Normalize scalar frontmatter lists

MeetingAssistant.Tests/MeetingNoteStoreTests.cs

@@ -105,6 +105,36 @@ public sealed class MeetingNoteStoreTests
         Assert.Equal(userNotes, reloaded.UserNotes);
     }
 
+    [Fact]
+    public async Task ReadConvertsScalarListFrontmatterToSingleItemLists()
+    {
+        var (vaultRoot, store) = CreateStore();
+        var notePath = Path.Combine(vaultRoot, "Meetings", "Notes", "manual.md");
+        Directory.CreateDirectory(Path.GetDirectoryName(notePath)!);
+        await File.WriteAllTextAsync(
+            notePath,
+            """
+            ---
+            title: Manual frontmatter
+            start_time: "2026-05-19T10:00:00.0000000+02:00"
+            end_time: ""
+            attendees: Ada
+            projects: Meeting Assistant
+            transcript: "[[../Transcripts/manual-transcript|Transcript]]"
+            assistant_context: "[[../Assistant Context/manual-context|Assistant Context]]"
+            summary: "[[../Summaries/manual-summary|Summary]]"
+            ---
+
+            User notes.
+            """);
+
+        var loaded = await store.ReadAsync(notePath, CancellationToken.None);
+
+        Assert.Equal(["Ada"], loaded.Frontmatter.Attendees);
+        Assert.Equal(["Meeting Assistant"], loaded.Frontmatter.Projects);
+        Assert.Equal("User notes.", loaded.UserNotes);
+    }
+
     [Fact]
     public void ActionLinkEscapesSummaryFileName()
     {

MeetingAssistant.Tests/ProjectKnowledgeToolTests.cs

@@ -63,6 +63,34 @@ public sealed class ProjectKnowledgeToolTests
             await tools.Search("alpha"));
     }
 
+    [Fact]
+    public async Task ListProjectsAcceptsScalarProjectFrontmatter()
+    {
+        var root = Path.Combine(Path.GetTempPath(), "meeting-assistant-tests", Guid.NewGuid().ToString("N"));
+        var projectsRoot = Path.Combine(root, "Projects");
+        Directory.CreateDirectory(Path.Combine(projectsRoot, "MeetingAssistant"));
+        var artifacts = CreateArtifacts(root);
+        Directory.CreateDirectory(Path.GetDirectoryName(artifacts.MeetingNotePath)!);
+        await File.WriteAllTextAsync(
+            artifacts.MeetingNotePath,
+            """
+            ---
+            projects: MeetingAssistant
+            ---
+            """);
+        var tools = new MeetingSummaryTools(
+            artifacts,
+            new MeetingAssistantOptions
+            {
+                Vault =
+                {
+                    ProjectsFolder = projectsRoot
+                }
+            });
+
+        Assert.Equal("MeetingAssistant", await tools.ListProjects());
+    }
+
     [Fact]
     public async Task WriteProjectFileSupportsAppendReplaceInsertOverwriteAndCreate()
     {

MeetingAssistant/MeetingNotes/FrontmatterYamlDeserializer.cs

@@ -0,0 +1,24 @@
+using YamlDotNet.Serialization;
+using YamlDotNet.Serialization.NamingConventions;
+
+namespace MeetingAssistant.MeetingNotes;
+
+internal static class FrontmatterYamlDeserializer
+{
+    public static IDeserializer Create()
+    {
+        return new DeserializerBuilder()
+            .WithTypeConverter(new ScalarStringListYamlTypeConverter())
+            .IgnoreUnmatchedProperties()
+            .Build();
+    }
+
+    public static IDeserializer CreateWithUnderscoredNaming()
+    {
+        return new DeserializerBuilder()
+            .WithNamingConvention(UnderscoredNamingConvention.Instance)
+            .WithTypeConverter(new ScalarStringListYamlTypeConverter())
+            .IgnoreUnmatchedProperties()
+            .Build();
+    }
+}

MeetingAssistant/MeetingNotes/MarkdownMeetingNoteStore.cs

@@ -16,9 +16,7 @@ public sealed class MarkdownMeetingNoteStore : IMeetingNoteStore
     {
         this.options = options.Value;
         this.logger = logger;
-        yamlDeserializer = new DeserializerBuilder()
-            .IgnoreUnmatchedProperties()
-            .Build();
+        yamlDeserializer = FrontmatterYamlDeserializer.Create();
     }
 
     public async Task<MeetingNote> SaveAsync(MeetingNote note, CancellationToken cancellationToken)

MeetingAssistant/MeetingNotes/ScalarStringListYamlTypeConverter.cs

@@ -0,0 +1,38 @@
+using YamlDotNet.Core;
+using YamlDotNet.Core.Events;
+using YamlDotNet.Serialization;
+
+namespace MeetingAssistant.MeetingNotes;
+
+internal sealed class ScalarStringListYamlTypeConverter : IYamlTypeConverter
+{
+    public bool Accepts(Type type)
+    {
+        return type == typeof(List<string>);
+    }
+
+    public object ReadYaml(IParser parser, Type type, ObjectDeserializer rootDeserializer)
+    {
+        if (parser.TryConsume<Scalar>(out var scalar))
+        {
+            return string.IsNullOrWhiteSpace(scalar.Value)
+                ? []
+                : new List<string> { scalar.Value };
+        }
+
+        var values = new List<string>();
+        parser.Consume<SequenceStart>();
+        while (!parser.TryConsume<SequenceEnd>(out _))
+        {
+            var item = parser.Consume<Scalar>();
+            values.Add(item.Value);
+        }
+
+        return values;
+    }
+
+    public void WriteYaml(IEmitter emitter, object? value, Type type, ObjectSerializer serializer)
+    {
+        serializer(value, typeof(IEnumerable<string>));
+    }
+}

MeetingAssistant/Summary/BoundMeetingProjectResolver.cs

@@ -7,9 +7,7 @@ public sealed record BoundMeetingProject(string Name, string Path);
 
 public sealed class BoundMeetingProjectResolver
 {
-    private static readonly IDeserializer YamlDeserializer = new DeserializerBuilder()
-        .IgnoreUnmatchedProperties()
-        .Build();
+    private static readonly IDeserializer YamlDeserializer = FrontmatterYamlDeserializer.Create();
 
     private readonly MeetingAssistantOptions options;
 

MeetingAssistant/Summary/MeetingSummaryFrontmatterFactory.cs

@@ -5,9 +5,7 @@ namespace MeetingAssistant.Summary;
 
 internal static class MeetingSummaryFrontmatterFactory
 {
-    private static readonly IDeserializer YamlDeserializer = new DeserializerBuilder()
-        .IgnoreUnmatchedProperties()
-        .Build();
+    private static readonly IDeserializer YamlDeserializer = FrontmatterYamlDeserializer.Create();
 
     public static async Task<MeetingArtifactFrontmatter> CreateAsync(
         MeetingSessionArtifacts artifacts,

MeetingAssistant/Summary/MeetingSummaryTools.cs

@@ -7,9 +7,7 @@ namespace MeetingAssistant.Summary;
 
 public sealed class MeetingSummaryTools
 {
-    private static readonly IDeserializer YamlDeserializer = new DeserializerBuilder()
-        .IgnoreUnmatchedProperties()
-        .Build();
+    private static readonly IDeserializer YamlDeserializer = FrontmatterYamlDeserializer.Create();
 
     private readonly MeetingSessionArtifacts artifacts;
     private readonly MeetingAssistantOptions options;

MeetingAssistant/Workflow/WorkflowRulesEditorTools.cs

@@ -12,16 +12,12 @@ using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Logging;
 using YamlDotNet.Core;
 using YamlDotNet.Serialization;
-using YamlDotNet.Serialization.NamingConventions;
 
 namespace MeetingAssistant.Workflow;
 
 public sealed class WorkflowRulesEditorTools
 {
-    private static readonly IDeserializer YamlDeserializer = new DeserializerBuilder()
-        .WithNamingConvention(UnderscoredNamingConvention.Instance)
-        .IgnoreUnmatchedProperties()
-        .Build();
+    private static readonly IDeserializer YamlDeserializer = FrontmatterYamlDeserializer.CreateWithUnderscoredNaming();
     private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web)
     {
         WriteIndented = true

openspec/specs/meeting-session/spec.md

@@ -48,6 +48,12 @@ Generated artifact notes SHALL link only to the other notes from the same run an
 - **WHEN** Meeting Assistant creates a meeting note
 - **THEN** the note frontmatter links to the configured transcript, assistant context, and summary note locations
 
+#### Scenario: Scalar list frontmatter is normalized
+- **GIVEN** a meeting note frontmatter field that Meeting Assistant expects as a list is stored as a scalar string
+- **WHEN** Meeting Assistant reads the meeting note
+- **THEN** it treats the scalar string as a one-item list
+- **AND** continues processing the meeting note
+
 #### Scenario: Generated artifacts do not self-reference
 - **WHEN** Meeting Assistant writes transcript, assistant context, or summary artifact frontmatter
 - **THEN** the artifact frontmatter links to the other run notes