diff --git a/desktop-app/resources/index.html b/desktop-app/resources/index.html
index 32be8f98..7108af59 100644
--- a/desktop-app/resources/index.html
+++ b/desktop-app/resources/index.html
@@ -239,8 +239,8 @@ <h5>Menu</h5>
         </header>
 
         <!-- Tab Bar -->
-        <div class="tab-bar" id="tab-bar" role="tablist" aria-label="Document tabs">
-          <div class="tab-list" id="tab-list"></div>
+        <div class="tab-bar" id="tab-bar">
+          <div class="tab-list" id="tab-list" role="tablist" aria-label="Document tabs"></div>
           <button class="tab-reset-btn" id="tab-reset-btn" title="Reset all files" aria-label="Reset all files">
             <i class="bi bi-arrow-counterclockwise"></i> Reset
           </button>
@@ -778,10 +778,10 @@ <h3 class="modal-section-title">Open-source credits</h3>
             </div>
         </div>
 
-        <div class="content-container">
+        <main class="content-container">
             <div class="editor-pane is-loading">
                 <div id="line-numbers" class="line-numbers" aria-hidden="true"></div>
-                <div id="editor-highlight-layer" class="editor-highlight-layer" aria-hidden="true"></div>
+                <div id="editor-highlight-layer" class="editor-highlight-layer" aria-hidden="true" tabindex="-1"></div>
                 <div class="editor-skeleton" id="editor-skeleton" aria-hidden="true">
                     <div class="skeleton-placeholder skeleton-title"></div>
                     <div class="skeleton-placeholder skeleton-line skeleton-w90"></div>
@@ -818,7 +818,7 @@ <h3 class="modal-section-title">Open-source credits</h3>
                     </div>
                 </div>
             </div>
-        </div>
+        </main>
     </div>
 
     <!-- Mermaid Zoom Modal -->
diff --git a/desktop-app/resources/js/script.js b/desktop-app/resources/js/script.js
index 9fd28eaf..42c35ff9 100644
--- a/desktop-app/resources/js/script.js
+++ b/desktop-app/resources/js/script.js
@@ -1518,6 +1518,14 @@ document.addEventListener("DOMContentLoaded", function () {
       enhanceGitHubAlerts(markdownPreview);
 
       processEmojis(markdownPreview);
+
+      // Add accessible dynamic labels to task list checkboxes matching their parent text
+      markdownPreview.querySelectorAll('input[type="checkbox"]').forEach(function(input) {
+        if (!input.hasAttribute('aria-label')) {
+          const parentText = input.parentElement ? input.parentElement.textContent.trim() : '';
+          input.setAttribute('aria-label', parentText || 'Task item');
+        }
+      });
       
       // PERF-002: Lazy-load mermaid only when diagrams are present
       try {
@@ -1559,7 +1567,11 @@ document.addEventListener("DOMContentLoaded", function () {
       if (hasMath) {
         if (window.MathJax) {
           try {
-            MathJax.typesetPromise([markdownPreview]).catch((err) => {
+            MathJax.typesetPromise([markdownPreview]).then(function() {
+              markdownPreview.querySelectorAll('mjx-container[tabindex="0"]').forEach(function(mjx) {
+                mjx.removeAttribute('tabindex');
+              });
+            }).catch(function(err) {
               console.warn('MathJax typesetting failed:', err);
             });
           } catch (e) {
@@ -1578,7 +1590,11 @@ document.addEventListener("DOMContentLoaded", function () {
           };
           loadScript(CDN.mathjax).then(function() {
             try {
-              MathJax.typesetPromise([markdownPreview]).catch(function(err) {
+              MathJax.typesetPromise([markdownPreview]).then(function() {
+                markdownPreview.querySelectorAll('mjx-container[tabindex="0"]').forEach(function(mjx) {
+                  mjx.removeAttribute('tabindex');
+                });
+              }).catch(function(err) {
                 console.warn('MathJax typesetting failed:', err);
               });
             } catch (e) {
diff --git a/desktop-app/resources/styles.css b/desktop-app/resources/styles.css
index 56be2004..984a61f3 100644
--- a/desktop-app/resources/styles.css
+++ b/desktop-app/resources/styles.css
@@ -758,7 +758,7 @@ a:focus {
   --color-prettylights-syntax-entity: #6f42c1;
   --color-prettylights-syntax-storage-modifier-import: #24292e;
   --color-prettylights-syntax-entity-tag: #22863a;
-  --color-prettylights-syntax-keyword: #d73a49;
+  --color-prettylights-syntax-keyword: #cf222e;
   --color-prettylights-syntax-string: #032f62;
   --color-prettylights-syntax-variable: #e36209;
   --color-prettylights-syntax-brackethighlighter-unmatched: #b31d28;
@@ -1732,7 +1732,7 @@ a:focus {
   display: flex;
   align-items: center;
   gap: 6px;
-  height: 27px;
+  height: 32px;
   padding: 0 8px 0 10px;
   min-width: 100px;
   max-width: 180px;
@@ -1874,8 +1874,8 @@ a:focus {
   display: flex;
   align-items: center;
   justify-content: center;
-  width: 18px;
-  height: 18px;
+  width: 22px;
+  height: 22px;
   border-radius: 3px;
   background: none;
   border: none;
diff --git a/index.html b/index.html
index f6d01b08..8407b3bb 100644
--- a/index.html
+++ b/index.html
@@ -298,8 +298,8 @@ <h5>Menu</h5>
         </header>
 
         <!-- Tab Bar -->
-        <div class="tab-bar" id="tab-bar" role="tablist" aria-label="Document tabs">
-          <div class="tab-list" id="tab-list"></div>
+        <div class="tab-bar" id="tab-bar">
+          <div class="tab-list" id="tab-list" role="tablist" aria-label="Document tabs"></div>
           <button class="tab-reset-btn" id="tab-reset-btn" title="Reset all files" aria-label="Reset all files">
             <i class="bi bi-arrow-counterclockwise"></i> Reset
           </button>
@@ -837,10 +837,10 @@ <h3 class="modal-section-title">Open-source credits</h3>
             </div>
         </div>
 
-        <div class="content-container">
+        <main class="content-container">
             <div class="editor-pane is-loading">
                 <div id="line-numbers" class="line-numbers" aria-hidden="true"></div>
-                <div id="editor-highlight-layer" class="editor-highlight-layer" aria-hidden="true"></div>
+                <div id="editor-highlight-layer" class="editor-highlight-layer" aria-hidden="true" tabindex="-1"></div>
                 <div class="editor-skeleton" id="editor-skeleton" aria-hidden="true">
                     <div class="skeleton-placeholder skeleton-title"></div>
                     <div class="skeleton-placeholder skeleton-line skeleton-w90"></div>
@@ -877,7 +877,7 @@ <h3 class="modal-section-title">Open-source credits</h3>
                     </div>
                 </div>
             </div>
-        </div>
+        </main>
     </div>
 
     <!-- Mermaid Zoom Modal -->
diff --git a/script.js b/script.js
index 9fd28eaf..42c35ff9 100644
--- a/script.js
+++ b/script.js
@@ -1518,6 +1518,14 @@ document.addEventListener("DOMContentLoaded", function () {
       enhanceGitHubAlerts(markdownPreview);
 
       processEmojis(markdownPreview);
+
+      // Add accessible dynamic labels to task list checkboxes matching their parent text
+      markdownPreview.querySelectorAll('input[type="checkbox"]').forEach(function(input) {
+        if (!input.hasAttribute('aria-label')) {
+          const parentText = input.parentElement ? input.parentElement.textContent.trim() : '';
+          input.setAttribute('aria-label', parentText || 'Task item');
+        }
+      });
       
       // PERF-002: Lazy-load mermaid only when diagrams are present
       try {
@@ -1559,7 +1567,11 @@ document.addEventListener("DOMContentLoaded", function () {
       if (hasMath) {
         if (window.MathJax) {
           try {
-            MathJax.typesetPromise([markdownPreview]).catch((err) => {
+            MathJax.typesetPromise([markdownPreview]).then(function() {
+              markdownPreview.querySelectorAll('mjx-container[tabindex="0"]').forEach(function(mjx) {
+                mjx.removeAttribute('tabindex');
+              });
+            }).catch(function(err) {
               console.warn('MathJax typesetting failed:', err);
             });
           } catch (e) {
@@ -1578,7 +1590,11 @@ document.addEventListener("DOMContentLoaded", function () {
           };
           loadScript(CDN.mathjax).then(function() {
             try {
-              MathJax.typesetPromise([markdownPreview]).catch(function(err) {
+              MathJax.typesetPromise([markdownPreview]).then(function() {
+                markdownPreview.querySelectorAll('mjx-container[tabindex="0"]').forEach(function(mjx) {
+                  mjx.removeAttribute('tabindex');
+                });
+              }).catch(function(err) {
                 console.warn('MathJax typesetting failed:', err);
               });
             } catch (e) {
diff --git a/styles.css b/styles.css
index 56be2004..984a61f3 100644
--- a/styles.css
+++ b/styles.css
@@ -758,7 +758,7 @@ a:focus {
   --color-prettylights-syntax-entity: #6f42c1;
   --color-prettylights-syntax-storage-modifier-import: #24292e;
   --color-prettylights-syntax-entity-tag: #22863a;
-  --color-prettylights-syntax-keyword: #d73a49;
+  --color-prettylights-syntax-keyword: #cf222e;
   --color-prettylights-syntax-string: #032f62;
   --color-prettylights-syntax-variable: #e36209;
   --color-prettylights-syntax-brackethighlighter-unmatched: #b31d28;
@@ -1732,7 +1732,7 @@ a:focus {
   display: flex;
   align-items: center;
   gap: 6px;
-  height: 27px;
+  height: 32px;
   padding: 0 8px 0 10px;
   min-width: 100px;
   max-width: 180px;
@@ -1874,8 +1874,8 @@ a:focus {
   display: flex;
   align-items: center;
   justify-content: center;
-  width: 18px;
-  height: 18px;
+  width: 22px;
+  height: 22px;
   border-radius: 3px;
   background: none;
   border: none;