diff --git a/packages/appium/lib/appium.js b/packages/appium/lib/appium.js
index 4acb54ca9..c6fa3c274 100644
--- a/packages/appium/lib/appium.js
+++ b/packages/appium/lib/appium.js
@@ -53,6 +53,7 @@ class AppiumDriver extends BaseDriver {
     // It is not recommended to access this property directly from the outside
     this.pendingDrivers = {};
 
+    /** @type {PluginExtensionClass[]} */
     this.pluginClasses = []; // list of which plugins are active
     this.sessionPlugins = {}; // map of sessions to actual plugin instances per session
     this.sessionlessPlugins = []; // some commands are sessionless, so we need a set of plugins for them
@@ -61,9 +62,12 @@ class AppiumDriver extends BaseDriver {
     updateBuildInfo();
   }
 
-  /** @type {DriverConfig|undefined} */
+  /** @type {import('./driver-config').default|undefined} */
   driverConfig;
 
+  /** @type {import('express').Express|undefined} */
+  server;
+
   /**
    * Cancel commands queueing for the umbrella Appium driver
    */
@@ -670,3 +674,23 @@ export class NoDriverProxyCommandError extends Error {
 }
 
 export { AppiumDriver };
+
+
+/**
+ * @typedef {Object} StaticExtMembers
+ * @property {(app: import('express').Express, httpServer: import('http').Server) => import('type-fest').Promisable<void>} [updateServer]
+ * @property {import('@appium/base-driver').MethodMap} [newMethodMap]
+ */
+
+/**
+ * @typedef {Object} StaticPluginMembers
+ * @property {string} pluginName
+ */
+
+/**
+ * @typedef {import('type-fest').Class<unknown> & StaticPluginMembers & StaticExtMembers} PluginExtensionClass
+ */
+
+/**
+ * @typedef {import('type-fest').Class<unknown> & StaticExtMembers} DriverExtensionClass
+ */
diff --git a/packages/appium/lib/cli/args.js b/packages/appium/lib/cli/args.js
index ac1970712..1304a215c 100644
--- a/packages/appium/lib/cli/args.js
+++ b/packages/appium/lib/cli/args.js
@@ -1,7 +1,6 @@
 // @ts-check
 
 // @ts-ignore
-import { DEFAULT_BASE_PATH } from '@appium/base-driver';
 import _ from 'lodash';
 import DriverConfig from '../driver-config';
 import { APPIUM_HOME, DRIVER_TYPE, INSTALL_TYPES, PLUGIN_TYPE } from '../extension-config';
@@ -175,13 +174,7 @@ function makeRunArgs (type) {
  */
 function getServerArgs () {
   return new Map([
-    ...toParserArgs({
-      overrides: {
-        basePath: {
-          default: DEFAULT_BASE_PATH
-        },
-      }
-    }),
+    ...toParserArgs(),
     ...serverArgsDisallowedInConfig,
   ]);
 }
@@ -195,21 +188,31 @@ const serverArgsDisallowedInConfig = new Map([
     ['--shell'],
     {
       required: false,
-      default: null,
       help: 'Enter REPL mode',
-      action: 'store_true',
+      action: 'store_const',
+      const: true,
       dest: 'shell',
     },
   ],
+  [
+    ['--show-build-info'],
+    {
+      dest: 'showBuildInfo',
+      action: 'store_const',
+      const: true,
+      required: false,
+      help: 'Show info about the Appium build and exit',
+    },
+  ],
   [
     ['--show-config'],
     {
-      default: false,
       dest: 'showConfig',
-      action: 'store_true',
+      action: 'store_const',
+      const: true,
       required: false,
-      help: 'Show info about the appium server configuration and exit',
-    },
+      help: 'Show the current Appium configuration and exit',
+    }
   ],
   [
     ['--config'],
diff --git a/packages/appium/lib/cli/parser.js b/packages/appium/lib/cli/parser.js
index 354ae88e9..8fb5c5fe5 100644
--- a/packages/appium/lib/cli/parser.js
+++ b/packages/appium/lib/cli/parser.js
@@ -146,7 +146,7 @@ class ArgParser {
     return _.reduce(
       args,
       (unpacked, value, key) => {
-        if (hasArgSpec(key)) {
+        if (!_.isUndefined(value) && hasArgSpec(key)) {
           const {dest} = /** @type {import('../schema/arg-spec').ArgSpec} */(getArgSpec(key));
           _.set(unpacked, dest, value);
         } else {
diff --git a/packages/appium/lib/config.js b/packages/appium/lib/config.js
index 16c11a3ec..82b5753f2 100644
--- a/packages/appium/lib/config.js
+++ b/packages/appium/lib/config.js
@@ -1,3 +1,6 @@
+// @ts-check
+
+/* eslint-disable no-console */
 import _ from 'lodash';
 import { mkdirp, system, fs } from '@appium/support';
 import axios from 'axios';
@@ -22,7 +25,7 @@ const BUILD_INFO = {
 };
 
 function getNodeVersion () {
-  return semver.coerce(process.version);
+  return /** @type {import('semver').SemVer} */(semver.coerce(process.version));
 }
 
 async function updateBuildInfo (useGithubApiFallback = false) {
@@ -42,7 +45,7 @@ async function updateBuildInfo (useGithubApiFallback = false) {
  *
  * This is needed because Appium cannot assume `package.json` and `.git` are in the same
  * directory.  Monorepos, see?
- * @returns {string|void} Path to dir or `undefined` if not found
+ * @returns {Promise<string|undefined>} Path to dir or `undefined` if not found
  */
 async function findGitRoot () {
   return await findUp(GIT_META_ROOT, {cwd: rootDir, type: 'directory'});
@@ -80,6 +83,11 @@ async function getGitRev (useGithubApiFallback = false) {
   return null;
 }
 
+/**
+ * @param {string} commitSha
+ * @param {boolean} [useGithubApiFallback]
+ * @returns {Promise<number?>}
+ */
 async function getGitTimestamp (commitSha, useGithubApiFallback = false) {
   const gitRoot = await findGitRoot();
   if (gitRoot) {
@@ -144,30 +152,30 @@ function warnNodeDeprecations () {
   // }
 }
 
-async function showConfig () {
+async function showBuildInfo () {
   await updateBuildInfo(true);
   console.log(JSON.stringify(getBuildInfo())); // eslint-disable-line no-console
 }
 
 /**
  * Returns k/v pairs of server arguments which are _not_ the defaults.
- * @param {import('../types/types').ParsedArgs} args
- * @returns {Partial<import('../types/types').ParsedArgs>}
+ * @param {ParsedArgs} args
+ * @returns {Partial<ParsedArgs>}
  */
 function getNonDefaultServerArgs (args) {
   // hopefully these function names are descriptive enough
 
-  const typesDiffer = (dest) => typeof args[dest] !== typeof defaultsFromSchema[dest];
+  const typesDiffer = /** @param {string} dest */(dest) => typeof args[dest] !== typeof defaultsFromSchema[dest];
 
-  const defaultValueIsArray = (dest) => _.isArray(defaultsFromSchema[dest]);
+  const defaultValueIsArray = /** @param {string} dest */(dest) => _.isArray(defaultsFromSchema[dest]);
 
-  const argsValueIsArray = (dest) => _.isArray(args[dest]);
+  const argsValueIsArray = /** @param {string} dest */(dest) => _.isArray(args[dest]);
 
-  const arraysDiffer = (dest) => _.size(_.difference(args[dest], defaultsFromSchema[dest])) > 0;
+  const arraysDiffer = /** @param {string} dest */(dest) => _.gt(_.size(_.difference(args[dest], defaultsFromSchema[dest])), 0);
 
-  const valuesDiffer = (dest) => args[dest] !== defaultsFromSchema[dest];
+  const valuesDiffer = /** @param {string} dest */(dest) => args[dest] !== defaultsFromSchema[dest];
 
-  const defaultIsDefined = (dest) => !_.isUndefined(defaultsFromSchema[dest]);
+  const defaultIsDefined = /** @param {string} dest */(dest) => !_.isUndefined(defaultsFromSchema[dest]);
 
   // note that `_.overEvery` is like an "AND", and `_.overSome` is like an "OR"
 
@@ -209,6 +217,46 @@ function getNonDefaultServerArgs (args) {
   return _.pickBy(args, (__, key) => isNotDefault(key));
 }
 
+/**
+ * Compacts an object for {@link showConfig}:
+ * 1. Removes `subcommand` key/value
+ * 2. Removes `undefined` values
+ * 3. Removes empty objects (but not `false` values)
+ * Does not operate recursively.
+ */
+const compactConfig = _.partial(
+  _.omitBy,
+  _,
+  (value, key) => key === 'subcommand' || _.isUndefined(value) || (_.isObject(value) && _.isEmpty(value))
+);
+
+/**
+ * Shows a breakdown of the current config after CLI params, config file loaded & defaults applied.
+ *
+ * The actual shape of `preConfigParsedArgs` and `defaults` does not matter for the purposes of this function,
+ * but it's intended to be called with values of type {@link ParsedArgs} and `DefaultValues<true>`, respectively.
+ *
+ * @param {object} preConfigParsedArgs - Parsed CLI args (or param to `init()`) before config & defaults applied
+ * @param {import('./config-file').ReadConfigFileResult} configResult - Result of attempting to load a config file
+ * @param {object} defaults - Configuration defaults from schemas
+ */
+function showConfig (preConfigParsedArgs, configResult, defaults) {
+  console.log('Appium Configuration\n');
+  if (configResult.config) {
+    console.log(`via config file at ${configResult.filepath}:\n`);
+    console.dir(compactConfig(configResult.config));
+  } else {
+    console.log(`(no configuration file loaded)\n`);
+  }
+  console.log('via CLI or function call:\n');
+  console.dir(compactConfig(preConfigParsedArgs));
+  console.log('\nvia defaults:\n');
+  console.dir(compactConfig(defaults));
+}
+
+/**
+ * @param {string} tmpDir
+ */
 async function validateTmpDir (tmpDir) {
   try {
     await mkdirp(tmpDir);
@@ -219,7 +267,11 @@ async function validateTmpDir (tmpDir) {
 }
 
 export {
-  getBuildInfo, checkNodeOk, showConfig,
+  getBuildInfo, checkNodeOk, showBuildInfo,
   warnNodeDeprecations, validateTmpDir, getNonDefaultServerArgs,
-  getGitRev, APPIUM_VER, updateBuildInfo
+  getGitRev, APPIUM_VER, updateBuildInfo, showConfig
 };
+
+/**
+ * @typedef {import('../types/types').ParsedArgs} ParsedArgs
+ */
diff --git a/packages/appium/lib/extension-config.js b/packages/appium/lib/extension-config.js
index abc4ddad3..3f141bddb 100644
--- a/packages/appium/lib/extension-config.js
+++ b/packages/appium/lib/extension-config.js
@@ -270,7 +270,7 @@ export default class ExtensionConfig {
   /**
    * Loads extension and returns its main class
    * @param {string} extName
-   * @returns {(...args: any[]) => object }
+   * @returns {import('type-fest').Class<unknown>}
    */
   require (extName) {
     const {mainClass} = this.installedExtensions[extName];
diff --git a/packages/appium/lib/main.js b/packages/appium/lib/main.js
index ff4027742..fc03cff73 100755
--- a/packages/appium/lib/main.js
+++ b/packages/appium/lib/main.js
@@ -3,6 +3,7 @@
 // transpile:main
 // @ts-check
 
+import logger from './logger'; // logger needs to remain first of imports
 // @ts-ignore
 import { routeConfiguringFunction as makeRouter, server as baseServer } from '@appium/base-driver';
 import { logger as logFactory, util } from '@appium/support';
@@ -12,13 +13,12 @@ import { AppiumDriver } from './appium';
 import { driverConfig, pluginConfig, USE_ALL_PLUGINS } from './cli/args';
 import { runExtensionCommand } from './cli/extension';
 import { default as getParser, SERVER_SUBCOMMAND } from './cli/parser';
-import { APPIUM_VER, checkNodeOk, getGitRev, getNonDefaultServerArgs, showConfig, validateTmpDir, warnNodeDeprecations } from './config';
+import { APPIUM_VER, checkNodeOk, getGitRev, getNonDefaultServerArgs, showBuildInfo, validateTmpDir, warnNodeDeprecations, showConfig } from './config';
 import { readConfigFile } from './config-file';
 import { DRIVER_TYPE, PLUGIN_TYPE } from './extension-config';
 import registerNode from './grid-register';
-import logger from './logger'; // logger needs to remain first of imports
 import { init as logsinkInit } from './logsink';
-import { getDefaultsForSchema, validate } from './schema/schema';
+import { getDefaultsForSchema } from './schema/schema';
 import { inspect } from './utils';
 
 /**
@@ -32,14 +32,12 @@ async function preflightChecks (args, throwInsteadOfExit = false) {
     if (args.longStacktrace) {
       require('longjohn').async_trace_limit = -1;
     }
-    if (args.showConfig) {
-      await showConfig();
+    if (args.showBuildInfo) {
+      await showBuildInfo();
       process.exit(0);
     }
     warnNodeDeprecations();
 
-    validate(args);
-
     if (args.tmpDir) {
       await validateTmpDir(args.tmpDir);
     }
@@ -112,7 +110,7 @@ function logServerPort (address, port) {
  *
  * @param {Object} args - argparser parsed dict
  * @param {import('./plugin-config').default} pluginConfig - a plugin extension config
- * @returns {({pluginName: string} & ((...args: any[]) => unknown))[]}
+ * @returns {PluginExtensionClass[]}
  */
 function getActivePlugins (args, pluginConfig) {
   return _.compact(Object.keys(pluginConfig.installedExtensions).filter((pluginName) =>
@@ -121,7 +119,7 @@ function getActivePlugins (args, pluginConfig) {
   ).map((pluginName) => {
     try {
       logger.info(`Attempting to load plugin ${pluginName}...`);
-      const PluginClass = /** @type {{pluginName: string} & ((...args: any[]) => unknown)} */(pluginConfig.require(pluginName));
+      const PluginClass = /** @type {PluginExtensionClass} */(pluginConfig.require(pluginName));
 
       PluginClass.pluginName = pluginName; // store the plugin name on the class so it can be used later
       return PluginClass;
@@ -156,10 +154,22 @@ function getActiveDrivers (args, driverConfig) {
   }));
 }
 
+/**
+ * Gets a list of `updateServer` functions from all extensions
+ * @param {DriverExtensionClass[]} driverClasses
+ * @param {PluginExtensionClass[]} pluginClasses
+ * @returns {StaticExtMembers['updateServer'][]}
+ */
 function getServerUpdaters (driverClasses, pluginClasses) {
-  return [...driverClasses, ...pluginClasses].map((klass) => klass.updateServer).filter(Boolean);
+  return _.compact(_.map([...driverClasses, ...pluginClasses], 'updateServer'));
 }
 
+/**
+ * Makes a big `MethodMap` from all the little `MethodMap`s in the extensions
+ * @param {DriverExtensionClass[]} driverClasses
+ * @param {PluginExtensionClass[]} pluginClasses
+ * @returns {import('@appium/base-driver').MethodMap}
+ */
 function getExtraMethodMap (driverClasses, pluginClasses) {
   return [...driverClasses, ...pluginClasses].reduce(
     (map, klass) => ({...map, ...klass.newMethodMap}),
@@ -175,20 +185,27 @@ function getExtraMethodMap (driverClasses, pluginClasses) {
  * If `args` contains a non-empty `subcommand` which is not `server`, this function
  * will resolve with an empty object.
  *
- * @todo: Use generics/conditional types to specify return values.
+ * @param {ParsedArgs} [args] - Parsed args
+ * @returns {Promise<Partial<{appiumDriver: AppiumDriver, parsedArgs: ParsedArgs}>>}
  * @example
  * import {init, getSchema} from 'appium';
  * const options = {}; // config object
  * await init(options);
  * const schema = getSchema(); // entire config schema including plugins and drivers
- * @param {ParsedArgs} [args] - Parsed args
- * @returns {Promise<Partial<{appiumDriver: AppiumDriver, parsedArgs: ParsedArgs}>>}
  */
 async function init (args) {
   const parser = await getParser();
   let throwInsteadOfExit = false;
   /** @type {ParsedArgs} */
+  let preConfigParsedArgs;
+  /** @type {typeof preConfigParsedArgs & import('type-fest').AsyncReturnType<readConfigFile>['config']} */
   let parsedArgs;
+  /**
+   * This is a definition (instead of declaration) because TS can't figure out
+   * the value will be defined when it's used.
+   * @type {ReturnType<getDefaultsForSchema>}
+   */
+  let defaults = {};
   if (args) {
     // if we have a containing package instead of running as a CLI process,
     // that package might not appreciate us calling 'process.exit' willy-
@@ -198,29 +215,39 @@ async function init (args) {
       // but remove it since it's not a real server arg per se
       delete args.throwInsteadOfExit;
     }
-    parsedArgs = {...args, subcommand: args.subcommand ?? SERVER_SUBCOMMAND};
+    preConfigParsedArgs = {...args, subcommand: args.subcommand ?? SERVER_SUBCOMMAND};
   } else {
     // otherwise parse from CLI
-    parsedArgs = parser.parseArgs();
+    preConfigParsedArgs = parser.parseArgs();
   }
 
-  const configResult = await readConfigFile(parsedArgs.configFile);
+  const configResult = await readConfigFile(preConfigParsedArgs.configFile);
 
   if (!_.isEmpty(configResult.errors)) {
     throw new Error(`Errors in config file ${configResult.filepath}:\n ${configResult.reason ?? configResult.errors}`);
   }
 
+
   // merge config and apply defaults.
   // the order of precendece is:
   // 1. command line args
   // 2. config file
   // 3. defaults from config file.
-  if (parsedArgs.subcommand === SERVER_SUBCOMMAND) {
+  if (preConfigParsedArgs.subcommand === SERVER_SUBCOMMAND) {
+    defaults = getDefaultsForSchema(false);
+
+    if (preConfigParsedArgs.showConfig) {
+      showConfig(preConfigParsedArgs, configResult, defaults);
+      return {};
+    }
+
     parsedArgs = _.defaultsDeep(
-      parsedArgs,
+      preConfigParsedArgs,
       configResult.config?.server,
-      getDefaultsForSchema(false)
+      defaults
     );
+  } else {
+    parsedArgs = preConfigParsedArgs;
   }
 
   await logsinkInit(parsedArgs);
@@ -310,7 +337,6 @@ async function main (args) {
                 'to visit sites which could maliciously try to start Appium ' +
                 'sessions on your machine');
   }
-  // @ts-ignore
   appiumDriver.server = server;
   try {
     // configure as node on grid, if necessary
@@ -363,3 +389,15 @@ export { readConfigFile } from './config-file';
 /**
  * @typedef {import('../types/types').ParsedArgs} ParsedArgs
  */
+
+/**
+ * @typedef {import('./appium').PluginExtensionClass} PluginExtensionClass
+ */
+
+/**
+ * @typedef {import('./appium').DriverExtensionClass} DriverExtensionClass
+ */
+
+/**
+ * @typedef {import('./appium').StaticExtMembers} StaticExtMembers
+ */
diff --git a/packages/appium/lib/schema/cli-args.js b/packages/appium/lib/schema/cli-args.js
index ad2bf317f..777367db9 100644
--- a/packages/appium/lib/schema/cli-args.js
+++ b/packages/appium/lib/schema/cli-args.js
@@ -98,11 +98,9 @@ function makeDescription (schema) {
  * as understood by `argparse`.
  * @param {AppiumJSONSchema} subSchema - JSON schema for the option
  * @param {ArgSpec} argSpec - Argument spec tuple
- * @param {SubSchemaToArgDefOptions} [opts] - Options
  * @returns {[string[], import('argparse').ArgumentOptions]} Tuple of flag and options
  */
-function subSchemaToArgDef (subSchema, argSpec, opts = {}) {
-  const {overrides = {}} = opts;
+function subSchemaToArgDef (subSchema, argSpec) {
   let {
     type,
     appiumCliAliases,
@@ -110,7 +108,7 @@ function subSchemaToArgDef (subSchema, argSpec, opts = {}) {
     enum: enumValues,
   } = subSchema;
 
-  const {name, arg, dest} = argSpec;
+  const {name, arg} = argSpec;
 
   const aliases = [
     aliasToFlag(argSpec),
@@ -142,7 +140,8 @@ function subSchemaToArgDef (subSchema, argSpec, opts = {}) {
   switch (type) {
     // booleans do not have a type per `ArgumentOptions`, just an "action"
     case TYPENAMES.BOOLEAN: {
-      argOpts.action = 'store_true';
+      argOpts.action = 'store_const';
+      argOpts.const = true;
       break;
     }
 
@@ -227,16 +226,6 @@ function subSchemaToArgDef (subSchema, argSpec, opts = {}) {
     }
   }
 
-  // overrides override anything we computed here.  usually this involves "custom types",
-  // which are really just transform functions.
-  argOpts = _.merge(
-    argOpts,
-    /** should the override keys correspond to the prop name or the prop dest?
-     * the prop dest is computed by {@link aliasToDest}.
-     */
-    overrides[dest] ?? {},
-  );
-
   return [aliases, argOpts];
 }
 
@@ -244,32 +233,19 @@ function subSchemaToArgDef (subSchema, argSpec, opts = {}) {
  * Converts the finalized, flattened schema representation into
  * ArgumentDefinitions for handoff to `argparse`.
  *
- * @param {ToParserArgsOptions} opts - Options
  * @throws If schema has not been added to ajv (via `finalizeSchema()`)
  * @returns {import('../cli/args').ArgumentDefinitions} A map of arryas of
  * aliases to `argparse` arguments; empty if no schema found
  */
-export function toParserArgs (opts = {}) {
+export function toParserArgs () {
   const flattened = flattenSchema().filter(({schema}) => !schema.appiumCliIgnored);
   return new Map(
     _.map(flattened, ({schema, argSpec}) =>
-      subSchemaToArgDef(schema, argSpec, opts),
+      subSchemaToArgDef(schema, argSpec),
     ),
   );
 }
 
-/**
- * Options for {@link toParserArgs}
- * @typedef {SubSchemaToArgDefOptions} ToParserArgsOptions
- */
-
-/**
- * Options for {@link subSchemaToArgDef}.
- * @typedef {Object} SubSchemaToArgDefOptions
- * @property {string} [prefix] - The prefix to use for the flag, if any
- * @property {{[key: string]: import('argparse').ArgumentOptions}} [overrides] - An object of key/value pairs to override the default values
- */
-
 /**
  * @template T
  * @typedef {import('ajv/dist/types').FormatValidator<T>} FormatValidator<T>
diff --git a/packages/appium/test/cli/cli-helpers.js b/packages/appium/test/cli/cli-helpers.js
index 17c952474..aff32f755 100644
--- a/packages/appium/test/cli/cli-helpers.js
+++ b/packages/appium/test/cli/cli-helpers.js
@@ -143,6 +143,14 @@ export const installLocalExtension = _.curry(
  * @typedef {Error & AppiumRunErrorProps & import('../../lib/cli/npm').TeenProcessExecErrorProps} AppiumRunError
  */
 
+/**
+ * @typedef {import('../../lib/cli/npm').TeenProcessExecResult} TeenProcessExecResult
+ */
+
+/**
+ * @typedef {import('../../lib/cli/npm').TeenProcessExecError} TeenProcessExecError
+ */
+
 /**
  * Wraps the error returned by {@link exec}.
  * @typedef {Object} AppiumRunErrorProps
diff --git a/packages/appium/test/config-specs.js b/packages/appium/test/config-specs.js
index db771a962..55307b11b 100644
--- a/packages/appium/test/config-specs.js
+++ b/packages/appium/test/config-specs.js
@@ -1,22 +1,61 @@
+// @ts-check
+
 // transpile:mocha
-import _ from 'lodash';
 import sinon from 'sinon';
 import getParser from '../lib/cli/parser';
-import { checkNodeOk, getBuildInfo, getNonDefaultServerArgs, showConfig, validateTmpDir, warnNodeDeprecations } from '../lib/config';
+import { checkNodeOk, getBuildInfo, getNonDefaultServerArgs, showBuildInfo, showConfig, validateTmpDir, warnNodeDeprecations } from '../lib/config';
 import logger from '../lib/logger';
 import { getDefaultsForSchema, resetSchema, registerSchema, finalizeSchema } from '../lib/schema/schema';
 
 describe('Config', function () {
+  /** @type {import('sinon').SinonSandbox} */
+  let sandbox;
+
+  beforeEach(function () {
+    sandbox = sinon.createSandbox();
+  });
+
+  afterEach(function () {
+    sandbox.restore();
+  });
+
   describe('Appium config', function () {
-    describe('showConfig', function () {
-      before(function () {
-        sinon.spy(console, 'log');
-      });
-      it('should log the config to console', async function () {
+    /** @type {import('sinon').SinonSpy<[message?: any, ...extra: any[]],void>} */
+    let log;
+    /** @type {import('sinon').SinonSpy<[message?: any, ...extra: any[]],void>} */
+    let dir;
+    beforeEach(function () {
+      log = sandbox.spy(console, 'log');
+      dir = sandbox.spy(console, 'dir');
+    });
+
+    describe('showBuildInfo()', function () {
+      it('should log build info to console', async function () {
         const config = getBuildInfo();
-        await showConfig();
-        console.log.calledOnce.should.be.true; // eslint-disable-line no-console
-        console.log.getCall(0).args[0].should.contain(JSON.stringify(config)); // eslint-disable-line no-console
+        await showBuildInfo();
+        log.should.have.been.calledOnce;
+        log.firstCall.args.should.contain(JSON.stringify(config));
+      });
+    });
+
+    describe('showConfig', function () {
+      describe('when a config file is present', function () {
+        it('should dump the current Appium config', function () {
+          showConfig({foo: 'bar'}, {config: {server: {address: 'quux'}}}, {spam: 'food'});
+          log.should.have.been.calledWith('Appium Configuration\n');
+        });
+
+        it('should skip empty objects', function () {
+          showConfig({foo: 'bar', cows: {}, pigs: [], sheep: 0, ducks: false}, {config: {server: {address: 'quux'}}}, {spam: 'food'});
+          dir.should.have.been.calledWith({foo: 'bar', sheep: 0, ducks: false});
+        });
+      });
+
+      describe('when a config file is not present', function () {
+        it('should dump the current Appium config sans config file contents', function () {
+          showConfig({foo: 'bar'}, {}, {spam: 'food'});
+          log.should.have.been.calledWith('(no configuration file loaded)\n');
+        });
       });
     });
   });
@@ -27,11 +66,7 @@ describe('Config', function () {
       // need to be able to write to process.version
       // but also to have access to process methods
       // so copy them over to a writable object
-      let tempProcess = {};
-      for (let [prop, value] of _.toPairs(process)) {
-        tempProcess[prop] = value;
-      }
-      process = tempProcess; // eslint-disable-line no-global-assign
+      process = {...process}; // eslint-disable-line no-global-assign
     });
     after(function () {
       process = _process; // eslint-disable-line no-global-assign
@@ -45,6 +80,7 @@ describe('Config', function () {
         ];
         for (const version of unsupportedVersions) {
           it(`should fail if node is ${version}`, function () {
+            // @ts-expect-error
             process.version = version;
             checkNodeOk.should.throw();
           });
@@ -53,14 +89,17 @@ describe('Config', function () {
 
       describe('supported nodes', function () {
         it('should succeed if node is 12+', function () {
+          // @ts-expect-error
           process.version = 'v12.0.1';
           checkNodeOk.should.not.throw();
         });
         it('should succeed if node is 13+', function () {
+          // @ts-expect-error
           process.version = 'v13.6.0';
           checkNodeOk.should.not.throw();
         });
         it('should succeed if node is 14+', function () {
+          // @ts-expect-error
           process.version = 'v14.0.0';
           checkNodeOk.should.not.throw();
         });
@@ -70,17 +109,19 @@ describe('Config', function () {
     describe('warnNodeDeprecations', function () {
       let spy;
       before(function () {
-        spy = sinon.spy(logger, 'warn');
+        spy = sandbox.spy(logger, 'warn');
       });
       beforeEach(function () {
         spy.resetHistory();
       });
       it('should not log a warning if node is 8+', function () {
+        // @ts-expect-error
         process.version = 'v8.0.0';
         warnNodeDeprecations();
         logger.warn.callCount.should.equal(0);
       });
       it('should not log a warning if node is 9+', function () {
+        // @ts-expect-error
         process.version = 'v9.0.0';
         warnNodeDeprecations();
         logger.warn.callCount.should.equal(0);
@@ -142,6 +183,7 @@ describe('Config', function () {
       validateTmpDir('/private/if_you_run_with_sudo_this_wont_fail').should.be.rejectedWith(/could not ensure/);
     });
     it('should fail to use an undefined tmp dir', function () {
+      // @ts-expect-error
       validateTmpDir().should.be.rejectedWith(/could not ensure/);
     });
     it('should be able to use a tmp dir with correct permissions', function () {
@@ -165,7 +207,7 @@ describe('Config', function () {
     });
 
     it('should not fail if process.argv[1] is undefined', async function () {
-      process.argv[1] = undefined;
+      delete process.argv[1];
       let args = await getParser();
       args.prog.should.be.equal('appium');
     });
diff --git a/packages/appium/test/parser-specs.js b/packages/appium/test/parser-specs.js
index 18c05c30e..67de11e76 100644
--- a/packages/appium/test/parser-specs.js
+++ b/packages/appium/test/parser-specs.js
@@ -94,7 +94,7 @@ describe('parser', function () {
       });
 
       it('should parse --allow-insecure correctly', function () {
-        p.parseArgs([]).should.have.property('allowInsecure', undefined);
+        p.parseArgs([]).should.not.have.property('allowInsecure');
         p.parseArgs(['--allow-insecure', '']).allowInsecure.should.eql([]);
         p.parseArgs(['--allow-insecure', 'foo']).allowInsecure.should.eql(['foo']);
         p.parseArgs(['--allow-insecure', 'foo,bar']).allowInsecure.should.eql(['foo', 'bar']);
@@ -102,7 +102,7 @@ describe('parser', function () {
       });
 
       it('should parse --deny-insecure correctly', function () {
-        p.parseArgs([]).should.have.property('denyInsecure', undefined);
+        p.parseArgs([]).should.not.have.property('denyInsecure');
         p.parseArgs(['--deny-insecure', '']).denyInsecure.should.eql([]);
         p.parseArgs(['--deny-insecure', 'foo']).denyInsecure.should.eql(['foo']);
         p.parseArgs(['--deny-insecure', 'foo,bar']).denyInsecure.should.eql(['foo', 'bar']);
@@ -161,7 +161,7 @@ describe('parser', function () {
 
       it('should not yet apply defaults', function () {
         const args = p.parseArgs([]);
-        args.driver.fake.should.eql({sillyWebServerHost: undefined, sillyWebServerPort: undefined});
+        args.should.not.have.property('driver');
       });
 
       it('should nicely handle extensions w/ dashes in them', async function () {
diff --git a/packages/appium/test/schema/cli-args-specs.js b/packages/appium/test/schema/cli-args-specs.js
index 4f21dc1cb..9c8e71dee 100644
--- a/packages/appium/test/schema/cli-args-specs.js
+++ b/packages/appium/test/schema/cli-args-specs.js
@@ -20,7 +20,7 @@ describe('cli-args', function () {
         registerSchema(extType, extName, schema);
       }
       finalizeSchema();
-      return _.fromPairs([...toParserArgs(opts)]);
+      return _.fromPairs([...toParserArgs()]);
     }
 
     beforeEach(resetSchema);
@@ -40,10 +40,10 @@ describe('cli-args', function () {
             result = getArgs({schema, extName, extType});
           });
 
-          it('should return options containing `action` prop of `store_true` and no `type`', function () {
+          it('should return options containing `action` prop of `store_const` and no `type`', function () {
             expect(result['--plugin-blob-foo']).to.have.property(
               'action',
-              'store_true',
+              'store_const',
             );
           });
 
@@ -343,32 +343,6 @@ describe('cli-args', function () {
           });
         });
       });
-
-      describe('overrides', function () {
-        // this might be better some other way, IDK.  I suspect this will be rarely used.
-        // since extensions can't actually call `toParserArgs()`, they can't set `overrides` anyway.
-        it('should set them via "dest" key', function () {
-          const schema = {
-            properties: {
-              foo: {
-                type: 'string',
-              },
-            },
-            type: 'object',
-          };
-
-          const result = getArgs({
-            schema,
-            extName,
-            extType,
-            overrides: {'plugin.blob.foo': {enum: ['slug', 'snail']}},
-          });
-          expect(result['--plugin-blob-foo']).to.have.deep.property('enum', [
-            'slug',
-            'snail',
-          ]);
-        });
-      });
     });
   });
 });
diff --git a/packages/appium/types/types.d.ts b/packages/appium/types/types.d.ts
index 100ad44ab..db56359d5 100644
--- a/packages/appium/types/types.d.ts
+++ b/packages/appium/types/types.d.ts
@@ -160,6 +160,11 @@ interface MoreArgs {
   /**
    * If true, show the build info and exit
    */
+  showBuildInfo: boolean;
+
+  /**
+   * If true, show config and exit
+   */
   showConfig: boolean;
 
   /**