diff --git a/api/src/api/request/pipeline.js b/api/src/api/request/pipeline.js
index 290eb3b2..66fa8a0e 100644
--- a/api/src/api/request/pipeline.js
+++ b/api/src/api/request/pipeline.js
@@ -49,7 +49,36 @@ module.exports = class RequestPipeline {
     return this;
   }
 
+  addNeuralModelId() {
+    const neuralModelId = process.env.OPENSEARCH_MODEL_ID;
+    if (!neuralModelId) return this;
+
+    const recursivelyAddNeuralModelId = (query) => {
+      if (Array.isArray(query)) {
+        for (const subQuery of query) {
+          recursivelyAddNeuralModelId(subQuery);
+        }
+      }
+
+      if (typeof query !== "object" || query === null) return this;
+
+      for (const key in query) {
+        if (key === "neural") {
+          const [field] = Object.keys(query.neural);
+          query.neural[field].model_id ||= neuralModelId;
+        } else {
+          recursivelyAddNeuralModelId(query[key]);
+        }
+      }
+    };
+
+    recursivelyAddNeuralModelId(this.searchContext.query);
+
+    return this;
+  }
+
   toJson() {
+    this.addNeuralModelId();
     return JSON.stringify(sortJson(this.searchContext));
   }
 };
diff --git a/api/test/unit/api/request/pipeline.test.js b/api/test/unit/api/request/pipeline.test.js
index 470678d1..bd15c917 100644
--- a/api/test/unit/api/request/pipeline.test.js
+++ b/api/test/unit/api/request/pipeline.test.js
@@ -151,4 +151,93 @@ describe("RequestPipeline", () => {
       }
     });
   });
+
+  describe("addNeuralModelId", () => {
+    let oldModelId;
+    beforeEach(() => {
+      oldModelId = process.env.OPENSEARCH_MODEL_ID;
+      process.env.OPENSEARCH_MODEL_ID = "MODEL_ID";
+      requestBody.query = {
+        neural: {
+          embedding: {
+            query_text:
+              "Do you have any materials related to testing the request pipeline?",
+            k: 5,
+          },
+        },
+      };
+      pipeline = new RequestPipeline(requestBody);
+    });
+
+    afterEach(() => {
+      if (oldModelId) {
+        process.env.OPENSEARCH_MODEL_ID = oldModelId;
+      } else {
+        delete process.env.OPENSEARCH_MODEL_ID;
+      }
+      oldModelId = null;
+    });
+
+    it("does not modify the query if OPENSEARCH_MODEL_ID is not set", () => {
+      delete process.env.OPENSEARCH_MODEL_ID;
+      pipeline.addNeuralModelId();
+      expect(pipeline.searchContext.query).to.deep.equal(requestBody.query);
+    });
+
+    it("does not modify the query if there are no neural queries", () => {
+      requestBody.query = {
+        term: {
+          all_titles: "request pipeline testing",
+        },
+      };
+      pipeline = new RequestPipeline(requestBody);
+      pipeline.addNeuralModelId();
+      expect(pipeline.searchContext.query).to.deep.equal(requestBody.query);
+    });
+
+    it("does not modify the query if there is already a model_id", () => {
+      requestBody.query.neural.embedding.model_id = "EXISTING_MODEL_ID";
+      pipeline = new RequestPipeline(requestBody);
+      pipeline.addNeuralModelId();
+      expect(pipeline.searchContext.query.neural.embedding.model_id).to.eq(
+        "EXISTING_MODEL_ID"
+      );
+    });
+
+    it("automatically adds the model_id to a neural query", () => {
+      pipeline.addNeuralModelId();
+      expect(pipeline.searchContext.query.neural.embedding.model_id).to.eq(
+        "MODEL_ID"
+      );
+    });
+
+    it("recursively adds the model_id to all neural queries in a hybrid query", () => {
+      event.userToken = new ApiToken();
+      requestBody.query = {
+        hybrid: {
+          queries: [
+            {
+              neural: {
+                embedding: {
+                  query_text:
+                    "Do you have any materials related to testing the request pipeline?",
+                  k: 5,
+                },
+              },
+            },
+            {
+              term: {
+                all_titles: "request pipeline testing",
+              },
+            },
+          ],
+        },
+      };
+      pipeline = new RequestPipeline(requestBody);
+      pipeline.addNeuralModelId();
+      expect(
+        pipeline.searchContext.query.hybrid.queries[0].neural.embedding.model_id
+      ).to.eq("MODEL_ID");
+    });
+  });
 });