diff --git a/java/ql/experimental/adaptivethreatmodeling/src/ExtractNegativeExamples.ql b/java/ql/experimental/adaptivethreatmodeling/src/ExtractNegativeExamples.ql
index 379eb113e3e..e27a565d173 100644
--- a/java/ql/experimental/adaptivethreatmodeling/src/ExtractNegativeExamples.ql
+++ b/java/ql/experimental/adaptivethreatmodeling/src/ExtractNegativeExamples.ql
@@ -35,5 +35,18 @@ where
   // Exclude endpoints that have contradictory endpoint characteristics, because we only want examples we're highly
   // certain about in the prompt.
   not EndpointCharacteristics::erroneousEndpoints(endpoint, _, _, _, _) and
+  // It's valid for a node to satisfy the logic for both `isSink` and `isSanitizer`, but in that case it will be
+  // treated by the actual query as a sanitizer, since the final logic is something like
+  // `isSink(n) and not isSanitizer(n)`. We don't want to include such nodes as negative examples in the prompt, because
+  // they're ambiguous and might confuse the model, so we explicitly exclude all known sinks from the negative examples.
+  not exists(
+    EndpointCharacteristics::EndpointCharacteristic characteristic2, float confidence2,
+    EndpointType positiveType
+  |
+    characteristic2.appliesToEndpoint(endpoint) and
+    confidence2 >= characteristic2.maximalConfidence() and
+    not positiveType instanceof NegativeType and
+    characteristic2.hasImplications(positiveType, true, confidence2)
+  ) and
   endpoint = getSampleFromSampleRate(0.01)
 select endpoint, "Non-sink of type " + characteristic + " with confidence " + confidence.toString()
diff --git a/java/ql/experimental/adaptivethreatmodeling/src/ExtractPositiveExamples.ql b/java/ql/experimental/adaptivethreatmodeling/src/ExtractPositiveExamples.ql
index 7319c68e11d..b790a417caf 100644
--- a/java/ql/experimental/adaptivethreatmodeling/src/ExtractPositiveExamples.ql
+++ b/java/ql/experimental/adaptivethreatmodeling/src/ExtractPositiveExamples.ql
@@ -26,5 +26,9 @@ where
   config.isKnownSink(sink) and
   // If there are _any_ erroneous endpoints, return nothing. This will prevent us from accidentally running this query
   // when there's a codex-generated data extension file in `java/ql/lib/ext`.
-  not EndpointCharacteristics::erroneousEndpoints(_, _, _, _, _)
+  not EndpointCharacteristics::erroneousEndpoints(_, _, _, _, _) and
+  // It's valid for a node to satisfy the logic for both `isSink` and `isSanitizer`, but in that case it will be
+  // treated by the actual query as a sanitizer, since the final logic is something like
+  // `isSink(n) and not isSanitizer(n)`. We don't want to include such nodes as positive examples in the prompt.
+  not config.isSanitizer(sink)
 select sink, config.getASinkEndpointType().getDescription()