diff --git a/src/FluentCMS.Admin/Components/Forms/FactFields.razor b/src/FluentCMS.Admin/Components/Forms/FactFields.razor
new file mode 100644
index 000000000..81ff72ec2
--- /dev/null
+++ b/src/FluentCMS.Admin/Components/Forms/FactFields.razor
@@ -0,0 +1,75 @@
+@using FluentCMS.Admin.Forms
+@using FluentCMS.Core.Schema
+@inject IStringLocalizer<FactFields> L
+
+@* The fact around an entity field's value (SCH-03): its source, owner and validity, each posted under the field's name. *@
+<fieldset class="grid gap-4 rounded-md border p-4 sm:col-span-2" data-fact="@Field">
+    <legend class="px-1 text-sm font-medium">@L["Fact details for {0}", Field]</legend>
+    @if (Unsourced)
+    {
+        <p class="text-sm text-destructive" data-testid="fact-unsourced">@L["This fact has no source, so it is flagged unsourced. Say where the value comes from."]</p>
+    }
+    <div class="grid gap-4 sm:grid-cols-[12rem_1fr]">
+        <FormField Label="@L["Source kind"]" Error="@Error(FactValues.Kind)">
+            <Select name="@Name(FactValues.Kind)">
+                <option value="">@L["None"]</option>
+                @foreach (var kind in FactMetadata.SourceKinds)
+                {
+                    <option value="@kind" selected="@(Value(FactValues.Kind) == kind)">@KindLabel(kind)</option>
+                }
+            </Select>
+        </FormField>
+        <FormField Label="@L["Source"]" Description="@L["The URL, file, person or system the value comes from."]" Error="@Error(FactValues.Reference)">
+            <Input name="@Name(FactValues.Reference)" value="@Value(FactValues.Reference)" dir="ltr" />
+        </FormField>
+    </div>
+    <div class="grid gap-4 sm:grid-cols-2 lg:grid-cols-4">
+        <FormField Label="@L["Owner"]" Error="@Error(FactValues.Owner)">
+            <Select name="@Name(FactValues.Owner)">
+                <option value="">@L["None"]</option>
+                @foreach (var owner in Owners)
+                {
+                    <option value="@owner.Value" selected="@(Value(FactValues.Owner) == owner.Value)">@owner.Label</option>
+                }
+            </Select>
+        </FormField>
+        <FormField Label="@L["Valid from (UTC)"]" Error="@Error(FactMetadata.ValidFrom)">
+            <Input Type="datetime-local" name="@Name(FactMetadata.ValidFrom)" value="@Value(FactMetadata.ValidFrom)" dir="ltr" />
+        </FormField>
+        <FormField Label="@L["Valid until (UTC)"]" Error="@Error(FactMetadata.ValidUntil)">
+            <Input Type="datetime-local" name="@Name(FactMetadata.ValidUntil)" value="@Value(FactMetadata.ValidUntil)" dir="ltr" />
+        </FormField>
+        <FormField Label="@L["Last verified (UTC)"]" Error="@Error(FactMetadata.LastVerified)">
+            <Input Type="datetime-local" name="@Name(FactMetadata.LastVerified)" value="@Value(FactMetadata.LastVerified)" dir="ltr" />
+        </FormField>
+    </div>
+</fieldset>
+
+@code {
+    [Parameter, EditorRequired] public string Field { get; set; } = string.Empty;
+    [Parameter] public IReadOnlyDictionary<string, string?> Values { get; set; } = new Dictionary<string, string?>();
+    [Parameter] public IReadOnlyDictionary<string, string> Problems { get; set; } = new Dictionary<string, string>();
+    [Parameter] public IReadOnlyList<FieldOption> Owners { get; set; } = [];
+    [Parameter] public bool Unsourced { get; set; }
+
+    private string Name(string part) => $"Form.Facts[{FactValues.Key(Field, part)}]";
+
+    private string? Value(string part) => Values.GetValueOrDefault(FactValues.Key(Field, part));
+
+    private string? Error(string part) => Problems.GetValueOrDefault(part) switch
+    {
+        null => null,
+        "kind" => L["Choose a kind of source."].Value,
+        "source" => L["Give both the kind of source and the source, or neither."].Value,
+        "owner" => L["Choose an owner from the list."].Value,
+        _ => L["Enter a date and a time."].Value,
+    };
+
+    private string KindLabel(string kind) => kind switch
+    {
+        "url" => L["URL"],
+        "file" => L["File"],
+        "person" => L["Person"],
+        _ => L["System"],
+    };
+}
diff --git a/src/FluentCMS.Admin/Components/Pages/EntriesView.razor b/src/FluentCMS.Admin/Components/Pages/EntriesView.razor
index 7eb4a9864..1c28e823c 100644
--- a/src/FluentCMS.Admin/Components/Pages/EntriesView.razor
+++ b/src/FluentCMS.Admin/Components/Pages/EntriesView.razor
@@ -20,15 +20,8 @@
                 @(type.Definition.IsEntity ? L["An entity type: each field is a fact with its source, owner and validity."] : L["Entries of this content type."])
             </p>
         </div>
-        @if (!type.Definition.IsEntity)
-        {
-            <a href="@($"content/{type.Slug}/new")" aria-keyshortcuts="N" class="@ButtonVariants.Classes()" data-testid="new-entry">@L["New entry"]</a>
-        }
+        <a href="@($"content/{type.Slug}/new")" aria-keyshortcuts="N" class="@ButtonVariants.Classes()" data-testid="new-entry">@L["New entry"]</a>
     </div>
-    @if (type.Definition.IsEntity)
-    {
-        <p class="mt-4 rounded-md border px-3 py-2 text-sm text-muted-foreground" data-testid="entity-form-note">@L["Entity forms, with a source, owner and validity on every fact, come with the next forms slice. Agents write entities with set_entity_fact until then."]</p>
-    }
 
     @if (_entries.Count == 0)
     {
@@ -51,14 +44,7 @@
                     {
                         <TableRow data-entry="@entry.Id.ToString("N")">
                             <TableCell>
-                                @if (type.Definition.IsEntity)
-                                {
-                                    <bdi dir="ltr" class="font-mono text-xs">@entry.Id</bdi>
-                                }
-                                else
-                                {
-                                    <a href="@($"content/{type.Slug}/{entry.Id}")" data-ui="rove-item" tabindex="@(index == 0 ? null : "-1")" class="font-mono text-xs underline-offset-4 hover:underline" dir="ltr">@entry.Id</a>
-                                }
+                                <a href="@($"content/{type.Slug}/{entry.Id}")" data-ui="rove-item" tabindex="@(index == 0 ? null : "-1")" class="font-mono text-xs underline-offset-4 hover:underline" dir="ltr">@entry.Id</a>
                             </TableCell>
                             <TableCell><Badge Variant="outline">@StateLabel(entry.State)</Badge></TableCell>
                             <TableCell>@entry.LatestVersion</TableCell>
diff --git a/src/FluentCMS.Admin/Components/Pages/EntryEditor.razor b/src/FluentCMS.Admin/Components/Pages/EntryEditor.razor
index bd3934527..80c089855 100644
--- a/src/FluentCMS.Admin/Components/Pages/EntryEditor.razor
+++ b/src/FluentCMS.Admin/Components/Pages/EntryEditor.razor
@@ -13,6 +13,7 @@
 @inject IEntryDirectory Entries
 @inject IEntryEdits Edits
 @inject IMediaLibrary Media
+@inject FluentCMS.Core.Identity.IUserDirectory Users
 @inject FieldTypeRegistry FieldTypes
 @inject NavigationManager Navigation
 @inject IStringLocalizer<EntryEditor> L
@@ -31,47 +32,48 @@
 
     @if (type.Definition.IsEntity)
     {
-        <p class="mt-6 rounded-md border px-3 py-2 text-sm text-muted-foreground" data-testid="entity-form-note">@L["Entity forms, with a source, owner and validity on every fact, come with the next forms slice."]</p>
+        <p class="mt-2 text-sm text-muted-foreground">@L["An entity type: every field is a fact with its source, owner and validity."]</p>
     }
-    else
-    {
-        <form method="post" @onsubmit="SaveAsync" @formname="entry" class="mt-6 grid gap-6" data-testid="entry-form">
-            <AntiforgeryToken />
-            <input type="hidden" name="Form.BaseVersion" value="@(_entry?.LatestVersion ?? 0)" />
-            @if (_formError is not null)
-            {
-                <p role="alert" class="rounded-md border border-destructive/50 px-3 py-2 text-sm text-destructive" data-testid="entry-form-error">@_formError</p>
-            }
-            <Card>
-                <CardHeader>
-                    <CardTitle><h2>@L["Fields"]</h2></CardTitle>
-                </CardHeader>
-                <CardContent Class="grid gap-6 sm:grid-cols-2">
-                    @foreach (var field in type.Definition.Fields)
+    <form method="post" @onsubmit="SaveAsync" @formname="entry" class="mt-6 grid gap-6" data-testid="entry-form">
+        <AntiforgeryToken />
+        <input type="hidden" name="Form.BaseVersion" value="@(_entry?.LatestVersion ?? 0)" />
+        @if (_formError is not null)
+        {
+            <p role="alert" class="rounded-md border border-destructive/50 px-3 py-2 text-sm text-destructive" data-testid="entry-form-error">@_formError</p>
+        }
+        <Card>
+            <CardHeader>
+                <CardTitle><h2>@L["Fields"]</h2></CardTitle>
+            </CardHeader>
+            <CardContent Class="grid gap-6 sm:grid-cols-2">
+                @foreach (var field in type.Definition.Fields)
+                {
+                    <FieldWidget Field="field" Value="@Shown.Values.GetValueOrDefault(field.Name)" Error="@_fieldErrors.GetValueOrDefault(field.Name)" Options="@_options.GetValueOrDefault(field.Name, [])" />
+                    @if (type.Definition.IsEntity)
                     {
-                        <FieldWidget Field="field" Value="@Shown.Values.GetValueOrDefault(field.Name)" Error="@_fieldErrors.GetValueOrDefault(field.Name)" Options="@_options.GetValueOrDefault(field.Name, [])" />
+                        <FactFields Field="@field.Name" Values="Shown.Facts" Problems="@_factProblems.GetValueOrDefault(field.Name, new Dictionary<string, string>())" Owners="_owners" Unsourced="@_unsourced.Contains(field.Name)" />
                     }
-                </CardContent>
-            </Card>
-            <Card>
-                <CardHeader>
-                    <CardTitle><h2>@L["Change set"]</h2></CardTitle>
-                    <CardDescription>@L["The reviewer reads why you made the change and where it comes from."]</CardDescription>
-                </CardHeader>
-                <CardContent Class="grid gap-6">
-                    <FormField Label="@L["Why (required)"]" Error="@_rationaleError">
-                        <Textarea name="Form.Rationale" rows="2" value="@Shown.Rationale" required />
-                    </FormField>
-                    <FormField Label="@L["Sources"]" Description="@L["Optional, one per line, such as a URL or a file name."]">
-                        <Textarea name="Form.Sources" rows="2" value="@Shown.Sources" dir="ltr" />
-                    </FormField>
-                </CardContent>
-            </Card>
-            <div>
-                <Button Type="submit" data-action="save">@L["Save to a change set"]</Button>
-            </div>
-        </form>
-    }
+                }
+            </CardContent>
+        </Card>
+        <Card>
+            <CardHeader>
+                <CardTitle><h2>@L["Change set"]</h2></CardTitle>
+                <CardDescription>@L["The reviewer reads why you made the change and where it comes from."]</CardDescription>
+            </CardHeader>
+            <CardContent Class="grid gap-6">
+                <FormField Label="@L["Why (required)"]" Error="@_rationaleError">
+                    <Textarea name="Form.Rationale" rows="2" value="@Shown.Rationale" required />
+                </FormField>
+                <FormField Label="@L["Sources"]" Description="@L["Optional, one per line, such as a URL or a file name."]">
+                    <Textarea name="Form.Sources" rows="2" value="@Shown.Sources" dir="ltr" />
+                </FormField>
+            </CardContent>
+        </Card>
+        <div>
+            <Button Type="submit" data-action="save">@L["Save to a change set"]</Button>
+        </div>
+    </form>
 }
 
 @code {
@@ -79,6 +81,9 @@
     private Entry? _entry;
     private Dictionary<string, IReadOnlyList<FieldOption>> _options = new(StringComparer.Ordinal);
     private Dictionary<string, string> _fieldErrors = new(StringComparer.Ordinal);
+    private Dictionary<string, Dictionary<string, string>> _factProblems = new(StringComparer.Ordinal);
+    private HashSet<string> _unsourced = new(StringComparer.Ordinal);
+    private IReadOnlyList<FieldOption> _owners = [];
     private string? _rationaleError;
     private string? _formError;
 
@@ -127,9 +132,20 @@
         }
 
         Shown = new EntryFormModel { BaseVersion = _entry?.LatestVersion ?? 0 };
+        _unsourced.Clear();
         foreach (var field in _type.Definition.Fields)
         {
             JsonElement? stored = _entry is not null && _entry.Latest.Fields.TryGetProperty(field.Name, out var value) ? value : null;
+            if (_type.Definition.IsEntity)
+            {
+                if (FactValues.IsUnsourced(stored))
+                {
+                    _unsourced.Add(field.Name);
+                }
+
+                stored = FactValues.Show(field.Name, stored, Shown.Facts);
+            }
+
             Shown.Values[field.Name] = FieldValues.Show(field, stored);
         }
 
@@ -139,6 +155,11 @@
     // Until the pickers search (F-SRC), a reference offers every entry of its target type and a media field every asset.
     private async Task LoadOptionsAsync()
     {
+        if (_type!.Definition.IsEntity)
+        {
+            _owners = [.. (await Users.ListAsync()).Where(user => !user.IsDisabled).Select(user => new FieldOption(user.Id.ToString(), user.DisplayName))];
+        }
+
         foreach (var field in _type!.Definition.Fields)
         {
             if (field.Type == "reference" && FieldValues.Setting(field, "target") is { } target)
@@ -157,7 +178,7 @@
 
     private async Task SaveAsync()
     {
-        if (_type is null || Form is null || _type.Definition.IsEntity)
+        if (_type is null || Form is null)
         {
             return;
         }
@@ -190,7 +211,21 @@
                 continue;
             }
 
-            fields[field.Name] = value;
+            if (!_type.Definition.IsEntity)
+            {
+                fields[field.Name] = value;
+                continue;
+            }
+
+            var problems = new Dictionary<string, string>();
+            var fact = FactValues.Read(field.Name, value, Form.Facts, problems);
+            if (fact is null)
+            {
+                _factProblems[field.Name] = problems;
+                continue;
+            }
+
+            fields[field.Name] = fact;
         }
 
         if (string.IsNullOrWhiteSpace(Form.Rationale))
@@ -198,7 +233,7 @@
             _rationaleError = L["Say why you are making this change."];
         }
 
-        if (_fieldErrors.Count > 0 || _rationaleError is not null)
+        if (_fieldErrors.Count > 0 || _factProblems.Count > 0 || _rationaleError is not null)
         {
             Shown = Form;
             return;
diff --git a/src/FluentCMS.Admin/Forms/EntryFormModel.cs b/src/FluentCMS.Admin/Forms/EntryFormModel.cs
index f61dc6568..87b163a85 100644
--- a/src/FluentCMS.Admin/Forms/EntryFormModel.cs
+++ b/src/FluentCMS.Admin/Forms/EntryFormModel.cs
@@ -5,6 +5,9 @@ public sealed class EntryFormModel
 {
     public Dictionary<string, string?> Values { get; set; } = new(StringComparer.Ordinal);
 
+    // For an entity type, each field's source, owner and validity by "field.part" (FactValues).
+    public Dictionary<string, string?> Facts { get; set; } = new(StringComparer.Ordinal);
+
     public string? Rationale { get; set; }
 
     // One per line, such as a URL or a file name.
diff --git a/src/FluentCMS.Admin/Forms/FactValues.cs b/src/FluentCMS.Admin/Forms/FactValues.cs
new file mode 100644
index 000000000..2799cf595
--- /dev/null
+++ b/src/FluentCMS.Admin/Forms/FactValues.cs
@@ -0,0 +1,120 @@
+using System.Globalization;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using FluentCMS.Core.Schema;
+
+namespace FluentCMS.Admin.Forms;
+
+// The fact around an entity field's value (SCH-03): where it comes from, who owns it and when it holds. A generated form posts each
+// part as text under the field's name, such as "price.kind"; this turns them into the fact object entities store, and back.
+public static class FactValues
+{
+    public const string Kind = "kind";
+    public const string Reference = "reference";
+    public const string Owner = "owner";
+
+    public static IReadOnlyList<string> Times { get; } = [FactMetadata.ValidFrom, FactMetadata.ValidUntil, FactMetadata.LastVerified];
+
+    public static string Key(string field, string part) => $"{field}.{part}";
+
+    // The fact for a value, or null with the problems of each part by part name.
+    public static JsonObject? Read(string field, JsonNode value, IReadOnlyDictionary<string, string?> posted, Dictionary<string, string> problems)
+    {
+        string? Part(string part) => posted.GetValueOrDefault(Key(field, part)) is { } text && text.Trim().Length > 0 ? text.Trim() : null;
+
+        var kind = Part(Kind);
+        var reference = Part(Reference);
+        if (kind is not null && !FactMetadata.SourceKinds.Contains(kind))
+        {
+            problems[Kind] = "kind";
+        }
+        else if ((kind is null) != (reference is null))
+        {
+            problems[kind is null ? Kind : Reference] = "source";
+        }
+
+        Guid? owner = null;
+        if (Part(Owner) is { } ownerText)
+        {
+            if (Guid.TryParse(ownerText, out var ownerId))
+            {
+                owner = ownerId;
+            }
+            else
+            {
+                problems[Owner] = "owner";
+            }
+        }
+
+        var times = new Dictionary<string, string?>();
+        foreach (var name in Times)
+        {
+            times[name] = null;
+            if (Part(name) is not { } text)
+            {
+                continue;
+            }
+
+            if (DateTime.TryParseExact(text, [FieldValues.DateTimeFormat, FieldValues.DateTimeFormat + ":ss"], CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal, out var time))
+            {
+                times[name] = time.ToString("yyyy-MM-ddTHH:mm:ssZ", CultureInfo.InvariantCulture);
+            }
+            else
+            {
+                problems[name] = "dateTime";
+            }
+        }
+
+        if (problems.Count > 0)
+        {
+            return null;
+        }
+
+        return new JsonObject
+        {
+            [FactMetadata.Value] = value.DeepClone(),
+            [FactMetadata.Source] = kind is null ? null : new JsonObject { [FactMetadata.SourceKind] = kind, [FactMetadata.SourceReference] = reference },
+            [FactMetadata.Owner] = owner?.ToString(),
+            [FactMetadata.ValidFrom] = times[FactMetadata.ValidFrom],
+            [FactMetadata.ValidUntil] = times[FactMetadata.ValidUntil],
+            [FactMetadata.LastVerified] = times[FactMetadata.LastVerified],
+        };
+    }
+
+    // The stored fact's value for the value widget, and its parts for the metadata widgets.
+    public static JsonElement? Show(string field, JsonElement? stored, IDictionary<string, string?> facts)
+    {
+        if (stored is not { ValueKind: JsonValueKind.Object } fact)
+        {
+            return null;
+        }
+
+        if (fact.TryGetProperty(FactMetadata.Source, out var source) && source.ValueKind == JsonValueKind.Object)
+        {
+            facts[Key(field, Kind)] = source.GetProperty(FactMetadata.SourceKind).GetString();
+            facts[Key(field, Reference)] = source.GetProperty(FactMetadata.SourceReference).GetString();
+        }
+
+        if (fact.TryGetProperty(FactMetadata.Owner, out var owner) && owner.ValueKind == JsonValueKind.String)
+        {
+            facts[Key(field, Owner)] = owner.GetString();
+        }
+
+        foreach (var name in Times)
+        {
+            if (fact.TryGetProperty(name, out var time) && time.ValueKind == JsonValueKind.String
+                && DateTimeOffset.TryParse(time.GetString(), CultureInfo.InvariantCulture, DateTimeStyles.None, out var parsed))
+            {
+                facts[Key(field, name)] = parsed.UtcDateTime.ToString(FieldValues.DateTimeFormat, CultureInfo.InvariantCulture);
+            }
+        }
+
+        return fact.TryGetProperty(FactMetadata.Value, out var value) ? value : null;
+    }
+
+    public static bool IsUnsourced(JsonElement? stored)
+    {
+        return stored is { ValueKind: JsonValueKind.Object } fact
+            && (!fact.TryGetProperty(FactMetadata.Source, out var source) || source.ValueKind != JsonValueKind.Object);
+    }
+}
diff --git a/tests/FluentCMS.IntegrationTests/Browser/AccessibilityTests.cs b/tests/FluentCMS.IntegrationTests/Browser/AccessibilityTests.cs
index ce53a53b7..0d3f11b9c 100644
--- a/tests/FluentCMS.IntegrationTests/Browser/AccessibilityTests.cs
+++ b/tests/FluentCMS.IntegrationTests/Browser/AccessibilityTests.cs
@@ -27,7 +27,7 @@ public async Task The_showcase_desk_and_set_view_have_no_wcag_21_aa_violations()
             AssetMetadata.Create("drill.jpg", "products", ["hero"], null, null).Value))).Value.Id);
         await session.SignInWithKeyboardAsync();
 
-        string[] paths = ["/ui", "/", "/?queue=stale-facts", $"/sets/{set.Id}?queue=awaiting-me", "/security", "/media", $"/media/{asset}", "/content", "/content/product", "/content/product/new"];
+        string[] paths = ["/ui", "/", "/?queue=stale-facts", $"/sets/{set.Id}?queue=awaiting-me", "/security", "/media", $"/media/{asset}", "/content", "/content/product", "/content/product/new", "/content/supplier/new"];
         var violations = new List<string>();
         foreach (var theme in new[] { "light", "dark" })
         {
@@ -54,6 +54,8 @@ private static async Task<ChangeSet> AwaitingReviewAsync(BrowserSession session)
     {
         var type = await session.Host.AsUserAsync<IContentTypeDirectory, ContentType>(session.OwnerId, async directory =>
             (await directory.CreateAsync(new NewContentType("Product", "product", new ContentTypeDefinition([new FieldDefinition("title", "text")])))).Value);
+        await session.Host.AsUserAsync<IContentTypeDirectory, ContentType>(session.OwnerId, async directory =>
+            (await directory.CreateAsync(new NewContentType("Supplier", "supplier", new ContentTypeDefinition([new FieldDefinition("name", "text")], isEntity: true)))).Value);
 
         return await session.Host.AsUserAsync<IChangeSetDirectory, ChangeSet>(session.OwnerId, async directory =>
         {
diff --git a/tests/FluentCMS.IntegrationTests/Browser/BrowserSession.cs b/tests/FluentCMS.IntegrationTests/Browser/BrowserSession.cs
index e4546dce6..4857bf7c5 100644
--- a/tests/FluentCMS.IntegrationTests/Browser/BrowserSession.cs
+++ b/tests/FluentCMS.IntegrationTests/Browser/BrowserSession.cs
@@ -35,7 +35,7 @@ public static async Task<BrowserSession> StartAsync()
         var playwright = await Playwright.CreateAsync();
         var browser = await playwright.Chromium.LaunchAsync(new BrowserTypeLaunchOptions { Headless = true });
         var page = await browser.NewPageAsync(new BrowserNewPageOptions { ViewportSize = new ViewportSize { Width = 1280, Height = 900 } });
-        page.SetDefaultTimeout(15_000);
+        page.SetDefaultTimeout(30_000);
 
         return new BrowserSession(install, host, ownerId, playwright, browser, page);
     }
diff --git a/tests/FluentCMS.IntegrationTests/Forms/EntityFormScreenTests.cs b/tests/FluentCMS.IntegrationTests/Forms/EntityFormScreenTests.cs
new file mode 100644
index 000000000..0edeb35d6
--- /dev/null
+++ b/tests/FluentCMS.IntegrationTests/Forms/EntityFormScreenTests.cs
@@ -0,0 +1,95 @@
+using System.Net;
+using System.Text.Json;
+using FluentCMS.Core.ChangeSets;
+using FluentCMS.Core.Content;
+using FluentCMS.Core.Entities;
+using FluentCMS.Core.Schema;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace FluentCMS.IntegrationTests.Forms;
+
+public sealed class EntityFormScreenTests
+{
+    [Fact]
+    public async Task A_person_creates_an_entity_whose_facts_carry_their_source_owner_and_validity()
+    {
+        using var install = new TemporaryInstall();
+        await using var host = await AdminHost.StartAsync(install);
+        var ownerId = await host.CreateFirstAdministratorAsync();
+        await ProductTypeAsync(host, ownerId);
+        await host.SignInAsync(AdminHost.Owner);
+
+        var form = await host.Client.GetStringAsync("/content/product/new");
+        Assert.Contains("name=\"Form.Facts[price.kind]\"", form);
+        Assert.Contains($"<option value=\"{ownerId}\">", form);
+
+        var saved = await host.SubmitAsync("/content/product/new", "entry", new Dictionary<string, string>
+        {
+            ["Form.Values[name]"] = "Drill",
+            ["Form.Values[price]"] = "129.5",
+            ["Form.Facts[price.kind]"] = "url",
+            ["Form.Facts[price.reference]"] = "https://example.com/catalog",
+            ["Form.Facts[price.owner]"] = ownerId.ToString(),
+            ["Form.Facts[price.validUntil]"] = "2026-12-31T23:59",
+            ["Form.Facts[price.lastVerified]"] = "2026-10-18T09:00",
+            ["Form.Rationale"] = "Add the drill.",
+            ["Form.BaseVersion"] = "0",
+        });
+
+        var set = await host.AsUserAsync<IChangeSetDirectory, ChangeSet>(ownerId, async sets => (await sets.GetAsync(Guid.Parse(host.LocationOf(saved)![6..42]))).Value);
+        var operation = Assert.Single(set.Operations);
+        Assert.Equal((OperationKind.Create, ItemKind.Entity), (operation.Kind, operation.ItemKind));
+        var entity = await host.AsUserAsync<IEntryDirectory, Entry>(ownerId, async entries => (await entries.GetAsync(operation.ItemId)).Value);
+        var price = entity.Latest.Fields.GetProperty("price");
+        Assert.Equal(129.5m, price.GetProperty("value").GetDecimal());
+        Assert.Equal(("url", "https://example.com/catalog"), (price.GetProperty("source").GetProperty("kind").GetString(), price.GetProperty("source").GetProperty("reference").GetString()));
+        Assert.Equal(ownerId.ToString(), price.GetProperty("owner").GetString());
+        Assert.Equal("2026-12-31T23:59:00Z", price.GetProperty("validUntil").GetString());
+        Assert.Equal("2026-10-18T09:00:00Z", price.GetProperty("lastVerified").GetString());
+        Assert.Equal(JsonValueKind.Null, price.GetProperty("validFrom").ValueKind);
+
+        // The name was saved without a source: it is stored, flagged unsourced, and the form says so.
+        var unsourced = await host.AsUserAsync<IEntityFacts, IReadOnlyList<FactFlag>>(ownerId, async facts => (await facts.UnsourcedAsync("product")).Value);
+        Assert.Equal(["name"], unsourced.Select(flag => flag.Field));
+        var edit = await host.Client.GetStringAsync($"/content/product/{entity.Id}");
+        Assert.Contains("value=\"https://example.com/catalog\"", edit);
+        Assert.Contains("value=\"2026-12-31T23:59\"", edit);
+        Assert.Contains("<option value=\"url\" selected", edit);
+        Assert.Equal(1, System.Text.RegularExpressions.Regex.Count(edit, "data-testid=\"fact-unsourced\""));
+    }
+
+    [Fact]
+    public async Task A_half_given_source_and_a_bad_time_are_reported_and_nothing_is_stored()
+    {
+        using var install = new TemporaryInstall();
+        await using var host = await AdminHost.StartAsync(install);
+        var ownerId = await host.CreateFirstAdministratorAsync();
+        await ProductTypeAsync(host, ownerId);
+        await host.SignInAsync(AdminHost.Owner);
+
+        var refused = await host.SubmitAsync("/content/product/new", "entry", new Dictionary<string, string>
+        {
+            ["Form.Values[name]"] = "Drill",
+            ["Form.Values[price]"] = "10",
+            ["Form.Facts[name.kind]"] = "url",
+            ["Form.Facts[price.validUntil]"] = "next year",
+            ["Form.Rationale"] = "Add the drill.",
+            ["Form.BaseVersion"] = "0",
+        });
+        var page = await refused.Content.ReadAsStringAsync();
+
+        Assert.Equal(HttpStatusCode.OK, refused.StatusCode);
+        Assert.Contains("Give both the kind of source and the source, or neither.", page);
+        Assert.Contains("Enter a date and a time.", page);
+        Assert.Contains("value=\"next year\"", page);
+        Assert.Empty(await host.AsUserAsync<IEntryDirectory, IReadOnlyList<EntrySummary>>(ownerId, async entries => (await entries.ListAsync("product")).Value));
+    }
+
+    private static Task<ContentType> ProductTypeAsync(AdminHost host, Guid ownerId)
+    {
+        return host.AsUserAsync<IContentTypeDirectory, ContentType>(ownerId, async types => (await types.CreateAsync(new NewContentType(
+            "Product",
+            "product",
+            new ContentTypeDefinition([new FieldDefinition("name", "text", required: true), new FieldDefinition("price", "number")], isEntity: true)))).Value);
+    }
+}
diff --git a/tests/FluentCMS.Tests/Admin/FactValuesTests.cs b/tests/FluentCMS.Tests/Admin/FactValuesTests.cs
new file mode 100644
index 000000000..98e25955f
--- /dev/null
+++ b/tests/FluentCMS.Tests/Admin/FactValuesTests.cs
@@ -0,0 +1,68 @@
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using FluentCMS.Admin.Forms;
+
+namespace FluentCMS.Tests.Admin;
+
+public sealed class FactValuesTests
+{
+    private static readonly Guid Owner = Guid.Parse("0192f3a1-7c2e-7a4b-9d3e-1f2a3b4c5d6e");
+
+    [Fact]
+    public void Posted_parts_become_the_fact_object_with_every_property()
+    {
+        var problems = new Dictionary<string, string>();
+
+        var fact = FactValues.Read("price", JsonValue.Create(10m), Posted(
+            ("price.kind", "url"),
+            ("price.reference", " https://example.com "),
+            ("price.owner", Owner.ToString()),
+            ("price.validFrom", "2026-01-01T00:00")), problems);
+
+        Assert.Empty(problems);
+        Assert.Equal(
+            $$"""{"value":10,"source":{"kind":"url","reference":"https://example.com"},"owner":"{{Owner}}","validFrom":"2026-01-01T00:00:00Z","validUntil":null,"lastVerified":null}""",
+            fact!.ToJsonString());
+    }
+
+    [Fact]
+    public void A_fact_without_any_details_is_unsourced_and_keeps_null_properties()
+    {
+        var fact = FactValues.Read("name", JsonValue.Create("Drill"), Posted(), []);
+
+        Assert.Equal("""{"value":"Drill","source":null,"owner":null,"validFrom":null,"validUntil":null,"lastVerified":null}""", fact!.ToJsonString());
+        Assert.True(FactValues.IsUnsourced(JsonDocument.Parse(fact.ToJsonString()).RootElement));
+    }
+
+    [Theory]
+    [InlineData("price.kind", "url", "reference", "source")]
+    [InlineData("price.reference", "x", "kind", "source")]
+    [InlineData("price.kind", "rumour", "kind", "kind")]
+    [InlineData("price.owner", "someone", "owner", "owner")]
+    [InlineData("price.lastVerified", "yesterday", "lastVerified", "dateTime")]
+    public void A_part_that_cannot_stand_is_a_problem_of_that_part(string key, string posted, string part, string problem)
+    {
+        var problems = new Dictionary<string, string>();
+
+        Assert.Null(FactValues.Read("price", JsonValue.Create(10m), Posted((key, posted)), problems));
+        Assert.Equal(problem, problems[part]);
+    }
+
+    [Fact]
+    public void A_stored_fact_shows_its_value_and_parts()
+    {
+        var facts = new Dictionary<string, string?>();
+        var stored = JsonDocument.Parse($$"""{"value": 10, "source": {"kind": "file", "reference": "prices.csv"}, "owner": "{{Owner}}", "validFrom": null, "validUntil": "2026-12-31T23:59:00+01:00", "lastVerified": null}""").RootElement;
+
+        var value = FactValues.Show("price", stored, facts);
+
+        Assert.Equal(10, value!.Value.GetInt32());
+        Assert.Equal(("file", "prices.csv", Owner.ToString(), "2026-12-31T22:59"), (facts["price.kind"], facts["price.reference"], facts["price.owner"], facts["price.validUntil"]));
+        Assert.False(FactValues.IsUnsourced(stored));
+    }
+
+    private static Dictionary<string, string?> Posted(params (string Key, string Value)[] parts)
+    {
+        return parts.ToDictionary(part => part.Key, part => (string?)part.Value);
+    }
+}