2 files changed, 97 insertions, 12 deletions
diff --git a/src/Agent.App/Configuration/SkillLoader.cs b/src/Agent.App/Configuration/SkillLoader.cs
index 6923c12..bac1559 100644
--- a/src/Agent.App/Configuration/SkillLoader.cs
+++ b/src/Agent.App/Configuration/SkillLoader.cs
@@ -1,24 +1,109 @@
+using System.Text.RegularExpressions;
+using Agent.Core.Skills;
+using YamlDotNet.Serialization;
+using YamlDotNet.Serialization.NamingConventions;
+
 namespace Agent.App.Configuration;
 
 public static class SkillLoader
 {
-    public static string[] Load(string directory)
+    private static readonly Regex NamePattern = new("^[a-z0-9]([a-z0-9-]*[a-z0-9])?$", RegexOptions.Compiled);
+
+    public static IReadOnlyList<AgentSkill> Load(string directory)
     {
-        var paths = new List<string>();
-        paths.AddRange(Directory.EnumerateFiles(directory, "*.md", SearchOption.TopDirectoryOnly));
+        if (!Directory.Exists(directory)) return [];
+
+        var skills = new List<AgentSkill>();
+        var names = new HashSet<string>(StringComparer.Ordinal);
 
         foreach (string child in Directory.EnumerateDirectories(directory, "*", SearchOption.TopDirectoryOnly))
         {
             var info = new DirectoryInfo(child);
             if ((info.Attributes & FileAttributes.ReparsePoint) != 0) continue;
-            string standardSkill = Path.Combine(info.FullName, "SKILL.md");
-            if (File.Exists(standardSkill)) paths.Add(standardSkill);
+
+            string skillMd = Path.Combine(info.FullName, "SKILL.md");
+            if (!File.Exists(skillMd)) continue;
+
+            string dirName = info.Name;
+            string content = File.ReadAllText(skillMd);
+            var (frontmatter, body) = SplitFrontmatter(content);
+
+            if (frontmatter is null)
+                throw new SkillLoadException($"Skill '{dirName}': SKILL.md is missing YAML frontmatter.");
+
+            SkillFrontmatter fm = ParseFrontmatter(frontmatter);
+
+            ValidateSkill(dirName, fm, names);
+
+            skills.Add(new AgentSkill(
+                RootPath: info.FullName,
+                Name: fm.Name,
+                Description: fm.Description,
+                Instructions: body.Trim(),
+                License: fm.License,
+                Compatibility: fm.Compatibility,
+                Metadata: fm.Metadata,
+                AllowedTools: fm.AllowedTools));
+        }
+
+        return skills;
+    }
+
+    private static void ValidateSkill(string dirName, SkillFrontmatter fm, HashSet<string> names)
+    {
+        if (string.IsNullOrWhiteSpace(fm.Name))
+            throw new SkillLoadException($"Skill '{dirName}': name is required.");
+        if (fm.Name.Length < 1 || fm.Name.Length > 64)
+            throw new SkillLoadException($"Skill '{dirName}': name must be 1-64 characters.");
+        if (!NamePattern.IsMatch(fm.Name))
+            throw new SkillLoadException($"Skill '{dirName}': name must be lowercase alphanumeric with hyphens.");
+        if (!fm.Name.Equals(dirName, StringComparison.Ordinal))
+            throw new SkillLoadException($"Skill '{dirName}': name '{fm.Name}' does not match directory name.");
+        if (string.IsNullOrWhiteSpace(fm.Description))
+            throw new SkillLoadException($"Skill '{dirName}': description is required.");
+        if (fm.Description.Length > 1024)
+            throw new SkillLoadException($"Skill '{dirName}': description must be 1-1024 characters.");
+        if (!names.Add(fm.Name))
+            throw new SkillLoadException($"Duplicate skill name '{fm.Name}'.");
+    }
+
+    private static (string? Frontmatter, string Body) SplitFrontmatter(string content)
+    {
+        if (!content.StartsWith("---", StringComparison.Ordinal)) return (null, content);
+        int end = content.IndexOf("\n---", 3, StringComparison.Ordinal);
+        if (end < 0) return (null, content);
+        string frontmatter = content[3..end].Trim();
+        int bodyStart = end + 4;
+        if (bodyStart < content.Length && content[bodyStart] == '\r') bodyStart++;
+        if (bodyStart < content.Length && content[bodyStart] == '\n') bodyStart++;
+        string body = bodyStart < content.Length ? content[bodyStart..] : string.Empty;
+        return (frontmatter, body);
+    }
+
+    private static SkillFrontmatter ParseFrontmatter(string yaml)
+    {
+        try
+        {
+            var deserializer = new DeserializerBuilder()
+                .WithNamingConvention(UnderscoredNamingConvention.Instance)
+                .Build();
+            return deserializer.Deserialize<SkillFrontmatter>(yaml);
+        }
+        catch (Exception ex)
+        {
+            throw new SkillLoadException($"Malformed YAML frontmatter: {ex.Message}");
         }
+    }
 
-        return paths
-            .Distinct(StringComparer.OrdinalIgnoreCase)
-            .Order(StringComparer.OrdinalIgnoreCase)
-            .Select(File.ReadAllText)
-            .ToArray();
+    private sealed class SkillFrontmatter
+    {
+        public string Name { get; set; } = "";
+        public string Description { get; set; } = "";
+        public string? License { get; set; }
+        public string? Compatibility { get; set; }
+        public Dictionary<string, string>? Metadata { get; set; }
+        public string? AllowedTools { get; set; }
     }
 }
+
+public sealed class SkillLoadException(string message) : Exception(message);
diff --git a/src/Agent.App/Program.cs b/src/Agent.App/Program.cs
index 82a3f36..7839e82 100644
--- a/src/Agent.App/Program.cs
+++ b/src/Agent.App/Program.cs
@@ -85,7 +85,7 @@ internal static class Program
             {
                 string userPrompt = File.ReadAllText(ConfigurationLoader.Resolve(baseDirectory, configuration.Agent.UserSystemPrompt));
                 string skillDirectory = ConfigurationLoader.Resolve(baseDirectory, configuration.Skills.Directory);
-                string[] skills = SkillLoader.Load(skillDirectory);
+                var skills = SkillLoader.Load(skillDirectory);
                 var runtimeSettings = new AgentRuntimeSettings(userPrompt, language, skills, "Windows AppContainer, ACL, Job Object, child-process restriction, and WFP sandbox capabilities.", configuration.Agent.MaxIterations, configuration.Agent.SameFailureLimit, locale.Get("ollama.vision_unsupported"));
                 var visionLimits = new VisionLimits(configuration.Mcp.Images.MaxCount, configuration.Mcp.Images.MaxBytesEach, configuration.Mcp.Images.MaxTotalBytes);
                 await McpHost.RunStdioAsync(locale, OllamaSettingsFactory.Create(configuration.Ollama), runtimeSettings, visionLimits, CancellationToken.None,
@@ -96,7 +96,7 @@ internal static class Program
             {
                 string userPrompt = File.ReadAllText(ConfigurationLoader.Resolve(baseDirectory, configuration.Agent.UserSystemPrompt));
                 string skillDirectory = ConfigurationLoader.Resolve(baseDirectory, configuration.Skills.Directory);
-                string[] skills = SkillLoader.Load(skillDirectory);
+                var skills = SkillLoader.Load(skillDirectory);
                 var runtimeSettings = new AgentRuntimeSettings(userPrompt, language, skills, "Windows AppContainer, ACL, Job Object, child-process restriction, and WFP sandbox capabilities.", configuration.Agent.MaxIterations, configuration.Agent.SameFailureLimit, locale.Get("ollama.vision_unsupported"));
                 var visionLimits = new VisionLimits(configuration.Mcp.Images.MaxCount, configuration.Mcp.Images.MaxBytesEach, configuration.Mcp.Images.MaxTotalBytes);
                 await McpHost.RunHttpAsync(locale, OllamaSettingsFactory.Create(configuration.Ollama), runtimeSettings, visionLimits,