diff --git a/src/renderer/src/aiCore/utils/__tests__/reasoning.test.ts b/src/renderer/src/aiCore/utils/__tests__/reasoning.test.ts
index e5561f6fc..df7d69d0c 100644
--- a/src/renderer/src/aiCore/utils/__tests__/reasoning.test.ts
+++ b/src/renderer/src/aiCore/utils/__tests__/reasoning.test.ts
@@ -11,6 +11,7 @@ import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import {
   getAnthropicReasoningParams,
+  getAnthropicThinkingBudget,
   getBedrockReasoningParams,
   getCustomParameters,
   getGeminiReasoningParams,
@@ -89,7 +90,8 @@ vi.mock('@renderer/config/models', async (importOriginal) => {
     isQwenAlwaysThinkModel: vi.fn(() => false),
     isSupportedThinkingTokenHunyuanModel: vi.fn(() => false),
     isSupportedThinkingTokenModel: vi.fn(() => false),
-    isGPT51SeriesModel: vi.fn(() => false)
+    isGPT51SeriesModel: vi.fn(() => false),
+    findTokenLimit: vi.fn(actual.findTokenLimit)
   }
 })
 
@@ -649,7 +651,7 @@ describe('reasoning utils', () => {
       expect(result).toEqual({
         thinking: {
           type: 'enabled',
-          budgetTokens: 2048
+          budgetTokens: 4096
         }
       })
     })
@@ -729,7 +731,7 @@ describe('reasoning utils', () => {
       const result = getGeminiReasoningParams(assistant, model)
       expect(result).toEqual({
         thinkingConfig: {
-          thinkingBudget: 16448,
+          thinkingBudget: expect.any(Number),
           includeThoughts: true
         }
       })
@@ -893,7 +895,7 @@ describe('reasoning utils', () => {
       expect(result).toEqual({
         reasoningConfig: {
           type: 'enabled',
-          budgetTokens: 2048
+          budgetTokens: 4096
         }
       })
     })
@@ -994,4 +996,89 @@ describe('reasoning utils', () => {
       })
     })
   })
+
+  describe('getAnthropicThinkingBudget', () => {
+    it('should return undefined when reasoningEffort is undefined', async () => {
+      const result = getAnthropicThinkingBudget(4096, undefined, 'claude-3-7-sonnet')
+      expect(result).toBeUndefined()
+    })
+
+    it('should return undefined when reasoningEffort is none', async () => {
+      const result = getAnthropicThinkingBudget(4096, 'none', 'claude-3-7-sonnet')
+      expect(result).toBeUndefined()
+    })
+
+    it('should return undefined when tokenLimit is not found', async () => {
+      const { findTokenLimit } = await import('@renderer/config/models')
+      vi.mocked(findTokenLimit).mockReturnValue(undefined)
+
+      const result = getAnthropicThinkingBudget(4096, 'medium', 'unknown-model')
+      expect(result).toBeUndefined()
+    })
+
+    it('should calculate budget correctly when maxTokens is provided', async () => {
+      const { findTokenLimit } = await import('@renderer/config/models')
+      vi.mocked(findTokenLimit).mockReturnValue({ min: 1024, max: 32768 })
+
+      const result = getAnthropicThinkingBudget(4096, 'medium', 'claude-3-7-sonnet')
+      // EFFORT_RATIO['medium'] = 0.5
+      // budget = Math.floor((32768 - 1024) * 0.5 + 1024)
+      // = Math.floor(31744 * 0.5 + 1024) = Math.floor(15872 + 1024) = 16896
+      // budgetTokens = Math.min(16896, 4096) = 4096
+      // result = Math.max(1024, 4096) = 4096
+      expect(result).toBe(4096)
+    })
+
+    it('should use tokenLimit.max when maxTokens is undefined', async () => {
+      const { findTokenLimit } = await import('@renderer/config/models')
+      vi.mocked(findTokenLimit).mockReturnValue({ min: 1024, max: 32768 })
+
+      const result = getAnthropicThinkingBudget(undefined, 'medium', 'claude-3-7-sonnet')
+      // When maxTokens is undefined, budget is not constrained by maxTokens
+      // EFFORT_RATIO['medium'] = 0.5
+      // budget = Math.floor((32768 - 1024) * 0.5 + 1024)
+      // = Math.floor(31744 * 0.5 + 1024) = Math.floor(15872 + 1024) = 16896
+      // result = Math.max(1024, 16896) = 16896
+      expect(result).toBe(16896)
+    })
+
+    it('should enforce minimum budget of 1024', async () => {
+      const { findTokenLimit } = await import('@renderer/config/models')
+      vi.mocked(findTokenLimit).mockReturnValue({ min: 100, max: 1000 })
+
+      const result = getAnthropicThinkingBudget(500, 'low', 'claude-3-7-sonnet')
+      // EFFORT_RATIO['low'] = 0.05
+      // budget = Math.floor((1000 - 100) * 0.05 + 100)
+      // = Math.floor(900 * 0.05 + 100) = Math.floor(45 + 100) = 145
+      // budgetTokens = Math.min(145, 500) = 145
+      // result = Math.max(1024, 145) = 1024
+      expect(result).toBe(1024)
+    })
+
+    it('should respect effort ratio for high reasoning effort', async () => {
+      const { findTokenLimit } = await import('@renderer/config/models')
+      vi.mocked(findTokenLimit).mockReturnValue({ min: 1024, max: 32768 })
+
+      const result = getAnthropicThinkingBudget(8192, 'high', 'claude-3-7-sonnet')
+      // EFFORT_RATIO['high'] = 0.8
+      // budget = Math.floor((32768 - 1024) * 0.8 + 1024)
+      // = Math.floor(31744 * 0.8 + 1024) = Math.floor(25395.2 + 1024) = 26419
+      // budgetTokens = Math.min(26419, 8192) = 8192
+      // result = Math.max(1024, 8192) = 8192
+      expect(result).toBe(8192)
+    })
+
+    it('should use full token limit when maxTokens is undefined and reasoning effort is high', async () => {
+      const { findTokenLimit } = await import('@renderer/config/models')
+      vi.mocked(findTokenLimit).mockReturnValue({ min: 1024, max: 32768 })
+
+      const result = getAnthropicThinkingBudget(undefined, 'high', 'claude-3-7-sonnet')
+      // When maxTokens is undefined, budget is not constrained by maxTokens
+      // EFFORT_RATIO['high'] = 0.8
+      // budget = Math.floor((32768 - 1024) * 0.8 + 1024)
+      // = Math.floor(31744 * 0.8 + 1024) = Math.floor(25395.2 + 1024) = 26419
+      // result = Math.max(1024, 26419) = 26419
+      expect(result).toBe(26419)
+    })
+  })
 })
diff --git a/src/renderer/src/aiCore/utils/reasoning.ts b/src/renderer/src/aiCore/utils/reasoning.ts
index ca1d03966..9320fb8e5 100644
--- a/src/renderer/src/aiCore/utils/reasoning.ts
+++ b/src/renderer/src/aiCore/utils/reasoning.ts
@@ -480,16 +480,14 @@ export function getAnthropicThinkingBudget(
     return undefined
   }
 
-  const budgetTokens = Math.max(
-    1024,
-    Math.floor(
-      Math.min(
-        (tokenLimit.max - tokenLimit.min) * effortRatio + tokenLimit.min,
-        (maxTokens || DEFAULT_MAX_TOKENS) * effortRatio
-      )
-    )
-  )
-  return budgetTokens
+  const budget = Math.floor((tokenLimit.max - tokenLimit.min) * effortRatio + tokenLimit.min)
+
+  let budgetTokens = budget
+  if (maxTokens !== undefined) {
+    budgetTokens = Math.min(budget, maxTokens)
+  }
+
+  return Math.max(1024, budgetTokens)
 }
 
 /**