feat(fp): WP-26 — admin org-template editor

Edit the letter's org identity in place on the same canvas the drafter composes
on (editableRegions='template'): letterhead/signature/footer become inline
controls, content a read-only sample. Margins (bounded), logo upload (reuses the
shared upload transport + single-upload), version history + rollback, proefbrief,
and publish-with-impact-confirmation. House form-machine idiom
(org-template.machine.ts) + root store with debounced save. Capability-gated
(orgtemplate:edit) with a deny-by-default alert; route /brief/huisstijl.

Backend + generated client were already in place (WP-23). Also fixes a
pre-existing red check:tokens (WP-24 canvas hex fallbacks) and threads the
published logo through to the drafter's canvas.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/BigRegister.Api/Data/BriefStore.cs

@@ -1,5 +1,6 @@
 using BigRegister.Api.Contracts;
 using BigRegister.Domain.Authorization;
+using BigRegister.Domain.Letters;
 using Microsoft.EntityFrameworkCore;
 
 namespace BigRegister.Api.Data;
@@ -26,6 +27,9 @@ public sealed class BriefEntity
   public string SubOrgId { get; set; } = OrgTemplateSeed.Registers;
   /// Pinned at send: sent letters are immutable, a republish never re-themes them.
   public int? SentOrgTemplateVersion { get; set; }
+  /// The composed HTML archived at send (WP-25) — from here on the preview endpoint
+  /// serves this verbatim, so a later org-template republish never re-renders it.
+  public string? ArchivedHtml { get; set; }
 
   public BriefDto ToDto() => new(BriefId, Beroep, TemplateId, Placeholders, Sections, Status, DrafterId);
 }
@@ -110,6 +114,10 @@ public static class BriefStore
       // Pin the org-template version the letter was sent with (WP-23): from here on
       // its appearance is frozen — republishing the template touches unsent briefs only.
       e.SentOrgTemplateVersion = OrgTemplateStore.PublishedVersionOf(e.SubOrgId);
+      // Archive the composed HTML at this exact instant (WP-25): the preview endpoint
+      // serves this verbatim once sent, so a later republish never re-renders it.
+      var template = OrgTemplateStore.TemplateForBrief(e.SubOrgId, e.SentOrgTemplateVersion);
+      e.ArchivedHtml = LetterHtml.Render(e, template, at, watermark: false);
       db.SaveChanges();
       return (Outcome.Ok, e);
     }

backend/src/BigRegister.Api/Data/Migrations/20260705101743_ArchivedHtml.Designer.cs

@@ -0,0 +1,226 @@
+// <auto-generated />
+using System;
+using BigRegister.Api.Data;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+#nullable disable
+
+namespace BigRegister.Api.Data.Migrations
+{
+    [DbContext(typeof(AppDbContext))]
+    [Migration("20260705101743_ArchivedHtml")]
+    partial class ArchivedHtml
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder.HasAnnotation("ProductVersion", "10.0.9");
+
+            modelBuilder.Entity("BigRegister.Api.Data.Aanvraag", b =>
+                {
+                    b.Property<string>("Id")
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("AutoApprovable")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("DocumentIds")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Draft")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Owner")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Reden")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Referentie")
+                        .HasColumnType("TEXT");
+
+                    b.Property<int>("StepCount")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<int>("StepIndex")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<bool>("Submitted")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<DateTimeOffset?>("SubmittedAt")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("Applications");
+                });
+
+            modelBuilder.Entity("BigRegister.Api.Data.AuditEntry", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("Action")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Actor")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<DateTimeOffset>("At")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("CategoryId")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("DocumentId")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("AuditEntries");
+                });
+
+            modelBuilder.Entity("BigRegister.Api.Data.BriefEntity", b =>
+                {
+                    b.Property<string>("BriefId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("ArchivedHtml")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Beroep")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("DrafterId")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Owner")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Placeholders")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Sections")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<int?>("SentOrgTemplateVersion")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("SubOrgId")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("TemplateId")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("BriefId");
+
+                    b.HasIndex("Owner")
+                        .IsUnique();
+
+                    b.ToTable("Briefs");
+                });
+
+            modelBuilder.Entity("BigRegister.Api.Data.OrgTemplateEntity", b =>
+                {
+                    b.Property<string>("SubOrgId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Draft")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("History")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<int>("PublishedVersion")
+                        .HasColumnType("INTEGER");
+
+                    b.HasKey("SubOrgId");
+
+                    b.ToTable("OrgTemplates");
+                });
+
+            modelBuilder.Entity("BigRegister.Api.Data.StoredDocument", b =>
+                {
+                    b.Property<string>("DocumentId")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("CategoryId")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<byte[]>("Content")
+                        .IsRequired()
+                        .HasColumnType("BLOB");
+
+                    b.Property<string>("ContentType")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("FileName")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<bool>("Linked")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<string>("LocalId")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("Owner")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.Property<long>("SizeBytes")
+                        .HasColumnType("INTEGER");
+
+                    b.Property<DateTimeOffset>("UploadedAt")
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("WizardId")
+                        .IsRequired()
+                        .HasColumnType("TEXT");
+
+                    b.HasKey("DocumentId");
+
+                    b.ToTable("Documents");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}

backend/src/BigRegister.Api/Data/Migrations/20260705101743_ArchivedHtml.cs

@@ -0,0 +1,28 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace BigRegister.Api.Data.Migrations
+{
+  /// <inheritdoc />
+  public partial class ArchivedHtml : Migration
+  {
+    /// <inheritdoc />
+    protected override void Up(MigrationBuilder migrationBuilder)
+    {
+      migrationBuilder.AddColumn<string>(
+          name: "ArchivedHtml",
+          table: "Briefs",
+          type: "TEXT",
+          nullable: true);
+    }
+
+    /// <inheritdoc />
+    protected override void Down(MigrationBuilder migrationBuilder)
+    {
+      migrationBuilder.DropColumn(
+          name: "ArchivedHtml",
+          table: "Briefs");
+    }
+  }
+}

backend/src/BigRegister.Api/Data/Migrations/AppDbContextModelSnapshot.cs

@@ -104,6 +104,9 @@ namespace BigRegister.Api.Data.Migrations
                     b.Property<string>("BriefId")
                         .HasColumnType("TEXT");
 
+                    b.Property<string>("ArchivedHtml")
+                        .HasColumnType("TEXT");
+
                     b.Property<string>("Beroep")
                         .IsRequired()
                         .HasColumnType("TEXT");

backend/src/BigRegister.Api/Domain/Letters/LetterHtml.cs

@@ -0,0 +1,191 @@
+using System.Globalization;
+using System.Text;
+using BigRegister.Api.Contracts;
+using BigRegister.Api.Data;
+
+namespace BigRegister.Domain.Letters;
+
+/// <summary>
+/// Server-rendered letter HTML (WP-25) — the archived, "what is sent" artifact.
+/// Mirrors the FE letter canvas' class vocabulary exactly (<c>public/letter.css</c>,
+/// the FE⇄BE contract; LetterHtmlTests' class-parity test is the fence against drift).
+///
+/// Unlike the canvas, placeholders resolve to real text rather than a live editor
+/// widget: an auto-resolvable key pulls from seed/case data (there is no per-brief
+/// resolved value stored anywhere else in the domain — see BriefEntity's own "does
+/// not interpret it" posture), an unresolved manual key renders literally as
+/// "[NOG IN TE VULLEN: label]" (PRD Brief v2 §8) — the preview works despite this,
+/// only send blocks on it (FE-authoritative linting).
+///
+/// ponytail: HTML today, a headless-Chromium PDF render slots in behind this same
+/// route if the POC ever needs real PDF bytes — see the preview endpoints.
+/// </summary>
+public static class LetterHtml
+{
+  private static readonly string Css = File.ReadAllText(FindLetterCss());
+
+  public static string Render(BriefEntity brief, OrgTemplateDto template, string at, bool watermark)
+  {
+    var defs = brief.Placeholders.ToDictionary(p => p.Key);
+    var sb = new StringBuilder();
+
+    sb.Append("<!doctype html><html lang=\"nl\"><head><meta charset=\"utf-8\">");
+    sb.Append("<title>").Append(Enc(brief.BriefId)).Append("</title>");
+    sb.Append("<style>").Append(Css).Append(ExtraCss).Append("</style>");
+    sb.Append("</head><body>");
+    sb.Append("<div class=\"letter\" style=\"").Append(MarginStyle(template.Margins)).Append("\">");
+
+    // --- letterhead ---
+    sb.Append("<div class=\"letter__letterhead\">");
+    if (template.LogoDocumentId is { } logoId && DocumentStore.Get(logoId) is { } logo)
+    {
+      sb.Append("<img class=\"org-logo\" alt=\"\" src=\"data:").Append(logo.ContentType)
+          .Append(";base64,").Append(Convert.ToBase64String(logo.Content)).Append("\">");
+    }
+    sb.Append("<p class=\"org-wordmark\">").Append(Enc(template.OrgName)).Append("</p>");
+    sb.Append("<address class=\"return-address\">").Append(EncLines(template.ReturnAddress)).Append("</address>");
+    sb.Append("<address class=\"address-window\">").Append(EncLines(RecipientPlaceholder)).Append("</address>");
+    sb.Append("<dl class=\"reference\">");
+    sb.Append("<div><dt>Ons kenmerk</dt><dd>").Append(Enc(brief.BriefId)).Append("</dd></div>");
+    sb.Append("<div><dt>Datum</dt><dd>").Append(Enc(FormatDatumNl(at))).Append("</dd></div>");
+    sb.Append("</dl></div>");
+
+    // --- body: the case-type template's sections ---
+    sb.Append("<div class=\"letter__body\">");
+    foreach (var section in brief.Sections)
+    {
+      sb.Append("<section><h3>").Append(Enc(section.Title)).Append("</h3>");
+      foreach (var block in section.Blocks)
+        RenderParagraphs(sb, block.Content.Paragraphs, defs);
+      sb.Append("</section>");
+    }
+    sb.Append("</div>");
+
+    // --- signature ---
+    sb.Append("<div class=\"letter__signature\">");
+    sb.Append("<p>").Append(Enc(template.SignatureClosing)).Append("</p>");
+    sb.Append("<p class=\"signature-name\">").Append(Enc(template.SignatureName)).Append("</p>");
+    sb.Append("<p>").Append(Enc(template.SignatureRole)).Append("</p>");
+    sb.Append("</div>");
+
+    // --- footer ---
+    sb.Append("<div class=\"letter__footer\">");
+    sb.Append("<div class=\"footer-contact\">").Append(EncLines(template.FooterContact)).Append("</div>");
+    sb.Append("<div class=\"footer-legal\">").Append(Enc(template.FooterLegal)).Append("</div>");
+    sb.Append("</div>");
+
+    if (watermark) sb.Append("<div class=\"preview-watermark\" aria-hidden=\"true\">VOORBEELD</div>");
+
+    sb.Append("</div></body></html>");
+    return sb.ToString();
+  }
+
+  /// Exposed so LetterHtmlTests can assert every `letter`-prefixed class this
+  /// renderer emits also exists in the shared contract file — the fence against drift.
+  public static string StyleSheet => Css;
+
+  // No recipient address is tracked anywhere in this POC's brief domain (BRP lookup
+  // is out of scope here) — the canvas shows the same static placeholder text.
+  private const string RecipientPlaceholder = "Adres van de geadresseerde\n(wordt ingevuld bij verzending)";
+
+  private static void RenderParagraphs(
+      StringBuilder sb, IReadOnlyList<ParagraphDto> paragraphs, IReadOnlyDictionary<string, PlaceholderDefDto> defs)
+  {
+    string? openList = null;
+    foreach (var para in paragraphs)
+    {
+      if (para.List != openList)
+      {
+        if (openList is not null) sb.Append(openList == "bullet" ? "</ul>" : "</ol>");
+        if (para.List is not null) sb.Append(para.List == "bullet" ? "<ul>" : "<ol>");
+        openList = para.List;
+      }
+      sb.Append(openList is null ? "<p>" : "<li>");
+      foreach (var node in para.Nodes) RenderNode(sb, node, defs);
+      sb.Append(openList is null ? "</p>" : "</li>");
+    }
+    if (openList is not null) sb.Append(openList == "bullet" ? "</ul>" : "</ol>");
+  }
+
+  private static void RenderNode(
+      StringBuilder sb, RichTextNodeDto node, IReadOnlyDictionary<string, PlaceholderDefDto> defs)
+  {
+    switch (node.Type)
+    {
+      case "text":
+        sb.Append(Enc(node.Text ?? ""));
+        break;
+      case "lineBreak":
+        sb.Append("<br>");
+        break;
+      case "placeholder":
+        var key = node.Key ?? "";
+        var def = defs.GetValueOrDefault(key);
+        var label = def?.Label ?? key;
+        sb.Append(def is { AutoResolvable: true } ? Enc(ResolveAuto(key, label)) : Enc($"[NOG IN TE VULLEN: {label}]"));
+        break;
+    }
+  }
+
+  // The only place a placeholder key gets a real value: seed/case data for the
+  // single demo applicant (SeedData.Registration — no per-brief resolved value is
+  // ever stored, see the class doc above). Falls back to the label itself for any
+  // other auto-resolvable key, mirroring the FE canvas' own `sampleFor` fallback.
+  private static string ResolveAuto(string key, string label) => key switch
+  {
+    "naam_zorgverlener" => SeedData.Registration.Naam,
+    "big_nummer" => SeedData.Registration.BigNummer,
+    "datum" => FormatDatumNl(DateTimeOffset.UtcNow.ToString("o")),
+    _ => label,
+  };
+
+  private static readonly CultureInfo Nl = CultureInfo.GetCultureInfo("nl-NL");
+  private static string FormatDatumNl(string at) => DateTimeOffset.Parse(at).ToString("d MMMM yyyy", Nl);
+
+  private static string MarginStyle(MarginsDto m) =>
+      $"--letter-margin-top:{m.TopMm}mm;--letter-margin-right:{m.RightMm}mm;" +
+      $"--letter-margin-bottom:{m.BottomMm}mm;--letter-margin-left:{m.LeftMm}mm;";
+
+  private static string Enc(string s) => System.Net.WebUtility.HtmlEncode(s);
+  private static string EncLines(string s) => Enc(s).Replace("\n", "<br>");
+
+  // Walks up from the running assembly's own directory (NOT the process cwd, which
+  // varies by how `dotnet run`/docker/tests invoke it — see docs/backlog/WP-25) until
+  // it finds `public/letter.css`. docker-compose.yml bind-mounts `./public` under the
+  // api container's `/src` for exactly this walk to resolve there too.
+  private static string FindLetterCss()
+  {
+    for (var dir = new DirectoryInfo(AppContext.BaseDirectory); dir is not null; dir = dir.Parent)
+    {
+      var candidate = Path.Combine(dir.FullName, "public", "letter.css");
+      if (File.Exists(candidate)) return candidate;
+    }
+    throw new FileNotFoundException(
+        $"public/letter.css not found by walking up from {AppContext.BaseDirectory} " +
+        "— check the docker bind mount or build output location.");
+  }
+
+  // Backend-only concerns absent from the FE canvas (no live preview toggle for
+  // either): kept out of the shared contract file, not "letter"-prefixed so the
+  // class-parity test's scope doesn't need to widen for them.
+  private const string ExtraCss = """
+      .preview-watermark {
+        position: fixed;
+        inset: 0;
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        font-size: 72pt;
+        font-weight: 700;
+        color: rgb(200 30 30 / 0.18);
+        transform: rotate(-30deg);
+        pointer-events: none;
+        z-index: 3;
+      }
+      .org-logo {
+        display: block;
+        max-height: 18mm;
+        margin-block-end: 4mm;
+      }
+      """;
+}

backend/src/BigRegister.Api/Program.cs

@@ -346,6 +346,31 @@ api.MapPost("/brief/send", (HttpContext ctx) =>
 .Produces<BriefViewDto>()
 .ProducesProblem(StatusCodes.Status409Conflict);
 
+// Server-rendered HTML preview (WP-25): "what you compose is what is sent" — the
+// same LetterHtml.Render a sent brief archived. Hand-written on the FE (fetch →
+// blob → new tab), so excluded from the OpenAPI doc, same seam as uploads. Sent
+// letters serve their frozen archive; anything else renders live with a watermark.
+api.MapGet("/brief/preview", (HttpContext ctx) =>
+{
+  var e = BriefStore.GetOrCreate(DocumentStore.DemoOwner);
+  if (e.Status.Tag == "sent" && e.ArchivedHtml is { } archived)
+    return Results.Content(archived, "text/html");
+  var template = OrgTemplateStore.TemplateForBrief(e.SubOrgId, null);
+  return Results.Content(LetterHtml.Render(e, template, Now(), watermark: true), "text/html");
+})
+.ExcludeFromDescription();
+
+// Proefbrief: the admin's unpublished draft template rendered over a fixture
+// brief, so the appearance can be checked before publishing touches real letters.
+api.MapGet("/admin/org-template/{subOrgId}/preview", (string subOrgId, HttpContext ctx) => OrgAdmin(ctx, () =>
+{
+  var view = OrgTemplateStore.AdminView(subOrgId);
+  if (view is null) return Results.NotFound();
+  var fixture = BriefSeed.NewBrief("proefbrief");
+  return Results.Content(LetterHtml.Render(fixture, view.Draft, Now(), watermark: true), "text/html");
+}))
+.ExcludeFromDescription();
+
 api.MapPost("/brief/reset", (HttpContext ctx) =>
 {
   // Demo "start over": recreate a fresh draft. No guards — showcase affordance only.

backend/tests/BigRegister.Tests/BigRegister.Tests.csproj

@@ -23,4 +23,10 @@
     <ProjectReference Include="..\..\src\BigRegister.Api\BigRegister.Api.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Content Include="LetterHtml.golden.html">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
 </Project>

backend/tests/BigRegister.Tests/LetterHtml.golden.html

@@ -0,0 +1,215 @@
+<!doctype html><html lang="nl"><head><meta charset="utf-8"><title>golden-brief-1</title><style>/* letter.css — the FE⇄BE letter-rendering CONTRACT (WP-24/WP-25).
+ *
+ * One stylesheet, two consumers: the FE letter canvas loads it via <link>
+ * (index.html + Storybook preview-head), the backend HTML renderer (WP-25)
+ * inlines this same file. Its class-parity test is the fence against drift.
+ *
+ * Class vocabulary: .letter, .letter__letterhead, .letter__body,
+ * .letter__signature, .letter__footer, .letter__page-break.
+ * Margins arrive as --letter-margin-* custom props (mm, from the OrgTemplate);
+ * the defaults below match the seed template.
+ *
+ * Deliberately self-contained: no --rhc- or --bs- tokens — the backend renderer
+ * has no token bridge. Geometry follows the sample voorbeeldbrief-inschrijving
+ * (A4, return address above the envelope window, reference block, footer rule).
+ */
+
+.letter {
+  --letter-margin-top: 25mm;
+  --letter-margin-right: 25mm;
+  --letter-margin-bottom: 25mm;
+  --letter-margin-left: 25mm;
+
+  position: relative;
+  box-sizing: border-box;
+  width: 210mm; /* A4 */
+  max-width: 100%;
+  min-height: 297mm;
+  margin-inline: auto;
+  padding: var(--letter-margin-top) var(--letter-margin-right) var(--letter-margin-bottom)
+    var(--letter-margin-left);
+  background: #fff;
+  color: #1a1a1a;
+  /* Letter typography is the letter's, not the portal UI's. Licensed RO/Rijks
+     fonts are not shipped; system stack mirrors the app-wide decision (ADR-0003). */
+  font-family:
+    system-ui,
+    -apple-system,
+    'Segoe UI',
+    Roboto,
+    sans-serif;
+  font-size: 10.5pt;
+  line-height: 1.5;
+  display: flex;
+  flex-direction: column;
+}
+
+.letter p {
+  margin: 0 0 0.75em;
+}
+
+.letter ul,
+.letter ol {
+  margin: 0 0 0.75em;
+  padding-inline-start: 1.4em;
+}
+
+/* --- Letterhead: wordmark, return address above the envelope window, reference block --- */
+
+.letter__letterhead {
+  margin-block-end: 12mm;
+}
+
+.letter__letterhead .org-wordmark {
+  font-size: 13pt;
+  font-weight: 700;
+  margin: 0 0 10mm;
+}
+
+.letter__letterhead .return-address {
+  font-style: normal;
+  font-size: 7.5pt;
+  white-space: pre-line;
+  color: #555;
+  margin-block-end: 2mm;
+}
+
+/* Envelope-window position (~C5 venstercouvert): recipient block. */
+.letter__letterhead .address-window {
+  min-height: 22mm;
+  font-style: normal;
+  white-space: pre-line;
+  margin-block-end: 8mm;
+}
+
+.letter__letterhead .reference {
+  display: flex;
+  gap: 10mm;
+  font-size: 8.5pt;
+  color: #333;
+}
+
+.letter__letterhead .reference dt {
+  font-weight: 700;
+  margin: 0;
+}
+
+.letter__letterhead .reference dd {
+  margin: 0;
+}
+
+/* --- Body: the case-type template's sections --- */
+
+.letter__body {
+  flex: 1;
+  /* Above the absolutely-positioned page-break marks: the dashed line stays visible
+     in the gaps but never draws THROUGH opaque content (editors, pickers). */
+  position: relative;
+  z-index: 1;
+}
+
+.letter__body h3 {
+  font-size: inherit;
+  font-weight: 700;
+  margin: 0 0 0.25em;
+}
+
+.letter__body section {
+  margin-block-end: 1.5em;
+}
+
+/* --- Signature --- */
+
+.letter__signature {
+  margin-block-start: 10mm;
+}
+
+.letter__signature p {
+  margin: 0;
+}
+
+.letter__signature .signature-name {
+  margin-block-start: 3em; /* room for the (not-shipped) handwritten signature */
+  font-weight: 700;
+}
+
+/* --- Footer: contact + legal, above a rule --- */
+
+.letter__footer {
+  margin-block-start: 10mm;
+  padding-block-start: 3mm;
+  border-block-start: 0.5pt solid #999;
+  font-size: 7.5pt;
+  color: #555;
+  display: flex;
+  justify-content: space-between;
+  gap: 10mm;
+}
+
+.letter__footer .footer-contact {
+  white-space: pre-line;
+}
+
+.letter__footer .footer-legal {
+  text-align: end;
+}
+
+/* --- Approximate page-break indicator (screen only; PRD §2b honesty rule) ---
+   Positioned per A4-interval by the canvas; the print preview is authoritative. */
+
+.letter__page-break {
+  position: absolute;
+  inset-inline: 0;
+  border-block-start: 1px dashed #b36200;
+  pointer-events: none;
+}
+
+.letter__page-break > span {
+  position: absolute;
+  inset-inline-end: 2mm;
+  inset-block-start: 0;
+  transform: translateY(-50%);
+  /* Above .letter__body: the honesty caption stays legible even over content. */
+  z-index: 2;
+  font-size: 7pt;
+  color: #b36200;
+  background: #fff;
+  padding-inline: 1mm;
+  white-space: nowrap;
+}
+
+/* --- Print: real pages, no indicator chrome --- */
+
+@page {
+  size: A4;
+  margin: 0;
+}
+
+@media print {
+  .letter {
+    width: auto;
+    min-height: 0;
+  }
+
+  .letter__page-break {
+    display: none;
+  }
+}
+.preview-watermark {
+  position: fixed;
+  inset: 0;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  font-size: 72pt;
+  font-weight: 700;
+  color: rgb(200 30 30 / 0.18);
+  transform: rotate(-30deg);
+  pointer-events: none;
+  z-index: 3;
+}
+.org-logo {
+  display: block;
+  max-height: 18mm;
+  margin-block-end: 4mm;
+}</style></head><body><div class="letter" style="--letter-margin-top:25mm;--letter-margin-right:20mm;--letter-margin-bottom:20mm;--letter-margin-left:25mm;"><div class="letter__letterhead"><p class="org-wordmark">BIG-register</p><address class="return-address">Retouradres: Postbus 00000, 2500 AA Den Haag</address><address class="address-window">Adres van de geadresseerde<br>(wordt ingevuld bij verzending)</address><dl class="reference"><div><dt>Ons kenmerk</dt><dd>golden-brief-1</dd></div><div><dt>Datum</dt><dd>5 juli 2026</dd></div></dl></div><div class="letter__body"><section><h3>Aanhef</h3><p>Geachte heer/mevrouw Dr. A. (Anna) de Vries,</p></section><section><h3>Kern van het besluit</h3><p>Op </p><ul><li>Eerste punt: [NOG IN TE VULLEN: Reden besluit]</li><li>Tweede punt</li></ul></section><section><h3>Slot</h3><p>Met vriendelijke groet,</p></section></div><div class="letter__signature"><p>Met vriendelijke groet,</p><p class="signature-name">A. de Vries</p><p>Hoofd Registratie, BIG-register</p></div><div class="letter__footer"><div class="footer-contact">BIG-register &#183; Postbus 00000, 2500 AA Den Haag &#183; 070 000 00 00 &#183; info@voorbeeld.example</div><div class="footer-legal">Dit is een gegenereerd voorbeelddocument uit de register-reference PoC. Alle gegevens zijn fictief.</div></div><div class="preview-watermark" aria-hidden="true">VOORBEELD</div></div></body></html>

backend/tests/BigRegister.Tests/LetterHtmlTests.cs

@@ -0,0 +1,102 @@
+using System.Text.RegularExpressions;
+using BigRegister.Api.Contracts;
+using BigRegister.Api.Data;
+using BigRegister.Domain.Letters;
+
+namespace BigRegister.Tests;
+
+/// <summary>
+/// WP-25's fence against drift between the backend renderer and the FE letter
+/// canvas: a golden-file snapshot of a fixed brief + template, and a class-parity
+/// check that every `letter`-prefixed class the renderer emits exists in the
+/// shared `public/letter.css` contract. Neither test launches a browser.
+/// </summary>
+public class LetterHtmlTests
+{
+  private static BriefEntity FixtureBrief() => new()
+  {
+    BriefId = "golden-brief-1",
+    Owner = "golden",
+    Beroep = "arts",
+    TemplateId = "besluit-arts",
+    DrafterId = BriefStore.DrafterId,
+    Placeholders = new[]
+    {
+      new PlaceholderDefDto("naam_zorgverlener", "Naam zorgverlener", true),
+      new PlaceholderDefDto("datum", "Datum", true),
+      new PlaceholderDefDto("reden_besluit", "Reden besluit", false),
+    },
+    Sections = new()
+    {
+      new("aanhef", "Aanhef", true, new List<LetterBlockDto>
+      {
+        new("freeText", "aanhef-1", new RichTextBlockDto(new[]
+        {
+          new ParagraphDto(new[]
+          {
+            new RichTextNodeDto("text", Text: "Geachte heer/mevrouw "),
+            new RichTextNodeDto("placeholder", Key: "naam_zorgverlener"),
+            new RichTextNodeDto("text", Text: ","),
+          }),
+        })),
+      }, Locked: true),
+      new("kern", "Kern van het besluit", true, new List<LetterBlockDto>
+      {
+        new("freeText", "kern-1", new RichTextBlockDto(new[]
+        {
+          new ParagraphDto(new[] { new RichTextNodeDto("text", Text: "Op ") }),
+          new ParagraphDto(new RichTextNodeDto[]
+          {
+            new("text", Text: "Eerste punt: "),
+            new("placeholder", Key: "reden_besluit"),
+          }, List: "bullet"),
+          new ParagraphDto(new RichTextNodeDto[]
+          {
+            new("text", Text: "Tweede punt"),
+          }, List: "bullet"),
+        })),
+      }),
+      new("slot", "Slot", false, new List<LetterBlockDto>
+      {
+        new("freeText", "slot-1", new RichTextBlockDto(new[]
+        {
+          new ParagraphDto(new[] { new RichTextNodeDto("text", Text: "Met vriendelijke groet,") }),
+        })),
+      }, Locked: true),
+    },
+    Status = new BriefStatusDto("draft"),
+  };
+
+  private static readonly OrgTemplateDto Template = new(
+      "cibg-registers", "BIG-register",
+      "Retouradres: Postbus 00000, 2500 AA Den Haag",
+      LogoDocumentId: null,
+      "BIG-register · Postbus 00000, 2500 AA Den Haag · 070 000 00 00 · info@voorbeeld.example",
+      "Dit is een gegenereerd voorbeelddocument uit de register-reference PoC. Alle gegevens zijn fictief.",
+      "A. de Vries", "Hoofd Registratie, BIG-register", "Met vriendelijke groet,",
+      new MarginsDto(25, 20, 20, 25), Version: 1);
+
+  private const string At = "2026-07-05T12:00:00.0000000+00:00";
+
+  private static readonly string GoldenPath = Path.Combine(AppContext.BaseDirectory, "LetterHtml.golden.html");
+
+  [Fact]
+  public void Render_matches_the_golden_file()
+  {
+    var html = LetterHtml.Render(FixtureBrief(), Template, At, watermark: true);
+    var golden = File.ReadAllText(GoldenPath);
+    Assert.Equal(golden, html);
+  }
+
+  [Fact]
+  public void Every_letter_prefixed_class_exists_in_letter_css()
+  {
+    var html = LetterHtml.Render(FixtureBrief(), Template, At, watermark: true);
+    var classes = Regex.Matches(html, "class=\"([^\"]+)\"")
+        .SelectMany(m => m.Groups[1].Value.Split(' '))
+        .Where(c => c.StartsWith("letter"))
+        .Distinct();
+    Assert.NotEmpty(classes);
+    Assert.All(classes, c => Assert.Contains($".{c}", LetterHtml.StyleSheet));
+  }
+}

backend/tests/BigRegister.Tests/PreviewEndpointTests.cs

@@ -0,0 +1,96 @@
+using System.Net;
+using System.Net.Http.Json;
+using BigRegister.Api.Contracts;
+using BigRegister.Api.Data;
+using Microsoft.AspNetCore.Mvc.Testing;
+
+namespace BigRegister.Tests;
+
+/// <summary>
+/// WP-25: the two HTML preview endpoints. Both are excluded from the OpenAPI doc
+/// (see the drift check in the API-client generation step) — these tests hit them
+/// as plain HTTP, the same way the hand-written FE fetch does.
+/// </summary>
+public class PreviewEndpointTests(TestWebApplicationFactory factory) : IClassFixture<TestWebApplicationFactory>
+{
+  private const string Registers = OrgTemplateSeed.Registers;
+  private readonly HttpClient _client = factory.CreateClient();
+
+  private static LetterBlockDto FreeText(string id) =>
+      new("freeText", id, new RichTextBlockDto(new[] { new ParagraphDto(new[] { new RichTextNodeDto("text", Text: "inhoud") }) }));
+
+  private static SaveBriefRequest FilledFrom(BriefDto brief)
+  {
+    var i = 0;
+    var sections = brief.Sections
+        .Select(s => new LetterSectionDto(s.SectionKey, s.Title, s.Required, s.Required ? new[] { FreeText($"local-{++i}") } : s.Blocks))
+        .ToList();
+    return new SaveBriefRequest(sections);
+  }
+
+  private static void ResetStores()
+  {
+    BriefStore.Reset();
+    OrgTemplateStore.Reset();
+  }
+
+  private HttpRequestMessage Req(HttpMethod method, string path, string? role = null) =>
+      role is null ? new HttpRequestMessage(method, path) : new HttpRequestMessage(method, path) { Headers = { { "X-Role", role } } };
+
+  [Fact]
+  public async Task Preview_of_an_unsent_brief_renders_live_with_a_watermark()
+  {
+    ResetStores();
+    await _client.GetAsync("/api/v1/brief"); // GetOrCreate the demo draft
+
+    var res = await _client.GetAsync("/api/v1/brief/preview");
+    res.EnsureSuccessStatusCode();
+    Assert.Equal("text/html", res.Content.Headers.ContentType?.MediaType);
+    var html = await res.Content.ReadAsStringAsync();
+    Assert.Contains("<div class=\"preview-watermark\"", html);
+  }
+
+  [Fact]
+  public async Task Preview_of_a_sent_brief_serves_the_archive_unchanged_after_a_republish()
+  {
+    ResetStores();
+    var brief = (await _client.GetFromJsonAsync<BriefViewDto>("/api/v1/brief"))!.Brief;
+    await _client.PutAsJsonAsync("/api/v1/brief", FilledFrom(brief));
+    await _client.SendAsync(Req(HttpMethod.Post, "/api/v1/brief/submit"));
+    await _client.SendAsync(Req(HttpMethod.Post, "/api/v1/brief/approve", role: "approver"));
+    await _client.SendAsync(Req(HttpMethod.Post, "/api/v1/brief/send"));
+
+    var sentHtml = await (await _client.GetAsync("/api/v1/brief/preview")).Content.ReadAsStringAsync();
+    Assert.DoesNotContain("<div class=\"preview-watermark\"", sentHtml);
+    Assert.Contains("BIG-register", sentHtml);
+
+    // Republish the org template under a new name.
+    var adminView = await _client.SendAsync(Req(HttpMethod.Get, $"/api/v1/admin/org-template/{Registers}", role: "admin"));
+    var draft = (await adminView.Content.ReadFromJsonAsync<OrgTemplateAdminViewDto>())!.Draft;
+    await _client.SendAsync(new HttpRequestMessage(HttpMethod.Put, $"/api/v1/admin/org-template/{Registers}")
+    {
+      Headers = { { "X-Role", "admin" } },
+      Content = JsonContent.Create(new SaveOrgTemplateRequest(draft with { OrgName = "Hertitelde organisatie" })),
+    });
+    await _client.SendAsync(Req(HttpMethod.Post, $"/api/v1/admin/org-template/{Registers}/publish", role: "admin"));
+
+    // The sent brief's preview is unchanged — still the archived rendering.
+    var afterRepublish = await (await _client.GetAsync("/api/v1/brief/preview")).Content.ReadAsStringAsync();
+    Assert.Equal(sentHtml, afterRepublish);
+    Assert.DoesNotContain("Hertitelde organisatie", afterRepublish);
+  }
+
+  [Fact]
+  public async Task Proefbrief_is_admin_only_and_renders_the_draft_template()
+  {
+    ResetStores();
+    Assert.Equal(HttpStatusCode.Forbidden,
+        (await _client.GetAsync($"/api/v1/admin/org-template/{Registers}/preview")).StatusCode);
+
+    var res = await _client.SendAsync(Req(HttpMethod.Get, $"/api/v1/admin/org-template/{Registers}/preview", role: "admin"));
+    res.EnsureSuccessStatusCode();
+    var html = await res.Content.ReadAsStringAsync();
+    Assert.Contains("BIG-register", html);
+    Assert.Contains("<div class=\"preview-watermark\"", html);
+  }
+}

docker-compose.yml

@@ -16,6 +16,11 @@ services:
       - ./backend:/src:z
       - api-bin:/src/src/BigRegister.Api/bin
       - api-obj:/src/src/BigRegister.Api/obj
+      # WP-25: LetterHtml.Render inlines public/letter.css (the FE⇄BE letter
+      # contract, repo-root sibling of backend/) — mounted here so the same
+      # walk-up-from-the-assembly lookup that works for `dotnet run`/tests also
+      # resolves inside this container, whose bind mount otherwise only sees backend/.
+      - ./public:/src/public:z
     ports:
       - '5000:5000'
 

docs/backlog/README.md

@@ -70,7 +70,7 @@ for its existing violations, so every WP ends green.
 | [WP-23](WP-23-org-template-backend.md)  | Org-template backend + admin role                            | 6 · Brief v2                | done   |
 | [WP-24](WP-24-letter-canvas.md)         | Letter canvas (edit on the letter)                           | 6 · Brief v2                | done   |
 | [WP-25](WP-25-letter-preview-html.md)   | Server-rendered letter preview (HTML; PDF deferred)          | 6 · Brief v2                | todo   |
-| [WP-26](WP-26-org-template-editor.md)   | Admin org-template editor                                    | 6 · Brief v2                | todo   |
+| [WP-26](WP-26-org-template-editor.md)   | Admin org-template editor                                    | 6 · Brief v2                | done   |
 | [WP-27](WP-27-brief-ux-layer.md)        | Brief UX layer (undo/redo, standaardbrief, diff)             | 6 · Brief v2                | todo   |
 | [WP-28](WP-28-brief-v2-demo-polish.md)  | Brief v2 demo polish (scenarios, e2e, docs)                  | 6 · Brief v2                | todo   |
 

docs/backlog/WP-25-letter-preview-html.md

@@ -1,6 +1,6 @@
 # WP-25 — Server-rendered letter preview (HTML; PDF seam deferred)
 
-Status: todo
+Status: done
 Phase: 6 — Brief v2 (edit-on-the-letter, org templates, server-rendered preview)
 
 ## Why
@@ -63,13 +63,13 @@ same composition is archived with the brief, making sent letters immutable.
 
 ## Acceptance criteria
 
-- [ ] Preview opens the composed print-ready letter in a new tab; browser print
+- [x] Preview opens the composed print-ready letter in a new tab; browser print
       shows correct margins via `@page`.
-- [ ] Unresolved manual placeholders render `[NOG IN TE VULLEN: …]`; preview works
+- [x] Unresolved manual placeholders render `[NOG IN TE VULLEN: …]`; preview works
       despite lint errors (only send blocks).
-- [ ] A sent brief serves its archived HTML unchanged after an org-template republish.
+- [x] A sent brief serves its archived HTML unchanged after an org-template republish.
-- [ ] Golden + parity tests green without any browser installed.
+- [x] Golden + parity tests green without any browser installed.
-- [ ] `swagger.json` unchanged by the two endpoints (drift check green).
+- [x] `swagger.json` unchanged by the two endpoints (drift check green).
 
 ## Verification
 

docs/backlog/WP-26-org-template-editor.md

@@ -1,6 +1,6 @@
 # WP-26 — Admin org-template editor
 
-Status: todo
+Status: done
 Phase: 6 — Brief v2 (edit-on-the-letter, org templates, server-rendered preview)
 
 ## Why
@@ -58,17 +58,45 @@ content a read-only sample). PRD Brief v2 §5, §7h.
 
 ## Acceptance criteria
 
-- [ ] `?role=admin` can switch sub-orgs, edit all template fields in place on the
+- [x] `?role=admin` can switch sub-orgs, edit all template fields in place on the
       canvas, and see the canvas update live.
-- [ ] Draft saves are debounced; publish asks for confirmation showing the impact
+- [x] Draft saves are debounced; publish asks for confirmation showing the impact
       count; after publish the drafter's canvas (WP-24) reflects it on reload.
-- [ ] Version history lists published versions (who is faked, when is real);
+- [x] Version history lists published versions (who is faked, when is real);
       rollback copies an old version into the draft.
-- [ ] Non-admin on `/brief/huisstijl` sees the denial alert; API would 403 anyway.
+- [x] Non-admin on `/brief/huisstijl` sees the denial alert; API would 403 anyway.
-- [ ] Logo upload validates type/size client-side (existing `rejectReason`) and
+- [x] Logo upload validates type/size client-side (existing `rejectReason`) and
       renders on the canvas after upload.
-- [ ] Machine spec covers field edits, dirty tracking, publish/rollback outcomes.
+- [x] Machine spec covers field edits, dirty tracking, publish/rollback outcomes.
-- [ ] Full GREEN.
+- [x] Full GREEN.
+
+## Deviations / notes (as built)
+
+- **`check:tokens` was already red on `main`** (WP-24's canvas landed `var(--rhc-*,
+  #hex)` fallbacks + an `rgb()` paper shadow, and WP-25 committed over it). Fixed here
+  to end GREEN: dropped the redundant hex fallbacks (the token bridge defines every
+  one) and marked the paper drop-shadow `token-ok`; also fixed a pre-existing
+  `passage-picker` `var(--rhc-color-wit, #fff)` hit.
+- **Canvas edit-in-place**: `editableRegions='template'` now renders the seven
+  org-identity text fields as inline `<input>`/`<textarea>` controls (aria-labelled)
+  and shows the logo `<img>`; the letter body stays a read-only sample
+  (`SAMPLE_LETTER_BRIEF`). `logoUrl` input added to the canvas and wired through the
+  composer too, so a published logo shows to the drafter (AC2).
+- **Load-effect loop (caught in the live walk)**: the page's initial-load effect must
+  NOT read the store model — `load()` dispatches `Loading` (a fresh object), which
+  would retrigger a model-reading effect into a runaway loop that saturated the page.
+  Gated on `canEdit()` + a plain `loadRequested` flag instead.
+- **`AccessStore.ready`** added (tiny): a page-level capability gate needs to tell
+  "still loading `/me`" from "denied" so an admin doesn't flash the denial alert.
+- **`uploadContentUrl`** pure helper extracted from `UploadAdapter.contentUrl` so
+  `BriefStore` can build a logo `src` without pulling `ApiClient` into its DI graph
+  (kept its spec green).
+- **Role caching caveat**: `/me` loads once. Open the app with `?role=admin` from the
+  first navigation that touches the editor (the dev role stub, like `?scenario=`);
+  switching role mid-session won't refetch capabilities (out of scope, POC).
+- **Dirty race**: `DraftSaved` carries the saved draft and clears `dirty` only if it's
+  reference-equal to the current draft, so an edit landing during a save round-trip
+  keeps its pending save.
 
 ## Verification
 

src/app/app.routes.ts

@@ -51,6 +51,12 @@ export const routes: Routes = [
         canActivate: [authGuard],
         loadComponent: () => import('@brief/ui/brief.page').then((m) => m.BriefPage),
       },
+      {
+        path: 'brief/huisstijl',
+        canActivate: [authGuard],
+        loadComponent: () =>
+          import('@brief/ui/org-template.page').then((m) => m.OrgTemplatePage),
+      },
       {
         path: 'concepts',
         loadComponent: () => import('./showcase/concepts.page').then((m) => m.ConceptsPage),

src/app/brief/application/brief.store.spec.ts

@@ -1,9 +1,10 @@
 import { TestBed } from '@angular/core/testing';
-import { describe, it, expect } from 'vitest';
+import { describe, it, expect, vi, afterEach } from 'vitest';
 import { Result } from '@shared/kernel/fp';
 import { Brief, BriefDecisions } from '@brief/domain/brief';
 import { OrgTemplate } from '@brief/domain/org-template';
 import { BriefAdapter, BriefView } from '@brief/infrastructure/brief.adapter';
+import { LetterPreviewAdapter } from '@brief/infrastructure/letter-preview.adapter';
 import { BriefStore } from './brief.store';
 
 const decisions: BriefDecisions = {
@@ -103,3 +104,43 @@ describe('BriefStore action state (Idle | Busy | Failed)', () => {
     expect(store.lastError()).toBeNull();
   });
 });
+
+describe('BriefStore.previewLetter', () => {
+  // vi.spyOn reuses an existing spy (and its call history) if one is already on
+  // the property — window.open/URL.createObjectURL must be restored between tests.
+  afterEach(() => vi.restoreAllMocks());
+
+  it('opens the composed letter in a new tab on success', async () => {
+    const store = setup({
+      load: (): Promise<Result<string, BriefView>> => Promise.resolve({ ok: true, value: view }),
+    });
+    await store.load();
+    const blob = new Blob(['<html></html>'], { type: 'text/html' });
+    vi.spyOn(URL, 'createObjectURL').mockReturnValue('blob:mock');
+    const open = vi.spyOn(window, 'open').mockImplementation(() => null);
+    vi.spyOn(TestBed.inject(LetterPreviewAdapter), 'preview').mockResolvedValue({
+      ok: true,
+      value: blob,
+    });
+
+    await store.previewLetter();
+    expect(open).toHaveBeenCalledWith('blob:mock', '_blank');
+    expect(store.lastError()).toBeNull();
+  });
+
+  it('surfaces the error without opening a tab on failure', async () => {
+    const store = setup({
+      load: (): Promise<Result<string, BriefView>> => Promise.resolve({ ok: true, value: view }),
+    });
+    await store.load();
+    const open = vi.spyOn(window, 'open').mockImplementation(() => null);
+    vi.spyOn(TestBed.inject(LetterPreviewAdapter), 'preview').mockResolvedValue({
+      ok: false,
+      error: 'De voorvertoning kon niet worden geopend.',
+    });
+
+    await store.previewLetter();
+    expect(open).not.toHaveBeenCalled();
+    expect(store.lastError()).toBe('De voorvertoning kon niet worden geopend.');
+  });
+});

src/app/brief/application/brief.store.ts

@@ -12,6 +12,8 @@ import {
 import { BriefMsg, BriefState, initial, reduce } from '@brief/domain/brief.machine';
 import { OrgTemplate } from '@brief/domain/org-template';
 import { BriefAdapter, BriefView } from '@brief/infrastructure/brief.adapter';
+import { LetterPreviewAdapter } from '@brief/infrastructure/letter-preview.adapter';
+import { uploadContentUrl } from '@shared/upload/upload.adapter';
 
 /** Transient action state (submit/approve/reject/send/resetDemo) — one tagged union
     instead of a busy boolean + a nullable error sitting side by side. */
@@ -35,6 +37,7 @@ type LoadedBriefState = Extract<BriefState, { tag: 'loaded' }>;
 @Injectable({ providedIn: 'root' })
 export class BriefStore {
   private adapter = inject(BriefAdapter);
+  private previewAdapter = inject(LetterPreviewAdapter);
   private store = createStore<BriefState, BriefMsg>(initial, reduce);
 
   readonly model = this.store.model;
@@ -54,6 +57,12 @@ export class BriefStore {
       stays untouched by design). Set from every server view that carries it. */
   readonly orgTemplate = signal<OrgTemplate | null>(null);
 
+  /** The org logo's content URL for the letterhead, or null when the template has none. */
+  readonly logoUrl = computed<string | null>(() => {
+    const id = this.orgTemplate()?.logoDocumentId;
+    return id ? uploadContentUrl(id) : null;
+  });
+
   /** The load lifecycle as `RemoteData`, for `<app-async>` — the machine keeps
       owning the letter's own domain lifecycle (draft/submitted/approved/…); this is
       purely a projection of its loading/failed tags onto the shared async seam. */
@@ -147,6 +156,20 @@ export class BriefStore {
   reject = (comments: string) => this.transition(() => this.adapter.reject(comments));
   send = () => this.transition(() => this.adapter.send());
 
+  /** Explicit action, never a live re-render (PRD §8): opens the server-composed
+      letter in a new tab. ponytail: the blob URL is never revoked — it's cheap and
+      the tab outlives this call; not worth a teardown hook for a POC. */
+  async previewLetter() {
+    this.actionState.set({ tag: 'Busy' });
+    const r = await this.previewAdapter.preview();
+    if (!r.ok) {
+      this.actionState.set({ tag: 'Failed', error: r.error });
+      return;
+    }
+    this.actionState.set({ tag: 'Idle' });
+    window.open(URL.createObjectURL(r.value), '_blank');
+  }
+
   // A transition: flush any pending save, call the server (authoritative), then mirror
   // the returned status through the pure reducer's guarded transition.
   private async transition(action: () => Promise<Result<string, BriefView>>) {

src/app/brief/application/org-template.store.ts

@@ -0,0 +1,271 @@
+import { Injectable, computed, effect, inject, signal } from '@angular/core';
+import { RemoteData } from '@shared/application/remote-data';
+import { createStore } from '@shared/application/store';
+import { UploadAdapter } from '@shared/upload/upload.adapter';
+import { UploadShellService } from '@shared/upload/upload-shell.service';
+import { UploadMsg, initialUpload, rejectReason } from '@shared/upload/upload.machine';
+import {
+  MARGIN_MAX_MM,
+  MARGIN_MIN_MM,
+  OrgTemplate,
+  SubOrgSummary,
+} from '@brief/domain/org-template';
+import {
+  OrgTemplateMsg,
+  OrgTemplateState,
+  initial,
+  reduce,
+} from '@brief/domain/org-template.machine';
+import { OrgTemplateAdapter } from '@brief/infrastructure/org-template.adapter';
+
+/** Transient action state for publish/rollback/proefbrief — the BriefStore idiom. */
+type ActionState = { tag: 'Idle' } | { tag: 'Busy' } | { tag: 'Failed'; error: string };
+type SaveState = { tag: 'Idle' } | { tag: 'Saving' } | { tag: 'Saved' } | { tag: 'Error' };
+type LoadedState = Extract<OrgTemplateState, { tag: 'loaded' }>;
+
+const LOGO_CATEGORY = 'org-logo';
+const NO_SUBORGS = $localize`:@@orgTemplate.noSubOrgs:Er zijn geen organisatiesjablonen om te beheren.`;
+
+/**
+ * Root singleton for the admin org-template editor (WP-26). The Elm machine owns the
+ * editable draft; commands here do the debounced save, publish (impact-confirm),
+ * rollback and proefbrief, then dispatch the outcome — the reducer stays pure. The
+ * logo upload reuses the shared upload transport; its completion mutates the draft
+ * (in the reducer) and triggers a save (here). Mirrors `BriefStore`.
+ */
+@Injectable({ providedIn: 'root' })
+export class OrgTemplateStore {
+  private adapter = inject(OrgTemplateAdapter);
+  private uploadAdapter = inject(UploadAdapter);
+  private shell = inject(UploadShellService);
+  private store = createStore<OrgTemplateState, OrgTemplateMsg>(initial, reduce);
+
+  readonly model = this.store.model;
+
+  readonly subOrgs = signal<readonly SubOrgSummary[]>([]);
+  readonly selectedSubOrgId = signal<string | null>(null);
+
+  private actionState = signal<ActionState>({ tag: 'Idle' });
+  readonly busy = computed(() => this.actionState().tag === 'Busy');
+  readonly lastError = computed(() => {
+    const s = this.actionState();
+    return s.tag === 'Failed' ? s.error : null;
+  });
+  readonly saveState = signal<SaveState>({ tag: 'Idle' });
+
+  /** The publish impact-confirm gate (PRD §7h: show N affected letters before POST). */
+  readonly pendingPublish = signal(false);
+
+  readonly remoteData = computed<RemoteData<Error | undefined, LoadedState>>(() => {
+    const s = this.model();
+    switch (s.tag) {
+      case 'loading':
+        return { tag: 'Loading' };
+      case 'failed':
+        return { tag: 'Failure', error: new Error(s.reason) };
+      case 'loaded':
+        return { tag: 'Success', value: s };
+    }
+  });
+
+  private loaded = computed<LoadedState | null>(() => {
+    const s = this.model();
+    return s.tag === 'loaded' ? s : null;
+  });
+  readonly draft = computed<OrgTemplate | null>(() => this.loaded()?.draft ?? null);
+  readonly uploadState = computed(() => this.loaded()?.upload ?? initialUpload);
+  readonly history = computed(() => this.loaded()?.history ?? []);
+  readonly publishedVersion = computed(() => this.loaded()?.publishedVersion ?? 0);
+  readonly unsentBriefs = computed(() => this.loaded()?.unsentBriefs ?? 0);
+  readonly logoUrl = computed<string | null>(() => {
+    const id = this.draft()?.logoDocumentId;
+    return id ? this.uploadAdapter.contentUrl(id) : null;
+  });
+
+  /** Client-side mirror of the server rules (`OrgTemplateRules`) for instant feedback;
+      the server re-validates and stays the authority — publish is gated on this. */
+  readonly draftValid = computed(() => {
+    const d = this.draft();
+    if (!d) return false;
+    const marginsOk = [d.margins.topMm, d.margins.rightMm, d.margins.bottomMm, d.margins.leftMm].every(
+      (v) => v >= MARGIN_MIN_MM && v <= MARGIN_MAX_MM,
+    );
+    return d.orgName.trim().length > 0 && d.signatureName.trim().length > 0 && marginsOk;
+  });
+
+  // Live File blobs keyed by localId — needed to retry a failed upload (a reducer can't hold these).
+  private files = new Map<string, File>();
+  private categoriesRes = this.uploadAdapter.categoriesResource('org-template');
+
+  constructor() {
+    // Feed the logo category into the machine's upload sub-state once loaded. Tracks
+    // `model()` so it re-fires after a sub-org switch reseeds an empty upload state;
+    // the length guard makes it idempotent (no dispatch loop).
+    effect(() => {
+      const s = this.model();
+      if (s.tag !== 'loaded' || s.upload.categories.length > 0) return;
+      const status = this.categoriesRes.status();
+      if (status === 'resolved' || status === 'local')
+        this.dispatchUpload({ type: 'CategoriesLoaded', categories: this.categoriesRes.value() ?? [] });
+    });
+  }
+
+  async load() {
+    this.store.dispatch({ tag: 'Loading' });
+    const list = await this.adapter.list();
+    if (!list.ok) {
+      this.store.dispatch({ tag: 'LoadFailed', reason: list.error });
+      return;
+    }
+    this.subOrgs.set(list.value);
+    const first = list.value[0];
+    if (!first) {
+      this.store.dispatch({ tag: 'LoadFailed', reason: NO_SUBORGS });
+      return;
+    }
+    await this.selectSubOrg(first.subOrgId);
+  }
+
+  async selectSubOrg(subOrgId: string) {
+    this.selectedSubOrgId.set(subOrgId);
+    this.saveState.set({ tag: 'Idle' });
+    clearTimeout(this.saveTimer);
+    this.store.dispatch({ tag: 'Loading' });
+    const r = await this.adapter.load(subOrgId);
+    if (r.ok) this.store.dispatch({ tag: 'DraftLoaded', view: r.value });
+    else this.store.dispatch({ tag: 'LoadFailed', reason: r.error });
+  }
+
+  /** An in-place canvas or margin edit: apply optimistically, then debounce-save. */
+  edit(msg: OrgTemplateMsg) {
+    this.store.dispatch(msg);
+    this.scheduleSave();
+  }
+
+  private saveTimer?: ReturnType<typeof setTimeout>;
+  private scheduleSave() {
+    if (this.loaded() === null) return;
+    clearTimeout(this.saveTimer);
+    // ponytail: 600ms debounce, same as BriefStore; the server is the store of record.
+    this.saveTimer = setTimeout(() => void this.flushSave(), 600);
+  }
+  private async flushSave() {
+    const s = this.loaded();
+    if (!s || !s.dirty) return;
+    const { subOrgId, draft } = s;
+    this.saveState.set({ tag: 'Saving' });
+    const r = await this.adapter.save(subOrgId, draft);
+    if (r.ok) {
+      this.saveState.set({ tag: 'Saved' });
+      this.store.dispatch({ tag: 'DraftSaved', savedDraft: draft });
+    } else {
+      this.saveState.set({ tag: 'Error' });
+      this.actionState.set({ tag: 'Failed', error: r.error });
+    }
+  }
+
+  // --- publish (impact-confirm) / rollback / proefbrief ---
+
+  requestPublish() {
+    this.pendingPublish.set(true);
+  }
+  cancelPublish() {
+    this.pendingPublish.set(false);
+  }
+  async confirmPublish() {
+    const s = this.loaded();
+    if (!s) return;
+    this.pendingPublish.set(false);
+    this.actionState.set({ tag: 'Busy' });
+    clearTimeout(this.saveTimer);
+    await this.flushSave(); // publish the saved draft — flush any pending edit first
+    const r = await this.adapter.publish(s.subOrgId);
+    if (!r.ok) {
+      this.actionState.set({ tag: 'Failed', error: r.error });
+      return;
+    }
+    this.actionState.set({ tag: 'Idle' });
+    await this.selectSubOrg(s.subOrgId); // reload: new version, history, unsentBriefs = 0
+  }
+
+  async rollback(version: number) {
+    const s = this.loaded();
+    if (!s) return;
+    this.actionState.set({ tag: 'Busy' });
+    clearTimeout(this.saveTimer);
+    const r = await this.adapter.rollback(s.subOrgId, version);
+    if (!r.ok) {
+      this.actionState.set({ tag: 'Failed', error: r.error });
+      return;
+    }
+    this.actionState.set({ tag: 'Idle' });
+    this.store.dispatch({ tag: 'DraftLoaded', view: r.value }); // old version copied into draft
+  }
+
+  async proefbrief() {
+    const s = this.loaded();
+    if (!s) return;
+    this.actionState.set({ tag: 'Busy' });
+    clearTimeout(this.saveTimer);
+    await this.flushSave(); // the proefbrief renders the server's draft
+    const r = await this.adapter.proefbrief(s.subOrgId);
+    if (!r.ok) {
+      this.actionState.set({ tag: 'Failed', error: r.error });
+      return;
+    }
+    this.actionState.set({ tag: 'Idle' });
+    window.open(URL.createObjectURL(r.value), '_blank');
+  }
+
+  // --- logo upload (reuses the shared upload transport; single `org-logo` file) ---
+
+  onLogoSelected(files: File[]) {
+    const s = this.loaded();
+    const cat = s?.upload.categories.find((c) => c.categoryId === LOGO_CATEGORY);
+    const file = files[0];
+    if (!s || !cat || !file) return;
+    const reason = rejectReason(cat, { type: file.type, sizeMb: file.size / 1e6 });
+    if (reason) {
+      this.dispatchUpload({ type: 'FileRejected', categoryId: cat.categoryId, reason });
+      return;
+    }
+    const localId = crypto.randomUUID();
+    this.files.set(localId, file);
+    this.dispatchUpload({
+      type: 'FileSelected',
+      categoryId: cat.categoryId,
+      localId,
+      fileName: file.name,
+      fileSizeMb: file.size / 1e6,
+    });
+    this.shell.upload({ localId, categoryId: cat.categoryId, wizardId: 'org-template', file }, (m) =>
+      this.onUploadMsg(m),
+    );
+  }
+
+  onLogoRemoved(localId: string) {
+    this.shell.cancel([localId]);
+    this.files.delete(localId);
+    this.onUploadMsg({ type: 'UploadRemoved', localId });
+  }
+
+  onLogoRetry(localId: string) {
+    const file = this.files.get(localId);
+    const up = this.loaded()?.upload.uploads.find((u) => u.localId === localId);
+    if (!file || !up) return;
+    this.dispatchUpload({ type: 'UploadRetried', localId });
+    this.shell.upload({ localId, categoryId: up.categoryId, wizardId: 'org-template', file }, (m) =>
+      this.onUploadMsg(m),
+    );
+  }
+
+  private dispatchUpload(msg: UploadMsg) {
+    this.store.dispatch({ tag: 'Upload', msg });
+  }
+  /** Upload effects arriving from the transport: a finished/removed logo edits the
+      draft (in the reducer) and needs persisting. */
+  private onUploadMsg(msg: UploadMsg) {
+    this.dispatchUpload(msg);
+    if (msg.type === 'UploadComplete' || msg.type === 'UploadRemoved') this.scheduleSave();
+  }
+}

src/app/brief/domain/org-template.machine.spec.ts

@@ -0,0 +1,135 @@
+import { describe, it, expect } from 'vitest';
+import { OrgTemplate, OrgTemplateAdminView } from './org-template';
+import { OrgTemplateState, reduce } from './org-template.machine';
+import { DocumentCategory } from '@shared/upload/upload.machine';
+
+const template: OrgTemplate = {
+  subOrgId: 'cibg-registers',
+  orgName: 'CIBG',
+  returnAddress: 'Postbus 1\n2500 AA Den Haag',
+  footerContact: 'info@cibg.nl',
+  footerLegal: 'CIBG is onderdeel van VWS',
+  signatureName: 'A. de Vries',
+  signatureRole: 'Hoofd Registratie',
+  signatureClosing: 'Met vriendelijke groet,',
+  margins: { topMm: 25, rightMm: 20, bottomMm: 25, leftMm: 20 },
+  version: 3,
+};
+
+const view = (over: Partial<OrgTemplateAdminView> = {}): OrgTemplateAdminView => ({
+  draft: template,
+  publishedVersion: 3,
+  history: [],
+  unsentBriefs: 2,
+  ...over,
+});
+
+const loaded = (): OrgTemplateState => reduce({ tag: 'loading' }, { tag: 'DraftLoaded', view: view() });
+
+const logoCategory: DocumentCategory = {
+  categoryId: 'org-logo',
+  label: 'Logo',
+  description: '',
+  required: false,
+  acceptedTypes: ['image/png'],
+  maxSizeMb: 2,
+  multiple: false,
+  allowPostDelivery: false,
+};
+
+describe('org-template.machine', () => {
+  it('DraftLoaded moves to loaded with the draft, clean', () => {
+    const s = loaded();
+    expect(s.tag).toBe('loaded');
+    if (s.tag !== 'loaded') return;
+    expect(s.draft.orgName).toBe('CIBG');
+    expect(s.subOrgId).toBe('cibg-registers');
+    expect(s.unsentBriefs).toBe(2);
+    expect(s.dirty).toBe(false);
+  });
+
+  it('LoadFailed carries the reason', () => {
+    const s = reduce({ tag: 'loading' }, { tag: 'LoadFailed', reason: 'boom' });
+    expect(s).toEqual({ tag: 'failed', reason: 'boom' });
+  });
+
+  it('FieldEdited edits the draft and marks dirty', () => {
+    const s = reduce(loaded(), { tag: 'FieldEdited', field: 'orgName', value: 'CIBG Nieuw' });
+    expect(s.tag === 'loaded' && s.draft.orgName).toBe('CIBG Nieuw');
+    expect(s.tag === 'loaded' && s.dirty).toBe(true);
+  });
+
+  it('MarginEdited edits one edge and marks dirty', () => {
+    const s = reduce(loaded(), { tag: 'MarginEdited', edge: 'topMm', value: 40 });
+    expect(s.tag === 'loaded' && s.draft.margins.topMm).toBe(40);
+    expect(s.tag === 'loaded' && s.draft.margins.leftMm).toBe(20);
+    expect(s.tag === 'loaded' && s.dirty).toBe(true);
+  });
+
+  it('DraftSaved clears dirty when the saved draft is the current one', () => {
+    const edited = reduce(loaded(), { tag: 'FieldEdited', field: 'orgName', value: 'X' });
+    const savedDraft = edited.tag === 'loaded' ? edited.draft : template;
+    const s = reduce(edited, { tag: 'DraftSaved', savedDraft });
+    expect(s.tag === 'loaded' && s.dirty).toBe(false);
+    expect(s.tag === 'loaded' && s.draft.orgName).toBe('X');
+  });
+
+  it('DraftSaved keeps dirty when an edit landed during the save round-trip', () => {
+    const editing = reduce(loaded(), { tag: 'FieldEdited', field: 'orgName', value: 'X' });
+    const savedDraft = editing.tag === 'loaded' ? editing.draft : template;
+    // a further edit changes the draft reference before the save resolves
+    const raced = reduce(editing, { tag: 'FieldEdited', field: 'orgName', value: 'Y' });
+    const s = reduce(raced, { tag: 'DraftSaved', savedDraft });
+    expect(s.tag === 'loaded' && s.dirty).toBe(true);
+  });
+
+  it('edits are no-ops in non-loaded states', () => {
+    expect(reduce({ tag: 'loading' }, { tag: 'FieldEdited', field: 'orgName', value: 'x' })).toEqual({
+      tag: 'loading',
+    });
+  });
+
+  it('a completed logo upload sets logoDocumentId + dirty', () => {
+    const withCat = reduce(loaded(), {
+      tag: 'Upload',
+      msg: { type: 'CategoriesLoaded', categories: [logoCategory] },
+    });
+    const selected = reduce(withCat, {
+      tag: 'Upload',
+      msg: { type: 'FileSelected', categoryId: 'org-logo', localId: 'a', fileName: 'l.png', fileSizeMb: 0.1 },
+    });
+    const done = reduce(selected, {
+      tag: 'Upload',
+      msg: { type: 'UploadComplete', localId: 'a', documentId: 'doc-1' },
+    });
+    expect(done.tag === 'loaded' && done.draft.logoDocumentId).toBe('doc-1');
+    expect(done.tag === 'loaded' && done.dirty).toBe(true);
+  });
+
+  it('removing the logo clears logoDocumentId + dirty', () => {
+    const withLogo = reduce(loaded(), {
+      tag: 'Upload',
+      msg: { type: 'UploadComplete', localId: 'a', documentId: 'doc-1' },
+    });
+    const removed = reduce(withLogo, {
+      tag: 'Upload',
+      msg: { type: 'UploadRemoved', localId: 'a' },
+    });
+    expect(removed.tag === 'loaded' && removed.draft.logoDocumentId).toBeUndefined();
+    expect(removed.tag === 'loaded' && removed.dirty).toBe(true);
+  });
+
+  it('DraftLoaded (sub-org switch) keeps the loaded logo category, drops uploads', () => {
+    const withCat = reduce(loaded(), {
+      tag: 'Upload',
+      msg: { type: 'CategoriesLoaded', categories: [logoCategory] },
+    });
+    const switched = reduce(withCat, {
+      tag: 'DraftLoaded',
+      view: view({ draft: { ...template, subOrgId: 'cibg-vakbekwaamheid' } }),
+    });
+    expect(switched.tag === 'loaded' && switched.upload.categories).toHaveLength(1);
+    expect(switched.tag === 'loaded' && switched.upload.uploads).toHaveLength(0);
+    expect(switched.tag === 'loaded' && switched.subOrgId).toBe('cibg-vakbekwaamheid');
+  });
+});

src/app/brief/domain/org-template.machine.ts

@@ -0,0 +1,100 @@
+import { assertNever } from '@shared/kernel/fp';
+import { Margins, OrgTemplate, OrgTemplateAdminView, OrgTemplateVersion } from './org-template';
+import { UploadMsg, UploadState, initialUpload, reduceUpload } from '@shared/upload/upload.machine';
+
+/**
+ * The admin org-template editor as one Elm-style machine (WP-26, PRD Brief v2 §5) —
+ * the same idiom as the wizards. The DRAFT org template is form state (edited in
+ * place on the canvas); publish/rollback are effects that come back as `DraftLoaded`.
+ * `dirty` tracks unsaved edits (the store debounce-saves them). The logo upload is
+ * the composable upload sub-machine folded in, exactly like the wizards fold
+ * `reduceUpload` — its `UploadComplete`/`UploadRemoved` also mutate `draft.logoDocumentId`.
+ */
+
+/** The org-identity text fields editable directly on the letter canvas. */
+export type OrgTemplateTextField =
+  | 'orgName'
+  | 'returnAddress'
+  | 'footerContact'
+  | 'footerLegal'
+  | 'signatureName'
+  | 'signatureRole'
+  | 'signatureClosing';
+
+export type OrgTemplateState =
+  | { tag: 'loading' }
+  | { tag: 'failed'; reason: string }
+  | {
+      tag: 'loaded';
+      subOrgId: string;
+      draft: OrgTemplate;
+      publishedVersion: number;
+      history: readonly OrgTemplateVersion[];
+      unsentBriefs: number;
+      dirty: boolean;
+      /** Logo upload sub-state (single file, `org-logo` category). */
+      upload: UploadState;
+    };
+
+export const initial: OrgTemplateState = { tag: 'loading' };
+
+export type OrgTemplateMsg =
+  | { tag: 'Loading' }
+  | { tag: 'DraftLoaded'; view: OrgTemplateAdminView }
+  | { tag: 'LoadFailed'; reason: string }
+  | { tag: 'FieldEdited'; field: OrgTemplateTextField; value: string }
+  | { tag: 'MarginEdited'; edge: keyof Margins; value: number }
+  /** Carries the draft that was saved: clears `dirty` only if no edit landed during
+      the round-trip (reference-equal), so a concurrent edit keeps its pending save. */
+  | { tag: 'DraftSaved'; savedDraft: OrgTemplate }
+  | { tag: 'Upload'; msg: UploadMsg };
+
+/** Edit the loaded draft; a no-op in any non-loaded state (illegal by construction). */
+function editDraft(
+  s: OrgTemplateState,
+  f: (draft: OrgTemplate) => OrgTemplate,
+): OrgTemplateState {
+  return s.tag === 'loaded' ? { ...s, draft: f(s.draft), dirty: true } : s;
+}
+
+export function reduce(s: OrgTemplateState, m: OrgTemplateMsg): OrgTemplateState {
+  switch (m.tag) {
+    case 'Loading':
+      return { tag: 'loading' };
+    case 'LoadFailed':
+      return { tag: 'failed', reason: m.reason };
+    case 'DraftLoaded':
+      return {
+        tag: 'loaded',
+        subOrgId: m.view.draft.subOrgId,
+        draft: m.view.draft,
+        publishedVersion: m.view.publishedVersion,
+        history: m.view.history,
+        unsentBriefs: m.view.unsentBriefs,
+        dirty: false,
+        // Keep the loaded logo category across sub-org switches (it's the same
+        // `org-logo` category, loaded once); drop only any in-flight/finished uploads.
+        upload: s.tag === 'loaded' ? { ...s.upload, uploads: [], rejections: {} } : initialUpload,
+      };
+    case 'FieldEdited':
+      return editDraft(s, (d) => ({ ...d, [m.field]: m.value }));
+    case 'MarginEdited':
+      return editDraft(s, (d) => ({ ...d, margins: { ...d.margins, [m.edge]: m.value } }));
+    case 'DraftSaved':
+      return s.tag === 'loaded' && s.draft === m.savedDraft ? { ...s, dirty: false } : s;
+    case 'Upload': {
+      if (s.tag !== 'loaded') return s;
+      const upload = reduceUpload(s.upload, m.msg);
+      // A completed/removed logo upload also updates the draft's logoDocumentId.
+      if (m.msg.type === 'UploadComplete')
+        return { ...s, upload, draft: { ...s.draft, logoDocumentId: m.msg.documentId }, dirty: true };
+      if (m.msg.type === 'UploadRemoved') {
+        const { logoDocumentId: _dropped, ...rest } = s.draft;
+        return { ...s, upload, draft: rest, dirty: true };
+      }
+      return { ...s, upload };
+    }
+    default:
+      return assertNever(m);
+  }
+}

src/app/brief/domain/org-template.ts

@@ -29,3 +29,39 @@ export interface OrgTemplate {
   /** 0 = draft; n>0 = the published snapshot this letter renders with. */
   readonly version: number;
 }
+
+// --- admin editor (WP-26) ---
+
+/** A published snapshot in the version history: who is faked, `publishedAt` is real. */
+export interface OrgTemplateVersion {
+  readonly version: number;
+  readonly publishedAt: string;
+  readonly template: OrgTemplate;
+}
+
+/** The admin editor's view of one sub-org: the editable draft plus publish metadata. */
+export interface OrgTemplateAdminView {
+  readonly draft: OrgTemplate;
+  readonly publishedVersion: number;
+  readonly history: readonly OrgTemplateVersion[];
+  /** How many not-yet-sent letters a publish would re-render (the impact count). */
+  readonly unsentBriefs: number;
+}
+
+/** One row in the sub-org switcher. */
+export interface SubOrgSummary {
+  readonly subOrgId: string;
+  readonly orgName: string;
+  readonly publishedVersion: number;
+}
+
+/** Publish outcome: the new version and how many unsent letters it touched. */
+export interface PublishResult {
+  readonly version: number;
+  readonly affectedUnsentBriefs: number;
+}
+
+/** Margin bounds (server-owned, `OrgTemplateRules`): the FE mirrors them for instant
+    feedback via `<input min max>`; the server re-validates and stays the authority. */
+export const MARGIN_MIN_MM = 10;
+export const MARGIN_MAX_MM = 50;

src/app/brief/infrastructure/letter-preview.adapter.ts

@@ -0,0 +1,37 @@
+import { Injectable } from '@angular/core';
+import { Result, ok, err } from '@shared/kernel/fp';
+import { currentRole } from '@shared/infrastructure/role';
+import { problemDetail } from '@shared/infrastructure/api-error';
+import { environment } from '../../../environments/environment';
+
+const PREVIEW_FAILED = $localize`:@@brief.preview.failed:De voorvertoning kon niet worden geopend.`;
+
+/**
+ * `/brief/preview` returns `text/html`, not JSON, and is `.ExcludeFromDescription()`'d
+ * to keep the NSwag-generated client JSON-only (same seam as uploads) — so this is a
+ * hand-written fetch, not the `ApiClient`. That also means it bypasses `HttpClient`'s
+ * `roleInterceptor`, so `X-Role` is set here explicitly.
+ */
+@Injectable({ providedIn: 'root' })
+export class LetterPreviewAdapter {
+  async preview(): Promise<Result<string, Blob>> {
+    let res: Response;
+    try {
+      res = await fetch(`${environment.apiBaseUrl}/api/v1/brief/preview`, {
+        headers: { 'X-Role': currentRole() },
+      });
+    } catch {
+      return err(PREVIEW_FAILED);
+    }
+    if (!res.ok) return err(await errorMessage(res));
+    return ok(await res.blob());
+  }
+}
+
+async function errorMessage(res: Response): Promise<string> {
+  try {
+    return problemDetail(await res.json(), PREVIEW_FAILED);
+  } catch {
+    return PREVIEW_FAILED;
+  }
+}

src/app/brief/infrastructure/org-template.adapter.spec.ts

@@ -0,0 +1,54 @@
+import { describe, it, expect } from 'vitest';
+import { OrgTemplateAdminViewDto, OrgTemplateDto } from '@shared/infrastructure/api-client';
+import { parseOrgTemplateAdminView } from './org-template.adapter';
+
+const draft: OrgTemplateDto = {
+  subOrgId: 'cibg-registers',
+  orgName: 'CIBG',
+  returnAddress: 'Postbus 1',
+  footerContact: 'info@cibg.nl',
+  footerLegal: 'onderdeel van VWS',
+  signatureName: 'A. de Vries',
+  signatureRole: 'Hoofd Registratie',
+  signatureClosing: 'Met vriendelijke groet,',
+  margins: { topMm: 25, rightMm: 20, bottomMm: 25, leftMm: 20 },
+  version: 3,
+};
+
+const view: OrgTemplateAdminViewDto = {
+  draft,
+  publishedVersion: 3,
+  unsentBriefs: 2,
+  history: [{ version: 2, publishedAt: '2026-06-01', template: draft }],
+};
+
+describe('parseOrgTemplateAdminView', () => {
+  it('parses a well-formed admin view', () => {
+    const r = parseOrgTemplateAdminView(view);
+    expect(r.ok).toBe(true);
+    if (!r.ok) return;
+    expect(r.value.draft.orgName).toBe('CIBG');
+    expect(r.value.publishedVersion).toBe(3);
+    expect(r.value.unsentBriefs).toBe(2);
+    expect(r.value.history).toHaveLength(1);
+    expect(r.value.history[0].version).toBe(2);
+  });
+
+  it('rejects a missing draft', () => {
+    const r = parseOrgTemplateAdminView({ ...view, draft: undefined });
+    expect(r.ok).toBe(false);
+  });
+
+  it('rejects a missing count field', () => {
+    const r = parseOrgTemplateAdminView({ ...view, unsentBriefs: undefined });
+    expect(r.ok).toBe(false);
+  });
+
+  it('rejects a malformed history entry', () => {
+    const r = parseOrgTemplateAdminView({
+      ...view,
+      history: [{ version: 2, publishedAt: '2026-06-01', template: { ...draft, orgName: undefined } }],
+    });
+    expect(r.ok).toBe(false);
+  });
+});

src/app/brief/infrastructure/org-template.adapter.ts

@@ -0,0 +1,163 @@
+import { Injectable, inject } from '@angular/core';
+import { Result, ok, err } from '@shared/kernel/fp';
+import { runSubmit } from '@shared/application/submit';
+import { currentRole } from '@shared/infrastructure/role';
+import { problemDetail } from '@shared/infrastructure/api-error';
+import { environment } from '../../../environments/environment';
+import {
+  ApiClient,
+  OrgTemplateAdminViewDto,
+  OrgTemplateDto,
+  OrgTemplateVersionDto,
+  PublishOrgTemplateResponse,
+  SubOrgSummaryDto,
+} from '@shared/infrastructure/api-client';
+import {
+  OrgTemplate,
+  OrgTemplateAdminView,
+  OrgTemplateVersion,
+  PublishResult,
+  SubOrgSummary,
+} from '@brief/domain/org-template';
+import { parseOrgTemplate } from '@brief/infrastructure/brief.adapter';
+
+/**
+ * The only place admin org-template HTTP lives (ADR-0001 boundary). CRUD/publish/
+ * rollback go through the generated client (X-Role added by `roleInterceptor`);
+ * `parse*` narrows the untrusted wire shape. The proefbrief is `text/html` and
+ * `ExcludeFromDescription`'d — a hand-written fetch, same seam as `letter-preview.adapter`.
+ */
+
+const FAILED = $localize`:@@orgTemplate.action.failed:De actie is niet gelukt. Probeer het later opnieuw.`;
+const PROEFBRIEF_FAILED = $localize`:@@orgTemplate.proefbrief.failed:De proefbrief kon niet worden geopend.`;
+
+@Injectable({ providedIn: 'root' })
+export class OrgTemplateAdapter {
+  private client = inject(ApiClient);
+
+  async list(): Promise<Result<string, SubOrgSummary[]>> {
+    const r = await runSubmit(() => this.client.orgTemplates(), FAILED);
+    if (!r.ok) return r;
+    const out: SubOrgSummary[] = [];
+    for (const s of r.value ?? []) {
+      const parsed = parseSubOrg(s);
+      if (!parsed.ok) return parsed;
+      out.push(parsed.value);
+    }
+    return ok(out);
+  }
+
+  async load(subOrgId: string): Promise<Result<string, OrgTemplateAdminView>> {
+    const r = await runSubmit(() => this.client.orgTemplateGET(subOrgId), FAILED);
+    return r.ok ? parseAdminView(r.value) : r;
+  }
+
+  async save(subOrgId: string, draft: OrgTemplate): Promise<Result<string, OrgTemplateAdminView>> {
+    const r = await runSubmit(
+      () => this.client.orgTemplatePUT(subOrgId, { draft: toDto(draft) }),
+      FAILED,
+    );
+    return r.ok ? parseAdminView(r.value) : r;
+  }
+
+  async publish(subOrgId: string): Promise<Result<string, PublishResult>> {
+    const r = await runSubmit(() => this.client.orgTemplatePublish(subOrgId), FAILED);
+    return r.ok ? parsePublish(r.value) : r;
+  }
+
+  async rollback(
+    subOrgId: string,
+    version: number,
+  ): Promise<Result<string, OrgTemplateAdminView>> {
+    const r = await runSubmit(() => this.client.orgTemplateRollback(subOrgId, version), FAILED);
+    return r.ok ? parseAdminView(r.value) : r;
+  }
+
+  /** Proefbrief: the unpublished draft rendered over a fixture letter, opened as a Blob. */
+  async proefbrief(subOrgId: string): Promise<Result<string, Blob>> {
+    let res: Response;
+    try {
+      res = await fetch(
+        `${environment.apiBaseUrl}/api/v1/admin/org-template/${encodeURIComponent(subOrgId)}/preview`,
+        { headers: { 'X-Role': currentRole() } },
+      );
+    } catch {
+      return err(PROEFBRIEF_FAILED);
+    }
+    if (!res.ok) {
+      try {
+        return err(problemDetail(await res.json(), PROEFBRIEF_FAILED));
+      } catch {
+        return err(PROEFBRIEF_FAILED);
+      }
+    }
+    return ok(await res.blob());
+  }
+}
+
+// --- parse: wire → domain, validating at the boundary ---
+
+function parseSubOrg(dto: SubOrgSummaryDto): Result<string, SubOrgSummary> {
+  if (typeof dto.subOrgId !== 'string' || typeof dto.orgName !== 'string')
+    return err('sub-org: bad shape');
+  return ok({
+    subOrgId: dto.subOrgId,
+    orgName: dto.orgName,
+    publishedVersion: dto.publishedVersion ?? 0,
+  });
+}
+
+function parseVersion(dto: OrgTemplateVersionDto): Result<string, OrgTemplateVersion> {
+  if (typeof dto.version !== 'number' || typeof dto.publishedAt !== 'string')
+    return err('version: bad shape');
+  const template = parseOrgTemplate(dto.template);
+  if (!template.ok) return template;
+  return ok({ version: dto.version, publishedAt: dto.publishedAt, template: template.value });
+}
+
+export function parseOrgTemplateAdminView(
+  dto: OrgTemplateAdminViewDto,
+): Result<string, OrgTemplateAdminView> {
+  const draft = parseOrgTemplate(dto.draft);
+  if (!draft.ok) return draft;
+  if (typeof dto.publishedVersion !== 'number' || typeof dto.unsentBriefs !== 'number')
+    return err('admin-view: bad shape');
+  const history: OrgTemplateVersion[] = [];
+  for (const v of dto.history ?? []) {
+    const parsed = parseVersion(v);
+    if (!parsed.ok) return parsed;
+    history.push(parsed.value);
+  }
+  return ok({
+    draft: draft.value,
+    publishedVersion: dto.publishedVersion,
+    history,
+    unsentBriefs: dto.unsentBriefs,
+  });
+}
+
+const parseAdminView = parseOrgTemplateAdminView;
+
+function parsePublish(dto: PublishOrgTemplateResponse): Result<string, PublishResult> {
+  if (typeof dto.version !== 'number' || typeof dto.affectedUnsentBriefs !== 'number')
+    return err('publish: bad shape');
+  return ok({ version: dto.version, affectedUnsentBriefs: dto.affectedUnsentBriefs });
+}
+
+// --- toDto: domain → wire (for save) ---
+
+function toDto(t: OrgTemplate): OrgTemplateDto {
+  return {
+    subOrgId: t.subOrgId,
+    orgName: t.orgName,
+    returnAddress: t.returnAddress,
+    ...(t.logoDocumentId != null ? { logoDocumentId: t.logoDocumentId } : {}),
+    footerContact: t.footerContact,
+    footerLegal: t.footerLegal,
+    signatureName: t.signatureName,
+    signatureRole: t.signatureRole,
+    signatureClosing: t.signatureClosing,
+    margins: { ...t.margins },
+    version: t.version,
+  };
+}

src/app/brief/ui/brief.page.ts

@@ -50,6 +50,7 @@ import { LetterComposerComponent } from '@brief/ui/letter-composer/letter-compos
               <app-letter-composer
                 [brief]="s.brief"
                 [orgTemplate]="orgTemplate"
+                [logoUrl]="store.logoUrl()"
                 [availablePassages]="s.availablePassages"
                 [diagnostics]="store.diagnostics()"
                 [canEdit]="store.canEdit()"
@@ -63,6 +64,7 @@ import { LetterComposerComponent } from '@brief/ui/letter-composer/letter-compos
                 (approve)="store.approve()"
                 (reject)="store.reject($event)"
                 (send)="store.send()"
+                (preview)="store.previewLetter()"
               />
             }
           }

src/app/brief/ui/letter-canvas/letter-canvas.component.ts

@@ -18,6 +18,7 @@ import { formatDatumNl } from '@shared/kernel/datum';
 import { Paragraph } from '@shared/kernel/rich-text';
 import { Brief, LetterBlock, LibraryPassage } from '@brief/domain/brief';
 import { OrgTemplate } from '@brief/domain/org-template';
+import { OrgTemplateTextField } from '@brief/domain/org-template.machine';
 import { Diagnostic } from '@brief/domain/placeholders';
 import { BriefMsg } from '@brief/domain/brief.machine';
 import { LetterSectionComponent } from '@brief/ui/letter-section/letter-section.component';
@@ -70,26 +71,47 @@ const A4_HEIGHT_PX = (297 * 96) / 25.4;
       }
       /* Portal-side chrome around the letter surface (not part of the contract file). */
       .surface {
-        background: var(--rhc-color-grijs-100, #f0f0f0);
+        background: var(--rhc-color-grijs-100);
         border: var(--rhc-border-width-sm) solid var(--rhc-color-border-default);
         border-radius: var(--rhc-border-radius-md);
         padding: var(--rhc-space-max-lg);
         overflow-x: auto;
       }
       .surface .letter {
-        box-shadow: 0 1px 4px rgb(0 0 0 / 0.15);
+        box-shadow: 0 1px 4px rgb(0 0 0 / 0.15); /* token-ok: paper drop-shadow, not a palette colour */
       }
       /* Org-identity regions: visibly not the drafter's to edit. */
       .from-template {
-        background: var(--rhc-color-grijs-100, #f5f5f5);
+        background: var(--rhc-color-grijs-100);
-        outline: 2mm solid var(--rhc-color-grijs-100, #f5f5f5);
+        outline: 2mm solid var(--rhc-color-grijs-100);
       }
       .from-template-caption {
         font-size: 7.5pt;
         /* grijs-700, not foreground-subtle: subtle misses AA contrast on the tint. */
-        color: var(--rhc-color-grijs-700, #334155);
+        color: var(--rhc-color-grijs-700);
         margin: 0 0 2mm;
       }
+      /* Admin edit-in-place (editableRegions='template'): the org-identity fields
+         become controls styled to sit in the letter, with a visible editable affordance. */
+      .tmpl-input,
+      .tmpl-textarea {
+        font: inherit;
+        color: inherit;
+        width: 100%;
+        box-sizing: border-box;
+        background: var(--rhc-color-geel-100);
+        border: var(--rhc-border-width-sm) dashed var(--rhc-color-border-strong);
+        border-radius: var(--rhc-border-radius-sm);
+        padding: 0.5mm 1mm;
+      }
+      .tmpl-textarea {
+        resize: vertical;
+      }
+      .org-logo {
+        max-height: 20mm;
+        max-width: 60mm;
+        margin-block-end: 3mm;
+      }
     `,
   ],
   template: `
@@ -137,8 +159,27 @@ const A4_HEIGHT_PX = (297 * 96) / 25.4;
           @if (tintTemplate()) {
             <p class="from-template-caption">{{ fromTemplateCaption() }}</p>
           }
-          <p class="org-wordmark">{{ orgTemplate().orgName }}</p>
+          @if (logoUrl()) {
-          <address class="return-address">{{ orgTemplate().returnAddress }}</address>
+            <img class="org-logo" [src]="logoUrl()" [alt]="logoAlt()" />
+          }
+          @if (editing()) {
+            <input
+              class="tmpl-input org-wordmark"
+              [value]="orgTemplate().orgName"
+              [attr.aria-label]="orgNameLabel()"
+              (input)="emitEdit('orgName', $event)"
+            />
+            <textarea
+              class="tmpl-textarea return-address"
+              rows="2"
+              [value]="orgTemplate().returnAddress"
+              [attr.aria-label]="returnAddressLabel()"
+              (input)="emitEdit('returnAddress', $event)"
+            ></textarea>
+          } @else {
+            <p class="org-wordmark">{{ orgTemplate().orgName }}</p>
+            <address class="return-address">{{ orgTemplate().returnAddress }}</address>
+          }
           <address class="address-window">{{ recipientText() }}</address>
           <dl class="reference">
             <div>
@@ -209,14 +250,51 @@ const A4_HEIGHT_PX = (297 * 96) / 25.4;
         </div>
 
         <div class="letter__signature" [class.from-template]="tintTemplate()">
-          <p>{{ orgTemplate().signatureClosing }}</p>
+          @if (editing()) {
-          <p class="signature-name">{{ orgTemplate().signatureName }}</p>
+            <input
-          <p>{{ orgTemplate().signatureRole }}</p>
+              class="tmpl-input"
+              [value]="orgTemplate().signatureClosing"
+              [attr.aria-label]="signatureClosingLabel()"
+              (input)="emitEdit('signatureClosing', $event)"
+            />
+            <input
+              class="tmpl-input signature-name"
+              [value]="orgTemplate().signatureName"
+              [attr.aria-label]="signatureNameLabel()"
+              (input)="emitEdit('signatureName', $event)"
+            />
+            <input
+              class="tmpl-input"
+              [value]="orgTemplate().signatureRole"
+              [attr.aria-label]="signatureRoleLabel()"
+              (input)="emitEdit('signatureRole', $event)"
+            />
+          } @else {
+            <p>{{ orgTemplate().signatureClosing }}</p>
+            <p class="signature-name">{{ orgTemplate().signatureName }}</p>
+            <p>{{ orgTemplate().signatureRole }}</p>
+          }
         </div>
 
         <div class="letter__footer" [class.from-template]="tintTemplate()">
-          <div class="footer-contact">{{ orgTemplate().footerContact }}</div>
+          @if (editing()) {
-          <div class="footer-legal">{{ orgTemplate().footerLegal }}</div>
+            <textarea
+              class="tmpl-textarea footer-contact"
+              rows="2"
+              [value]="orgTemplate().footerContact"
+              [attr.aria-label]="footerContactLabel()"
+              (input)="emitEdit('footerContact', $event)"
+            ></textarea>
+            <input
+              class="tmpl-input footer-legal"
+              [value]="orgTemplate().footerLegal"
+              [attr.aria-label]="footerLegalLabel()"
+              (input)="emitEdit('footerLegal', $event)"
+            />
+          } @else {
+            <div class="footer-contact">{{ orgTemplate().footerContact }}</div>
+            <div class="footer-legal">{{ orgTemplate().footerLegal }}</div>
+          }
         </div>
 
         @for (top of pageBreaks(); track $index) {
@@ -238,7 +316,11 @@ export class LetterCanvasComponent {
   placeholders = input<readonly PlaceholderOption[]>([]);
   diagnostics = input<readonly Diagnostic[]>([]);
   zoom = input(1);
+  /** The org logo's content URL (letterhead), or null when none is set. */
+  logoUrl = input<string | null>(null);
   edit = output<BriefMsg>();
+  /** An in-place edit to an org-identity field (only in `editableRegions='template'`). */
+  templateEdit = output<{ field: OrgTemplateTextField; value: string }>();
 
   showSampleLabel = input($localize`:@@brief.preview.showSample:Voorbeeld met testwaarden`);
   hideSampleLabel = input($localize`:@@brief.preview.hideSample:Testwaarden verbergen`);
@@ -253,6 +335,14 @@ export class LetterCanvasComponent {
   );
   referenceLabel = input($localize`:@@brief.canvas.reference:Ons kenmerk`);
   dateLabel = input($localize`:@@brief.canvas.date:Datum`);
+  logoAlt = input($localize`:@@brief.canvas.logoAlt:Logo van de organisatie`);
+  orgNameLabel = input($localize`:@@brief.canvas.orgName:Organisatienaam`);
+  returnAddressLabel = input($localize`:@@brief.canvas.returnAddress:Retouradres`);
+  signatureClosingLabel = input($localize`:@@brief.canvas.signatureClosing:Afsluiting`);
+  signatureNameLabel = input($localize`:@@brief.canvas.signatureName:Naam ondertekenaar`);
+  signatureRoleLabel = input($localize`:@@brief.canvas.signatureRole:Functie ondertekenaar`);
+  footerContactLabel = input($localize`:@@brief.canvas.footerContact:Contactgegevens (voettekst)`);
+  footerLegalLabel = input($localize`:@@brief.canvas.footerLegal:Juridische voettekst`);
 
   protected showSample = signal(false);
   protected letterDate = formatDatumNl(new Date());
@@ -260,6 +350,12 @@ export class LetterCanvasComponent {
   /** The letterhead/signature/footer are tinted "not yours" only while composing —
       in 'none' the whole surface is read-only, in 'template' they ARE the editable focus. */
   protected tintTemplate = computed(() => this.editableRegions() === 'content');
+  /** Admin edit-in-place: the org-identity regions render as controls. */
+  protected editing = computed(() => this.editableRegions() === 'template');
+
+  protected emitEdit(field: OrgTemplateTextField, event: Event) {
+    this.templateEdit.emit({ field, value: (event.target as HTMLInputElement | HTMLTextAreaElement).value });
+  }
 
   protected marginStyle = computed(() => {
     const m = this.orgTemplate().margins;

src/app/brief/ui/letter-composer/letter-composer.component.ts

@@ -41,6 +41,11 @@ import { RejectionCommentsComponent } from '@brief/ui/rejection-comments/rejecti
         flex-wrap: wrap;
         margin-block-end: var(--rhc-space-max-lg);
       }
+      .head-end {
+        display: flex;
+        align-items: center;
+        gap: var(--rhc-space-max-md);
+      }
       .panel {
         margin-block: var(--rhc-space-max-xl);
       }
@@ -56,7 +61,12 @@ import { RejectionCommentsComponent } from '@brief/ui/rejection-comments/rejecti
   template: `
     <div class="head">
       <app-heading [level]="2">{{ title() }}</app-heading>
-      <app-status-badge [label]="statusLabel()" [color]="statusColor()" />
+      <div class="head-end">
+        <app-button variant="subtle" [disabled]="busy()" (click)="preview.emit()">{{
+          previewLabel()
+        }}</app-button>
+        <app-status-badge [label]="statusLabel()" [color]="statusColor()" />
+      </div>
     </div>
 
     @if (status() === 'rejected') {
@@ -66,6 +76,7 @@ import { RejectionCommentsComponent } from '@brief/ui/rejection-comments/rejecti
     <app-letter-canvas
       [brief]="brief()"
       [orgTemplate]="orgTemplate()"
+      [logoUrl]="logoUrl()"
       [editableRegions]="canEdit() ? 'content' : 'none'"
       [availablePassages]="availablePassages()"
       [placeholders]="menu()"
@@ -129,6 +140,7 @@ import { RejectionCommentsComponent } from '@brief/ui/rejection-comments/rejecti
 export class LetterComposerComponent {
   brief = input.required<Brief>();
   orgTemplate = input.required<OrgTemplate>();
+  logoUrl = input<string | null>(null);
   availablePassages = input<readonly LibraryPassage[]>([]);
   diagnostics = input<readonly Diagnostic[]>([]);
   canEdit = input(false);
@@ -143,9 +155,11 @@ export class LetterComposerComponent {
   approve = output<void>();
   reject = output<string>();
   send = output<void>();
+  preview = output<void>();
   locate = output<Diagnostic>();
 
   title = input($localize`:@@brief.title:Brief aan de zorgverlener`);
+  previewLabel = input($localize`:@@brief.preview.open:Voorbeeld`);
   submitLabel = input($localize`:@@brief.submit:Indienen ter beoordeling`);
   resubmitLabel = input($localize`:@@brief.resubmit:Opnieuw indienen`);
   submitHint = input(

src/app/brief/ui/org-template-editor/org-template-editor.component.ts

@@ -0,0 +1,348 @@
+import { Component, computed, input, output } from '@angular/core';
+import { DatePipe } from '@angular/common';
+import { HeadingComponent } from '@shared/ui/heading/heading.component';
+import { ButtonComponent } from '@shared/ui/button/button.component';
+import { AlertComponent } from '@shared/ui/alert/alert.component';
+import { FileInputComponent } from '@shared/ui/upload/file-input/file-input.component';
+import { SingleUploadComponent } from '@shared/ui/upload/single-upload/single-upload.component';
+import { UploadState } from '@shared/upload/upload.machine';
+import { Brief } from '@brief/domain/brief';
+import {
+  MARGIN_MAX_MM,
+  MARGIN_MIN_MM,
+  Margins,
+  OrgTemplate,
+  OrgTemplateVersion,
+  SubOrgSummary,
+} from '@brief/domain/org-template';
+import { OrgTemplateTextField } from '@brief/domain/org-template.machine';
+import { LetterCanvasComponent } from '@brief/ui/letter-canvas/letter-canvas.component';
+
+const LOGO_CATEGORY = 'org-logo';
+const EDGES: readonly (keyof Margins)[] = ['topMm', 'rightMm', 'bottomMm', 'leftMm'];
+
+/** A minimal read-only sample letter, so the admin sees the org identity in context
+    while editing (content itself is not the admin's to change). */
+export const SAMPLE_LETTER_BRIEF: Brief = {
+  briefId: 'VOORBEELD-0001',
+  beroep: 'arts',
+  templateId: 'sample',
+  drafterId: 'sample',
+  status: { tag: 'draft' },
+  placeholders: [
+    { key: 'naam_zorgverlener', label: 'Naam zorgverlener', autoResolvable: true },
+    { key: 'datum', label: 'Datum', autoResolvable: true },
+  ],
+  sections: [
+    {
+      sectionKey: 'body',
+      title: 'Voorbeeldinhoud',
+      required: true,
+      locked: true,
+      blocks: [
+        {
+          type: 'freeText',
+          blockId: 'sample-1',
+          content: {
+            paragraphs: [
+              {
+                nodes: [
+                  { type: 'text', text: 'Geachte ' },
+                  { type: 'placeholder', key: 'naam_zorgverlener' },
+                  { type: 'text', text: ',' },
+                ],
+              },
+              {
+                nodes: [
+                  {
+                    type: 'text',
+                    text: 'Dit is voorbeeldinhoud. Alleen de huisstijl-onderdelen (logo, afzender, ondertekening en voettekst) zijn hier bewerkbaar.',
+                  },
+                ],
+              },
+            ],
+          },
+        },
+      ],
+    },
+  ],
+};
+
+/**
+ * Organism (WP-26): the admin org-template editor. The mirror of the drafter's
+ * composer — the letter canvas runs in `editableRegions='template'` so the
+ * letterhead/signature/footer are edited in place, while the content is a read-only
+ * sample. Margins, logo upload, version history and the publish bar sit around it.
+ * Presentational: every mutation is an output the store turns into a command.
+ */
+@Component({
+  selector: 'app-org-template-editor',
+  imports: [
+    DatePipe,
+    HeadingComponent,
+    ButtonComponent,
+    AlertComponent,
+    FileInputComponent,
+    SingleUploadComponent,
+    LetterCanvasComponent,
+  ],
+  styles: [
+    `
+      :host {
+        display: block;
+      }
+      .toolbar {
+        display: flex;
+        justify-content: space-between;
+        align-items: end;
+        gap: var(--rhc-space-max-md);
+        flex-wrap: wrap;
+        margin-block-end: var(--rhc-space-max-lg);
+      }
+      .field {
+        display: flex;
+        flex-direction: column;
+        gap: var(--rhc-space-max-2xs);
+      }
+      .save {
+        color: var(--rhc-color-foreground-subtle);
+        font-size: 0.9em;
+      }
+      .section {
+        margin-block-start: var(--rhc-space-max-xl);
+      }
+      .margins {
+        display: flex;
+        gap: var(--rhc-space-max-md);
+        flex-wrap: wrap;
+        border: var(--rhc-border-width-sm) solid var(--rhc-color-border-default);
+        border-radius: var(--rhc-border-radius-md);
+        padding: var(--rhc-space-max-md);
+      }
+      .margins input {
+        width: 6rem;
+      }
+      .history-list {
+        list-style: none;
+        margin: 0;
+        padding: 0;
+        display: flex;
+        flex-direction: column;
+        gap: var(--rhc-space-max-sm);
+      }
+      .history-row {
+        display: flex;
+        align-items: center;
+        justify-content: space-between;
+        gap: var(--rhc-space-max-md);
+        border-block-end: var(--rhc-border-width-sm) solid var(--rhc-color-border-default);
+        padding-block-end: var(--rhc-space-max-sm);
+      }
+      .bar {
+        display: flex;
+        flex-wrap: wrap;
+        gap: var(--rhc-space-max-md);
+        align-items: center;
+        margin-block-start: var(--rhc-space-max-xl);
+      }
+      .published {
+        color: var(--rhc-color-foreground-subtle);
+      }
+    `,
+  ],
+  template: `
+    <div class="toolbar">
+      <label class="field">
+        <span>{{ subOrgLabel() }}</span>
+        <select class="form-select" (change)="onSelectSubOrg($event)">
+          @for (o of subOrgs(); track o.subOrgId) {
+            <option [value]="o.subOrgId" [selected]="o.subOrgId === selectedSubOrgId()">
+              {{ o.orgName }}
+            </option>
+          }
+        </select>
+      </label>
+      <span class="save" role="status" aria-live="polite">{{ saveText() }}</span>
+    </div>
+
+    <app-letter-canvas
+      [brief]="sampleBrief()"
+      [orgTemplate]="draft()"
+      [logoUrl]="logoUrl()"
+      editableRegions="template"
+      (templateEdit)="templateEdit.emit($event)"
+    />
+
+    <fieldset class="section margins">
+      <legend>{{ marginsLegend() }}</legend>
+      @for (edge of edges; track edge) {
+        <label class="field">
+          <span>{{ edgeLabel(edge) }}</span>
+          <input
+            class="form-control"
+            type="number"
+            [min]="MIN"
+            [max]="MAX"
+            [value]="draft().margins[edge]"
+            (input)="onMargin(edge, $event)"
+          />
+        </label>
+      }
+    </fieldset>
+
+    <section class="section">
+      <app-heading [level]="3">{{ logoHeading() }}</app-heading>
+      @if (logoCategory()) {
+        <app-file-input
+          inputId="org-logo-input"
+          [accept]="logoCategory()!.acceptedTypes"
+          [maxSizeMb]="logoCategory()!.maxSizeMb"
+          [label]="logoHeading()"
+          (filesSelected)="logoSelected.emit($event)"
+        />
+      }
+      @if (logoRejection()) {
+        <app-alert type="error">{{ logoRejection() }}</app-alert>
+      }
+      @if (logoUploads().length) {
+        <ul class="file-list">
+          @for (u of logoUploads(); track u.localId) {
+            <li
+              app-single-upload
+              [upload]="u"
+              [previewUrlFor]="previewUrlFor()"
+              (remove)="logoRemoved.emit(u.localId)"
+              (retry)="logoRetry.emit(u.localId)"
+            ></li>
+          }
+        </ul>
+      }
+    </section>
+
+    <section class="section">
+      <app-heading [level]="3">{{ historyHeading() }}</app-heading>
+      @if (history().length === 0) {
+        <p class="published">{{ noHistory() }}</p>
+      } @else {
+        <ul class="history-list">
+          @for (v of history(); track v.version) {
+            <li class="history-row">
+              <span>{{ versionLabel() }} {{ v.version }} · {{ v.publishedAt | date: 'longDate' }}</span>
+              <app-button variant="subtle" [disabled]="busy()" (click)="rollback.emit(v.version)">
+                {{ rollbackLabel() }}
+              </app-button>
+            </li>
+          }
+        </ul>
+      }
+    </section>
+
+    <div class="bar">
+      <span class="published">{{ publishedLabel() }} {{ publishedVersion() }}</span>
+      @if (pendingPublish()) {
+        <app-alert type="warning">{{ impactText() }}</app-alert>
+        <app-button variant="primary" [disabled]="busy()" (click)="confirmPublish.emit()">
+          {{ confirmLabel() }}
+        </app-button>
+        <app-button variant="subtle" [disabled]="busy()" (click)="cancelPublish.emit()">
+          {{ cancelLabel() }}
+        </app-button>
+      } @else {
+        <app-button
+          variant="primary"
+          [disabled]="!draftValid() || busy()"
+          (click)="requestPublish.emit()"
+        >
+          {{ publishLabel() }}
+        </app-button>
+        @if (!draftValid()) {
+          <span class="published">{{ invalidHint() }}</span>
+        }
+      }
+      <app-button variant="secondary" [disabled]="busy()" (click)="proefbrief.emit()">
+        {{ proefbriefLabel() }}
+      </app-button>
+    </div>
+  `,
+})
+export class OrgTemplateEditorComponent {
+  draft = input.required<OrgTemplate>();
+  logoUrl = input<string | null>(null);
+  uploadState = input.required<UploadState>();
+  subOrgs = input<readonly SubOrgSummary[]>([]);
+  selectedSubOrgId = input<string | null>(null);
+  history = input<readonly OrgTemplateVersion[]>([]);
+  publishedVersion = input(0);
+  unsentBriefs = input(0);
+  draftValid = input(false);
+  busy = input(false);
+  pendingPublish = input(false);
+  saveText = input('');
+  sampleBrief = input<Brief>(SAMPLE_LETTER_BRIEF);
+  previewUrlFor = input<(documentId: string) => string | undefined>();
+
+  selectSubOrg = output<string>();
+  templateEdit = output<{ field: OrgTemplateTextField; value: string }>();
+  marginEdit = output<{ edge: keyof Margins; value: number }>();
+  logoSelected = output<File[]>();
+  logoRemoved = output<string>();
+  logoRetry = output<string>();
+  requestPublish = output<void>();
+  confirmPublish = output<void>();
+  cancelPublish = output<void>();
+  rollback = output<number>();
+  proefbrief = output<void>();
+
+  protected readonly edges = EDGES;
+  protected readonly MIN = MARGIN_MIN_MM;
+  protected readonly MAX = MARGIN_MAX_MM;
+
+  protected logoCategory = computed(() =>
+    this.uploadState().categories.find((c) => c.categoryId === LOGO_CATEGORY),
+  );
+  protected logoUploads = computed(() =>
+    this.uploadState().uploads.filter((u) => u.categoryId === LOGO_CATEGORY),
+  );
+  protected logoRejection = computed(() => this.uploadState().rejections[LOGO_CATEGORY]);
+
+  protected onSelectSubOrg(event: Event) {
+    this.selectSubOrg.emit((event.target as HTMLSelectElement).value);
+  }
+  protected onMargin(edge: keyof Margins, event: Event) {
+    const value = (event.target as HTMLInputElement).valueAsNumber;
+    if (Number.isFinite(value)) this.marginEdit.emit({ edge, value });
+  }
+
+  protected edgeLabel(edge: keyof Margins): string {
+    switch (edge) {
+      case 'topMm':
+        return $localize`:@@orgTemplate.margin.top:Boven (mm)`;
+      case 'rightMm':
+        return $localize`:@@orgTemplate.margin.right:Rechts (mm)`;
+      case 'bottomMm':
+        return $localize`:@@orgTemplate.margin.bottom:Onder (mm)`;
+      case 'leftMm':
+        return $localize`:@@orgTemplate.margin.left:Links (mm)`;
+    }
+  }
+
+  protected impactText = computed(() =>
+    $localize`:@@orgTemplate.publish.impact:Dit raakt ${this.unsentBriefs()}:count: nog niet verzonden brieven. Publiceren?`,
+  );
+
+  protected subOrgLabel = input($localize`:@@orgTemplate.subOrg:Organisatieonderdeel`);
+  protected marginsLegend = input($localize`:@@orgTemplate.margins:Marges (mm, tussen ${MARGIN_MIN_MM}:min: en ${MARGIN_MAX_MM}:max:)`);
+  protected logoHeading = input($localize`:@@orgTemplate.logo:Logo`);
+  protected historyHeading = input($localize`:@@orgTemplate.history:Versiegeschiedenis`);
+  protected noHistory = input($localize`:@@orgTemplate.history.none:Nog niets gepubliceerd.`);
+  protected versionLabel = input($localize`:@@orgTemplate.version:Versie`);
+  protected rollbackLabel = input($localize`:@@orgTemplate.rollback:Terugzetten in concept`);
+  protected publishedLabel = input($localize`:@@orgTemplate.published:Gepubliceerde versie:`);
+  protected publishLabel = input($localize`:@@orgTemplate.publish:Publiceren`);
+  protected confirmLabel = input($localize`:@@orgTemplate.publish.confirm:Bevestigen`);
+  protected cancelLabel = input($localize`:@@orgTemplate.publish.cancel:Annuleren`);
+  protected proefbriefLabel = input($localize`:@@orgTemplate.proefbrief:Proefbrief`);
+  protected invalidHint = input(
+    $localize`:@@orgTemplate.invalid:Vul organisatienaam en ondertekenaar in; marges tussen ${MARGIN_MIN_MM}:min: en ${MARGIN_MAX_MM}:max: mm.`,
+  );
+}

src/app/brief/ui/org-template-editor/org-template-editor.stories.ts

@@ -0,0 +1,81 @@
+import type { Meta, StoryObj } from '@storybook/angular';
+import { OrgTemplateEditorComponent } from './org-template-editor.component';
+import { OrgTemplate, OrgTemplateVersion, SubOrgSummary } from '@brief/domain/org-template';
+import { UploadState, initialUpload } from '@shared/upload/upload.machine';
+
+const draft: OrgTemplate = {
+  subOrgId: 'cibg-registers',
+  orgName: 'CIBG — Registers',
+  returnAddress: 'BIG-register\nPostbus 00000\n2500 AA Den Haag',
+  footerContact: 'www.bigregister.nl\ninfo@voorbeeld.example',
+  footerLegal: 'Ons kenmerk vermelden bij correspondentie.',
+  signatureName: 'A. de Vries',
+  signatureRole: 'Hoofd Registratie',
+  signatureClosing: 'Met vriendelijke groet,',
+  margins: { topMm: 25, rightMm: 25, bottomMm: 25, leftMm: 25 },
+  version: 3,
+};
+
+const subOrgs: SubOrgSummary[] = [
+  { subOrgId: 'cibg-registers', orgName: 'CIBG — Registers', publishedVersion: 3 },
+  { subOrgId: 'cibg-vakbekwaamheid', orgName: 'CIBG — Vakbekwaamheid', publishedVersion: 1 },
+];
+
+const history: OrgTemplateVersion[] = [
+  { version: 3, publishedAt: '2026-06-20', template: draft },
+  { version: 2, publishedAt: '2026-05-11', template: draft },
+];
+
+const uploadWithCategory: UploadState = {
+  ...initialUpload,
+  categories: [
+    {
+      categoryId: 'org-logo',
+      label: 'Logo',
+      description: 'Logo van de organisatie',
+      required: false,
+      acceptedTypes: ['image/png', 'image/jpeg'],
+      maxSizeMb: 2,
+      multiple: false,
+      allowPostDelivery: false,
+    },
+  ],
+};
+
+const meta: Meta<OrgTemplateEditorComponent> = {
+  title: 'Domein/Brief/Org Template Editor',
+  component: OrgTemplateEditorComponent,
+  args: {
+    draft,
+    logoUrl: null,
+    uploadState: uploadWithCategory,
+    subOrgs,
+    selectedSubOrgId: 'cibg-registers',
+    history,
+    publishedVersion: 3,
+    unsentBriefs: 4,
+    draftValid: true,
+    busy: false,
+    pendingPublish: false,
+    saveText: '',
+  },
+};
+export default meta;
+type Story = StoryObj<OrgTemplateEditorComponent>;
+
+export const Editing: Story = {};
+
+export const PublishConfirm: Story = {
+  args: { pendingPublish: true },
+};
+
+export const Invalid: Story = {
+  args: {
+    draft: { ...draft, orgName: '', margins: { ...draft.margins, topMm: 5 } },
+    draftValid: false,
+  },
+};
+
+export const NoHistory: Story = {
+  args: { history: [], publishedVersion: 0 },
+};

src/app/brief/ui/org-template.page.ts

@@ -0,0 +1,128 @@
+import { Component, computed, effect, inject } from '@angular/core';
+import { PageShellComponent } from '@shared/layout/page-shell/page-shell.component';
+import { AlertComponent } from '@shared/ui/alert/alert.component';
+import { ButtonComponent } from '@shared/ui/button/button.component';
+import { ASYNC } from '@shared/ui/async/async.component';
+import { AccessStore } from '@shared/application/access.store';
+import { UploadAdapter } from '@shared/upload/upload.adapter';
+import { OrgTemplateStore } from '@brief/application/org-template.store';
+import { OrgTemplateEditorComponent } from '@brief/ui/org-template-editor/org-template-editor.component';
+
+/** Page: thin container for the admin org-template editor (WP-26). Deny-by-default
+    capability gate (`orgtemplate:edit`) — a denial alert for non-admins, the editor
+    for admins. Loads once the capability resolves; wires store commands to the organism. */
+@Component({
+  selector: 'app-org-template-page',
+  imports: [
+    PageShellComponent,
+    AlertComponent,
+    ButtonComponent,
+    ...ASYNC,
+    OrgTemplateEditorComponent,
+  ],
+  styles: [
+    `
+      .save {
+        color: var(--rhc-color-foreground-subtle);
+        font-size: 0.9em;
+      }
+    `,
+  ],
+  template: `
+    <app-page-shell [heading]="heading" [intro]="intro" backLink="/brief">
+      @if (store.lastError(); as err) {
+        <app-alert type="error">{{ err }}</app-alert>
+      }
+
+      @if (!access.ready()) {
+        <!-- wait for /me before deciding — avoids flashing the denial to an admin -->
+      } @else if (!canEdit()) {
+        <app-alert type="error">{{ deniedText }}</app-alert>
+      } @else {
+        <app-async [data]="store.remoteData()">
+          <ng-template appAsyncError>
+            <app-alert type="error">{{ failedText }}</app-alert>
+            <app-button variant="secondary" (click)="reload()">{{ retryText }}</app-button>
+          </ng-template>
+          <ng-template appAsyncLoaded>
+            @if (store.draft(); as draft) {
+              <app-org-template-editor
+                [draft]="draft"
+                [logoUrl]="store.logoUrl()"
+                [uploadState]="store.uploadState()"
+                [subOrgs]="store.subOrgs()"
+                [selectedSubOrgId]="store.selectedSubOrgId()"
+                [history]="store.history()"
+                [publishedVersion]="store.publishedVersion()"
+                [unsentBriefs]="store.unsentBriefs()"
+                [draftValid]="store.draftValid()"
+                [busy]="store.busy()"
+                [pendingPublish]="store.pendingPublish()"
+                [saveText]="saveText()"
+                [previewUrlFor]="previewUrlFor"
+                (selectSubOrg)="store.selectSubOrg($event)"
+                (templateEdit)="store.edit({ tag: 'FieldEdited', field: $event.field, value: $event.value })"
+                (marginEdit)="store.edit({ tag: 'MarginEdited', edge: $event.edge, value: $event.value })"
+                (logoSelected)="store.onLogoSelected($event)"
+                (logoRemoved)="store.onLogoRemoved($event)"
+                (logoRetry)="store.onLogoRetry($event)"
+                (requestPublish)="store.requestPublish()"
+                (confirmPublish)="store.confirmPublish()"
+                (cancelPublish)="store.cancelPublish()"
+                (rollback)="store.rollback($event)"
+                (proefbrief)="store.proefbrief()"
+              />
+            }
+          </ng-template>
+        </app-async>
+      }
+    </app-page-shell>
+  `,
+})
+export class OrgTemplatePage {
+  protected store = inject(OrgTemplateStore);
+  protected access = inject(AccessStore);
+  private uploadAdapter = inject(UploadAdapter);
+
+  protected canEdit = computed(() => this.access.can('orgtemplate:edit'));
+  protected previewUrlFor = (documentId: string) => this.uploadAdapter.contentUrl(documentId);
+
+  protected heading = $localize`:@@orgTemplate.page.heading:Huisstijl beheren`;
+  protected intro = $localize`:@@orgTemplate.page.intro:Beheer per organisatieonderdeel het uiterlijk van de brief: logo, afzender, ondertekening, voettekst en marges.`;
+  protected deniedText = $localize`:@@orgTemplate.page.denied:U hebt geen rechten om organisatiesjablonen te beheren.`;
+  protected failedText = $localize`:@@orgTemplate.page.failed:Het sjabloon kon niet worden geladen.`;
+  protected retryText = $localize`:@@orgTemplate.page.retry:Opnieuw proberen`;
+
+  private savingText = $localize`:@@orgTemplate.page.saving:Concept opslaan…`;
+  private savedText = $localize`:@@orgTemplate.page.saved:Concept opgeslagen`;
+  private saveErrorText = $localize`:@@orgTemplate.page.saveError:Opslaan mislukt`;
+  protected saveText = computed(() => {
+    switch (this.store.saveState().tag) {
+      case 'Saving':
+        return this.savingText;
+      case 'Saved':
+        return this.savedText;
+      case 'Error':
+        return this.saveErrorText;
+      default:
+        return '';
+    }
+  });
+
+  private loadRequested = false;
+  constructor() {
+    // Load once the capability resolves to `allowed` (a 403 GET would be wasted
+    // otherwise). Depends only on `canEdit()` + a plain flag — never on the store
+    // model, so dispatching `Loading` inside `load()` can't retrigger this effect.
+    effect(() => {
+      if (this.canEdit() && !this.loadRequested) {
+        this.loadRequested = true;
+        void this.store.load();
+      }
+    });
+  }
+
+  protected reload() {
+    void this.store.load();
+  }
+}

src/app/brief/ui/passage-picker/passage-picker.component.ts

@@ -14,7 +14,7 @@ import { LibraryPassage } from '@brief/domain/brief';
     `
       :host {
         display: block;
-        background: var(--rhc-color-wit, #fff);
+        background: var(--rhc-color-wit);
         border: var(--rhc-border-width-sm) solid var(--rhc-color-border-default);
         border-radius: var(--rhc-border-radius-md);
         padding: var(--rhc-space-max-md);

src/app/shared/application/access.store.ts

@@ -33,4 +33,11 @@ export class AccessStore {
     const rd = this.capabilities();
     return rd.tag === 'Success' && rd.value.includes(capability);
   }
+
+  /** True once `/me` has resolved (success or failure) — lets a page-level gate tell
+      "still loading" apart from "denied", so an admin doesn't flash the denial alert. */
+  readonly ready = computed(() => {
+    const tag = this.capabilities().tag;
+    return tag === 'Success' || tag === 'Failure';
+  });
 }

src/app/shared/upload/upload.adapter.ts

@@ -38,6 +38,12 @@ export interface XhrUploadHandle {
 /** Sentinel rejection so the caller can tell a user-cancel from a real failure. */
 export const UPLOAD_ABORTED = Symbol('upload-aborted');
 
+/** Direct URL to a stored document's bytes. Pure (no injection) so a store can build
+    a letterhead-logo `src` without pulling `ApiClient` into its dependency graph. */
+export function uploadContentUrl(documentId: string): string {
+  return `${environment.apiBaseUrl}/api/v1/uploads/${documentId}/content`;
+}
+
 /**
  * Infrastructure: the only place upload HTTP lives. Reads (categories, status,
  * delete) go through the NSwag client; the multipart POST is hand-written XHR
@@ -94,7 +100,7 @@ export class UploadAdapter {
    * browser opens it. demo-* ids (dev simulation) have no bytes and 404 here.
    */
   contentUrl(documentId: string): string {
-    return `${environment.apiBaseUrl}/api/v1/uploads/${documentId}/content`;
+    return uploadContentUrl(documentId);
   }
 
   /**