diff --git a/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModel.php b/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModel.php
index e0e2e71b..4d61c82b 100644
--- a/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModel.php
+++ b/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModel.php
@@ -504,7 +504,14 @@ protected function prepareToolsParam(array $functionDeclarations): array
     /**
      * Prepares the response format parameter for the API request.
      *
-     * This is only called if the output MIME type is `application/json`.
+     * This is only called if the output MIME type is `application/json`. When an output schema is
+     * provided, it is wrapped in the `json_schema` envelope expected by the OpenAI Chat Completions
+     * API, which requires a `name` field and the schema under the `schema` key. The `name` uses a
+     * fixed identifier that satisfies the API's `^[a-zA-Z0-9_-]{1,64}$` constraint, rather than a
+     * value derived from the schema, to avoid producing an invalid name. If a caller already
+     * supplies a wrapped payload (i.e. an array containing both `name` and `schema` keys), it is
+     * passed through unchanged, allowing callers to opt into provider-specific options such as
+     * `strict`.
      *
      * @since 0.1.0
      *
@@ -513,7 +520,17 @@ protected function prepareToolsParam(array $functionDeclarations): array
      */
     protected function prepareResponseFormatParam(?array $outputSchema): array
     {
-        if (is_array($outputSchema)) {
+        if ($outputSchema === null) {
+            return [
+                'type' => 'json_object',
+            ];
+        }
+
+        // Pass through payloads that are already wrapped in the json_schema envelope.
+        $isWrappedEnvelope = isset($outputSchema['name'])
+            && isset($outputSchema['schema'])
+            && is_array($outputSchema['schema']);
+        if ($isWrappedEnvelope) {
             return [
                 'type' => 'json_schema',
                 'json_schema' => $outputSchema,
@@ -521,7 +538,11 @@ protected function prepareResponseFormatParam(?array $outputSchema): array
         }
 
         return [
-            'type' => 'json_object',
+            'type' => 'json_schema',
+            'json_schema' => [
+                'name' => 'response_schema',
+                'schema' => $outputSchema,
+            ],
         ];
     }
 
diff --git a/tests/unit/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModelTest.php b/tests/unit/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModelTest.php
index 6c99c75b..ae99b332 100644
--- a/tests/unit/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModelTest.php
+++ b/tests/unit/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModelTest.php
@@ -418,7 +418,16 @@ public function testPrepareGenerateTextParamsWithJsonOutputSchema(): void
         $params = $model->exposePrepareGenerateTextParams($prompt);
 
         $this->assertArrayHasKey('response_format', $params);
-        $this->assertEquals(['type' => 'json_schema', 'json_schema' => $schema], $params['response_format']);
+        $this->assertEquals(
+            [
+                'type' => 'json_schema',
+                'json_schema' => [
+                    'name' => 'response_schema',
+                    'schema' => $schema,
+                ],
+            ],
+            $params['response_format']
+        );
     }
 
     /**
@@ -950,7 +959,71 @@ public function testPrepareResponseFormatParamWithSchema(): void
         $model = $this->createModel();
         $format = $model->exposePrepareResponseFormatParam($schema);
 
-        $this->assertEquals(['type' => 'json_schema', 'json_schema' => $schema], $format);
+        $this->assertEquals(
+            [
+                'type' => 'json_schema',
+                'json_schema' => [
+                    'name' => 'response_schema',
+                    'schema' => $schema,
+                ],
+            ],
+            $format
+        );
+    }
+
+    /**
+     * Tests prepareResponseFormatParam() ignores the schema title when naming the envelope.
+     *
+     * The OpenAI API requires the json_schema name to match ^[a-zA-Z0-9_-]{1,64}$, so a
+     * user-supplied title (which may contain spaces or other invalid characters) must not be
+     * used as the name. A fixed, valid identifier is used instead.
+     *
+     * @return void
+     */
+    public function testPrepareResponseFormatParamIgnoresSchemaTitle(): void
+    {
+        $schema = [
+            'title' => 'Review Notes!',
+            'type' => 'object',
+            'properties' => ['key' => ['type' => 'string']],
+        ];
+        $model = $this->createModel();
+        $format = $model->exposePrepareResponseFormatParam($schema);
+
+        $this->assertEquals(
+            [
+                'type' => 'json_schema',
+                'json_schema' => [
+                    'name' => 'response_schema',
+                    'schema' => $schema,
+                ],
+            ],
+            $format
+        );
+    }
+
+    /**
+     * Tests prepareResponseFormatParam() passes through an already-wrapped envelope.
+     *
+     * @return void
+     */
+    public function testPrepareResponseFormatParamPassesThroughWrappedEnvelope(): void
+    {
+        $envelope = [
+            'name' => 'classification',
+            'strict' => true,
+            'schema' => ['type' => 'object', 'properties' => ['key' => ['type' => 'string']]],
+        ];
+        $model = $this->createModel();
+        $format = $model->exposePrepareResponseFormatParam($envelope);
+
+        $this->assertEquals(
+            [
+                'type' => 'json_schema',
+                'json_schema' => $envelope,
+            ],
+            $format
+        );
     }
 
     /**