diff --git a/docs/changelog/125599.yaml b/docs/changelog/125599.yaml
new file mode 100644
index 0000000000000..e0057f50dd937
--- /dev/null
+++ b/docs/changelog/125599.yaml
@@ -0,0 +1,6 @@
+pr: 125599
+summary: Allow zero for `rescore_vector.oversample` to indicate by-passing oversample
+  and rescoring
+area: Vector Search
+type: enhancement
+issues: []
diff --git a/docs/reference/elasticsearch/mapping-reference/dense-vector.md b/docs/reference/elasticsearch/mapping-reference/dense-vector.md
index 346355802562d..46ba23a1050b9 100644
--- a/docs/reference/elasticsearch/mapping-reference/dense-vector.md
+++ b/docs/reference/elasticsearch/mapping-reference/dense-vector.md
@@ -291,7 +291,7 @@ $$$dense-vector-index-options$$$
     :   (Optional, object) Functionality in [preview]. An optional section that configures automatic vector rescoring on knn queries for the given field. Only applicable to quantized index types.
     :::::{dropdown} Properties of `rescore_vector`
     `oversample`
-    :   (required, float) The amount to oversample the search results by. This value should be greater than `1.0` and less than `10.0`. The higher the value, the more vectors will be gathered and rescored with the raw values per shard.
+    :   (required, float) The amount to oversample the search results by. This value should be greater than `1.0` and less than `10.0` or exactly `0` to indicate no oversampling & rescoring should occur. The higher the value, the more vectors will be gathered and rescored with the raw values per shard.
         :   In case a knn query specifies a `rescore_vector` parameter, the query `rescore_vector` parameter will be used instead.
         :   See [oversampling and rescoring quantized vectors](docs-content://solutions/search/vector/knn.md#dense-vector-knn-search-rescoring) for details.
         :::::
diff --git a/docs/reference/query-languages/query-dsl/query-dsl-knn-query.md b/docs/reference/query-languages/query-dsl/query-dsl-knn-query.md
index 3c9835700a4c5..99349a32aeff0 100644
--- a/docs/reference/query-languages/query-dsl/query-dsl-knn-query.md
+++ b/docs/reference/query-languages/query-dsl/query-dsl-knn-query.md
@@ -113,6 +113,7 @@ Rescoring only makes sense for quantized vectors; when [quantization](/reference
     * Retrieve `num_candidates` candidates per shard.
     * From these candidates, the top `k * oversample` candidates per shard will be rescored using the original vectors.
     * The top `k` rescored candidates will be returned.
+    Must be >= 1f to indicate oversample factor, or exactly `0` to indicate that no oversampling and rescoring should occur.
 
 
 See [oversampling and rescoring quantized vectors](docs-content://solutions/search/vector/knn.md#dense-vector-knn-search-rescoring) for details.
diff --git a/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_bbq_hnsw.yml b/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_bbq_hnsw.yml
index a64d28af2e765..4e1d64d651a84 100644
--- a/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_bbq_hnsw.yml
+++ b/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_bbq_hnsw.yml
@@ -337,3 +337,260 @@ setup:
   - match: { hits.hits.0._score: $rescore_score0 }
   - match: { hits.hits.1._score: $rescore_score1 }
   - match: { hits.hits.2._score: $rescore_score2 }
+---
+"Test index configured rescore vector updateable and settable to 0":
+  - requires:
+      cluster_features: ["mapper.dense_vector.rescore_zero_vector"]
+      reason: Needs rescore_zero_vector feature
+
+  - do:
+      indices.create:
+        index: bbq_rescore_0_hnsw
+        body:
+          settings:
+            index:
+              number_of_shards: 1
+          mappings:
+            properties:
+              vector:
+                type: dense_vector
+                index_options:
+                  type: bbq_hnsw
+                  rescore_vector:
+                    oversample: 0
+
+  - do:
+      indices.create:
+        index: bbq_rescore_update_hnsw
+        body:
+          settings:
+            index:
+              number_of_shards: 1
+          mappings:
+            properties:
+              vector:
+                type: dense_vector
+                index_options:
+                  type: bbq_hnsw
+                  rescore_vector:
+                    oversample: 1
+
+  - do:
+      indices.put_mapping:
+        index: bbq_rescore_update_hnsw
+        body:
+          properties:
+            vector:
+              type: dense_vector
+              index_options:
+                type: bbq_hnsw
+                rescore_vector:
+                  oversample: 0
+
+  - do:
+      indices.get_mapping:
+        index: bbq_rescore_update_hnsw
+
+  - match: { .bbq_rescore_update_hnsw.mappings.properties.vector.index_options.rescore_vector.oversample: 0 }
+---
+"Test index configured rescore vector score consistency":
+  - requires:
+      cluster_features: ["mapper.dense_vector.rescore_zero_vector"]
+      reason: Needs rescore_zero_vector feature
+  - skip:
+      features: "headers"
+  - do:
+      indices.create:
+        index: bbq_rescore_zero_hnsw
+        body:
+          settings:
+            index:
+              number_of_shards: 1
+          mappings:
+            properties:
+              vector:
+                type: dense_vector
+                dims: 64
+                index: true
+                similarity: max_inner_product
+                index_options:
+                  type: bbq_hnsw
+                  rescore_vector:
+                    oversample: 0
+
+  - do:
+      bulk:
+        index: bbq_rescore_zero_hnsw
+        refresh: true
+        body: |
+          { "index": {"_id": "1"}}
+          { "vector": [0.077,  0.32 , -0.205,  0.63 ,  0.032,  0.201,  0.167, -0.313, 0.176,  0.531, -0.375,  0.334, -0.046,  0.078, -0.349,  0.272, 0.307, -0.083,  0.504,  0.255, -0.404,  0.289, -0.226, -0.132, -0.216,  0.49 ,  0.039,  0.507, -0.307,  0.107,  0.09 , -0.265, -0.285,  0.336, -0.272,  0.369, -0.282,  0.086, -0.132,  0.475, -0.224,  0.203,  0.439,  0.064,  0.246, -0.396,  0.297,  0.242, -0.028,  0.321, -0.022, -0.009, -0.001  ,  0.031, -0.533,  0.45, -0.683,  1.331,  0.194, -0.157, -0.1  , -0.279, -0.098, -0.176] }
+          { "index": {"_id": "2"}}
+          { "vector": [0.196,  0.514,  0.039,  0.555, -0.042,  0.242,  0.463, -0.348, -0.08 ,  0.442, -0.067, -0.05 , -0.001,  0.298, -0.377,  0.048, 0.307,  0.159,  0.278,  0.119, -0.057,  0.333, -0.289, -0.438, -0.014,  0.361, -0.169,  0.292, -0.229,  0.123,  0.031, -0.138, -0.139,  0.315, -0.216,  0.322, -0.445, -0.059,  0.071,  0.429, -0.602, -0.142,  0.11 ,  0.192,  0.259, -0.241,  0.181, -0.166, 0.082,  0.107, -0.05 ,  0.155,  0.011,  0.161, -0.486,  0.569, -0.489,  0.901,  0.208,  0.011, -0.209, -0.153, -0.27 , -0.013] }
+          { "index": {"_id": "3"}}
+          { "vector": [0.196,  0.514,  0.039,  0.555, -0.042,  0.242,  0.463, -0.348, -0.08 ,  0.442, -0.067, -0.05 , -0.001,  0.298, -0.377,  0.048, 0.307,  0.159,  0.278,  0.119, -0.057,  0.333, -0.289, -0.438, -0.014,  0.361, -0.169,  0.292, -0.229,  0.123,  0.031, -0.138, -0.139,  0.315, -0.216,  0.322, -0.445, -0.059,  0.071,  0.429, -0.602, -0.142,  0.11 ,  0.192,  0.259, -0.241,  0.181, -0.166, 0.082,  0.107, -0.05 ,  0.155,  0.011,  0.161, -0.486,  0.569, -0.489,  0.901,  0.208,  0.011, -0.209, -0.153, -0.27 , -0.013] }
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: bbq_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [0.128,  0.067, -0.08 ,  0.395, -0.11 , -0.259,  0.473, -0.393,
+                           0.292,  0.571, -0.491,  0.444, -0.288,  0.198, -0.343,  0.015,
+                           0.232,  0.088,  0.228,  0.151, -0.136,  0.236, -0.273, -0.259,
+                           -0.217,  0.359, -0.207,  0.352, -0.142,  0.192, -0.061, -0.17 ,
+                           -0.343,  0.189, -0.221,  0.32 , -0.301, -0.1  ,  0.005,  0.232,
+                           -0.344,  0.136,  0.252,  0.157, -0.13 , -0.244,  0.193, -0.034,
+                           -0.12 , -0.193, -0.102,  0.252, -0.185, -0.167, -0.575,  0.582,
+                           -0.426,  0.983,  0.212,  0.204,  0.03 , -0.276, -0.425, -0.158]
+            k: 3
+            num_candidates: 3
+
+  - match: { hits.total: 3 }
+  - set: { hits.hits.0._score: raw_score0 }
+  - set: { hits.hits.1._score: raw_score1 }
+  - set: { hits.hits.2._score: raw_score2 }
+
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: bbq_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [0.128,  0.067, -0.08 ,  0.395, -0.11 , -0.259,  0.473, -0.393,
+                           0.292,  0.571, -0.491,  0.444, -0.288,  0.198, -0.343,  0.015,
+                           0.232,  0.088,  0.228,  0.151, -0.136,  0.236, -0.273, -0.259,
+                           -0.217,  0.359, -0.207,  0.352, -0.142,  0.192, -0.061, -0.17 ,
+                           -0.343,  0.189, -0.221,  0.32 , -0.301, -0.1  ,  0.005,  0.232,
+                           -0.344,  0.136,  0.252,  0.157, -0.13 , -0.244,  0.193, -0.034,
+                           -0.12 , -0.193, -0.102,  0.252, -0.185, -0.167, -0.575,  0.582,
+                           -0.426,  0.983,  0.212,  0.204,  0.03 , -0.276, -0.425, -0.158]
+            k: 3
+            num_candidates: 3
+            rescore_vector:
+              oversample: 2
+
+  - match: { hits.total: 3 }
+  - set: { hits.hits.0._score: override_score0 }
+  - set: { hits.hits.1._score: override_score1 }
+  - set: { hits.hits.2._score: override_score2 }
+
+  - do:
+      indices.put_mapping:
+        index: bbq_rescore_zero_hnsw
+        body:
+          properties:
+            vector:
+              type: dense_vector
+              dims: 64
+              index: true
+              similarity: max_inner_product
+              index_options:
+                type: bbq_hnsw
+                rescore_vector:
+                  oversample: 2
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: bbq_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [0.128,  0.067, -0.08 ,  0.395, -0.11 , -0.259,  0.473, -0.393,
+                           0.292,  0.571, -0.491,  0.444, -0.288,  0.198, -0.343,  0.015,
+                           0.232,  0.088,  0.228,  0.151, -0.136,  0.236, -0.273, -0.259,
+                           -0.217,  0.359, -0.207,  0.352, -0.142,  0.192, -0.061, -0.17 ,
+                           -0.343,  0.189, -0.221,  0.32 , -0.301, -0.1  ,  0.005,  0.232,
+                           -0.344,  0.136,  0.252,  0.157, -0.13 , -0.244,  0.193, -0.034,
+                           -0.12 , -0.193, -0.102,  0.252, -0.185, -0.167, -0.575,  0.582,
+                           -0.426,  0.983,  0.212,  0.204,  0.03 , -0.276, -0.425, -0.158]
+            k: 3
+            num_candidates: 3
+
+  - match: { hits.total: 3 }
+  - set: { hits.hits.0._score: default_rescore0 }
+  - set: { hits.hits.1._score: default_rescore1 }
+  - set: { hits.hits.2._score: default_rescore2 }
+
+  - do:
+      indices.put_mapping:
+        index: bbq_rescore_zero_hnsw
+        body:
+          properties:
+            vector:
+              type: dense_vector
+              dims: 64
+              index: true
+              similarity: max_inner_product
+              index_options:
+                type: bbq_hnsw
+                rescore_vector:
+                  oversample: 0
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: bbq_rescore_zero_hnsw
+        body:
+          query:
+            script_score:
+              query: {match_all: {} }
+              script:
+                source: "double similarity = dotProduct(params.query_vector, 'vector'); return similarity < 0 ? 1 / (1 + -1 * similarity) : similarity + 1"
+                params:
+                  query_vector: [0.128,  0.067, -0.08 ,  0.395, -0.11 , -0.259,  0.473, -0.393,
+                                 0.292,  0.571, -0.491,  0.444, -0.288,  0.198, -0.343,  0.015,
+                                 0.232,  0.088,  0.228,  0.151, -0.136,  0.236, -0.273, -0.259,
+                                 -0.217,  0.359, -0.207,  0.352, -0.142,  0.192, -0.061, -0.17 ,
+                                 -0.343,  0.189, -0.221,  0.32 , -0.301, -0.1  ,  0.005,  0.232,
+                                 -0.344,  0.136,  0.252,  0.157, -0.13 , -0.244,  0.193, -0.034,
+                                 -0.12 , -0.193, -0.102,  0.252, -0.185, -0.167, -0.575,  0.582,
+                                 -0.426,  0.983,  0.212,  0.204,  0.03 , -0.276, -0.425, -0.158]
+
+  # Compare scores as hit IDs may change depending on how things are distributed
+  - match: { hits.total: 3 }
+  - match: { hits.hits.0._score: $override_score0 }
+  - match: { hits.hits.0._score: $default_rescore0 }
+  - match: { hits.hits.1._score: $override_score1 }
+  - match: { hits.hits.1._score: $default_rescore1 }
+  - match: { hits.hits.2._score: $override_score2 }
+  - match: { hits.hits.2._score: $default_rescore2 }
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: bbq_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [0.128,  0.067, -0.08 ,  0.395, -0.11 , -0.259,  0.473, -0.393,
+                           0.292,  0.571, -0.491,  0.444, -0.288,  0.198, -0.343,  0.015,
+                           0.232,  0.088,  0.228,  0.151, -0.136,  0.236, -0.273, -0.259,
+                           -0.217,  0.359, -0.207,  0.352, -0.142,  0.192, -0.061, -0.17 ,
+                           -0.343,  0.189, -0.221,  0.32 , -0.301, -0.1  ,  0.005,  0.232,
+                           -0.344,  0.136,  0.252,  0.157, -0.13 , -0.244,  0.193, -0.034,
+                           -0.12 , -0.193, -0.102,  0.252, -0.185, -0.167, -0.575,  0.582,
+                           -0.426,  0.983,  0.212,  0.204,  0.03 , -0.276, -0.425, -0.158]
+            k: 3
+            num_candidates: 3
+
+  # Compare scores as hit IDs may change depending on how things are distributed
+  - match: { hits.total: 3 }
+  - match: { hits.hits.0._score: $raw_score0 }
+  - match: { hits.hits.1._score: $raw_score1 }
+  - match: { hits.hits.2._score: $raw_score2 }
diff --git a/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_byte_quantized.yml b/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_byte_quantized.yml
index fb45521cb47c6..a1ed9a2eca11b 100644
--- a/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_byte_quantized.yml
+++ b/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_byte_quantized.yml
@@ -629,8 +629,7 @@ setup:
             properties:
               vector:
                 type: dense_vector
-                dims: 64
-                index: true
+                dims: 4
                 similarity: max_inner_product
                 index_options:
                   type: int8_hnsw
@@ -643,12 +642,11 @@ setup:
         refresh: true
         body: |
           { "index": {"_id": "1"}}
-          { "vector": [0.077,  0.32 , -0.205,  0.63 ,  0.032,  0.201,  0.167, -0.313, 0.176,  0.531, -0.375,  0.334, -0.046,  0.078, -0.349,  0.272, 0.307, -0.083,  0.504,  0.255, -0.404,  0.289, -0.226, -0.132, -0.216,  0.49 ,  0.039,  0.507, -0.307,  0.107,  0.09 , -0.265, -0.285,  0.336, -0.272,  0.369, -0.282,  0.086, -0.132,  0.475, -0.224,  0.203,  0.439,  0.064,  0.246, -0.396,  0.297,  0.242, -0.028,  0.321, -0.022, -0.009, -0.001  ,  0.031, -0.533,  0.45, -0.683,  1.331,  0.194, -0.157, -0.1  , -0.279, -0.098, -0.176] }
+          { "vector":  [230.0, 300.33, -34.8988, 15.555] }
           { "index": {"_id": "2"}}
-          { "vector": [0.196,  0.514,  0.039,  0.555, -0.042,  0.242,  0.463, -0.348, -0.08 ,  0.442, -0.067, -0.05 , -0.001,  0.298, -0.377,  0.048, 0.307,  0.159,  0.278,  0.119, -0.057,  0.333, -0.289, -0.438, -0.014,  0.361, -0.169,  0.292, -0.229,  0.123,  0.031, -0.138, -0.139,  0.315, -0.216,  0.322, -0.445, -0.059,  0.071,  0.429, -0.602, -0.142,  0.11 ,  0.192,  0.259, -0.241,  0.181, -0.166, 0.082,  0.107, -0.05 ,  0.155,  0.011,  0.161, -0.486,  0.569, -0.489,  0.901,  0.208,  0.011, -0.209, -0.153, -0.27 , -0.013] }
+          { "vector":  [-0.5, 100.0, -13, 14.8] }
           { "index": {"_id": "3"}}
-          { "vector": [0.196,  0.514,  0.039,  0.555, -0.042,  0.242,  0.463, -0.348, -0.08 ,  0.442, -0.067, -0.05 , -0.001,  0.298, -0.377,  0.048, 0.307,  0.159,  0.278,  0.119, -0.057,  0.333, -0.289, -0.438, -0.014,  0.361, -0.169,  0.292, -0.229,  0.123,  0.031, -0.138, -0.139,  0.315, -0.216,  0.322, -0.445, -0.059,  0.071,  0.429, -0.602, -0.142,  0.11 ,  0.192,  0.259, -0.241,  0.181, -0.166, 0.082,  0.107, -0.05 ,  0.155,  0.011,  0.161, -0.486,  0.569, -0.489,  0.901,  0.208,  0.011, -0.209, -0.153, -0.27 , -0.013] }
-
+          { "vector":  [0.5, 111.3, -13.0, 14.8] }
   - do:
       headers:
         Content-Type: application/json
@@ -658,14 +656,7 @@ setup:
         body:
           knn:
             field: vector
-            query_vector: [0.128,  0.067, -0.08 ,  0.395, -0.11 , -0.259,  0.473, -0.393,
-                           0.292,  0.571, -0.491,  0.444, -0.288,  0.198, -0.343,  0.015,
-                           0.232,  0.088,  0.228,  0.151, -0.136,  0.236, -0.273, -0.259,
-                           -0.217,  0.359, -0.207,  0.352, -0.142,  0.192, -0.061, -0.17 ,
-                           -0.343,  0.189, -0.221,  0.32 , -0.301, -0.1  ,  0.005,  0.232,
-                           -0.344,  0.136,  0.252,  0.157, -0.13 , -0.244,  0.193, -0.034,
-                           -0.12 , -0.193, -0.102,  0.252, -0.185, -0.167, -0.575,  0.582,
-                           -0.426,  0.983,  0.212,  0.204,  0.03 , -0.276, -0.425, -0.158]
+            query_vector: [-0.5, 90.0, -10, 14.8]
             k: 3
             num_candidates: 3
 
@@ -679,6 +670,7 @@ setup:
         Content-Type: application/json
       search:
         rest_total_hits_as_int: true
+        index: int8_rescore_hnsw
         body:
           query:
             script_score:
@@ -686,17 +678,228 @@ setup:
               script:
                 source: "double similarity = dotProduct(params.query_vector, 'vector'); return similarity < 0 ? 1 / (1 + -1 * similarity) : similarity + 1"
                 params:
-                  query_vector: [0.128,  0.067, -0.08 ,  0.395, -0.11 , -0.259,  0.473, -0.393,
-                                 0.292,  0.571, -0.491,  0.444, -0.288,  0.198, -0.343,  0.015,
-                                 0.232,  0.088,  0.228,  0.151, -0.136,  0.236, -0.273, -0.259,
-                                 -0.217,  0.359, -0.207,  0.352, -0.142,  0.192, -0.061, -0.17 ,
-                                 -0.343,  0.189, -0.221,  0.32 , -0.301, -0.1  ,  0.005,  0.232,
-                                 -0.344,  0.136,  0.252,  0.157, -0.13 , -0.244,  0.193, -0.034,
-                                 -0.12 , -0.193, -0.102,  0.252, -0.185, -0.167, -0.575,  0.582,
-                                 -0.426,  0.983,  0.212,  0.204,  0.03 , -0.276, -0.425, -0.158]
+                  query_vector: [-0.5, 90.0, -10, 14.8]
 
   # Compare scores as hit IDs may change depending on how things are distributed
   - match: { hits.total: 3 }
   - match: { hits.hits.0._score: $rescore_score0 }
   - match: { hits.hits.1._score: $rescore_score1 }
   - match: { hits.hits.2._score: $rescore_score2 }
+---
+"Test index configured rescore vector updateable and settable to 0":
+  - requires:
+      cluster_features: ["mapper.dense_vector.rescore_zero_vector"]
+      reason: Needs rescore_zero_vector feature
+
+  - do:
+      indices.create:
+        index: int8_rescore_0_hnsw
+        body:
+          settings:
+            index:
+              number_of_shards: 1
+          mappings:
+            properties:
+              vector:
+                type: dense_vector
+                index_options:
+                  type: int8_hnsw
+                  rescore_vector:
+                    oversample: 0
+
+  - do:
+      indices.create:
+        index: int8_rescore_update_hnsw
+        body:
+          settings:
+            index:
+              number_of_shards: 1
+          mappings:
+            properties:
+              vector:
+                type: dense_vector
+                index_options:
+                  type: int8_hnsw
+                  rescore_vector:
+                    oversample: 1
+
+  - do:
+      indices.put_mapping:
+        index: int8_rescore_update_hnsw
+        body:
+          properties:
+            vector:
+              type: dense_vector
+              index_options:
+                type: int8_hnsw
+                rescore_vector:
+                  oversample: 0
+
+  - do:
+      indices.get_mapping:
+        index: int8_rescore_update_hnsw
+
+  - match: { .int8_rescore_update_hnsw.mappings.properties.vector.index_options.rescore_vector.oversample: 0 }
+---
+"Test index configured rescore vector score consistency":
+  - requires:
+      cluster_features: ["mapper.dense_vector.rescore_zero_vector"]
+      reason: Needs rescore_zero_vector feature
+  - skip:
+      features: "headers"
+  - do:
+      indices.create:
+        index: int8_rescore_zero_hnsw
+        body:
+          settings:
+            index:
+              number_of_shards: 1
+          mappings:
+            properties:
+              vector:
+                type: dense_vector
+                similarity: max_inner_product
+                dims: 4
+                index_options:
+                  type: int8_hnsw
+                  rescore_vector:
+                    oversample: 0
+
+  - do:
+      bulk:
+        index: int8_rescore_zero_hnsw
+        refresh: true
+        body: |
+          { "index": {"_id": "1"}}
+          { "vector":  [230.0, 300.33, -34.8988, 15.555] }
+          { "index": {"_id": "2"}}
+          { "vector":  [-0.5, 100.0, -13, 14.8] }
+          { "index": {"_id": "3"}}
+          { "vector":  [0.5, 111.3, -13.0, 14.8] }
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int8_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [-0.5, 90.0, -10, 14.8]
+            k: 3
+            num_candidates: 3
+
+  - match: { hits.total: 3 }
+  - set: { hits.hits.0._score: raw_score0 }
+  - set: { hits.hits.1._score: raw_score1 }
+  - set: { hits.hits.2._score: raw_score2 }
+
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int8_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [-0.5, 90.0, -10, 14.8]
+            k: 3
+            num_candidates: 3
+            rescore_vector:
+              oversample: 2
+
+  - match: { hits.total: 3 }
+  - set: { hits.hits.0._score: override_score0 }
+  - set: { hits.hits.1._score: override_score1 }
+  - set: { hits.hits.2._score: override_score2 }
+
+  - do:
+      indices.put_mapping:
+        index: int8_rescore_zero_hnsw
+        body:
+          properties:
+            vector:
+              type: dense_vector
+              similarity: max_inner_product
+              dims: 4
+              index_options:
+                type: int8_hnsw
+                rescore_vector:
+                  oversample: 2
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int8_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [-0.5, 90.0, -10, 14.8]
+            k: 3
+            num_candidates: 3
+
+  - match: { hits.total: 3 }
+  - set: { hits.hits.0._score: default_rescore0 }
+  - set: { hits.hits.1._score: default_rescore1 }
+  - set: { hits.hits.2._score: default_rescore2 }
+
+  - do:
+      indices.put_mapping:
+        index: int8_rescore_zero_hnsw
+        body:
+          properties:
+            vector:
+              type: dense_vector
+              similarity: max_inner_product
+              dims: 4
+              index_options:
+                type: int8_hnsw
+                rescore_vector:
+                  oversample: 0
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int8_rescore_zero_hnsw
+        body:
+          query:
+            script_score:
+              query: {match_all: {} }
+              script:
+                source: "double similarity = dotProduct(params.query_vector, 'vector'); return similarity < 0 ? 1 / (1 + -1 * similarity) : similarity + 1"
+                params:
+                  query_vector: [-0.5, 90.0, -10, 14.8]
+
+  # Compare scores as hit IDs may change depending on how things are distributed
+  - match: { hits.total: 3 }
+  - match: { hits.hits.0._score: $override_score0 }
+  - match: { hits.hits.0._score: $default_rescore0 }
+  - match: { hits.hits.1._score: $override_score1 }
+  - match: { hits.hits.1._score: $default_rescore1 }
+  - match: { hits.hits.2._score: $override_score2 }
+  - match: { hits.hits.2._score: $default_rescore2 }
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int8_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [-0.5, 90.0, -10, 14.8]
+            k: 3
+            num_candidates: 3
+
+  # Compare scores as hit IDs may change depending on how things are distributed
+  - match: { hits.total: 3 }
+  - match: { hits.hits.0._score: $raw_score0 }
+  - match: { hits.hits.1._score: $raw_score1 }
+  - match: { hits.hits.2._score: $raw_score2 }
diff --git a/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_half_byte_quantized.yml b/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_half_byte_quantized.yml
index 1faaba2be11a9..094f7a13ba6d4 100644
--- a/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_half_byte_quantized.yml
+++ b/rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/search.vectors/41_knn_search_half_byte_quantized.yml
@@ -660,8 +660,7 @@ setup:
             properties:
               vector:
                 type: dense_vector
-                dims: 64
-                index: true
+                dims: 4
                 similarity: max_inner_product
                 index_options:
                   type: int4_hnsw
@@ -674,11 +673,11 @@ setup:
         refresh: true
         body: |
           { "index": {"_id": "1"}}
-          { "vector": [0.077,  0.32 , -0.205,  0.63 ,  0.032,  0.201,  0.167, -0.313, 0.176,  0.531, -0.375,  0.334, -0.046,  0.078, -0.349,  0.272, 0.307, -0.083,  0.504,  0.255, -0.404,  0.289, -0.226, -0.132, -0.216,  0.49 ,  0.039,  0.507, -0.307,  0.107,  0.09 , -0.265, -0.285,  0.336, -0.272,  0.369, -0.282,  0.086, -0.132,  0.475, -0.224,  0.203,  0.439,  0.064,  0.246, -0.396,  0.297,  0.242, -0.028,  0.321, -0.022, -0.009, -0.001  ,  0.031, -0.533,  0.45, -0.683,  1.331,  0.194, -0.157, -0.1  , -0.279, -0.098, -0.176] }
+          { "vector":  [230.0, 300.33, -34.8988, 15.555] }
           { "index": {"_id": "2"}}
-          { "vector": [0.196,  0.514,  0.039,  0.555, -0.042,  0.242,  0.463, -0.348, -0.08 ,  0.442, -0.067, -0.05 , -0.001,  0.298, -0.377,  0.048, 0.307,  0.159,  0.278,  0.119, -0.057,  0.333, -0.289, -0.438, -0.014,  0.361, -0.169,  0.292, -0.229,  0.123,  0.031, -0.138, -0.139,  0.315, -0.216,  0.322, -0.445, -0.059,  0.071,  0.429, -0.602, -0.142,  0.11 ,  0.192,  0.259, -0.241,  0.181, -0.166, 0.082,  0.107, -0.05 ,  0.155,  0.011,  0.161, -0.486,  0.569, -0.489,  0.901,  0.208,  0.011, -0.209, -0.153, -0.27 , -0.013] }
+          { "vector":  [-0.5, 100.0, -13, 14.8] }
           { "index": {"_id": "3"}}
-          { "vector": [0.196,  0.514,  0.039,  0.555, -0.042,  0.242,  0.463, -0.348, -0.08 ,  0.442, -0.067, -0.05 , -0.001,  0.298, -0.377,  0.048, 0.307,  0.159,  0.278,  0.119, -0.057,  0.333, -0.289, -0.438, -0.014,  0.361, -0.169,  0.292, -0.229,  0.123,  0.031, -0.138, -0.139,  0.315, -0.216,  0.322, -0.445, -0.059,  0.071,  0.429, -0.602, -0.142,  0.11 ,  0.192,  0.259, -0.241,  0.181, -0.166, 0.082,  0.107, -0.05 ,  0.155,  0.011,  0.161, -0.486,  0.569, -0.489,  0.901,  0.208,  0.011, -0.209, -0.153, -0.27 , -0.013] }
+          { "vector":  [0.5, 111.3, -13.0, 14.8] }
 
   - do:
       headers:
@@ -689,14 +688,7 @@ setup:
         body:
           knn:
             field: vector
-            query_vector: [0.128,  0.067, -0.08 ,  0.395, -0.11 , -0.259,  0.473, -0.393,
-                           0.292,  0.571, -0.491,  0.444, -0.288,  0.198, -0.343,  0.015,
-                           0.232,  0.088,  0.228,  0.151, -0.136,  0.236, -0.273, -0.259,
-                           -0.217,  0.359, -0.207,  0.352, -0.142,  0.192, -0.061, -0.17 ,
-                           -0.343,  0.189, -0.221,  0.32 , -0.301, -0.1  ,  0.005,  0.232,
-                           -0.344,  0.136,  0.252,  0.157, -0.13 , -0.244,  0.193, -0.034,
-                           -0.12 , -0.193, -0.102,  0.252, -0.185, -0.167, -0.575,  0.582,
-                           -0.426,  0.983,  0.212,  0.204,  0.03 , -0.276, -0.425, -0.158]
+            query_vector: [-0.5, 90.0, -10, 14.8]
             k: 3
             num_candidates: 3
 
@@ -710,6 +702,7 @@ setup:
         Content-Type: application/json
       search:
         rest_total_hits_as_int: true
+        index: int4_rescore_hnsw
         body:
           query:
             script_score:
@@ -717,17 +710,228 @@ setup:
               script:
                 source: "double similarity = dotProduct(params.query_vector, 'vector'); return similarity < 0 ? 1 / (1 + -1 * similarity) : similarity + 1"
                 params:
-                  query_vector: [0.128,  0.067, -0.08 ,  0.395, -0.11 , -0.259,  0.473, -0.393,
-                                 0.292,  0.571, -0.491,  0.444, -0.288,  0.198, -0.343,  0.015,
-                                 0.232,  0.088,  0.228,  0.151, -0.136,  0.236, -0.273, -0.259,
-                                 -0.217,  0.359, -0.207,  0.352, -0.142,  0.192, -0.061, -0.17 ,
-                                 -0.343,  0.189, -0.221,  0.32 , -0.301, -0.1  ,  0.005,  0.232,
-                                 -0.344,  0.136,  0.252,  0.157, -0.13 , -0.244,  0.193, -0.034,
-                                 -0.12 , -0.193, -0.102,  0.252, -0.185, -0.167, -0.575,  0.582,
-                                 -0.426,  0.983,  0.212,  0.204,  0.03 , -0.276, -0.425, -0.158]
+                  query_vector: [-0.5, 90.0, -10, 14.8]
 
   # Compare scores as hit IDs may change depending on how things are distributed
   - match: { hits.total: 3 }
   - match: { hits.hits.0._score: $rescore_score0 }
   - match: { hits.hits.1._score: $rescore_score1 }
   - match: { hits.hits.2._score: $rescore_score2 }
+---
+"Test index configured rescore vector updateable and settable to 0":
+  - requires:
+      cluster_features: ["mapper.dense_vector.rescore_zero_vector"]
+      reason: Needs rescore_zero_vector feature
+
+  - do:
+      indices.create:
+        index: int4_rescore_0_hnsw
+        body:
+          settings:
+            index:
+              number_of_shards: 1
+          mappings:
+            properties:
+              vector:
+                type: dense_vector
+                index_options:
+                  type: int4_hnsw
+                  rescore_vector:
+                    oversample: 0
+
+  - do:
+      indices.create:
+        index: int4_rescore_update_hnsw
+        body:
+          settings:
+            index:
+              number_of_shards: 1
+          mappings:
+            properties:
+              vector:
+                type: dense_vector
+                index_options:
+                  type: int4_hnsw
+                  rescore_vector:
+                    oversample: 1
+
+  - do:
+      indices.put_mapping:
+        index: int4_rescore_update_hnsw
+        body:
+          properties:
+            vector:
+              type: dense_vector
+              index_options:
+                type: int4_hnsw
+                rescore_vector:
+                  oversample: 0
+
+  - do:
+      indices.get_mapping:
+        index: int4_rescore_update_hnsw
+
+  - match: { .int4_rescore_update_hnsw.mappings.properties.vector.index_options.rescore_vector.oversample: 0 }
+---
+"Test index configured rescore vector score consistency":
+  - requires:
+      cluster_features: ["mapper.dense_vector.rescore_zero_vector"]
+      reason: Needs rescore_zero_vector feature
+  - skip:
+      features: "headers"
+  - do:
+      indices.create:
+        index: int4_rescore_zero_hnsw
+        body:
+          settings:
+            index:
+              number_of_shards: 1
+          mappings:
+            properties:
+              vector:
+                type: dense_vector
+                similarity: max_inner_product
+                dims: 4
+                index_options:
+                  type: int4_hnsw
+                  rescore_vector:
+                    oversample: 0
+
+  - do:
+      bulk:
+        index: int4_rescore_zero_hnsw
+        refresh: true
+        body: |
+          { "index": {"_id": "1"}}
+          { "vector":  [230.0, 300.33, -34.8988, 15.555] }
+          { "index": {"_id": "2"}}
+          { "vector":  [-0.5, 100.0, -13, 14.8] }
+          { "index": {"_id": "3"}}
+          { "vector":  [0.5, 111.3, -13.0, 14.8] }
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int4_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [-0.5, 90.0, -10, 14.8]
+            k: 3
+            num_candidates: 3
+
+  - match: { hits.total: 3 }
+  - set: { hits.hits.0._score: raw_score0 }
+  - set: { hits.hits.1._score: raw_score1 }
+  - set: { hits.hits.2._score: raw_score2 }
+
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int4_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [-0.5, 90.0, -10, 14.8]
+            k: 3
+            num_candidates: 3
+            rescore_vector:
+              oversample: 2
+
+  - match: { hits.total: 3 }
+  - set: { hits.hits.0._score: override_score0 }
+  - set: { hits.hits.1._score: override_score1 }
+  - set: { hits.hits.2._score: override_score2 }
+
+  - do:
+      indices.put_mapping:
+        index: int4_rescore_zero_hnsw
+        body:
+          properties:
+            vector:
+              type: dense_vector
+              similarity: max_inner_product
+              dims: 4
+              index_options:
+                type: int4_hnsw
+                rescore_vector:
+                  oversample: 2
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int4_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [-0.5, 90.0, -10, 14.8]
+            k: 3
+            num_candidates: 3
+
+  - match: { hits.total: 3 }
+  - set: { hits.hits.0._score: default_rescore0 }
+  - set: { hits.hits.1._score: default_rescore1 }
+  - set: { hits.hits.2._score: default_rescore2 }
+
+  - do:
+      indices.put_mapping:
+        index: int4_rescore_zero_hnsw
+        body:
+          properties:
+            vector:
+              type: dense_vector
+              similarity: max_inner_product
+              dims: 4
+              index_options:
+                type: int4_hnsw
+                rescore_vector:
+                  oversample: 0
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int4_rescore_zero_hnsw
+        body:
+          query:
+            script_score:
+              query: {match_all: {} }
+              script:
+                source: "double similarity = dotProduct(params.query_vector, 'vector'); return similarity < 0 ? 1 / (1 + -1 * similarity) : similarity + 1"
+                params:
+                  query_vector: [-0.5, 90.0, -10, 14.8]
+
+  # Compare scores as hit IDs may change depending on how things are distributed
+  - match: { hits.total: 3 }
+  - match: { hits.hits.0._score: $override_score0 }
+  - match: { hits.hits.0._score: $default_rescore0 }
+  - match: { hits.hits.1._score: $override_score1 }
+  - match: { hits.hits.1._score: $default_rescore1 }
+  - match: { hits.hits.2._score: $override_score2 }
+  - match: { hits.hits.2._score: $default_rescore2 }
+
+  - do:
+      headers:
+        Content-Type: application/json
+      search:
+        rest_total_hits_as_int: true
+        index: int4_rescore_zero_hnsw
+        body:
+          knn:
+            field: vector
+            query_vector: [-0.5, 90.0, -10, 14.8]
+            k: 3
+            num_candidates: 3
+
+  # Compare scores as hit IDs may change depending on how things are distributed
+  - match: { hits.total: 3 }
+  - match: { hits.hits.0._score: $raw_score0 }
+  - match: { hits.hits.1._score: $raw_score1 }
+  - match: { hits.hits.2._score: $raw_score2 }
diff --git a/server/src/main/java/org/elasticsearch/TransportVersions.java b/server/src/main/java/org/elasticsearch/TransportVersions.java
index aa1c87e875aec..33c4bb0bef900 100644
--- a/server/src/main/java/org/elasticsearch/TransportVersions.java
+++ b/server/src/main/java/org/elasticsearch/TransportVersions.java
@@ -204,6 +204,7 @@ static TransportVersion def(int id) {
     public static final TransportVersion INDEX_METADATA_INCLUDES_RECENT_WRITE_LOAD = def(9_036_0_00);
     public static final TransportVersion RERANK_COMMON_OPTIONS_ADDED = def(9_037_0_00);
     public static final TransportVersion ESQL_REPORT_ORIGINAL_TYPES = def(9_038_00_0);
+    public static final TransportVersion RESCORE_VECTOR_ALLOW_ZERO = def(9_039_0_00);
 
     /*
      * STOP! READ THIS FIRST! No, really,
diff --git a/server/src/main/java/org/elasticsearch/index/IndexVersions.java b/server/src/main/java/org/elasticsearch/index/IndexVersions.java
index 774ddb33808ff..8bbf1cb9fc804 100644
--- a/server/src/main/java/org/elasticsearch/index/IndexVersions.java
+++ b/server/src/main/java/org/elasticsearch/index/IndexVersions.java
@@ -155,6 +155,7 @@ private static Version parseUnchecked(String version) {
     public static final IndexVersion ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS = def(9_015_0_00, Version.LUCENE_10_1_0);
     public static final IndexVersion SYNTHETIC_SOURCE_STORE_ARRAYS_NATIVELY_NUMBER = def(9_016_0_00, Version.LUCENE_10_1_0);
     public static final IndexVersion SYNTHETIC_SOURCE_STORE_ARRAYS_NATIVELY_BOOLEAN = def(9_017_0_00, Version.LUCENE_10_1_0);
+    public static final IndexVersion RESCORE_PARAMS_ALLOW_ZERO_TO_QUANTIZED_VECTORS = def(9_018_0_00, Version.LUCENE_10_1_0);
     /*
      * STOP! READ THIS FIRST! No, really,
      *        ____ _____ ___  ____  _        ____  _____    _    ____    _____ _   _ ___ ____    _____ ___ ____  ____ _____ _
diff --git a/server/src/main/java/org/elasticsearch/index/mapper/MapperFeatures.java b/server/src/main/java/org/elasticsearch/index/mapper/MapperFeatures.java
index 69477c272cab6..e3e3623bf8158 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/MapperFeatures.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/MapperFeatures.java
@@ -15,6 +15,7 @@
 import java.util.Set;
 
 import static org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper.RESCORE_VECTOR_QUANTIZED_VECTOR_MAPPING;
+import static org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapper.RESCORE_ZERO_VECTOR_QUANTIZED_VECTOR_MAPPING;
 
 /**
  * Spec for mapper-related features.
@@ -62,7 +63,8 @@ public Set<NodeFeature> getTestFeatures() {
             UKNOWN_FIELD_MAPPING_UPDATE_ERROR_MESSAGE,
             DOC_VALUES_SKIPPER,
             RESCORE_VECTOR_QUANTIZED_VECTOR_MAPPING,
-            DateFieldMapper.INVALID_DATE_FIX
+            DateFieldMapper.INVALID_DATE_FIX,
+            RESCORE_ZERO_VECTOR_QUANTIZED_VECTOR_MAPPING
         );
     }
 }
diff --git a/server/src/main/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapper.java b/server/src/main/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapper.java
index 3e85ef79d2e5f..11068e01d43b8 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapper.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapper.java
@@ -115,8 +115,13 @@ public static boolean isNotUnitVector(float magnitude) {
     public static final IndexVersion DEFAULT_TO_INT8 = DEFAULT_DENSE_VECTOR_TO_INT8_HNSW;
     public static final IndexVersion LITTLE_ENDIAN_FLOAT_STORED_INDEX_VERSION = IndexVersions.V_8_9_0;
     public static final IndexVersion ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS = IndexVersions.ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS;
+    public static final IndexVersion RESCORE_PARAMS_ALLOW_ZERO_TO_QUANTIZED_VECTORS =
+        IndexVersions.RESCORE_PARAMS_ALLOW_ZERO_TO_QUANTIZED_VECTORS;
 
     public static final NodeFeature RESCORE_VECTOR_QUANTIZED_VECTOR_MAPPING = new NodeFeature("mapper.dense_vector.rescore_vector");
+    public static final NodeFeature RESCORE_ZERO_VECTOR_QUANTIZED_VECTOR_MAPPING = new NodeFeature(
+        "mapper.dense_vector.rescore_zero_vector"
+    );
 
     public static final String CONTENT_TYPE = "dense_vector";
     public static final short MAX_DIMS_COUNT = 4096; // maximum allowed number of dimensions
@@ -1321,7 +1326,7 @@ public IndexOptions parseIndexOptions(String fieldName, Map<String, ?> indexOpti
                 }
                 RescoreVector rescoreVector = null;
                 if (indexVersion.onOrAfter(ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS)) {
-                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap);
+                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap, indexVersion);
                 }
                 MappingParser.checkNoRemainingFields(fieldName, indexOptionsMap);
                 return new Int8HnswIndexOptions(m, efConstruction, confidenceInterval, rescoreVector);
@@ -1356,7 +1361,7 @@ public IndexOptions parseIndexOptions(String fieldName, Map<String, ?> indexOpti
                 }
                 RescoreVector rescoreVector = null;
                 if (indexVersion.onOrAfter(ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS)) {
-                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap);
+                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap, indexVersion);
                 }
                 MappingParser.checkNoRemainingFields(fieldName, indexOptionsMap);
                 return new Int4HnswIndexOptions(m, efConstruction, confidenceInterval, rescoreVector);
@@ -1399,7 +1404,7 @@ public IndexOptions parseIndexOptions(String fieldName, Map<String, ?> indexOpti
                 }
                 RescoreVector rescoreVector = null;
                 if (indexVersion.onOrAfter(ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS)) {
-                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap);
+                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap, indexVersion);
                 }
                 MappingParser.checkNoRemainingFields(fieldName, indexOptionsMap);
                 return new Int8FlatIndexOptions(confidenceInterval, rescoreVector);
@@ -1425,7 +1430,7 @@ public IndexOptions parseIndexOptions(String fieldName, Map<String, ?> indexOpti
                 }
                 RescoreVector rescoreVector = null;
                 if (indexVersion.onOrAfter(ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS)) {
-                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap);
+                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap, indexVersion);
                 }
                 MappingParser.checkNoRemainingFields(fieldName, indexOptionsMap);
                 return new Int4FlatIndexOptions(confidenceInterval, rescoreVector);
@@ -1456,7 +1461,7 @@ public IndexOptions parseIndexOptions(String fieldName, Map<String, ?> indexOpti
                 int efConstruction = XContentMapValues.nodeIntegerValue(efConstructionNode);
                 RescoreVector rescoreVector = null;
                 if (indexVersion.onOrAfter(ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS)) {
-                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap);
+                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap, indexVersion);
                 }
                 MappingParser.checkNoRemainingFields(fieldName, indexOptionsMap);
                 return new BBQHnswIndexOptions(m, efConstruction, rescoreVector);
@@ -1477,7 +1482,7 @@ public boolean supportsDimension(int dims) {
             public IndexOptions parseIndexOptions(String fieldName, Map<String, ?> indexOptionsMap, IndexVersion indexVersion) {
                 RescoreVector rescoreVector = null;
                 if (indexVersion.onOrAfter(ADD_RESCORE_PARAMS_TO_QUANTIZED_VECTORS)) {
-                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap);
+                    rescoreVector = RescoreVector.fromIndexOptions(indexOptionsMap, indexVersion);
                 }
                 MappingParser.checkNoRemainingFields(fieldName, indexOptionsMap);
                 return new BBQFlatIndexOptions(rescoreVector);
@@ -1991,7 +1996,7 @@ record RescoreVector(float oversample) implements ToXContentObject {
         static final String NAME = "rescore_vector";
         static final String OVERSAMPLE = "oversample";
 
-        static RescoreVector fromIndexOptions(Map<String, ?> indexOptionsMap) {
+        static RescoreVector fromIndexOptions(Map<String, ?> indexOptionsMap, IndexVersion indexVersion) {
             Object rescoreVectorNode = indexOptionsMap.remove(NAME);
             if (rescoreVectorNode == null) {
                 return null;
@@ -2001,16 +2006,16 @@ static RescoreVector fromIndexOptions(Map<String, ?> indexOptionsMap) {
             if (oversampleNode == null) {
                 throw new IllegalArgumentException("Invalid rescore_vector value. Missing required field " + OVERSAMPLE);
             }
-            return new RescoreVector((float) XContentMapValues.nodeDoubleValue(oversampleNode));
-        }
-
-        RescoreVector {
-            if (oversample < 1) {
+            float oversampleValue = (float) XContentMapValues.nodeDoubleValue(oversampleNode);
+            if (oversampleValue == 0 && indexVersion.before(RESCORE_PARAMS_ALLOW_ZERO_TO_QUANTIZED_VECTORS)) {
                 throw new IllegalArgumentException("oversample must be greater than 1");
             }
-            if (oversample > 10) {
+            if (oversampleValue < 1 && oversampleValue != 0) {
+                throw new IllegalArgumentException("oversample must be greater than 1 or exactly 0");
+            } else if (oversampleValue > 10) {
                 throw new IllegalArgumentException("oversample must be less than or equal to 10");
             }
+            return new RescoreVector(oversampleValue);
         }
 
         @Override
@@ -2177,7 +2182,7 @@ public Query createKnnQuery(
         }
 
         private boolean needsRescore(Float rescoreOversample) {
-            return rescoreOversample != null && isQuantized();
+            return rescoreOversample != null && rescoreOversample > 0 && isQuantized();
         }
 
         private boolean isQuantized() {
diff --git a/server/src/main/java/org/elasticsearch/search/vectors/RescoreVectorBuilder.java b/server/src/main/java/org/elasticsearch/search/vectors/RescoreVectorBuilder.java
index 0e110a57d1e14..51cc87d58fcc2 100644
--- a/server/src/main/java/org/elasticsearch/search/vectors/RescoreVectorBuilder.java
+++ b/server/src/main/java/org/elasticsearch/search/vectors/RescoreVectorBuilder.java
@@ -9,9 +9,11 @@
 
 package org.elasticsearch.search.vectors;
 
+import org.elasticsearch.ElasticsearchStatusException;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.rest.RestStatus;
 import org.elasticsearch.xcontent.ConstructingObjectParser;
 import org.elasticsearch.xcontent.ParseField;
 import org.elasticsearch.xcontent.ToXContentObject;
@@ -21,9 +23,12 @@
 import java.io.IOException;
 import java.util.Objects;
 
+import static org.elasticsearch.TransportVersions.RESCORE_VECTOR_ALLOW_ZERO;
+
 public class RescoreVectorBuilder implements Writeable, ToXContentObject {
 
     public static final ParseField OVERSAMPLE_FIELD = new ParseField("oversample");
+    public static final float NO_OVERSAMPLE = 0.0F;
     public static final float MIN_OVERSAMPLE = 1.0F;
     private static final ConstructingObjectParser<RescoreVectorBuilder, Void> PARSER = new ConstructingObjectParser<>(
         "rescore_vector",
@@ -39,8 +44,8 @@ public class RescoreVectorBuilder implements Writeable, ToXContentObject {
 
     public RescoreVectorBuilder(float numCandidatesFactor) {
         Objects.requireNonNull(numCandidatesFactor, "[" + OVERSAMPLE_FIELD.getPreferredName() + "] must be set");
-        if (numCandidatesFactor < MIN_OVERSAMPLE) {
-            throw new IllegalArgumentException("[" + OVERSAMPLE_FIELD.getPreferredName() + "] must be >= " + MIN_OVERSAMPLE);
+        if (numCandidatesFactor < MIN_OVERSAMPLE && numCandidatesFactor != NO_OVERSAMPLE) {
+            throw new IllegalArgumentException("[" + OVERSAMPLE_FIELD.getPreferredName() + "] must be >= " + MIN_OVERSAMPLE + " or 0");
         }
         this.oversample = numCandidatesFactor;
     }
@@ -51,6 +56,17 @@ public RescoreVectorBuilder(StreamInput in) throws IOException {
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
+        // We don't want to serialize a `0` oversample to a node that doesn't know what to do with it.
+        if (oversample == NO_OVERSAMPLE && out.getTransportVersion().before(RESCORE_VECTOR_ALLOW_ZERO)) {
+            throw new ElasticsearchStatusException(
+                "[rescore_vector] does not support a 0 for ["
+                    + OVERSAMPLE_FIELD.getPreferredName()
+                    + "] before version ["
+                    + RESCORE_VECTOR_ALLOW_ZERO.toReleaseVersion()
+                    + "]",
+                RestStatus.BAD_REQUEST
+            );
+        }
         out.writeFloat(oversample);
     }
 
diff --git a/server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapperTests.java b/server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapperTests.java
index 036d2e62c8f48..62caaff6ca778 100644
--- a/server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapperTests.java
+++ b/server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapperTests.java
@@ -903,7 +903,7 @@ public void testRescoreVectorForNonQuantized() {
         }
     }
 
-    public void tesetRescoreVectorOldIndexVersion() {
+    public void testRescoreVectorOldIndexVersion() {
         IndexVersion incompatibleVersion = IndexVersionUtils.randomVersionBetween(
             random(),
             IndexVersionUtils.getLowestReadCompatibleVersion(),
@@ -927,6 +927,30 @@ public void tesetRescoreVectorOldIndexVersion() {
         }
     }
 
+    public void testRescoreZeroVectorOldIndexVersion() {
+        IndexVersion incompatibleVersion = IndexVersionUtils.randomVersionBetween(
+            random(),
+            IndexVersionUtils.getLowestReadCompatibleVersion(),
+            IndexVersionUtils.getPreviousVersion(DenseVectorFieldMapper.RESCORE_PARAMS_ALLOW_ZERO_TO_QUANTIZED_VECTORS)
+        );
+        for (String indexType : List.of("int8_hnsw", "int8_flat", "int4_hnsw", "int4_flat", "bbq_hnsw", "bbq_flat")) {
+            expectThrows(
+                MapperParsingException.class,
+                () -> createDocumentMapper(
+                    incompatibleVersion,
+                    fieldMapping(
+                        b -> b.field("type", "dense_vector")
+                            .field("index", true)
+                            .startObject("index_options")
+                            .field("type", indexType)
+                            .field(DenseVectorFieldMapper.RescoreVector.NAME, Map.of("oversample", 0f))
+                            .endObject()
+                    )
+                )
+            );
+        }
+    }
+
     public void testInvalidRescoreVector() {
         for (String indexType : List.of("int8_hnsw", "int8_flat", "int4_hnsw", "int4_flat", "bbq_hnsw", "bbq_flat")) {
             Exception e = expectThrows(
diff --git a/server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldTypeTests.java b/server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldTypeTests.java
index e98038b7a0759..b6df46d17b598 100644
--- a/server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldTypeTests.java
+++ b/server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldTypeTests.java
@@ -50,7 +50,7 @@ public DenseVectorFieldTypeTests() {
     }
 
     private static DenseVectorFieldMapper.RescoreVector randomRescoreVector() {
-        return new DenseVectorFieldMapper.RescoreVector(randomFloatBetween(1.0F, 10.0F, false));
+        return new DenseVectorFieldMapper.RescoreVector(randomBoolean() ? 0 : randomFloatBetween(1.0F, 10.0F, false));
     }
 
     private DenseVectorFieldMapper.IndexOptions randomIndexOptionsNonQuantized() {
@@ -94,24 +94,24 @@ private DenseVectorFieldMapper.IndexOptions randomIndexOptionsAll() {
     }
 
     private DenseVectorFieldMapper.IndexOptions randomIndexOptionsHnswQuantized() {
+        return randomIndexOptionsHnswQuantized(randomBoolean() ? null : randomRescoreVector());
+    }
+
+    private DenseVectorFieldMapper.IndexOptions randomIndexOptionsHnswQuantized(DenseVectorFieldMapper.RescoreVector rescoreVector) {
         return randomFrom(
             new DenseVectorFieldMapper.Int8HnswIndexOptions(
                 randomIntBetween(1, 100),
                 randomIntBetween(1, 10_000),
                 randomFrom((Float) null, 0f, (float) randomDoubleBetween(0.9, 1.0, true)),
-                randomFrom((DenseVectorFieldMapper.RescoreVector) null, randomRescoreVector())
+                rescoreVector
             ),
             new DenseVectorFieldMapper.Int4HnswIndexOptions(
                 randomIntBetween(1, 100),
                 randomIntBetween(1, 10_000),
                 randomFrom((Float) null, 0f, (float) randomDoubleBetween(0.9, 1.0, true)),
-                randomFrom((DenseVectorFieldMapper.RescoreVector) null, randomRescoreVector())
+                rescoreVector
             ),
-            new DenseVectorFieldMapper.BBQHnswIndexOptions(
-                randomIntBetween(1, 100),
-                randomIntBetween(1, 10_000),
-                randomFrom((DenseVectorFieldMapper.RescoreVector) null, randomRescoreVector())
-            )
+            new DenseVectorFieldMapper.BBQHnswIndexOptions(randomIntBetween(1, 100), randomIntBetween(1, 10_000), rescoreVector)
         );
     }
 
@@ -492,6 +492,40 @@ public void testRescoreOversampleModifiesNumCandidates() {
         checkRescoreQueryParameters(fieldType, 1000, 1000, 11.0F, OVERSAMPLE_LIMIT, OVERSAMPLE_LIMIT, 1000);
     }
 
+    public void testRescoreOversampleQueryOverrides() {
+        // verify we can override to `0`
+        DenseVectorFieldType fieldType = new DenseVectorFieldType(
+            "f",
+            IndexVersion.current(),
+            FLOAT,
+            3,
+            true,
+            VectorSimilarity.COSINE,
+            randomIndexOptionsHnswQuantized(new DenseVectorFieldMapper.RescoreVector(randomFloatBetween(1.1f, 9.9f, false))),
+            Collections.emptyMap()
+        );
+        Query query = fieldType.createKnnQuery(VectorData.fromFloats(new float[] { 1, 4, 10 }), 10, 100, 0f, null, null, null);
+        assertTrue(query instanceof ESKnnFloatVectorQuery);
+
+        // verify we can override a `0` to a positive number
+        fieldType = new DenseVectorFieldType(
+            "f",
+            IndexVersion.current(),
+            FLOAT,
+            3,
+            true,
+            VectorSimilarity.COSINE,
+            randomIndexOptionsHnswQuantized(new DenseVectorFieldMapper.RescoreVector(0)),
+            Collections.emptyMap()
+        );
+        query = fieldType.createKnnQuery(VectorData.fromFloats(new float[] { 1, 4, 10 }), 10, 100, 2f, null, null, null);
+        assertTrue(query instanceof RescoreKnnVectorQuery);
+        assertThat(((RescoreKnnVectorQuery) query).k(), equalTo(10));
+        ESKnnFloatVectorQuery esKnnQuery = (ESKnnFloatVectorQuery) ((RescoreKnnVectorQuery) query).innerQuery();
+        assertThat(esKnnQuery.kParam(), equalTo(20));
+
+    }
+
     private static void checkRescoreQueryParameters(
         DenseVectorFieldType fieldType,
         int k,
diff --git a/server/src/test/java/org/elasticsearch/search/vectors/AbstractKnnVectorQueryBuilderTestCase.java b/server/src/test/java/org/elasticsearch/search/vectors/AbstractKnnVectorQueryBuilderTestCase.java
index b3764d528ff0f..1a964c8c2b4f7 100644
--- a/server/src/test/java/org/elasticsearch/search/vectors/AbstractKnnVectorQueryBuilderTestCase.java
+++ b/server/src/test/java/org/elasticsearch/search/vectors/AbstractKnnVectorQueryBuilderTestCase.java
@@ -166,7 +166,7 @@ protected RescoreVectorBuilder randomRescoreVectorBuilder() {
             return null;
         }
 
-        return new RescoreVectorBuilder(randomFloatBetween(1.0f, 10.0f, false));
+        return new RescoreVectorBuilder(randomBoolean() ? 0f : randomFloatBetween(1.0f, 10.0f, false));
     }
 
     @Override
@@ -181,9 +181,13 @@ protected void doAssertLuceneQuery(KnnVectorQueryBuilder queryBuilder, Query que
             k = context.requestSize() == null || context.requestSize() < 0 ? DEFAULT_SIZE : context.requestSize();
         }
         if (queryBuilder.rescoreVectorBuilder() != null && isQuantizedElementType()) {
-            RescoreKnnVectorQuery rescoreQuery = (RescoreKnnVectorQuery) query;
-            assertEquals(k.intValue(), (rescoreQuery.k()));
-            query = rescoreQuery.innerQuery();
+            if (queryBuilder.rescoreVectorBuilder().oversample() > 0) {
+                RescoreKnnVectorQuery rescoreQuery = (RescoreKnnVectorQuery) query;
+                assertEquals(k.intValue(), (rescoreQuery.k()));
+                query = rescoreQuery.innerQuery();
+            } else {
+                assertFalse(query instanceof RescoreKnnVectorQuery);
+            }
         }
         switch (elementType()) {
             case FLOAT -> assertTrue(query instanceof ESKnnFloatVectorQuery);