Transition to flash GA model when experiment flag is present.

docs/reference/configuration.md

@@ -602,6 +602,12 @@
           "model": "gemini-3.1-flash-lite"
         }
       },
+      "gemini-3.5-flash": {
+        "extends": "chat-base-3",
+        "modelConfig": {
+          "model": "gemini-3.5-flash"
+        }
+      },
       "gemma-4-31b-it": {
         "extends": "chat-base-3",
         "modelConfig": {
@@ -626,6 +632,12 @@
           "model": "gemini-3-flash-preview"
         }
       },
+      "gemini-3.5-flash-base": {
+        "extends": "base",
+        "modelConfig": {
+          "model": "gemini-3.5-flash"
+        }
+      },
       "classifier": {
         "extends": "base",
         "modelConfig": {
@@ -868,6 +880,16 @@
           "multimodalToolUse": true
         }
       },
+      "gemini-3.5-flash": {
+        "tier": "flash",
+        "family": "gemini-3",
+        "isPreview": false,
+        "isVisible": true,
+        "features": {
+          "thinking": false,
+          "multimodalToolUse": true
+        }
+      },
       "gemini-2.5-pro": {
         "tier": "pro",
         "family": "gemini-2.5",
@@ -1020,9 +1042,44 @@
         "contexts": [
           {
             "condition": {
+              "useGemini3_5Flash": true
+            },
+            "target": "gemini-3.5-flash"
+          },
+          {
+            "condition": {
+              "hasAccessToPreview": false
+            },
+            "target": "gemini-2.5-flash"
+          }
+        ]
+      },
+      "gemini-3.5-flash": {
+        "default": "gemini-3.5-flash",
+        "contexts": [
+          {
+            "condition": {
+              "useGemini3_5Flash": false,
               "hasAccessToPreview": false
             },
             "target": "gemini-2.5-flash"
+          },
+          {
+            "condition": {
+              "useGemini3_5Flash": false
+            },
+            "target": "gemini-3-flash-preview"
+          }
+        ]
+      },
+      "gemini-2.5-flash": {
+        "default": "gemini-2.5-flash",
+        "contexts": [
+          {
+            "condition": {
+              "useGemini3_5Flash": true
+            },
+            "target": "gemini-3.5-flash"
           }
         ]
       },
@@ -1104,6 +1161,12 @@
       "flash": {
         "default": "gemini-3-flash-preview",
         "contexts": [
+          {
+            "condition": {
+              "useGemini3_5Flash": true
+            },
+            "target": "gemini-3.5-flash"
+          },
           {
             "condition": {
               "hasAccessToPreview": false
@@ -1157,6 +1220,12 @@
       "flash": {
         "default": "gemini-3-flash-preview",
         "contexts": [
+          {
+            "condition": {
+              "useGemini3_5Flash": true
+            },
+            "target": "gemini-3.5-flash"
+          },
           {
             "condition": {
               "hasAccessToPreview": false

evals/llm-judge.ts

@@ -76,10 +76,30 @@ export class LLMJudge {
 
     for (const res of rawResults) {
       // Remove any punctuation the model might have appended
-      const cleanRes = res.replace(/[^A-Z]/g, '');
-      if (cleanRes.startsWith('YES')) yes++;
-      else if (cleanRes.startsWith('NO')) no++;
-      else other++;
+      const cleanRes = res.replace(/[^A-Z ]/g, '');
+      if (
+        cleanRes.includes('THE ANSWER IS YES') ||
+        cleanRes.includes('ANSWER IS YES') ||
+        cleanRes.endsWith('YES')
+      ) {
+        yes++;
+      } else if (
+        cleanRes.includes('THE ANSWER IS NO') ||
+        cleanRes.includes('ANSWER IS NO') ||
+        cleanRes.endsWith('NO')
+      ) {
+        no++;
+      } else if (cleanRes.trim() === 'YES') {
+        yes++;
+      } else if (cleanRes.trim() === 'NO') {
+        no++;
+      } else {
+        // Fallback: look for YES or NO as standalone words or at the end
+        const words = cleanRes.split(/\s+/);
+        if (words.includes('YES')) yes++;
+        else if (words.includes('NO')) no++;
+        else other++;
+      }
     }
 
     // Pass if YES > NO and YES > OTHER (plurality)

packages/core/src/availability/policyCatalog.ts

@@ -33,6 +33,7 @@ export interface ModelPolicyOptions {
   useGemini31?: boolean;
   useGemini31FlashLite?: boolean;
   useCustomToolModel?: boolean;
+  useGemini3_5Flash?: boolean;
 }
 
 const DEFAULT_ACTIONS: ModelPolicyActionMap = {
@@ -94,6 +95,9 @@ export function getModelPolicyChain(
       PREVIEW_GEMINI_MODEL,
       options.useGemini31,
       options.useCustomToolModel,
+      true,
+      undefined,
+      options.useGemini3_5Flash,
     );
     return [
       definePolicy({

packages/core/src/availability/policyHelpers.ts

@@ -54,6 +54,7 @@ export function resolvePolicyChain(
   const useGemini31 = config.getGemini31LaunchedSync?.() ?? false;
   const useCustomToolModel = config.getUseCustomToolModelSync?.() ?? false;
   const hasAccessToPreview = config.getHasAccessToPreviewModel?.() ?? false;
+  const useGemini3_5Flash = config.hasGemini35FlashGAAccess?.() ?? false;
 
   // Capture the original family intent before any normalization or early downgrade.
   const isOriginallyGemini3 = isGemini3Model(modelFromConfig, config);
@@ -65,6 +66,7 @@ export function resolvePolicyChain(
       useCustomToolModel,
       hasAccessToPreview,
       config,
+      useGemini3_5Flash,
     ),
   );
   const isAutoPreferred = normalizedPreferredModel
@@ -82,6 +84,7 @@ export function resolvePolicyChain(
     const context = {
       useGemini3_1: useGemini31,
       useCustomTools: useCustomToolModel,
+      useGemini3_5Flash,
     };
 
     if (resolvedModel === DEFAULT_GEMINI_FLASH_LITE_MODEL) {
@@ -136,6 +139,7 @@ export function resolvePolicyChain(
           userTier: config.getUserTier(),
           useGemini31,
           useCustomToolModel,
+          useGemini3_5Flash,
         });
       } else {
         // User requested Gemini 3 but has no access. Proactively downgrade
@@ -146,6 +150,7 @@ export function resolvePolicyChain(
           userTier: config.getUserTier(),
           useGemini31,
           useCustomToolModel,
+          useGemini3_5Flash,
         });
       }
     } else {

packages/core/src/code_assist/experiments/flagNames.ts

@@ -19,6 +19,7 @@ export const ExperimentFlags = {
   GEMINI_3_1_PRO_LAUNCHED: 45760185,
   PRO_MODEL_NO_ACCESS: 45768879,
   DEFAULT_REQUEST_TIMEOUT: 45773134,
+  GEMINI_3_5_FLASH_GA_LAUNCHED: 45780819,
 } as const;
 
 export type ExperimentFlagName =

packages/core/src/config/config.ts

@@ -2054,6 +2054,7 @@ export class Config implements McpContext, AgentLoopContext {
       this.getUseCustomToolModelSync(),
       this.getHasAccessToPreviewModel(),
       this,
+      this.hasGemini35FlashGAAccess(),
     );
 
     const isPreview = isPreviewModel(primaryModel, this);
@@ -2093,6 +2094,7 @@ export class Config implements McpContext, AgentLoopContext {
       this.getUseCustomToolModelSync(),
       this.getHasAccessToPreviewModel(),
       this,
+      this.hasGemini35FlashGAAccess(),
     );
     return this.modelQuotas.get(primaryModel)?.remaining;
   }
@@ -2108,6 +2110,7 @@ export class Config implements McpContext, AgentLoopContext {
       this.getUseCustomToolModelSync(),
       this.getHasAccessToPreviewModel(),
       this,
+      this.hasGemini35FlashGAAccess(),
     );
     return this.modelQuotas.get(primaryModel)?.limit;
   }
@@ -2123,6 +2126,7 @@ export class Config implements McpContext, AgentLoopContext {
       this.getUseCustomToolModelSync(),
       this.getHasAccessToPreviewModel(),
       this,
+      this.hasGemini35FlashGAAccess(),
     );
     return this.modelQuotas.get(primaryModel)?.resetTime;
   }
@@ -3537,6 +3541,22 @@ export class Config implements McpContext, AgentLoopContext {
     );
   }
 
+  /**
+   * Returns whether Gemini 3.5 Flash GA has been launched.
+   *
+   * Note: This method should only be called after startup, once experiments have been loaded.
+   */
+  hasGemini35FlashGAAccess(): boolean {
+    const authType = this.contentGeneratorConfig?.authType;
+    if (this.isGemini31LaunchedForAuthType(authType)) {
+      return true;
+    }
+    return (
+      this.experiments?.flags[ExperimentFlags.GEMINI_3_5_FLASH_GA_LAUNCHED]
+        ?.boolValue ?? false
+    );
+  }
+
   /**
    * Returns whether Gemini 3.1 has been launched.
    *

packages/core/src/config/defaultModelConfigs.ts

@@ -113,6 +113,12 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
         model: 'gemini-3.1-flash-lite',
       },
     },
+    'gemini-3.5-flash': {
+      extends: 'chat-base-3',
+      modelConfig: {
+        model: 'gemini-3.5-flash',
+      },
+    },
     'gemma-4-31b-it': {
       extends: 'chat-base-3',
       modelConfig: {
@@ -139,6 +145,12 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
         model: 'gemini-3-flash-preview',
       },
     },
+    'gemini-3.5-flash-base': {
+      extends: 'base',
+      modelConfig: {
+        model: 'gemini-3.5-flash',
+      },
+    },
     classifier: {
       extends: 'base',
       modelConfig: {
@@ -346,6 +358,13 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
       isVisible: true,
       features: { thinking: false, multimodalToolUse: true },
     },
+    'gemini-3.5-flash': {
+      tier: 'flash',
+      family: 'gemini-3',
+      isPreview: false,
+      isVisible: true,
+      features: { thinking: false, multimodalToolUse: true },
+    },
     'gemini-2.5-pro': {
       tier: 'pro',
       family: 'gemini-2.5',
@@ -450,12 +469,32 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     'gemini-3-flash-preview': {
       default: 'gemini-3-flash-preview',
       contexts: [
+        { condition: { useGemini3_5Flash: true }, target: 'gemini-3.5-flash' },
         {
           condition: { hasAccessToPreview: false },
           target: 'gemini-2.5-flash',
         },
       ],
     },
+    'gemini-3.5-flash': {
+      default: 'gemini-3.5-flash',
+      contexts: [
+        {
+          condition: { useGemini3_5Flash: false, hasAccessToPreview: false },
+          target: 'gemini-2.5-flash',
+        },
+        {
+          condition: { useGemini3_5Flash: false },
+          target: 'gemini-3-flash-preview',
+        },
+      ],
+    },
+    'gemini-2.5-flash': {
+      default: 'gemini-2.5-flash',
+      contexts: [
+        { condition: { useGemini3_5Flash: true }, target: 'gemini-3.5-flash' },
+      ],
+    },
     'gemini-3-pro-preview': {
       default: 'gemini-3-pro-preview',
       contexts: [
@@ -504,6 +543,7 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     flash: {
       default: 'gemini-3-flash-preview',
       contexts: [
+        { condition: { useGemini3_5Flash: true }, target: 'gemini-3.5-flash' },
         {
           condition: { hasAccessToPreview: false },
           target: 'gemini-2.5-flash',
@@ -535,6 +575,7 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     flash: {
       default: 'gemini-3-flash-preview',
       contexts: [
+        { condition: { useGemini3_5Flash: true }, target: 'gemini-3.5-flash' },
         {
           condition: { hasAccessToPreview: false },
           target: 'gemini-2.5-flash',