diff --git a/UPGRADING.md b/UPGRADING.md
index c99de606f..999e0c448 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -1,3 +1,16 @@
+# Upgrading from 4.0.x to 4.1.x
+
+## On-disk format version 7
+- Version 7 of the on-disk graph format adds one feature, inline int8 vectors (`FeatureId.INLINE_BYTE_VECTORS`):
+  each node's byte vector stored inline, one byte per dimension. Apart from that feature, a version 7 file has
+  the version 6 layout.
+- JVector 4.0.x reads formats up to 6 and rejects version 7 files. `OnDiskGraphIndex.CURRENT_VERSION`,
+  the default for `OnDiskGraphIndexWriter.Builder` and for `CompressedVectors.write(out)`, is now 7.
+- To keep a rollback to 4.0.x possible, pass the version explicitly until every reader runs 4.1:
+  `withVersion(6)` on graph writer builders and `write(out, 6)` for compressors and compressed vectors.
+  A version 6 writer rejects `INLINE_BYTE_VECTORS`.
+- `OnDiskGraphIndexCompactor` always writes `CURRENT_VERSION`; it has no option to write an older version.
+
 # Upgrading from 3.0.x to 4.0.x
 
 ## New features
diff --git a/docs/release notes/4.1.0/709.feature.md b/docs/release notes/4.1.0/709.feature.md
index cbb188527..dcd6a71c0 100644
--- a/docs/release notes/4.1.0/709.feature.md	
+++ b/docs/release notes/4.1.0/709.feature.md	
@@ -49,4 +49,5 @@ try (var builder = GraphIndexBuilder.builder(vectors, ByteVectorSimilarityFuncti
 * Zero vectors are not supported with `COSINE` (the result is undefined); do not index them.
 * Existing float32 callers keep working: `RandomAccessVectorValues.getVector` keeps its `VectorFloat<?>`
   signature and `GraphIndexBuilder.build(RandomAccessVectorValues)` is retained as a forwarding overload.
-* Int8 indexes require on-disk format version 6 or later.
+* Int8 indexes require on-disk format version 7 or later. JVector 4.0.x reads formats up to 6 and rejects
+  version 7 files; a version 6 writer rejects `INLINE_BYTE_VECTORS`.
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/AbstractGraphIndexFormat.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/AbstractGraphIndexFormat.java
index 2f77cf768..12bb1d28a 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/AbstractGraphIndexFormat.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/AbstractGraphIndexFormat.java
@@ -381,7 +381,7 @@ public int commonHeaderSize() {
     public void writeHeaderFeatures(IndexWriter out, Map<FeatureId,? extends Feature> features) throws IOException {
         // we restrict pre-version-3 writers to INLINE_VECTORS features, so we don't need additional version-handling here
         for (Feature writer : features.values()) {
-            writer.writeHeader(out);
+            writer.writeHeader(out, getVersion());
         }
     }
 
@@ -415,7 +415,7 @@ public OnDiskGraphIndex loadOnDiskIndex(RandomAccessReader reader, Header header
      */
     protected static Set<FeatureId> allFeatures() {
         return EnumSet.of(FeatureId.INLINE_VECTORS, FeatureId.FUSED_PQ, FeatureId.NVQ_VECTORS,
-                FeatureId.SEPARATED_VECTORS, FeatureId.SEPARATED_NVQ, FeatureId.INLINE_BYTE_VECTORS);
+                FeatureId.SEPARATED_VECTORS, FeatureId.SEPARATED_NVQ);
     }
 
     /**
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatFactory.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatFactory.java
index 12010bc1e..b7c0014a1 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatFactory.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatFactory.java
@@ -35,7 +35,8 @@ public class GraphIndexFormatFactory {
         3, new GraphIndexFormatV3(),
         4, new GraphIndexFormatV4(),
         5, new GraphIndexFormatV5(),
-        6, new GraphIndexFormatV6()
+        6, new GraphIndexFormatV6(),
+        7, new GraphIndexFormatV7()
     );
 
     /**
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatV6.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatV6.java
index c9d965aa4..a9a46ed5c 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatV6.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatV6.java
@@ -26,6 +26,7 @@
 import java.util.EnumMap;
 import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.Set;
 import java.util.function.IntFunction;
 import java.util.stream.Collectors;
 
@@ -44,7 +45,12 @@ class GraphIndexFormatV6 extends GraphIndexFormatV5 {
 
     /** Creates the singleton format for version 6. */
     GraphIndexFormatV6() {
-        super(6, allFeatures());
+        this(6, allFeatures());
+    }
+
+    /** Allows later feature extensions to reuse the V6 record and hierarchy layout. */
+    protected GraphIndexFormatV6(int version, Set<FeatureId> supportedFeatures) {
+        super(version, supportedFeatures);
     }
 
     /** Places fused features last so non-fused inline features occupy a contiguous prefix. */
@@ -112,7 +118,7 @@ public void writeHeaderFeatures(IndexWriter out, Map<FeatureId,? extends Feature
         for (var featureId : features.keySet()) {
             out.writeInt(featureId.ordinal());
             Feature feature = features.get(featureId);
-            feature.writeHeader(out);
+            feature.writeHeader(out, getVersion());
         }
     }
 
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatV7.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatV7.java
new file mode 100644
index 000000000..49ff3940d
--- /dev/null
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/GraphIndexFormatV7.java
@@ -0,0 +1,39 @@
+/*
+ * Copyright DataStax, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.github.jbellis.jvector.graph.disk;
+
+import io.github.jbellis.jvector.graph.disk.feature.FeatureId;
+
+import java.util.EnumSet;
+import java.util.Set;
+
+/**
+ * Version 7 adds inline int8 vectors while retaining the V6 graph record layout.
+ * Each node record carries its byte vector inline, one byte per dimension.
+ */
+final class GraphIndexFormatV7 extends GraphIndexFormatV6 {
+    GraphIndexFormatV7() {
+        super(7, supportedFeatures());
+    }
+
+    /** The extension is restricted to V7; earlier formats retain their feature sets. */
+    private static Set<FeatureId> supportedFeatures() {
+        var features = EnumSet.copyOf(allFeatures());
+        features.add(FeatureId.INLINE_BYTE_VECTORS);
+        return features;
+    }
+}
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/OnDiskGraphIndex.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/OnDiskGraphIndex.java
index 92f43292d..c67461162 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/OnDiskGraphIndex.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/OnDiskGraphIndex.java
@@ -71,7 +71,7 @@
 public class OnDiskGraphIndex implements ImmutableGraphIndex, AutoCloseable, Accountable
 {
     private static final Logger logger = LoggerFactory.getLogger(OnDiskGraphIndex.class);
-    public static final int CURRENT_VERSION = 6;
+    public static final int CURRENT_VERSION = 7;
     static final int MAGIC = 0xFFFF0D61; // FFFF to distinguish from old graphs, which should never start with a negative size "ODGI"
     static final VectorTypeSupport vectorTypeSupport = VectorizationProvider.getInstance().getVectorTypeSupport();
     final ReaderSupplier readerSupplier;
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/Feature.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/Feature.java
index 03dd2ec98..1602aa2fa 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/Feature.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/Feature.java
@@ -36,8 +36,27 @@ default boolean isFused() {
 
     int featureSize();
 
+    /**
+     * Writes this feature's header at {@link io.github.jbellis.jvector.graph.disk.OnDiskGraphIndex#CURRENT_VERSION}.
+     *
+     * @deprecated a header embedded in a graph must be written at the graph's version; use
+     *             {@link #writeHeader(IndexWriter, int)}
+     */
+    @Deprecated
     void writeHeader(IndexWriter out) throws IOException;
 
+    /**
+     * Writes this feature's header for a graph written at {@code version}. Features that serialize a
+     * compressor write it at this version, so a graph written at an older version is laid out as that
+     * version wrote it. The default ignores the version, for headers that don't depend on it.
+     *
+     * @param out the output to write to
+     * @param version the on-disk format version of the graph being written
+     */
+    default void writeHeader(IndexWriter out, int version) throws IOException {
+        writeHeader(out);
+    }
+
     default void writeInline(IndexWriter out, State state) throws IOException {
         // default no-op
     }
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/FusedPQ.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/FusedPQ.java
index 3dc404481..a8d39aa1b 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/FusedPQ.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/FusedPQ.java
@@ -135,9 +135,15 @@ public QuantizationCompactionStrategy createCompactionStrategy(CompactionContext
         return new FusedCompactionStrategy(ctx, this, retrainer);
     }
 
+    @Deprecated
     @Override
     public void writeHeader(IndexWriter out) throws IOException {
-        pq.write(out, OnDiskGraphIndex.CURRENT_VERSION);
+        writeHeader(out, OnDiskGraphIndex.CURRENT_VERSION);
+    }
+
+    @Override
+    public void writeHeader(IndexWriter out, int version) throws IOException {
+        pq.write(out, version);
     }
 
     // this is an awkward fit for the Feature.State design since we need to
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/InlineByteVectors.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/InlineByteVectors.java
index 86ebfff3c..981999b95 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/InlineByteVectors.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/InlineByteVectors.java
@@ -20,6 +20,7 @@
 import io.github.jbellis.jvector.disk.IndexWriter;
 import io.github.jbellis.jvector.disk.RandomAccessReader;
 import io.github.jbellis.jvector.graph.disk.CommonHeader;
+import io.github.jbellis.jvector.graph.disk.OnDiskGraphIndex;
 import io.github.jbellis.jvector.vector.VectorizationProvider;
 import io.github.jbellis.jvector.vector.types.ByteSequence;
 import io.github.jbellis.jvector.vector.types.VectorTypeSupport;
@@ -72,8 +73,14 @@ static InlineByteVectors load(CommonHeader header, RandomAccessReader reader) {
         return new InlineByteVectors(header.dimension);
     }
 
+    @Deprecated
     @Override
     public void writeHeader(IndexWriter out) {
+        writeHeader(out, OnDiskGraphIndex.CURRENT_VERSION);
+    }
+
+    @Override
+    public void writeHeader(IndexWriter out, int version) {
         // common header carries dimension; nothing extra needed
     }
 
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/InlineVectors.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/InlineVectors.java
index 005103ddb..cac33f6f2 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/InlineVectors.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/InlineVectors.java
@@ -19,6 +19,7 @@
 import io.github.jbellis.jvector.disk.IndexWriter;
 import io.github.jbellis.jvector.disk.RandomAccessReader;
 import io.github.jbellis.jvector.graph.disk.CommonHeader;
+import io.github.jbellis.jvector.graph.disk.OnDiskGraphIndex;
 import io.github.jbellis.jvector.vector.VectorizationProvider;
 import io.github.jbellis.jvector.vector.types.VectorFloat;
 import io.github.jbellis.jvector.vector.types.VectorTypeSupport;
@@ -58,8 +59,14 @@ static InlineVectors load(CommonHeader header, RandomAccessReader reader) {
         return new InlineVectors(header.dimension);
     }
 
+    @Deprecated
     @Override
     public void writeHeader(IndexWriter out) {
+        writeHeader(out, OnDiskGraphIndex.CURRENT_VERSION);
+    }
+
+    @Override
+    public void writeHeader(IndexWriter out, int version) {
         // common header contains dimension, which is sufficient
     }
 
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/NVQ.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/NVQ.java
index 492bb0dfe..863780bf1 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/NVQ.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/NVQ.java
@@ -69,9 +69,15 @@ static NVQ load(CommonHeader header, RandomAccessReader reader) {
         }
     }
 
+    @Deprecated
     @Override
     public void writeHeader(IndexWriter out) throws IOException {
-        nvq.write(out, OnDiskGraphIndex.CURRENT_VERSION);
+        writeHeader(out, OnDiskGraphIndex.CURRENT_VERSION);
+    }
+
+    @Override
+    public void writeHeader(IndexWriter out, int version) throws IOException {
+        nvq.write(out, version);
     }
 
     @Override
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/SeparatedNVQ.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/SeparatedNVQ.java
index b65370632..a0e3ddd21 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/SeparatedNVQ.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/SeparatedNVQ.java
@@ -67,9 +67,15 @@ public int featureSize() {
         return nvq.compressedVectorSize();
     }
 
+    @Deprecated
     @Override
     public void writeHeader(IndexWriter out) throws IOException {
-        nvq.write(out, OnDiskGraphIndex.CURRENT_VERSION);
+        writeHeader(out, OnDiskGraphIndex.CURRENT_VERSION);
+    }
+
+    @Override
+    public void writeHeader(IndexWriter out, int version) throws IOException {
+        nvq.write(out, version);
         out.writeLong(offset);
     }
 
diff --git a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/SeparatedVectors.java b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/SeparatedVectors.java
index 017aef53f..b399574af 100644
--- a/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/SeparatedVectors.java
+++ b/jvector-base/src/main/java/io/github/jbellis/jvector/graph/disk/feature/SeparatedVectors.java
@@ -19,6 +19,7 @@
 import io.github.jbellis.jvector.disk.IndexWriter;
 import io.github.jbellis.jvector.disk.RandomAccessReader;
 import io.github.jbellis.jvector.graph.disk.CommonHeader;
+import io.github.jbellis.jvector.graph.disk.OnDiskGraphIndex;
 import io.github.jbellis.jvector.vector.VectorizationProvider;
 import io.github.jbellis.jvector.vector.types.VectorTypeSupport;
 
@@ -60,8 +61,14 @@ public int featureSize() {
         return dimension * Float.BYTES;
     }
 
+    @Deprecated
     @Override
     public void writeHeader(IndexWriter out) throws IOException {
+        writeHeader(out, OnDiskGraphIndex.CURRENT_VERSION);
+    }
+
+    @Override
+    public void writeHeader(IndexWriter out, int version) throws IOException {
         out.writeLong(offset);
     }
 
diff --git a/jvector-examples/yaml-configs/index-parameters/cap-10M.yml b/jvector-examples/yaml-configs/index-parameters/cap-10M.yml
index c9c6c09d8..93b5b4eb9 100644
--- a/jvector-examples/yaml-configs/index-parameters/cap-10M.yml
+++ b/jvector-examples/yaml-configs/index-parameters/cap-10M.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: cap-10M
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/cap-1M.yml b/jvector-examples/yaml-configs/index-parameters/cap-1M.yml
index 6aa8454b5..08a8e38a4 100644
--- a/jvector-examples/yaml-configs/index-parameters/cap-1M.yml
+++ b/jvector-examples/yaml-configs/index-parameters/cap-1M.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: cap-1M
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/cohere-english-v3-10M.yml b/jvector-examples/yaml-configs/index-parameters/cohere-english-v3-10M.yml
index 17b3dd54a..97fb04c36 100644
--- a/jvector-examples/yaml-configs/index-parameters/cohere-english-v3-10M.yml
+++ b/jvector-examples/yaml-configs/index-parameters/cohere-english-v3-10M.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: cohere-english-v3-10M
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/cohere-english-v3-1M.yml b/jvector-examples/yaml-configs/index-parameters/cohere-english-v3-1M.yml
index 56fb2849f..dc9dcf7f2 100644
--- a/jvector-examples/yaml-configs/index-parameters/cohere-english-v3-1M.yml
+++ b/jvector-examples/yaml-configs/index-parameters/cohere-english-v3-1M.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: cohere-english-v3-1M
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/colbert-1M.yml b/jvector-examples/yaml-configs/index-parameters/colbert-1M.yml
index 66b47a056..3bcf9668a 100644
--- a/jvector-examples/yaml-configs/index-parameters/colbert-1M.yml
+++ b/jvector-examples/yaml-configs/index-parameters/colbert-1M.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: colbert-1M
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/default.yml b/jvector-examples/yaml-configs/index-parameters/default.yml
index e0a4ed3a5..fdb3da125 100644
--- a/jvector-examples/yaml-configs/index-parameters/default.yml
+++ b/jvector-examples/yaml-configs/index-parameters/default.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: default
 # Prefetch bounded batches instead of preloading the entire dataset into memory.
diff --git a/jvector-examples/yaml-configs/index-parameters/dpr-gemma-10M.yml b/jvector-examples/yaml-configs/index-parameters/dpr-gemma-10M.yml
index 90eac34e8..16acbe6cf 100644
--- a/jvector-examples/yaml-configs/index-parameters/dpr-gemma-10M.yml
+++ b/jvector-examples/yaml-configs/index-parameters/dpr-gemma-10M.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: dpr-gemma-10M
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/dpr-gemma-1M.yml b/jvector-examples/yaml-configs/index-parameters/dpr-gemma-1M.yml
index 354c06436..a194ace14 100644
--- a/jvector-examples/yaml-configs/index-parameters/dpr-gemma-1M.yml
+++ b/jvector-examples/yaml-configs/index-parameters/dpr-gemma-1M.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: dpr-gemma-1M
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/glove-100-angular.yml b/jvector-examples/yaml-configs/index-parameters/glove-100-angular.yml
index 1b03b1edd..920fee6a8 100644
--- a/jvector-examples/yaml-configs/index-parameters/glove-100-angular.yml
+++ b/jvector-examples/yaml-configs/index-parameters/glove-100-angular.yml
@@ -1,6 +1,6 @@
 # This is here for loader testing purposes only, use other datasets for realistic test data
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: glove-100-angular
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/glove-200-angular.yml b/jvector-examples/yaml-configs/index-parameters/glove-200-angular.yml
index 1630baaba..f39457919 100644
--- a/jvector-examples/yaml-configs/index-parameters/glove-200-angular.yml
+++ b/jvector-examples/yaml-configs/index-parameters/glove-200-angular.yml
@@ -1,6 +1,6 @@
 # This is here for loader testing purposes only, use other datasets for realistic test data
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: glove-200-angular
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/glove-25-angular.yml b/jvector-examples/yaml-configs/index-parameters/glove-25-angular.yml
index bc2293a9d..e25426f0f 100644
--- a/jvector-examples/yaml-configs/index-parameters/glove-25-angular.yml
+++ b/jvector-examples/yaml-configs/index-parameters/glove-25-angular.yml
@@ -1,6 +1,6 @@
 # This is here for loader testing purposes only, use other datasets for realistic test data
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: glove-25-angular
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/glove-50-angular.yml b/jvector-examples/yaml-configs/index-parameters/glove-50-angular.yml
index 309ef9769..cde4630f9 100644
--- a/jvector-examples/yaml-configs/index-parameters/glove-50-angular.yml
+++ b/jvector-examples/yaml-configs/index-parameters/glove-50-angular.yml
@@ -1,6 +1,6 @@
 # This is here for loader testing purposes only, use other datasets for realistic test data
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: glove-50-angular
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/lastfm-64-dot.yml b/jvector-examples/yaml-configs/index-parameters/lastfm-64-dot.yml
index c2e2fb98a..5ac19c195 100644
--- a/jvector-examples/yaml-configs/index-parameters/lastfm-64-dot.yml
+++ b/jvector-examples/yaml-configs/index-parameters/lastfm-64-dot.yml
@@ -1,6 +1,6 @@
 # This is here for loader testing purposes only, use other datasets for realistic test data
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: lastfm-64-dot
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/nytimes-256-angular.yml b/jvector-examples/yaml-configs/index-parameters/nytimes-256-angular.yml
index 4e2db21a7..50e1ba072 100644
--- a/jvector-examples/yaml-configs/index-parameters/nytimes-256-angular.yml
+++ b/jvector-examples/yaml-configs/index-parameters/nytimes-256-angular.yml
@@ -1,6 +1,6 @@
 # This is here for loader testing purposes only, use other datasets for realistic test data
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: nytimes-256-angular
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/sift-128-euclidean.yml b/jvector-examples/yaml-configs/index-parameters/sift-128-euclidean.yml
index 94362ec70..93569a009 100644
--- a/jvector-examples/yaml-configs/index-parameters/sift-128-euclidean.yml
+++ b/jvector-examples/yaml-configs/index-parameters/sift-128-euclidean.yml
@@ -1,6 +1,6 @@
 # This is here for loader testing purposes only, use other datasets for realistic test data
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: sift-128-euclidean
 useDatasetPrefetching: false
diff --git a/jvector-examples/yaml-configs/index-parameters/wiki-multilingual-v3-int8-1m.yml b/jvector-examples/yaml-configs/index-parameters/wiki-multilingual-v3-int8-1m.yml
index d7692b697..e7d98b7dc 100644
--- a/jvector-examples/yaml-configs/index-parameters/wiki-multilingual-v3-int8-1m.yml
+++ b/jvector-examples/yaml-configs/index-parameters/wiki-multilingual-v3-int8-1m.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: wiki-multilingual-v3-int8-1m
 
diff --git a/jvector-examples/yaml-configs/index-parameters/wikipedia-2023-11-en-mxbai-int8-1m.yml b/jvector-examples/yaml-configs/index-parameters/wikipedia-2023-11-en-mxbai-int8-1m.yml
index 02978921f..23b470734 100644
--- a/jvector-examples/yaml-configs/index-parameters/wikipedia-2023-11-en-mxbai-int8-1m.yml
+++ b/jvector-examples/yaml-configs/index-parameters/wikipedia-2023-11-en-mxbai-int8-1m.yml
@@ -1,5 +1,5 @@
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 dataset: wikipedia-2023-11-en-mxbai-int8-1m
 
diff --git a/jvector-examples/yaml-configs/run-config.yml b/jvector-examples/yaml-configs/run-config.yml
index ba5ee1077..04dd1e160 100644
--- a/jvector-examples/yaml-configs/run-config.yml
+++ b/jvector-examples/yaml-configs/run-config.yml
@@ -1,6 +1,6 @@
 # Run-level controls for BenchYAML (applies to the whole invocation)
 yamlSchemaVersion: 1
-onDiskIndexVersion: 6
+onDiskIndexVersion: 7
 
 # Benchmark stats to compute
 benchmarks:
diff --git a/jvector-tests/src/test/java/io/github/jbellis/jvector/example/TestDatasetPrefetching.java b/jvector-tests/src/test/java/io/github/jbellis/jvector/example/TestDatasetPrefetching.java
index 5379cb0ef..af6f85f4f 100644
--- a/jvector-tests/src/test/java/io/github/jbellis/jvector/example/TestDatasetPrefetching.java
+++ b/jvector-tests/src/test/java/io/github/jbellis/jvector/example/TestDatasetPrefetching.java
@@ -49,18 +49,18 @@ private MultiConfig config(String build, String search, boolean fused, String re
     @Test public void yamlDefaultsToResidentAndOptInIsParsed() throws Exception {
         var file = Files.createTempFile("prefetch-flag", ".yml");
         try {
-            Files.writeString(file, "yamlSchemaVersion: 1\nonDiskIndexVersion: 6\n");
+            Files.writeString(file, "yamlSchemaVersion: 1\nonDiskIndexVersion: " + OnDiskGraphIndex.CURRENT_VERSION + "\n");
             assertFalse(MultiConfig.getConfig(file.toString()).useDatasetPrefetching);
-            Files.writeString(file, "yamlSchemaVersion: 1\nonDiskIndexVersion: 6\nuseDatasetPrefetching: false\n");
+            Files.writeString(file, "yamlSchemaVersion: 1\nonDiskIndexVersion: " + OnDiskGraphIndex.CURRENT_VERSION + "\nuseDatasetPrefetching: false\n");
             assertFalse(MultiConfig.getConfig(file.toString()).useDatasetPrefetching);
-            Files.writeString(file, "yamlSchemaVersion: 1\nonDiskIndexVersion: 6\nuseDatasetPrefetching: true\n");
+            Files.writeString(file, "yamlSchemaVersion: 1\nonDiskIndexVersion: " + OnDiskGraphIndex.CURRENT_VERSION + "\nuseDatasetPrefetching: true\n");
             assertTrue(MultiConfig.getConfig(file.toString()).useDatasetPrefetching);
         } finally { Files.delete(file); }
     }
     @Test public void datasetPrefetchingAndCompactionOptionsAreIndependent() throws Exception {
         var file = Files.createTempFile("prefetch-compaction-flags", ".yml");
         try {
-            String common = "yamlSchemaVersion: 1\nonDiskIndexVersion: 6\nuseDatasetPrefetching: true\n";
+            String common = "yamlSchemaVersion: 1\nonDiskIndexVersion: " + OnDiskGraphIndex.CURRENT_VERSION + "\nuseDatasetPrefetching: true\n";
             Files.writeString(file, common);
             var config = MultiConfig.getConfig(file.toString());
             assertTrue(config.useDatasetPrefetching);
@@ -78,7 +78,7 @@ private MultiConfig config(String build, String search, boolean fused, String re
     @Test public void versionedYamlRejectsUnknownSettings() throws Exception {
         var file = Files.createTempFile("prefetch-unknown-setting", ".yml");
         try {
-            Files.writeString(file, "yamlSchemaVersion: 1\nonDiskIndexVersion: 6\nuseDatasetPrefetching: false\nunknownSetting: true\n");
+            Files.writeString(file, "yamlSchemaVersion: 1\nonDiskIndexVersion: " + OnDiskGraphIndex.CURRENT_VERSION + "\nuseDatasetPrefetching: false\nunknownSetting: true\n");
             assertThrows(org.yaml.snakeyaml.error.YAMLException.class,
                     () -> MultiConfig.getConfig(file.toString()));
         } finally { Files.delete(file); }
diff --git a/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestFeatureHeaderVersion.java b/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestFeatureHeaderVersion.java
new file mode 100644
index 000000000..8f9be0f12
--- /dev/null
+++ b/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestFeatureHeaderVersion.java
@@ -0,0 +1,111 @@
+/*
+ * Copyright DataStax, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.github.jbellis.jvector.graph.disk;
+
+import com.carrotsearch.randomizedtesting.RandomizedTest;
+import com.carrotsearch.randomizedtesting.annotations.ThreadLeakScope;
+import io.github.jbellis.jvector.TestUtil;
+import io.github.jbellis.jvector.disk.ByteBufferIndexWriter;
+import io.github.jbellis.jvector.disk.IndexWriter;
+import io.github.jbellis.jvector.graph.ListRandomAccessVectorValues;
+import io.github.jbellis.jvector.graph.disk.feature.Feature;
+import io.github.jbellis.jvector.graph.disk.feature.FeatureId;
+import io.github.jbellis.jvector.graph.disk.feature.FusedPQ;
+import io.github.jbellis.jvector.graph.disk.feature.NVQ;
+import io.github.jbellis.jvector.graph.disk.feature.SeparatedNVQ;
+import io.github.jbellis.jvector.quantization.NVQuantization;
+import io.github.jbellis.jvector.quantization.ProductQuantization;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.EnumMap;
+import java.util.List;
+
+import static org.junit.Assert.assertArrayEquals;
+
+/**
+ * A feature header embedded in a graph serializes its compressor at the graph's version, not at
+ * {@link OnDiskGraphIndex#CURRENT_VERSION}, so a graph written at an older version is laid out as
+ * that version wrote it.
+ */
+@ThreadLeakScope(ThreadLeakScope.Scope.NONE)
+public class TestFeatureHeaderVersion extends RandomizedTest {
+    private static final int DIMENSION = 32, MAX_DEGREE = 16;
+
+    private interface Body {
+        void write(IndexWriter out, int version) throws IOException;
+    }
+
+    @Test
+    public void featureHeadersAreWrittenAtTheGraphVersion() throws IOException {
+        var ravv = new ListRandomAccessVectorValues(TestUtil.createRandomVectors(512, DIMENSION), DIMENSION);
+        var pq = ProductQuantization.compute(ravv, 8, 256, false);
+        var nvq = NVQuantization.compute(ravv, 2);
+
+        // Each feature's header is its compressor at the graph's version, plus any fields of its own.
+        var cases = List.of(
+                new Case(FeatureId.FUSED_PQ, new FusedPQ(MAX_DEGREE, pq), pq::write),
+                new Case(FeatureId.NVQ_VECTORS, new NVQ(nvq), nvq::write),
+                new Case(FeatureId.SEPARATED_NVQ, new SeparatedNVQ(nvq, 1234L), (out, v) -> {
+                    nvq.write(out, v);
+                    out.writeLong(1234L);
+                }));
+
+        for (int version = 2; version <= OnDiskGraphIndex.CURRENT_VERSION; version++) {
+            var format = GraphIndexFormatFactory.forVersion(version);
+            for (var c : cases) {
+                if (!format.getSupportedFeatures().contains(c.id)) continue;
+                var features = new EnumMap<FeatureId, Feature>(FeatureId.class);
+                features.put(c.id, c.feature);
+                byte[] written = bytes(out -> format.writeHeaderFeatures(out, features));
+                int v = version;
+                byte[] expected = bytes(out -> c.body.write(out, v));
+                // The format's own framing (feature ids, counts) precedes the header.
+                byte[] header = Arrays.copyOfRange(written, written.length - expected.length, written.length);
+                assertArrayEquals(c.id + " at version " + version, expected, header);
+            }
+        }
+    }
+
+    private static final class Case {
+        final FeatureId id;
+        final Feature feature;
+        final Body body;
+
+        Case(FeatureId id, Feature feature, Body body) {
+            this.id = id;
+            this.feature = feature;
+            this.body = body;
+        }
+    }
+
+    private interface Writes {
+        void to(IndexWriter out) throws IOException;
+    }
+
+    private static byte[] bytes(Writes writes) throws IOException {
+        try (var out = ByteBufferIndexWriter.create(1024 * 1024, false)) {
+            writes.to(out);
+            ByteBuffer data = out.getWrittenData();
+            byte[] result = new byte[data.remaining()];
+            data.get(result);
+            return result;
+        }
+    }
+}
diff --git a/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestGraphIndexFormatFactory.java b/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestGraphIndexFormatFactory.java
index a3296937a..67d15e0f1 100644
--- a/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestGraphIndexFormatFactory.java
+++ b/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestGraphIndexFormatFactory.java
@@ -89,7 +89,7 @@ public void testFormatCharacteristicsPerVersion() {
         assertFalse(v2.usesFooter());
         assertEquals(EnumSet.of(FeatureId.INLINE_VECTORS), v2.getSupportedFeatures());
 
-        // versions 3-5 support every feature except FUSED_PQ and INLINE_BYTE_VECTORS (both v6+);
+        // versions 3-5 support every feature except FUSED_PQ (v6+) and INLINE_BYTE_VECTORS (v7+);
         // multi-layer arrives at v4, footer-based metadata arrives at v5.
         var nonFused = EnumSet.complementOf(EnumSet.of(FeatureId.FUSED_PQ, FeatureId.INLINE_BYTE_VECTORS));
         for (int version : new int[]{3, 4, 5}) {
@@ -104,7 +104,15 @@ public void testFormatCharacteristicsPerVersion() {
         assertTrue(v6.supportsMultiLayer());
         assertTrue(v6.usesFooter());
         assertTrue(v6.supportsFeature(FeatureId.FUSED_PQ));
-        assertEquals(EnumSet.allOf(FeatureId.class), v6.getSupportedFeatures());
+        assertFalse(v6.supportsFeature(FeatureId.INLINE_BYTE_VECTORS));
+        assertEquals(EnumSet.complementOf(EnumSet.of(FeatureId.INLINE_BYTE_VECTORS)), v6.getSupportedFeatures());
+
+        var v7 = GraphIndexFormatFactory.forVersion(7);
+        assertTrue(v7.supportsMultiLayer());
+        assertTrue(v7.usesFooter());
+        assertTrue(v7.supportsFeature(FeatureId.FUSED_PQ));
+        assertTrue(v7.supportsFeature(FeatureId.INLINE_BYTE_VECTORS));
+        assertEquals(EnumSet.allOf(FeatureId.class), v7.getSupportedFeatures());
     }
 
     @Test
diff --git a/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestOnDiskGraphIndex.java b/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestOnDiskGraphIndex.java
index f9c505b4e..d82c4e0b4 100644
--- a/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestOnDiskGraphIndex.java
+++ b/jvector-tests/src/test/java/io/github/jbellis/jvector/graph/disk/TestOnDiskGraphIndex.java
@@ -662,6 +662,17 @@ public void testInlineByteVectorsFeatureSize() {
         }
     }
 
+    @Test
+    public void testInlineByteVectorsRequiresVersion7() {
+        var graph = new TestUtil.RandomlyConnectedGraphIndex(32, 4, getRandom());
+        var e = assertThrows(IllegalArgumentException.class, () -> new OnDiskGraphIndexWriter.Builder(graph,
+                testDirectory.resolve("version_6_inline_byte_vectors"))
+                .withVersion(6)
+                .with(new InlineByteVectors(8))
+                .build());
+        assertTrue(e.getMessage(), e.getMessage().startsWith("Feature INLINE_BYTE_VECTORS is not supported by version 6"));
+    }
+
     /**
      * getByteVector throws UnsupportedOperationException when the graph has no INLINE_BYTE_VECTORS feature.
      */