diff --git a/src/upstream/translator.ts b/src/upstream/translator.ts
index 6410787..d4b14d2 100644
--- a/src/upstream/translator.ts
+++ b/src/upstream/translator.ts
@@ -201,7 +201,6 @@ export function openaiToAnthropic(body: any): any {
         format: {
           type: "json_schema",
           schema: fmt.json_schema.schema,
-          name: fmt.json_schema.name,
         },
       };
     } else if (fmt.type === "json_object") {
@@ -580,7 +579,6 @@ export function responsesToAnthropic(body: any): any {
         format: {
           type: "json_schema",
           schema: fmt.schema,
-          name: fmt.name,
         },
       };
     } else if (fmt.type === "json_object") {
diff --git a/tests/unit.test.ts b/tests/unit.test.ts
index 6f235d6..703b3da 100644
--- a/tests/unit.test.ts
+++ b/tests/unit.test.ts
@@ -568,7 +568,11 @@ test("openaiToAnthropic translates response_format json_schema", () => {
     },
   });
   assert.equal(result.output_config.format.type, "json_schema");
-  assert.equal(result.output_config.format.name, "test");
+  // Anthropic's Messages API rejects an extra `name` field here with
+  // "Extra inputs are not permitted" (verified against the live API) --
+  // unlike OpenAI's json_schema format, Anthropic's output_config.format
+  // only accepts { type, schema }.
+  assert.equal(result.output_config.format.name, undefined);
 });
 
 test("openaiToAnthropic translates tool role messages", () => {