diff --git a/server/src/utils/webview_utils.cpp b/server/src/utils/webview_utils.cpp
index 3cc02db4..8982645c 100644
--- a/server/src/utils/webview_utils.cpp
+++ b/server/src/utils/webview_utils.cpp
@@ -61,8 +61,17 @@ void GetContainerSizeCand(ComPtr<ICoreWebView2> webview, std::function<void(std:
     }
     std::wstring script = LR"(
         (function() {
-            var rect = document.getElementById("measureContainerParent").getBoundingClientRect();
-            return JSON.stringify({width: rect.width, height: rect.height});
+            var el = document.getElementById("measureContainerParent");
+            var box = document.getElementById("measureContainer");
+            if (!el) {
+                return JSON.stringify({width: 0, height: 0});
+            }
+            var rect = el.getBoundingClientRect();
+            // Prefer intrinsic content width so horizontal nowrap layouts are not
+            // under-reported when the WebView viewport is still narrow.
+            var width = Math.max(rect.width, box ? box.scrollWidth : 0, el.scrollWidth || 0);
+            var height = Math.max(rect.height, box ? box.scrollHeight : 0, el.scrollHeight || 0);
+            return JSON.stringify({width: width, height: height});
         })();
     )";
     const HRESULT submitHr = webview->ExecuteScript( //
diff --git a/server/src/webview2/windows_webview2.cpp b/server/src/webview2/windows_webview2.cpp
index 351aac5a..03943365 100644
--- a/server/src/webview2/windows_webview2.cpp
+++ b/server/src/webview2/windows_webview2.cpp
@@ -366,33 +366,81 @@ inline std::wstring GetAppdataPath()
 
 void UpdateHtmlContentWithJavaScript(ComPtr<ICoreWebView2> webview, const std::wstring &newContent)
 {
-    if (webview != nullptr)
+    UpdateHtmlContentWithJavaScript(webview, newContent, nullptr);
+}
+
+void UpdateHtmlContentWithJavaScript(ComPtr<ICoreWebView2> webview, const std::wstring &newContent,
+                                     std::function<void()> onComplete)
+{
+    if (!webview)
     {
-        std::wstring script;
-        script.reserve(newContent.length() + 512);
-
-        script.append(L"document.getElementById('realContainer').innerHTML = `");
-        script.append(newContent);
-        script.append(L"`;\n");
-        script.append(L"window.ClearState();\n");
-        script.append(L"var el = document.getElementById('realContainerParent');\n");
-        script.append(L"if (el) {\n");
-        script.append(L"  el.style.marginTop = \"");
-        script.append(std::to_wstring(Global::MarginTop));
-        script.append(L"px\";\n");
-        script.append(L"}\n");
-        script.append(L"if (window.SetCandidateSelection) { window.SetCandidateSelection(");
-        script.append(std::to_wstring(Global::candidate_ui.selected_index_in_page));
-        script.append(L"); }\n");
-        script.append(L"if (window.SetCandidatePreeditVisible) { window.SetCandidatePreeditVisible(");
-        script.append(GetConfiguredCandidateWindowPreeditStyle() == "empty" ? L"false" : L"true");
-        script.append(L"); }\n");
-        script.append(L"if (window.SetPreeditCaret) { window.SetPreeditCaret(); }\n");
-
-        // OutputDebugString(fmt::format(L"[msime]: UpdateHtmlContentWithJavaScript: {}", script).c_str());
-
-        webview->ExecuteScript(script.c_str(), nullptr);
+        if (onComplete)
+        {
+            onComplete();
+        }
+        return;
     }
+
+    std::wstring script;
+    script.reserve(newContent.length() + 512);
+
+    script.append(L"document.getElementById('realContainer').innerHTML = `");
+    script.append(newContent);
+    script.append(L"`;\n");
+    script.append(L"window.ClearState();\n");
+    script.append(L"var el = document.getElementById('realContainerParent');\n");
+    script.append(L"if (el) {\n");
+    script.append(L"  el.style.marginTop = \"");
+    script.append(std::to_wstring(Global::MarginTop));
+    script.append(L"px\";\n");
+    script.append(L"}\n");
+    script.append(L"if (window.SetCandidateSelection) { window.SetCandidateSelection(");
+    script.append(std::to_wstring(Global::candidate_ui.selected_index_in_page));
+    script.append(L"); }\n");
+    script.append(L"if (window.SetCandidatePreeditVisible) { window.SetCandidatePreeditVisible(");
+    script.append(GetConfiguredCandidateWindowPreeditStyle() == "empty" ? L"false" : L"true");
+    script.append(L"); }\n");
+    script.append(L"if (window.SetPreeditCaret) { window.SetPreeditCaret(); }\n");
+
+    if (!onComplete)
+    {
+        webview->ExecuteScript(script.c_str(), nullptr);
+        return;
+    }
+
+    webview->ExecuteScript(
+        script.c_str(),
+        Callback<ICoreWebView2ExecuteScriptCompletedHandler>(
+            [onComplete](HRESULT, LPCWSTR) -> HRESULT {
+                onComplete();
+                return S_OK;
+            })
+            .Get());
+}
+
+void PrepareCandidateWebViewBoundsForMeasure(HWND hwnd)
+{
+    if (!webviewControllerCandWnd || !hwnd)
+    {
+        return;
+    }
+    RECT bounds{};
+    GetClientRect(hwnd, &bounds);
+    bounds.right += candidateBoundRightExtra;
+    bounds.bottom += candidateBoundBottomExtra;
+    webviewControllerCandWnd->put_Bounds(bounds);
+}
+
+void SyncCandidateWebViewBoundsToHost(HWND hwnd)
+{
+    if (!webviewControllerCandWnd || !hwnd)
+    {
+        return;
+    }
+    RECT bounds{};
+    GetClientRect(hwnd, &bounds);
+    webviewControllerCandWnd->put_Bounds(bounds);
+    webviewControllerCandWnd->NotifyParentWindowPositionChanged();
 }
 
 int PrepareHtmlForWnds()
@@ -555,6 +603,11 @@ window.mouseBlockTimeout = setTimeout(() => {
 }
 
 void InflateCandWnd(std::wstring &str)
+{
+    InflateCandWnd(str, nullptr);
+}
+
+void InflateCandWnd(std::wstring &str, std::function<void()> onComplete)
 {
     std::wstringstream wss(str);
     std::wstring token;
@@ -565,7 +618,7 @@ void InflateCandWnd(std::wstring &str)
         words.push_back(token);
     }
 
-    int size = words.size();
+    int size = static_cast<int>(words.size());
 
     while (words.size() < 9)
     {
@@ -588,11 +641,10 @@ void InflateCandWnd(std::wstring &str)
     if (size < 9)
     {
         size_t pos = result.find(fmt::format(L"<!--{}Anchor-->", size));
-        // result = result.substr(0, pos) + L"</div>";
         result = result.substr(0, pos);
     }
 
-    UpdateHtmlContentWithJavaScript(webviewCandWnd, result);
+    UpdateHtmlContentWithJavaScript(webviewCandWnd, result, std::move(onComplete));
 }
 
 void InflateMeasureDivCandWnd(std::wstring &str)
diff --git a/server/src/webview2/windows_webview2.h b/server/src/webview2/windows_webview2.h
index d6125e62..595cdae4 100644
--- a/server/src/webview2/windows_webview2.h
+++ b/server/src/webview2/windows_webview2.h
@@ -5,6 +5,7 @@
 #include "fmt/xchar.h"
 #include <boost/locale.hpp>
 #include <fstream>
+#include <functional>
 #include <sstream>
 #include <string>
 #include <vector>
@@ -28,6 +29,11 @@ void UpdateHtmlContentWithJavaScript( //
     ComPtr<ICoreWebView2> webview,    //
     const std::wstring &newContent    //
 );                                    //
+void UpdateHtmlContentWithJavaScript(                       //
+    ComPtr<ICoreWebView2> webview,                          //
+    const std::wstring &newContent,                         //
+    std::function<void()> onComplete                        //
+);                                                          //
 
 //
 // 候选窗口 webview
@@ -48,10 +54,15 @@ bool ApplyConfiguredUiThemes();
 void ResetContainerHoverCandWnd(ComPtr<ICoreWebView2> webview);
 void DisableMouseForAWhileWhenShownCandWnd(ComPtr<ICoreWebView2> webview);
 void InflateCandWnd(std::wstring &str);
+void InflateCandWnd(std::wstring &str, std::function<void()> onComplete);
 void InflateMeasureDivCandWnd(std::wstring &str);
 void InitSmallWindowWebviews(HWND candHwnd, HWND menuHwnd, HWND ftbHwnd);
 void ShutdownWebviews();
 void UpdateSmallWindowWebviewVisibility(HWND hwnd, bool visible);
+// Expand WebView bounds beyond the host client so horizontal measure/layout
+// is not constrained by a still-narrow HWND.
+void PrepareCandidateWebViewBoundsForMeasure(HWND hwnd);
+void SyncCandidateWebViewBoundsToHost(HWND hwnd);
 
 // uiAccess + HWND WebView2: request TOPMOST on first real show. If WebViews are
 // not ready yet, the request is queued and applied after all small-window
diff --git a/server/src/window/ime_windows.cpp b/server/src/window/ime_windows.cpp
index 3a2af42b..86f187ae 100644
--- a/server/src/window/ime_windows.cpp
+++ b/server/src/window/ime_windows.cpp
@@ -1481,6 +1481,8 @@ int FineTuneWindow(HWND hwnd)
         LogSmallWindowReadyGate(L"fine-tune-no-webview");
         return 0;
     }
+    // Give horizontal measure an unconstrained viewport before reading DOM size.
+    PrepareCandidateWebViewBoundsForMeasure(hwnd);
     std::shared_ptr<std::pair<int, int>> properPos = std::make_shared<std::pair<int, int>>();
     GetContainerSizeCand(webviewCandWnd, [flag,      //
                                           scale,     //
@@ -1512,7 +1514,6 @@ int FineTuneWindow(HWND hwnd)
             OutputDebugStringW(L"[msime-webview] candidate fine-tune abandoned: composition and candidates empty\n");
             return;
         }
-        InflateCandWnd(str);
 
         int newWidth = 0;
         int newHeight = 0;
@@ -1532,6 +1533,10 @@ int FineTuneWindow(HWND hwnd)
         {
             return;
         }
+
+        // Resize host + WebView first, then paint visible content. Inflating
+        // into a still-narrow viewport lets horizontal candidates wrap and
+        // flash a taller intermediate frame before the final single-line layout.
         const BOOL positioned = SetWindowPos( //
             hwnd,              //
             nullptr,           //
@@ -1541,20 +1546,27 @@ int FineTuneWindow(HWND hwnd)
             newHeight,         //
             newFlag            //
         );
-        SetHostWindowCloaked(hwnd, false);
-        UpdateSmallWindowWebviewVisibility(hwnd, true);
-        SyncHostWebViewBounds(::webviewControllerCandWnd.Get(), hwnd);
-        RECT actualRect{};
-        GetWindowRect(hwnd, &actualRect);
-        OutputDebugStringW(fmt::format(
-            L"[msime-webview] candidate window positioned: requested_pos=({},{}), requested_size=({},{}), "
-            L"flags=0x{:X}, success={}, GetLastError={}, actual_rect=[{},{},{},{}], visible={}, "
-            L"topmost_applied={}, measure=({:.1f},{:.1f})\n",
-            properPos->first, properPos->second, newWidth, newHeight, newFlag, positioned != FALSE,
-            positioned ? 0 : GetLastError(), actualRect.left, actualRect.top, actualRect.right, actualRect.bottom,
-            IsWindowVisible(hwnd) != FALSE, AreSmallWindowsTopmostApplied(), containerSize.first,
-            containerSize.second)
-                               .c_str());
+        SyncCandidateWebViewBoundsToHost(hwnd);
+
+        InflateCandWnd(str, [hwnd, positioned, newWidth, newHeight, newFlag, properPos, containerSize]() {
+            if (!::is_global_wnd_cand_shown)
+            {
+                return;
+            }
+            SetHostWindowCloaked(hwnd, false);
+            UpdateSmallWindowWebviewVisibility(hwnd, true);
+            RECT actualRect{};
+            GetWindowRect(hwnd, &actualRect);
+            OutputDebugStringW(fmt::format(
+                L"[msime-webview] candidate window positioned: requested_pos=({},{}), requested_size=({},{}), "
+                L"flags=0x{:X}, success={}, GetLastError={}, actual_rect=[{},{},{},{}], visible={}, "
+                L"topmost_applied={}, measure=({:.1f},{:.1f})\n",
+                properPos->first, properPos->second, newWidth, newHeight, newFlag, positioned != FALSE,
+                positioned ? 0 : GetLastError(), actualRect.left, actualRect.top, actualRect.right, actualRect.bottom,
+                IsWindowVisible(hwnd) != FALSE, AreSmallWindowsTopmostApplied(), containerSize.first,
+                containerSize.second)
+                                   .c_str());
+        });
     });
     return 0;
 }