From 9cf3e31af26b33a1d8914e2dbb223a53d3a1c3bf Mon Sep 17 00:00:00 2001
From: Riccardo Giorato <riccardoemanuelegiorato@gmail.com>
Date: Wed, 11 Feb 2026 11:37:28 +0100
Subject: [PATCH] Enforce MAX_USER_PROMPT limit in generate-page-modal and
 comic-creation-form

---
 components/editor/generate-page-modal.tsx  | 20 ++++++----
 components/landing/comic-creation-form.tsx | 10 +++--
 lib/prompt.ts                              | 43 +++++++++++++++++++---
 3 files changed, 58 insertions(+), 15 deletions(-)

diff --git a/components/editor/generate-page-modal.tsx b/components/editor/generate-page-modal.tsx
index dfd0697..466115b 100644
--- a/components/editor/generate-page-modal.tsx
+++ b/components/editor/generate-page-modal.tsx
@@ -15,6 +15,7 @@ import { useKeyboardShortcut } from "@/hooks/use-keyboard-shortcut";
 import { validateFileForUpload, generateFilePreview } from "@/lib/file-utils";
 import { useS3Upload } from "next-s3-upload";
 import { isContentPolicyViolation } from "@/lib/utils";
+import { MAX_SYSTEM_LENGTH, MAX_USER_PROMPT } from "@/lib/prompt";
 
 interface CharacterItem {
   url: string;
@@ -330,13 +331,19 @@ export function GeneratePageModal({
                 <textarea
                   autoFocus
                   value={prompt}
-                  onChange={(e) => setPrompt(e.target.value)}
+
+                  onChange={(e) => setPrompt(e.target.value.slice(
+                    // Only allow users to type up to MAX_SYSTEM_LENGTH characters in the prompt.
+                    // Ensure users cannot paste or otherwise enter more text than the max.
+                    0, MAX_USER_PROMPT))
+                  }
                   placeholder={
                     isRedrawMode
                       ? "Tweak the prompt to improve this page..."
                       : "Continue the story... Describe what happens next."
                   }
                   disabled={isGenerating}
+                  maxLength={MAX_USER_PROMPT}
                   className="w-full bg-transparent border-none text-sm text-white placeholder-muted-foreground/50 focus:ring-0 focus:outline-none resize-none h-20 leading-relaxed tracking-tight"
                 />
 
@@ -358,11 +365,10 @@ export function GeneratePageModal({
                                 onClick={() => toggleCharacterSelection(index)}
                                 onDoubleClick={() => setShowPreview(imageUrl)}
                                 disabled={isGenerating}
-                                className={`w-10 h-10 rounded-md overflow-hidden transition-all disabled:opacity-50 disabled:cursor-not-allowed relative ${
-                                  isSelected
-                                    ? "border-2 border-indigo-500"
-                                    : "border-2 border-transparent hover:border-indigo/50"
-                                }`}
+                                className={`w-10 h-10 rounded-md overflow-hidden transition-all disabled:opacity-50 disabled:cursor-not-allowed relative ${isSelected
+                                  ? "border-2 border-indigo-500"
+                                  : "border-2 border-transparent hover:border-indigo/50"
+                                  }`}
                                 title="Click to select/deselect, double-click to preview"
                               >
                                 <img
@@ -432,7 +438,7 @@ export function GeneratePageModal({
               {isRedrawMode
                 ? "Previous pages and characters automatically referenced."
                 : "Previous page automatically referenced. " +
-                  `${selectedCharacterIndices.size} selected characters.`}
+                `${selectedCharacterIndices.size} selected characters.`}
             </div>
 
             <Button
diff --git a/components/landing/comic-creation-form.tsx b/components/landing/comic-creation-form.tsx
index 3943d04..5b66884 100644
--- a/components/landing/comic-creation-form.tsx
+++ b/components/landing/comic-creation-form.tsx
@@ -12,6 +12,7 @@ import { useKeyboardShortcut } from "@/hooks/use-keyboard-shortcut";
 import { useApiKey } from "@/hooks/use-api-key";
 import { isContentPolicyViolation } from "@/lib/utils";
 import { ApiKeyModal } from "@/components/api-key-modal";
+import { MAX_SYSTEM_LENGTH, MAX_USER_PROMPT } from "@/lib/prompt";
 
 interface ComicCreationFormProps {
   prompt: string;
@@ -328,9 +329,12 @@ export function ComicCreationForm({
           <textarea
             ref={textareaRef}
             value={prompt}
-            onChange={(e) => setPrompt(e.target.value)}
+            onChange={(e) => setPrompt(e.target.value.slice(
+              0, MAX_USER_PROMPT))
+            }
             placeholder="A cyberpunk detective standing in neon rain, holding a glowing datapad, moody lighting, noir style..."
             disabled={isLoading}
+            maxLength={MAX_USER_PROMPT}
             className="w-full bg-transparent border-none text-sm text-white placeholder-muted-foreground/50 focus:ring-0 focus:outline-none resize-none h-16 leading-relaxed disabled:opacity-50 disabled:cursor-not-allowed"
           />
 
@@ -424,8 +428,8 @@ export function ComicCreationForm({
                           setShowStyleDropdown(false);
                         }}
                         className={`w-full text-left px-3 py-2 rounded text-xs transition-colors flex items-center justify-between ${style === styleOption.id
-                            ? "bg-indigo/10 text-indigo"
-                            : "text-muted-foreground hover:bg-white/5 hover:text-white"
+                          ? "bg-indigo/10 text-indigo"
+                          : "text-muted-foreground hover:bg-white/5 hover:text-white"
                           }`}
                       >
                         <span>{styleOption.name}</span>
diff --git a/lib/prompt.ts b/lib/prompt.ts
index 73ce4dc..48c1897 100644
--- a/lib/prompt.ts
+++ b/lib/prompt.ts
@@ -1,5 +1,12 @@
 import { COMIC_STYLES } from "./constants";
 
+// Together AI has a 45000 character limit for the prompt parameter
+// We use 40k total to keep a larger safety margin
+export const MAX_PROMPT_LENGTH = 40000;
+export const MAX_SYSTEM_LENGTH = 35000; // Reserve 5,000 for user's prompt
+
+export const MAX_USER_PROMPT = MAX_PROMPT_LENGTH - MAX_SYSTEM_LENGTH;
+
 export function buildComicPrompt({
   prompt,
   style,
@@ -28,11 +35,37 @@ export function buildComicPrompt({
   }
 
   if (isAddPage && previousPages.length > 0) {
-    const storyHistory = previousPages
-      .map((page, index) => `Page ${index + 1}: ${page.prompt}`)
-      .join("\n");
-
-    continuationContext = `\nSTORY CONTINUATION CONTEXT:\nThis is a continuation of an existing comic story. Here are the previous pages:\n${storyHistory}\n\nThe new page should naturally continue this story. Maintain the same characters, setting, and narrative style. Reference previous events and build upon them.\n`;
+    // Limit previous pages to fit within MAX_SYSTEM_LENGTH
+    // Start with most recent pages and work backwards
+    const header = `\nSTORY CONTINUATION CONTEXT:\nThis is page ${previousPages.length + 1} of an existing comic story. Here are the recent pages for context:\n`;
+    const footer = `\n\nThe new page should naturally continue this story. Maintain the same characters, setting, and narrative style. Reference previous events and build upon them.\n`;
+    
+    // Calculate available space for previous pages (reserve space for rest of system prompt)
+    const basePromptLength = 2500; // Approximate length of system prompt without previous pages
+    const availableSpace = MAX_SYSTEM_LENGTH - basePromptLength - header.length - footer.length;
+    
+    const selectedPages: string[] = [];
+    let currentLength = 0;
+    
+    // Add pages from most recent backwards until we run out of space
+    for (let i = previousPages.length - 1; i >= 0; i--) {
+      const pageEntry = `Page ${i + 1}: ${previousPages[i].prompt}`;
+      const entryLength = pageEntry.length + (selectedPages.length > 0 ? 1 : 0); // +1 for newline
+      
+      if (currentLength + entryLength <= availableSpace) {
+        selectedPages.unshift(pageEntry);
+        currentLength += entryLength;
+      } else {
+        break;
+      }
+    }
+    
+    if (selectedPages.length > 0) {
+      continuationContext = header + selectedPages.join("\n") + footer;
+    } else {
+      // Fallback if no pages fit
+      continuationContext = `\nSTORY CONTINUATION CONTEXT:\nThis is page ${previousPages.length + 1} of an existing comic story with ${previousPages.length} previous pages. Continue the story maintaining consistency.\n`;
+    }
   }
 
   let characterSection = "";