diff --git a/src/PostIt.Tests/BlogPostAuthorDtoTests.cs b/src/PostIt.Tests/BlogPostAuthorDtoTests.cs
new file mode 100644
index 00000000..895f220e
--- /dev/null
+++ b/src/PostIt.Tests/BlogPostAuthorDtoTests.cs
@@ -0,0 +1,169 @@
+using System.Text.Json;
+using Yavsc.Blogspot;
+
+namespace PostIt.Tests;
+
+/// <summary>
+/// Round-trip tests for the wire shape of a blog post as
+/// serialised by Yavsc.Blogs and consumed by PostIt.
+///
+/// <para>
+/// Background: in 1.0.7, <c>BlogPostDto.Author</c> was typed as
+/// the abstract interface <c>IApplicationUser</c>. System.Text.Json
+/// cannot materialise an interface without a polymorphic
+/// converter, so the "load posts" call from PostIt crashed when
+/// the server returned a post with a populated <c>Author</c>
+/// object. The fix replaced <c>IApplicationUser</c> with a thin
+/// concrete DTO, <c>BlogPostAuthorDto</c>, embedded directly in
+/// <c>BlogPostDto.Author</c>.
+/// </para>
+///
+/// <para>
+/// These tests pin the wire shape: a JSON document with an
+/// <c>Author</c> object must deserialise without throwing and
+/// must round-trip the three fields PostIt exposes in the UI
+/// (Id, UserName, Avatar). They are intentionally placed in
+/// <c>PostIt.Tests</c> — the client-side assembly — so the
+/// regression is caught at the deserialisation boundary, where
+/// it actually manifested in production.
+/// </para>
+/// </summary>
+public class BlogPostAuthorDtoTests
+{
+    private static readonly JsonSerializerOptions CaseInsensitiveJson
+        = new() { PropertyNameCaseInsensitive = true };
+
+    [Fact]
+    public void BlogPostDto_deserialises_with_populated_author()
+    {
+        // A representative JSON shape the server would emit for
+        // GET /api/BlogApi. The Author object is fully populated
+        // — that's the shape that used to break deserialisation
+        // when Author was typed as the abstract IApplicationUser
+        // interface.
+        var json = """
+        {
+          "id": 42,
+          "title": "Premier billet",
+          "article": "Contenu",
+          "photo": null,
+          "dateCreated": "2026-08-01T12:00:00Z",
+          "dateModified": "2026-08-02T12:00:00Z",
+          "userCreated": "alice",
+          "userModified": "alice",
+          "authorId": "u-alice",
+          "isPublished": true,
+          "author": {
+            "id": "u-alice",
+            "userName": "alice",
+            "avatar": "/avatars/alice.png"
+          }
+        }
+        """;
+
+        var post = JsonSerializer.Deserialize<BlogPostDto>(json, CaseInsensitiveJson);
+
+        Assert.NotNull(post);
+        Assert.Equal(42, post!.Id);
+        Assert.Equal("Premier billet", post.Title);
+        Assert.Equal("u-alice", post.AuthorId);
+        Assert.True(post.IsPublished);
+
+        // The actual regression coverage: Author must
+        // materialise as a concrete DTO, not be left null because
+        // of a JsonException on IApplicationUser.
+        Assert.NotNull(post.Author);
+        Assert.Equal("u-alice", post.Author!.Id);
+        Assert.Equal("alice", post.Author.UserName);
+        Assert.Equal("/avatars/alice.png", post.Author.Avatar);
+    }
+
+    [Fact]
+    public void BlogPostDto_deserialises_when_author_is_null()
+    {
+        // The server is allowed to omit Author (the field is
+        // nullable on the wire — it maps to a navigation
+        // property that may not have been Included). The client
+        // must accept that shape without throwing.
+        var json = """
+        {
+          "id": 7,
+          "title": "Sans auteur",
+          "article": null,
+          "photo": null,
+          "dateCreated": "2026-08-01T12:00:00Z",
+          "dateModified": "2026-08-01T12:00:00Z",
+          "userCreated": "system",
+          "userModified": "system",
+          "authorId": "system",
+          "isPublished": false,
+          "author": null
+        }
+        """;
+
+        var post = JsonSerializer.Deserialize<BlogPostDto>(json, CaseInsensitiveJson);
+
+        Assert.NotNull(post);
+        Assert.Null(post!.Author);
+        Assert.Equal("system", post.AuthorId);
+    }
+
+    [Fact]
+    public void BlogPostDto_deserialises_when_author_field_is_missing()
+    {
+        // Forward-compatibility: an older server that doesn't
+        // emit the Author field at all. Should not throw.
+        var json = """
+        {
+          "id": 9,
+          "title": "Ancien format",
+          "article": "Pas d'auteur dans la charge utile",
+          "photo": null,
+          "dateCreated": "2026-07-01T12:00:00Z",
+          "dateModified": "2026-07-01T12:00:00Z",
+          "userCreated": "bob",
+          "userModified": "bob",
+          "authorId": "u-bob",
+          "isPublished": true
+        }
+        """;
+
+        var post = JsonSerializer.Deserialize<BlogPostDto>(json, CaseInsensitiveJson);
+
+        Assert.NotNull(post);
+        Assert.Null(post!.Author);
+    }
+
+    [Fact]
+    public void BlogPostAuthorDto_serialises_back_to_expected_json_shape()
+    {
+        // Pin the wire shape on the way out too. The server
+        // builds BlogPostAuthorDto from an ApplicationUser and
+        // PostIt receives it as JSON; if the field names
+        // change (e.g. case) the round-trip on the client side
+        // is what would silently break.
+        //
+        // The server emits camelCase (ASP.NET Core's Web
+        // defaults — PropertyNamingPolicy = CamelCase). We
+        // mirror that here so the test reflects what the wire
+        // actually looks like. PropertyNameCaseInsensitive on
+        // the client deserialiser means we don't have to
+        // hardcode the casing for the inbound assertions.
+        var author = new BlogPostAuthorDto
+        {
+            Id = "u-alice",
+            UserName = "alice",
+            Avatar = "/avatars/alice.png"
+        };
+
+        var json = JsonSerializer.Serialize(author,
+            new JsonSerializerOptions { PropertyNamingPolicy = JsonNamingPolicy.CamelCase });
+
+        using var doc = JsonDocument.Parse(json);
+        var root = doc.RootElement;
+
+        Assert.True(root.TryGetProperty("id", out _));
+        Assert.True(root.TryGetProperty("userName", out _));
+        Assert.True(root.TryGetProperty("avatar", out _));
+    }
+}
diff --git a/src/Yavsc.Abstract/Blogspot/BlogPost.cs b/src/Yavsc.Abstract/Blogspot/BlogPost.cs
index 0f88fdf8..2406fb2a 100644
--- a/src/Yavsc.Abstract/Blogspot/BlogPost.cs
+++ b/src/Yavsc.Abstract/Blogspot/BlogPost.cs
@@ -1,5 +1,4 @@
 using System;
-using Yavsc.Abstract.Identity;
 using Yavsc.Abstract.Identity.Security;
 
 namespace Yavsc.Blogspot;
@@ -8,7 +7,7 @@ public class BlogPostDto : IBlogPost
 {
     public string AuthorId { get; set; }
 
-    public IApplicationUser Author { get; set; }
+    public BlogPostAuthorDto? Author { get; set; }
 
     public string Article { get; set ; }
     public string Photo { get; set ; }
diff --git a/src/Yavsc.Abstract/Blogspot/BlogPostAuthorDto.cs b/src/Yavsc.Abstract/Blogspot/BlogPostAuthorDto.cs
new file mode 100644
index 00000000..e332822e
--- /dev/null
+++ b/src/Yavsc.Abstract/Blogspot/BlogPostAuthorDto.cs
@@ -0,0 +1,33 @@
+namespace Yavsc.Blogspot;
+
+/// <summary>
+/// Minimum-viable author payload embedded in <see cref="BlogPostDto"/>.
+///
+/// <para>
+/// Before this record existed, <c>BlogPostDto.Author</c> was typed
+/// as the abstract interface <c>IApplicationUser</c>. The
+/// interface is fine for server-side contract (we have a concrete
+/// entity that implements it) but System.Text.Json cannot
+/// materialise an interface without a polymorphic converter
+/// configured on both ends. PostIt would crash on load-posts
+/// because the JSON contained an <c>Author</c> object that the
+/// client could not deserialise.
+/// </para>
+///
+/// <para>
+/// This record is the wire shape: <c>Id</c> for "go to author
+/// profile", <c>UserName</c> for "by @username", <c>Avatar</c>
+/// for the round badge next to the title. The server-side
+/// <c>BlogPost</c> entity (<c>Yavsc.Server.Models.Blog</c>) keeps
+/// its full <c>ApplicationUser</c> navigation property for
+/// permission checks and authorisation; the DTO is built on
+/// demand by the controller / service layer when the post is
+/// served to the wire.
+/// </para>
+/// </summary>
+public sealed record BlogPostAuthorDto
+{
+    public string Id { get; init; } = string.Empty;
+    public string? UserName { get; init; }
+    public string? Avatar { get; init; }
+}
diff --git a/src/Yavsc.Abstract/Blogspot/IBlogPost.cs b/src/Yavsc.Abstract/Blogspot/IBlogPost.cs
index 5287685d..6090fca2 100644
--- a/src/Yavsc.Abstract/Blogspot/IBlogPost.cs
+++ b/src/Yavsc.Abstract/Blogspot/IBlogPost.cs
@@ -1,7 +1,6 @@
 
 
 
-using Yavsc.Abstract.Identity;
 using Yavsc.Abstract.Identity.Security;
 using Yavsc.Interfaces;
 
@@ -9,6 +8,11 @@ namespace Yavsc.Blogspot
 {
     public interface IBlogPost : IBlogPostPayLoad, ICircleAuthorized,  ITrackedEntity,  ITitle
     {
-        IApplicationUser Author { get; }
+        // Typed as a concrete wire DTO (not the IApplicationUser
+        // interface) so System.Text.Json can materialise it on the
+        // client without a polymorphic converter. The server-side
+        // BlogPost entity implements this getter by mapping its
+        // ApplicationUser navigation to a BlogPostAuthorDto.
+        BlogPostAuthorDto? Author { get; }
     }
 }
diff --git a/src/Yavsc.Server/Models/Blog/BlogPost.cs b/src/Yavsc.Server/Models/Blog/BlogPost.cs
index 213910cd..be9fe7fa 100644
--- a/src/Yavsc.Server/Models/Blog/BlogPost.cs
+++ b/src/Yavsc.Server/Models/Blog/BlogPost.cs
@@ -107,6 +107,32 @@ namespace Yavsc.Models.Blog
         [NotMapped]
         public bool IsPublished { get; set; }
 
-        IApplicationUser IBlogPost.Author => Author;
+        /// <summary>
+        /// Explicit interface implementation of
+        /// <see cref="IBlogPost.Author"/>. The underlying
+        /// navigation property is <see cref="Author"/>
+        /// (an <c>ApplicationUser</c> entity), but the wire
+        /// DTO is a thin <see cref="BlogPostAuthorDto"/> with
+        /// only the fields the client UI consumes. We project
+        /// on demand so EF can lazy-load the navigation
+        /// without forcing an eager join on every read.
+        /// Returns <c>null</c> when the navigation hasn't been
+        /// loaded (caller should pre-Include <c>Author</c> if
+        /// they need it).
+        /// </summary>
+        BlogPostAuthorDto? IBlogPost.Author
+        {
+            get
+            {
+                var a = Author;
+                if (a == null) return null;
+                return new BlogPostAuthorDto
+                {
+                    Id = a.Id,
+                    UserName = a.UserName,
+                    Avatar = a.Avatar
+                };
+            }
+        }
     }
 }
diff --git a/yavsc.sln b/yavsc.sln
index fafdff89..7d972ade 100644
--- a/yavsc.sln
+++ b/yavsc.sln
@@ -37,6 +37,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Yavsc.Blogs.Tests", "src\Ya
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Yavsc.Tests.Shared", "src\Yavsc.Tests.Shared\Yavsc.Tests.Shared.csproj", "{34D1F73D-BF74-47CC-9358-9F4F221C75D7}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Yavsc.Api.Client", "src\Yavsc.Api.Client\Yavsc.Api.Client.csproj", "{59AF5DEA-D349-495A-BC44-FC7BD4E55099}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -215,6 +217,18 @@ Global
 		{34D1F73D-BF74-47CC-9358-9F4F221C75D7}.Release|x64.Build.0 = Release|Any CPU
 		{34D1F73D-BF74-47CC-9358-9F4F221C75D7}.Release|x86.ActiveCfg = Release|Any CPU
 		{34D1F73D-BF74-47CC-9358-9F4F221C75D7}.Release|x86.Build.0 = Release|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Debug|x64.Build.0 = Debug|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Debug|x86.Build.0 = Debug|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Release|Any CPU.Build.0 = Release|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Release|x64.ActiveCfg = Release|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Release|x64.Build.0 = Release|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Release|x86.ActiveCfg = Release|Any CPU
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -235,5 +249,6 @@ Global
 		{4D283324-6DD3-4CD1-9893-8C317772C6B5} = {CDB1BDB5-53F9-4B43-864F-60F2E74F44E2}
 		{0E471075-DABF-40E9-98B7-1630BEF19145} = {CDB1BDB5-53F9-4B43-864F-60F2E74F44E2}
 		{34D1F73D-BF74-47CC-9358-9F4F221C75D7} = {CDB1BDB5-53F9-4B43-864F-60F2E74F44E2}
+		{59AF5DEA-D349-495A-BC44-FC7BD4E55099} = {CDB1BDB5-53F9-4B43-864F-60F2E74F44E2}
 	EndGlobalSection
 EndGlobal