diff --git a/app/MindWork AI Studio/Components/DataSourceSelection.razor.cs b/app/MindWork AI Studio/Components/DataSourceSelection.razor.cs
index 170d6a0b..839a4850 100644
--- a/app/MindWork AI Studio/Components/DataSourceSelection.razor.cs	
+++ b/app/MindWork AI Studio/Components/DataSourceSelection.razor.cs	
@@ -246,7 +246,7 @@ public partial class DataSourceSelection : MSGComponentBase
         // that field holds what was usable the last time we looked, so a source filtered out once
         // would never come back, while the RAG process keeps reading it from the preselection.
         //
-        var sources = await this.DataSourceService.GetDataSources(this.LLMProvider, this.DataSourceOptions, this.GetDataSourcesFromConfiguredIds());
+        var sources = await this.DataSourceService.GetDataSources(this.LLMProvider, this.DataSourceOptions, DataSourceRetrievalMode.EVERY_MESSAGE, this.GetDataSourcesFromConfiguredIds());
         if (generation != this.loadAndApplyFiltersGeneration)
             return;
 
diff --git a/app/MindWork AI Studio/Settings/DataModel/DataSourceRetrievalMode.cs b/app/MindWork AI Studio/Settings/DataModel/DataSourceRetrievalMode.cs
new file mode 100644
index 00000000..8377aed4
--- /dev/null
+++ b/app/MindWork AI Studio/Settings/DataModel/DataSourceRetrievalMode.cs	
@@ -0,0 +1,21 @@
+namespace AIStudio.Settings.DataModel;
+
+/// <summary>
+/// How the data sources of a chat are searched.
+/// </summary>
+public enum DataSourceRetrievalMode
+{
+    /// <summary>
+    /// The model searches the data sources itself, through the tool semantic_search, whenever a
+    /// question calls for it. No agent takes part: the chat model picks the data sources and
+    /// judges what it found.
+    /// </summary>
+    SEMANTIC_SEARCH,
+
+    /// <summary>
+    /// AI Studio searches the data sources with every message, before the model answers. This is
+    /// the classic RAG process, with its agents for selecting data sources and for validating what
+    /// was found.
+    /// </summary>
+    EVERY_MESSAGE,
+}
\ No newline at end of file
diff --git a/app/MindWork AI Studio/Tools/RAG/RAGProcesses/AISrcSelWithRetCtxVal.cs b/app/MindWork AI Studio/Tools/RAG/RAGProcesses/AISrcSelWithRetCtxVal.cs
index 5bfaebc9..286ab29e 100644
--- a/app/MindWork AI Studio/Tools/RAG/RAGProcesses/AISrcSelWithRetCtxVal.cs	
+++ b/app/MindWork AI Studio/Tools/RAG/RAGProcesses/AISrcSelWithRetCtxVal.cs	
@@ -94,7 +94,7 @@ public sealed class AISrcSelWithRetCtxVal : IRagProcess
             // data sources changed its security requirements.
             //
             List<IDataSource> preselectedDataSources = chatThread.DataSourceOptions.PreselectedDataSourceIds.Select(id => settings.ConfigurationData.DataSources.FirstOrDefault(ds => ds.Id == id)).Where(ds => ds is not null).ToList()!;
-            var dataSources = await dataSourceService.GetDataSources(provider, chatThread.DataSourceOptions, preselectedDataSources);
+            var dataSources = await dataSourceService.GetDataSources(provider, chatThread.DataSourceOptions, DataSourceRetrievalMode.EVERY_MESSAGE, preselectedDataSources);
             var selectedDataSources = dataSources.SelectedDataSources;
             
             //
diff --git a/app/MindWork AI Studio/Tools/Services/DataSourceService.cs b/app/MindWork AI Studio/Tools/Services/DataSourceService.cs
index ce18b3b6..c74f1d50 100644
--- a/app/MindWork AI Studio/Tools/Services/DataSourceService.cs	
+++ b/app/MindWork AI Studio/Tools/Services/DataSourceService.cs	
@@ -39,9 +39,10 @@ public sealed class DataSourceService
     /// </summary>
     /// <param name="selectedLLMProvider">The selected LLM provider.</param>
     /// <param name="dataSourceOptions">The active data source options, which determine which agent providers participate.</param>
+    /// <param name="retrievalMode">How the data sources are searched in effect, which decides whether any agent participates at all.</param>
     /// <param name="previousSelectedDataSources">The data sources selected before.</param>
     /// <returns>The allowed data sources and the data sources selected before -- when they are still allowed.</returns>
-    public async Task<AllowedSelectedDataSources> GetDataSources(AIStudio.Settings.Provider selectedLLMProvider, DataSourceOptions dataSourceOptions, IReadOnlyCollection<IDataSource>? previousSelectedDataSources = null)
+    public async Task<AllowedSelectedDataSources> GetDataSources(AIStudio.Settings.Provider selectedLLMProvider, DataSourceOptions dataSourceOptions, DataSourceRetrievalMode retrievalMode, IReadOnlyCollection<IDataSource>? previousSelectedDataSources = null)
     {
         //
         // Case: Somehow the selected LLM provider was not set. The default provider
@@ -55,7 +56,7 @@ public sealed class DataSourceService
         }
         
         var usingTrustedProvider = selectedLLMProvider.IsTrustedForDataSourceSecurityChecks(this.settingsManager);
-        var participatingProviders = this.GetParticipatingProviders(selectedLLMProvider.Id, dataSourceOptions,
+        var participatingProviders = this.GetParticipatingProviders(selectedLLMProvider.Id, dataSourceOptions, retrievalMode,
             new("chat provider", usingTrustedProvider, selectedLLMProvider.GetConfidenceLevel(this.settingsManager)));
         return await this.GetDataSources(usingTrustedProvider, participatingProviders, previousSelectedDataSources);
     }
@@ -67,9 +68,10 @@ public sealed class DataSourceService
     /// </summary>
     /// <param name="selectedLLMProvider">The selected LLM provider.</param>
     /// <param name="dataSourceOptions">The active data source options, which determine which agent providers participate.</param>
+    /// <param name="retrievalMode">How the data sources are searched in effect, which decides whether any agent participates at all.</param>
     /// <param name="requestedDataSources">The data sources to check.</param>
     /// <returns>The requested data sources that are allowed for the provider.</returns>
-    public async Task<IReadOnlyList<IDataSource>> GetAllowedDataSources(AIStudio.Settings.Provider selectedLLMProvider, DataSourceOptions dataSourceOptions, IReadOnlyCollection<IDataSource> requestedDataSources)
+    public async Task<IReadOnlyList<IDataSource>> GetAllowedDataSources(AIStudio.Settings.Provider selectedLLMProvider, DataSourceOptions dataSourceOptions, DataSourceRetrievalMode retrievalMode, IReadOnlyCollection<IDataSource> requestedDataSources)
     {
         if (selectedLLMProvider == Settings.Provider.NONE)
         {
@@ -78,7 +80,7 @@ public sealed class DataSourceService
         }
 
         var usingTrustedProvider = selectedLLMProvider.IsTrustedForDataSourceSecurityChecks(this.settingsManager);
-        var participatingProviders = this.GetParticipatingProviders(selectedLLMProvider.Id, dataSourceOptions,
+        var participatingProviders = this.GetParticipatingProviders(selectedLLMProvider.Id, dataSourceOptions, retrievalMode,
             new("chat provider", usingTrustedProvider, selectedLLMProvider.GetConfidenceLevel(this.settingsManager)));
         var allowedDataSources = await this.GetAllowedDataSources(usingTrustedProvider, participatingProviders, requestedDataSources);
 
@@ -98,9 +100,10 @@ public sealed class DataSourceService
     /// </summary>
     /// <param name="selectedLLMProvider">The selected LLM provider.</param>
     /// <param name="dataSourceOptions">The active data source options, which determine which agent providers participate.</param>
+    /// <param name="retrievalMode">How the data sources are searched in effect, which decides whether any agent participates at all.</param>
     /// <param name="previousSelectedDataSources">The data sources selected before.</param>
     /// <returns>The allowed data sources and the data sources selected before -- when they are still allowed.</returns>
-    public async Task<AllowedSelectedDataSources> GetDataSources(IProvider selectedLLMProvider, DataSourceOptions dataSourceOptions, IReadOnlyCollection<IDataSource>? previousSelectedDataSources = null)
+    public async Task<AllowedSelectedDataSources> GetDataSources(IProvider selectedLLMProvider, DataSourceOptions dataSourceOptions, DataSourceRetrievalMode retrievalMode, IReadOnlyCollection<IDataSource>? previousSelectedDataSources = null)
     {
         //
         // Case: Somehow the selected LLM provider was not set. The default provider
@@ -114,24 +117,49 @@ public sealed class DataSourceService
         }
         
         var usingTrustedProvider = selectedLLMProvider.IsTrustedForDataSourceSecurityChecks(this.settingsManager);
-        var participatingProviders = this.GetParticipatingProviders(selectedLLMProvider.ConfiguredProviderId, dataSourceOptions,
+        var participatingProviders = this.GetParticipatingProviders(selectedLLMProvider.ConfiguredProviderId, dataSourceOptions, retrievalMode,
             new("chat provider", usingTrustedProvider, selectedLLMProvider.GetConfidenceLevel(this.settingsManager)));
         return await this.GetDataSources(usingTrustedProvider, participatingProviders, previousSelectedDataSources);
     }
     
-    private IReadOnlyList<ParticipatingProvider> GetParticipatingProviders(string currentProviderId, DataSourceOptions dataSourceOptions, ParticipatingProvider currentProvider)
+    private IReadOnlyList<ParticipatingProvider> GetParticipatingProviders(string currentProviderId, DataSourceOptions dataSourceOptions, DataSourceRetrievalMode retrievalMode, ParticipatingProvider currentProvider)
     {
         var providers = new List<ParticipatingProvider> { currentProvider };
-
-        if (dataSourceOptions.AutomaticDataSourceSelection)
-            this.AddAgentProvider(providers, Components.AGENT_DATA_SOURCE_SELECTION, currentProviderId, "data source selection agent");
-
-        if (dataSourceOptions.AutomaticValidation && this.settingsManager.ConfigurationData.AgentRetrievalContextValidation.EnableRetrievalContextValidation)
-            this.AddAgentProvider(providers, Components.AGENT_RETRIEVAL_CONTEXT_VALIDATION, currentProviderId, "retrieval context validation agent");
+        var retrievalContextValidationEnabled = this.settingsManager.ConfigurationData.AgentRetrievalContextValidation.EnableRetrievalContextValidation;
+        foreach (var (component, role) in GetParticipatingAgents(dataSourceOptions, retrievalMode, retrievalContextValidationEnabled))
+            this.AddAgentProvider(providers, component, currentProviderId, role);
 
         return providers;
     }
 
+    /// <summary>
+    /// Which agents get to see the data of the data sources, besides the chat provider.
+    /// </summary>
+    /// <remarks>
+    /// Only the classic RAG process runs agents. With Semantic Search, the chat model picks the
+    /// data sources and judges what it found itself, so the data reaches no other provider.
+    /// Counting the providers of the agents there would hold back data sources which the chat
+    /// provider alone may use.
+    /// </remarks>
+    /// <param name="dataSourceOptions">The active data source options.</param>
+    /// <param name="retrievalMode">How the data sources are searched in effect.</param>
+    /// <param name="retrievalContextValidationEnabled">Whether the validation of retrieval contexts is enabled in the settings.</param>
+    /// <returns>The component of each participating agent, together with its role for the log.</returns>
+    internal static IReadOnlyList<(Components Component, string Role)> GetParticipatingAgents(DataSourceOptions dataSourceOptions, DataSourceRetrievalMode retrievalMode, bool retrievalContextValidationEnabled)
+    {
+        if (retrievalMode is DataSourceRetrievalMode.SEMANTIC_SEARCH)
+            return [];
+
+        var agents = new List<(Components Component, string Role)>(2);
+        if (dataSourceOptions.AutomaticDataSourceSelection)
+            agents.Add((Components.AGENT_DATA_SOURCE_SELECTION, "data source selection agent"));
+
+        if (dataSourceOptions.AutomaticValidation && retrievalContextValidationEnabled)
+            agents.Add((Components.AGENT_RETRIEVAL_CONTEXT_VALIDATION, "retrieval context validation agent"));
+
+        return agents;
+    }
+
     private void AddAgentProvider(List<ParticipatingProvider> providers, Components component, string currentProviderId, string role)
     {
         var provider = this.settingsManager.GetPreselectedProvider(component, currentProviderId, true);
diff --git a/app/MindWork AI Studio/Tools/Services/DirectChatService.cs b/app/MindWork AI Studio/Tools/Services/DirectChatService.cs
index 0bbd5ffe..dfb50c27 100644
--- a/app/MindWork AI Studio/Tools/Services/DirectChatService.cs	
+++ b/app/MindWork AI Studio/Tools/Services/DirectChatService.cs	
@@ -274,7 +274,7 @@ public sealed class DirectChatService(SettingsManager settingsManager, DataSourc
             // decide which agent providers take part, and an agent with too little confidence makes
             // a data source unavailable.
             //
-            availableDataSources = await dataSourceService.GetAllowedDataSources(provider, chosenOptions, requestedDataSources);
+            availableDataSources = await dataSourceService.GetAllowedDataSources(provider, chosenOptions, DataSourceRetrievalMode.EVERY_MESSAGE, requestedDataSources);
         }
         catch (Exception exception)
         {
diff --git a/app/Tests/Tools/DataSourceParticipatingAgentsTests.cs b/app/Tests/Tools/DataSourceParticipatingAgentsTests.cs
new file mode 100644
index 00000000..e66a28ea
--- /dev/null
+++ b/app/Tests/Tools/DataSourceParticipatingAgentsTests.cs
@@ -0,0 +1,51 @@
+using AIStudio.Settings.DataModel;
+using AIStudio.Tools.Services;
+
+namespace AIStudio.Tests.Tools;
+
+/// <summary>
+/// Checks which agents count as seeing the data of the data sources.
+/// </summary>
+/// <remarks>
+/// Every provider which sees the data must be trusted enough for every data source it sees. That
+/// cuts both ways: leaving out an agent which does run would send data to a provider trusted too
+/// little, while counting an agent which does not run holds back data sources for no reason. The
+/// classic RAG process runs its agents; Semantic Search runs none, since the chat model picks the
+/// data sources and judges the passages itself.
+/// </remarks>
+[TestFixture]
+public sealed class DataSourceParticipatingAgentsTests
+{
+    [Test]
+    public void SemanticSearchRunsNoAgent()
+    {
+        var agents = DataSourceService.GetParticipatingAgents(Options(automaticSelection: true, automaticValidation: true), DataSourceRetrievalMode.SEMANTIC_SEARCH, retrievalContextValidationEnabled: true);
+
+        Assert.That(agents, Is.Empty, "The chat provider alone sees the data, so its trust alone decides which data sources it may search.");
+    }
+
+    [Test]
+    public void TheClassicRAGProcessCountsTheAgentsItRuns()
+    {
+        var agents = DataSourceService.GetParticipatingAgents(Options(automaticSelection: true, automaticValidation: true), DataSourceRetrievalMode.EVERY_MESSAGE, retrievalContextValidationEnabled: true);
+
+        Assert.That(agents.Select(agent => agent.Component), Is.EqualTo(new[] { AIStudio.Tools.Components.AGENT_DATA_SOURCE_SELECTION, AIStudio.Tools.Components.AGENT_RETRIEVAL_CONTEXT_VALIDATION }));
+    }
+
+    [Test]
+    public void TheClassicRAGProcessCountsNoAgentItDoesNotRun()
+    {
+        Assert.Multiple(() =>
+        {
+            Assert.That(DataSourceService.GetParticipatingAgents(Options(automaticSelection: false, automaticValidation: false), DataSourceRetrievalMode.EVERY_MESSAGE, retrievalContextValidationEnabled: true), Is.Empty);
+            Assert.That(DataSourceService.GetParticipatingAgents(Options(automaticSelection: false, automaticValidation: true), DataSourceRetrievalMode.EVERY_MESSAGE, retrievalContextValidationEnabled: false), Is.Empty, "The validation of this chat is on, but the settings switch it off everywhere.");
+        });
+    }
+
+    private static DataSourceOptions Options(bool automaticSelection, bool automaticValidation) => new()
+    {
+        DisableDataSources = false,
+        AutomaticDataSourceSelection = automaticSelection,
+        AutomaticValidation = automaticValidation,
+    };
+}
\ No newline at end of file