diff --git a/.gitignore b/.gitignore
index b2026fa..b1de687 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,3 +30,5 @@ dist-ssr
 .next/dev/trace
 .next/dev/cache/turbopack/23c46498/CURRENT
 .next/dev/cache/turbopack/23c46498/LOG
+.next/dev/cache/turbopack/23c46498/CURRENT
+.next/dev/cache/turbopack/23c46498/LOG
diff --git a/next-env.d.ts b/next-env.d.ts
index 9edff1c..c4b7818 100644
--- a/next-env.d.ts
+++ b/next-env.d.ts
@@ -1,6 +1,6 @@
 /// <reference types="next" />
 /// <reference types="next/image-types/global" />
-import "./.next/types/routes.d.ts";
+import "./.next/dev/types/routes.d.ts";
 
 // NOTE: This file should not be edited
 // see https://nextjs.org/docs/app/api-reference/config/typescript for more information.
diff --git a/package-lock.json b/package-lock.json
index 37f592e..4e8fd07 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -8,6 +8,7 @@
       "name": "plumeia",
       "version": "0.1.0",
       "dependencies": {
+        "@anthropic-ai/sdk": "^0.78.0",
         "@google/genai": "^1.38.0",
         "@prisma/adapter-pg": "^7.4.2",
         "@prisma/client": "^7.4.1",
@@ -17,6 +18,7 @@
         "lucide-react": "^0.563.0",
         "next": "16.1.6",
         "next-auth": "^5.0.0-beta.30",
+        "openai": "^6.25.0",
         "pg": "^8.19.0",
         "prisma": "^7.4.1",
         "react": "19.2.3",
@@ -52,6 +54,26 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
     },
+    "node_modules/@anthropic-ai/sdk": {
+      "version": "0.78.0",
+      "resolved": "https://registry.npmjs.org/@anthropic-ai/sdk/-/sdk-0.78.0.tgz",
+      "integrity": "sha512-PzQhR715td/m1UaaN5hHXjYB8Gl2lF9UVhrrGrZeysiF6Rb74Wc9GCB8hzLdzmQtBd1qe89F9OptgB9Za1Ib5w==",
+      "license": "MIT",
+      "dependencies": {
+        "json-schema-to-ts": "^3.1.1"
+      },
+      "bin": {
+        "anthropic-ai-sdk": "bin/cli"
+      },
+      "peerDependencies": {
+        "zod": "^3.25.0 || ^4.0.0"
+      },
+      "peerDependenciesMeta": {
+        "zod": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/@auth/core": {
       "version": "0.41.0",
       "resolved": "https://registry.npmjs.org/@auth/core/-/core-0.41.0.tgz",
@@ -273,6 +295,15 @@
         "node": ">=6.0.0"
       }
     },
+    "node_modules/@babel/runtime": {
+      "version": "7.28.6",
+      "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.28.6.tgz",
+      "integrity": "sha512-05WQkdpL9COIMz4LjTxGpPNCdlpyimKppYNoJ5Di5EUObifl8t4tuLuUBBZEpoLYOmfvIWrsp9fCl0HoPRVTdA==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=6.9.0"
+      }
+    },
     "node_modules/@babel/template": {
       "version": "7.28.6",
       "resolved": "https://registry.npmjs.org/@babel/template/-/template-7.28.6.tgz",
@@ -6008,6 +6039,19 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/json-schema-to-ts": {
+      "version": "3.1.1",
+      "resolved": "https://registry.npmjs.org/json-schema-to-ts/-/json-schema-to-ts-3.1.1.tgz",
+      "integrity": "sha512-+DWg8jCJG2TEnpy7kOm/7/AxaYoaRbjVB4LFZLySZlWn8exGs3A4OLJR966cVvU26N7X9TWxl+Jsw7dzAqKT6g==",
+      "license": "MIT",
+      "dependencies": {
+        "@babel/runtime": "^7.18.3",
+        "ts-algebra": "^2.0.0"
+      },
+      "engines": {
+        "node": ">=16"
+      }
+    },
     "node_modules/json-schema-traverse": {
       "version": "0.4.1",
       "resolved": "https://registry.npmjs.org/json-schema-traverse/-/json-schema-traverse-0.4.1.tgz",
@@ -6962,6 +7006,27 @@
       "integrity": "sha512-RdR9FQrFwNBNXAr4GixM8YaRZRJ5PUWbKYbE5eOsrwAjJW0q2REGcf79oYPsLyskQCZG1PLN+S/K1V00joZAoQ==",
       "license": "MIT"
     },
+    "node_modules/openai": {
+      "version": "6.25.0",
+      "resolved": "https://registry.npmjs.org/openai/-/openai-6.25.0.tgz",
+      "integrity": "sha512-mEh6VZ2ds2AGGokWARo18aPISI1OhlgdEIC1ewhkZr8pSIT31dec0ecr9Nhxx0JlybyOgoAT1sWeKtwPZzJyww==",
+      "license": "Apache-2.0",
+      "bin": {
+        "openai": "bin/cli"
+      },
+      "peerDependencies": {
+        "ws": "^8.18.0",
+        "zod": "^3.25 || ^4.0"
+      },
+      "peerDependenciesMeta": {
+        "ws": {
+          "optional": true
+        },
+        "zod": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/optionator": {
       "version": "0.9.4",
       "resolved": "https://registry.npmjs.org/optionator/-/optionator-0.9.4.tgz",
@@ -8472,6 +8537,12 @@
         "node": ">=8.0"
       }
     },
+    "node_modules/ts-algebra": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/ts-algebra/-/ts-algebra-2.0.0.tgz",
+      "integrity": "sha512-FPAhNPFMrkwz76P7cdjdmiShwMynZYN6SgOujD1urY4oNm80Ou9oMdmbR45LotcKOXoy7wSmHkRFE6Mxbrhefw==",
+      "license": "MIT"
+    },
     "node_modules/ts-api-utils": {
       "version": "2.4.0",
       "resolved": "https://registry.npmjs.org/ts-api-utils/-/ts-api-utils-2.4.0.tgz",
@@ -9056,7 +9127,7 @@
       "version": "4.3.6",
       "resolved": "https://registry.npmjs.org/zod/-/zod-4.3.6.tgz",
       "integrity": "sha512-rftlrkhHZOcjDwkGlnUtZZkvaPHCsDATp4pGpuOOMDaTdDDXF91wuVDJoWoPsKX/3YPQ5fHuF3STjcYyKr+Qhg==",
-      "dev": true,
+      "devOptional": true,
       "license": "MIT",
       "funding": {
         "url": "https://github.com/sponsors/colinhacks"
diff --git a/package.json b/package.json
index cbafdc3..deaa17b 100644
--- a/package.json
+++ b/package.json
@@ -12,6 +12,7 @@
     "lint": "next lint"
   },
   "dependencies": {
+    "@anthropic-ai/sdk": "^0.78.0",
     "@google/genai": "^1.38.0",
     "@prisma/adapter-pg": "^7.4.2",
     "@prisma/client": "^7.4.1",
@@ -21,6 +22,7 @@
     "lucide-react": "^0.563.0",
     "next": "16.1.6",
     "next-auth": "^5.0.0-beta.30",
+    "openai": "^6.25.0",
     "pg": "^8.19.0",
     "prisma": "^7.4.1",
     "react": "19.2.3",
diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 9feb9ff..a81cca8 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -40,6 +40,10 @@ model User {
   planId         String?  @default("free")
   subscriptionPlan Plan?  @relation(fields: [planId], references: [id])
   
+  // Bring Your Own Key
+  customApiProvider String?
+  customApiKey      String?
+  
   aiActionsUsed  Int      @default(0)
   dailyWordGoal  Int      @default(500)
   writingStreak  Int      @default(0)
diff --git a/prisma/seed.ts b/prisma/seed.ts
index df6fa76..f42ba8e 100644
--- a/prisma/seed.ts
+++ b/prisma/seed.ts
@@ -1,8 +1,13 @@
 import { config } from 'dotenv';
-config({ path: '.env.local' });
-import getDB from '../src/lib/prisma';
+config();
+import { PrismaClient } from '@prisma/client';
+import { PrismaPg } from '@prisma/adapter-pg';
+import { Pool } from 'pg';
 
-const prisma = getDB();
+const connectionString = process.env.DATABASE_URL;
+const pool = new Pool({ connectionString });
+const adapter = new PrismaPg(pool);
+const prisma = new PrismaClient({ adapter });
 
 async function main() {
     console.log('Seeding plans...');
@@ -41,6 +46,17 @@ async function main() {
             features: ['250 actions IA / mois', 'Accès Gemini 3 Pro', 'Bible du monde avancée', 'Outils de révision avancés'],
             isPopular: false,
         },
+        {
+            id: 'byok',
+            name: 'byok',
+            displayName: 'Clé Perso (BYOK)',
+            price: 4.99,
+            description: 'Utilisez vos propres clés API (ChatGPT, Claude, Gemini).',
+            maxProjects: -1,
+            maxAiActions: -1,
+            features: ['Tokens illimités via votre clé', 'Mode Bring Your Own Key', 'Choix du modèle IA', 'Projets illimités'],
+            isPopular: false,
+        },
     ];
 
     for (const plan of plans) {
diff --git a/src/app/api/user/profile/route.ts b/src/app/api/user/profile/route.ts
index 85f22ae..d29d4ce 100644
--- a/src/app/api/user/profile/route.ts
+++ b/src/app/api/user/profile/route.ts
@@ -54,6 +54,8 @@ export async function GET() {
         dailyWordGoal: user.dailyWordGoal,
         writingStreak: user.writingStreak,
         lastWriteDate: user.lastWriteDate,
+        customApiProvider: user.customApiProvider,
+        customApiKey: user.customApiKey,
         createdAt: user.createdAt,
         totalWords,
     });
@@ -78,6 +80,12 @@ export async function PUT(request: NextRequest) {
     if (body.dailyWordGoal !== undefined) data.dailyWordGoal = body.dailyWordGoal;
     if (body.writingStreak !== undefined) data.writingStreak = body.writingStreak;
     if (body.lastWriteDate !== undefined) data.lastWriteDate = body.lastWriteDate ? new Date(body.lastWriteDate) : null;
+    if (body.customApiProvider !== undefined) data.customApiProvider = body.customApiProvider;
+    if (body.customApiKey !== undefined) data.customApiKey = body.customApiKey;
+    if (body.planId !== undefined) {
+        data.planId = body.planId;
+        data.plan = body.planId; // legacy sync
+    }
 
     const updated = await prisma.user.update({
         where: { id: session.user.id },
diff --git a/src/app/checkout/page.tsx b/src/app/checkout/page.tsx
index 9bd6f47..1edd52d 100644
--- a/src/app/checkout/page.tsx
+++ b/src/app/checkout/page.tsx
@@ -1,15 +1,67 @@
 'use client';
 
 import Checkout from '@/components/Checkout';
-import { useRouter } from 'next/navigation';
+import { useRouter, useSearchParams } from 'next/navigation';
+import { useEffect, useState, Suspense } from 'react';
 
-export default function CheckoutPage() {
+function CheckoutContent() {
     const router = useRouter();
+    const searchParams = useSearchParams();
+    const planId = searchParams.get('plan') || 'pro';
+
+    const [plan, setPlan] = useState<{ id: string, displayName: string, price: number } | null>(null);
+
+    useEffect(() => {
+        fetch('/api/plans', { cache: 'no-store' })
+            .then(res => res.json())
+            .then(data => {
+                const found = data.find((p: any) => p.id === planId);
+                if (found) {
+                    setPlan(found);
+                } else {
+                    setPlan(data.find((p: any) => p.id === 'pro') || { id: 'pro', displayName: 'Auteur Pro', price: 12.00 });
+                }
+            })
+            .catch(err => {
+                console.error(err);
+                setPlan({ id: 'pro', displayName: 'Auteur Pro', price: 12.00 });
+            });
+    }, [planId]);
+
+    const handleComplete = async () => {
+        if (plan) {
+            try {
+                await fetch('/api/user/profile', {
+                    method: 'PUT',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({ planId: plan.id })
+                });
+                // Force a full reload to update user context in providers
+                window.location.href = '/dashboard';
+            } catch (err) {
+                console.error('Failed to update plan', err);
+                router.push('/dashboard');
+            }
+        } else {
+            router.push('/dashboard');
+        }
+    };
+
+    if (!plan) return <div className="min-h-screen bg-[#eef2ff] flex items-center justify-center p-8">Chargement...</div>;
 
     return (
         <Checkout
-            onComplete={() => router.push('/dashboard')}
+            plan={plan}
+            onComplete={handleComplete}
             onCancel={() => router.push('/pricing')}
         />
     );
 }
+
+export default function CheckoutPage() {
+    return (
+        <Suspense fallback={<div className="min-h-screen bg-[#eef2ff] flex items-center justify-center p-8">Chargement...</div>}>
+            <CheckoutContent />
+        </Suspense>
+    );
+}
diff --git a/src/app/pricing/page.tsx b/src/app/pricing/page.tsx
index c5e5227..31b3acc 100644
--- a/src/app/pricing/page.tsx
+++ b/src/app/pricing/page.tsx
@@ -31,7 +31,7 @@ export default function PricingPage() {
             isLoading={isLoading}
             currentPlan={user?.subscription.plan || 'free'}
             onBack={() => router.push(user ? '/dashboard' : '/')}
-            onSelectPlan={() => router.push(user ? '/checkout' : '/login')}
+            onSelectPlan={(id) => router.push(user ? `/checkout?plan=${id}` : '/login')}
         />
     );
 }
diff --git a/src/components/Checkout.tsx b/src/components/Checkout.tsx
index 6921112..1354d8b 100644
--- a/src/components/Checkout.tsx
+++ b/src/components/Checkout.tsx
@@ -6,11 +6,12 @@ import { CreditCard, Shield, Lock, ArrowRight, Loader2 } from 'lucide-react';
 import { useLanguage } from '@/providers/LanguageProvider';
 
 interface CheckoutProps {
+  plan: { id: string; displayName: string; price: number };
   onComplete: () => void;
   onCancel: () => void;
 }
 
-const Checkout: React.FC<CheckoutProps> = ({ onComplete, onCancel }) => {
+const Checkout: React.FC<CheckoutProps> = ({ plan, onComplete, onCancel }) => {
   const [loading, setLoading] = useState(false);
   const { t } = useLanguage();
 
@@ -28,10 +29,10 @@ const Checkout: React.FC<CheckoutProps> = ({ onComplete, onCancel }) => {
         <div className="w-full md:w-1/3 bg-slate-900 text-white p-8">
           <h3 className="text-xl font-bold mb-8 flex items-center gap-2"><Lock size={18} className="text-blue-400" /> {t('checkout.order')}</h3>
           <div className="space-y-4">
-            <div className="flex justify-between text-sm"><span>{t('checkout.pro_author')}</span><span>12.00€</span></div>
-            <div className="flex justify-between text-sm"><span>{t('checkout.vat')}</span><span>2.40€</span></div>
+            <div className="flex justify-between text-sm"><span>{plan.displayName}</span><span>{plan.price.toFixed(2)}€</span></div>
+            <div className="flex justify-between text-sm"><span>{t('checkout.vat')} (20%)</span><span>{(plan.price * 0.2).toFixed(2)}€</span></div>
             <div className="h-px bg-slate-800 my-4" />
-            <div className="flex justify-between text-xl font-black"><span>{t('checkout.total')}</span><span className="text-blue-400">14.40€</span></div>
+            <div className="flex justify-between text-xl font-black"><span>{t('checkout.total')}</span><span className="text-blue-400">{(plan.price * 1.2).toFixed(2)}€</span></div>
           </div>
         </div>
         <div className="flex-1 p-8 md:p-12">
diff --git a/src/components/UserProfileSettings.tsx b/src/components/UserProfileSettings.tsx
index 83634a5..7801150 100644
--- a/src/components/UserProfileSettings.tsx
+++ b/src/components/UserProfileSettings.tsx
@@ -6,6 +6,7 @@ import { UserProfile, UserPreferences } from '@/lib/types';
 import { User, Settings, Globe, Shield, Bell, Save, Camera, Target, Flame, Layout } from 'lucide-react';
 import { useLanguage } from '@/providers/LanguageProvider';
 import { LanguageSwitcher } from '@/components/LanguageSwitcher';
+import { useRouter } from 'next/navigation';
 
 interface UserProfileSettingsProps {
     user: UserProfile;
@@ -36,9 +37,13 @@ const UserProfileSettings: React.FC<UserProfileSettingsProps> = ({ user, onUpdat
             panel: '#24283b',
             text: '#c0caf5',
             accent: '#7aa2f7'
-        }
+        },
+        customApiProvider: user.customApiProvider || 'openai',
+        customApiKey: user.customApiKey || ''
     });
 
+    const router = useRouter();
+
     // Handle Live Preview of Theme Changes
     useEffect(() => {
         const root = document.documentElement;
@@ -114,7 +119,9 @@ const UserProfileSettings: React.FC<UserProfileSettingsProps> = ({ user, onUpdat
                 theme: formData.theme,
                 dailyWordGoal: formData.dailyWordGoal,
                 customColors: formData.customColors
-            }
+            },
+            customApiProvider: formData.customApiProvider as any,
+            customApiKey: formData.customApiKey
         });
 
         localStorage.setItem('plumeia_theme', formData.theme);
@@ -296,7 +303,12 @@ const UserProfileSettings: React.FC<UserProfileSettingsProps> = ({ user, onUpdat
                                         <h4 className="font-bold text-blue-900">{t('profile.plan_title')} {(user.subscription.planDetails?.displayName || user.subscription.plan).toUpperCase()}</h4>
                                         <p className="text-xs text-blue-700">{t('profile.active_sub')}</p>
                                     </div>
-                                    <button className="bg-blue-600 text-white px-4 py-2 rounded-lg text-xs font-bold hover:bg-blue-700 shadow-md shadow-blue-200">{t('profile.manage')}</button>
+                                    <button
+                                        onClick={() => router.push('/pricing')}
+                                        className="bg-blue-600 text-white px-4 py-2 rounded-lg text-xs font-bold hover:bg-blue-700 shadow-md shadow-blue-200"
+                                    >
+                                        {t('profile.manage')}
+                                    </button>
                                 </div>
 
                                 <div className="space-y-1">
@@ -309,7 +321,58 @@ const UserProfileSettings: React.FC<UserProfileSettingsProps> = ({ user, onUpdat
                                     />
                                 </div>
 
-                                <div className="pt-4">
+                                {/* BYOK Settings */}
+                                {user.subscription.plan === 'byok' && (
+                                    <div className={`p-6 rounded-xl border mt-8 ${isCustom ? 'border-theme-border bg-theme-panel' : isDark ? 'border-slate-700 bg-slate-800/50' : isSepia ? 'border-[#dfcdae] bg-[#f4ecd8]/50' : 'border-slate-200 bg-slate-50'}`}>
+                                        <h4 className={`font-bold mb-4 flex items-center gap-2 ${themeTextHeading}`}>
+                                            <Globe size={18} className="text-blue-500" /> Vos clés API (BYOK)
+                                        </h4>
+                                        <p className={`text-xs mb-6 ${themeTextMuted}`}>
+                                            Vous avez l'abonnement "Clé Perso". Vous pouvez utiliser l'IA en illimité en renseignant votre propre clé API.
+                                        </p>
+
+                                        <div className="space-y-4">
+                                            <div className="space-y-1">
+                                                <label className={`text-xs font-black uppercase tracking-widest ${themeTextMuted}`}>Fournisseur IA</label>
+                                                <select
+                                                    value={formData.customApiProvider}
+                                                    onChange={(e) => setFormData({ ...formData, customApiProvider: e.target.value as any })}
+                                                    className={`w-full p-3 rounded-xl outline-none focus:ring-2 focus:ring-blue-500 ${themeInputBg}`}
+                                                >
+                                                    <option value="openai">OpenAI (ChatGPT)</option>
+                                                    <option value="anthropic">Anthropic (Claude)</option>
+                                                    <option value="gemini">Google (Gemini)</option>
+                                                </select>
+                                            </div>
+
+                                            <div className="space-y-1">
+                                                <label className={`text-xs font-black uppercase tracking-widest ${themeTextMuted}`}>Clé API ({formData.customApiProvider === 'openai' ? 'sk-proj-...' : formData.customApiProvider === 'anthropic' ? 'sk-ant-...' : 'AIza...'})</label>
+                                                <input
+                                                    type="password"
+                                                    value={formData.customApiKey}
+                                                    onChange={(e) => setFormData({ ...formData, customApiKey: e.target.value })}
+                                                    placeholder="Collez votre clé secrète ici..."
+                                                    className={`w-full p-3 rounded-xl outline-none focus:ring-2 focus:ring-blue-500 font-mono text-sm ${themeInputBg}`}
+                                                />
+                                            </div>
+                                        </div>
+                                    </div>
+                                )}
+
+                                {user.subscription.plan !== 'byok' && user.subscription.plan !== 'master' && (
+                                    <div className="p-4 bg-indigo-50 border border-indigo-100 rounded-xl mt-8">
+                                        <h4 className="font-bold text-indigo-900 text-sm mb-1">Passer à l'abonnement "Clé Perso (BYOK)" ?</h4>
+                                        <p className="text-xs text-indigo-700 mb-3">Pour 4,99€/mois, utilisez vos propres clés API ChatGPT, Claude ou Gemini sans limite de tokens.</p>
+                                        <button
+                                            onClick={() => router.push('/pricing')}
+                                            className="bg-white text-indigo-600 px-4 py-2 rounded-lg text-xs font-bold border border-indigo-200 hover:bg-indigo-50 transition w-full"
+                                        >
+                                            Découvrir le plan BYOK
+                                        </button>
+                                    </div>
+                                )}
+
+                                <div className="pt-4 mt-8 pt-8 border-t border-red-100/20">
                                     <button className="text-red-500 text-sm font-bold hover:underline">{t('profile.delete_account')}</button>
                                 </div>
                             </div>
diff --git a/src/lib/gemini.ts b/src/lib/gemini.ts
index 9e3d371..f33f4e3 100644
--- a/src/lib/gemini.ts
+++ b/src/lib/gemini.ts
@@ -2,6 +2,8 @@
 // This file is only imported by API routes, never by client code
 
 import { GoogleGenAI, Type } from "@google/genai";
+import OpenAI from "openai";
+import Anthropic from "@anthropic-ai/sdk";
 import { BookProject, UserProfile } from "./types";
 
 const truncate = (str: string, length: number) => {
@@ -10,7 +12,8 @@ const truncate = (str: string, length: number) => {
 };
 
 const checkUsage = (user: UserProfile) => {
-    if (user.subscription.plan === 'master') return true;
+    // BYOK and Master plans have unlimited AI actions
+    if (user.subscription.plan === 'master' || user.subscription.plan === 'byok') return true;
     return user.usage.aiActionsCurrent < user.usage.aiActionsLimit;
 };
 
@@ -86,37 +89,77 @@ export const generateStoryContent = async (
     }
 
     try {
-        const ai = new GoogleGenAI({ apiKey: process.env.GEMINI_API_KEY });
         const finalPrompt = buildContextPrompt(project, currentChapterId, userPrompt);
 
-        const modelName = user.subscription.plan === 'master' ? 'gemini-3-pro-preview' : 'gemini-3-flash-preview';
+        // --- BYOK: Bring Your Own Key Logic ---
+        const isBYOK = user.subscription.plan === 'byok' && user.customApiKey;
+        const provider = isBYOK ? (user.customApiProvider || 'openai') : 'gemini';
 
-        const response = await ai.models.generateContent({
-            model: modelName,
-            contents: finalPrompt,
-            config: {
+        if (provider === 'openai' && isBYOK) {
+            const openai = new OpenAI({ apiKey: user.customApiKey });
+            const completion = await openai.chat.completions.create({
+                model: "gpt-4o-mini",
+                messages: [{ role: "user", content: finalPrompt }],
+                response_format: { type: "json_object" },
                 temperature: 0.7,
-                responseMimeType: "application/json",
-                responseSchema: {
-                    type: Type.OBJECT,
-                    properties: {
-                        responseType: {
-                            type: Type.STRING,
-                            enum: ["draft", "reflection"]
-                        },
-                        content: {
-                            type: Type.STRING
+            });
+            const result = JSON.parse(completion.choices[0].message.content || "{}");
+            return {
+                text: result.content || "Erreur de génération.",
+                type: result.responseType || "reflection"
+            };
+        }
+        else if (provider === 'anthropic' && isBYOK) {
+            const anthropic = new Anthropic({ apiKey: user.customApiKey });
+            // Anthropic doesn't have strict JSON mode matching OpenAI's structure natively at this tier, 
+            // so we prompt it to return JSON.
+            const systemPrompt = "You must respond in valid JSON format with exact keys: `responseType` (either 'draft' or 'reflection') and `content` (string).";
+            const message = await anthropic.messages.create({
+                model: "claude-3-haiku-20240320",
+                max_tokens: 4000,
+                system: systemPrompt,
+                messages: [{ role: "user", content: finalPrompt }],
+            });
+            const textContent = message.content[0].type === 'text' ? message.content[0].text : '{}';
+            const result = JSON.parse(textContent);
+            return {
+                text: result.content || "Erreur de génération.",
+                type: result.responseType || "reflection"
+            };
+        }
+        else {
+            // Default: Pluume Gemini implementation
+            const ai = new GoogleGenAI({ apiKey: isBYOK && user.customApiProvider === 'gemini' ? user.customApiKey : process.env.GEMINI_API_KEY });
+            const modelName = user.subscription.plan === 'master' ? 'gemini-3-pro-preview' : 'gemini-3-flash-preview';
+
+            const response = await ai.models.generateContent({
+                model: modelName,
+                contents: finalPrompt,
+                config: {
+                    temperature: 0.7,
+                    responseMimeType: "application/json",
+                    responseSchema: {
+                        type: Type.OBJECT,
+                        properties: {
+                            responseType: {
+                                type: Type.STRING,
+                                enum: ["draft", "reflection"]
+                            },
+                            content: {
+                                type: Type.STRING
+                            }
                         }
                     }
                 }
-            }
-        });
+            });
+
+            const result = JSON.parse(response.text || "{}");
+            return {
+                text: result.content || "Erreur de génération.",
+                type: result.responseType || "reflection"
+            };
+        }
 
-        const result = JSON.parse(response.text || "{}");
-        return {
-            text: result.content || "Erreur de génération.",
-            type: result.responseType || "reflection"
-        };
     } catch (error) {
         console.error("AI Generation Error:", error);
         return { text: "Erreur lors de la communication avec l'IA.", type: 'reflection' };
@@ -130,11 +173,35 @@ export const transformTextServer = async (
     user: UserProfile,
 ): Promise<string> => {
     if (!checkUsage(user)) return "Limite d'actions IA atteinte.";
+
     try {
-        const ai = new GoogleGenAI({ apiKey: process.env.GEMINI_API_KEY });
-        const prompt = `Action: ${mode}. Texte: ${text}. Contexte: ${truncate(context, 1000)}. Renvoie juste le texte transformé.`;
-        const response = await ai.models.generateContent({ model: 'gemini-3-flash-preview', contents: prompt });
-        return response.text?.trim() || text;
+        const prompt = `Action: ${mode}. Texte: ${text}. Contexte: ${truncate(context, 1000)}. Renvoie juste le texte transformé sans commentaires.`;
+
+        const isBYOK = user.subscription.plan === 'byok' && user.customApiKey;
+        const provider = isBYOK ? (user.customApiProvider || 'openai') : 'gemini';
+
+        if (provider === 'openai' && isBYOK) {
+            const openai = new OpenAI({ apiKey: user.customApiKey });
+            const completion = await openai.chat.completions.create({
+                model: "gpt-4o-mini",
+                messages: [{ role: "user", content: prompt }],
+            });
+            return completion.choices[0].message.content || text;
+        }
+        else if (provider === 'anthropic' && isBYOK) {
+            const anthropic = new Anthropic({ apiKey: user.customApiKey });
+            const message = await anthropic.messages.create({
+                model: "claude-3-haiku-20240320",
+                max_tokens: 4000,
+                messages: [{ role: "user", content: prompt }],
+            });
+            return message.content[0].type === 'text' ? message.content[0].text : text;
+        }
+        else {
+            const ai = new GoogleGenAI({ apiKey: isBYOK && user.customApiProvider === 'gemini' ? user.customApiKey : process.env.GEMINI_API_KEY });
+            const response = await ai.models.generateContent({ model: 'gemini-3-flash-preview', contents: prompt });
+            return response.text?.trim() || text;
+        }
     } catch {
         return text;
     }
diff --git a/src/lib/types.ts b/src/lib/types.ts
index 230611f..e8e0200 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -164,6 +164,9 @@ export interface UserPreferences {
   };
   dailyWordGoal: number;
   language: 'fr' | 'en';
+  customApiProvider?: 'openai' | 'anthropic' | 'gemini';
+  // We can store the masked key or omit it from the client
+  customApiKey?: string;
 }
 
 export interface UserStats {
@@ -182,6 +185,8 @@ export interface UserProfile {
   usage: UserUsage;
   preferences: UserPreferences;
   stats: UserStats;
+  customApiProvider?: 'openai' | 'anthropic' | 'gemini';
+  customApiKey?: string;
 }
 
 export type ViewMode = 'write' | 'world_building' | 'workflow' | 'settings' | 'preview' | 'ideas' | 'landing' | 'features' | 'pricing' | 'checkout' | 'dashboard' | 'auth' | 'signup' | 'profile';