diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 474a1d2..a4fa299 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -35,3 +35,6 @@ jobs:
 
     - name: Run lints and tests
       run: ./script/test
+    
+    - name: Run Psalm for this specific PHP version
+      run: ./vendor/bin/psalm --php-version=${{ matrix.php-versions }}
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 67a6053..65788c3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Support for PHP 8
 - `whippet generate plugin` to generate a plugin based on our template repo https://github.com/dxw/wordpress-plugin-template/
+- Psalm compliance
 
 ### Removed
 - `whippet migrate` commands.
diff --git a/composer.json b/composer.json
index 891d108..b6b8b41 100644
--- a/composer.json
+++ b/composer.json
@@ -29,6 +29,7 @@
         "dxw/phar-install": "^1.1",
         "mikey179/vfsstream": "^1.6",
         "dxw/php-cs-fixer-config": "^2.0",
-        "kahlan/kahlan": "^5.1"
+        "kahlan/kahlan": "^5.1",
+        "vimeo/psalm": "^5.15"
     }
 }
diff --git a/composer.lock b/composer.lock
index 934f8ae..3853675 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "6b69ffa4d235186c6a47ad20e800c4df",
+    "content-hash": "bf29d8b7a0135e28b9f5f2bb31ae2a22",
     "packages": [
         {
             "name": "aura/autoload",
@@ -922,6 +922,172 @@
         }
     ],
     "packages-dev": [
+        {
+            "name": "amphp/amp",
+            "version": "v2.6.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/amphp/amp.git",
+                "reference": "9d5100cebffa729aaffecd3ad25dc5aeea4f13bb"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/amphp/amp/zipball/9d5100cebffa729aaffecd3ad25dc5aeea4f13bb",
+                "reference": "9d5100cebffa729aaffecd3ad25dc5aeea4f13bb",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.1"
+            },
+            "require-dev": {
+                "amphp/php-cs-fixer-config": "dev-master",
+                "amphp/phpunit-util": "^1",
+                "ext-json": "*",
+                "jetbrains/phpstorm-stubs": "^2019.3",
+                "phpunit/phpunit": "^7 | ^8 | ^9",
+                "psalm/phar": "^3.11@dev",
+                "react/promise": "^2"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "2.x-dev"
+                }
+            },
+            "autoload": {
+                "files": [
+                    "lib/functions.php",
+                    "lib/Internal/functions.php"
+                ],
+                "psr-4": {
+                    "Amp\\": "lib"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Daniel Lowrey",
+                    "email": "rdlowrey@php.net"
+                },
+                {
+                    "name": "Aaron Piotrowski",
+                    "email": "aaron@trowski.com"
+                },
+                {
+                    "name": "Bob Weinand",
+                    "email": "bobwei9@hotmail.com"
+                },
+                {
+                    "name": "Niklas Keller",
+                    "email": "me@kelunik.com"
+                }
+            ],
+            "description": "A non-blocking concurrency framework for PHP applications.",
+            "homepage": "https://amphp.org/amp",
+            "keywords": [
+                "async",
+                "asynchronous",
+                "awaitable",
+                "concurrency",
+                "event",
+                "event-loop",
+                "future",
+                "non-blocking",
+                "promise"
+            ],
+            "support": {
+                "irc": "irc://irc.freenode.org/amphp",
+                "issues": "https://github.com/amphp/amp/issues",
+                "source": "https://github.com/amphp/amp/tree/v2.6.2"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/amphp",
+                    "type": "github"
+                }
+            ],
+            "time": "2022-02-20T17:52:18+00:00"
+        },
+        {
+            "name": "amphp/byte-stream",
+            "version": "v1.8.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/amphp/byte-stream.git",
+                "reference": "acbd8002b3536485c997c4e019206b3f10ca15bd"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/amphp/byte-stream/zipball/acbd8002b3536485c997c4e019206b3f10ca15bd",
+                "reference": "acbd8002b3536485c997c4e019206b3f10ca15bd",
+                "shasum": ""
+            },
+            "require": {
+                "amphp/amp": "^2",
+                "php": ">=7.1"
+            },
+            "require-dev": {
+                "amphp/php-cs-fixer-config": "dev-master",
+                "amphp/phpunit-util": "^1.4",
+                "friendsofphp/php-cs-fixer": "^2.3",
+                "jetbrains/phpstorm-stubs": "^2019.3",
+                "phpunit/phpunit": "^6 || ^7 || ^8",
+                "psalm/phar": "^3.11.4"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.x-dev"
+                }
+            },
+            "autoload": {
+                "files": [
+                    "lib/functions.php"
+                ],
+                "psr-4": {
+                    "Amp\\ByteStream\\": "lib"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Aaron Piotrowski",
+                    "email": "aaron@trowski.com"
+                },
+                {
+                    "name": "Niklas Keller",
+                    "email": "me@kelunik.com"
+                }
+            ],
+            "description": "A stream abstraction to make working with non-blocking I/O simple.",
+            "homepage": "http://amphp.org/byte-stream",
+            "keywords": [
+                "amp",
+                "amphp",
+                "async",
+                "io",
+                "non-blocking",
+                "stream"
+            ],
+            "support": {
+                "irc": "irc://irc.freenode.org/amphp",
+                "issues": "https://github.com/amphp/byte-stream/issues",
+                "source": "https://github.com/amphp/byte-stream/tree/v1.8.1"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/amphp",
+                    "type": "github"
+                }
+            ],
+            "time": "2021-03-30T17:13:30+00:00"
+        },
         {
             "name": "composer/pcre",
             "version": "3.1.0",
@@ -1140,6 +1306,90 @@
             ],
             "time": "2022-02-25T21:32:43+00:00"
         },
+        {
+            "name": "dnoegel/php-xdg-base-dir",
+            "version": "v0.1.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/dnoegel/php-xdg-base-dir.git",
+                "reference": "8f8a6e48c5ecb0f991c2fdcf5f154a47d85f9ffd"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/dnoegel/php-xdg-base-dir/zipball/8f8a6e48c5ecb0f991c2fdcf5f154a47d85f9ffd",
+                "reference": "8f8a6e48c5ecb0f991c2fdcf5f154a47d85f9ffd",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.3.2"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "~7.0|~6.0|~5.0|~4.8.35"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "XdgBaseDir\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "implementation of xdg base directory specification for php",
+            "support": {
+                "issues": "https://github.com/dnoegel/php-xdg-base-dir/issues",
+                "source": "https://github.com/dnoegel/php-xdg-base-dir/tree/v0.1.1"
+            },
+            "time": "2019-12-04T15:06:13+00:00"
+        },
+        {
+            "name": "doctrine/deprecations",
+            "version": "1.1.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/doctrine/deprecations.git",
+                "reference": "4f2d4f2836e7ec4e7a8625e75c6aa916004db931"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/doctrine/deprecations/zipball/4f2d4f2836e7ec4e7a8625e75c6aa916004db931",
+                "reference": "4f2d4f2836e7ec4e7a8625e75c6aa916004db931",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.1 || ^8.0"
+            },
+            "require-dev": {
+                "doctrine/coding-standard": "^9",
+                "phpstan/phpstan": "1.4.10 || 1.10.15",
+                "phpstan/phpstan-phpunit": "^1.0",
+                "phpunit/phpunit": "^7.5 || ^8.5 || ^9.5",
+                "psalm/plugin-phpunit": "0.18.4",
+                "psr/log": "^1 || ^2 || ^3",
+                "vimeo/psalm": "4.30.0 || 5.12.0"
+            },
+            "suggest": {
+                "psr/log": "Allows logging deprecations via PSR-3 logger implementation"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Doctrine\\Deprecations\\": "lib/Doctrine/Deprecations"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "description": "A small layer on top of trigger_error(E_USER_DEPRECATED) or PSR-3 logging with options to disable all deprecations or selectively for packages.",
+            "homepage": "https://www.doctrine-project.org/",
+            "support": {
+                "issues": "https://github.com/doctrine/deprecations/issues",
+                "source": "https://github.com/doctrine/deprecations/tree/1.1.2"
+            },
+            "time": "2023-09-27T20:04:15+00:00"
+        },
         {
             "name": "doctrine/instantiator",
             "version": "1.5.0",
@@ -1284,6 +1534,168 @@
             },
             "time": "2023-09-13T12:53:23+00:00"
         },
+        {
+            "name": "felixfbecker/advanced-json-rpc",
+            "version": "v3.2.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/felixfbecker/php-advanced-json-rpc.git",
+                "reference": "b5f37dbff9a8ad360ca341f3240dc1c168b45447"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/felixfbecker/php-advanced-json-rpc/zipball/b5f37dbff9a8ad360ca341f3240dc1c168b45447",
+                "reference": "b5f37dbff9a8ad360ca341f3240dc1c168b45447",
+                "shasum": ""
+            },
+            "require": {
+                "netresearch/jsonmapper": "^1.0 || ^2.0 || ^3.0 || ^4.0",
+                "php": "^7.1 || ^8.0",
+                "phpdocumentor/reflection-docblock": "^4.3.4 || ^5.0.0"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^7.0 || ^8.0"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "AdvancedJsonRpc\\": "lib/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "ISC"
+            ],
+            "authors": [
+                {
+                    "name": "Felix Becker",
+                    "email": "felix.b@outlook.com"
+                }
+            ],
+            "description": "A more advanced JSONRPC implementation",
+            "support": {
+                "issues": "https://github.com/felixfbecker/php-advanced-json-rpc/issues",
+                "source": "https://github.com/felixfbecker/php-advanced-json-rpc/tree/v3.2.1"
+            },
+            "time": "2021-06-11T22:34:44+00:00"
+        },
+        {
+            "name": "felixfbecker/language-server-protocol",
+            "version": "v1.5.2",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/felixfbecker/php-language-server-protocol.git",
+                "reference": "6e82196ffd7c62f7794d778ca52b69feec9f2842"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/felixfbecker/php-language-server-protocol/zipball/6e82196ffd7c62f7794d778ca52b69feec9f2842",
+                "reference": "6e82196ffd7c62f7794d778ca52b69feec9f2842",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=7.1"
+            },
+            "require-dev": {
+                "phpstan/phpstan": "*",
+                "squizlabs/php_codesniffer": "^3.1",
+                "vimeo/psalm": "^4.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "LanguageServerProtocol\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "ISC"
+            ],
+            "authors": [
+                {
+                    "name": "Felix Becker",
+                    "email": "felix.b@outlook.com"
+                }
+            ],
+            "description": "PHP classes for the Language Server Protocol",
+            "keywords": [
+                "language",
+                "microsoft",
+                "php",
+                "server"
+            ],
+            "support": {
+                "issues": "https://github.com/felixfbecker/php-language-server-protocol/issues",
+                "source": "https://github.com/felixfbecker/php-language-server-protocol/tree/v1.5.2"
+            },
+            "time": "2022-03-02T22:36:06+00:00"
+        },
+        {
+            "name": "fidry/cpu-core-counter",
+            "version": "0.5.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/theofidry/cpu-core-counter.git",
+                "reference": "b58e5a3933e541dc286cc91fc4f3898bbc6f1623"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/theofidry/cpu-core-counter/zipball/b58e5a3933e541dc286cc91fc4f3898bbc6f1623",
+                "reference": "b58e5a3933e541dc286cc91fc4f3898bbc6f1623",
+                "shasum": ""
+            },
+            "require": {
+                "php": "^7.2 || ^8.0"
+            },
+            "require-dev": {
+                "fidry/makefile": "^0.2.0",
+                "phpstan/extension-installer": "^1.2.0",
+                "phpstan/phpstan": "^1.9.2",
+                "phpstan/phpstan-deprecation-rules": "^1.0.0",
+                "phpstan/phpstan-phpunit": "^1.2.2",
+                "phpstan/phpstan-strict-rules": "^1.4.4",
+                "phpunit/phpunit": "^9.5.26 || ^8.5.31",
+                "theofidry/php-cs-fixer-config": "^1.0",
+                "webmozarts/strict-phpunit": "^7.5"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-4": {
+                    "Fidry\\CpuCoreCounter\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Théo FIDRY",
+                    "email": "theo.fidry@gmail.com"
+                }
+            ],
+            "description": "Tiny utility to get the number of CPU cores.",
+            "keywords": [
+                "CPU",
+                "core"
+            ],
+            "support": {
+                "issues": "https://github.com/theofidry/cpu-core-counter/issues",
+                "source": "https://github.com/theofidry/cpu-core-counter/tree/0.5.1"
+            },
+            "funding": [
+                {
+                    "url": "https://github.com/theofidry",
+                    "type": "github"
+                }
+            ],
+            "time": "2022-12-24T12:35:10+00:00"
+        },
         {
             "name": "friendsofphp/php-cs-fixer",
             "version": "v3.26.1",
@@ -1664,192 +2076,458 @@
             "license": [
                 "MIT"
             ],
-            "description": "Create deep copies (clones) of your objects",
+            "description": "Create deep copies (clones) of your objects",
+            "keywords": [
+                "clone",
+                "copy",
+                "duplicate",
+                "object",
+                "object graph"
+            ],
+            "support": {
+                "issues": "https://github.com/myclabs/DeepCopy/issues",
+                "source": "https://github.com/myclabs/DeepCopy/tree/1.11.1"
+            },
+            "funding": [
+                {
+                    "url": "https://tidelift.com/funding/github/packagist/myclabs/deep-copy",
+                    "type": "tidelift"
+                }
+            ],
+            "time": "2023-03-08T13:26:56+00:00"
+        },
+        {
+            "name": "netresearch/jsonmapper",
+            "version": "v4.2.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/cweiske/jsonmapper.git",
+                "reference": "f60565f8c0566a31acf06884cdaa591867ecc956"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/cweiske/jsonmapper/zipball/f60565f8c0566a31acf06884cdaa591867ecc956",
+                "reference": "f60565f8c0566a31acf06884cdaa591867ecc956",
+                "shasum": ""
+            },
+            "require": {
+                "ext-json": "*",
+                "ext-pcre": "*",
+                "ext-reflection": "*",
+                "ext-spl": "*",
+                "php": ">=7.1"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "~7.5 || ~8.0 || ~9.0",
+                "squizlabs/php_codesniffer": "~3.5"
+            },
+            "type": "library",
+            "autoload": {
+                "psr-0": {
+                    "JsonMapper": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "OSL-3.0"
+            ],
+            "authors": [
+                {
+                    "name": "Christian Weiske",
+                    "email": "cweiske@cweiske.de",
+                    "homepage": "http://github.com/cweiske/jsonmapper/",
+                    "role": "Developer"
+                }
+            ],
+            "description": "Map nested JSON structures onto PHP classes",
+            "support": {
+                "email": "cweiske@cweiske.de",
+                "issues": "https://github.com/cweiske/jsonmapper/issues",
+                "source": "https://github.com/cweiske/jsonmapper/tree/v4.2.0"
+            },
+            "time": "2023-04-09T17:37:40+00:00"
+        },
+        {
+            "name": "nikic/php-parser",
+            "version": "v4.17.1",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/nikic/PHP-Parser.git",
+                "reference": "a6303e50c90c355c7eeee2c4a8b27fe8dc8fef1d"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/nikic/PHP-Parser/zipball/a6303e50c90c355c7eeee2c4a8b27fe8dc8fef1d",
+                "reference": "a6303e50c90c355c7eeee2c4a8b27fe8dc8fef1d",
+                "shasum": ""
+            },
+            "require": {
+                "ext-tokenizer": "*",
+                "php": ">=7.0"
+            },
+            "require-dev": {
+                "ircmaxell/php-yacc": "^0.0.7",
+                "phpunit/phpunit": "^6.5 || ^7.0 || ^8.0 || ^9.0"
+            },
+            "bin": [
+                "bin/php-parse"
+            ],
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "4.9-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "PhpParser\\": "lib/PhpParser"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "BSD-3-Clause"
+            ],
+            "authors": [
+                {
+                    "name": "Nikita Popov"
+                }
+            ],
+            "description": "A PHP parser written in PHP",
+            "keywords": [
+                "parser",
+                "php"
+            ],
+            "support": {
+                "issues": "https://github.com/nikic/PHP-Parser/issues",
+                "source": "https://github.com/nikic/PHP-Parser/tree/v4.17.1"
+            },
+            "time": "2023-08-13T19:53:39+00:00"
+        },
+        {
+            "name": "phar-io/manifest",
+            "version": "2.0.3",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/phar-io/manifest.git",
+                "reference": "97803eca37d319dfa7826cc2437fc020857acb53"
+            },
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+            "time": "2023-08-20T23:07:30+00:00"
+        },
+        {
+            "name": "webmozart/assert",
+            "version": "1.11.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/webmozarts/assert.git",
+                "reference": "11cb2199493b2f8a3b53e7f19068fc6aac760991"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/webmozarts/assert/zipball/11cb2199493b2f8a3b53e7f19068fc6aac760991",
+                "reference": "11cb2199493b2f8a3b53e7f19068fc6aac760991",
+                "shasum": ""
+            },
+            "require": {
+                "ext-ctype": "*",
+                "php": "^7.2 || ^8.0"
+            },
+            "conflict": {
+                "phpstan/phpstan": "<0.12.20",
+                "vimeo/psalm": "<4.6.1 || 4.6.2"
+            },
+            "require-dev": {
+                "phpunit/phpunit": "^8.5.13"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "1.10-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Webmozart\\Assert\\": "src/"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "Bernhard Schussek",
+                    "email": "bschussek@gmail.com"
+                }
+            ],
+            "description": "Assertions to validate method input/output with nice error messages.",
+            "keywords": [
+                "assert",
+                "check",
+                "validate"
+            ],
+            "support": {
+                "issues": "https://github.com/webmozarts/assert/issues",
+                "source": "https://github.com/webmozarts/assert/tree/1.11.0"
+            },
+            "time": "2022-06-03T18:03:27+00:00"
         }
     ],
     "aliases": [],
diff --git a/psalm.xml b/psalm.xml
new file mode 100644
index 0000000..d72d164
--- /dev/null
+++ b/psalm.xml
@@ -0,0 +1,20 @@
+<?xml version="1.0"?>
+<psalm
+    errorLevel="6"
+    resolveFromConfigFile="true"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://getpsalm.org/schema/config"
+    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+    findUnusedBaselineEntry="true"
+    findUnusedCode="true"
+>
+    <projectFiles>
+        <directory name="src" />
+        <ignoreFiles>
+            <directory name="vendor" />
+        </ignoreFiles>
+    </projectFiles>
+    <issueHandlers>
+        <PossiblyUnusedMethod errorLevel="suppress" />
+    </issueHandlers>
+</psalm>
diff --git a/script/test b/script/test
index 04b1efb..a0cbf2b 100755
--- a/script/test
+++ b/script/test
@@ -26,6 +26,9 @@ else
 	echo "==> Running php-cs-fixer..."
 	./vendor/bin/php-cs-fixer fix --dry-run -v --diff
 
+	echo "==> Running Psalm..."
+	./vendor/bin/psalm
+
 	echo "==> Running the tests..."
 	./vendor/bin/phpunit && ./vendor/bin/kahlan spec
 fi
diff --git a/src/Dependencies/Installer.php b/src/Dependencies/Installer.php
index ec3c4a8..f837db2 100644
--- a/src/Dependencies/Installer.php
+++ b/src/Dependencies/Installer.php
@@ -29,9 +29,7 @@ public function installAll()
 		$dependencies = [];
 
 		foreach (['themes', 'plugins'] as $type) {
-			foreach ($this->lockFile->getDependencies($type) as $dep) {
-				$dependencies[$type] = $this->lockFile->getDependencies($type);
-			}
+			$dependencies[$type] = $this->lockFile->getDependencies($type);
 		}
 
 		return $this->install($dependencies);
diff --git a/src/Files/WhippetJson.php b/src/Files/WhippetJson.php
index c3a427a..396ff43 100644
--- a/src/Files/WhippetJson.php
+++ b/src/Files/WhippetJson.php
@@ -2,6 +2,9 @@
 
 namespace Dxw\Whippet\Files;
 
+/**
+ * @psalm-suppress UnusedClass
+ */
 class WhippetJson extends Base
 {
 	public function getDependencies(/* string */ $type)
diff --git a/src/Files/WhippetLock.php b/src/Files/WhippetLock.php
index c5db5f8..bbcae3a 100644
--- a/src/Files/WhippetLock.php
+++ b/src/Files/WhippetLock.php
@@ -2,6 +2,9 @@
 
 namespace Dxw\Whippet\Files;
 
+/**
+ * @psalm-suppress UnusedClass
+ */
 class WhippetLock extends Base
 {
 	public function getDependencies(/* string */ $type)
diff --git a/src/Git/Git.php b/src/Git/Git.php
index 95a8c76..2c10b93 100644
--- a/src/Git/Git.php
+++ b/src/Git/Git.php
@@ -81,7 +81,7 @@ public function clone_no_checkout($repository)
 			return false;
 		}
 
-		$this->run_command("mv {$tmpdir}/.git {$this->repo_path}");
+		$this->run_command(['mv', $tmpdir . '/.git', $this->repo_path]);
 
 		return true;
 	}
diff --git a/src/Models/Inspection.php b/src/Models/Inspection.php
index d19b46f..87078c5 100644
--- a/src/Models/Inspection.php
+++ b/src/Models/Inspection.php
@@ -5,9 +5,21 @@
 // Responsible for wrapping data about dxw inspections in an object
 class Inspection
 {
+	/**
+	 * @psalm-suppress PossiblyUnusedProperty
+	 */
 	public $date;
+	/**
+	 * @psalm-suppress PossiblyUnusedProperty
+	 */
 	public $versions;
+	/**
+	 * @psalm-suppress PossiblyUnusedProperty
+	 */
 	public $result;
+	/**
+	 * @psalm-suppress PossiblyUnusedProperty
+	 */
 	public $url;
 
 	public function __construct($date_string, $versions, $result, $url)
diff --git a/src/Modules/Deploy.php b/src/Modules/Deploy.php
index 025e067..042384b 100644
--- a/src/Modules/Deploy.php
+++ b/src/Modules/Deploy.php
@@ -10,6 +10,7 @@ class Deploy
 	private $releases_dir;
 	private $shared_dir;
 	private $public_dir;
+	private $releases_manifest;
 
 	public function __construct($dir)
 	{
@@ -17,6 +18,7 @@ public function __construct($dir)
 		$this->releases_dir = "{$this->deploy_dir}/releases";
 		$this->shared_dir = "{$this->deploy_dir}/shared";
 		$this->public_dir = "";
+		$this->releases_manifest = [];
 	}
 
 	public function deploy($force, $keep, $public)
@@ -57,7 +59,7 @@ public function deploy($force, $keep, $public)
 				$release_number = 0;
 			}
 
-			$new_release = new Release($this->releases_dir, '', $release_number, $this->public_dir);
+			$new_release = new Release($this->releases_dir, $release_number, $this->public_dir);
 
 			// Make it.
 			$new_release->create($force, $public);
@@ -156,7 +158,7 @@ public function deploy($force, $keep, $public)
 				$this->releases_manifest[] = $release;
 				$this->save_releases_manifest();
 			}
-		} catch (Exception $e) {
+		} catch (\Exception $e) {
 			echo $e->getMessage();
 
 			exit(1);
diff --git a/src/Modules/Generate.php b/src/Modules/Generate.php
index ac43c75..624918f 100644
--- a/src/Modules/Generate.php
+++ b/src/Modules/Generate.php
@@ -8,6 +8,9 @@ class Generate
 
 	public function __construct()
 	{
+		/**
+		* @psalm-suppress UndefinedConstant
+		*/
 		$this->generators_dir = WHIPPET_ROOT.'/generators';
 	}
 
@@ -40,8 +43,8 @@ public function generate($thing, $options)
 	public function list_generators()
 	{
 		echo "Available generators:\n\n";
-		foreach ($this->get_generators() as $generator => $file) {
-			echo "  $generator\n";
+		foreach (array_keys($this->get_generators()) as $generator) {
+			echo strval($generator) . "\n";
 		}
 	}
 
diff --git a/src/Modules/Helpers/ManifestIo.php b/src/Modules/Helpers/ManifestIo.php
index 89b61fb..b05dc2d 100644
--- a/src/Modules/Helpers/ManifestIo.php
+++ b/src/Modules/Helpers/ManifestIo.php
@@ -118,6 +118,9 @@ private function update_plugins_lock()
 
 		$this->plugins_locked = new \stdClass();
 
+		/**
+		 * @psalm-suppress UndefinedThisPropertyFetch
+		 */
 		foreach (scandir($this->plugin_dir) as $dir) {
 			if ($dir[0] == '.') {
 				continue;
diff --git a/src/Modules/Plugin.php b/src/Modules/Plugin.php
index 1d85bad..bf3df6d 100644
--- a/src/Modules/Plugin.php
+++ b/src/Modules/Plugin.php
@@ -9,6 +9,7 @@ class Plugin extends \RubbishThorClone
 
 	private $plugins_manifest;
 	private $plugin_dir;
+	private $plugins_locked;
 
 	public function commands()
 	{
@@ -116,8 +117,8 @@ public function install($internal = false)
 			// Make sure every entry in the lockfile also appears in the manifest
 			$plugins_to_delete = array_keys((array) $this->plugins_locked);
 
-			foreach ($this->plugins_locked as $lock_dir => $lock_plugin) {
-				foreach ($this->plugins_manifest as $manifest_dir => $manifest_plugin) {
+			foreach (array_keys($this->plugins_locked) as $lock_dir) {
+				foreach (array_keys($this->plugins_manifest) as $manifest_dir) {
 					if ($lock_dir == $manifest_dir) {
 						unset($plugins_to_delete[array_search($lock_dir, $plugins_to_delete)]);
 					}
@@ -238,8 +239,8 @@ public function install($internal = false)
 		$gitignore = new \Dxw\Whippet\Git\Gitignore($this->project_dir);
 		$ignores = $gitignore->get_ignores();
 
-		foreach ($this->plugins_locked as $dir => $plugin) {
-			$plugin_dir = "/wp-content/plugins/{$dir}\n";
+		foreach (array_keys(get_object_vars($this->plugins_locked)) as $dir) {
+			$plugin_dir = "/wp-content/plugins/" . strval($dir) . "\n";
 
 			if (array_search($plugin_dir, $ignores) === false) {
 				$ignores[] = $plugin_dir;
diff --git a/src/Modules/Release.php b/src/Modules/Release.php
index b1e176f..1b78c2a 100644
--- a/src/Modules/Release.php
+++ b/src/Modules/Release.php
@@ -13,7 +13,7 @@ class Release
 	public $release_dir;
 	private $public_dir;
 
-	public function __construct($releases_dir, $message, $number, $public_dir)
+	public function __construct($releases_dir, $number, $public_dir)
 	{
 		$this->whippet_init();
 		$this->load_plugins_lock();
diff --git a/src/ProjectDirectory.php b/src/ProjectDirectory.php
index f79dbda..d49885a 100644
--- a/src/ProjectDirectory.php
+++ b/src/ProjectDirectory.php
@@ -25,6 +25,7 @@ public function __construct(/* string */ $path)
 		$this->path = $path;
 	}
 
+	#[\ReturnTypeWillChange]
 	public function __toString()
 	{
 		return $this->path;
diff --git a/src/Whippet.php b/src/Whippet.php
index 9cac9a2..cfdfbea 100644
--- a/src/Whippet.php
+++ b/src/Whippet.php
@@ -2,6 +2,9 @@
 
 namespace Dxw\Whippet;
 
+/**
+ * @psalm-suppress UnusedClass
+ */
 class Whippet extends \RubbishThorClone
 {
 	public function commands()
@@ -29,12 +32,12 @@ public function commands()
 		$this->command('deps SUBCOMMAND', 'Alias for dependencies');
 	}
 
-	public function plugins($plugin_command)
+	public function plugins()
 	{
 		(new Modules\Plugin())->start(array_slice($this->argv, 1));
 	}
 
-	public function theme($plugin_command)
+	public function theme()
 	{
 		(new Modules\Theme())->start(array_slice($this->argv, 1));
 	}
diff --git a/src/WhippetGenerator.php b/src/WhippetGenerator.php
index 3a51e4e..4c84836 100644
--- a/src/WhippetGenerator.php
+++ b/src/WhippetGenerator.php
@@ -6,7 +6,7 @@ abstract class WhippetGenerator
 {
 	use \Dxw\Whippet\Modules\Helpers\WhippetHelpers;
 
-	public function __construct($options)
+	public function __construct()
 	{
 		//
 		// This should not be called. You should declare your own constructor
@@ -14,8 +14,7 @@ public function __construct($options)
 		// requires.
 		//
 
-		trigger_error('Generators must declare a constructor', E_USER_FATAL);
-		die();
+		trigger_error('Generators must declare a constructor', E_USER_ERROR);
 	}
 
 	abstract public function generate();
diff --git a/vendor.phar b/vendor.phar
index b4b9ed0..1bee6a1 100644
Binary files a/vendor.phar and b/vendor.phar differ