Register installed CLI plugins at program start

register_cli_plugins() ran while mvt.ios and mvt.android were being
imported, so importing any part of MVT executed the entry points of every
installed command package. That made plugin loading depend on import
order: a plugin importing from MVT while MVT was still initializing got an
ImportError and was quietly demoted to a broken command, and the same
plugin worked when MVT happened to be imported first.

Move the call into a main() function in each CLI module and point the
console scripts at it, so registration happens once when the program
starts and importing MVT no longer runs third-party code. For packagers:
mvt.ios:cli and mvt.android:cli stay importable, but a wrapper invoking
cli() directly no longer registers the installed plugin commands and
should call main() instead.

README.md

@@ -84,7 +84,7 @@ details.
 
 Users can also add top-level commands to `mvt-ios` and `mvt-android` from
 installed Python packages or local files and folders. See the
-[custom CLI command documentation](https://docs.mvt.re/en/latest/custom_commands/)
+[custom CLI command documentation](https://docs.mvt.re/en/latest/development/custom_commands/)
 for the plugin entry points and `--load-command` interface.
 
 

docs/development/custom_commands.md

@@ -1,7 +1,7 @@
 # Custom CLI Commands
 
 MVT can load additional top-level commands into `mvt-ios` and `mvt-android`.
-Custom commands are different from [custom forensic modules](development.md#custom-modules):
+Custom commands are different from [custom forensic modules](index.md#custom-modules):
 commands add new CLI operations, while modules add analysis steps to existing
 `check-*` commands.
 
@@ -56,6 +56,10 @@ pipx inject mvt my-mvt-plugin
 When MVT is installed in an active virtual environment, install the plugin with
 `pip` in that environment.
 
+Command packages that need their own settings, such as an API key, should store
+them in a namespaced [plugin configuration file](plugin_configuration.md)
+rather than in MVT's own `config.yaml`.
+
 ## Load a Command File
 
 For local commands that are not packaged, create a Python file that exports one

docs/development/index.md

@@ -35,9 +35,16 @@ class DependentModule(MVTModule):
         prerequisite_results = self.get_dependency_results(PrerequisiteModule)
 ```
 
-Selecting a single module also runs its transitive dependencies. If a dependency
-is unavailable or the dependency graph contains a cycle, the command logs a
-warning and does not run any modules.
+Selecting a single module also runs its transitive dependencies.
+
+A module can only depend on modules the command it runs in also has. When a
+declared dependency is not among them, the command logs a warning naming the
+module and the missing dependency, skips that module and everything depending
+on it, and runs the rest of the analysis. Selecting such a module with
+`--module` therefore leaves nothing to run, which the warning explains.
+
+A cycle in the dependency graph is a programming error rather than a
+configuration problem: the command logs a warning and runs no modules at all.
 
 ## Custom modules
 
@@ -160,6 +167,10 @@ For a `pipx` installation of MVT, inject the package into MVT's environment:
 pipx inject mvt mvt-plugin-amnesty-custom
 ```
 
+Module packages that need their own settings, such as an API key, should store
+them in a namespaced [plugin configuration file](plugin_configuration.md)
+rather than in MVT's own `config.yaml`.
+
 ### Naming module packages
 
 Name module packages `mvt-plugin-<name>` (import package `mvt_plugin_<name>`),

docs/development/plugin_configuration.md

@@ -0,0 +1,149 @@
+# Plugin Configuration
+
+Plugin packages that add [custom CLI commands](custom_commands.md) or
+[modules](index.md#installed-module-packages) often need to store their
+own settings, such as an API key, a server URL or the timestamp of the last
+synchronization. MVT provides a namespaced settings base class so each plugin
+keeps its configuration in its own file, and a data folder for anything else a
+plugin needs to keep on disk.
+
+!!! warning
+
+    Do not write plugin settings to MVT's own `config.yaml`. MVT rewrites that
+    file with the settings it knows about every time it starts, so any other
+    section is deleted.
+
+## Where Settings Are Stored
+
+Each plugin gets one YAML file in a `plugins` folder next to MVT's own
+configuration:
+
+```
+~/.config/mvt/plugins/<plugin name>.yaml
+```
+
+The exact parent folder follows the platform convention used for MVT's
+`config.yaml` (for example `~/Library/Application Support/mvt` on macOS). Use
+`mvt.common.plugin_config.plugin_config_path()` instead of building the path by
+hand.
+
+Plugin names must be lowercase and may only contain letters, digits and dashes,
+matching the `mvt-plugin-<name>` package naming convention. MVT creates the
+`plugins` folder with `0700` permissions and writes the settings files with
+`0600` permissions, because they commonly hold credentials. Files are written
+through a temporary file and moved into place, so an interrupted save never
+leaves a partially written settings file behind.
+
+## Plugin Data Folder
+
+Everything else a plugin keeps on disk, such as a cache, a downloaded artifact
+or synchronization state, belongs in the folder returned by the `data_folder()`
+class method of the plugin's settings class, or by
+`mvt.common.plugin_config.plugin_data_folder()` called with the plugin name if
+the plugin has no settings class:
+
+```
+~/.local/share/mvt/plugin-data/<plugin name>/                # Linux
+~/Library/Application Support/mvt/plugin-data/<plugin name>/ # macOS
+```
+
+The folder sits beside MVT's own data, such as the downloaded indicators. It is
+created if it is missing, with `0700` permissions. Asking for it again returns
+the same path and leaves the contents alone, so a plugin can ask for it every
+time it needs the folder. `ExamplePluginSettings` below is the settings class
+defined in the next section:
+
+```python
+import os
+
+
+def cache_path() -> str:
+    folder = ExamplePluginSettings.data_folder()
+    return os.path.join(folder, "virustotal_lookups_cache.json")
+```
+
+A plugin which has no settings class calls
+`plugin_data_folder("example-plugin")` instead.
+
+Do not fall back on a path of your own such as `~/.cache/example-plugin`: it
+is a Linux-only convention, and MVT will not create it for you.
+
+## Defining Plugin Settings
+
+Subclass `MVTPluginSettings`, set `plugin_name` and declare typed fields with
+defaults:
+
+```python
+from typing import Optional
+
+from mvt.common.plugin_config import MVTPluginSettings
+
+
+class ExamplePluginSettings(MVTPluginSettings):
+    plugin_name = "example-plugin"
+
+    API_KEY: Optional[str] = None
+    MAX_RESULTS: int = 25
+    LAST_SYNC: Optional[str] = None
+```
+
+`load()` returns the current settings and `save()` writes them back:
+
+```python
+from datetime import datetime, timezone
+
+import click
+
+
+def sync():
+    settings = ExamplePluginSettings.load()
+    if not settings.API_KEY:
+        raise click.ClickException(
+            "No API key configured. Set MVT_PLUGIN_EXAMPLE_PLUGIN_API_KEY or "
+            "run 'example-plugin configure'."
+        )
+
+    settings.LAST_SYNC = datetime.now(timezone.utc).isoformat()
+    settings.save()
+```
+
+A missing settings file is not an error: the plugin then runs on the field
+defaults and on whatever the environment provides. `save()` only persists the
+values that differ from the defaults, and it never touches MVT's `config.yaml`.
+A settings file that cannot be parsed, or that does not hold a mapping of
+setting names to values, raises a `PluginConfigLoadError` naming the file.
+
+Every subclass that sets its own `plugin_name` gets its own file and its own
+environment namespace. A subclass that does not redefine `plugin_name` inherits
+it, and therefore shares the file and the environment variables of its parent
+class.
+
+## Environment Variables
+
+Every field can also be set with an environment variable. The prefix is
+`MVT_PLUGIN_`, followed by the plugin name upper-cased with dashes replaced by
+underscores, followed by the field name. For the example above:
+
+```bash
+export MVT_PLUGIN_EXAMPLE_PLUGIN_API_KEY=...
+export MVT_PLUGIN_EXAMPLE_PLUGIN_MAX_RESULTS=50
+```
+
+Settings resolve in this order, from highest to lowest priority:
+
+1. Arguments passed to the settings class directly, such as
+   `ExamplePluginSettings(API_KEY="...")`
+2. Environment variables
+3. The plugin's YAML file
+4. The field defaults declared on the settings class
+
+!!! tip
+
+    On shared or multi-user machines, prefer passing API keys through
+    environment variables rather than saving them to the plugin file. `save()`
+    skips every value that the environment currently supplies, so a credential
+    provided that way is not copied into the settings file when a plugin saves
+    an unrelated setting.
+
+Unknown keys in a plugin's YAML file are ignored, so a settings file written by
+a newer version of a plugin does not break an older one.

mkdocs.yml

@@ -50,6 +50,7 @@ nav:
         - Check Android Intrusion Logs: "android/intrusion_logs.md"
     - Indicators of Compromise: "iocs.md"
     - Development:
-        - Development Instructions: "development.md"
-        - Custom CLI Commands: "custom_commands.md"
+        - Development Instructions: "development/index.md"
+        - Custom CLI Commands: "development/custom_commands.md"
+        - Plugin Configuration: "development/plugin_configuration.md"
     - License: "license.md"

pyproject.toml

@@ -44,8 +44,8 @@ homepage = "https://docs.mvt.re/en/latest/"
 repository = "https://github.com/mvt-project/mvt"
 
 [project.scripts]
-mvt-ios = "mvt.ios:cli"
-mvt-android = "mvt.android:cli"
+mvt-ios = "mvt.ios:main"
+mvt-android = "mvt.android:main"
 
 [dependency-groups]
 dev = [

src/mvt/android/__init__.py

@@ -3,4 +3,4 @@
 # Use of this software is governed by the MVT License 1.1 that can be found at
 #   https://license.mvt.re/1.1/
 
-from .cli import cli
+from .cli import cli, main

src/mvt/android/cli.py

@@ -514,8 +514,19 @@ def download_indicators():
     ioc_updates.update()
 
 
-register_cli_plugins(
-    cli,
-    entry_point_group=ANDROID_CLI_PLUGIN_GROUP,
-    environment_variable=MVT_ANDROID_CUSTOM_COMMANDS_ENV,
-)
+# ==============================================================================
+# Entry point of the mvt-android console script
+# ==============================================================================
+def main() -> None:
+    """Register the external commands and run the mvt-android CLI.
+
+    External commands are registered here rather than when this module is
+    imported, so that importing MVT never runs third-party code and a plugin
+    importing from MVT cannot re-enter a module that is still initializing.
+    """
+    register_cli_plugins(
+        cli,
+        entry_point_group=ANDROID_CLI_PLUGIN_GROUP,
+        environment_variable=MVT_ANDROID_CUSTOM_COMMANDS_ENV,
+    )
+    cli()

src/mvt/common/command.py

@@ -317,6 +317,81 @@ class Command:
         console.print("")
         console.print(panel)
 
+    def _skipped_modules(
+        self,
+        required: list[type[MVTModule]],
+        module_indexes: dict[type[MVTModule], int],
+    ) -> dict[type[MVTModule], tuple[type[MVTModule], type[MVTModule]]]:
+        """Return the modules to drop because a dependency is unavailable.
+
+        A module declaring a dependency this command cannot provide is unable
+        to run, and so is every module depending on it. Dropping only those
+        keeps a single wrong declaration - in a module scoped to several
+        commands, for example - from silencing an entire analysis.
+
+        The returned mapping gives, for each skipped module, the module which
+        is missing a dependency and the dependency it is missing.
+        """
+        skipped: dict[type[MVTModule], tuple[type[MVTModule], type[MVTModule]]] = {}
+        # Skipping the one module a run was asked for leaves nothing to run,
+        # which the caller reports instead.
+        remainder = (
+            "" if self.module_name else " The rest of the analysis will still run."
+        )
+
+        # Skipping one module can skip the modules depending on it, which the
+        # pass over the module list may already have gone past, so repeat the
+        # pass until nothing changes.
+        changed = True
+        while changed:
+            changed = False
+            for module in required:
+                if module in skipped:
+                    continue
+
+                for dependency in module.dependencies:
+                    if dependency not in module_indexes:
+                        skipped[module] = (module, dependency)
+                        changed = True
+                        self.log.warning(
+                            "Module %s will be SKIPPED: it depends on module "
+                            "%s, which is not available in this command.%s",
+                            module.__name__,
+                            dependency.__name__,
+                            remainder,
+                        )
+                        break
+
+                    if dependency in skipped:
+                        root, missing = skipped[dependency]
+                        skipped[module] = (root, missing)
+                        changed = True
+                        if dependency is root:
+                            self.log.warning(
+                                "Module %s will be SKIPPED: it depends on "
+                                "module %s, itself skipped for depending on "
+                                "unavailable module %s.%s",
+                                module.__name__,
+                                dependency.__name__,
+                                missing.__name__,
+                                remainder,
+                            )
+                        else:
+                            self.log.warning(
+                                "Module %s will be SKIPPED: it depends on "
+                                "skipped module %s, in a chain starting at "
+                                "module %s, which depends on unavailable "
+                                "module %s.%s",
+                                module.__name__,
+                                dependency.__name__,
+                                root.__name__,
+                                missing.__name__,
+                                remainder,
+                            )
+                        break
+
+        return skipped
+
     def _ordered_modules(self) -> Optional[list[type[MVTModule]]]:
         """Return enabled modules in stable topological order."""
         modules = self._available_modules()
@@ -329,30 +404,34 @@ class Command:
         else:
             selected = [module for module in modules if module.enabled]
 
-        required = set(selected)
+        required: set[type[MVTModule]] = set()
         pending = list(selected)
         while pending:
             module = pending.pop()
+            if module in required:
+                continue
+            required.add(module)
             for dependency in module.dependencies:
-                if dependency not in module_indexes:
-                    self.log.warning(
-                        "Module %s depends on unavailable module %s. "
-                        "No modules will be run.",
-                        module.__name__,
-                        dependency.__name__,
-                    )
-                    return None
-                if dependency not in required:
-                    required.add(dependency)
+                # Unavailable dependencies are reported by _skipped_modules().
+                if dependency in module_indexes:
                     pending.append(dependency)
 
+        ordered_required = sorted(required, key=lambda module: module_indexes[module])
+        skipped = self._skipped_modules(ordered_required, module_indexes)
+        runnable = [module for module in ordered_required if module not in skipped]
+        if skipped and not runnable:
+            self.log.warning(
+                "Every selected module was skipped for an unavailable "
+                "dependency. No modules will be run."
+            )
+
         dependents: dict[type[MVTModule], list[type[MVTModule]]] = {
-            module: [] for module in required
+            module: [] for module in runnable
         }
-        indegree = {module: 0 for module in required}
-        for module in required:
+        indegree = {module: 0 for module in runnable}
+        for module in runnable:
             for dependency in module.dependencies:
-                if dependency not in required:
+                if dependency not in indegree:
                     continue
                 dependents[dependency].append(module)
                 indegree[module] += 1
@@ -371,7 +450,7 @@ class Command:
                 if indegree[dependent] == 0:
                     heappush(ready, (module_indexes[dependent], dependent))
 
-        if len(ordered) != len(required):
+        if len(ordered) != len(runnable):
             cyclic_modules = sorted(
                 (module.__name__ for module, count in indegree.items() if count > 0)
             )

src/mvt/common/plugin_config.py

@@ -0,0 +1,299 @@
+# Mobile Verification Toolkit (MVT)
+# Copyright (c) 2021-2026 The MVT Authors.
+# Use of this software is governed by the MVT License 1.1 that can be found at
+#   https://license.mvt.re/1.1/
+
+import contextlib
+import json
+import os
+import re
+import tempfile
+from typing import Any, ClassVar, Dict, List, Tuple, Type, TypeVar
+
+import yaml
+from appdirs import user_config_dir, user_data_dir
+from pydantic import ValidationError
+from pydantic_settings import (
+    BaseSettings,
+    EnvSettingsSource,
+    PydanticBaseSettingsSource,
+    SettingsConfigDict,
+    YamlConfigSettingsSource,
+)
+
+PLUGIN_CONFIG_FOLDER_NAME = "plugins"
+# Not "plugins": on macOS the configuration and data folders are the same
+# directory, and that name already holds the settings files.
+PLUGIN_DATA_FOLDER_NAME = "plugin-data"
+PLUGIN_ENV_PREFIX = "MVT_PLUGIN_"
+
+PLUGIN_NAME_PATTERN = re.compile(r"[a-z0-9][a-z0-9-]*")
+
+PluginSettingsType = TypeVar("PluginSettingsType", bound="MVTPluginSettings")
+
+
+class PluginConfigLoadError(Exception):
+    pass
+
+
+def validate_plugin_name(plugin_name: Any) -> str:
+    """
+    Check that a plugin name is safe to use in a file name and an env variable.
+
+    :param plugin_name: Name to validate.
+    :returns: The validated plugin name.
+    """
+    if not isinstance(plugin_name, str):
+        raise TypeError(
+            f"Plugin name must be a string, not {type(plugin_name).__name__}"
+        )
+    if not PLUGIN_NAME_PATTERN.fullmatch(plugin_name):
+        raise ValueError(
+            f"Invalid plugin name {plugin_name!r}: plugin names must start with a "
+            "lowercase letter or a digit and may only contain lowercase letters, "
+            "digits and dashes"
+        )
+    return plugin_name
+
+
+def plugin_config_folder() -> str:
+    """
+    Return the folder where plugins store their configuration files.
+
+    The path is resolved on every call so it always reflects the current
+    environment.
+    """
+    return os.path.join(user_config_dir("mvt"), PLUGIN_CONFIG_FOLDER_NAME)
+
+
+def plugin_config_path(plugin_name: str) -> str:
+    """
+    Return the path of the configuration file of a given plugin.
+
+    :param plugin_name: Name of the plugin.
+    """
+    return os.path.join(
+        plugin_config_folder(), f"{validate_plugin_name(plugin_name)}.yaml"
+    )
+
+
+def plugin_data_folder(plugin_name: str) -> str:
+    """
+    Return the folder where a given plugin stores its data, creating it.
+
+    Plugins should keep whatever they persist, such as caches or downloaded
+    artifacts, in this folder. It is created with owner-only permissions. The
+    path is resolved on every call so it always reflects the current
+    environment. A plugin with a settings class calls
+    `MVTPluginSettings.data_folder()` instead, which passes `plugin_name` here.
+
+    :param plugin_name: Name of the plugin.
+    :returns: The path of the data folder of the plugin.
+    """
+    # Validate the name before anything is created, so an unsafe name cannot
+    # leave a folder behind.
+    name = validate_plugin_name(plugin_name)
+
+    # makedirs() applies its mode only to the last folder of the path, so
+    # MVT's own data folder keeps the default permissions while the two
+    # plugin folders are private.
+    data_folder = os.path.join(user_data_dir("mvt"), PLUGIN_DATA_FOLDER_NAME)
+    os.makedirs(data_folder, mode=0o700, exist_ok=True)
+
+    folder = os.path.join(data_folder, name)
+    os.makedirs(folder, mode=0o700, exist_ok=True)
+    return folder
+
+
+def plugin_env_prefix(plugin_name: str) -> str:
+    """
+    Return the environment variable prefix used by a given plugin.
+
+    Dashes are replaced by underscores. Plugin names cannot contain underscores,
+    so two different plugin names never share an environment namespace.
+
+    :param plugin_name: Name of the plugin.
+    """
+    name = validate_plugin_name(plugin_name).upper().replace("-", "_")
+    return f"{PLUGIN_ENV_PREFIX}{name}_"
+
+
+def _settings_plugin_name(settings_cls: Type[BaseSettings]) -> str:
+    plugin_name = getattr(settings_cls, "plugin_name", None)
+    if plugin_name is None:
+        raise TypeError(
+            f"{settings_cls.__name__} must set a 'plugin_name' class attribute to "
+            "namespace its configuration file and environment variables"
+        )
+    return validate_plugin_name(plugin_name)
+
+
+def _plugin_yaml_source(
+    settings_cls: Type[BaseSettings], config_path: str
+) -> YamlConfigSettingsSource:
+    """
+    Build the YAML settings source of a plugin, reporting unusable files.
+
+    A missing file is not an error, but a file which cannot be parsed or which
+    does not hold a mapping of setting names is reported with its path.
+    """
+    try:
+        return YamlConfigSettingsSource(settings_cls, config_path)
+    except yaml.YAMLError as exc:
+        raise PluginConfigLoadError(
+            f"Invalid plugin configuration file {config_path}: {exc}"
+        ) from exc
+    except (TypeError, ValueError) as exc:
+        raise PluginConfigLoadError(
+            f"Invalid plugin configuration file {config_path}: the file must "
+            "contain a mapping of setting names to values"
+        ) from exc
+
+
+class MVTPluginSettings(BaseSettings):
+    """
+    Base class for plugin-namespaced settings.
+
+    Subclass with typed fields and set `plugin_name`. Values resolve from
+    constructor arguments, then environment variables (MVT_PLUGIN_<NAME>_*),
+    then the plugin's YAML file (~/.config/mvt/plugins/<name>.yaml), then field
+    defaults.
+
+    Plugins must not store their settings in MVT's own configuration file: MVT
+    rewrites it with the fields it knows about, dropping anything else.
+
+    `data_folder()` returns the folder the plugin keeps its data in.
+    """
+
+    model_config = SettingsConfigDict(extra="ignore")
+
+    plugin_name: ClassVar[str]
+
+    def __init_subclass__(cls, **kwargs: Any) -> None:
+        super().__init_subclass__(**kwargs)
+        plugin_name = _settings_plugin_name(cls)
+        # Namespace the environment variables of this plugin. Each pydantic
+        # model gets its own configuration dictionary, so this does not leak
+        # into other plugins.
+        cls.model_config["env_prefix"] = plugin_env_prefix(plugin_name)
+
+    @classmethod
+    def settings_customise_sources(
+        cls,
+        settings_cls: Type[BaseSettings],
+        init_settings: PydanticBaseSettingsSource,
+        env_settings: PydanticBaseSettingsSource,
+        dotenv_settings: PydanticBaseSettingsSource,
+        file_secret_settings: PydanticBaseSettingsSource,
+    ) -> Tuple[PydanticBaseSettingsSource, ...]:
+        config_path = plugin_config_path(_settings_plugin_name(settings_cls))
+        yaml_source = _plugin_yaml_source(settings_cls, config_path)
+        # Explicit arguments take precedence over environment variables, which
+        # in turn take precedence over the configuration file.
+        return (init_settings, env_settings, yaml_source)
+
+    @classmethod
+    def load(cls: Type[PluginSettingsType]) -> PluginSettingsType:
+        """
+        Load the settings of the plugin.
+
+        A missing configuration file is not an error: the settings then come
+        from the environment and from the field defaults.
+        """
+        return cls()
+
+    @classmethod
+    def data_folder(cls) -> str:
+        """
+        Return the data folder of the plugin, creating it.
+
+        The folder is the one plugin_data_folder() returns for `plugin_name`,
+        so a plugin with a settings class does not repeat its name.
+        """
+        return plugin_data_folder(_settings_plugin_name(cls))
+
+    def _environment_values(self) -> Dict[str, Any]:
+        """
+        Return the settings values currently supplied by the environment.
+
+        Values are validated by the model, so they can be compared with the
+        values held by this instance.
+        """
+        settings_cls = type(self)
+        raw_values = EnvSettingsSource(settings_cls)()
+        names = [name for name in raw_values if name in settings_cls.model_fields]
+        if not names:
+            return {}
+
+        # Fall back on the current values for the fields the environment does
+        # not set, so that required fields do not fail validation here.
+        current_values = json.loads(self.model_dump_json())
+        try:
+            from_environment = settings_cls.model_validate(
+                {**current_values, **raw_values}
+            )
+        except ValidationError:
+            # An environment variable which the model cannot validate must not
+            # stop the other environment values from being recognised, or a
+            # credential would be written to the configuration file.
+            return self._environment_values_by_field(current_values, raw_values, names)
+        return {name: getattr(from_environment, name) for name in names}
+
+    def _environment_values_by_field(
+        self,
+        current_values: Dict[str, Any],
+        raw_values: Dict[str, Any],
+        names: List[str],
+    ) -> Dict[str, Any]:
+        """
+        Validate each environment value on its own, skipping unusable ones.
+
+        :param current_values: Serialized values held by this instance.
+        :param raw_values: Values supplied by the environment.
+        :param names: Names of the fields set by the environment.
+        """
+        settings_cls = type(self)
+        values = {}
+        for name in names:
+            try:
+                from_environment = settings_cls.model_validate(
+                    {**current_values, name: raw_values[name]}
+                )
+            except ValidationError:
+                continue
+            values[name] = getattr(from_environment, name)
+        return values
+
+    def save(self) -> None:
+        """
+        Save the current settings to the configuration file of the plugin.
+
+        Only values which differ from the field defaults are persisted. Values
+        which come from the environment are not written to disk, so credentials
+        passed as environment variables stay out of the configuration file.
+        MVT's own configuration file is never modified.
+        """
+        config_folder = plugin_config_folder()
+        if not os.path.isdir(config_folder):
+            os.makedirs(config_folder, mode=0o700, exist_ok=True)
+
+        values = json.loads(self.model_dump_json(exclude_defaults=True))
+        for name, environment_value in self._environment_values().items():
+            if name in values and getattr(self, name, None) == environment_value:
+                del values[name]
+
+        # Settings files can hold credentials, so write them through a private
+        # temporary file and move it in place. The file is then never partially
+        # written and never briefly readable by other users.
+        config_path = plugin_config_path(self.plugin_name)
+        descriptor, temporary_path = tempfile.mkstemp(
+            dir=config_folder, prefix=f".{self.plugin_name}-", suffix=".yaml"
+        )
+        try:
+            with os.fdopen(descriptor, "w") as config_file:
+                config_file.write(yaml.dump(values, default_flow_style=False))
+            os.replace(temporary_path, config_path)
+        except BaseException:
+            with contextlib.suppress(OSError):
+                os.unlink(temporary_path)
+            raise

src/mvt/ios/__init__.py

@@ -3,4 +3,4 @@
 # Use of this software is governed by the MVT License 1.1 that can be found at
 #   https://license.mvt.re/1.1/
 
-from .cli import cli
+from .cli import cli, main

src/mvt/ios/cli.py

@@ -532,8 +532,19 @@ def download_iocs():
     ioc_updates.update()
 
 
-register_cli_plugins(
-    cli,
-    entry_point_group=IOS_CLI_PLUGIN_GROUP,
-    environment_variable=MVT_IOS_CUSTOM_COMMANDS_ENV,
-)
+# ==============================================================================
+# Entry point of the mvt-ios console script
+# ==============================================================================
+def main() -> None:
+    """Register the external commands and run the mvt-ios CLI.
+
+    External commands are registered here rather than when this module is
+    imported, so that importing MVT never runs third-party code and a plugin
+    importing from MVT cannot re-enter a module that is still initializing.
+    """
+    register_cli_plugins(
+        cli,
+        entry_point_group=IOS_CLI_PLUGIN_GROUP,
+        environment_variable=MVT_IOS_CUSTOM_COMMANDS_ENV,
+    )
+    cli()

tests/common/test_command.py

@@ -157,7 +157,7 @@ class TestCommand:
         assert not hasattr(cmd, "initialized")
         assert "Circular module dependency detected" in caplog.text
 
-    def test_unavailable_dependency_warns_and_stops(self, caplog):
+    def test_unavailable_dependency_only_skips_the_dependent_module(self, caplog):
         class UnavailableModule(RecordingModule):
             pass
 
@@ -165,14 +165,97 @@ class TestCommand:
             dependencies = (UnavailableModule,)
 
         cmd = RecordingCommand()
-        cmd.modules = [DependentModule]
+        cmd.modules = [DependentModule, IndependentModule, FirstModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["IndependentModule", "FirstModule"]
+        assert cmd.initialized
+        assert "Module DependentModule will be SKIPPED" in caplog.text
+        assert "depends on module UnavailableModule" in caplog.text
+
+    def test_modules_depending_on_a_skipped_module_are_skipped_too(self, caplog):
+        class UnavailableModule(RecordingModule):
+            pass
+
+        class SkippedModule(RecordingModule):
+            dependencies = (UnavailableModule,)
+
+        class DependsOnSkippedModule(RecordingModule):
+            dependencies = (SkippedModule,)
+
+        class DependsOnTheChain(RecordingModule):
+            dependencies = (DependsOnSkippedModule,)
+
+        cmd = RecordingCommand()
+        cmd.modules = [
+            DependsOnTheChain,
+            DependsOnSkippedModule,
+            SkippedModule,
+            IndependentModule,
+        ]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == ["IndependentModule"]
+        skip_warnings = [
+            record.getMessage()
+            for record in caplog.records
+            if "will be SKIPPED" in record.getMessage()
+        ]
+        assert len(skip_warnings) == 3
+        assert [warning.split()[1] for warning in skip_warnings] == [
+            "SkippedModule",
+            "DependsOnSkippedModule",
+            "DependsOnTheChain",
+        ]
+        # Every warning names the root cause: the module missing a dependency
+        # and the dependency it is missing.
+        assert all("UnavailableModule" in warning for warning in skip_warnings)
+        assert all("module SkippedModule" in warning for warning in skip_warnings[1:])
+
+    def test_explicitly_selected_module_with_missing_dependency_runs_nothing(
+        self, caplog
+    ):
+        class UnavailableModule(RecordingModule):
+            pass
+
+        class DependentModule(RecordingModule):
+            dependencies = (UnavailableModule,)
+
+        cmd = RecordingCommand(module_name="DependentModule")
+        cmd.modules = [DependentModule, IndependentModule]
 
         with caplog.at_level(logging.WARNING):
             cmd.run()
 
         assert RecordingModule.run_order == []
-        assert not hasattr(cmd, "initialized")
-        assert "depends on unavailable module UnavailableModule" in caplog.text
+        assert "Module DependentModule will be SKIPPED" in caplog.text
+        assert "No modules will be run" in caplog.text
+        # Nothing else was selected, so the warning must not promise that the
+        # analysis continues right before saying that it does not.
+        assert "The rest of the analysis will still run" not in caplog.text
+
+    def test_unaffected_dependency_chains_keep_their_order(self, caplog):
+        class UnavailableModule(RecordingModule):
+            pass
+
+        class SkippedModule(RecordingModule):
+            dependencies = (UnavailableModule,)
+
+        cmd = RecordingCommand()
+        cmd.modules = [ThirdModule, SkippedModule, SecondModule, FirstModule]
+
+        with caplog.at_level(logging.WARNING):
+            cmd.run()
+
+        assert RecordingModule.run_order == [
+            "FirstModule",
+            "SecondModule",
+            "ThirdModule",
+        ]
 
     def test_custom_modules_are_filtered_before_ordering(self):
         cmd = RecordingCommand()

tests/common/test_plugin_config.py

@@ -0,0 +1,391 @@
+# Mobile Verification Toolkit (MVT)
+# Copyright (c) 2021-2026 The MVT Authors.
+# Use of this software is governed by the MVT License 1.1 that can be found at
+#   https://license.mvt.re/1.1/
+
+import os
+import stat
+import sys
+from typing import Optional
+
+import pytest
+import yaml
+
+from mvt.common.plugin_config import (
+    MVTPluginSettings,
+    PluginConfigLoadError,
+    plugin_config_folder,
+    plugin_config_path,
+    plugin_data_folder,
+    plugin_env_prefix,
+)
+
+
+class ExamplePluginSettings(MVTPluginSettings):
+    plugin_name = "example-plugin"
+
+    API_KEY: Optional[str] = None
+    CACHE_FOLDER: str = "cache"
+    MAX_RESULTS: int = 25
+
+
+class OtherPluginSettings(MVTPluginSettings):
+    plugin_name = "other-plugin"
+
+    API_KEY: Optional[str] = None
+
+
+@pytest.fixture
+def config_folder(tmp_path, monkeypatch):
+    monkeypatch.setattr(
+        "mvt.common.plugin_config.user_config_dir",
+        lambda *args, **kwargs: str(tmp_path),
+    )
+    return tmp_path
+
+
+@pytest.fixture
+def data_folder(tmp_path, monkeypatch):
+    folder = tmp_path / "data"
+    monkeypatch.setattr(
+        "mvt.common.plugin_config.user_data_dir",
+        lambda *args, **kwargs: str(folder),
+    )
+    return folder
+
+
+def _write_plugin_file(plugin_name, values):
+    config_path = plugin_config_path(plugin_name)
+    os.makedirs(os.path.dirname(config_path), exist_ok=True)
+    content = values if isinstance(values, str) else yaml.dump(values)
+    with open(config_path, "w") as config_file:
+        config_file.write(content)
+    return config_path
+
+
+def test_plugin_paths_and_prefixes_are_namespaced(config_folder):
+    assert plugin_config_folder() == str(config_folder / "plugins")
+    assert plugin_config_path("example-plugin") == str(
+        config_folder / "plugins" / "example-plugin.yaml"
+    )
+    assert plugin_env_prefix("example-plugin") == "MVT_PLUGIN_EXAMPLE_PLUGIN_"
+    assert plugin_env_prefix("other-plugin") == "MVT_PLUGIN_OTHER_PLUGIN_"
+
+
+def test_defaults_are_used_without_file_or_environment(config_folder):
+    settings = ExamplePluginSettings.load()
+
+    assert settings.API_KEY is None
+    assert settings.CACHE_FOLDER == "cache"
+    assert settings.MAX_RESULTS == 25
+    assert not os.path.exists(plugin_config_path("example-plugin"))
+
+
+def test_values_are_loaded_from_the_plugin_file(config_folder):
+    _write_plugin_file("example-plugin", {"API_KEY": "from-file", "MAX_RESULTS": 5})
+
+    settings = ExamplePluginSettings.load()
+
+    assert settings.API_KEY == "from-file"
+    assert settings.MAX_RESULTS == 5
+    assert settings.CACHE_FOLDER == "cache"
+
+
+def test_environment_overrides_the_plugin_file(config_folder, monkeypatch):
+    _write_plugin_file("example-plugin", {"API_KEY": "from-file", "MAX_RESULTS": 5})
+    monkeypatch.setenv("MVT_PLUGIN_EXAMPLE_PLUGIN_API_KEY", "from-environment")
+
+    settings = ExamplePluginSettings.load()
+
+    assert settings.API_KEY == "from-environment"
+    assert settings.MAX_RESULTS == 5
+
+
+def test_arguments_override_the_environment_and_the_plugin_file(
+    config_folder, monkeypatch
+):
+    _write_plugin_file("example-plugin", {"API_KEY": "from-file", "MAX_RESULTS": 5})
+    monkeypatch.setenv("MVT_PLUGIN_EXAMPLE_PLUGIN_API_KEY", "from-environment")
+    monkeypatch.setenv("MVT_PLUGIN_EXAMPLE_PLUGIN_MAX_RESULTS", "10")
+
+    settings = ExamplePluginSettings(API_KEY="from-argument")
+
+    assert settings.API_KEY == "from-argument"
+    assert settings.MAX_RESULTS == 10
+
+
+def test_save_and_load_round_trip(config_folder):
+    settings = ExamplePluginSettings.load()
+    settings.API_KEY = "saved-key"
+    settings.MAX_RESULTS = 100
+
+    settings.save()
+
+    config_path = plugin_config_path("example-plugin")
+    assert os.path.isfile(config_path)
+    with open(config_path) as config_file:
+        assert yaml.safe_load(config_file) == {
+            "API_KEY": "saved-key",
+            "MAX_RESULTS": 100,
+        }
+
+    reloaded = ExamplePluginSettings.load()
+    assert reloaded.API_KEY == "saved-key"
+    assert reloaded.MAX_RESULTS == 100
+    assert reloaded.CACHE_FOLDER == "cache"
+
+
+@pytest.mark.skipif(
+    sys.platform == "win32", reason="POSIX file permissions are not available"
+)
+def test_saved_file_is_only_readable_by_the_user(config_folder):
+    settings = ExamplePluginSettings.load()
+    settings.API_KEY = "saved-key"
+
+    settings.save()
+
+    config_path = plugin_config_path("example-plugin")
+    assert stat.S_IMODE(os.stat(config_path).st_mode) == 0o600
+    folder_mode = stat.S_IMODE(os.stat(plugin_config_folder()).st_mode)
+    assert folder_mode & 0o077 == 0
+
+
+@pytest.mark.skipif(
+    sys.platform == "win32", reason="POSIX file permissions are not available"
+)
+def test_save_restricts_the_permissions_of_an_existing_file(config_folder):
+    config_path = _write_plugin_file("example-plugin", {"API_KEY": "from-file"})
+    os.chmod(config_path, 0o644)
+
+    settings = ExamplePluginSettings.load()
+    settings.MAX_RESULTS = 100
+    settings.save()
+
+    assert stat.S_IMODE(os.stat(config_path).st_mode) == 0o600
+    assert os.listdir(plugin_config_folder()) == ["example-plugin.yaml"]
+
+
+def test_save_only_persists_non_default_values(config_folder):
+    settings = ExamplePluginSettings.load()
+    settings.CACHE_FOLDER = "another-cache"
+
+    settings.save()
+
+    with open(plugin_config_path("example-plugin")) as config_file:
+        assert yaml.safe_load(config_file) == {"CACHE_FOLDER": "another-cache"}
+
+
+def test_save_does_not_persist_values_coming_from_the_environment(
+    config_folder, monkeypatch
+):
+    monkeypatch.setenv("MVT_PLUGIN_EXAMPLE_PLUGIN_API_KEY", "environment-secret")
+
+    settings = ExamplePluginSettings.load()
+    assert settings.API_KEY == "environment-secret"
+    settings.MAX_RESULTS = 100
+    settings.save()
+
+    with open(plugin_config_path("example-plugin")) as config_file:
+        assert yaml.safe_load(config_file) == {"MAX_RESULTS": 100}
+
+
+def test_an_invalid_environment_variable_still_protects_the_other_values(
+    config_folder, monkeypatch
+):
+    monkeypatch.setenv("MVT_PLUGIN_EXAMPLE_PLUGIN_API_KEY", "environment-secret")
+    monkeypatch.setenv("MVT_PLUGIN_EXAMPLE_PLUGIN_MAX_RESULTS", "not-an-int")
+
+    settings = ExamplePluginSettings(MAX_RESULTS=100)
+    assert settings.API_KEY == "environment-secret"
+    settings.save()
+
+    with open(plugin_config_path("example-plugin")) as config_file:
+        saved_values = yaml.safe_load(config_file)
+    assert saved_values == {"MAX_RESULTS": 100}
+    assert "API_KEY" not in saved_values
+
+
+def test_save_persists_values_which_differ_from_the_environment(
+    config_folder, monkeypatch
+):
+    monkeypatch.setenv("MVT_PLUGIN_EXAMPLE_PLUGIN_API_KEY", "environment-secret")
+
+    settings = ExamplePluginSettings.load()
+    settings.API_KEY = "chosen-key"
+    settings.save()
+
+    with open(plugin_config_path("example-plugin")) as config_file:
+        assert yaml.safe_load(config_file) == {"API_KEY": "chosen-key"}
+
+
+def test_save_does_not_write_the_mvt_configuration_file(config_folder):
+    settings = ExamplePluginSettings.load()
+    settings.API_KEY = "saved-key"
+
+    settings.save()
+
+    assert os.listdir(config_folder) == ["plugins"]
+
+
+def test_unknown_keys_in_the_plugin_file_are_ignored(config_folder):
+    _write_plugin_file(
+        "example-plugin",
+        {"API_KEY": "from-file", "UNKNOWN_SETTING": "ignored"},
+    )
+
+    settings = ExamplePluginSettings.load()
+
+    assert settings.API_KEY == "from-file"
+    assert not hasattr(settings, "UNKNOWN_SETTING")
+
+
+def test_unparsable_plugin_file_is_reported_with_its_path(config_folder):
+    config_path = _write_plugin_file("example-plugin", "API_KEY: [unclosed\n")
+
+    with pytest.raises(PluginConfigLoadError) as raised:
+        ExamplePluginSettings.load()
+
+    assert config_path in str(raised.value)
+
+
+def test_plugin_file_which_is_not_a_mapping_is_reported_with_its_path(config_folder):
+    config_path = _write_plugin_file("example-plugin", "- one\n- two\n")
+
+    with pytest.raises(PluginConfigLoadError) as raised:
+        ExamplePluginSettings.load()
+
+    assert config_path in str(raised.value)
+    assert "mapping of setting names" in str(raised.value)
+
+
+def test_plugins_do_not_interfere_with_each_other(config_folder, monkeypatch):
+    _write_plugin_file("other-plugin", {"API_KEY": "other-file-key"})
+    monkeypatch.setenv("MVT_PLUGIN_EXAMPLE_PLUGIN_API_KEY", "example-environment-key")
+
+    example_settings = ExamplePluginSettings.load()
+    other_settings = OtherPluginSettings.load()
+
+    assert example_settings.API_KEY == "example-environment-key"
+    assert other_settings.API_KEY == "other-file-key"
+
+    example_settings.MAX_RESULTS = 100
+    example_settings.save()
+    assert sorted(os.listdir(plugin_config_folder())) == [
+        "example-plugin.yaml",
+        "other-plugin.yaml",
+    ]
+    with open(plugin_config_path("other-plugin")) as config_file:
+        assert yaml.safe_load(config_file) == {"API_KEY": "other-file-key"}
+
+
+def test_subclass_without_plugin_name_is_rejected():
+    with pytest.raises(TypeError, match="plugin_name"):
+
+        class MissingNameSettings(MVTPluginSettings):
+            API_KEY: Optional[str] = None
+
+
+def test_subclass_with_invalid_plugin_name_is_rejected():
+    with pytest.raises(ValueError, match="Invalid plugin name"):
+
+        class InvalidNameSettings(MVTPluginSettings):
+            plugin_name = "Bad/Name"
+
+
+def test_underscores_are_not_allowed_in_plugin_names():
+    # Underscores are replaced by dashes in the environment prefix, so allowing
+    # both would let two plugin names share one environment namespace.
+    with pytest.raises(ValueError, match="Invalid plugin name"):
+
+        class UnderscoreNameSettings(MVTPluginSettings):
+            plugin_name = "under_score"
+
+    with pytest.raises(ValueError, match="Invalid plugin name"):
+        plugin_config_path("under_score")
+    with pytest.raises(ValueError, match="Invalid plugin name"):
+        plugin_env_prefix("under_score")
+
+
+@pytest.mark.parametrize(
+    "plugin_name", ["../escape", "folder/name", "UPPER", "-dash", ""]
+)
+def test_unsafe_plugin_names_have_no_configuration_path(plugin_name):
+    with pytest.raises(ValueError, match="Invalid plugin name"):
+        plugin_config_path(plugin_name)
+
+
+def test_data_folder_is_namespaced_and_created(data_folder):
+    folder = plugin_data_folder("example-plugin")
+
+    assert folder == str(data_folder / "plugin-data" / "example-plugin")
+    assert os.path.isdir(folder)
+
+
+def test_data_folder_can_be_requested_repeatedly(data_folder):
+    folder = plugin_data_folder("example-plugin")
+    with open(os.path.join(folder, "kept.json"), "w") as data_file:
+        data_file.write("{}")
+
+    assert plugin_data_folder("example-plugin") == folder
+    assert os.listdir(folder) == ["kept.json"]
+
+
+@pytest.mark.skipif(
+    sys.platform == "win32", reason="POSIX file permissions are not available"
+)
+def test_data_folder_is_only_accessible_by_the_user(data_folder):
+    folder = plugin_data_folder("example-plugin")
+
+    assert stat.S_IMODE(os.stat(folder).st_mode) & 0o077 == 0
+    parent_mode = stat.S_IMODE(os.stat(os.path.dirname(folder)).st_mode)
+    assert parent_mode & 0o077 == 0
+
+
+def test_plugins_get_their_own_data_folder(data_folder):
+    example_folder = plugin_data_folder("example-plugin")
+    other_folder = plugin_data_folder("other-plugin")
+
+    assert example_folder != other_folder
+    assert sorted(os.listdir(data_folder / "plugin-data")) == [
+        "example-plugin",
+        "other-plugin",
+    ]
+
+
+def test_data_folder_does_not_touch_the_configuration_folder(
+    config_folder, data_folder
+):
+    plugin_data_folder("example-plugin")
+
+    assert not os.path.exists(plugin_config_folder())
+
+
+@pytest.mark.parametrize(
+    "plugin_name", ["../escape", "folder/name", "UPPER", "-dash", ""]
+)
+def test_unsafe_plugin_names_have_no_data_folder(data_folder, plugin_name):
+    with pytest.raises(ValueError, match="Invalid plugin name"):
+        plugin_data_folder(plugin_name)
+
+    assert not os.path.exists(data_folder)
+
+
+def test_settings_class_knows_its_data_folder(data_folder):
+    folder = ExamplePluginSettings.data_folder()
+
+    assert folder == plugin_data_folder("example-plugin")
+    assert os.path.isdir(folder)
+    assert OtherPluginSettings.data_folder() != folder
+
+
+def test_settings_instance_uses_the_same_data_folder(config_folder, data_folder):
+    settings = ExamplePluginSettings.load()
+
+    assert settings.data_folder() == ExamplePluginSettings.data_folder()
+
+
+def test_subclass_without_its_own_name_shares_the_data_folder(data_folder):
+    class InheritingSettings(ExamplePluginSettings):
+        pass
+
+    assert InheritingSettings.data_folder() == ExamplePluginSettings.data_folder()

tests/plugin_fixtures.py

@@ -0,0 +1,85 @@
+# Mobile Verification Toolkit (MVT)
+# Copyright (c) 2021-2026 The MVT Authors.
+# Use of this software is governed by the MVT License 1.1 that can be found at
+#   https://license.mvt.re/1.1/
+
+"""Helpers building throwaway plugin distributions for the tests.
+
+Some plugin behaviour only shows up in a fresh interpreter: what an import
+executes, and what a plugin sees when MVT is imported before or after it.
+These helpers write an importable distribution with a real entry point and
+run a script against it in a subprocess, with a temporary home so that the
+subprocess cannot touch the configuration of whoever runs the tests.
+"""
+
+import os
+import subprocess
+import sys
+from pathlib import Path
+from typing import Optional
+
+FIXTURE_COMMAND_NAME = "fixture-plugin"
+FIXTURE_MODULE_NAME = "fixture_cli_plugin"
+FIXTURE_DISTRIBUTION_NAME = "fixture-cli-plugin"
+
+
+def write_cli_plugin_distribution(
+    site_path: Path,
+    entry_point_group: str,
+    module_source: str,
+) -> Path:
+    """Write a distribution registering a CLI plugin entry point.
+
+    :param site_path: Folder to write the distribution into, to be added to
+                      the import path of the interpreter loading it.
+    :param entry_point_group: Entry-point group to register the command in.
+    :param module_source: Source of the plugin module, which must define a
+                          Click command named `cli`.
+    :returns: The folder the distribution was written to.
+    """
+    site_path.mkdir(parents=True, exist_ok=True)
+    (site_path / f"{FIXTURE_MODULE_NAME}.py").write_text(
+        module_source, encoding="utf-8"
+    )
+
+    dist_info = (
+        site_path / f"{FIXTURE_DISTRIBUTION_NAME.replace('-', '_')}-1.0.dist-info"
+    )
+    dist_info.mkdir(exist_ok=True)
+    (dist_info / "METADATA").write_text(
+        f"Metadata-Version: 2.1\nName: {FIXTURE_DISTRIBUTION_NAME}\nVersion: 1.0\n",
+        encoding="utf-8",
+    )
+    (dist_info / "entry_points.txt").write_text(
+        f"[{entry_point_group}]\n{FIXTURE_COMMAND_NAME} = {FIXTURE_MODULE_NAME}:cli\n",
+        encoding="utf-8",
+    )
+    return site_path
+
+
+def run_isolated_python(
+    script: str,
+    home: Path,
+    site_path: Optional[Path] = None,
+    **environment: str,
+) -> subprocess.CompletedProcess:
+    """Run a script in a fresh interpreter with its own configuration folder.
+
+    Importing MVT writes its configuration file, so the subprocess gets a
+    temporary home and no MVT environment variables from the test session.
+    """
+    isolated_environment = {
+        key: value for key, value in os.environ.items() if not key.startswith("MVT_")
+    }
+    isolated_environment["HOME"] = str(home)
+    isolated_environment["XDG_CONFIG_HOME"] = str(home / "config")
+    if site_path is not None:
+        isolated_environment["PYTHONPATH"] = str(site_path)
+    isolated_environment.update(environment)
+
+    return subprocess.run(
+        [sys.executable, "-c", script],
+        capture_output=True,
+        text=True,
+        env=isolated_environment,
+    )

tests/test_cli_entry_points.py

@@ -0,0 +1,215 @@
+# Mobile Verification Toolkit (MVT)
+# Copyright (c) 2021-2026 The MVT Authors.
+# Use of this software is governed by the MVT License 1.1 that can be found at
+#   https://license.mvt.re/1.1/
+
+import sys
+from types import SimpleNamespace
+
+import click
+import pytest
+
+import mvt.android
+import mvt.ios
+from mvt.android.cli import cli as android_cli
+from mvt.android.cli import main as android_main
+from mvt.common.cli_plugins import ANDROID_CLI_PLUGIN_GROUP, IOS_CLI_PLUGIN_GROUP
+from mvt.ios.cli import cli as ios_cli
+from mvt.ios.cli import main as ios_main
+
+from .plugin_fixtures import (
+    FIXTURE_COMMAND_NAME,
+    run_isolated_python,
+    write_cli_plugin_distribution,
+)
+
+MARKER_PLUGIN_TEMPLATE = """
+import os
+
+import click
+
+# Touched when this module is imported, so a test can tell whether loading MVT
+# executed the plugin.
+open(os.environ["FIXTURE_PLUGIN_MARKER"], "a").close()
+
+
+@click.command()
+def cli():
+    click.echo("fixture plugin ran")
+"""
+
+PROGRAMS = {
+    "mvt-ios": (mvt.ios, ios_cli, IOS_CLI_PLUGIN_GROUP),
+    "mvt-android": (mvt.android, android_cli, ANDROID_CLI_PLUGIN_GROUP),
+}
+
+
+@pytest.fixture
+def restore_cli_commands():
+    """Undo the plugin registration main() performs on the shared CLI groups."""
+    originals = {
+        program: dict(group.commands) for program, (_, group, _) in PROGRAMS.items()
+    }
+    yield
+    for program, (_, group, _) in PROGRAMS.items():
+        group.commands.clear()
+        group.commands.update(originals[program])
+        if hasattr(group, "_mvt_external_command_sources"):
+            delattr(group, "_mvt_external_command_sources")
+
+
+def _install_fixture_entry_point(monkeypatch, entry_point_group, command):
+    def entry_points(*, group):
+        if group != entry_point_group:
+            return []
+        return [
+            SimpleNamespace(
+                name=FIXTURE_COMMAND_NAME,
+                value="fixture_cli_plugin:cli",
+                load=lambda: command,
+                dist=SimpleNamespace(
+                    metadata={"Name": "fixture-cli-plugin"}, version="1.0"
+                ),
+            )
+        ]
+
+    monkeypatch.setattr(
+        "mvt.common.cli_plugins.importlib.metadata.entry_points", entry_points
+    )
+
+
+def _offline_argv(program, *arguments):
+    """Build an argument list which keeps the CLI from checking for updates."""
+    return [
+        program,
+        "--disable-update-check",
+        "--disable-indicator-update-check",
+        *arguments,
+    ]
+
+
+@pytest.mark.parametrize("program", sorted(PROGRAMS))
+def test_main_registers_installed_plugins_before_running_the_cli(
+    program, monkeypatch, capsys, restore_cli_commands
+):
+    package, group, entry_point_group = PROGRAMS[program]
+
+    @click.command()
+    def fixture_command():
+        click.echo("fixture plugin ran")
+
+    _install_fixture_entry_point(monkeypatch, entry_point_group, fixture_command)
+    monkeypatch.setattr(sys, "argv", _offline_argv(program, FIXTURE_COMMAND_NAME))
+
+    with pytest.raises(SystemExit) as exit_info:
+        package.main()
+
+    assert exit_info.value.code == 0
+    assert "fixture plugin ran" in capsys.readouterr().out
+    assert FIXTURE_COMMAND_NAME in group.commands
+
+
+@pytest.mark.parametrize("program", sorted(PROGRAMS))
+def test_main_completes_plugin_command_names(
+    program, monkeypatch, capsys, restore_cli_commands
+):
+    package, _, entry_point_group = PROGRAMS[program]
+
+    @click.command()
+    def fixture_command():
+        pass
+
+    _install_fixture_entry_point(monkeypatch, entry_point_group, fixture_command)
+    complete_variable = f"_{program.upper().replace('-', '_')}_COMPLETE"
+    monkeypatch.setenv(complete_variable, "bash_complete")
+    monkeypatch.setenv("COMP_WORDS", f"{program} fixture")
+    monkeypatch.setenv("COMP_CWORD", "1")
+    monkeypatch.setattr(sys, "argv", [program])
+
+    with pytest.raises(SystemExit):
+        package.main()
+
+    assert f"plain,{FIXTURE_COMMAND_NAME}" in capsys.readouterr().out
+
+
+@pytest.mark.parametrize("program", sorted(PROGRAMS))
+def test_main_still_loads_commands_from_a_file(
+    program, monkeypatch, capsys, tmp_path, restore_cli_commands
+):
+    package, _, entry_point_group = PROGRAMS[program]
+    command_path = tmp_path / "case_summary.py"
+    command_path.write_text(
+        "import click\n"
+        "\n"
+        "\n"
+        '@click.command("case-summary")\n'
+        "def cli():\n"
+        '    click.echo("case summary ran")\n',
+        encoding="utf-8",
+    )
+    _install_fixture_entry_point(
+        monkeypatch, entry_point_group, click.Command("unused")
+    )
+    monkeypatch.setattr(
+        sys,
+        "argv",
+        _offline_argv(program, "--load-command", str(command_path), "case-summary"),
+    )
+
+    with pytest.raises(SystemExit) as exit_info:
+        package.main()
+
+    assert exit_info.value.code == 0
+    assert "case summary ran" in capsys.readouterr().out
+
+
+def test_the_console_script_targets_are_importable():
+    # [project.scripts] points at these, so they must stay on the packages.
+    assert mvt.ios.main is ios_main
+    assert mvt.android.main is android_main
+
+
+def test_importing_mvt_does_not_run_installed_plugins(tmp_path):
+    site_path = write_cli_plugin_distribution(
+        tmp_path / "site", IOS_CLI_PLUGIN_GROUP, MARKER_PLUGIN_TEMPLATE
+    )
+    marker = tmp_path / "plugin-imported"
+
+    result = run_isolated_python(
+        "import mvt.ios.cli\nimport mvt.android.cli\nprint('imported')",
+        home=tmp_path / "home",
+        site_path=site_path,
+        FIXTURE_PLUGIN_MARKER=str(marker),
+    )
+
+    assert result.returncode == 0, result.stderr
+    assert "imported" in result.stdout
+    assert not marker.exists()
+
+
+def test_registering_the_plugins_runs_the_entry_point(tmp_path):
+    site_path = write_cli_plugin_distribution(
+        tmp_path / "site", IOS_CLI_PLUGIN_GROUP, MARKER_PLUGIN_TEMPLATE
+    )
+    marker = tmp_path / "plugin-imported"
+
+    result = run_isolated_python(
+        "import click\n"
+        "from mvt.common.cli_plugins import (\n"
+        "    IOS_CLI_PLUGIN_GROUP,\n"
+        "    BrokenPluginCommand,\n"
+        "    register_installed_cli_commands,\n"
+        ")\n"
+        "group = click.Group()\n"
+        "register_installed_cli_commands(group, IOS_CLI_PLUGIN_GROUP)\n"
+        f"command = group.commands[{FIXTURE_COMMAND_NAME!r}]\n"
+        "assert not isinstance(command, BrokenPluginCommand), command.help\n"
+        "print('registered')\n",
+        home=tmp_path / "home",
+        site_path=site_path,
+        FIXTURE_PLUGIN_MARKER=str(marker),
+    )
+
+    assert result.returncode == 0, result.stderr
+    assert "registered" in result.stdout
+    assert marker.exists()