diff --git a/braintrust-sdk/src/main/java/dev/braintrust/eval/Classification.java b/braintrust-sdk/src/main/java/dev/braintrust/eval/Classification.java
new file mode 100644
index 00000000..7d3684a6
--- /dev/null
+++ b/braintrust-sdk/src/main/java/dev/braintrust/eval/Classification.java
@@ -0,0 +1,37 @@
+package dev.braintrust.eval;
+
+import java.util.Map;
+import javax.annotation.Nullable;
+
+/**
+ * A single structured classification produced by a {@link Classifier}.
+ *
+ * <p>Unlike a {@link Score} (numeric 0-1), a Classification carries a stable id, an optional
+ * display label, and optional metadata. The {@code name} acts as the grouping key in the aggregated
+ * result map; when {@code name} is {@code null} or blank, the owning classifier's resolved name is
+ * used instead.
+ *
+ * @param name optional grouping key; defaults to the owning classifier's resolved name when null or
+ *     blank
+ * @param id stable identifier for the classification (required)
+ * @param label optional display label
+ * @param metadata optional arbitrary metadata
+ */
+public record Classification(
+        @Nullable String name,
+        String id,
+        @Nullable String label,
+        @Nullable Map<String, Object> metadata) {
+
+    public static Classification of(String id) {
+        return new Classification(null, id, null, null);
+    }
+
+    public static Classification of(String id, String label) {
+        return new Classification(null, id, label, null);
+    }
+
+    public static Classification of(String name, String id, String label) {
+        return new Classification(name, id, label, null);
+    }
+}
diff --git a/braintrust-sdk/src/main/java/dev/braintrust/eval/Classifier.java b/braintrust-sdk/src/main/java/dev/braintrust/eval/Classifier.java
new file mode 100644
index 00000000..e37b3e3e
--- /dev/null
+++ b/braintrust-sdk/src/main/java/dev/braintrust/eval/Classifier.java
@@ -0,0 +1,98 @@
+package dev.braintrust.eval;
+
+import java.util.List;
+import java.util.function.Function;
+
+/**
+ * A classifier categorizes and labels eval outputs, producing zero or more structured {@link
+ * Classification} items.
+ *
+ * <p>Classifiers run independently from {@link Scorer}s. Each Classifier exposes a name (used as
+ * the span name and as the default grouping key for classifications whose own {@code name} is
+ * blank).
+ *
+ * @param <INPUT> type of the input data
+ * @param <OUTPUT> type of the output data
+ */
+public interface Classifier<INPUT, OUTPUT> {
+    String INVALID_CLASSIFICATION_MESSAGE =
+            "When returning structured classifier results, each classification must be a non-empty"
+                    + " object.";
+
+    String getName();
+
+    /**
+     * Classifies the result of a successful task execution.
+     *
+     * @param taskResult the task output and originating dataset case
+     * @return zero or more classifications. An empty list means "no classifications for this case".
+     */
+    List<Classification> classify(TaskResult<INPUT, OUTPUT> taskResult);
+
+    /**
+     * Creates a classifier from a function that returns a (possibly empty or null) list of
+     * classifications.
+     *
+     * <p>A {@code null} return value is treated as no classifications. Each returned {@link
+     * Classification} must have a non-blank {@code id}; otherwise the classifier throws an
+     * exception (which the eval runner records but does not abort on).
+     */
+    static <INPUT, OUTPUT> Classifier<INPUT, OUTPUT> of(
+            String classifierName,
+            Function<TaskResult<INPUT, OUTPUT>, List<Classification>> classifierFn) {
+        return new Classifier<>() {
+            @Override
+            public String getName() {
+                return classifierName;
+            }
+
+            @Override
+            public List<Classification> classify(TaskResult<INPUT, OUTPUT> taskResult) {
+                var result = classifierFn.apply(taskResult);
+                if (result == null) {
+                    return List.of();
+                }
+                for (var item : result) {
+                    validate(item);
+                }
+                return result;
+            }
+        };
+    }
+
+    /**
+     * Creates a classifier from a function that returns a single classification.
+     *
+     * <p>A {@code null} return value is treated as no classifications.
+     */
+    static <INPUT, OUTPUT> Classifier<INPUT, OUTPUT> single(
+            String classifierName,
+            Function<TaskResult<INPUT, OUTPUT>, Classification> classifierFn) {
+        return new Classifier<>() {
+            @Override
+            public String getName() {
+                return classifierName;
+            }
+
+            @Override
+            public List<Classification> classify(TaskResult<INPUT, OUTPUT> taskResult) {
+                var item = classifierFn.apply(taskResult);
+                if (item == null) {
+                    return List.of();
+                }
+                validate(item);
+                return List.of(item);
+            }
+        };
+    }
+
+    /**
+     * Validates a single classification: it must have a non-blank id. Throws with the spec-mandated
+     * wording on failure.
+     */
+    private static void validate(Classification item) {
+        if (item == null || item.id() == null || item.id().isBlank()) {
+            throw new IllegalArgumentException(INVALID_CLASSIFICATION_MESSAGE + " Got: " + item);
+        }
+    }
+}
diff --git a/braintrust-sdk/src/main/java/dev/braintrust/eval/Eval.java b/braintrust-sdk/src/main/java/dev/braintrust/eval/Eval.java
index ee814baf..a9c3d06b 100644
--- a/braintrust-sdk/src/main/java/dev/braintrust/eval/Eval.java
+++ b/braintrust-sdk/src/main/java/dev/braintrust/eval/Eval.java
@@ -42,6 +42,7 @@ public final class Eval<INPUT, OUTPUT> {
     private final @Nonnull Dataset<INPUT, OUTPUT> dataset;
     private final @Nonnull Task<INPUT, OUTPUT> task;
     private final @Nonnull List<Scorer<INPUT, OUTPUT>> scorers;
+    private final @Nonnull List<Classifier<INPUT, OUTPUT>> classifiers;
     private final @Nonnull List<String> tags;
     private final @Nonnull Map<String, Object> metadata;
     private final @Nonnull Parameters parameters;
@@ -58,6 +59,7 @@ private Eval(Builder<INPUT, OUTPUT> builder) {
         this.dataset = builder.dataset;
         this.task = Objects.requireNonNull(builder.task);
         this.scorers = List.copyOf(builder.scorers);
+        this.classifiers = List.copyOf(builder.classifiers);
         this.tags = List.copyOf(builder.tags);
         this.metadata = Map.copyOf(builder.metadata);
         this.parameters = builder.buildParameters();
@@ -172,6 +174,42 @@ private void evalOne(String experimentId, DatasetCase<INPUT, OUTPUT> datasetCase
             for (var scorer : scorers) {
                 runScorer(experimentId, rootSpan, scorer, taskResult, trace);
             }
+
+            // run classifiers - one span per classifier. Classifier exceptions are non-fatal:
+            // they are recorded on the classifier span and surfaced in the root span's metadata
+            // under `classifier_errors`, but do not abort the eval or affect other classifiers/
+            // scorers. Classifiers only run when the task succeeded (no scoreForTaskException
+            // analogue).
+            if (!classifiers.isEmpty()) {
+                Map<String, List<Map<String, Object>>> caseClassifications = new LinkedHashMap<>();
+                Map<String, String> classifierErrors = new LinkedHashMap<>();
+                for (int i = 0; i < classifiers.size(); i++) {
+                    var classifier = classifiers.get(i);
+                    var classifierName = classifier.getName();
+                    if (classifierName == null || classifierName.isBlank()) {
+                        classifierName = "classifier_" + i;
+                    }
+                    runClassifier(
+                            experimentId,
+                            classifier,
+                            classifierName,
+                            taskResult,
+                            trace,
+                            caseClassifications,
+                            classifierErrors);
+                }
+                if (!caseClassifications.isEmpty()) {
+                    rootSpan.setAttribute(
+                            "braintrust.classifications", toJson(caseClassifications));
+                }
+                if (!classifierErrors.isEmpty()) {
+                    Map<String, Object> mergedMetadata =
+                            new LinkedHashMap<>(datasetCase.metadata());
+                    mergedMetadata.put("classifier_errors", classifierErrors);
+                    rootSpan.setAttribute(
+                            AttributeKey.stringKey("braintrust.metadata"), toJson(mergedMetadata));
+                }
+            }
         } finally {
             rootSpan.end();
         }
@@ -236,6 +274,84 @@ private void runScoreForTaskException(
         }
     }
 
+    /**
+     * Runs a classifier inside its own span. Exceptions are recorded on the classifier span and
+     * surfaced via {@code classifierErrors}; they do not propagate.
+     */
+    private void runClassifier(
+            String experimentId,
+            Classifier<INPUT, OUTPUT> classifier,
+            String resolvedName,
+            TaskResult<INPUT, OUTPUT> taskResult,
+            BrainstoreTrace trace,
+            Map<String, List<Map<String, Object>>> caseClassifications,
+            Map<String, String> classifierErrors) {
+        var classifierSpan =
+                tracer.spanBuilder(resolvedName)
+                        .setAttribute(PARENT, "experiment_id:" + experimentId)
+                        .startSpan();
+        try (var unused =
+                BraintrustContext.ofExperiment(experimentId, classifierSpan).makeCurrent()) {
+            Map<String, Object> spanAttrs = new LinkedHashMap<>();
+            spanAttrs.put("type", "classifier");
+            spanAttrs.put("name", resolvedName);
+            spanAttrs.put("purpose", "scorer");
+            classifierSpan.setAttribute("braintrust.span_attributes", toJson(spanAttrs));
+
+            List<Classification> classifications;
+            try {
+                if (classifier instanceof TracedClassifier<INPUT, OUTPUT> tracedClassifier) {
+                    classifications = tracedClassifier.classify(taskResult, trace);
+                } else {
+                    classifications = classifier.classify(taskResult);
+                }
+                if (classifications == null) {
+                    classifications = List.of();
+                }
+            } catch (Exception e) {
+                classifierSpan.setStatus(StatusCode.ERROR, e.getMessage());
+                classifierSpan.recordException(e);
+                log.debug("Classifier '{}' threw exception", resolvedName, e);
+                classifierErrors.put(
+                        resolvedName, e.getMessage() == null ? e.toString() : e.getMessage());
+                return;
+            }
+
+            // Group results by resolved item name (item.name, falling back to the classifier
+            // name when blank). Same map is logged to the classifier span and merged into the
+            // per-case aggregate logged on the root span.
+            Map<String, List<Map<String, Object>>> outputByName = new LinkedHashMap<>();
+            for (var item : classifications) {
+                var itemName = item.name();
+                if (itemName == null || itemName.isBlank()) {
+                    itemName = resolvedName;
+                }
+                var itemMap = toClassificationItem(item);
+                outputByName.computeIfAbsent(itemName, k -> new ArrayList<>()).add(itemMap);
+                caseClassifications.computeIfAbsent(itemName, k -> new ArrayList<>()).add(itemMap);
+            }
+            classifierSpan.setAttribute("braintrust.output_json", toJson(outputByName));
+        } finally {
+            classifierSpan.end();
+        }
+    }
+
+    /**
+     * Converts a {@link Classification} to the wire-format {@code ClassificationItem}: drops {@code
+     * name}, includes {@code label} and {@code metadata} only when present.
+     */
+    private static Map<String, Object> toClassificationItem(Classification c) {
+        Map<String, Object> m = new LinkedHashMap<>();
+        m.put("id", c.id());
+        if (c.label() != null) {
+            m.put("label", c.label());
+        }
+        if (c.metadata() != null) {
+            m.put("metadata", c.metadata());
+        }
+        return m;
+    }
+
     /** Validates and records scores on the score span and root span. */
     private void recordScores(
             Span scoreSpan, Span rootSpan, Scorer<INPUT, OUTPUT> scorer, List<Score> scores) {
@@ -276,6 +392,7 @@ public static final class Builder<INPUT, OUTPUT> {
         private @Nullable Tracer tracer = null;
         private @Nullable Task<INPUT, OUTPUT> task;
         private @Nonnull List<Scorer<INPUT, OUTPUT>> scorers = List.of();
+        private @Nonnull List<Classifier<INPUT, OUTPUT>> classifiers = List.of();
         private @Nonnull List<ParameterDef<?>> parameterDefs = List.of();
         private @Nonnull Map<String, Object> parameterValues = Map.of();
         private @Nonnull List<String> tags = List.of();
@@ -291,8 +408,8 @@ public Eval<INPUT, OUTPUT> build() {
             if (projectId == null) {
                 projectId = config.defaultProjectId().orElse(null);
             }
-            if (scorers.isEmpty()) {
-                throw new RuntimeException("must provide at least one scorer");
+            if (scorers.isEmpty() && classifiers.isEmpty()) {
+                throw new RuntimeException("must provide at least one scorer or classifier");
             }
             if (null == apiClient) {
                 apiClient = BraintrustOpenApiClient.of(config);
@@ -380,6 +497,12 @@ public final Builder<INPUT, OUTPUT> scorers(Scorer<INPUT, OUTPUT>... scorers) {
             return this;
         }
 
+        @SafeVarargs
+        public final Builder<INPUT, OUTPUT> classifiers(Classifier<INPUT, OUTPUT>... classifiers) {
+            this.classifiers = List.of(classifiers);
+            return this;
+        }
+
         /** Sets tags for the experiment. */
         public Builder<INPUT, OUTPUT> tags(List<String> tags) {
             this.tags = List.copyOf(tags);
diff --git a/braintrust-sdk/src/main/java/dev/braintrust/eval/TracedClassifier.java b/braintrust-sdk/src/main/java/dev/braintrust/eval/TracedClassifier.java
new file mode 100644
index 00000000..db67d78b
--- /dev/null
+++ b/braintrust-sdk/src/main/java/dev/braintrust/eval/TracedClassifier.java
@@ -0,0 +1,41 @@
+package dev.braintrust.eval;
+
+import dev.braintrust.trace.BrainstoreTrace;
+import java.util.List;
+
+/**
+ * A classifier that receives access to the full distributed trace of the task that was evaluated.
+ *
+ * <p>Implement this interface when your classifier needs to examine intermediate LLM calls, tool
+ * invocations, or other spans produced during task execution — not just the final {@link
+ * TaskResult}.
+ *
+ * @param <INPUT> type of the input data
+ * @param <OUTPUT> type of the output data
+ */
+public interface TracedClassifier<INPUT, OUTPUT> extends Classifier<INPUT, OUTPUT> {
+
+    /**
+     * Classifies the task result using the distributed trace for additional context. Called instead
+     * of {@link Classifier#classify(TaskResult)} when a {@link BrainstoreTrace} is available.
+     *
+     * @param taskResult the task output and originating dataset case
+     * @param trace lazy access to the distributed trace spans for this eval case
+     * @return zero or more classifications
+     */
+    List<Classification> classify(TaskResult<INPUT, OUTPUT> taskResult, BrainstoreTrace trace);
+
+    /**
+     * {@inheritDoc}
+     *
+     * <p>When used inside an {@link Eval}, this overload is never called — {@link
+     * #classify(TaskResult, BrainstoreTrace)} is dispatched instead. This default implementation
+     * throws {@link UnsupportedOperationException} to surface any accidental direct calls.
+     */
+    @Override
+    default List<Classification> classify(TaskResult<INPUT, OUTPUT> taskResult) {
+        throw new UnsupportedOperationException(
+                "traced classifier classify method directly called. This is likely an accident. If"
+                    + " you wish to support this, your implementation must override this method.");
+    }
+}
diff --git a/braintrust-sdk/src/test/java/dev/braintrust/eval/ClassifierEvalTest.java b/braintrust-sdk/src/test/java/dev/braintrust/eval/ClassifierEvalTest.java
new file mode 100644
index 00000000..fb1445c6
--- /dev/null
+++ b/braintrust-sdk/src/test/java/dev/braintrust/eval/ClassifierEvalTest.java
@@ -0,0 +1,304 @@
+package dev.braintrust.eval;
+
+import static dev.braintrust.json.BraintrustJsonMapper.fromJson;
+import static org.junit.jupiter.api.Assertions.*;
+
+import dev.braintrust.TestHarness;
+import io.opentelemetry.api.common.AttributeKey;
+import io.opentelemetry.sdk.trace.data.SpanData;
+import java.util.List;
+import java.util.Map;
+import lombok.SneakyThrows;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+/**
+ * End-to-end tests for the classifier flow on {@link Eval}, modeled on {@link EvalTest}.
+ *
+ * <p>These tests rely on VCR cassettes for new experiment names. Cassettes are regenerated by
+ * running {@code VCR_MODE=record BRAINTRUST_API_KEY=... ./gradlew :braintrust-sdk:test --tests
+ * 'dev.braintrust.eval.ClassifierEvalTest'} (see {@code scripts/re-record-cassettes.sh}).
+ */
+public class ClassifierEvalTest {
+    private TestHarness testHarness;
+
+    @BeforeEach
+    void beforeEach() {
+        testHarness = TestHarness.setup();
+    }
+
+    // ---------------------------------------------------------------------------
+    // Builder validation (no API calls)
+    // ---------------------------------------------------------------------------
+
+    @Test
+    void builderRejectsEmptyScorersAndClassifiers() {
+        var error =
+                assertThrows(
+                        RuntimeException.class,
+                        () ->
+                                testHarness
+                                        .braintrust()
+                                        .<String, String>evalBuilder()
+                                        .name("no-scorers-or-classifiers")
+                                        .cases(DatasetCase.of("hello", null))
+                                        .taskFunction(input -> input)
+                                        .build());
+        assertTrue(
+                error.getMessage().contains("at least one scorer or classifier"),
+                "expected message about scorer-or-classifier requirement, got: "
+                        + error.getMessage());
+    }
+
+    @Test
+    void builderAcceptsClassifiersOnly() {
+        assertDoesNotThrow(
+                () ->
+                        testHarness
+                                .braintrust()
+                                .<String, String>evalBuilder()
+                                .name("classifiers-only-build")
+                                .cases(DatasetCase.of("hello", null))
+                                .taskFunction(input -> input)
+                                .classifiers(
+                                        Classifier.single(
+                                                "category",
+                                                tr ->
+                                                        new Classification(
+                                                                "category",
+                                                                "greeting",
+                                                                null,
+                                                                null)))
+                                .build());
+    }
+
+    @Test
+    void builderAcceptsBothScorersAndClassifiers() {
+        assertDoesNotThrow(
+                () ->
+                        testHarness
+                                .braintrust()
+                                .<String, String>evalBuilder()
+                                .name("scorers-and-classifiers-build")
+                                .cases(DatasetCase.of("hello", "HELLO"))
+                                .taskFunction(String::toUpperCase)
+                                .scorers(Scorer.of("exact", tr -> 1.0))
+                                .classifiers(
+                                        Classifier.single(
+                                                "category",
+                                                tr ->
+                                                        new Classification(
+                                                                "category", "text", null, null)))
+                                .build());
+    }
+
+    // ---------------------------------------------------------------------------
+    // End-to-end span assertions (require VCR cassettes)
+    // ---------------------------------------------------------------------------
+
+    @Test
+    @SneakyThrows
+    void classifierOnlyEvalProducesClassifierSpanAndRootAggregation() {
+        var eval =
+                testHarness
+                        .braintrust()
+                        .<String, String>evalBuilder()
+                        .name("classifier-only-eval")
+                        .cases(DatasetCase.of("hello", null))
+                        .taskFunction(input -> input)
+                        .classifiers(
+                                Classifier.single(
+                                        "category",
+                                        tr ->
+                                                new Classification(
+                                                        "category", "greeting", "Greeting", null)))
+                        .build();
+        eval.run();
+
+        var spans = testHarness.awaitExportedSpans();
+        var classifierSpan = findSpanByName(spans, "category");
+        assertNotNull(classifierSpan, "expected classifier span named 'category'");
+
+        var spanAttrsJson =
+                classifierSpan
+                        .getAttributes()
+                        .get(AttributeKey.stringKey("braintrust.span_attributes"));
+        assertNotNull(spanAttrsJson);
+        var spanAttrs = fromJson(spanAttrsJson, Map.class);
+        assertEquals("classifier", spanAttrs.get("type"));
+        assertEquals("scorer", spanAttrs.get("purpose"));
+        assertEquals("category", spanAttrs.get("name"));
+
+        var outputJson =
+                classifierSpan
+                        .getAttributes()
+                        .get(AttributeKey.stringKey("braintrust.output_json"));
+        assertNotNull(outputJson);
+        var output = fromJson(outputJson, Map.class);
+        @SuppressWarnings("unchecked")
+        var category = (List<Map<String, Object>>) output.get("category");
+        assertEquals(1, category.size());
+        assertEquals("greeting", category.get(0).get("id"));
+        assertEquals("Greeting", category.get(0).get("label"));
+
+        var rootSpan = findRootEvalSpan(spans);
+        assertNotNull(rootSpan);
+        var classificationsJson =
+                rootSpan.getAttributes().get(AttributeKey.stringKey("braintrust.classifications"));
+        assertNotNull(classificationsJson, "root span should carry braintrust.classifications");
+        var classifications = fromJson(classificationsJson, Map.class);
+        assertTrue(classifications.containsKey("category"));
+    }
+
+    @Test
+    @SneakyThrows
+    void scorerAndClassifierBothRun() {
+        var eval =
+                testHarness
+                        .braintrust()
+                        .<String, String>evalBuilder()
+                        .name("scorer-and-classifier-eval")
+                        .cases(DatasetCase.of("hello", "HELLO"))
+                        .taskFunction(String::toUpperCase)
+                        .scorers(
+                                Scorer.of(
+                                        "exact",
+                                        tr ->
+                                                tr.result().equals(tr.datasetCase().expected())
+                                                        ? 1.0
+                                                        : 0.0))
+                        .classifiers(
+                                Classifier.single(
+                                        "category",
+                                        tr -> new Classification("category", "text", null, null)))
+                        .build();
+        eval.run();
+
+        var spans = testHarness.awaitExportedSpans();
+        assertNotNull(findSpanByName(spans, "score"), "expected score span");
+        assertNotNull(findSpanByName(spans, "category"), "expected classifier span");
+    }
+
+    @Test
+    @SneakyThrows
+    void classifierExceptionIsNonFatalAndRecordedInRootMetadata() {
+        var eval =
+                testHarness
+                        .braintrust()
+                        .<String, String>evalBuilder()
+                        .name("classifier-error-eval")
+                        .cases(DatasetCase.of("hello", null))
+                        .taskFunction(input -> input)
+                        .classifiers(
+                                Classifier.single(
+                                        "broken",
+                                        tr -> {
+                                            throw new RuntimeException("classifier boom");
+                                        }),
+                                Classifier.single(
+                                        "working",
+                                        tr -> new Classification("working", "ok", null, null)))
+                        .build();
+        eval.run();
+
+        var spans = testHarness.awaitExportedSpans();
+        var rootSpan = findRootEvalSpan(spans);
+        assertNotNull(rootSpan);
+
+        var metadataJson =
+                rootSpan.getAttributes().get(AttributeKey.stringKey("braintrust.metadata"));
+        assertNotNull(metadataJson, "expected metadata to be set when classifier errors occur");
+        var metadata = fromJson(metadataJson, Map.class);
+        @SuppressWarnings("unchecked")
+        var classifierErrors = (Map<String, Object>) metadata.get("classifier_errors");
+        assertNotNull(classifierErrors);
+        assertEquals("classifier boom", classifierErrors.get("broken"));
+
+        // The working classifier still produced output
+        var classificationsJson =
+                rootSpan.getAttributes().get(AttributeKey.stringKey("braintrust.classifications"));
+        assertNotNull(classificationsJson);
+        var classifications = fromJson(classificationsJson, Map.class);
+        assertTrue(classifications.containsKey("working"));
+    }
+
+    @Test
+    @SneakyThrows
+    void multiLabelClassifierGroupsUnderOneName() {
+        var eval =
+                testHarness
+                        .braintrust()
+                        .<String, String>evalBuilder()
+                        .name("multi-label-eval")
+                        .cases(DatasetCase.of("great!", null))
+                        .taskFunction(input -> input)
+                        .classifiers(
+                                Classifier.of(
+                                        "sentiment",
+                                        tr ->
+                                                List.of(
+                                                        new Classification(
+                                                                "sentiment",
+                                                                "positive",
+                                                                "Positive",
+                                                                null),
+                                                        new Classification(
+                                                                "sentiment",
+                                                                "enthusiastic",
+                                                                "Enthusiastic",
+                                                                null))))
+                        .build();
+        eval.run();
+
+        var spans = testHarness.awaitExportedSpans();
+        var rootSpan = findRootEvalSpan(spans);
+        assertNotNull(rootSpan);
+        var classifications =
+                fromJson(
+                        rootSpan.getAttributes()
+                                .get(AttributeKey.stringKey("braintrust.classifications")),
+                        Map.class);
+        @SuppressWarnings("unchecked")
+        var sentiment = (List<Map<String, Object>>) classifications.get("sentiment");
+        assertEquals(2, sentiment.size());
+        assertEquals("positive", sentiment.get(0).get("id"));
+        assertEquals("enthusiastic", sentiment.get(1).get("id"));
+    }
+
+    @Test
+    @SneakyThrows
+    void blankItemNameDefaultsToClassifierName() {
+        var eval =
+                testHarness
+                        .braintrust()
+                        .<String, String>evalBuilder()
+                        .name("default-name-eval")
+                        .cases(DatasetCase.of("hello", null))
+                        .taskFunction(input -> input)
+                        .classifiers(
+                                // No name on the item — should fall back to the classifier name.
+                                Classifier.single(
+                                        "my_classifier",
+                                        tr -> new Classification(null, "foo", null, null)))
+                        .build();
+        eval.run();
+
+        var spans = testHarness.awaitExportedSpans();
+        var rootSpan = findRootEvalSpan(spans);
+        assertNotNull(rootSpan);
+        var classifications =
+                fromJson(
+                        rootSpan.getAttributes()
+                                .get(AttributeKey.stringKey("braintrust.classifications")),
+                        Map.class);
+        assertTrue(classifications.containsKey("my_classifier"));
+    }
+
+    private static SpanData findSpanByName(List<SpanData> spans, String name) {
+        return spans.stream().filter(s -> name.equals(s.getName())).findFirst().orElse(null);
+    }
+
+    private static SpanData findRootEvalSpan(List<SpanData> spans) {
+        return spans.stream().filter(s -> "eval".equals(s.getName())).findFirst().orElse(null);
+    }
+}
diff --git a/braintrust-sdk/src/test/java/dev/braintrust/eval/ClassifierTest.java b/braintrust-sdk/src/test/java/dev/braintrust/eval/ClassifierTest.java
new file mode 100644
index 00000000..37ada2cd
--- /dev/null
+++ b/braintrust-sdk/src/test/java/dev/braintrust/eval/ClassifierTest.java
@@ -0,0 +1,128 @@
+package dev.braintrust.eval;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+public class ClassifierTest {
+
+    private static <T> TaskResult<String, T> taskResult(String input, T output) {
+        return new TaskResult<>(output, DatasetCase.of(input, null));
+    }
+
+    @Test
+    void singleFactoryReturnsOneClassification() {
+        Classifier<String, String> classifier =
+                Classifier.single(
+                        "category",
+                        tr -> new Classification("category", "greeting", "Greeting", null));
+
+        var result = classifier.classify(taskResult("hello", "hello"));
+        assertEquals(1, result.size());
+        assertEquals("greeting", result.get(0).id());
+        assertEquals("Greeting", result.get(0).label());
+        assertEquals("category", classifier.getName());
+    }
+
+    @Test
+    void singleFactoryNullReturnNormalizesToEmptyList() {
+        Classifier<String, String> classifier = Classifier.single("maybe", tr -> null);
+        assertEquals(List.of(), classifier.classify(taskResult("x", "x")));
+    }
+
+    @Test
+    void listFactoryReturnsMultipleClassifications() {
+        Classifier<String, String> classifier =
+                Classifier.of(
+                        "sentiment",
+                        tr ->
+                                List.of(
+                                        new Classification(
+                                                "sentiment", "positive", "Positive", null),
+                                        new Classification(
+                                                "sentiment",
+                                                "enthusiastic",
+                                                "Enthusiastic",
+                                                null)));
+
+        var result = classifier.classify(taskResult("great!", "great!"));
+        assertEquals(2, result.size());
+        assertEquals("positive", result.get(0).id());
+        assertEquals("enthusiastic", result.get(1).id());
+    }
+
+    @Test
+    void listFactoryNullReturnNormalizesToEmptyList() {
+        Classifier<String, String> classifier = Classifier.of("maybe", tr -> null);
+        assertEquals(List.of(), classifier.classify(taskResult("x", "x")));
+    }
+
+    @Test
+    void classificationOfHelpers() {
+        var c1 = Classification.of("id1");
+        assertNull(c1.name());
+        assertEquals("id1", c1.id());
+        assertNull(c1.label());
+        assertNull(c1.metadata());
+
+        var c2 = Classification.of("id2", "Label 2");
+        assertEquals("id2", c2.id());
+        assertEquals("Label 2", c2.label());
+
+        var c3 = Classification.of("nm", "id3", "Label 3");
+        assertEquals("nm", c3.name());
+        assertEquals("id3", c3.id());
+        assertEquals("Label 3", c3.label());
+    }
+
+    @Test
+    void classificationWithMetadataIsPreserved() {
+        var item =
+                new Classification(
+                        "category", "greeting", "Greeting", Map.of("source", "unit-test"));
+        Classifier<String, String> classifier = Classifier.single("category", tr -> item);
+
+        var result = classifier.classify(taskResult("hi", "hi"));
+        assertEquals(1, result.size());
+        assertEquals(Map.of("source", "unit-test"), result.get(0).metadata());
+    }
+
+    @Test
+    void validationThrowsForBlankId() {
+        Classifier<String, String> classifier =
+                Classifier.single("bad", tr -> new Classification("bad", "", null, null));
+
+        var error =
+                assertThrows(
+                        IllegalArgumentException.class,
+                        () -> classifier.classify(taskResult("x", "x")));
+        assertTrue(
+                error.getMessage().contains("each classification must be a non-empty object"),
+                "expected spec wording, got: " + error.getMessage());
+    }
+
+    @Test
+    void validationThrowsForNullItemInList() {
+        Classifier<String, String> classifier =
+                Classifier.of("bad", tr -> java.util.Arrays.asList((Classification) null));
+
+        var error =
+                assertThrows(
+                        IllegalArgumentException.class,
+                        () -> classifier.classify(taskResult("x", "x")));
+        assertTrue(
+                error.getMessage().contains("each classification must be a non-empty object"),
+                "expected spec wording, got: " + error.getMessage());
+    }
+
+    @Test
+    void getNameReturnsConstructorName() {
+        Classifier<String, String> c1 = Classifier.of("foo", tr -> List.of());
+        assertEquals("foo", c1.getName());
+
+        Classifier<String, String> c2 = Classifier.single("bar", tr -> null);
+        assertEquals("bar", c2.getName());
+    }
+}
diff --git a/examples/src/main/java/dev/braintrust/examples/ClassifiersExample.java b/examples/src/main/java/dev/braintrust/examples/ClassifiersExample.java
new file mode 100644
index 00000000..270dcc61
--- /dev/null
+++ b/examples/src/main/java/dev/braintrust/examples/ClassifiersExample.java
@@ -0,0 +1,158 @@
+package dev.braintrust.examples;
+
+import dev.braintrust.Braintrust;
+import dev.braintrust.eval.Classification;
+import dev.braintrust.eval.Classifier;
+import dev.braintrust.eval.DatasetCase;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Classifiers categorize and label eval outputs. Unlike scorers (numeric 0-1), classifiers return
+ * structured {@link Classification} items with an id, optional label, and optional metadata.
+ *
+ * <p>Three patterns are shown:
+ *
+ * <ol>
+ *   <li>{@link Classifier#single} for a single-label classifier returning one {@link
+ *       Classification}.
+ *   <li>{@link Classifier#of} for a multi-label classifier returning a list.
+ *   <li>An anonymous {@link Classifier} implementation for reusable classifiers with their own
+ *       logic.
+ * </ol>
+ *
+ * <p>Classifiers and scorers run independently — you can use either, or both together.
+ */
+public class ClassifiersExample {
+    public static void main(String[] args) throws Exception {
+        var braintrust = Braintrust.get();
+
+        // 1. Single-label classifier.
+        Classifier<String, String> intentClassifier =
+                Classifier.single(
+                        "intent",
+                        tr -> {
+                            var input = tr.datasetCase().input();
+                            String id;
+                            if (input.matches("(?i).*thank.*")) {
+                                id = "praise";
+                            } else if (input.matches("(?i).*(waiting|order|update).*")) {
+                                id = "follow_up";
+                            } else if (input.matches("(?i).*(password|reset|find).*")) {
+                                id = "how_to";
+                            } else if (input.matches("(?i).*(damaged|refund).*")) {
+                                id = "complaint";
+                            } else {
+                                id = "other";
+                            }
+                            return new Classification(
+                                    "intent", id, capitalize(id.replace('_', ' ')), null);
+                        });
+
+        // 2. Multi-label classifier.
+        Classifier<String, String> toneClassifier =
+                Classifier.of(
+                        "tone",
+                        tr -> {
+                            var input = tr.datasetCase().input();
+                            List<Classification> labels = new ArrayList<>();
+                            if (input.matches("(?i).*(immediately|unacceptable|waiting).*")) {
+                                labels.add(new Classification("tone", "urgent", "Urgent", null));
+                            }
+                            if (input.matches("(?i).*(please|thank|just checking).*")) {
+                                labels.add(new Classification("tone", "polite", "Polite", null));
+                            }
+                            if (input.matches("(?i).*(unacceptable|damaged|waiting).*")) {
+                                labels.add(
+                                        new Classification(
+                                                "tone", "frustrated", "Frustrated", null));
+                            }
+                            if (labels.isEmpty()) {
+                                labels.add(new Classification("tone", "neutral", "Neutral", null));
+                            }
+                            return labels;
+                        });
+
+        // 3. Custom Classifier implementation — full control over name and logic.
+        Classifier<String, String> qualityClassifier =
+                new Classifier<>() {
+                    @Override
+                    public String getName() {
+                        return "response_quality";
+                    }
+
+                    @Override
+                    public List<Classification> classify(
+                            dev.braintrust.eval.TaskResult<String, String> tr) {
+                        var output = tr.result();
+                        int wordCount = output == null ? 0 : output.trim().split("\\s+").length;
+                        String id;
+                        if (output == null || output.isBlank()) {
+                            id = "no_response";
+                        } else if (wordCount < 5) {
+                            id = "too_short";
+                        } else if (output.matches("(?i).*(immediately|right away|look into).*")) {
+                            id = "action_oriented";
+                        } else {
+                            id = "informational";
+                        }
+                        return List.of(
+                                new Classification(
+                                        "response_quality",
+                                        id,
+                                        capitalize(id.replace('_', ' ')),
+                                        java.util.Map.of("word_count", wordCount)));
+                    }
+                };
+
+        var eval =
+                braintrust
+                        .<String, String>evalBuilder()
+                        .name("classifiers-example-" + System.currentTimeMillis())
+                        .cases(
+                                DatasetCase.of(
+                                        "Hi! I just wanted to say thank you, the product is"
+                                                + " amazing!",
+                                        null),
+                                DatasetCase.of(
+                                        "I've been waiting 2 weeks for my order. This is"
+                                                + " unacceptable!",
+                                        null),
+                                DatasetCase.of(
+                                        "How do I reset my password? I can't find the option"
+                                                + " anywhere.",
+                                        null),
+                                DatasetCase.of(
+                                        "The item arrived damaged. I need a refund immediately.",
+                                        null),
+                                DatasetCase.of(
+                                        "Just checking in — any update on my ticket #4821?", null))
+                        .taskFunction(ClassifiersExample::generateResponse)
+                        .classifiers(intentClassifier, toneClassifier, qualityClassifier)
+                        .build();
+
+        var result = eval.run();
+        System.out.println("\n\n" + result.createReportString());
+    }
+
+    private static String generateResponse(String message) {
+        if (message.matches("(?i).*thank.*")) {
+            return "You're welcome! So glad you're enjoying it.";
+        }
+        if (message.matches("(?i).*(waiting|order).*")) {
+            return "I sincerely apologise for the delay. Let me look into this right away.";
+        }
+        if (message.matches("(?i).*(password|reset).*")) {
+            return "To reset your password, go to Settings > Account > Reset Password.";
+        }
+        if (message.matches("(?i).*(damaged|refund).*")) {
+            return "I'm sorry to hear that. I'll process your refund immediately.";
+        }
+        return "Thanks for reaching out! Let me check on that for you.";
+    }
+
+    private static String capitalize(String s) {
+        if (s == null || s.isEmpty()) return s;
+        return Character.toUpperCase(s.charAt(0)) + s.substring(1);
+    }
+}
diff --git a/test-harness/src/testFixtures/java/dev/braintrust/TestHarness.java b/test-harness/src/testFixtures/java/dev/braintrust/TestHarness.java
index e95ef5a0..75a8ece6 100644
--- a/test-harness/src/testFixtures/java/dev/braintrust/TestHarness.java
+++ b/test-harness/src/testFixtures/java/dev/braintrust/TestHarness.java
@@ -313,7 +313,7 @@ public void ensureRemoteDataset(String datasetName, Dataset<?, ?> expectedData)
 
         // verify
         var btDataset = braintrust.fetchDataset(datasetName);
-        if (datasetsEqual(expectedData, btDataset)) {
+        if (!datasetsEqual(expectedData, btDataset)) {
             throw new RuntimeException(
                     "failed to ensure expected dataset: %s -- %s"
                             .formatted(toList(expectedData), toList(btDataset)));
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-08d26d2faef8.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-08d26d2faef8.json
new file mode 100644
index 00000000..634dffc9
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-08d26d2faef8.json
@@ -0,0 +1 @@
+{"org_info":[{"id":"5abfae3a-7aa7-4653-a9c8-b3efcb18f584","name":"Braintrust SDKs","api_url":"https://api.braintrust.dev","git_metadata":null,"is_universal_api":null,"proxy_url":"https://api.braintrust.dev","realtime_url":"wss://realtime.braintrustapi.com"}]}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-228248286fba.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-228248286fba.json
new file mode 100644
index 00000000..634dffc9
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-228248286fba.json
@@ -0,0 +1 @@
+{"org_info":[{"id":"5abfae3a-7aa7-4653-a9c8-b3efcb18f584","name":"Braintrust SDKs","api_url":"https://api.braintrust.dev","git_metadata":null,"is_universal_api":null,"proxy_url":"https://api.braintrust.dev","realtime_url":"wss://realtime.braintrustapi.com"}]}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-4139f91c7e72.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-4139f91c7e72.json
new file mode 100644
index 00000000..634dffc9
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-4139f91c7e72.json
@@ -0,0 +1 @@
+{"org_info":[{"id":"5abfae3a-7aa7-4653-a9c8-b3efcb18f584","name":"Braintrust SDKs","api_url":"https://api.braintrust.dev","git_metadata":null,"is_universal_api":null,"proxy_url":"https://api.braintrust.dev","realtime_url":"wss://realtime.braintrustapi.com"}]}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-684178b0ab9d.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-684178b0ab9d.json
new file mode 100644
index 00000000..634dffc9
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-684178b0ab9d.json
@@ -0,0 +1 @@
+{"org_info":[{"id":"5abfae3a-7aa7-4653-a9c8-b3efcb18f584","name":"Braintrust SDKs","api_url":"https://api.braintrust.dev","git_metadata":null,"is_universal_api":null,"proxy_url":"https://api.braintrust.dev","realtime_url":"wss://realtime.braintrustapi.com"}]}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-9611c99e6aac.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-9611c99e6aac.json
new file mode 100644
index 00000000..634dffc9
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-9611c99e6aac.json
@@ -0,0 +1 @@
+{"org_info":[{"id":"5abfae3a-7aa7-4653-a9c8-b3efcb18f584","name":"Braintrust SDKs","api_url":"https://api.braintrust.dev","git_metadata":null,"is_universal_api":null,"proxy_url":"https://api.braintrust.dev","realtime_url":"wss://realtime.braintrustapi.com"}]}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-a7fce53bd211.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-a7fce53bd211.json
new file mode 100644
index 00000000..634dffc9
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-a7fce53bd211.json
@@ -0,0 +1 @@
+{"org_info":[{"id":"5abfae3a-7aa7-4653-a9c8-b3efcb18f584","name":"Braintrust SDKs","api_url":"https://api.braintrust.dev","git_metadata":null,"is_universal_api":null,"proxy_url":"https://api.braintrust.dev","realtime_url":"wss://realtime.braintrustapi.com"}]}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-fd38313bebba.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-fd38313bebba.json
new file mode 100644
index 00000000..634dffc9
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-fd38313bebba.json
@@ -0,0 +1 @@
+{"org_info":[{"id":"5abfae3a-7aa7-4653-a9c8-b3efcb18f584","name":"Braintrust SDKs","api_url":"https://api.braintrust.dev","git_metadata":null,"is_universal_api":null,"proxy_url":"https://api.braintrust.dev","realtime_url":"wss://realtime.braintrustapi.com"}]}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-fda483633056.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-fda483633056.json
new file mode 100644
index 00000000..634dffc9
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/api_apikey_login-fda483633056.json
@@ -0,0 +1 @@
+{"org_info":[{"id":"5abfae3a-7aa7-4653-a9c8-b3efcb18f584","name":"Braintrust SDKs","api_url":"https://api.braintrust.dev","git_metadata":null,"is_universal_api":null,"proxy_url":"https://api.braintrust.dev","realtime_url":"wss://realtime.braintrustapi.com"}]}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-1185d0796fb3.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-1185d0796fb3.json
new file mode 100644
index 00000000..a817864e
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-1185d0796fb3.json
@@ -0,0 +1 @@
+{"id":"bd13b6ad-0fb2-4477-b407-0aa58127586e","project_id":"f1e858a4-58e3-408f-983f-016760d7fa25","name":"scorer-and-classifier-eval","description":null,"created":"2026-05-27T10:13:48.702Z","repo_info":{},"commit":null,"base_exp_id":null,"deleted_at":null,"dataset_id":null,"dataset_version":null,"internal_metadata":null,"parameters_id":null,"parameters_version":null,"public":false,"user_id":"08e3988c-e05c-4324-8763-8998a5b39755","metadata":null,"tags":null}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-2c8bb270c5cf.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-2c8bb270c5cf.json
new file mode 100644
index 00000000..eadc14a9
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-2c8bb270c5cf.json
@@ -0,0 +1 @@
+{"id":"bda48716-d8cc-406b-aed1-10ca29b511e5","project_id":"f1e858a4-58e3-408f-983f-016760d7fa25","name":"classifier-only-eval","description":null,"created":"2026-05-27T10:13:52.580Z","repo_info":{},"commit":null,"base_exp_id":null,"deleted_at":null,"dataset_id":null,"dataset_version":null,"internal_metadata":null,"parameters_id":null,"parameters_version":null,"public":false,"user_id":"08e3988c-e05c-4324-8763-8998a5b39755","metadata":null,"tags":null}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-4f1bd5afd18d.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-4f1bd5afd18d.json
new file mode 100644
index 00000000..8c927324
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-4f1bd5afd18d.json
@@ -0,0 +1 @@
+{"id":"129eb154-c227-43f4-a549-35bd3f281bd9","project_id":"f1e858a4-58e3-408f-983f-016760d7fa25","name":"classifier-error-eval","description":null,"created":"2026-05-27T10:14:02.504Z","repo_info":{},"commit":null,"base_exp_id":null,"deleted_at":null,"dataset_id":null,"dataset_version":null,"internal_metadata":null,"parameters_id":null,"parameters_version":null,"public":false,"user_id":"08e3988c-e05c-4324-8763-8998a5b39755","metadata":null,"tags":null}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-80d23f49c06c.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-80d23f49c06c.json
new file mode 100644
index 00000000..42a3a8d2
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-80d23f49c06c.json
@@ -0,0 +1 @@
+{"id":"ed5735fb-b23b-4522-9b4f-546bcae35eae","project_id":"f1e858a4-58e3-408f-983f-016760d7fa25","name":"multi-label-eval","description":null,"created":"2026-05-27T10:13:46.338Z","repo_info":{},"commit":null,"base_exp_id":null,"deleted_at":null,"dataset_id":null,"dataset_version":null,"internal_metadata":null,"parameters_id":null,"parameters_version":null,"public":false,"user_id":"08e3988c-e05c-4324-8763-8998a5b39755","metadata":null,"tags":null}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-81a6ebbafe29.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-81a6ebbafe29.json
new file mode 100644
index 00000000..0f2383ab
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_experiment-81a6ebbafe29.json
@@ -0,0 +1 @@
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new file mode 100644
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-410ff9f133da.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-410ff9f133da.json
new file mode 100644
index 00000000..89452950
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-4891298f2969.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-4891298f2969.json
new file mode 100644
index 00000000..89452950
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-4891298f2969.json
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-543a07178006.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-543a07178006.json
new file mode 100644
index 00000000..89452950
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-543a07178006.json
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new file mode 100644
index 00000000..89452950
--- /dev/null
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-dd7665d7a48a.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-dd7665d7a48a.json
new file mode 100644
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--- /dev/null
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-e74886687a34.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/__files/v1_project-e74886687a34.json
new file mode 100644
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--- /dev/null
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new file mode 100644
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-08d26d2faef8.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-08d26d2faef8.json
new file mode 100644
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+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-08d26d2faef8.json
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+  },
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-228248286fba.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-228248286fba.json
new file mode 100644
index 00000000..d130210d
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-228248286fba.json
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-4139f91c7e72.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-4139f91c7e72.json
new file mode 100644
index 00000000..376ad543
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+  "name" : "api_apikey_login",
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+  },
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+    "bodyFileName" : "api_apikey_login-4139f91c7e72.json",
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-684178b0ab9d.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-684178b0ab9d.json
new file mode 100644
index 00000000..8b8a9bdb
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+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-684178b0ab9d.json
@@ -0,0 +1,37 @@
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+  "name" : "api_apikey_login",
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-9611c99e6aac.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-9611c99e6aac.json
new file mode 100644
index 00000000..417b5b06
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+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-9611c99e6aac.json
@@ -0,0 +1,38 @@
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+    "bodyFileName" : "api_apikey_login-9611c99e6aac.json",
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-a7fce53bd211.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-a7fce53bd211.json
new file mode 100644
index 00000000..d14b3a9e
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-a7fce53bd211.json
@@ -0,0 +1,38 @@
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+    "bodyFileName" : "api_apikey_login-a7fce53bd211.json",
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-fd38313bebba.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-fd38313bebba.json
new file mode 100644
index 00000000..349b8a9e
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-fd38313bebba.json
@@ -0,0 +1,38 @@
+{
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-fda483633056.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-fda483633056.json
new file mode 100644
index 00000000..e2cd318e
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/api_apikey_login-fda483633056.json
@@ -0,0 +1,38 @@
+{
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\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-1185d0796fb3.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-1185d0796fb3.json
new file mode 100644
index 00000000..4c124322
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-1185d0796fb3.json
@@ -0,0 +1,45 @@
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-2c8bb270c5cf.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-2c8bb270c5cf.json
new file mode 100644
index 00000000..aac667da
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-2c8bb270c5cf.json
@@ -0,0 +1,45 @@
+{
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+    "bodyFileName" : "v1_experiment-2c8bb270c5cf.json",
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-4f1bd5afd18d.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-4f1bd5afd18d.json
new file mode 100644
index 00000000..728272dd
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-4f1bd5afd18d.json
@@ -0,0 +1,45 @@
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+    "bodyFileName" : "v1_experiment-4f1bd5afd18d.json",
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-80d23f49c06c.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-80d23f49c06c.json
new file mode 100644
index 00000000..9e90708c
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+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-80d23f49c06c.json
@@ -0,0 +1,45 @@
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new file mode 100644
index 00000000..3e098ee6
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+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_experiment-81a6ebbafe29.json
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-30867e7088bd.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-30867e7088bd.json
new file mode 100644
index 00000000..f05070e2
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-30867e7088bd.json
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-410ff9f133da.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-410ff9f133da.json
new file mode 100644
index 00000000..3b61260c
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-410ff9f133da.json
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-4891298f2969.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-4891298f2969.json
new file mode 100644
index 00000000..9d6e550d
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-4891298f2969.json
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-543a07178006.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-543a07178006.json
new file mode 100644
index 00000000..b9c1e229
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-543a07178006.json
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diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-c0742bb3c63f.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-c0742bb3c63f.json
new file mode 100644
index 00000000..55948026
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+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-c0742bb3c63f.json
@@ -0,0 +1,45 @@
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new file mode 100644
index 00000000..22c2cf49
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+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-dd7665d7a48a.json
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--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-e74886687a34.json
@@ -0,0 +1,45 @@
+{
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+  "name" : "v1_project",
+  "request" : {
+    "urlPath" : "/v1/project",
+    "method" : "GET",
+    "queryParameters" : {
+      "project_name" : {
+        "hasExactly" : [ {
+          "equalTo" : "java-unit-test"
+        } ]
+      }
+    }
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+    "bodyFileName" : "v1_project-e74886687a34.json",
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+}
\ No newline at end of file
diff --git a/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-e7e35e493e43.json b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-e7e35e493e43.json
new file mode 100644
index 00000000..91a2f6b6
--- /dev/null
+++ b/test-harness/src/testFixtures/resources/cassettes/braintrust/mappings/v1_project-e7e35e493e43.json
@@ -0,0 +1,45 @@
+{
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+  "name" : "v1_project",
+  "request" : {
+    "urlPath" : "/v1/project",
+    "method" : "GET",
+    "queryParameters" : {
+      "project_name" : {
+        "hasExactly" : [ {
+          "equalTo" : "java-unit-test"
+        } ]
+      }
+    }
+  },
+  "response" : {
+    "status" : 200,
+    "bodyFileName" : "v1_project-e7e35e493e43.json",
+    "headers" : {
+      "X-Cache" : "Miss from cloudfront",
+      "expires" : "0",
+      "x-amz-apigw-id" : "eBXBpHbzIAMEgmQ=",
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+      "x-amzn-Remapped-content-length" : "361",
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+      "cache-control" : "no-store, no-cache, must-revalidate, proxy-revalidate",
+      "surrogate-control" : "no-store",
+      "Content-Type" : "application/json; charset=utf-8"
+    }
+  },
+  "uuid" : "d2f428e5-f001-3e3a-9b24-5e1d7065518c",
+  "persistent" : true,
+  "scenarioName" : "scenario-2-v1-project",
+  "requiredScenarioState" : "scenario-2-v1-project-2",
+  "newScenarioState" : "scenario-2-v1-project-3",
+  "insertionIndex" : 138
+}
\ No newline at end of file