Surface NER routing provenance (ModelOrigin, NerModelsInvoked) through the pipeline and WPF harness so English/Tamil routing is observable during POC validation. Consolidate docs into solution-guide and add NER logs, topic filtering, and batch UI fixes in the test harness.

tests/PiiRedaction.Core.Tests/Detection/OnnxNerPiiDetectorTests.cs

@@ -46,6 +46,36 @@ public sealed class OnnxNerPiiDetectorTests
         action.Should().Throw<ArgumentException>();
     }
 
+    [Test]
+    public void Detect_ModelAvailable_RecordsInvokedModels()
+    {
+        var runner = new FakeOnnxNerModelRunner
+        {
+            IsModelAvailable = true,
+            InvokedModelsToReturn = [NerModelOrigin.English, NerModelOrigin.Tamil]
+        };
+
+        var detector = new OnnxNerPiiDetector(runner);
+        detector.Detect("Mixed prompt");
+
+        detector.LastInvokedModels.Should().Equal(NerModelOrigin.English, NerModelOrigin.Tamil);
+    }
+
+    [Test]
+    public void Detect_ModelUnavailable_ClearsInvokedModels()
+    {
+        var runner = new FakeOnnxNerModelRunner
+        {
+            IsModelAvailable = false,
+            InvokedModelsToReturn = [NerModelOrigin.English]
+        };
+
+        var detector = new OnnxNerPiiDetector(runner);
+        detector.Detect("Any text");
+
+        detector.LastInvokedModels.Should().BeEmpty();
+    }
+
     private static OnnxNerPiiDetector CreateDetector(bool modelAvailable)
     {
         var runner = new FakeOnnxNerModelRunner { IsModelAvailable = modelAvailable };

tests/PiiRedaction.Core.Tests/Integration/RealTamilPipelineTests.cs

@@ -32,7 +32,32 @@ public sealed class RealTamilPipelineTests : RealRoutingNerModelFixture
         result.SanitizedPrompt.Should().Contain("<PERSON_1>");
         result.SanitizedPrompt.Should().NotContain("ராஜேஷ்");
         result.DetectedEntities.Should().Contain(entity =>
-            entity.Type == PiiEntityType.Person && entity.Source == PiiDetectionSource.Ner);
+            entity.Type == PiiEntityType.Person
+            && entity.Source == PiiDetectionSource.Ner
+            && entity.ModelOrigin == NerModelOrigin.Tamil);
+        result.NerModelsInvoked.Should().Equal(NerModelOrigin.Tamil);
+    }
+
+    [Test]
+    public void Sanitize_TanglishCustomer_InvokesEnglishNerOnly()
+    {
+        const string prompt = "Customer Senthil phone 9876543210 reported a failed UPI transfer.";
+
+        var result = _sanitizer.Sanitize(new SanitizationRequest(prompt));
+
+        result.NerModelsInvoked.Should().Equal(NerModelOrigin.English);
+        result.DetectedEntities.Should().Contain(entity =>
+            entity.Type == PiiEntityType.Person && entity.ModelOrigin == NerModelOrigin.English);
+    }
+
+    [Test]
+    public void Sanitize_MixedTamilEnglish_InvokesBothNerModels()
+    {
+        const string prompt = "வாடிக்கையாளர் Ravi Kumar phone 9876543210 disputed the charge.";
+
+        var result = _sanitizer.Sanitize(new SanitizationRequest(prompt));
+
+        result.NerModelsInvoked.Should().Equal(NerModelOrigin.English, NerModelOrigin.Tamil);
     }
 
     [Test]

tests/PiiRedaction.Core.Tests/TestSupport/FakeOnnxNerModelRunner.cs

@@ -9,11 +9,13 @@ public sealed class FakeOnnxNerModelRunner : IOnnxNerModelRunner
 
     public IReadOnlyList<PiiEntity> EntitiesToReturn { get; set; } = [];
 
+    public IReadOnlyList<NerModelOrigin> InvokedModelsToReturn { get; set; } = [NerModelOrigin.English];
+
     public string? LastPredictedText { get; private set; }
 
-    public IReadOnlyList<PiiEntity> PredictEntities(string text)
+    public NerPredictionResult PredictEntities(string text)
     {
         LastPredictedText = text;
-        return EntitiesToReturn;
+        return new NerPredictionResult(EntitiesToReturn, InvokedModelsToReturn);
     }
 }

tests/PiiRedaction.Core.Tests/TestSupport/ProductionPipelineFactory.cs

@@ -1,3 +1,4 @@
+using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 using PiiRedaction.Core.Abstractions;
 using PiiRedaction.Core.Configuration;
@@ -20,7 +21,8 @@ public static class ProductionPipelineFactory
         CreateWithRealModel(new RoutingOnnxNerModelRunner(
             englishRunner,
             tamilRunner,
-            options ?? Options.Create(new PiiRedactionOptions { EnableTamilNer = true })));
+            options ?? Options.Create(new PiiRedactionOptions { EnableTamilNer = true }),
+            NullLogger<RoutingOnnxNerModelRunner>.Instance));
 
     public static IPiiDetector CreateCompositeDetector(IOnnxNerModelRunner runner) =>
         new CompositePiiDetector(