diff --git a/Changes b/Changes
index 3cf53bb..480e77e 100644
--- a/Changes
+++ b/Changes
@@ -1,7 +1,8 @@
-0.65 2026-05-12
-includes all changes in 0.64.7
+0.65.1 2026-06-10
+    - [feature] Prevent indexation of documents without
+      a token stream (diewald; AI-assisted Claude Opus 4.6)
 
-0.64.7 2026-05-07
+0.65 2026-05-12
     - [bugfix] Keep highlights that extend beyond a cut match
       (diewald; fixes #177; diewald; AI-assisted Claude Opus 4.6)
     - [bugfix] Correctly handle foundry and layer in attribute groups
diff --git a/pom.xml b/pom.xml
index 287e281..36beae8 100644
--- a/pom.xml
+++ b/pom.xml
@@ -35,7 +35,7 @@
 
   <groupId>de.ids-mannheim.korap.krill</groupId>
   <artifactId>Krill</artifactId>
-  <version>0.65</version>
+  <version>0.65.1</version>
   <packaging>jar</packaging>
 
   <name>Krill</name>
diff --git a/src/main/java/de/ids_mannheim/korap/KrillIndex.java b/src/main/java/de/ids_mannheim/korap/KrillIndex.java
index 0bcd1cd..0b673e9 100644
--- a/src/main/java/de/ids_mannheim/korap/KrillIndex.java
+++ b/src/main/java/de/ids_mannheim/korap/KrillIndex.java
@@ -496,6 +496,15 @@
         if (doc == null)
             return doc;
 
+        if (!hasTokenField(doc)) {
+            log.error(
+                "Rejecting upsert for document '{}': no token stream - "
+                + "existing document (if any) will not be removed",
+                doc.getTextSigle()
+            );
+            return doc;
+        }
+
         // Create a filter based on the corpusID and the docID
         String textSigle = doc.getTextSigle();
         KrillDate current = new KrillDate(LocalDate.now());
@@ -608,6 +617,26 @@
     
 
     /**
+     * Check if a FieldDocument has a known token stream field.
+     * Checks for "tokens" first (current KorAP-XML-Krill format),
+     * then falls back to "base" (legacy format).
+     * A document without either field will not contribute
+     * to token/sentence/paragraph statistics and cannot be searched.
+     *
+     * @param doc The FieldDocument to check
+     * @return true if the document has a known token field with term vectors
+     */
+    public boolean hasTokenField (FieldDocument doc) {
+        if (doc == null)
+            return false;
+        IndexableField field = doc.doc.getField("tokens");
+        if (field == null)
+            field = doc.doc.getField("base");
+        return field != null && field.fieldType().storeTermVectors();
+    }
+
+
+    /**
      * Add a document to the index as a {@link FieldDocument}.
      * 
      * @param doc
@@ -619,6 +648,16 @@
         if (doc == null)
             return doc;
 
+        if (!hasTokenField(doc)) {
+            log.error(
+                "Rejecting document '{}': no token stream - "
+                + "the document would not contribute to statistics "
+                + "and cannot be searched",
+                doc.getTextSigle()
+            );
+            return doc;
+        }
+
         try {
 
             // Add document to writer
diff --git a/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionIndex.java b/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionIndex.java
index 8b5fcef..eaaba0a 100644
--- a/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/collection/TestKrillCollectionIndex.java
@@ -1296,6 +1296,8 @@
         for (int i = 0; i < 6000; i++) {
             FieldDocument fd = new FieldDocument();
             fd.addString("UID", Integer.toString(i));
+            fd.addTV("tokens", "x",
+                "[(0-1)s:x|_0$<i>0<i>1|-:tokens$<i>1]");
             ki.addDoc(fd);
             if (i == 4500)
                 ki.commit();
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestFieldDocument.java b/src/test/java/de/ids_mannheim/korap/index/TestFieldDocument.java
index a7b3777..f4b3c2c 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestFieldDocument.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestFieldDocument.java
@@ -637,6 +637,245 @@
     };
 
 
+    /**
+     * A document with only metadata (no token stream / no "data" section)
+     * should be rejected by addDoc with an error.
+     */
+    @Test
+    public void testAddDocRejectsMetadataOnlyDocument () throws Exception {
+        KrillIndex ki = new KrillIndex();
+
+        FieldDocument fd = new FieldDocument();
+        fd.addString("textSigle", "TEST/META/001");
+        fd.addString("author", "Test Author");
+        fd.addDate("pubDate", 20200101);
+
+        FieldDocument result = ki.addDoc(fd);
+        ki.commit();
+
+        assertEquals(0, ki.numberOf("documents"));
+        assertTrue(
+            "addDoc should return the doc even when rejected",
+            result != null
+        );
+    }
+
+    /**
+     * A document with only metadata should also be rejected via upsertDoc.
+     */
+    @Test
+    public void testUpsertDocRejectsMetadataOnlyDocument () throws Exception {
+        KrillIndex ki = new KrillIndex();
+
+        FieldDocument fd = new FieldDocument();
+        fd.addString("textSigle", "TEST/META/002");
+        fd.addString("author", "Test Author");
+
+        FieldDocument result = ki.upsertDoc(fd);
+        ki.commit();
+
+        assertEquals(0, ki.numberOf("documents"));
+    }
+
+    /**
+     * A JSON document with fields but no data section should be rejected.
+     */
+    @Test
+    public void testAddDocRejectsJsonWithoutTokenStream () throws Exception {
+        String json = "{"
+            + "  \"fields\" : ["
+            + "    {"
+            + "      \"@type\" : \"koral:field\","
+            + "      \"type\" : \"type:string\","
+            + "      \"key\" : \"textSigle\","
+            + "      \"value\" : \"TEST/NODATA/001\""
+            + "    },"
+            + "    {"
+            + "      \"@type\" : \"koral:field\","
+            + "      \"type\" : \"type:text\","
+            + "      \"key\" : \"author\","
+            + "      \"value\" : \"Nobody\""
+            + "    },"
+            + "    {"
+            + "      \"@type\" : \"koral:field\","
+            + "      \"type\" : \"type:date\","
+            + "      \"key\" : \"pubDate\","
+            + "      \"value\" : \"2020-01-01\""
+            + "    }"
+            + "  ]"
+            + "}";
+
+        KrillIndex ki = new KrillIndex();
+        FieldDocument fd = ki.addDoc(json);
+        ki.commit();
+
+        assertEquals(
+            "Metadata-only document should not be indexed",
+            0, ki.numberOf("documents")
+        );
+    }
+
+    /**
+     * A document with a token stream on an unknown field name
+     * (neither "tokens" nor "base") should be rejected.
+     */
+    @Test
+    public void testAddDocRejectsUnknownTokenFieldName () throws Exception {
+        KrillIndex ki = new KrillIndex();
+
+        FieldDocument fd = new FieldDocument();
+        fd.addString("textSigle", "TEST/WRONG/001");
+        fd.addTV("other", "hello world",
+            "[(0-5)s:hello|i:hello|_0$<i>0<i>5|-:tokens$<i>2]"
+            + "[(6-11)s:world|i:world|_1$<i>6<i>11]");
+        ki.addDoc(fd);
+        ki.commit();
+
+        assertEquals(
+            "Document with token stream on unknown field should be rejected",
+            0, ki.numberOf("documents")
+        );
+    }
+
+    /**
+     * A document with a token stream on the legacy "base" field
+     * should be accepted.
+     */
+    @Test
+    public void testAddDocAcceptsLegacyBaseField () throws Exception {
+        KrillIndex ki = new KrillIndex();
+
+        FieldDocument fd = new FieldDocument();
+        fd.addString("textSigle", "TEST/BASE/001");
+        fd.addTV("base", "hello world",
+            "[(0-5)s:hello|i:hello|_0$<i>0<i>5|-:t$<i>2]"
+            + "[(6-11)s:world|i:world|_1$<i>6<i>11]");
+        ki.addDoc(fd);
+        ki.commit();
+
+        assertEquals(
+            "Document with legacy 'base' field should be accepted",
+            1, ki.numberOf("documents")
+        );
+    }
+
+    /**
+     * When metadata-only documents are mixed with proper documents,
+     * only proper documents should be indexed and contribute to stats.
+     */
+    @Test
+    public void testStatsWithMixedValidAndMetadataOnlyDocuments () throws Exception {
+        KrillIndex ki = new KrillIndex();
+
+        // Valid document with token stream
+        FieldDocument fd1 = new FieldDocument();
+        fd1.addString("textSigle", "TEST/OK/001");
+        fd1.addString("author", "Good Author");
+        fd1.addTV("tokens", "hello world",
+            "[(0-5)s:hello|i:hello|_0$<i>0<i>5|-:tokens$<i>2]"
+            + "[(6-11)s:world|i:world|_1$<i>6<i>11]");
+        ki.addDoc(fd1);
+
+        // Metadata-only document (should be rejected)
+        FieldDocument fd2 = new FieldDocument();
+        fd2.addString("textSigle", "TEST/BAD/001");
+        fd2.addString("author", "Bad Author");
+        ki.addDoc(fd2);
+
+        // Another valid document
+        FieldDocument fd3 = new FieldDocument();
+        fd3.addString("textSigle", "TEST/OK/002");
+        fd3.addString("author", "Another Author");
+        fd3.addTV("tokens", "foo bar baz",
+            "[(0-3)s:foo|i:foo|_0$<i>0<i>3|-:tokens$<i>3]"
+            + "[(4-7)s:bar|i:bar|_1$<i>4<i>7]"
+            + "[(8-11)s:baz|i:baz|_2$<i>8<i>11]");
+        ki.addDoc(fd3);
+
+        ki.commit();
+
+        assertEquals(
+            "Only valid documents should be counted",
+            2, ki.numberOf("documents")
+        );
+        assertEquals(5, ki.numberOf("tokens"));
+    }
+
+    /**
+     * A document with an empty stream (data section present but stream
+     * is empty) has a token stream field but no tokens. This is allowed
+     * through indexing since the document structure is valid (it has a
+     * "data" section), but it contributes 0 to token statistics.
+     */
+    @Test
+    public void testAddDocAcceptsEmptyTokenStream () throws Exception {
+        String json = "{"
+            + "  \"data\" : {"
+            + "    \"text\" : \"\","
+            + "    \"name\" : \"tokens\","
+            + "    \"stream\" : []"
+            + "  },"
+            + "  \"fields\" : ["
+            + "    {"
+            + "      \"@type\" : \"koral:field\","
+            + "      \"type\" : \"type:string\","
+            + "      \"key\" : \"textSigle\","
+            + "      \"value\" : \"TEST/EMPTY/001\""
+            + "    }"
+            + "  ]"
+            + "}";
+
+        KrillIndex ki = new KrillIndex();
+        FieldDocument fd = ki.addDoc(json);
+        ki.commit();
+
+        assertEquals(
+            "Document with empty stream is accepted (has token field)",
+            1, ki.numberOf("documents")
+        );
+        assertEquals(
+            "Empty stream contributes 0 tokens",
+            0, ki.numberOf("tokens")
+        );
+    }
+
+    /**
+     * Upserting a valid document with a metadata-only replacement should
+     * NOT remove the original and should reject the new one.
+     */
+    @Test
+    public void testUpsertDoesNotReplaceValidDocWithMetadataOnly () throws Exception {
+        KrillIndex ki = new KrillIndex();
+
+        // First: add a valid document
+        FieldDocument fd1 = new FieldDocument();
+        fd1.addString("textSigle", "TEST/UPSERT/001");
+        fd1.addString("author", "Original");
+        fd1.addTV("tokens", "good data",
+            "[(0-4)s:good|i:good|_0$<i>0<i>4|-:tokens$<i>2]"
+            + "[(5-9)s:data|i:data|_1$<i>5<i>9]");
+        ki.addDoc(fd1);
+        ki.commit();
+
+        assertEquals(1, ki.numberOf("documents"));
+        assertEquals(2, ki.numberOf("tokens"));
+
+        // Now try to upsert with metadata-only (should be rejected)
+        FieldDocument fd2 = new FieldDocument();
+        fd2.addString("textSigle", "TEST/UPSERT/001");
+        fd2.addString("author", "Replacement Without Tokens");
+        ki.upsertDoc(fd2);
+        ki.commit();
+
+        // The original document should still be there since the upsert
+        // was rejected before the delete could happen
+        assertEquals(1, ki.numberOf("documents"));
+        assertEquals(2, ki.numberOf("tokens"));
+
+        MetaFields mfs = ki.getFields("TEST/UPSERT/001");
+        assertEquals("Original", mfs.getFieldValue("author"));
+    }
+
     @Test
     public void indexUpsert () throws Exception {
         KrillIndex ki = new KrillIndex();
@@ -645,6 +884,8 @@
         FieldDocument fd = new FieldDocument();
         fd.addString("textSigle", "AAA/BBB/001");
         fd.addString("content", "Example1");
+        fd.addTV("tokens", "Example1",
+            "[(0-8)s:Example1|i:example1|_0$<i>0<i>8|-:tokens$<i>1]");
         ki.upsertDoc(fd);
         ki.commit();
 
@@ -662,6 +903,8 @@
         fd = new FieldDocument();
         fd.addString("textSigle", "AAA/BBB/002");
         fd.addString("content", "Example2");
+        fd.addTV("tokens", "Example2",
+            "[(0-8)s:Example2|i:example2|_0$<i>0<i>8|-:tokens$<i>1]");
 
         ki.upsertDoc(fd);
         ki.commit();
@@ -675,6 +918,8 @@
         fd = new FieldDocument();
         fd.addString("textSigle", "AAA/BBB/001");
         fd.addString("content", "Example3");
+        fd.addTV("tokens", "Example3",
+            "[(0-8)s:Example3|i:example3|_0$<i>0<i>8|-:tokens$<i>1]");
 
         ki.upsertDoc(fd);
         ki.commit();
@@ -696,6 +941,8 @@
         fd = new FieldDocument();
         fd.addString("textSigle", "AAA/DDD/005");
         fd.addString("content", "Example4");
+        fd.addTV("tokens", "Example4",
+            "[(0-8)s:Example4|i:example4|_0$<i>0<i>8|-:tokens$<i>1]");
         
         ki.upsertDoc(fd);
         ki.commit();
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestKrillIndex.java b/src/test/java/de/ids_mannheim/korap/index/TestKrillIndex.java
index e6c7d93..a301544 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestKrillIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestKrillIndex.java
@@ -114,12 +114,16 @@
 
         FieldDocument fd = new FieldDocument();
         fd.addString("name", "Peter");
+        fd.addTV("tokens", "x",
+            "[(0-1)s:x|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.addDoc(fd);
 
         assertEquals(0, ki.numberOf("base", "documents"));
 
         fd = new FieldDocument();
         fd.addString("name", "Michael");
+        fd.addTV("tokens", "y",
+            "[(0-1)s:y|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.addDoc(fd);
 
         assertEquals(0, ki.numberOf("base", "documents"));
@@ -170,11 +174,15 @@
         FieldDocument fd = new FieldDocument();
         fd.addText("title", "Peter");
         fd.setUID(22);
+        fd.addTV("tokens", "x",
+            "[(0-1)s:x|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.addDoc(fd);
 
         fd = new FieldDocument();
         fd.addText("title", "Akron");
         fd.setUID("05678");
+        fd.addTV("tokens", "y",
+            "[(0-1)s:y|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.addDoc(fd);
 
         ki.commit();
@@ -211,6 +219,8 @@
 
 		fd.addText("title", "Der Name der Rose");
 
+        fd.addTV("tokens", "x",
+            "[(0-1)s:x|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.addDoc(fd);
 
         /* Save documents */
@@ -335,6 +345,8 @@
         FieldDocument fd = new FieldDocument();
         fd.addString("name", "Peter");
         fd.addString("textSigle", "a/b/c");
+        fd.addTV("tokens", "x",
+            "[(0-1)s:x|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.upsertDoc(fd);
 
         /* Save documents */
@@ -343,6 +355,8 @@
         fd = new FieldDocument();
         fd.addString("name", "Frank");
         fd.addString("textSigle", "a/b/d");
+        fd.addTV("tokens", "y",
+            "[(0-1)s:y|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.upsertDoc(fd);
 
         /* Save documents */
@@ -351,6 +365,8 @@
         fd = new FieldDocument();
         fd.addString("name", "Franz");
         fd.addString("textSigle", "a/b/c");
+        fd.addTV("tokens", "z",
+            "[(0-1)s:z|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.upsertDoc(fd);
 
         /* Save documents */
@@ -384,11 +400,15 @@
 
         FieldDocument fd = new FieldDocument();
         fd.addString("textSigle", "aaaa");
+        fd.addTV("tokens", "x",
+            "[(0-1)s:x|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.addDoc(fd);
 
         fd = new FieldDocument();
         fd.addString("textSigle", "bbbb");
         fd.setUID("05678");
+        fd.addTV("tokens", "y",
+            "[(0-1)s:y|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.addDoc(fd);
 
         ki.commit();
@@ -413,6 +433,8 @@
         
         fd = new FieldDocument();
         fd.addString("textSigle", "cccc");
+        fd.addTV("tokens", "z",
+            "[(0-1)s:z|_0$<i>0<i>1|-:tokens$<i>1]");
         ki.addDoc(fd);
 
         ki.commit();
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestPrimaryDataProtection.java b/src/test/java/de/ids_mannheim/korap/index/TestPrimaryDataProtection.java
index 11a6421..191ced2 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestPrimaryDataProtection.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestPrimaryDataProtection.java
@@ -385,6 +385,10 @@
         fd.addString("textSigle", "TST-004-0001");
         fd.addText("title", "Custom Field Document");
         fd.setUID(45);
+        fd.addTV("tokens", "some indexed text",
+                "[(0-4)s:some|_0#0-4|-:t$<i>3]"
+                + "[(5-12)s:indexed|_1#5-12]"
+                + "[(13-17)s:text|_2#13-17]");
         fd.addTV("customTokens", "leaked custom text",
                 "[(0-6)s:leaked|_0#0-6|-:t$<i>3]"
                 + "[(7-13)s:custom|_1#7-13]"
diff --git a/src/test/java/de/ids_mannheim/korap/search/TestVcField.java b/src/test/java/de/ids_mannheim/korap/search/TestVcField.java
index 1a4ed72..f843bef 100644
--- a/src/test/java/de/ids_mannheim/korap/search/TestVcField.java
+++ b/src/test/java/de/ids_mannheim/korap/search/TestVcField.java
@@ -24,6 +24,8 @@
         FieldDocument fd = new FieldDocument();
         fd.addString("textSigle", textSigle);
         fd.setUID(uid);
+        fd.addTV("tokens", "x",
+            "[(0-1)s:x|_0$<i>0<i>1|-:tokens$<i>1]");
         return fd;
     }