diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BeyondFactsLabStore.Forms.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BeyondFactsLabStore.Forms.cs
index 8727e329e..f74eca8fd 100644
--- a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BeyondFactsLabStore.Forms.cs	
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BeyondFactsLabStore.Forms.cs	
@@ -113,12 +113,19 @@ public sealed partial class BeyondFactsLabStore
             throw new InvalidDataException("This version of AI Studio cannot open the form.", exception);
         }
 
-        if (form is null || form.SchemaVersion is < 1 or > BflStepFormData.CURRENT_SCHEMA_VERSION || IsNull(form.Values) || form.CardSort is { } cardSort && IsBroken(cardSort))
+        if (form is null || form.SchemaVersion is < 1 or > BflStepFormData.CURRENT_SCHEMA_VERSION || IsNull(form.Values) || form.CardSort is { } cardSort && IsBroken(cardSort) || form.Simulation is { } simulation && IsBroken(simulation))
             throw new InvalidDataException("This version of AI Studio cannot open the form.");
 
         return form;
     }
 
+    /// <summary>
+    /// Tells whether a stored simulation lacks one of its parts, which JSON can make null, or names a mode this version
+    /// does not know.
+    /// </summary>
+    /// <param name="simulation">The simulation.</param>
+    private static bool IsBroken(BflSimulation simulation) => !Enum.IsDefined(simulation.Mode) || IsNull(simulation.People) || simulation.People.Any(IsNull);
+
     /// <summary>
     /// Tells whether a stored card sort lacks one of its parts, which JSON can make null.
     /// </summary>
diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflEffectiveSimulation.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflEffectiveSimulation.cs
new file mode 100644
index 000000000..8826a5500
--- /dev/null
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflEffectiveSimulation.cs	
@@ -0,0 +1,35 @@
+namespace AIStudio.Assistants.BeyondFactsLab;
+
+/// <summary>
+/// Whom the chat of the step "Test situation" of the BeyondFacts Lab actually plays: the mode and the people which
+/// count of what the person chose.
+/// </summary>
+/// <remarks>
+/// A chosen person counts while they are a candidate, see BflSimulationCandidates, and only as many as the mode allows,
+/// in the order of the list of participants. When nobody of the chosen people counts, the chat plays generic
+/// counterparts, as it did before the person chose a mode.
+/// </remarks>
+/// <param name="Mode">The mode in effect.</param>
+/// <param name="People">The research on the people the chat plays, in the order of the list; empty for generic counterparts.</param>
+public sealed record BflEffectiveSimulation(BflSimulationMode Mode, IReadOnlyList<BflPersonResearch> People)
+{
+    /// <summary>
+    /// The simulation with generic counterparts, no specific person.
+    /// </summary>
+    public static readonly BflEffectiveSimulation GENERIC = new(BflSimulationMode.GENERIC, []);
+
+    /// <summary>
+    /// Gets whom the chat plays of what the person chose.
+    /// </summary>
+    /// <param name="simulation">What the person chose; null when they chose nothing.</param>
+    /// <param name="candidates">The people the chat may play, in the order of the list, see BflSimulationCandidates.</param>
+    /// <returns>The simulation in effect.</returns>
+    public static BflEffectiveSimulation Of(BflSimulation? simulation, IReadOnlyList<BflPersonResearch> candidates)
+    {
+        if (simulation is null || !simulation.Mode.HasPeople)
+            return GENERIC;
+
+        var people = candidates.Where(candidate => simulation.HasChosen(candidate.Name)).Take(simulation.Mode.MaxPeople).ToList();
+        return people.Count is 0 ? GENERIC : new(simulation.Mode, people);
+    }
+}
\ No newline at end of file
diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulation.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulation.cs
new file mode 100644
index 000000000..c52b055e5
--- /dev/null
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulation.cs	
@@ -0,0 +1,31 @@
+namespace AIStudio.Assistants.BeyondFactsLab;
+
+/// <summary>
+/// Whom the person chose for the chat of the step "Test situation" of the BeyondFacts Lab to play: the mode, and the
+/// people from the research on single participants.
+/// </summary>
+/// <remarks>
+/// The choice belongs to the details of its step and is stored with them, see BflStepFormData.Simulation. It is the
+/// opt-in of the person: the chat plays a real person only while the person chose them here. What counts is the
+/// effective simulation, see BflEffectiveSimulation: a name which is no longer a candidate stays stored, but counts no
+/// longer, and so do the names beyond what the mode allows.
+/// </remarks>
+public sealed class BflSimulation
+{
+    /// <summary>
+    /// Gets or sets the mode.
+    /// </summary>
+    public BflSimulationMode Mode { get; set; } = BflSimulationMode.GENERIC;
+
+    /// <summary>
+    /// Gets or sets the names of the people the person chose, as the list of participants gives them, in no particular
+    /// order.
+    /// </summary>
+    public List<string> People { get; set; } = [];
+
+    /// <summary>
+    /// Tells whether the person chose a person, regardless of case and of the spaces between the words.
+    /// </summary>
+    /// <param name="name">The name of the person.</param>
+    public bool HasChosen(string name) => this.People.Any(chosen => string.Equals(BflParticipant.NameKey(chosen), BflParticipant.NameKey(name), StringComparison.Ordinal));
+}
\ No newline at end of file
diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationBudget.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationBudget.cs
new file mode 100644
index 000000000..df4fa07c7
--- /dev/null
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationBudget.cs	
@@ -0,0 +1,52 @@
+using AIStudio.Models;
+
+namespace AIStudio.Assistants.BeyondFactsLab;
+
+/// <summary>
+/// Estimates whether the context window of a model holds the simulation the person chose in the step "Test situation"
+/// of the BeyondFacts Lab.
+/// </summary>
+/// <remarks>
+/// The prompt of the step carries the dossier of every person the chat plays, in full: unlike the material, a dossier
+/// is never shortened, since the chat must not play a person after half of what they said. The estimate adds the
+/// dossiers to the smallest window the lab accepts at all, which leaves room for the fixed part of the prompt, the
+/// details, and the conversation, and counts the characters of a dossier the way the budget of the material does. The
+/// material then gets what is left, see BflMaterialBudget.
+/// </remarks>
+public static class BflSimulationBudget
+{
+    /// <summary>
+    /// Estimates how many tokens the dossiers of the people the chat plays take in the prompt.
+    /// </summary>
+    /// <param name="people">The research on the people the chat plays.</param>
+    /// <returns>The estimated tokens.</returns>
+    public static int DossierTokens(IReadOnlyList<BflPersonResearch> people)
+    {
+        var characters = people.Sum(person => person.Stages.Sum(stage => stage.Research.Text.Trim().Length));
+        return (characters + BflMaterialBudget.CHARACTERS_PER_TOKEN - 1) / BflMaterialBudget.CHARACTERS_PER_TOKEN;
+    }
+
+    /// <summary>
+    /// Estimates how many tokens a model needs to read at once for a simulation.
+    /// </summary>
+    /// <param name="people">The research on the people the chat plays.</param>
+    /// <returns>The estimated tokens.</returns>
+    public static int RequiredTokens(IReadOnlyList<BflPersonResearch> people) => BflModelRequirements.MINIMUM_CONTEXT_TOKENS + DossierTokens(people);
+
+    /// <summary>
+    /// Checks whether the context window of a model is likely to hold a simulation.
+    /// </summary>
+    /// <param name="simulation">The simulation in effect.</param>
+    /// <param name="contextWindow">The context window of the model, as it ships.</param>
+    /// <returns>Whether the window holds the simulation, nobody knows, or it is likely too small.</returns>
+    public static BflSimulationFit Check(BflEffectiveSimulation simulation, ContextWindow contextWindow)
+    {
+        if (simulation.People.Count is 0)
+            return BflSimulationFit.FITS;
+
+        if (!contextWindow.IsKnown)
+            return BflSimulationFit.UNKNOWN_CONTEXT;
+
+        return contextWindow.DefaultTokens < RequiredTokens(simulation.People) ? BflSimulationFit.TOO_SMALL : BflSimulationFit.FITS;
+    }
+}
\ No newline at end of file
diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationCandidates.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationCandidates.cs
new file mode 100644
index 000000000..5baaf0abf
--- /dev/null
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationCandidates.cs	
@@ -0,0 +1,35 @@
+namespace AIStudio.Assistants.BeyondFactsLab;
+
+/// <summary>
+/// Decides whom of the participants the chat of the step "Test situation" of the BeyondFacts Lab may play.
+/// </summary>
+/// <remarks>
+/// Only a person with a documented public position qualifies, so that the chat never makes up what somebody stands
+/// for: the person stands on the current list of participants, and the stage "Positions" of the research on them is
+/// done and holds text. For an event which is not public, no research counts, see BflEventVisibility, and nobody
+/// qualifies. The prompt of the simulation still lets the chat refuse to play a person whose dossier documents no
+/// position after all, since only the model reads what the text says.
+/// </remarks>
+public static class BflSimulationCandidates
+{
+    /// <summary>
+    /// Gets the people the chat of the step "Test situation" may play.
+    /// </summary>
+    /// <param name="forms">The forms of the preparation, by their steps.</param>
+    /// <param name="topics">The research on the topics, with the list of participants.</param>
+    /// <param name="people">The research on every person stored for the preparation.</param>
+    /// <returns>The research on each person who qualifies, in the order of the list.</returns>
+    public static IReadOnlyList<BflPersonResearch> Of(IReadOnlyDictionary<BflStep, BflStepFormData> forms, IReadOnlyDictionary<BflResearchTopic, BflResearch> topics, IReadOnlyList<BflPersonResearch> people)
+    {
+        if (BflEventVisibility.IsNotPublic(forms))
+            return [];
+
+        return [.. BflStepResearch.Of(topics, people).People.Where(HasPositions)];
+    }
+
+    /// <summary>
+    /// Tells whether the research on a person documents public positions: its stage "Positions" is done and holds text.
+    /// </summary>
+    /// <param name="person">The research on the person.</param>
+    public static bool HasPositions(BflPersonResearch person) => person.StageOf(BflPersonResearchStage.POSITIONS) is { } positions && positions.Text.Trim().Length > 0;
+}
\ No newline at end of file
diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationFit.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationFit.cs
new file mode 100644
index 000000000..bf60e368b
--- /dev/null
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationFit.cs	
@@ -0,0 +1,23 @@
+namespace AIStudio.Assistants.BeyondFactsLab;
+
+/// <summary>
+/// Whether the context window of a model is likely to hold the simulation the person chose in the step "Test
+/// situation" of the BeyondFacts Lab, see BflSimulationBudget.
+/// </summary>
+public enum BflSimulationFit
+{
+    /// <summary>
+    /// The window is known and holds the simulation, or the simulation plays nobody from the research.
+    /// </summary>
+    FITS,
+
+    /// <summary>
+    /// Nobody knows the window of the model, so the lab cannot tell; it warns the person and lets the chat run.
+    /// </summary>
+    UNKNOWN_CONTEXT,
+
+    /// <summary>
+    /// The window is known and likely too small; the chat does not send.
+    /// </summary>
+    TOO_SMALL,
+}
\ No newline at end of file
diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationMode.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationMode.cs
new file mode 100644
index 000000000..1a87eb005
--- /dev/null
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationMode.cs	
@@ -0,0 +1,31 @@
+namespace AIStudio.Assistants.BeyondFactsLab;
+
+/// <summary>
+/// Whom the chat of the step "Test situation" of the BeyondFacts Lab plays: generic counterparts, or people from the
+/// research on single participants in a format of the event.
+/// </summary>
+/// <remarks>
+/// The names are stored, so they never change. A new format joins as a new member, see BflSimulationModeExtensions.
+/// </remarks>
+public enum BflSimulationMode
+{
+    /// <summary>
+    /// Generic counterparts, no specific person: the step as it was before the lab simulated people.
+    /// </summary>
+    GENERIC,
+
+    /// <summary>
+    /// One person from the research, after their dossier.
+    /// </summary>
+    SINGLE_PERSON,
+
+    /// <summary>
+    /// A panel discussion with up to three people from the research.
+    /// </summary>
+    PANEL_DISCUSSION,
+
+    /// <summary>
+    /// A press conference with up to five people from the research.
+    /// </summary>
+    PRESS_CONFERENCE,
+}
\ No newline at end of file
diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationModeExtensions.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationModeExtensions.cs
new file mode 100644
index 000000000..769c357e4
--- /dev/null
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflSimulationModeExtensions.cs	
@@ -0,0 +1,47 @@
+namespace AIStudio.Assistants.BeyondFactsLab;
+
+/// <summary>
+/// What the BeyondFacts Lab shows and allows for a mode of the simulation in the step "Test situation".
+/// </summary>
+public static class BflSimulationModeExtensions
+{
+    private static string TB(string fallbackEN) => Tools.PluginSystem.I18N.I.T(fallbackEN, typeof(BflSimulationModeExtensions).Namespace, nameof(BflSimulationModeExtensions));
+
+    /// <param name="mode">The mode.</param>
+    extension(BflSimulationMode mode)
+    {
+        /// <summary>
+        /// Gets the name of the mode, as the selection shows it.
+        /// </summary>
+        public string Title => mode switch
+        {
+            BflSimulationMode.SINGLE_PERSON => TB("One person from the research"),
+            BflSimulationMode.PANEL_DISCUSSION => TB("Panel discussion with up to three people"),
+            BflSimulationMode.PRESS_CONFERENCE => TB("Press conference with up to five people"),
+
+            _ => TB("Generic counterparts, no specific person"),
+        };
+
+        /// <summary>
+        /// Gets how many people from the research the chat plays at most in this mode; none for generic counterparts.
+        /// </summary>
+        public int MaxPeople => mode switch
+        {
+            BflSimulationMode.SINGLE_PERSON => 1,
+            BflSimulationMode.PANEL_DISCUSSION => 3,
+            BflSimulationMode.PRESS_CONFERENCE => 5,
+
+            _ => 0,
+        };
+
+        /// <summary>
+        /// Gets whether the chat plays people from the research in this mode.
+        /// </summary>
+        public bool HasPeople => mode.MaxPeople > 0;
+
+        /// <summary>
+        /// Gets every mode, in the order the selection shows them.
+        /// </summary>
+        public static IReadOnlyList<BflSimulationMode> All => Enum.GetValues<BflSimulationMode>();
+    }
+}
\ No newline at end of file
diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflStaleness.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflStaleness.cs
index 9314f70e7..3efac8e56 100644
--- a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflStaleness.cs	
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflStaleness.cs	
@@ -96,7 +96,8 @@ public static class BflStaleness
     /// <remarks>
     /// Line endings and spaces around a value do not count, since they change nothing the model reads. The card sort
     /// counts as a detail of its step; without one, or with an empty one, the fingerprint is the same as before the lab
-    /// had a card sort, so that no confirmation of an older preparation turns into "Details changed".
+    /// had a card sort, so that no confirmation of an older preparation turns into "Details changed". The same holds for
+    /// the simulation of the step "Test situation" with generic counterparts.
     /// </remarks>
     /// <param name="form">The form.</param>
     /// <returns>The fingerprint, in hexadecimal digits.</returns>
@@ -115,9 +116,28 @@ public static class BflStaleness
         if (form.CardSort is { IsEmpty: false } cardSort)
             AppendCardSort(text, cardSort);
 
+        if (form.Simulation is { Mode.HasPeople: true } simulation)
+            AppendSimulation(text, simulation);
+
         return Convert.ToHexStringLower(SHA256.HashData(Encoding.UTF8.GetBytes(text.ToString())));
     }
 
+    /// <summary>
+    /// Appends a simulation with people to the text a fingerprint is computed from.
+    /// </summary>
+    /// <remarks>
+    /// Generic counterparts add nothing, so that the fingerprint stays the same as before the lab simulated people. The
+    /// people count as a set, by the keys of their names: the order the person chose them in means nothing.
+    /// </remarks>
+    /// <param name="text">The text so far.</param>
+    /// <param name="simulation">The simulation.</param>
+    private static void AppendSimulation(StringBuilder text, BflSimulation simulation)
+    {
+        text.Append(SEPARATOR).Append("simulation").Append(SEPARATOR).Append(simulation.Mode.ToString()).Append(SEPARATOR);
+        foreach (var key in simulation.People.Select(BflParticipant.NameKey).Distinct(StringComparer.Ordinal).Order(StringComparer.Ordinal))
+            text.Append(key).Append(SEPARATOR);
+    }
+
     /// <summary>
     /// Appends a card sort to the text a fingerprint is computed from.
     /// </summary>
diff --git a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflStepFormData.cs b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflStepFormData.cs
index 72c7be123..62da9a706 100644
--- a/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflStepFormData.cs	
+++ b/app/MindWork AI Studio/Assistants/BeyondFactsLab/BflStepFormData.cs	
@@ -7,14 +7,15 @@ namespace AIStudio.Assistants.BeyondFactsLab;
 /// </summary>
 /// <remarks>
 /// The values are stored under the IDs of the fields of BflFieldCatalog. A value of a field this version does not
-/// know, e.g., one a newer version added, stays as it is and is written back unchanged. Version 2 added the card sort.
+/// know, e.g., one a newer version added, stays as it is and is written back unchanged. Version 2 added the card sort,
+/// version 3 the simulation.
 /// </remarks>
 public sealed class BflStepFormData
 {
     /// <summary>
     /// The version of the stored form this version of AI Studio writes. Raise it with every new property.
     /// </summary>
-    public const int CURRENT_SCHEMA_VERSION = 2;
+    public const int CURRENT_SCHEMA_VERSION = 3;
 
     /// <summary>
     /// The character which separates the options of a field with several choices.
@@ -40,6 +41,15 @@ public sealed class BflStepFormData
     [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
     public BflCardSort? CardSort { get; set; }
 
+    /// <summary>
+    /// Gets or sets whom the chat of the step "Test situation" plays, see BflSimulation.
+    /// </summary>
+    /// <remarks>
+    /// Null for every other step, and until the person chooses a mode there; the file then leaves it out.
+    /// </remarks>
+    [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
+    public BflSimulation? Simulation { get; set; }
+
     /// <summary>
     /// Gets the value of a field, or an empty string when the field has none.
     /// </summary>
diff --git a/app/Tests/BeyondFactsLab/BeyondFactsLabStoreTests.cs b/app/Tests/BeyondFactsLab/BeyondFactsLabStoreTests.cs
index bf85160de..e65606c6c 100644
--- a/app/Tests/BeyondFactsLab/BeyondFactsLabStoreTests.cs
+++ b/app/Tests/BeyondFactsLab/BeyondFactsLabStoreTests.cs
@@ -405,6 +405,54 @@ public sealed class BeyondFactsLabStoreTests
         await Assert.ThrowsAsync<InvalidDataException>(async () => await store.LoadFormAsync(created.ProjectId, BflStep.VALUES_AND_PERSPECTIVES));
     }
 
+    [Test]
+    public async Task ASimulationIsStoredWithTheFormOfItsStep()
+    {
+        var store = this.CreateStore();
+        var created = await store.CreateAsync("Panel");
+        var form = new BflStepFormData { Simulation = new() { Mode = BflSimulationMode.PANEL_DISCUSSION, People = ["Eva Klein", "Frank Ott"] } };
+
+        await store.SaveFormAsync(created.ProjectId, BflStep.TEST_SITUATION, form);
+        var json = await File.ReadAllTextAsync(Path.Combine(this.RootDirectory, created.ProjectId.ToString("D"), "steps", "06-test", "form.json"));
+        var loaded = (await this.CreateStore().LoadFormAsync(created.ProjectId, BflStep.TEST_SITUATION)).Simulation;
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(json, Does.Contain("\"PANEL_DISCUSSION\""), "The mode is stored by its name, which never changes.");
+            Assert.That(loaded, Is.Not.Null);
+            Assert.That(loaded!.Mode, Is.EqualTo(BflSimulationMode.PANEL_DISCUSSION));
+            Assert.That(loaded.People, Is.EqualTo(new[] { "Eva Klein", "Frank Ott" }));
+        }
+    }
+
+    [Test]
+    public async Task AFormOfTheSecondVersionIsStillOpenedWithoutASimulation()
+    {
+        var store = this.CreateStore();
+        var created = await store.CreateAsync("Panel");
+        await this.WriteFormFileAsync(created.ProjectId, "06-test", """{ "schemaVersion": 2, "values": { "test_notes": "Text" } }""");
+
+        var form = await store.LoadFormAsync(created.ProjectId, BflStep.TEST_SITUATION);
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(form.Get(BflFieldCatalog.TEST_NOTES), Is.EqualTo("Text"));
+            Assert.That(form.Simulation, Is.Null);
+        }
+    }
+
+    [TestCase("""{ "schemaVersion": 3, "values": {}, "simulation": { "mode": "PANEL_DISCUSSION", "people": null } }""")]
+    [TestCase("""{ "schemaVersion": 3, "values": {}, "simulation": { "mode": "PANEL_DISCUSSION", "people": [ null ] } }""")]
+    [TestCase("""{ "schemaVersion": 3, "values": {}, "simulation": { "mode": 42, "people": [] } }""")]
+    public async Task AFormWithABrokenSimulationIsNotOpened(string json)
+    {
+        var store = this.CreateStore();
+        var created = await store.CreateAsync("Panel");
+        await this.WriteFormFileAsync(created.ProjectId, "06-test", json);
+
+        await Assert.ThrowsAsync<InvalidDataException>(async () => await store.LoadFormAsync(created.ProjectId, BflStep.TEST_SITUATION));
+    }
+
     [Test]
     public async Task AStepWithoutAFormGetsAnEmptyOne()
     {
@@ -463,7 +511,7 @@ public sealed class BeyondFactsLabStoreTests
     [Test]
     public async Task AFormOfANewerVersionIsNotOverwritten()
     {
-        const string NEWER = """{ "schemaVersion": 3, "values": {} }""";
+        const string NEWER = """{ "schemaVersion": 4, "values": {} }""";
         var store = this.CreateStore();
         var created = await store.CreateAsync("Panel");
         var formPath = await this.WriteFormFileAsync(created.ProjectId, "05-strategy", NEWER);
diff --git a/app/Tests/BeyondFactsLab/BflSimulationTests.cs b/app/Tests/BeyondFactsLab/BflSimulationTests.cs
new file mode 100644
index 000000000..714ba59e4
--- /dev/null
+++ b/app/Tests/BeyondFactsLab/BflSimulationTests.cs
@@ -0,0 +1,173 @@
+using AIStudio.Assistants.BeyondFactsLab;
+using AIStudio.Models;
+
+namespace AIStudio.Tests.BeyondFactsLab;
+
+/// <summary>
+/// Checks whom the chat of the step "Test situation" of the BeyondFacts Lab may play, whom it plays of what the person
+/// chose, and whether a model reads enough for it.
+/// </summary>
+[TestFixture]
+public sealed class BflSimulationTests
+{
+    private static readonly DateTimeOffset CREATED_AT_UTC = new(2026, 11, 15, 10, 0, 0, TimeSpan.Zero);
+
+    [Test]
+    public void OnlyAListedPersonWithDocumentedPositionsQualifies()
+    {
+        var forms = Forms();
+        BflPersonResearch[] people =
+        [
+            Person(forms, "Eva Klein", BflPersonResearchStage.All),
+            Person(forms, "Frank Ott", [BflPersonResearchStage.PROFILE]),
+            Person(forms, "Gina Roth", [BflPersonResearchStage.PROFILE, BflPersonResearchStage.POSITIONS], positionsText: "  "),
+            Person(forms, "Nicht Gelistet", BflPersonResearchStage.All)
+        ];
+
+        var candidates = BflSimulationCandidates.Of(forms, Topics(forms, "Eva Klein", "Frank Ott", "Gina Roth"), people);
+
+        Assert.That(candidates.Select(person => person.Name), Is.EqualTo(new[] { "Eva Klein" }));
+    }
+
+    [Test]
+    public void TheCandidatesComeInTheOrderOfTheList()
+    {
+        var forms = Forms();
+        BflPersonResearch[] people = [Person(forms, "Eva Klein", BflPersonResearchStage.All), Person(forms, "Frank Ott", BflPersonResearchStage.All)];
+
+        var candidates = BflSimulationCandidates.Of(forms, Topics(forms, "Frank Ott", "Eva Klein"), people);
+
+        Assert.That(candidates.Select(person => person.Name), Is.EqualTo(new[] { "Frank Ott", "Eva Klein" }));
+    }
+
+    [Test]
+    public void NobodyQualifiesForAnEventWhichIsNotPublic()
+    {
+        var forms = Forms();
+        BflPersonResearch[] people = [Person(forms, "Eva Klein", BflPersonResearchStage.All)];
+        var topics = Topics(forms, "Eva Klein");
+        forms[BflStep.FRAMEWORK].Set(BflFieldCatalog.EVENT_VISIBILITY, BflFieldCatalog.EVENT_NOT_PUBLIC);
+
+        Assert.That(BflSimulationCandidates.Of(forms, topics, people), Is.Empty);
+    }
+
+    [Test]
+    public void GenericCounterpartsPlayNobody()
+    {
+        var candidates = Candidates("Eva Klein");
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(BflEffectiveSimulation.Of(null, candidates), Is.SameAs(BflEffectiveSimulation.GENERIC));
+            Assert.That(BflEffectiveSimulation.Of(new() { Mode = BflSimulationMode.GENERIC, People = ["Eva Klein"] }, candidates), Is.SameAs(BflEffectiveSimulation.GENERIC));
+        }
+    }
+
+    [TestCase(BflSimulationMode.SINGLE_PERSON, 1)]
+    [TestCase(BflSimulationMode.PANEL_DISCUSSION, 3)]
+    [TestCase(BflSimulationMode.PRESS_CONFERENCE, 5)]
+    public void AModePlaysAtMostItsNumberOfPeopleInTheOrderOfTheList(BflSimulationMode mode, int expected)
+    {
+        string[] names = ["Anna Arendt", "Bruno Berg", "Clara Cramer", "David Dorn", "Eva Klein", "Frank Ott"];
+        var candidates = Candidates(names);
+        var simulation = new BflSimulation { Mode = mode, People = [.. names.Reverse()] };
+
+        var effective = BflEffectiveSimulation.Of(simulation, candidates);
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(mode.MaxPeople, Is.EqualTo(expected));
+            Assert.That(effective.Mode, Is.EqualTo(mode));
+            Assert.That(effective.People.Select(person => person.Name), Is.EqualTo(names.Take(expected)));
+        }
+    }
+
+    [Test]
+    public void APersonWhoIsNoLongerACandidateCountsNoLonger()
+    {
+        var candidates = Candidates("Eva Klein", "Frank Ott");
+        var simulation = new BflSimulation { Mode = BflSimulationMode.PANEL_DISCUSSION, People = ["Nicht Mehr Gelistet", "frank  ott"] };
+
+        var effective = BflEffectiveSimulation.Of(simulation, candidates);
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(effective.People.Select(person => person.Name), Is.EqualTo(new[] { "Frank Ott" }));
+            Assert.That(simulation.People, Has.Count.EqualTo(2), "What the person chose stays stored.");
+        }
+    }
+
+    [Test]
+    public void AModeWithoutAnyChosenCandidateFallsBackToGenericCounterparts()
+    {
+        var candidates = Candidates("Eva Klein");
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(BflEffectiveSimulation.Of(new() { Mode = BflSimulationMode.SINGLE_PERSON }, candidates), Is.SameAs(BflEffectiveSimulation.GENERIC));
+            Assert.That(BflEffectiveSimulation.Of(new() { Mode = BflSimulationMode.PRESS_CONFERENCE, People = ["Frank Ott"] }, candidates), Is.SameAs(BflEffectiveSimulation.GENERIC));
+        }
+    }
+
+    [Test]
+    public void TheDossiersAreCountedWithTheCharactersPerTokenOfTheMaterial()
+    {
+        var person = new BflPersonResearch { Name = "Eva Klein" };
+        person.Set(BflPersonResearchStage.PROFILE, new BflResearch { Text = new string('a', 4_000), CreatedAtUtc = CREATED_AT_UTC });
+        person.Set(BflPersonResearchStage.POSITIONS, new BflResearch { Text = $"  {new string('b', 3_999)}\n", CreatedAtUtc = CREATED_AT_UTC });
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(BflSimulationBudget.DossierTokens([person]), Is.EqualTo(2_000));
+            Assert.That(BflSimulationBudget.RequiredTokens([person]), Is.EqualTo(BflModelRequirements.MINIMUM_CONTEXT_TOKENS + 2_000));
+        }
+    }
+
+    [Test]
+    public void AKnownWindowWhichIsTooSmallRefusesAndAnUnknownOneWarns()
+    {
+        var person = new BflPersonResearch { Name = "Eva Klein" };
+        person.Set(BflPersonResearchStage.POSITIONS, new BflResearch { Text = new string('a', 40_000), CreatedAtUtc = CREATED_AT_UTC });
+        var simulation = new BflEffectiveSimulation(BflSimulationMode.SINGLE_PERSON, [person]);
+        var required = BflSimulationBudget.RequiredTokens([person]);
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(BflSimulationBudget.Check(simulation, ContextWindow.Of(required - 1)), Is.EqualTo(BflSimulationFit.TOO_SMALL));
+            Assert.That(BflSimulationBudget.Check(simulation, ContextWindow.Of(required)), Is.EqualTo(BflSimulationFit.FITS));
+            Assert.That(BflSimulationBudget.Check(simulation, ContextWindow.UNKNOWN), Is.EqualTo(BflSimulationFit.UNKNOWN_CONTEXT));
+            Assert.That(BflSimulationBudget.Check(BflEffectiveSimulation.GENERIC, ContextWindow.Of(8_192)), Is.EqualTo(BflSimulationFit.FITS), "Generic counterparts need no room for dossiers.");
+            Assert.That(BflSimulationBudget.Check(BflEffectiveSimulation.GENERIC, ContextWindow.UNKNOWN), Is.EqualTo(BflSimulationFit.FITS));
+        }
+    }
+
+    private static List<BflPersonResearch> Candidates(params string[] names)
+    {
+        var forms = Forms();
+        return [.. BflSimulationCandidates.Of(forms, Topics(forms, names), [.. names.Select(name => Person(forms, name, BflPersonResearchStage.All))])];
+    }
+
+    private static BflPersonResearch Person(IReadOnlyDictionary<BflStep, BflStepFormData> forms, string name, IEnumerable<BflPersonResearchStage> stages, string? positionsText = null)
+    {
+        var person = new BflPersonResearch { Name = name };
+        foreach (var stage in stages)
+            person.Set(stage, BflResearch.Of(stage is BflPersonResearchStage.POSITIONS && positionsText is not null ? positionsText : $"Text {stage}", [], [], BflPromptComposer.PublicDetailsOf(forms), CREATED_AT_UTC));
+
+        return person;
+    }
+
+    private static Dictionary<BflResearchTopic, BflResearch> Topics(IReadOnlyDictionary<BflStep, BflStepFormData> forms, params string[] names)
+    {
+        var list = BflResearch.Of(string.Join("\n\n", names.Select(name => $"### {name}")), [], [], BflPromptComposer.PublicDetailsOf(forms), CREATED_AT_UTC);
+        list.Participants = [.. BflParticipant.ListIn(list.Text)];
+        return new() { [BflResearchTopic.PARTICIPANTS] = list };
+    }
+
+    private static Dictionary<BflStep, BflStepFormData> Forms()
+    {
+        var forms = BflStep.All.ToDictionary(step => step, _ => new BflStepFormData());
+        forms[BflStep.FRAMEWORK].Set(BflFieldCatalog.FORMAT, "Podium");
+        forms[BflStep.FRAMEWORK].Set(BflFieldCatalog.EVENT_TOPIC, "Klimapolitik");
+        return forms;
+    }
+}
\ No newline at end of file
diff --git a/app/Tests/BeyondFactsLab/BflStalenessTests.cs b/app/Tests/BeyondFactsLab/BflStalenessTests.cs
index 8f427aa0c..725c25854 100644
--- a/app/Tests/BeyondFactsLab/BflStalenessTests.cs
+++ b/app/Tests/BeyondFactsLab/BflStalenessTests.cs
@@ -213,6 +213,46 @@ public sealed class BflStalenessTests
         Assert.That(BflStaleness.FingerprintOf(first), Is.EqualTo(BflStaleness.FingerprintOf(second)));
     }
 
+    [Test]
+    public void WithGenericCounterpartsTheFingerprintStaysAsItWasBeforeTheSimulation()
+    {
+        var withoutSimulation = new BflStepFormData();
+        withoutSimulation.Set(BflFieldCatalog.TEST_NOTES, "Text");
+        var generic = new BflStepFormData { Simulation = new() { Mode = BflSimulationMode.GENERIC, People = ["Eva Klein"] } };
+        generic.Set(BflFieldCatalog.TEST_NOTES, "Text");
+
+        // How the lab computed the fingerprint of this form before it simulated people:
+        var before = Convert.ToHexStringLower(SHA256.HashData(Encoding.UTF8.GetBytes($"{BflFieldCatalog.TEST_NOTES}\0Text\0")));
+
+        using (Assert.EnterMultipleScope())
+        {
+            Assert.That(BflStaleness.FingerprintOf(withoutSimulation), Is.EqualTo(before));
+            Assert.That(BflStaleness.FingerprintOf(generic), Is.EqualTo(before));
+        }
+    }
+
+    [Test]
+    public void TheFingerprintCountsTheModeAndThePeopleOfTheSimulation()
+    {
+        var empty = new BflStepFormData();
+        var single = new BflStepFormData { Simulation = new() { Mode = BflSimulationMode.SINGLE_PERSON, People = ["Eva Klein"] } };
+        var panel = new BflStepFormData { Simulation = new() { Mode = BflSimulationMode.PANEL_DISCUSSION, People = ["Eva Klein"] } };
+        var otherPerson = new BflStepFormData { Simulation = new() { Mode = BflSimulationMode.SINGLE_PERSON, People = ["Frank Ott"] } };
+
+        var fingerprints = new[] { empty, single, panel, otherPerson }.Select(BflStaleness.FingerprintOf).ToList();
+
+        Assert.That(fingerprints, Is.Unique);
+    }
+
+    [Test]
+    public void TheOrderAndTheSpellingOfTheSimulatedPeopleIsNoChange()
+    {
+        var first = new BflStepFormData { Simulation = new() { Mode = BflSimulationMode.PANEL_DISCUSSION, People = ["Eva Klein", "Frank Ott"] } };
+        var second = new BflStepFormData { Simulation = new() { Mode = BflSimulationMode.PANEL_DISCUSSION, People = ["frank  ott", "Eva Klein"] } };
+
+        Assert.That(BflStaleness.FingerprintOf(first), Is.EqualTo(BflStaleness.FingerprintOf(second)));
+    }
+
     [Test]
     public void AChangedCardSortWeighsLikeChangedDetails()
     {