides == {}
 
 
 def test_options(run_command):
     """The extra options can be parsed."""
-    options = run_command.parse_options(
+    options, overrides = run_command.parse_options(
         ["--host", "myhost", "--port", "1234", "--no-browser"]
     )
 
@@ -64,6 +65,7 @@ def test_options(run_command):
         "port": 1234,
         "open_browser": False,
     }
+    assert overrides == {}
 
 
 def test_run(monkeypatch, run_command, first_app_built):
diff --git a/tests/platforms/windows/app/test_package.py b/tests/platforms/windows/app/test_package.py
index eb9d99d62..28d30d9a6 100644
--- a/tests/platforms/windows/app/test_package.py
+++ b/tests/platforms/windows/app/test_package.py
@@ -190,9 +190,10 @@ def test_parse_options(package_command, cli_args, signing_options, is_sdk_needed
     )
     expected_options = {**default_options, **signing_options}
 
-    options = package_command.parse_options(extra=cli_args)
+    options, overrides = package_command.parse_options(extra=cli_args)
 
     assert options == expected_options
+    assert overrides == {}
     assert package_command._windows_sdk_needed is is_sdk_needed
 
 
diff --git a/tests/test_cmdline.py b/tests/test_cmdline.py
index 1ed6df5ef..db61cbcb9 100644
--- a/tests/test_cmdline.py
+++ b/tests/test_cmdline.py
@@ -35,8 +35,8 @@ def do_cmdline_parse(args: list, logger: Log, console: Console):
     """Simulate process to parse command line."""
     Command, extra_cmdline = cmdline.parse_cmdline(args)
     cmd = Command(logger=logger, console=console)
-    options = cmd.parse_options(extra=extra_cmdline)
-    return cmd, options
+    options, overrides = cmd.parse_options(extra=extra_cmdline)
+    return cmd, options, overrides
 
 
 def test_empty():
@@ -93,9 +93,33 @@ def test_unknown_command():
     )
 
 
-def test_new_command(logger, console):
+@pytest.mark.parametrize(
+    "cmdline, expected_options, expected_overrides",
+    [
+        (
+            "new",
+            {
+                "template": None,
+                "template_branch": None,
+            },
+            {},
+        ),
+        (
+            "new --template=path/to/template --template-branch=experiment -C version=\\'1.2.3\\' -C other=42",
+            {
+                "template": "path/to/template",
+                "template_branch": "experiment",
+            },
+            {
+                "version": "1.2.3",
+                "other": 42,
+            },
+        ),
+    ],
+)
+def test_new_command(logger, console, cmdline, expected_options, expected_overrides):
     """``briefcase new`` returns the New command."""
-    cmd, options = do_cmdline_parse("new".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse(shlex.split(cmdline), logger, console)
 
     assert isinstance(cmd, NewCommand)
     assert cmd.platform == "all"
@@ -104,47 +128,68 @@ def test_new_command(logger, console):
     assert cmd.logger.verbosity == LogLevel.INFO
     assert cmd.logger is logger
     assert cmd.input is console
-    assert options == {"template": None, "template_branch": None}
+    assert options == expected_options
+    assert overrides == expected_overrides
 
 
 # Common tests for dev and run commands.
 def dev_run_parameters(command):
     return [
-        (f"{command} {args}", expected)
-        for args, expected in [
-            ("", {}),
-            ("-r", {"update_requirements": True}),
-            ("--update-requirements", {"update_requirements": True}),
-            ("--test", {"test_mode": True}),
-            ("--test -r", {"test_mode": True, "update_requirements": True}),
-            ("--", {}),
-            ("-- ''", {"passthrough": [""]}),
-            ("-- --test", {"passthrough": ["--test"]}),
-            ("--test -- --test", {"test_mode": True, "passthrough": ["--test"]}),
-            ("--test -- -r", {"test_mode": True, "passthrough": ["-r"]}),
-            ("-r -- --test", {"update_requirements": True, "passthrough": ["--test"]}),
-            ("-- -y --no maybe", {"passthrough": ["-y", "--no", "maybe"]}),
+        (f"{command} {args}", expected, overrides)
+        for args, expected, overrides in [
+            ("", {}, {}),
+            ("-r", {"update_requirements": True}, {}),
+            (
+                "-r -C version=\\'1.2.3\\' -C other=42",
+                {"update_requirements": True},
+                {
+                    "version": "1.2.3",
+                    "other": 42,
+                },
+            ),
+            ("--update-requirements", {"update_requirements": True}, {}),
+            ("--test", {"test_mode": True}, {}),
+            ("--test -r", {"test_mode": True, "update_requirements": True}, {}),
+            ("--", {}, {}),
+            ("-- ''", {"passthrough": [""]}, {}),
+            ("-- --test", {"passthrough": ["--test"]}, {}),
+            ("--test -- --test", {"test_mode": True, "passthrough": ["--test"]}, {}),
+            ("--test -- -r", {"test_mode": True, "passthrough": ["-r"]}, {}),
+            (
+                "-r -- --test",
+                {"update_requirements": True, "passthrough": ["--test"]},
+                {},
+            ),
+            ("-- -y --no maybe", {"passthrough": ["-y", "--no", "maybe"]}, {}),
             (
                 "--test -- -y --no maybe",
                 {"test_mode": True, "passthrough": ["-y", "--no", "maybe"]},
+                {},
             ),
         ]
     ]
 
 
 @pytest.mark.parametrize(
-    "cmdline, expected_options",
+    "cmdline, expected_options, expected_overrides",
     dev_run_parameters("dev")
     + [
-        ("dev --no-run", {"run_app": False}),
+        ("dev --no-run", {"run_app": False}, {}),
     ],
 )
-def test_dev_command(monkeypatch, logger, console, cmdline, expected_options):
+def test_dev_command(
+    monkeypatch,
+    logger,
+    console,
+    cmdline,
+    expected_options,
+    expected_overrides,
+):
     """``briefcase dev`` returns the Dev command."""
     # Pretend we're on macOS, regardless of where the tests run.
     monkeypatch.setattr(sys, "platform", "darwin")
 
-    cmd, options = do_cmdline_parse(shlex.split(cmdline), logger, console)
+    cmd, options, overrides = do_cmdline_parse(shlex.split(cmdline), logger, console)
 
     assert isinstance(cmd, DevCommand)
     assert cmd.platform == "macOS"
@@ -161,25 +206,33 @@ def test_dev_command(monkeypatch, logger, console, cmdline, expected_options):
         "passthrough": [],
         **expected_options,
     }
+    assert overrides == expected_overrides
 
 
 @pytest.mark.parametrize(
-    "cmdline, expected_options",
+    "cmdline, expected_options, expected_overrides",
     dev_run_parameters("run")
     + [
-        ("run -u", {"update": True}),
-        ("run --update", {"update": True}),
-        ("run --update-resources", {"update_resources": True}),
-        ("run --update-support", {"update_support": True}),
-        ("run --no-update", {"no_update": True}),
+        ("run -u", {"update": True}, {}),
+        ("run --update", {"update": True}, {}),
+        ("run --update-resources", {"update_resources": True}, {}),
+        ("run --update-support", {"update_support": True}, {}),
+        ("run --no-update", {"no_update": True}, {}),
     ],
 )
-def test_run_command(monkeypatch, logger, console, cmdline, expected_options):
+def test_run_command(
+    monkeypatch,
+    logger,
+    console,
+    cmdline,
+    expected_options,
+    expected_overrides,
+):
     """``briefcase run`` returns the Run command for the correct platform."""
     # Pretend we're on macOS, regardless of where the tests run.
     monkeypatch.setattr(sys, "platform", "darwin")
 
-    cmd, options = do_cmdline_parse(shlex.split(cmdline), logger, console)
+    cmd, options, overrides = do_cmdline_parse(shlex.split(cmdline), logger, console)
 
     assert isinstance(cmd, macOSAppRunCommand)
     assert cmd.platform == "macOS"
@@ -199,14 +252,46 @@ def test_run_command(monkeypatch, logger, console, cmdline, expected_options):
         "passthrough": [],
         **expected_options,
     }
+    assert overrides == expected_overrides
 
 
-def test_upgrade_command(monkeypatch, logger, console):
+@pytest.mark.parametrize(
+    "cmdline,expected_options,expected_overrides",
+    [
+        (
+            "upgrade",
+            {
+                "list_tools": False,
+                "tool_list": [],
+            },
+            {},
+        ),
+        (
+            "upgrade -C version='1.2.3' -C other=42",
+            {
+                "list_tools": False,
+                "tool_list": [],
+            },
+            {
+                "version": "1.2.3",
+                "other": 42,
+            },
+        ),
+    ],
+)
+def test_upgrade_command(
+    monkeypatch,
+    logger,
+    console,
+    cmdline,
+    expected_options,
+    expected_overrides,
+):
     """``briefcase upgrade`` returns the upgrade command."""
     # Pretend we're on macOS, regardless of where the tests run.
     monkeypatch.setattr(sys, "platform", "darwin")
 
-    cmd, options = do_cmdline_parse("upgrade".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse(cmdline.split(), logger, console)
 
     assert isinstance(cmd, UpgradeCommand)
     assert cmd.platform == "macOS"
@@ -215,10 +300,8 @@ def test_upgrade_command(monkeypatch, logger, console):
     assert cmd.logger.verbosity == LogLevel.INFO
     assert cmd.logger is logger
     assert cmd.input is console
-    assert options == {
-        "list_tools": False,
-        "tool_list": [],
-    }
+    assert options == expected_options
+    assert overrides == expected_overrides
 
 
 def test_bare_command(monkeypatch, logger, console):
@@ -226,7 +309,7 @@ def test_bare_command(monkeypatch, logger, console):
     # Pretend we're on macOS, regardless of where the tests run.
     monkeypatch.setattr(sys, "platform", "darwin")
 
-    cmd, options = do_cmdline_parse("create".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse("create".split(), logger, console)
 
     assert isinstance(cmd, macOSAppCreateCommand)
     assert cmd.platform == "macOS"
@@ -236,13 +319,14 @@ def test_bare_command(monkeypatch, logger, console):
     assert cmd.logger is logger
     assert cmd.input is console
     assert options == {}
+    assert overrides == {}
 
 
 @pytest.mark.skipif(sys.platform != "linux", reason="requires Linux")
 def test_linux_default(logger, console):
     """``briefcase create`` returns the linux create system command on Linux."""
 
-    cmd, options = do_cmdline_parse("create".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse("create".split(), logger, console)
 
     assert isinstance(cmd, LinuxSystemCreateCommand)
     assert cmd.platform == "linux"
@@ -258,7 +342,7 @@ def test_linux_default(logger, console):
 def test_macOS_default(logger, console):
     """``briefcase create`` returns the macOS create command on Linux."""
 
-    cmd, options = do_cmdline_parse("create".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse("create".split(), logger, console)
 
     assert isinstance(cmd, macOSAppCreateCommand)
     assert cmd.platform == "macOS"
@@ -268,13 +352,14 @@ def test_macOS_default(logger, console):
     assert cmd.logger is logger
     assert cmd.input is console
     assert options == {}
+    assert overrides == {}
 
 
 @pytest.mark.skipif(sys.platform != "win32", reason="requires Windows")
 def test_windows_default(logger, console):
     """``briefcase create`` returns the Windows create app command on Windows."""
 
-    cmd, options = do_cmdline_parse("create".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse("create".split(), logger, console)
 
     assert isinstance(cmd, WindowsAppCreateCommand)
     assert cmd.platform == "windows"
@@ -284,6 +369,7 @@ def test_windows_default(logger, console):
     assert cmd.logger is logger
     assert cmd.input is console
     assert options == {}
+    assert overrides == {}
 
 
 def test_bare_command_help(monkeypatch, capsys, logger, console):
@@ -299,7 +385,8 @@ def test_bare_command_help(monkeypatch, capsys, logger, console):
     # Help message is for default platform and format
     output = capsys.readouterr().out
     assert output.startswith(
-        "usage: briefcase create macOS app [-h] [-v] [-V] [--no-input] [--log]\n"
+        "usage: briefcase create macOS app [-h] [-C KEY=VALUE] [-v] [-V] [--no-input]\n"
+        "                                  [--log]\n"
         "\n"
         "Create and populate a macOS app.\n"
     )
@@ -337,7 +424,7 @@ def test_command_explicit_platform(monkeypatch, logger, console):
     # Pretend we're on macOS, regardless of where the tests run.
     monkeypatch.setattr(sys, "platform", "darwin")
 
-    cmd, options = do_cmdline_parse("create linux".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse("create linux".split(), logger, console)
 
     assert isinstance(cmd, LinuxSystemCreateCommand)
     assert cmd.platform == "linux"
@@ -347,6 +434,7 @@ def test_command_explicit_platform(monkeypatch, logger, console):
     assert cmd.logger is logger
     assert cmd.input is console
     assert options == {}
+    assert overrides == {}
 
 
 def test_command_explicit_platform_case_handling(monkeypatch, logger, console):
@@ -355,7 +443,7 @@ def test_command_explicit_platform_case_handling(monkeypatch, logger, console):
     monkeypatch.setattr(sys, "platform", "darwin")
 
     # This is all lower case; the command normalizes to macOS
-    cmd, options = do_cmdline_parse("create macOS".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse("create macOS".split(), logger, console)
 
     assert isinstance(cmd, macOSAppCreateCommand)
     assert cmd.platform == "macOS"
@@ -365,6 +453,7 @@ def test_command_explicit_platform_case_handling(monkeypatch, logger, console):
     assert cmd.logger is logger
     assert cmd.input is console
     assert options == {}
+    assert overrides == {}
 
 
 def test_command_explicit_platform_help(monkeypatch, capsys, logger, console):
@@ -380,7 +469,8 @@ def test_command_explicit_platform_help(monkeypatch, capsys, logger, console):
     # Help message is for default platform and format
     output = capsys.readouterr().out
     assert output.startswith(
-        "usage: briefcase create macOS app [-h] [-v] [-V] [--no-input] [--log]\n"
+        "usage: briefcase create macOS app [-h] [-C KEY=VALUE] [-v] [-V] [--no-input]\n"
+        "                                  [--log]\n"
         "\n"
         "Create and populate a macOS app.\n"
     )
@@ -391,7 +481,9 @@ def test_command_explicit_format(monkeypatch, logger, console):
     # Pretend we're on macOS, regardless of where the tests run.
     monkeypatch.setattr(sys, "platform", "darwin")
 
-    cmd, options = do_cmdline_parse("create macOS app".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse(
+        "create macOS app".split(), logger, console
+    )
 
     assert isinstance(cmd, macOSAppCreateCommand)
     assert cmd.platform == "macOS"
@@ -401,6 +493,7 @@ def test_command_explicit_format(monkeypatch, logger, console):
     assert cmd.logger is logger
     assert cmd.input is console
     assert options == {}
+    assert overrides == {}
 
 
 def test_command_unknown_format(monkeypatch, logger, console):
@@ -446,7 +539,8 @@ def test_command_explicit_format_help(monkeypatch, capsys, logger, console):
     # Help message is for default platform, but app format
     output = capsys.readouterr().out
     assert output.startswith(
-        "usage: briefcase create macOS app [-h] [-v] [-V] [--no-input] [--log]\n"
+        "usage: briefcase create macOS app [-h] [-C KEY=VALUE] [-v] [-V] [--no-input]\n"
+        "                                  [--log]\n"
         "\n"
         "Create and populate a macOS app.\n"
     )
@@ -457,7 +551,9 @@ def test_command_disable_input(monkeypatch, logger, console):
     # Pretend we're on macOS, regardless of where the tests run.
     monkeypatch.setattr(sys, "platform", "darwin")
 
-    cmd, options = do_cmdline_parse("create --no-input".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse(
+        "create --no-input".split(), logger, console
+    )
 
     assert isinstance(cmd, macOSAppCreateCommand)
     assert cmd.platform == "macOS"
@@ -467,6 +563,7 @@ def test_command_disable_input(monkeypatch, logger, console):
     assert cmd.logger is logger
     assert cmd.input is console
     assert options == {}
+    assert overrides == {}
 
 
 def test_command_options(monkeypatch, capsys, logger, console):
@@ -476,7 +573,9 @@ def test_command_options(monkeypatch, capsys, logger, console):
 
     # Invoke a command that is known to have its own custom arguments
     # (In this case, the channel argument for publication)
-    cmd, options = do_cmdline_parse("publish macos app -c s3".split(), logger, console)
+    cmd, options, overrides = do_cmdline_parse(
+        "publish macos app -c s3".split(), logger, console
+    )
 
     assert isinstance(cmd, macOSAppPublishCommand)
     assert cmd.input.enabled
@@ -484,6 +583,32 @@ def test_command_options(monkeypatch, capsys, logger, console):
     assert cmd.logger is logger
     assert cmd.input is console
     assert options == {"channel": "s3"}
+    assert overrides == {}
+
+
+def test_command_overrides(monkeypatch, capsys, logger, console):
+    """Configuration overrides can be specified."""
+    # Pretend we're on macOS, regardless of where the tests run.
+    monkeypatch.setattr(sys, "platform", "darwin")
+
+    # Invoke a command that is known to have its own custom arguments
+    # (In this case, the channel argument for publication)
+    cmd, options, overrides = do_cmdline_parse(
+        "publish macos app -C version='1.2.3' -C extra=42".split(),
+        logger,
+        console,
+    )
+
+    assert isinstance(cmd, macOSAppPublishCommand)
+    assert cmd.input.enabled
+    assert cmd.logger.verbosity == LogLevel.INFO
+    assert cmd.logger is logger
+    assert cmd.input is console
+    assert options == {"channel": "s3"}
+    assert overrides == {
+        "version": "1.2.3",
+        "extra": 42,
+    }
 
 
 def test_unknown_command_options(monkeypatch, capsys, logger, console):
@@ -501,7 +626,7 @@ def test_unknown_command_options(monkeypatch, capsys, logger, console):
     output = capsys.readouterr().err
 
     assert output.startswith(
-        "usage: briefcase publish macOS Xcode [-h] [-v] [-V] [--no-input] [--log]\n"
-        "                                     [-c {s3}]\n"
+        "usage: briefcase publish macOS Xcode [-h] [-C KEY=VALUE] [-v] [-V]\n"
+        "                                     [--no-input] [--log] [-c {s3}]\n"
         "briefcase publish macOS Xcode: error: unrecognized arguments: -x"
     )