FIX: normalize keys in structured output

lib/completions/llm.rb

@@ -80,7 +80,7 @@ def presets
                       tokens: 800_000,
                       endpoint:
                         "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash",
-                      display_name: "Gemini 2.5 Pro",
+                      display_name: "Gemini 2.5 Flash",
                       input_cost: 0.30,
                       output_cost: 2.50,
                     },
@@ -379,6 +379,12 @@ def generate(
 
         model_params[:temperature] = temperature if temperature
         model_params[:top_p] = top_p if top_p
+
+        # internals expect symbolized keys, so we normalize here
+        response_format =
+          JSON.parse(response_format.to_json, symbolize_names: true) if response_format &&
+          response_format.is_a?(Hash)
+
         model_params[:response_format] = response_format if response_format
         model_params.merge!(extra_model_params) if extra_model_params
 

spec/lib/completions/endpoints/gemini_spec.rb

@@ -612,6 +612,7 @@ def tool_response
       ).to_return(status: 200, body: response)
 
       structured_response = nil
+
       llm.generate("Hello", response_format: schema, user: user) do |partial|
         structured_response = partial
       end
@@ -626,6 +627,23 @@ def tool_response
         schema.dig(:json_schema, :schema).except(:additionalProperties),
       )
       expect(parsed.dig(:generationConfig, :responseMimeType)).to eq("application/json")
+
+      structured_response = nil
+      # once more but this time lets have the schema as string keys
+      llm.generate("Hello", response_format: schema.as_json, user: user) do |partial|
+        structured_response = partial
+      end
+
+      expect(structured_response.read_buffered_property(:key)).to eq("Hello!\n there")
+      expect(structured_response.read_buffered_property(:num)).to eq(42)
+
+      parsed = JSON.parse(req_body, symbolize_names: true)
+
+      # Verify that schema is passed following Gemini API specs.
+      expect(parsed.dig(:generationConfig, :responseSchema)).to eq(
+        schema.dig(:json_schema, :schema).except(:additionalProperties),
+      )
+      expect(parsed.dig(:generationConfig, :responseMimeType)).to eq("application/json")
     end
   end