FIX: normalize keys in structured output

Previously we did not validate the hash passed in to structured
outputs which could either be string based or symbol base

Specifically this broke structured outputs for Gemini in some
specific cases.

Author: SamSaffron

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