diff --git a/res/composer-lock-schema.json b/res/composer-lock-schema.json
new file mode 100644
index 000000000..b1ef31c2b
--- /dev/null
+++ b/res/composer-lock-schema.json
@@ -0,0 +1,101 @@
+{
+    "$schema": "https://json-schema.org/draft-04/schema#",
+    "title": "Composer Lock File",
+    "type": "object",
+    "required": [ "content-hash", "packages", "packages-dev" ],
+    "additionalProperties": true,
+    "properties": {
+        "_readme": {
+            "type": "array",
+            "items": {
+                "type": "string"
+            },
+            "description": "Informational text for humans reading the file"
+        },
+        "content-hash": {
+            "type": "string",
+            "description": "Hash of all relevant properties of the composer.json that was used to create this lock file."
+        },
+        "packages": {
+            "type": "array",
+            "description": "An array of packages that are required.",
+            "items": {
+                "$ref": "./composer-schema.json",
+                "required": ["name", "version"]
+            }
+        },
+        "packages-dev": {
+            "type": "array",
+            "description": "An array of packages that are required in require-dev.",
+            "items": {
+                "$ref": "./composer-schema.json"
+            }
+        },
+        "aliases": {
+            "type": "array",
+            "description": "Inline aliases defined in the root package.",
+            "items": {
+                "type": "object",
+                "required": [ "package", "version", "alias", "alias_normalized" ],
+                "properties": {
+                    "package": {
+                        "type": "string"
+                    },
+                    "version": {
+                        "type": "string"
+                    },
+                    "alias": {
+                        "type": "string"
+                    },
+                    "alias_normalized": {
+                        "type": "string"
+                    }
+                }
+            }
+        },
+        "minimum-stability": {
+            "type": "string",
+            "description": "The minimum-stability used to generate this lock file."
+        },
+        "stability-flags": {
+            "type": "object",
+            "description": "Root package stability flags changing the minimum-stability for specific packages.",
+            "additionalProperties": {
+                "type": "integer"
+            }
+        },
+        "prefer-stable": {
+            "type": "boolean",
+            "description": "Whether the --prefer-stable flag was used when building this lock file."
+        },
+        "prefer-lowest": {
+            "type": "boolean",
+            "description": "Whether the --prefer-lowest flag was used when building this lock file."
+        },
+        "platform": {
+            "type": "object",
+            "description": "Platform requirements of the root package.",
+            "additionalProperties": {
+                "type": "string"
+            }
+        },
+        "platform-dev": {
+            "type": "object",
+            "description": "Platform dev-requirements of the root package.",
+            "additionalProperties": {
+                "type": "string"
+            }
+        },
+        "platform-overrides": {
+            "type": "object",
+            "description": "Platform config overrides of the root package.",
+            "additionalProperties": {
+                "type": "string"
+            }
+        },
+        "plugin-api-version": {
+            "type": "string",
+            "description": "The composer-plugin-api version that was used to generate this lock file."
+        }
+    }
+}
diff --git a/res/composer-repository-schema.json b/res/composer-repository-schema.json
index adcc299d6..223f63abf 100644
--- a/res/composer-repository-schema.json
+++ b/res/composer-repository-schema.json
@@ -1,11 +1,12 @@
 {
     "$schema": "https://json-schema.org/draft-04/schema#",
-    "description": "A representation of packages metadata.",
+    "title": "Composer Package Repository",
     "type": "object",
     "oneOf": [
         { "required": [ "packages" ] },
         { "required": [ "providers" ] },
-        { "required": [ "provider-includes", "providers-url" ] }
+        { "required": [ "provider-includes", "providers-url" ] },
+        { "required": [ "metadata-url" ] }
     ],
     "properties": {
         "packages": {
@@ -13,19 +14,48 @@
             "description": "A hashmap of package names in the form of <vendor>/<name>.",
             "additionalProperties": { "$ref": "#/definitions/versions" }
         },
-        "providers-url": {
+        "metadata-url": {
             "type": "string",
-            "description": "Endpoint to retrieve provider data from, e.g. '/p/%package%$%hash%.json'."
+            "description": "Endpoint to retrieve package metadata data from, in Composer v2 format, e.g. '/p2/%package%.json'."
         },
-        "provider-includes": {
-            "type": "object",
-            "description": "A hashmap of provider listings.",
-            "additionalProperties": { "$ref": "#/definitions/provider" }
+        "available-packages": {
+            "type": "array",
+            "items": {
+                "type": "string"
+            },
+            "description": "If your repository only has a small number of packages, and you want to avoid serving many 404s, specify all the package names that your repository contains here."
         },
-        "providers": {
-            "type": "object",
-            "description": "A hashmap of package names in the form of <vendor>/<name>.",
-            "additionalProperties": { "$ref": "#/definitions/provider" }
+        "available-package-patterns": {
+            "type": "array",
+            "items": {
+                "type": "string"
+            },
+            "description": "If your repository only has a small number of packages, and you want to avoid serving many 404s, specify package name patterns containing wildcards (*) that your repository contains here."
+        },
+        "security-advisories": {
+            "type": "array",
+            "items": {
+                "type": "object",
+                "required": ["metadata", "api-url"],
+                "properties": {
+                    "metadata": {
+                        "type": "boolean",
+                        "description": "Whether metadata files contain security advisory data or whether it should always be queried using the API URL."
+                    },
+                    "api-url": {
+                        "type": "string",
+                        "description": "Endpoint to call to retrieve security advisories data."
+                    }
+                }
+            }
+        },
+        "metadata-changes-url": {
+            "type": "string",
+            "description": "Endpoint to retrieve package metadata updates from. This should receive a timestamp since last call to be able to return new changes. e.g. '/metadata/changes.json'."
+        },
+        "providers-api": {
+            "type": "string",
+            "description": "Endpoint to retrieve package names providing a given name from, e.g. '/providers/%package%.json'."
         },
         "notify-batch": {
             "type": "string",
@@ -35,9 +65,73 @@
             "type": "string",
             "description": "Endpoint that provides search capabilities, e.g. '/search.json?q=%query%&type=%type%'."
         },
+        "list": {
+            "type": "string",
+            "description": "Endpoint that provides a full list of packages present in the repository. It should accept an optional `?filter=xx` query param, which can contain `*` as wildcards matching any substring. e.g. '/list.json'."
+        },
+        "warnings": {
+            "type": "array",
+            "items": {
+                "type": "object",
+                "required": ["message", "versions"],
+                "properties": {
+                    "message": {
+                        "type": "string",
+                        "description": "A message that will be output by Composer as a warning when this source is consulted."
+                    },
+                    "versions": {
+                        "type": "string",
+                        "description": "A version constraint to limit to which Composer versions the warning should be shown."
+                    }
+                }
+            }
+        },
+        "infos": {
+            "type": "array",
+            "items": {
+                "type": "object",
+                "required": ["message", "versions"],
+                "properties": {
+                    "message": {
+                        "type": "string",
+                        "description": "A message that will be output by Composer as info when this source is consulted."
+                    },
+                    "versions": {
+                        "type": "string",
+                        "description": "A version constraint to limit to which Composer versions the info should be shown."
+                    }
+                }
+            }
+        },
+        "providers-url": {
+            "type": "string",
+            "description": "DEPRECATED: Endpoint to retrieve provider data from, e.g. '/p/%package%$%hash%.json'."
+        },
+        "provider-includes": {
+            "type": "object",
+            "description": "DEPRECATED: A hashmap of provider listings.",
+            "additionalProperties": { "$ref": "#/definitions/provider" }
+        },
+        "providers": {
+            "type": "object",
+            "description": "DEPRECATED: A hashmap of package names in the form of <vendor>/<name>.",
+            "additionalProperties": { "$ref": "#/definitions/provider" }
+        },
         "warning": {
             "type": "string",
-            "description": "A message that will be output by Composer as a warning when this source is consulted."
+            "description": "DEPRECATED: A message that will be output by Composer as a warning when this source is consulted."
+        },
+        "warning-versions": {
+            "type": "string",
+            "description": "DEPRECATED: A version constraint to limit to which Composer versions the warning should be shown."
+        },
+        "info": {
+            "type": "string",
+            "description": "DEPRECATED: A message that will be output by Composer as a info when this source is consulted."
+        },
+        "info-versions": {
+            "type": "string",
+            "description": "DEPRECATED: A version constraint to limit to which Composer versions the info should be shown."
         }
     },
     "definitions": {
diff --git a/res/composer-schema.json b/res/composer-schema.json
index ba62d21a4..9f76bc4b7 100644
--- a/res/composer-schema.json
+++ b/res/composer-schema.json
@@ -1,6 +1,6 @@
 {
     "$schema": "https://json-schema.org/draft-04/schema#",
-    "title": "Package",
+    "title": "Composer Package",
     "type": "object",
     "properties": {
         "name": {
diff --git a/src/Composer/Command/DiagnoseCommand.php b/src/Composer/Command/DiagnoseCommand.php
index cbd4a7c60..d06ad4497 100644
--- a/src/Composer/Command/DiagnoseCommand.php
+++ b/src/Composer/Command/DiagnoseCommand.php
@@ -19,6 +19,8 @@ use Composer\Config;
 use Composer\Downloader\TransportException;
 use Composer\IO\BufferIO;
 use Composer\Json\JsonFile;
+use Composer\Json\JsonValidationException;
+use Composer\Package\Locker;
 use Composer\Package\RootPackage;
 use Composer\Package\Version\VersionParser;
 use Composer\Pcre\Preg;
@@ -89,6 +91,12 @@ EOT
 
             $io->write('Checking composer.json: ', false);
             $this->outputResult($this->checkComposerSchema());
+
+            if ($composer->getLocker()->isLocked()) {
+                $io->write('Checking composer.lock: ', false);
+                $this->outputResult($this->checkComposerLockSchema($composer->getLocker()));
+            }
+
             $this->process = $composer->getLoop()->getProcessExecutor() ?? new ProcessExecutor($io);
         } else {
             $this->process = new ProcessExecutor($io);
@@ -267,6 +275,27 @@ EOT
         return true;
     }
 
+    /**
+     * @return string|true
+     */
+    private function checkComposerLockSchema(Locker $locker)
+    {
+        $json = $locker->getJsonFile();
+
+        try {
+            $json->validateSchema(JsonFile::LOCK_SCHEMA);
+        } catch (JsonValidationException $e) {
+            $output = '';
+            foreach ($e->getErrors() as $error) {
+                $output .= '<error>'.$error.'</error>'.PHP_EOL;
+            }
+
+            return trim($output);
+        }
+
+        return true;
+    }
+
     private function checkGit(): string
     {
         if (!function_exists('proc_open')) {
diff --git a/src/Composer/Json/JsonFile.php b/src/Composer/Json/JsonFile.php
index df4067e26..02ce5196c 100644
--- a/src/Composer/Json/JsonFile.php
+++ b/src/Composer/Json/JsonFile.php
@@ -32,6 +32,7 @@ class JsonFile
     public const LAX_SCHEMA = 1;
     public const STRICT_SCHEMA = 2;
     public const AUTH_SCHEMA = 3;
+    public const LOCK_SCHEMA = 4;
 
     /** @deprecated Use \JSON_UNESCAPED_SLASHES */
     public const JSON_UNESCAPED_SLASHES = 64;
@@ -41,6 +42,7 @@ class JsonFile
     public const JSON_UNESCAPED_UNICODE = 256;
 
     public const COMPOSER_SCHEMA_PATH = __DIR__ . '/../../../res/composer-schema.json';
+    public const LOCK_SCHEMA_PATH = __DIR__ . '/../../../res/composer-lock-schema.json';
 
     public const INDENT_DEFAULT = '    ';
 
@@ -228,8 +230,12 @@ class JsonFile
     {
         $isComposerSchemaFile = false;
         if (null === $schemaFile) {
-            $isComposerSchemaFile = true;
-            $schemaFile = self::COMPOSER_SCHEMA_PATH;
+            if ($schema === self::LOCK_SCHEMA) {
+                $schemaFile = self::LOCK_SCHEMA_PATH;
+            } else {
+                $isComposerSchemaFile = true;
+                $schemaFile = self::COMPOSER_SCHEMA_PATH;
+            }
         }
 
         // Prepend with file:// only when not using a special schema already (e.g. in the phar)
diff --git a/src/Composer/Package/Locker.php b/src/Composer/Package/Locker.php
index dc33a1123..5b5ec466c 100644
--- a/src/Composer/Package/Locker.php
+++ b/src/Composer/Package/Locker.php
@@ -73,6 +73,14 @@ class Locker
         $this->process = $process ?? new ProcessExecutor($io);
     }
 
+    /**
+     * @internal
+     */
+    public function getJsonFile(): JsonFile
+    {
+        return $this->lockFile;
+    }
+
     /**
      * Returns the md5 hash of the sorted content of the composer file.
      *