fix(ai-proxy): plugin config should own the tuning parameters

kong/llm/drivers/shared.lua

@@ -131,10 +131,10 @@ _M.clear_response_headers = {
 -- @return {string} error if any is thrown - request should definitely be terminated if this is not nil
 function _M.merge_config_defaults(request, options, request_format)
   if options then
-    request.temperature = request.temperature or options.temperature
-    request.max_tokens = request.max_tokens or options.max_tokens
-    request.top_p = request.top_p or options.top_p
-    request.top_k = request.top_k or options.top_k
+    request.temperature = options.temperature or request.temperature
+    request.max_tokens = options.max_tokens or request.max_tokens 
+    request.top_p = options.top_p or request.top_p
+    request.top_k = options.top_k or request.top_k
   end
 
   return request, nil

spec/03-plugins/38-ai-proxy/01-unit_spec.lua

@@ -629,7 +629,7 @@ describe(PLUGIN_NAME .. ": (unit)", function()
       SAMPLE_LLM_V1_CHAT_WITH_SOME_OPTS,
       {
         max_tokens = 1024,
-        top_p = 1.0,
+        top_p = 0.5,
       },
       "llm/v1/chat"
     )
@@ -638,9 +638,9 @@ describe(PLUGIN_NAME .. ": (unit)", function()
 
     assert.is_nil(err)
     assert.same({
-      max_tokens          = 256,
+      max_tokens          = 1024,
       temperature         = 0.1,
-      top_p               = 0.2,
+      top_p               = 0.5,
       some_extra_param    = "string_val",
       another_extra_param = 0.5,
     }, formatted)

spec/03-plugins/38-ai-proxy/02-openai_integration_spec.lua

@@ -841,6 +841,23 @@ for _, strategy in helpers.all_strategies() do if strategy ~= "cassandra" then
         }, json.choices[1].message)
       end)
 
+      it("tries to override configured model", function()
+        local r = client:get("/openai/llm/v1/chat/good", {
+          headers = {
+            ["content-type"] = "application/json",
+            ["accept"] = "application/json",
+          },
+          body = pl_file.read("spec/fixtures/ai-proxy/openai/llm-v1-chat/requests/good_own_model.json"),
+        })
+
+        -- validate that the request succeeded, response status 200
+        local body = assert.res_status(400 , r)
+        local json = cjson.decode(body)
+
+        -- check this is in the 'kong' response format
+        assert.same(json, {error = { message = "cannot use own model - must be: gpt-3.5-turbo" } })
+      end)
+
       it("bad upstream response", function()
         local r = client:get("/openai/llm/v1/chat/bad_upstream_response", {
           headers = {