diff --git a/app.go b/app.go
index d0bfcfb..284fb50 100644
--- a/app.go
+++ b/app.go
@@ -3,6 +3,8 @@ package main
 import (
 	"context"
 	"fmt"
+	"os/exec"
+	"strings"
 	"os"
 	"path/filepath"
 	"sync"
@@ -66,12 +68,67 @@ func NewApp() *App {
 // startup is called by Wails when the app starts
 func (a *App) startup(ctx context.Context) {
 	a.ctx = ctx
-	a.cfg = config.Load(".env")
+	a.cfg = config.LoadFromFile()
 	for i, letter := range []string{"A", "B", "C", "D"} {
 		a.slots[i] = SlotState{Slot: letter, Status: "idle"}
 	}
 }
 
+// SaveConfig persists config to user config dir and updates in-memory config
+func (a *App) SaveConfig(cfg config.Config) error {
+	if err := config.Save(cfg); err != nil {
+		return err
+	}
+	a.mu.Lock()
+	a.cfg = cfg
+	a.mu.Unlock()
+	return nil
+}
+
+// GetConfigPath returns where the config is stored (for display)
+func (a *App) GetConfigPath() string {
+	return config.Path()
+}
+
+// PickLocalDest opens native folder picker, returns selected path or "" if cancelled
+func (a *App) PickLocalDest() (string, error) {
+	path, err := runtime.OpenDirectoryDialog(a.ctx, runtime.OpenDialogOptions{
+		Title: "Dossier de destination locale",
+	})
+	return path, err
+}
+
+// ListS3Buckets runs `aws s3api list-buckets --profile <p>` returns []string
+func (a *App) ListS3Buckets(profile string) ([]string, error) {
+	args := []string{"s3api", "list-buckets", "--query", "Buckets[].Name", "--output", "text"}
+	if profile != "" {
+		args = append(args, "--profile", profile)
+	}
+	out, err := exec.Command("aws", args...).CombinedOutput()
+	if err != nil {
+		return nil, fmt.Errorf("aws error: %s", strings.TrimSpace(string(out)))
+	}
+	raw := strings.TrimSpace(string(out))
+	if raw == "" || raw == "None" {
+		return []string{}, nil
+	}
+	parts := strings.Fields(raw)
+	return parts, nil
+}
+
+// TestS3Access checks bucket reachable: `aws s3 ls s3://<bucket>/ --profile <p>`
+func (a *App) TestS3Access(bucket, profile string) error {
+	args := []string{"s3", "ls", "s3://" + bucket + "/"}
+	if profile != "" {
+		args = append(args, "--profile", profile)
+	}
+	out, err := exec.Command("aws", args...).CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("accès refusé: %s", strings.TrimSpace(string(out)))
+	}
+	return nil
+}
+
 // ScanCards returns up to 4 detected SD cards
 func (a *App) ScanCards() []detect.SDCard {
 	cards := detect.Detect()
diff --git a/frontend/src/App.svelte b/frontend/src/App.svelte
index 29904bf..ce38ed9 100644
--- a/frontend/src/App.svelte
+++ b/frontend/src/App.svelte
@@ -1,12 +1,25 @@
 <script lang="ts">
   import { onMount } from 'svelte';
-  import { ScanCards, StartIngest, CancelIngest, GetSnapshot, SetDryRun, LoadConfig } from '../wailsjs/go/main/App';
+  import { ScanCards, StartIngest, CancelIngest, GetSnapshot, SetDryRun, LoadConfig, SaveConfig, GetConfigPath, PickLocalDest, ListS3Buckets, TestS3Access } from '../wailsjs/go/main/App';
   import { EventsOn } from '../wailsjs/runtime/runtime';
 
   let cards: any[] = [];
   let snapshot: any = { slots: [], running: false, dryRun: false, sessionID: '', config: {} };
   let dryRun = false;
 
+  // Settings modal
+  let showSettings = false;
+  let settingsMsg = '';
+  let cfgPath = '';
+  let s3TestResult = '';
+  let s3TestOk: boolean | null = null;
+  let bucketList: string[] = [];
+  let loadingBuckets = false;
+  let savingConfig = false;
+
+  // Local editable config
+  let editCfg = { s3Bucket: '', localDest: '', awsProfile: 'cosma', concurrency: 4 };
+
   async function refresh() {
     cards = await ScanCards();
     snapshot = await GetSnapshot();
@@ -27,11 +40,74 @@
     SetDryRun(dryRun);
   }
 
-  onMount(() => {
-    refresh();
+  async function openSettings() {
+    editCfg = {
+      s3Bucket: snapshot.config?.s3Bucket || '',
+      localDest: snapshot.config?.localDest || '',
+      awsProfile: snapshot.config?.awsProfile || 'cosma',
+      concurrency: snapshot.config?.concurrency || 4,
+    };
+    cfgPath = await GetConfigPath();
+    s3TestResult = '';
+    s3TestOk = null;
+    bucketList = [];
+    settingsMsg = '';
+    showSettings = true;
+  }
+
+  async function pickFolder() {
+    const p = await PickLocalDest();
+    if (p) editCfg.localDest = p;
+  }
+
+  async function listBuckets() {
+    loadingBuckets = true;
+    bucketList = [];
+    try {
+      bucketList = await ListS3Buckets(editCfg.awsProfile);
+    } catch (e: any) {
+      bucketList = [];
+    }
+    loadingBuckets = false;
+  }
+
+  async function testS3() {
+    s3TestResult = 'Test en cours...';
+    s3TestOk = null;
+    try {
+      await TestS3Access(editCfg.s3Bucket, editCfg.awsProfile);
+      s3TestResult = 'Acces OK';
+      s3TestOk = true;
+    } catch (e: any) {
+      s3TestResult = e?.message || 'Erreur acces S3';
+      s3TestOk = false;
+    }
+  }
+
+  async function saveSettings() {
+    savingConfig = true;
+    try {
+      await SaveConfig(editCfg);
+      await refresh();
+      showSettings = false;
+    } catch (e: any) {
+      settingsMsg = 'Erreur: ' + (e?.message || String(e));
+    }
+    savingConfig = false;
+  }
+
+  onMount(async () => {
+    await refresh();
     const t = setInterval(refresh, 3000);
     EventsOn('slot-update', () => refresh());
     EventsOn('session-done', () => refresh());
+
+    // Auto-open settings if no bucket configured
+    if (!snapshot.config?.s3Bucket) {
+      settingsMsg = 'Configure d abord ton bucket S3 et le dossier local.';
+      await openSettings();
+    }
+
     return () => clearInterval(t);
   });
 
@@ -52,12 +128,29 @@
   <header class="flex items-center justify-between border-b border-slate-700 pb-4">
     <div>
       <h1 class="text-3xl font-bold text-cyan-400">field-sync</h1>
-      <p class="text-sm text-slate-400">Cosma terrain · SD → local + S3</p>
+      <p class="text-sm text-slate-400">Cosma terrain &middot; SD &rarr; local + S3</p>
     </div>
-    <div class="text-right text-xs text-slate-400">
-      <div>Session: <span class="text-slate-200">{snapshot.sessionID || '—'}</span></div>
-      <div>Bucket: <span class="text-slate-200">{snapshot.config?.s3Bucket || '—'}</span></div>
-      <div>Dest: <span class="text-slate-200">{snapshot.config?.localDest || '—'}</span></div>
+    <div class="flex flex-col items-end gap-1">
+      <div class="text-sm font-semibold text-cyan-300">
+        <span class="text-slate-400 font-normal">Local:</span>
+        {#if snapshot.config?.localDest}
+          {snapshot.config.localDest}
+        {:else}
+          <span class="italic text-slate-500">non configure</span>
+        {/if}
+      </div>
+      <div class="text-sm font-semibold text-cyan-300">
+        <span class="text-slate-400 font-normal">S3:</span>
+        {#if snapshot.config?.s3Bucket}
+          s3://{snapshot.config.s3Bucket}/
+        {:else}
+          <span class="italic text-slate-500">non configure</span>
+        {/if}
+      </div>
+      <div class="text-xs text-slate-500">Session: {snapshot.sessionID || '—'}</div>
+      <button on:click={openSettings} class="mt-1 px-3 py-1 bg-slate-700 hover:bg-slate-600 rounded-lg text-sm font-semibold">
+        Reglages
+      </button>
     </div>
   </header>
 
@@ -99,26 +192,116 @@
             </div>
           </div>
           {#if s.speedMBs}<div class="text-xs text-slate-400">{s.speedMBs.toFixed(1)} MB/s</div>{/if}
-          {#if s.error}<div class="text-xs text-red-400 mt-1">⚠ {s.error}</div>{/if}
+          {#if s.error}<div class="text-xs text-red-400 mt-1">Erreur: {s.error}</div>{/if}
         </div>
       </div>
     {/each}
   </section>
 
   <footer class="flex gap-3 items-center mt-auto border-t border-slate-700 pt-4">
-    <button on:click={refresh} class="px-5 py-3 bg-slate-700 hover:bg-slate-600 rounded-lg font-semibold">↻ Rescan</button>
+    <button on:click={refresh} class="px-5 py-3 bg-slate-700 hover:bg-slate-600 rounded-lg font-semibold">Rescan</button>
     <button on:click={start} disabled={snapshot.running || cards.length===0}
             class="px-6 py-3 bg-cyan-600 hover:bg-cyan-500 disabled:bg-slate-700 disabled:text-slate-500 rounded-lg font-bold text-lg">
-      ▶ START INGEST
+      START INGEST
     </button>
     <button on:click={cancel} disabled={!snapshot.running}
             class="px-5 py-3 bg-red-700 hover:bg-red-600 disabled:bg-slate-700 disabled:text-slate-500 rounded-lg font-semibold">
-      ✕ Cancel
+      Cancel
     </button>
     <label class="flex items-center gap-2 ml-4 text-sm cursor-pointer">
       <input type="checkbox" bind:checked={dryRun} on:change={toggleDryRun} class="w-4 h-4">
       Dry-run
     </label>
-    <div class="ml-auto text-xs text-slate-500">{cards.length} carte(s) détectée(s)</div>
+    <div class="ml-auto text-xs text-slate-500">{cards.length} carte(s) detectee(s)</div>
   </footer>
 </div>
+
+<!-- Settings Modal -->
+{#if showSettings}
+  <div class="fixed inset-0 bg-black/70 flex items-center justify-center z-50 p-4">
+    <div class="bg-slate-900 rounded-2xl border border-slate-600 shadow-2xl w-full max-w-lg p-6 flex flex-col gap-4">
+      <h2 class="text-xl font-bold text-cyan-300">Reglages</h2>
+
+      {#if settingsMsg}
+        <div class="text-sm text-amber-400 bg-amber-900/30 rounded-lg px-3 py-2">{settingsMsg}</div>
+      {/if}
+
+      <!-- Config path -->
+      <div>
+        <label class="text-xs text-slate-500 mb-1 block">Fichier config (info)</label>
+        <div class="text-xs text-slate-400 bg-slate-800 rounded px-3 py-2 font-mono truncate">{cfgPath || '...'}</div>
+      </div>
+
+      <!-- Local dest -->
+      <div>
+        <label class="text-xs text-slate-400 mb-1 block font-semibold">Dossier local</label>
+        <div class="flex gap-2">
+          <input type="text" bind:value={editCfg.localDest} placeholder="ex: C:\field-sync-data"
+                 class="flex-1 bg-slate-800 border border-slate-600 rounded-lg px-3 py-2 text-sm text-slate-200 focus:outline-none focus:border-cyan-500" />
+          <button on:click={pickFolder} class="px-3 py-2 bg-slate-700 hover:bg-slate-600 rounded-lg text-sm font-semibold whitespace-nowrap">
+            Parcourir...
+          </button>
+        </div>
+      </div>
+
+      <!-- AWS Profile -->
+      <div>
+        <label class="text-xs text-slate-400 mb-1 block font-semibold">Profil AWS</label>
+        <input type="text" bind:value={editCfg.awsProfile} placeholder="cosma"
+               class="w-full bg-slate-800 border border-slate-600 rounded-lg px-3 py-2 text-sm text-slate-200 focus:outline-none focus:border-cyan-500" />
+      </div>
+
+      <!-- S3 Bucket -->
+      <div>
+        <label class="text-xs text-slate-400 mb-1 block font-semibold">Bucket S3</label>
+        <div class="flex gap-2 mb-2">
+          <input type="text" bind:value={editCfg.s3Bucket} placeholder="mon-bucket"
+                 class="flex-1 bg-slate-800 border border-slate-600 rounded-lg px-3 py-2 text-sm text-slate-200 focus:outline-none focus:border-cyan-500" />
+          <button on:click={listBuckets} disabled={loadingBuckets}
+                  class="px-3 py-2 bg-slate-700 hover:bg-slate-600 disabled:opacity-50 rounded-lg text-sm font-semibold whitespace-nowrap">
+            {loadingBuckets ? '...' : 'Lister buckets'}
+          </button>
+        </div>
+        {#if bucketList.length > 0}
+          <select bind:value={editCfg.s3Bucket}
+                  class="w-full bg-slate-800 border border-slate-600 rounded-lg px-3 py-2 text-sm text-slate-200 focus:outline-none focus:border-cyan-500">
+            {#each bucketList as b}
+              <option value={b}>{b}</option>
+            {/each}
+          </select>
+        {/if}
+        <button on:click={testS3} disabled={!editCfg.s3Bucket}
+                class="mt-2 px-3 py-1.5 bg-slate-700 hover:bg-slate-600 disabled:opacity-50 rounded-lg text-sm font-semibold">
+          Tester acces S3
+        </button>
+        {#if s3TestResult}
+          <span class="ml-3 text-sm" class:text-emerald-400={s3TestOk === true} class:text-red-400={s3TestOk === false}>
+            {s3TestResult}
+          </span>
+        {/if}
+      </div>
+
+      <!-- Concurrency -->
+      <div>
+        <label class="text-xs text-slate-400 mb-1 block font-semibold">Concurrence (workers)</label>
+        <input type="number" min="1" max="16" bind:value={editCfg.concurrency}
+               class="w-24 bg-slate-800 border border-slate-600 rounded-lg px-3 py-2 text-sm text-slate-200 focus:outline-none focus:border-cyan-500" />
+      </div>
+
+      <!-- Buttons -->
+      {#if settingsMsg && settingsMsg.includes('Erreur')}
+        <div class="text-sm text-red-400">{settingsMsg}</div>
+      {/if}
+      <div class="flex gap-3 pt-2 border-t border-slate-700">
+        <button on:click={saveSettings} disabled={savingConfig}
+                class="flex-1 px-4 py-2 bg-cyan-600 hover:bg-cyan-500 disabled:opacity-50 rounded-lg font-bold text-sm">
+          {savingConfig ? 'Enregistrement...' : 'Enregistrer'}
+        </button>
+        <button on:click={() => { showSettings = false; settingsMsg = ''; }}
+                class="px-4 py-2 bg-slate-700 hover:bg-slate-600 rounded-lg font-semibold text-sm">
+          Annuler
+        </button>
+      </div>
+    </div>
+  </div>
+{/if}
diff --git a/internal/config/config.go b/internal/config/config.go
index 9a7debf..793a328 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -1,7 +1,9 @@
 package config
 
 import (
+	"encoding/json"
 	"os"
+	"path/filepath"
 	"strconv"
 
 	"github.com/joho/godotenv"
@@ -15,7 +17,52 @@ type Config struct {
 	Concurrency int    `json:"concurrency"`
 }
 
-// Load reads config from ENV (with optional .env file)
+// Path returns the cross-OS config file path
+func Path() string {
+	dir, _ := os.UserConfigDir()
+	return filepath.Join(dir, "field-sync", "config.json")
+}
+
+// Save writes config to disk (atomic)
+func Save(cfg Config) error {
+	p := Path()
+	if err := os.MkdirAll(filepath.Dir(p), 0755); err != nil {
+		return err
+	}
+	data, _ := json.MarshalIndent(cfg, "", "  ")
+	tmp := p + ".tmp"
+	if err := os.WriteFile(tmp, data, 0644); err != nil {
+		return err
+	}
+	return os.Rename(tmp, p)
+}
+
+// LoadFromFile reads from JSON config file (no .env)
+func LoadFromFile() Config {
+	data, err := os.ReadFile(Path())
+	if err != nil {
+		return Config{AWSProfile: "cosma", Concurrency: 4, LocalDest: defaultLocalDest()}
+	}
+	var c Config
+	json.Unmarshal(data, &c)
+	if c.Concurrency == 0 {
+		c.Concurrency = 4
+	}
+	if c.AWSProfile == "" {
+		c.AWSProfile = "cosma"
+	}
+	if c.LocalDest == "" {
+		c.LocalDest = defaultLocalDest()
+	}
+	return c
+}
+
+func defaultLocalDest() string {
+	home, _ := os.UserHomeDir()
+	return filepath.Join(home, "field-sync-data")
+}
+
+// Load reads config from ENV (with optional .env file) — kept for compat
 func Load(envFile string) Config {
 	_ = godotenv.Load(envFile) // ignore if missing