diff --git a/src/shared/provider-preset-catalog.ts b/src/shared/provider-preset-catalog.ts
index ab2db76d..64728ebc 100644
--- a/src/shared/provider-preset-catalog.ts
+++ b/src/shared/provider-preset-catalog.ts
@@ -53,7 +53,7 @@ export interface ProviderPresetDefinition {
   icon?: string;
 }
 
-export const OPENROUTER_BASE_URL = 'https://openrouter.ai/api/v1';
+export const OPENROUTER_BASE_URL = 'https://openrouter.ai/api';
 export const ORCAROUTER_BASE_URL = 'https://api.orcarouter.ai/v1';
 
 /**
diff --git a/tests/unit/api/profile-writer-anthropic.test.ts b/tests/unit/api/profile-writer-anthropic.test.ts
index 5a497d98..0416c321 100644
--- a/tests/unit/api/profile-writer-anthropic.test.ts
+++ b/tests/unit/api/profile-writer-anthropic.test.ts
@@ -134,7 +134,7 @@ describe('profile-writer Anthropic direct', () => {
   it('preserves OpenRouter ANTHROPIC_API_KEY blank behavior', () => {
     const result = createApiProfile(
       'openrouter-test',
-      'https://openrouter.ai/api/v1',
+      'https://openrouter.ai/api',
       'sk-or-testkey',
       { default: 'anthropic/claude-opus-4.5', opus: 'anthropic/claude-opus-4.5', sonnet: 'anthropic/claude-opus-4.5', haiku: 'anthropic/claude-opus-4.5' }
     );
@@ -145,7 +145,7 @@ describe('profile-writer Anthropic direct', () => {
     const settings = JSON.parse(fs.readFileSync(settingsPath, 'utf8'));
 
     // OpenRouter: proxy mode with ANTHROPIC_API_KEY explicitly blank
-    expect(settings.env.ANTHROPIC_BASE_URL).toBe('https://openrouter.ai/api/v1');
+    expect(settings.env.ANTHROPIC_BASE_URL).toBe('https://openrouter.ai/api');
     expect(settings.env.ANTHROPIC_AUTH_TOKEN).toBe('sk-or-testkey');
     expect(settings.env.ANTHROPIC_API_KEY).toBe('');
   });
diff --git a/tests/unit/api/provider-presets.test.ts b/tests/unit/api/provider-presets.test.ts
index 69386dbe..d90ff2eb 100644
--- a/tests/unit/api/provider-presets.test.ts
+++ b/tests/unit/api/provider-presets.test.ts
@@ -1,6 +1,8 @@
-import { existsSync } from 'fs';
-import { resolve } from 'path';
+import { existsSync, mkdtempSync, readFileSync, rmSync } from 'fs';
+import { tmpdir } from 'os';
+import { join, resolve } from 'path';
 import { describe, expect, it } from 'bun:test';
+import { createApiProfile } from '../../../src/api/services/profile-writer';
 import {
   PROVIDER_PRESETS,
   getPresetById,
@@ -113,9 +115,44 @@ describe('provider-presets', () => {
     expect(isValidPresetId('te')).toBe(true);
   });
 
-  it('uses OpenRouter v1 as the OpenAI-compatible API root', () => {
+  it('uses OpenRouter /api (without /v1) as the Anthropic-compatible API root to avoid double /v1 404 in Claude Code (#1728)', () => {
     const preset = getPresetById('openrouter');
-    expect(preset?.baseUrl).toBe('https://openrouter.ai/api/v1');
+    expect(preset?.baseUrl).toBe('https://openrouter.ai/api');
+    const finalEndpoint = `${preset?.baseUrl}/v1/messages`;
+    expect(finalEndpoint).toBe('https://openrouter.ai/api/v1/messages');
+    expect(finalEndpoint).not.toContain('/v1/v1/');
+  });
+
+  it('generates an OpenRouter profile whose ANTHROPIC_BASE_URL does not duplicate /v1 (#1728)', () => {
+    const preset = getPresetById('openrouter');
+    expect(preset).toBeDefined();
+    const tempHome = mkdtempSync(join(tmpdir(), 'ccs-openrouter-tdd-'));
+    const prevCcsHome = process.env.CCS_HOME;
+    process.env.CCS_HOME = tempHome;
+    try {
+      const result = createApiProfile(
+        'openrouter-tdd',
+        preset!.baseUrl,
+        'sk-or-test-key',
+        {
+          default: preset!.defaultModel,
+          opus: preset!.defaultModel,
+          sonnet: preset!.defaultModel,
+          haiku: preset!.defaultModel,
+        }
+      );
+      expect(result.success).toBe(true);
+      const settings = JSON.parse(
+        readFileSync(join(tempHome, '.ccs', 'openrouter-tdd.settings.json'), 'utf8')
+      );
+      expect(settings.env.ANTHROPIC_BASE_URL).toBe('https://openrouter.ai/api');
+      expect(`${settings.env.ANTHROPIC_BASE_URL}/v1/messages`).toBe(
+        'https://openrouter.ai/api/v1/messages'
+      );
+    } finally {
+      process.env.CCS_HOME = prevCcsHome;
+      rmSync(tempHome, { recursive: true, force: true });
+    }
   });
 
   it('keeps Anthropic direct last in the recommended preset order and reuses the Claude logo', () => {