diff --git a/frontend/index.html b/frontend/index.html
index d71d476..24db269 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -771,8 +771,16 @@
       </div>
       <div class="editor-body help-body" id="help-body">
         <nav class="help-nav" id="help-nav">
-          <div class="help-nav-title">Sommaire</div>
-          <ul class="help-nav-list">
+          <div class="help-nav-header">
+            <div class="help-nav-title">Sommaire</div>
+            <button class="help-nav-toggle" id="help-nav-toggle" title="Afficher/Masquer le sommaire" aria-label="Menu sommaire">
+              <i data-lucide="menu" style="width:16px;height:16px"></i>
+            </button>
+          </div>
+          <div class="help-nav-search-wrap">
+            <input type="text" class="help-nav-search" id="help-nav-search" placeholder="Rechercher dans l'aide..." autocomplete="off" spellcheck="false">
+          </div>
+          <ul class="help-nav-list" id="help-nav-list">
                       <li><a href="#help-intro" class="help-nav-link">📘 Introduction</a></li>
                       <li><a href="#help-interface" class="help-nav-link">🧭 Interface</a></li>
                       <li><a href="#help-navigation" class="help-nav-link">🗺️ Navigation</a></li>
diff --git a/frontend/js/config.js b/frontend/js/config.js
index 2e1ec02..a8d8caa 100644
--- a/frontend/js/config.js
+++ b/frontend/js/config.js
@@ -211,57 +211,161 @@ function initHelpModal() {
 }
 
 function initHelpNavigation() {
-  const helpContent = document.querySelector(".help-content");
   const helpBody = document.getElementById("help-body");
-  const navLinks = document.querySelectorAll(".help-nav-link");
-  const navList = document.querySelector(".help-nav-list");
+  const navList = document.getElementById("help-nav-list");
+  const nav = document.getElementById("help-nav");
+  const searchInput = document.getElementById("help-nav-search");
+  const toggleBtn = document.getElementById("help-nav-toggle");
 
-  if (!helpContent || !helpBody || !navLinks.length) return;
+  if (!helpBody || !navList || !nav) return;
 
-  // Handle nav link clicks
-  navLinks.forEach((link) => {
+  const allLinks = [...navList.querySelectorAll(".help-nav-link")];
+
+  // ── Scroll to section and focus it ──
+  function scrollToSection(targetId) {
+    const section = document.getElementById(targetId);
+    if (!section) return;
+    section.scrollIntoView({ behavior: "smooth", block: "start" });
+    section.setAttribute("tabindex", "-1");
+    section.focus({ preventScroll: true });
+    // On mobile, collapse nav after selection
+    if (window.innerWidth <= 768 && nav) {
+      nav.classList.add("collapsed");
+    }
+  }
+
+  // ── Nav link click handler ──
+  allLinks.forEach((link) => {
     link.addEventListener("click", (e) => {
       e.preventDefault();
       const targetId = link.getAttribute("href").substring(1);
-      const targetSection = document.getElementById(targetId);
-      if (targetSection) {
-        targetSection.scrollIntoView({ behavior: "smooth", block: "start" });
-        // Focus the section for accessibility
-        targetSection.setAttribute("tabindex", "-1");
-        targetSection.focus({ preventScroll: true });
-      }
+      scrollToSection(targetId);
     });
   });
 
   // ── Keyboard navigation inside nav list ──
-  if (navList) {
-    navList.addEventListener("keydown", (e) => {
-      const items = [...navList.querySelectorAll(".help-nav-link")];
-      const currentIdx = items.indexOf(document.activeElement);
+  navList.addEventListener("keydown", (e) => {
+    const items = [...navList.querySelectorAll(".help-nav-link:not(.hidden)")];
+    if (!items.length) return;
+    const currentIdx = items.indexOf(document.activeElement);
 
-      if (e.key === "ArrowDown" || e.key === "ArrowRight") {
-        e.preventDefault();
-        const next = (currentIdx + 1) % items.length;
-        items[next].focus();
-      } else if (e.key === "ArrowUp" || e.key === "ArrowLeft") {
-        e.preventDefault();
-        const prev = (currentIdx - 1 + items.length) % items.length;
-        items[prev].focus();
-      } else if (e.key === "Home") {
-        e.preventDefault();
-        items[0].focus();
-      } else if (e.key === "End") {
-        e.preventDefault();
-        items[items.length - 1].focus();
+    if (e.key === "ArrowDown" || e.key === "ArrowRight") {
+      e.preventDefault();
+      const next = (currentIdx + 1) % items.length;
+      items[next].focus();
+    } else if (e.key === "ArrowUp" || e.key === "ArrowLeft") {
+      e.preventDefault();
+      const prev = (currentIdx - 1 + items.length) % items.length;
+      items[prev].focus();
+    } else if (e.key === "Home") {
+      e.preventDefault();
+      items[0].focus();
+    } else if (e.key === "End") {
+      e.preventDefault();
+      items[items.length - 1].focus();
+    } else if (e.key === "Enter" && currentIdx >= 0) {
+      e.preventDefault();
+      const targetId = items[currentIdx].getAttribute("href").substring(1);
+      scrollToSection(targetId);
+    }
+  });
+
+  // Make nav items focusable
+  navList.querySelectorAll("li").forEach((li) => li.setAttribute("role", "none"));
+
+  // ── Search filter ──
+  if (searchInput) {
+    searchInput.addEventListener("input", () => {
+      const q = searchInput.value.toLowerCase().trim();
+      allLinks.forEach((link) => {
+        const text = link.textContent.toLowerCase();
+        if (!q || text.includes(q)) {
+          link.classList.remove("hidden");
+        } else {
+          link.classList.add("hidden");
+        }
+      });
+      // Update active state for visible links
+      updateActiveLink();
+    });
+    // Clear search on Escape
+    searchInput.addEventListener("keydown", (e) => {
+      if (e.key === "Escape") {
+        searchInput.value = "";
+        searchInput.dispatchEvent(new Event("input"));
       }
     });
+  }
 
-    // Make nav items focusable
-    navList.querySelectorAll("li").forEach((li) => {
-      li.setAttribute("role", "none"); // remove listitem role for cleaner a11y
+  // ── Mobile toggle ──
+  if (toggleBtn) {
+    toggleBtn.addEventListener("click", () => {
+      nav.classList.toggle("collapsed");
+    });
+    // Start collapsed on mobile
+    if (window.innerWidth <= 768) {
+      nav.classList.add("collapsed");
+    }
+    window.addEventListener("resize", () => {
+      if (window.innerWidth > 768) {
+        nav.classList.remove("collapsed");
+      }
     });
   }
 
+  // ── Scroll spy (IntersectionObserver) ──
+  let observer;
+  function updateActiveLink() {
+    // Find the first visible section and highlight its link
+    const sections = [...document.querySelectorAll(".help-section")];
+    let activeId = null;
+    for (const section of sections) {
+      const rect = section.getBoundingClientRect();
+      const helpContent = document.querySelector(".help-content");
+      const contentRect = helpContent ? helpContent.getBoundingClientRect() : null;
+      // Section top is in the upper half of the viewport (or within content)
+      if (rect.top < (contentRect ? contentRect.top + 120 : 200)) {
+        activeId = section.id;
+      }
+    }
+    if (activeId) {
+      allLinks.forEach((link) => {
+        const isMatch = link.getAttribute("href") === `#${activeId}`;
+        link.classList.toggle("active", isMatch);
+      });
+    }
+  }
+
+  observer = new IntersectionObserver(
+    (entries) => {
+      // Find the entry most visible near the top
+      let bestEntry = null;
+      for (const entry of entries) {
+        if (entry.isIntersecting) {
+          if (!bestEntry || entry.boundingClientRect.top < bestEntry.boundingClientRect.top) {
+            bestEntry = entry;
+          }
+        }
+      }
+      if (bestEntry) {
+        const id = bestEntry.target.getAttribute("id");
+        allLinks.forEach((link) => {
+          const isMatch = link.getAttribute("href") === `#${id}`;
+          link.classList.toggle("active", isMatch);
+        });
+      }
+    },
+    {
+      root: helpBody,
+      rootMargin: "-10% 0px -75% 0px",
+      threshold: [0, 0.25, 0.5],
+    }
+  );
+
+  document.querySelectorAll(".help-section").forEach((section) => {
+    observer.observe(section);
+  });
+
   // ── Keyboard: Ctrl+↑/↓ inside help body to jump between sections ──
   helpBody.addEventListener("keydown", (e) => {
     if ((e.ctrlKey || e.metaKey) && (e.key === "ArrowDown" || e.key === "ArrowUp")) {
@@ -269,10 +373,11 @@ function initHelpNavigation() {
       const sections = [...document.querySelectorAll(".help-section")];
       const currentSection = sections.find((s) => {
         const rect = s.getBoundingClientRect();
-        return rect.top >= 0 && rect.top < 100;
+        const helpContent = document.querySelector(".help-content");
+        const contentRect = helpContent ? helpContent.getBoundingClientRect() : null;
+        return rect.top >= (contentRect ? contentRect.top : 0) && rect.top < (contentRect ? contentRect.top + 120 : 120);
       });
       if (!currentSection) return;
-
       const currentIdx = sections.indexOf(currentSection);
       if (e.key === "ArrowDown" && currentIdx < sections.length - 1) {
         sections[currentIdx + 1].scrollIntoView({ behavior: "smooth", block: "start" });
@@ -281,33 +386,6 @@ function initHelpNavigation() {
       }
     }
   });
-
-  // ── Scroll spy ──
-  const observer = new IntersectionObserver(
-    (entries) => {
-      entries.forEach((entry) => {
-        if (entry.isIntersecting) {
-          const id = entry.target.getAttribute("id");
-          navLinks.forEach((link) => {
-            if (link.getAttribute("href") === `#${id}`) {
-              navLinks.forEach((l) => l.classList.remove("active"));
-              link.classList.add("active");
-            }
-          });
-        }
-      });
-    },
-    {
-      root: helpBody,
-      rootMargin: "-20% 0px -70% 0px",
-      threshold: 0,
-    },
-  );
-
-  // Observe all sections
-  document.querySelectorAll(".help-section").forEach((section) => {
-    observer.observe(section);
-  });
 }
 
 function closeHelpModal() {
diff --git a/frontend/style.css b/frontend/style.css
index 456a681..a84d5dd 100644
--- a/frontend/style.css
+++ b/frontend/style.css
@@ -2183,14 +2183,23 @@ select {
   min-width: 260px;
   background: color-mix(in srgb, var(--bg-secondary) 94%, var(--bg-primary));
   border-right: 1px solid color-mix(in srgb, var(--border) 85%, transparent);
-  padding: 24px 0;
-  overflow: visible;
+  display: flex;
+  flex-direction: column;
   position: sticky;
   top: 0;
   align-self: flex-start;
-  max-height: none;
+  height: 100%;
+  max-height: calc(90vh - 57px);
   flex-shrink: 0;
   backdrop-filter: blur(12px);
+  overflow: hidden;
+}
+.help-nav-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 20px 16px 10px;
+  flex-shrink: 0;
 }
 .help-nav-title {
   font-family: "JetBrains Mono", monospace;
@@ -2199,27 +2208,62 @@ select {
   text-transform: uppercase;
   letter-spacing: 0.05em;
   color: var(--text-muted);
-  padding: 0 22px 14px;
-  border-bottom: 1px solid color-mix(in srgb, var(--border) 85%, transparent);
-  margin-bottom: 12px;
 }
+.help-nav-toggle {
+  display: none;
+  width: 32px; height: 32px;
+  padding: 0;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  background: transparent;
+  color: var(--text-secondary);
+  cursor: pointer;
+  align-items: center;
+  justify-content: center;
+}
+.help-nav-toggle:hover { color: var(--accent); border-color: var(--accent); }
+.help-nav-search-wrap {
+  padding: 0 12px 8px;
+  flex-shrink: 0;
+}
+.help-nav-search {
+  width: 100%;
+  padding: 7px 10px;
+  border: 1px solid var(--border);
+  border-radius: 8px;
+  background: var(--bg-primary);
+  color: var(--text-primary);
+  font-size: 0.78rem;
+  outline: none;
+  transition: border-color 0.2s;
+}
+.help-nav-search:focus {
+  border-color: var(--accent);
+}
+.help-nav-search::placeholder { color: var(--text-muted); }
 .help-nav-list {
   list-style: none;
   margin: 0;
-  padding: 0 12px;
+  padding: 0 12px 20px;
+  flex: 1;
+  overflow-y: auto;
+  overflow-x: hidden;
+  scrollbar-width: thin;
+  scrollbar-color: var(--border) transparent;
 }
 .help-nav-list li {
-  margin: 0 0 6px;
+  margin: 0 0 3px;
 }
 .help-nav-link {
   display: block;
-  padding: 10px 12px;
-  font-size: 0.88rem;
+  padding: 8px 12px;
+  font-size: 0.85rem;
   color: var(--text-secondary);
   text-decoration: none;
   transition: all 150ms ease;
   border: 1px solid transparent;
-  border-radius: 12px;
+  border-radius: 8px;
+  outline: none;
 }
 .help-nav-link:hover {
   color: var(--accent);
@@ -2228,6 +2272,11 @@ select {
   text-decoration: none;
   transform: translateX(2px);
 }
+.help-nav-link:focus-visible {
+  outline: 2px solid var(--accent);
+  outline-offset: -2px;
+  border-radius: 8px;
+}
 .help-nav-link.active {
   color: var(--accent);
   background: linear-gradient(135deg, color-mix(in srgb, var(--accent) 16%, transparent), color-mix(in srgb, var(--accent) 7%, transparent));
@@ -2235,6 +2284,9 @@ select {
   font-weight: 600;
   box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--accent) 10%, transparent);
 }
+.help-nav-link.hidden {
+  display: none;
+}
 
 .help-content {
   flex: 1;
@@ -6335,3 +6387,52 @@ body.popup-mode .content-area {
   color: var(--text-muted);
   margin-top: 6px;
 }
+
+/* ── Help Modal: Mobile responsive ── */
+@media (max-width: 768px) {
+  .help-container { max-width: 100%; height: 100vh; }
+  .help-container .editor-container {
+    max-width: 100%;
+    max-height: 100vh;
+    border-radius: 0;
+  }
+  .help-body {
+    flex-direction: column;
+    overflow-y: auto;
+  }
+  .help-nav {
+    width: 100%;
+    min-width: 100%;
+    max-height: none;
+    height: auto;
+    position: relative;
+    top: auto;
+    border-right: none;
+    border-bottom: 1px solid var(--border);
+    flex-shrink: 0;
+  }
+  .help-nav-header {
+    padding: 12px 16px 8px;
+  }
+  .help-nav-toggle {
+    display: inline-flex;  /* visible on mobile */
+  }
+  .help-nav.collapsed .help-nav-search-wrap,
+  .help-nav.collapsed .help-nav-list {
+    display: none;
+  }
+  .help-nav-list {
+    max-height: 40vh;
+    flex: none;
+    padding-bottom: 12px;
+  }
+  .help-content {
+    padding: 16px 12px 40px;
+  }
+  .help-hero {
+    flex-direction: column;
+    gap: 16px;
+  }
+  .help-hero-visual { display: none; }
+  .help-section { padding: 24px 0 20px; }
+}