diff --git a/doc/agent-smoke-cases.md b/doc/agent-smoke-cases.md
index e213c3b..49ab309 100644
--- a/doc/agent-smoke-cases.md
+++ b/doc/agent-smoke-cases.md
@@ -356,6 +356,31 @@ bash scripts/agent-smoke.sh --cdp-port 9222 --cases AGENT-CHROME-001,AGENT-CHROM
 2. 对应滑杆 `disabled=true`
 3. 提示文案明确说明该设置仅在 `智能预览` 下生效
 
+### AGENT-CHROME-018：图片预览应全屏覆盖并支持滚轮缩放
+
+范围：
+正文图片点击预览、全屏覆盖、再次点击关闭、滚轮缩放
+
+状态：
+当前不在默认批量脚本中；用例内会显式切到 `智能预览`
+
+建议目标：
+优先选列表前几条中正文自带图片的公开主题
+
+步骤：
+
+1. 打开任一主题抽屉
+2. 在 `选项` 中切到 `智能预览`
+3. 点击正文中的第一张图片
+4. 在预览层内滚轮向上缩放一次
+5. 再点击预览图片本身
+
+断言：
+
+1. 图片预览层应覆盖整个视口，而不是只局限在右侧抽屉宽度内
+2. 预览打开后再次点击预览图片本身，应立即关闭预览层
+3. 在预览层内滚轮缩放后，预览图片的缩放值应大于默认的 `1`
+
 ## 3. 记录格式
 
 执行完用例后，建议按下面格式留证据：
diff --git a/src/content.css b/src/content.css
index 30e05fa..1d7beec 100644
--- a/src/content.css
+++ b/src/content.css
@@ -42,6 +42,13 @@ body.ld-drawer-resizing * {
   pointer-events: none;
 }
 
+#ld-image-preview-root {
+  position: fixed;
+  inset: 0;
+  z-index: 2147483647;
+  pointer-events: none;
+}
+
 body.ld-drawer-resizing #ld-drawer-root,
 body.ld-drawer-resizing {
   transition: none !important;
@@ -82,10 +89,10 @@ body.ld-drawer-page-open #ld-drawer-root {
   pointer-events: auto;
 }
 
-#ld-drawer-root .ld-image-preview {
-  position: absolute;
+#ld-image-preview-root .ld-image-preview {
+  position: fixed;
   inset: 0;
-  z-index: 8;
+  z-index: 1;
   display: flex;
   align-items: center;
   justify-content: center;
@@ -94,13 +101,14 @@ body.ld-drawer-page-open #ld-drawer-root {
   backdrop-filter: blur(6px);
   opacity: 1;
   animation: ld-image-preview-fade-in 180ms ease-out;
+  pointer-events: auto;
 }
 
-#ld-drawer-root .ld-image-preview[hidden] {
+#ld-image-preview-root .ld-image-preview[hidden] {
   display: none !important;
 }
 
-#ld-drawer-root .ld-image-preview-close {
+#ld-image-preview-root .ld-image-preview-close {
   position: absolute;
   top: 14px;
   right: 18px;
@@ -115,13 +123,13 @@ body.ld-drawer-page-open #ld-drawer-root {
   transition: background-color 0.18s ease, border-color 0.18s ease, transform 0.18s ease;
 }
 
-#ld-drawer-root .ld-image-preview-close:hover {
+#ld-image-preview-root .ld-image-preview-close:hover {
   background: rgba(15, 23, 42, 0.58);
   border-color: rgba(255, 255, 255, 0.44);
   transform: translateY(-1px);
 }
 
-#ld-drawer-root .ld-image-preview-stage {
+#ld-image-preview-root .ld-image-preview-stage {
   display: flex;
   align-items: center;
   justify-content: center;
@@ -130,7 +138,7 @@ body.ld-drawer-page-open #ld-drawer-root {
   overflow: hidden;
 }
 
-#ld-drawer-root .ld-image-preview-image {
+#ld-image-preview-root .ld-image-preview-image {
   display: block;
   max-width: 100%;
   max-height: 100%;
@@ -143,18 +151,19 @@ body.ld-drawer-page-open #ld-drawer-root {
   transition: opacity 0.2s ease, transform 0.24s ease, box-shadow 0.24s ease;
   transform-origin: center center;
   will-change: transform;
+  cursor: zoom-out;
 }
 
-#ld-drawer-root .ld-image-preview-image.is-ready {
+#ld-image-preview-root .ld-image-preview-image.is-ready {
   opacity: 1;
   transform: translateY(0) scale(var(--ld-image-preview-scale, 1));
 }
 
-#ld-drawer-root .ld-image-preview.is-zoomed {
+#ld-image-preview-root .ld-image-preview.is-zoomed {
   cursor: zoom-out;
 }
 
-#ld-drawer-root .ld-image-preview.is-zoomed .ld-image-preview-image {
+#ld-image-preview-root .ld-image-preview.is-zoomed .ld-image-preview-image {
   box-shadow: 0 24px 54px rgba(0, 0, 0, 0.44);
 }
 
@@ -991,14 +1000,14 @@ body.ld-drawer-page-open #ld-drawer-root {
     width: 100vw;
   }
 
-  #ld-drawer-root .ld-image-preview {
+  #ld-image-preview-root .ld-image-preview {
     padding: max(18px, env(safe-area-inset-top, 0px) + 8px)
       12px
       max(12px, env(safe-area-inset-bottom, 0px) + 8px);
     align-items: stretch;
   }
 
-  #ld-drawer-root .ld-image-preview-close {
+  #ld-image-preview-root .ld-image-preview-close {
     top: max(10px, env(safe-area-inset-top, 0px) + 2px);
     right: 12px;
     padding: 8px 12px;
@@ -1006,13 +1015,13 @@ body.ld-drawer-page-open #ld-drawer-root {
     backdrop-filter: blur(10px);
   }
 
-  #ld-drawer-root .ld-image-preview-stage {
+  #ld-image-preview-root .ld-image-preview-stage {
     align-items: center;
     padding-top: 40px;
     padding-bottom: 6px;
   }
 
-  #ld-drawer-root .ld-image-preview-image {
+  #ld-image-preview-root .ld-image-preview-image {
     max-width: 100%;
     max-height: calc(100dvh - 88px);
     border-radius: 12px;
@@ -1068,9 +1077,9 @@ body.ld-drawer-page-open #ld-drawer-root {
 }
 
 @media (prefers-reduced-motion: reduce) {
-  #ld-drawer-root .ld-image-preview,
-  #ld-drawer-root .ld-image-preview-close,
-  #ld-drawer-root .ld-image-preview-image {
+  #ld-image-preview-root .ld-image-preview,
+  #ld-image-preview-root .ld-image-preview-close,
+  #ld-image-preview-root .ld-image-preview-image {
     animation: none;
     transition: none;
   }
diff --git a/src/content.js b/src/content.js
index 2b9384e..4691310 100644
--- a/src/content.js
+++ b/src/content.js
@@ -1,5 +1,6 @@
 (function () {
   const ROOT_ID = "ld-drawer-root";
+  const IMAGE_PREVIEW_ROOT_ID = "ld-image-preview-root";
   const PAGE_OPEN_CLASS = "ld-drawer-page-open";
   const PAGE_IFRAME_OPEN_CLASS = "ld-drawer-page-iframe-open";
   const ACTIVE_LINK_CLASS = "ld-drawer-topic-link-active";
@@ -102,6 +103,7 @@
     replySubmitButton: null,
     replyCancelButton: null,
     replyStatus: null,
+    imagePreviewRoot: null,
     imagePreview: null,
     imagePreviewImage: null,
     imagePreviewCloseButton: null,
@@ -296,16 +298,22 @@
             <button class="ld-reply-action ld-reply-action-primary" type="button" data-action="submit">发送回复</button>
           </div>
         </div>
-        <div class="ld-image-preview" hidden aria-hidden="true">
-          <button class="ld-image-preview-close" type="button" aria-label="关闭图片预览">关闭</button>
-          <div class="ld-image-preview-stage">
-            <img class="ld-image-preview-image" alt="图片预览" />
-          </div>
+      </div>
+    `;
+
+    const imagePreviewRoot = document.createElement("div");
+    imagePreviewRoot.id = IMAGE_PREVIEW_ROOT_ID;
+    imagePreviewRoot.setAttribute("aria-hidden", "true");
+    imagePreviewRoot.innerHTML = `
+      <div class="ld-image-preview" hidden aria-hidden="true">
+        <button class="ld-image-preview-close" type="button" aria-label="关闭图片预览">关闭</button>
+        <div class="ld-image-preview-stage">
+          <img class="ld-image-preview-image" alt="图片预览" />
         </div>
       </div>
     `;
 
-    document.body.appendChild(root);
+    document.body.append(root, imagePreviewRoot);
 
     state.root = root;
     state.header = root.querySelector(".ld-drawer-header");
@@ -321,9 +329,10 @@
     state.replySubmitButton = root.querySelector('[data-action="submit"]');
     state.replyCancelButton = root.querySelector('[data-action="cancel"]');
     state.replyStatus = root.querySelector(".ld-reply-status");
-    state.imagePreview = root.querySelector(".ld-image-preview");
-    state.imagePreviewImage = root.querySelector(".ld-image-preview-image");
-    state.imagePreviewCloseButton = root.querySelector(".ld-image-preview-close");
+    state.imagePreviewRoot = imagePreviewRoot;
+    state.imagePreview = imagePreviewRoot.querySelector(".ld-image-preview");
+    state.imagePreviewImage = imagePreviewRoot.querySelector(".ld-image-preview-image");
+    state.imagePreviewCloseButton = imagePreviewRoot.querySelector(".ld-image-preview-close");
     state.openInTab = root.querySelector(".ld-drawer-link");
     state.settingsPanel = root.querySelector(".ld-drawer-settings");
     state.settingsCard = root.querySelector(".ld-drawer-settings-card");
@@ -352,6 +361,8 @@
     state.replyTextarea.addEventListener("paste", handleReplyTextareaPaste);
     root.addEventListener("click", handleDrawerRootClick);
     root.addEventListener("wheel", handleDrawerRootWheel, { passive: false });
+    imagePreviewRoot.addEventListener("click", handleImagePreviewClick);
+    imagePreviewRoot.addEventListener("wheel", handleImagePreviewWheel, { passive: false });
     state.drawerBody.addEventListener("scroll", handleDrawerBodyScroll, { passive: true });
     state.settingsPanel.addEventListener("click", handleSettingsPanelClick);
     state.settingsPanel.addEventListener("input", handleSettingsInput);
@@ -393,6 +404,10 @@
       return;
     }
 
+    if (!state.imagePreview?.hidden && target.closest(`#${IMAGE_PREVIEW_ROOT_ID}`)) {
+      return;
+    }
+
     if (!state.settingsPanel?.hidden && !target.closest(".ld-drawer-settings-card") && !target.closest(".ld-drawer-settings-toggle")) {
       setSettingsPanelOpen(false);
     }
@@ -2082,14 +2097,6 @@
       return;
     }
 
-    if (!state.imagePreview?.hidden) {
-      if (target.closest(".ld-image-preview-close") || !target.closest(".ld-image-preview-image")) {
-        event.preventDefault();
-        closeImagePreview();
-      }
-      return;
-    }
-
     const image = target.closest(".ld-post-body img");
     if (!(image instanceof HTMLImageElement)) {
       return;
@@ -2100,8 +2107,23 @@
     openImagePreview(image);
   }
 
+  function handleImagePreviewClick(event) {
+    if (state.imagePreview?.hidden) {
+      return;
+    }
+
+    const target = event.target;
+    if (!(target instanceof Element) || !target.closest(".ld-image-preview")) {
+      return;
+    }
+
+    event.preventDefault();
+    event.stopPropagation();
+    closeImagePreview();
+  }
+
   function openImagePreview(image) {
-    if (!state.imagePreview || !state.imagePreviewImage) {
+    if (!state.imagePreviewRoot || !state.imagePreview || !state.imagePreviewImage) {
       return;
     }
 
@@ -2114,6 +2136,7 @@
     state.imagePreviewImage.src = previewSrc;
     state.imagePreviewImage.alt = image.alt || "图片预览";
     state.imagePreviewImage.classList.remove("is-ready");
+    state.imagePreviewRoot.setAttribute("aria-hidden", "false");
     state.imagePreview.hidden = false;
     state.imagePreview.setAttribute("aria-hidden", "false");
     if (state.imagePreviewImage.complete) {
@@ -2126,10 +2149,11 @@
   }
 
   function closeImagePreview() {
-    if (!state.imagePreview || !state.imagePreviewImage) {
+    if (!state.imagePreviewRoot || !state.imagePreview || !state.imagePreviewImage) {
       return;
     }
 
+    state.imagePreviewRoot.setAttribute("aria-hidden", "true");
     state.imagePreview.hidden = true;
     state.imagePreview.setAttribute("aria-hidden", "true");
     resetImagePreviewScale();
@@ -2142,26 +2166,38 @@
     state.imagePreviewImage?.classList.add("is-ready");
   }
 
-  function handleDrawerRootWheel(event) {
+  function handleImagePreviewWheel(event) {
+    if (state.imagePreview?.hidden) {
+      return;
+    }
+
     const target = event.target;
     if (!(target instanceof Element)) {
       return;
     }
 
-    if (!state.imagePreview?.hidden && target.closest(".ld-image-preview-stage")) {
-      event.preventDefault();
+    event.preventDefault();
 
-      const nextScale = clampImagePreviewScale(
-        state.imagePreviewScale + (event.deltaY < 0 ? IMAGE_PREVIEW_SCALE_STEP : -IMAGE_PREVIEW_SCALE_STEP)
-      );
+    if (!target.closest(".ld-image-preview-stage")) {
+      return;
+    }
 
-      if (nextScale === state.imagePreviewScale) {
-        return;
-      }
+    const nextScale = clampImagePreviewScale(
+      state.imagePreviewScale + (event.deltaY < 0 ? IMAGE_PREVIEW_SCALE_STEP : -IMAGE_PREVIEW_SCALE_STEP)
+    );
+
+    if (nextScale === state.imagePreviewScale) {
+      return;
+    }
 
-      updateImagePreviewTransformOrigin(event.clientX, event.clientY);
-      state.imagePreviewScale = nextScale;
-      applyImagePreviewScale();
+    updateImagePreviewTransformOrigin(event.clientX, event.clientY);
+    state.imagePreviewScale = nextScale;
+    applyImagePreviewScale();
+  }
+
+  function handleDrawerRootWheel(event) {
+    const target = event.target;
+    if (!(target instanceof Element)) {
       return;
     }