diff --git a/app/create-session.tsx b/app/create-session.tsx
index 87cf974..a21c5db 100644
--- a/app/create-session.tsx
+++ b/app/create-session.tsx
@@ -178,6 +178,11 @@ export default function CreateSessionScreen() {
       return;
     }
 
+    if (prompt.length > 50000) {
+      Alert.alert(t('error'), t('promptTooLong'));
+      return;
+    }
+
     // Get source object from sourcesMap (validRecentRepos are already included in sources)
     const source = sourcesMap.get(selectedSource);
     const defaultBranch = source?.githubRepo?.defaultBranch?.displayName || 'main';
diff --git a/components/jules/create-session/prompt-input.tsx b/components/jules/create-session/prompt-input.tsx
index b320dd9..b642550 100644
--- a/components/jules/create-session/prompt-input.tsx
+++ b/components/jules/create-session/prompt-input.tsx
@@ -31,6 +31,7 @@ export function PromptInput({
         placeholderTextColor={isDark ? '#475569' : '#94a3b8'}
         multiline
         textAlignVertical="top"
+        maxLength={50000}
       />
     </View>
   );
diff --git a/constants/i18n.ts b/constants/i18n.ts
index 1769d17..a9bbccf 100644
--- a/constants/i18n.ts
+++ b/constants/i18n.ts
@@ -70,6 +70,7 @@ const translations = {
     modeReviewDesc: 'プラン確認してから実行',
     startSession: 'セッションを開始する',
     inputError: 'リポジトリを選んで、依頼内容を書いてね！',
+    promptTooLong: '依頼内容が長すぎます（最大50000文字）',
     createSuccess: 'セッションを作成したよ！',
     processing: '処理中...',
     recentRepos: '最近使ったリポジトリ',
@@ -210,6 +211,7 @@ const translations = {
     modeReviewDesc: 'Review plan before execution',
     startSession: 'Start Session',
     inputError: 'Please select a repository and enter your request!',
+    promptTooLong: 'Prompt is too long (max 50000 characters)',
     createSuccess: 'Session created!',
     processing: 'Processing...',
     recentRepos: 'Recent Repositories',
diff --git a/docs/api/reference.md b/docs/api/reference.md
index 8db5083..e100bba 100644
--- a/docs/api/reference.md
+++ b/docs/api/reference.md
@@ -618,8 +618,8 @@ const handleCreateSession = async () => {
      return;
    }
 
-   if (prompt.length > 5000) {
-     Alert.alert('Error', 'Description is too long (max 5000 characters)');
+   if (prompt.length > 50000) {
+     Alert.alert('Error', 'Description is too long (max 50000 characters)');
      return;
    }
    ```