diff --git a/src/renderer/components/chat/viewers/MarkdownViewer.tsx b/src/renderer/components/chat/viewers/MarkdownViewer.tsx
index 703c07d9..00c5da3f 100644
--- a/src/renderer/components/chat/viewers/MarkdownViewer.tsx
+++ b/src/renderer/components/chat/viewers/MarkdownViewer.tsx
@@ -39,6 +39,7 @@ import {
   highlightSearchInChildren,
   type SearchContext,
 } from '../searchHighlightUtils';
+import { highlightLine } from '../viewers/syntaxHighlighter';
 
 import { FileLink, isRelativeUrl } from './FileLink';
 import { MermaidDiagram } from './MermaidDiagram';
@@ -535,12 +536,21 @@ function createViewerMarkdownComponents(
       const isBlock = (hasLanguage ?? false) || isMultiLine;
 
       if (isBlock) {
+        const lang = codeClassName?.replace('language-', '') ?? '';
+        const raw = typeof children === 'string' ? children : '';
+        const text = raw.replace(/\n$/, '');
+        const lines = text.split('\n');
         return (
           <code
             className={`font-mono text-xs ${codeClassName ?? ''}`.trim()}
             style={{ color: COLOR_TEXT }}
           >
-            {hl(children)}
+            {lines.map((line, i) => (
+              <React.Fragment key={i}>
+                {hl(highlightLine(line, lang))}
+                {i < lines.length - 1 ? '\n' : null}
+              </React.Fragment>
+            ))}
           </code>
         );
       }
diff --git a/src/renderer/components/chat/viewers/syntaxHighlighter.ts b/src/renderer/components/chat/viewers/syntaxHighlighter.ts
index 2271d08b..e6e2f6b3 100644
--- a/src/renderer/components/chat/viewers/syntaxHighlighter.ts
+++ b/src/renderer/components/chat/viewers/syntaxHighlighter.ts
@@ -208,6 +208,200 @@ const KEYWORDS: Record<string, Set<string>> = {
     'true',
     'false',
   ]),
+  r: new Set([
+    'if',
+    'else',
+    'for',
+    'while',
+    'repeat',
+    'function',
+    'return',
+    'next',
+    'break',
+    'in',
+    'library',
+    'require',
+    'source',
+    'TRUE',
+    'FALSE',
+    'NULL',
+    'NA',
+    'Inf',
+    'NaN',
+    'NA_integer_',
+    'NA_real_',
+    'NA_complex_',
+    'NA_character_',
+  ]),
+  ruby: new Set([
+    'def',
+    'class',
+    'module',
+    'end',
+    'do',
+    'if',
+    'elsif',
+    'else',
+    'unless',
+    'while',
+    'until',
+    'for',
+    'in',
+    'begin',
+    'rescue',
+    'ensure',
+    'raise',
+    'return',
+    'yield',
+    'block_given?',
+    'require',
+    'require_relative',
+    'include',
+    'extend',
+    'attr_accessor',
+    'attr_reader',
+    'attr_writer',
+    'self',
+    'super',
+    'nil',
+    'true',
+    'false',
+    'and',
+    'or',
+    'not',
+    'then',
+    'when',
+    'case',
+    'lambda',
+    'proc',
+    'puts',
+    'print',
+  ]),
+  php: new Set([
+    'function',
+    'class',
+    'interface',
+    'trait',
+    'extends',
+    'implements',
+    'namespace',
+    'use',
+    'public',
+    'private',
+    'protected',
+    'static',
+    'abstract',
+    'final',
+    'const',
+    'var',
+    'new',
+    'return',
+    'if',
+    'elseif',
+    'else',
+    'for',
+    'foreach',
+    'while',
+    'do',
+    'switch',
+    'case',
+    'break',
+    'continue',
+    'default',
+    'try',
+    'catch',
+    'finally',
+    'throw',
+    'as',
+    'echo',
+    'print',
+    'require',
+    'require_once',
+    'include',
+    'include_once',
+    'true',
+    'false',
+    'null',
+    'array',
+    'isset',
+    'unset',
+    'empty',
+    'self',
+    'this',
+  ]),
+  sql: new Set([
+    'SELECT',
+    'FROM',
+    'WHERE',
+    'INSERT',
+    'INTO',
+    'UPDATE',
+    'SET',
+    'DELETE',
+    'CREATE',
+    'ALTER',
+    'DROP',
+    'TABLE',
+    'INDEX',
+    'VIEW',
+    'DATABASE',
+    'JOIN',
+    'INNER',
+    'LEFT',
+    'RIGHT',
+    'OUTER',
+    'FULL',
+    'CROSS',
+    'ON',
+    'AND',
+    'OR',
+    'NOT',
+    'IN',
+    'EXISTS',
+    'BETWEEN',
+    'LIKE',
+    'IS',
+    'NULL',
+    'AS',
+    'ORDER',
+    'BY',
+    'GROUP',
+    'HAVING',
+    'LIMIT',
+    'OFFSET',
+    'UNION',
+    'ALL',
+    'DISTINCT',
+    'COUNT',
+    'SUM',
+    'AVG',
+    'MIN',
+    'MAX',
+    'CASE',
+    'WHEN',
+    'THEN',
+    'ELSE',
+    'END',
+    'BEGIN',
+    'COMMIT',
+    'ROLLBACK',
+    'TRANSACTION',
+    'PRIMARY',
+    'KEY',
+    'FOREIGN',
+    'REFERENCES',
+    'CONSTRAINT',
+    'DEFAULT',
+    'VALUES',
+    'TRUE',
+    'FALSE',
+    'INTEGER',
+    'VARCHAR',
+    'TEXT',
+    'BOOLEAN',
+    'DATE',
+    'TIMESTAMP',
+  ]),
 };
 
 // Extend tsx/jsx to use typescript/javascript keywords
@@ -296,8 +490,23 @@ export function highlightLine(line: string, language: string): React.ReactNode[]
       break;
     }
 
-    // Check for comment (# style for Python/Shell)
-    if ((language === 'python' || language === 'bash') && remaining.startsWith('#')) {
+    // Check for comment (# style for Python/Shell/R/Ruby/PHP)
+    if (
+      (language === 'python' || language === 'bash' || language === 'r' || language === 'ruby' || language === 'php') &&
+      remaining.startsWith('#')
+    ) {
+      segments.push(
+        React.createElement(
+          'span',
+          { key: currentPos, style: { color: 'var(--syntax-comment)', fontStyle: 'italic' } },
+          remaining
+        )
+      );
+      break;
+    }
+
+    // Check for comment (-- style for SQL)
+    if (language === 'sql' && remaining.startsWith('--')) {
       segments.push(
         React.createElement(
           'span',
@@ -326,7 +535,8 @@ export function highlightLine(line: string, language: string): React.ReactNode[]
     const wordMatch = /^([a-zA-Z_$][a-zA-Z0-9_$]*)/.exec(remaining);
     if (wordMatch) {
       const word = wordMatch[1];
-      if (keywords.has(word)) {
+      // SQL keywords are case-insensitive
+      if (keywords.has(word) || (language === 'sql' && keywords.has(word.toUpperCase()))) {
         segments.push(
           React.createElement(
             'span',