Remove retired Gemini fallback models (#8199)

* Remove retired Gemini fallback models

* Prefer cheaper Gemini fallbacks first

docs/LLM_MODEL_COMPARISON.md

@@ -71,7 +71,7 @@ LLM settings can be changed at runtime via the admin console:
 1. Navigate to Admin Console → Settings
 2. Change `LlmProvider` to select vendor (gemini, openai, claude)
 3. Change the corresponding model name setting:
-   - `GeminiModelName` (default: gemini-3.1-flash-lite-preview)
+   - `GeminiModelName` (default: gemini-3.1-flash-lite)
    - `OpenAiModelName` (default: gpt-4.1-mini)
    - `ClaudeModelName` (default: claude-3-5-haiku-20241022)
 

src/main/go/net/eagle0/admin_server/admin_server.go

@@ -1616,7 +1616,7 @@ type SettingInfo struct {
 var llmProviderOptions = []string{"gemini", "openai", "claude"}
 var openAiModelOptions = []string{"gpt-4.1-mini", "gpt-5-mini", "gpt-5.1", "gpt-5.2", "gpt-4.1", "gpt-4o", "gpt-4o-mini", "o1", "o1-mini", "o3-mini"}
 var claudeModelOptions = []string{"claude-3-5-haiku-20241022", "claude-sonnet-4-20250514", "claude-opus-4-20250514", "claude-3-7-sonnet-20250219", "claude-3-5-sonnet-20241022"}
-var geminiModelOptions = []string{"gemini-3.1-flash-lite-preview", "gemini-2.5-flash-lite", "gemini-2.5-flash", "gemini-3-flash-preview", "gemini-2.5-pro", "gemini-3-pro-preview"}
+var geminiModelOptions = []string{"gemini-3.1-flash-lite", "gemini-3.5-flash", "gemini-2.5-flash-lite", "gemini-2.5-flash", "gemini-2.5-pro"}
 var historyBackendOptions = []string{"env", "sqlite", "postgres"}
 
 type SettingsPageData struct {

src/main/scala/net/eagle0/common/llm_integration/GeminiServiceImpl.scala

@@ -12,20 +12,21 @@ import org.json4s.jvalue2monadic
 import org.json4s.native.{Json, Serialization}
 
 object GeminiServiceImpl {
-  val defaultModel: String = "gemini-3.1-flash-lite-preview"
+  val defaultModel: String = "gemini-3.1-flash-lite"
 
   private val fallbackModels: Vector[String] = Vector(
-    "gemini-2.5-flash",
+    defaultModel,
     "gemini-2.5-flash-lite",
-    "gemini-2.0-flash",
-    "gemini-2.0-flash-lite"
+    "gemini-2.5-flash",
+    "gemini-2.5-pro",
+    "gemini-3.5-flash"
   )
 
   private lazy val apiKey = ApiKeys.gemini
   private val baseURL     = "https://generativelanguage.googleapis.com/v1beta/models"
 
   def fallbackModelNames(configuredModelName: String): Vector[String] =
-    (configuredModelName +: (fallbackModels :+ defaultModel)).distinct
+    (configuredModelName +: fallbackModels).distinct
 
   private def requestUrl(modelName: String): String =
     s"$baseURL/$modelName:streamGenerateContent?alt=sse&key=$apiKey"

src/main/scala/net/eagle0/eagle/library/settings/BUILD.bazel

@@ -3659,7 +3659,7 @@ scala_setting_library(
     name = "gemini_model_name",
     setting_name = "GeminiModelName",
     setting_type = "String",
-    setting_value = "gemini-3.1-flash-lite-preview",
+    setting_value = "gemini-3.1-flash-lite",
     visibility = [
         "//src/main/scala/net/eagle0/eagle:__subpackages__",
         "//src/main/scala/net/eagle0/util:__subpackages__",

src/main/scala/net/eagle0/eagle/service/GameAdminServiceImpl.scala

@@ -379,7 +379,7 @@ class GameAdminServiceImpl(
             case "gemini" =>
               settingsMap.getOrElse(
                 "GeminiModelName",
-                currentSettings.getOrElse("GeminiModelName", "gemini-3.1-flash-lite-preview")
+                currentSettings.getOrElse("GeminiModelName", GeminiServiceImpl.defaultModel)
               )
             case _        => ""
           }

src/test/scala/net/eagle0/common/llm_integration/GeminiServiceImplTest.scala

@@ -8,13 +8,21 @@ class GeminiServiceImplTest extends AnyFlatSpec with Matchers {
   "fallbackModelNames" should "try the configured model before fallback Gemini models" in {
     GeminiServiceImpl.fallbackModelNames("gemini-2.5-flash-lite") shouldBe Vector(
       "gemini-2.5-flash-lite",
+      GeminiServiceImpl.defaultModel,
       "gemini-2.5-flash",
-      "gemini-2.0-flash",
-      "gemini-2.0-flash-lite",
-      GeminiServiceImpl.defaultModel
+      "gemini-2.5-pro",
+      "gemini-3.5-flash"
     )
   }
 
+  it should "not include shut down Gemini model names" in {
+    val modelNames = GeminiServiceImpl.fallbackModelNames("gemini-2.5-flash-lite")
+
+    modelNames should not contain "gemini-2.0-flash"
+    modelNames should not contain "gemini-2.0-flash-lite"
+    modelNames should not contain "gemini-3.1-flash-lite-preview"
+  }
+
   it should "not duplicate the configured model when it is already a fallback" in {
     GeminiServiceImpl
       .fallbackModelNames(GeminiServiceImpl.defaultModel)

src/test/scala/net/eagle0/eagle/service/LlmResolverTest.scala

@@ -76,7 +76,7 @@ class LlmResolverTest extends AnyFlatSpec with MockFactory {
   it should "expand Gemini provider keys by fallback model" in {
     LlmResolver.providerKeysFor("gemini", "gemini-2.5-flash-lite").take(2) shouldBe Vector(
       "gemini/gemini-2.5-flash-lite",
-      "gemini/gemini-2.5-flash"
+      "gemini/gemini-3.1-flash-lite"
     )
   }