diff --git a/packages/core/src/code_assist/converter.ts b/packages/core/src/code_assist/converter.ts
index a71c70da..9c8a2434 100644
--- a/packages/core/src/code_assist/converter.ts
+++ b/packages/core/src/code_assist/converter.ts
@@ -22,7 +22,6 @@ import {
   Part,
   SafetySetting,
   PartUnion,
-  SchemaUnion,
   SpeechConfigUnion,
   ThinkingConfig,
   ToolListUnion,
@@ -61,7 +60,7 @@ interface VertexGenerationConfig {
   frequencyPenalty?: number;
   seed?: number;
   responseMimeType?: string;
-  responseSchema?: SchemaUnion;
+  responseJsonSchema?: unknown;
   routingConfig?: GenerationConfigRoutingConfig;
   modelSelectionConfig?: ModelSelectionConfig;
   responseModalities?: string[];
@@ -230,7 +229,7 @@ function toVertexGenerationConfig(
     frequencyPenalty: config.frequencyPenalty,
     seed: config.seed,
     responseMimeType: config.responseMimeType,
-    responseSchema: config.responseSchema,
+    responseJsonSchema: config.responseJsonSchema,
     routingConfig: config.routingConfig,
     modelSelectionConfig: config.modelSelectionConfig,
     responseModalities: config.responseModalities,
diff --git a/packages/core/src/core/client.test.ts b/packages/core/src/core/client.test.ts
index 2e8d086f..4c6f6dbb 100644
--- a/packages/core/src/core/client.test.ts
+++ b/packages/core/src/core/client.test.ts
@@ -396,7 +396,7 @@ describe('Gemini Client (client.ts)', () => {
             systemInstruction: getCoreSystemPrompt(''),
             temperature: 0,
             topP: 1,
-            responseSchema: schema,
+            responseJsonSchema: schema,
             responseMimeType: 'application/json',
           },
           contents,
@@ -435,7 +435,7 @@ describe('Gemini Client (client.ts)', () => {
             temperature: 0.9,
             topP: 1, // from default
             topK: 20,
-            responseSchema: schema,
+            responseJsonSchema: schema,
             responseMimeType: 'application/json',
           },
           contents,
diff --git a/packages/core/src/core/client.ts b/packages/core/src/core/client.ts
index df3dbc4e..cc492472 100644
--- a/packages/core/src/core/client.ts
+++ b/packages/core/src/core/client.ts
@@ -7,7 +7,6 @@
 import {
   EmbedContentParameters,
   GenerateContentConfig,
-  SchemaUnion,
   PartListUnion,
   Content,
   Tool,
@@ -515,7 +514,7 @@ export class GeminiClient {
 
   async generateJson(
     contents: Content[],
-    schema: SchemaUnion,
+    schema: Record<string, unknown>,
     abortSignal: AbortSignal,
     model?: string,
     config: GenerateContentConfig = {},
@@ -539,7 +538,7 @@ export class GeminiClient {
             config: {
               ...requestConfig,
               systemInstruction,
-              responseSchema: schema,
+              responseJsonSchema: schema,
               responseMimeType: 'application/json',
             },
             contents,
diff --git a/packages/core/src/services/loopDetectionService.ts b/packages/core/src/services/loopDetectionService.ts
index a01e4ee9..409e92a8 100644
--- a/packages/core/src/services/loopDetectionService.ts
+++ b/packages/core/src/services/loopDetectionService.ts
@@ -9,7 +9,6 @@ import { GeminiEventType, ServerGeminiStreamEvent } from '../core/turn.js';
 import { logLoopDetected } from '../telemetry/loggers.js';
 import { LoopDetectedEvent, LoopType } from '../telemetry/types.js';
 import { Config, DEFAULT_GEMINI_FLASH_MODEL } from '../config/config.js';
-import { SchemaUnion, Type } from '@google/genai';
 
 const TOOL_CALL_LOOP_THRESHOLD = 5;
 const CONTENT_LOOP_THRESHOLD = 10;
@@ -341,16 +340,16 @@ Please analyze the conversation history to determine the possibility that the co
       ...recentHistory,
       { role: 'user', parts: [{ text: prompt }] },
     ];
-    const schema: SchemaUnion = {
-      type: Type.OBJECT,
+    const schema: Record<string, unknown> = {
+      type: 'object',
       properties: {
         reasoning: {
-          type: Type.STRING,
+          type: 'string',
           description:
             'Your reasoning on if the conversation is looping without forward progress.',
         },
         confidence: {
-          type: Type.NUMBER,
+          type: 'number',
           description:
             'A number between 0.0 and 1.0 representing your confidence that the conversation is in an unproductive state.',
         },
diff --git a/packages/core/src/utils/editCorrector.ts b/packages/core/src/utils/editCorrector.ts
index 0ef8d4fe..faa52b51 100644
--- a/packages/core/src/utils/editCorrector.ts
+++ b/packages/core/src/utils/editCorrector.ts
@@ -4,12 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import {
-  Content,
-  GenerateContentConfig,
-  SchemaUnion,
-  Type,
-} from '@google/genai';
+import { Content, GenerateContentConfig } from '@google/genai';
 import { GeminiClient } from '../core/client.js';
 import { EditToolParams, EditTool } from '../tools/edit.js';
 import { WriteFileTool } from '../tools/write-file.js';
@@ -364,11 +359,11 @@ export async function ensureCorrectFileContent(
 }
 
 // Define the expected JSON schema for the LLM response for old_string correction
-const OLD_STRING_CORRECTION_SCHEMA: SchemaUnion = {
-  type: Type.OBJECT,
+const OLD_STRING_CORRECTION_SCHEMA: Record<string, unknown> = {
+  type: 'object',
   properties: {
     corrected_target_snippet: {
-      type: Type.STRING,
+      type: 'string',
       description:
         'The corrected version of the target snippet that exactly and uniquely matches a segment within the provided file content.',
     },
@@ -438,11 +433,11 @@ Return ONLY the corrected target snippet in the specified JSON format with the k
 }
 
 // Define the expected JSON schema for the new_string correction LLM response
-const NEW_STRING_CORRECTION_SCHEMA: SchemaUnion = {
-  type: Type.OBJECT,
+const NEW_STRING_CORRECTION_SCHEMA: Record<string, unknown> = {
+  type: 'object',
   properties: {
     corrected_new_string: {
-      type: Type.STRING,
+      type: 'string',
       description:
         'The original_new_string adjusted to be a suitable replacement for the corrected_old_string, while maintaining the original intent of the change.',
     },
@@ -521,11 +516,11 @@ Return ONLY the corrected string in the specified JSON format with the key 'corr
   }
 }
 
-const CORRECT_NEW_STRING_ESCAPING_SCHEMA: SchemaUnion = {
-  type: Type.OBJECT,
+const CORRECT_NEW_STRING_ESCAPING_SCHEMA: Record<string, unknown> = {
+  type: 'object',
   properties: {
     corrected_new_string_escaping: {
-      type: Type.STRING,
+      type: 'string',
       description:
         'The new_string with corrected escaping, ensuring it is a proper replacement for the old_string, especially considering potential over-escaping issues from previous LLM generations.',
     },
@@ -593,11 +588,11 @@ Return ONLY the corrected string in the specified JSON format with the key 'corr
   }
 }
 
-const CORRECT_STRING_ESCAPING_SCHEMA: SchemaUnion = {
-  type: Type.OBJECT,
+const CORRECT_STRING_ESCAPING_SCHEMA: Record<string, unknown> = {
+  type: 'object',
   properties: {
     corrected_string_escaping: {
-      type: Type.STRING,
+      type: 'string',
       description:
         'The string with corrected escaping, ensuring it is valid, specially considering potential over-escaping issues from previous LLM generations.',
     },
diff --git a/packages/core/src/utils/nextSpeakerChecker.ts b/packages/core/src/utils/nextSpeakerChecker.ts
index 8497db61..4ae8f437 100644
--- a/packages/core/src/utils/nextSpeakerChecker.ts
+++ b/packages/core/src/utils/nextSpeakerChecker.ts
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { Content, SchemaUnion, Type } from '@google/genai';
+import { Content } from '@google/genai';
 import { DEFAULT_GEMINI_FLASH_MODEL } from '../config/models.js';
 import { GeminiClient } from '../core/client.js';
 import { GeminiChat } from '../core/geminiChat.js';
@@ -16,16 +16,16 @@ const CHECK_PROMPT = `Analyze *only* the content and structure of your immediate
 2.  **Question to User:** If your last response ends with a direct question specifically addressed *to the user*, then the **'user'** should speak next.
 3.  **Waiting for User:** If your last response completed a thought, statement, or task *and* does not meet the criteria for Rule 1 (Model Continues) or Rule 2 (Question to User), it implies a pause expecting user input or reaction. In this case, the **'user'** should speak next.`;
 
-const RESPONSE_SCHEMA: SchemaUnion = {
-  type: Type.OBJECT,
+const RESPONSE_SCHEMA: Record<string, unknown> = {
+  type: 'object',
   properties: {
     reasoning: {
-      type: Type.STRING,
+      type: 'string',
       description:
         "Brief explanation justifying the 'next_speaker' choice based *strictly* on the applicable rule and the content/structure of the preceding turn.",
     },
     next_speaker: {
-      type: Type.STRING,
+      type: 'string',
       enum: ['user', 'model'],
       description:
         'Who should speak next based *only* on the preceding turn and the decision rules',