Summarization

src/common/assets/content-editable.module.css

@@ -0,0 +1,10 @@
+.autoLines {
+    overflow: hidden;
+}
+
+.root:empty::before {
+    content: attr(data-placeholder);
+    color: var(--text-muted);
+    font-style: italic;
+    pointer-events: none;
+}

src/common/components/ContentEditable.tsx

@@ -1,8 +1,12 @@
 import { useEffect, useRef } from "preact/hooks";
 import type { JSX } from "preact";
+import clsx from "clsx";
+import styles from "../assets/content-editable.module.css";
 
 type Props = Omit<JSX.HTMLAttributes<HTMLDivElement>, 'value' | 'onInput'> & {
     value: string;
+    placeholder?: string;
+    autoLines?: boolean;
     onInput?: JSX.EventHandler<JSX.TargetedInputEvent<HTMLDivElement>>;
 };
 
@@ -47,7 +51,12 @@ function setCaretOffset(el: HTMLElement, offset: number) {
     sel.addRange(range);
 }
 
-export const ContentEditable = ({ value, onInput, ...props }: Props) => {
+function resizeToContent(el: HTMLElement) {
+    el.style.height = 'auto';
+    el.style.height = el.scrollHeight + 'px';
+}
+
+export const ContentEditable = ({ value, placeholder, autoLines, onInput, class: externalClass, ...props }: Props) => {
     const ref = useRef<HTMLDivElement>(null);
 
     useEffect(() => {
@@ -57,11 +66,11 @@ export const ContentEditable = ({ value, onInput, ...props }: Props) => {
         const offset = document.activeElement === el ? getCaretOffset(el) : null;
         el.innerHTML = value;
         if (offset !== null) setCaretOffset(el, offset);
+        if (autoLines) resizeToContent(el);
     }, [value]);
 
     const handleKeyDown: JSX.KeyboardEventHandler<HTMLDivElement> = (e) => {
         if (e.key !== 'Enter') return;
-        const prevTextContent = (e.target as HTMLDivElement).textContent;
         e.preventDefault();
 
         const sel = window.getSelection();
@@ -75,31 +84,25 @@ export const ContentEditable = ({ value, onInput, ...props }: Props) => {
         range.setStartAfter(newline);
         range.collapse(true);
 
-        const nextTextContent = (e.target as HTMLDivElement).textContent;
-
-        // A trailing \n needs a following character to render in pre-line.
-        // If nothing follows the inserted newline, add a sentinel \n so the
-        // new line is visible, then place the caret before it.
-        const atEnd = nextTextContent.startsWith(prevTextContent) && nextTextContent !== prevTextContent && nextTextContent.length === prevTextContent.length + 1 && nextTextContent.at(-1) === '\n';
-        if (atEnd) {
-            const sentinel = document.createTextNode('\n');
-            range.insertNode(sentinel);
-            range.setStartBefore(sentinel);
-            range.collapse(true);
-        }
-
         sel.removeAllRanges();
         sel.addRange(range);
 
         ref.current?.dispatchEvent(new InputEvent('input', { bubbles: true }));
     };
 
+    const handleInput: JSX.EventHandler<JSX.TargetedInputEvent<HTMLDivElement>> = (e) => {
+        if (autoLines && ref.current) resizeToContent(ref.current);
+        onInput?.(e);
+    };
+
     return (
         <div
             ref={ref}
             contentEditable
             onKeyDown={handleKeyDown}
-            onInput={onInput}
+            onInput={handleInput}
+            data-placeholder={placeholder}
+            class={clsx(styles.root, autoLines && styles.autoLines, externalClass)}
             {...props}
         />
     );

src/games/storywriter/assets/chapters-editor.module.css

@@ -0,0 +1,81 @@
+.chaptersEditor {
+    width: 100%;
+    height: 100%;
+    display: flex;
+    flex-direction: column;
+    gap: 16px;
+}
+
+.empty {
+    color: var(--text-muted);
+    font-style: italic;
+    font-size: 14px;
+}
+
+.chapterCard {
+    background: var(--bg-secondary);
+    border-radius: 8px;
+    padding: 20px;
+    display: flex;
+    flex-direction: column;
+    gap: 16px;
+}
+
+.chapterTitle {
+    font-size: 18px;
+    font-weight: 600;
+    color: var(--text);
+    font-family: 'Georgia', serif;
+    padding-bottom: 12px;
+    border-bottom: 1px solid var(--border);
+}
+
+.chunk {
+    display: flex;
+    flex-direction: column;
+    gap: 8px;
+}
+
+.chunkHeader {
+    font-size: 12px;
+    font-weight: 600;
+    color: var(--text-muted);
+    text-transform: uppercase;
+    letter-spacing: 0.5px;
+}
+
+.chunkPreview {
+    font-size: 13px;
+    color: var(--text-muted);
+    font-style: italic;
+    line-height: 1.5;
+    padding: 8px 12px;
+    background: var(--bg);
+    border-radius: 4px;
+    border-left: 2px solid var(--border);
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+}
+
+.summaryEditable {
+    width: 100%;
+    padding: 10px 12px;
+    background: var(--bg);
+    border: 1px solid var(--border);
+    border-radius: 6px;
+    font-size: 14px;
+    color: var(--text);
+    font-family: inherit;
+    box-sizing: border-box;
+    min-height: 80px;
+    white-space: pre-wrap;
+    word-wrap: break-word;
+
+    &:focus {
+        outline: none;
+        border-color: var(--accent);
+    }
+
+
+}

src/games/storywriter/assets/chat-sidebar.module.css

@@ -133,10 +133,35 @@
 }
 
 .tokenCounter {
+    display: flex;
+    align-items: center;
+    gap: 8px;
     font-size: 11px;
     color: var(--text-muted);
 }
 
+.summarizeButton {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    padding: 4px;
+    color: var(--text-muted);
+    background: transparent;
+    border: 1px solid var(--border);
+    border-radius: 4px;
+    cursor: pointer;
+
+    &:hover:not(:disabled) {
+        color: var(--text);
+        border-color: var(--text-muted);
+    }
+
+    &:disabled {
+        opacity: 0.4;
+        cursor: default;
+    }
+}
+
 .toggleContainer {
     display: flex;
     align-items: center;

src/games/storywriter/assets/editor.module.css

@@ -17,6 +17,7 @@
     text-align: center;
 }
 
+
 .content {
     flex: 1;
     overflow-y: auto;
@@ -65,7 +66,11 @@
     display: flex;
     border-top: 1px solid var(--border);
     padding: 0 12px;
-    gap: 8px;
+    gap: 6px;
+}
+
+.tabRight {
+    margin-left: auto;
 }
 
 .tab {

src/games/storywriter/components/chapters-editor.tsx

@@ -0,0 +1,66 @@
+import { useMemo } from "preact/hooks";
+import { useAppState } from "../contexts/state";
+import Chapters from "../utils/chapters";
+import { ContentEditable } from "@common/components/ContentEditable";
+import { highlight } from "@common/highlight";
+import styles from "../assets/chapters-editor.module.css";
+
+export const ChaptersEditor = () => {
+    const { currentStory, dispatch } = useAppState();
+
+    if (!currentStory) return null;
+
+    const parsed = useMemo(
+        () => Chapters.parseText(currentStory.text),
+        [currentStory.text]
+    );
+
+    if (parsed.length === 0) {
+        return (
+            <div class={styles.chaptersEditor}>
+                <p class={styles.empty}>No chapters yet. Use <code># Chapter Title</code> headers in your story to create chapters.</p>
+            </div>
+        );
+    }
+
+    return (
+        <div class={styles.chaptersEditor}>
+            {parsed.map((parsedChapter) => {
+                const chunks = Chapters.splitIntoChunks(parsedChapter.body);
+                const cachedChapter = (currentStory.chapters ?? []).find(c => c.header === parsedChapter.header)
+                    ?? Chapters.emptyChapter(parsedChapter.header);
+
+                return (
+                    <div class={styles.chapterCard} key={parsedChapter.header || '__preamble__'}>
+                        <div class={styles.chapterTitle}>
+                            {parsedChapter.header ? parsedChapter.header.replace(/^# /, '') : '(Preamble)'}
+                        </div>
+                        {chunks.map((body, i) => {
+                            const { hash, summary } = Chapters.lookupSummary(cachedChapter, body);
+                            return (
+                                <div class={styles.chunk} key={i}>
+                                    {chunks.length > 1 && (
+                                        <div class={styles.chunkHeader}>Part {i + 1}</div>
+                                    )}
+                                    <div class={styles.chunkPreview}>{body}</div>
+                                    <ContentEditable
+                                        class={styles.summaryEditable}
+                                        value={highlight(summary ?? '')}
+                                        placeholder="Not summarized yet..."
+                                        onInput={(e) => dispatch({
+                                            type: 'STORE_CHAPTER_SUMMARY',
+                                            storyId: currentStory.id,
+                                            header: parsedChapter.header,
+                                            hash,
+                                            summary: (e.target as HTMLDivElement).textContent || '',
+                                        })}
+                                    />
+                                </div>
+                            );
+                        })}
+                    </div>
+                );
+            })}
+        </div>
+    );
+};

src/games/storywriter/components/chat-sidebar.tsx

@@ -2,11 +2,13 @@ import { useInputState } from "@common/hooks/useInputState";
 import { highlight } from "@common/highlight";
 import { Sidebar } from "./sidebar";
 import { useAppState, type ChatMessage } from "../contexts/state";
+import { useChapterSummarization } from "../utils/useChapterSummarization";
 import styles from '../assets/chat-sidebar.module.css';
 import { useState, useRef, useEffect, useMemo, useCallback } from "preact/hooks";
 import LLM from "../utils/llm";
 import Prompt from "../utils/prompt";
 import { Tools } from "../utils/tools";
+import { Sparkles } from "lucide-preact";
 import clsx from "clsx";
 
 // ─── Role Header ──────────────────────────────────────────────────────────────
@@ -41,6 +43,7 @@ const RoleHeader = ({ message, chatMessages }: RoleHeaderProps) => {
 export const ChatSidebar = () => {
     const appState = useAppState();
     const { currentStory, dispatch, connection, model, enableThinking } = appState;
+    const { summarizeAll, isSummarizing } = useChapterSummarization();
     const [input, setInput] = useInputState('');
     const [isLoading, setIsLoading] = useState(false);
     const [isCollapsed, setCollapsed] = useState(false);
@@ -336,11 +339,16 @@ export const ChatSidebar = () => {
                                 />
                                 <span>Enable thinking</span>
                             </label>
-                            {tokenCount && (
-                                <div class={styles.tokenCounter}>
-                                    {tokenCount.taken} / {tokenCount.total} tokens
-                                </div>
-                            )}
+                            <div class={styles.tokenCounter}>
+                                {tokenCount && <span>{tokenCount.taken} / {tokenCount.total} tokens</span>}
+                                <button
+                                    class={styles.summarizeButton}
+                                    onClick={summarizeAll}
+                                    disabled={isSummarizing || !currentStory || !connection || !model}
+                                    title={isSummarizing ? 'Summarizing...' : 'Summarize'}>
+                                    <Sparkles size={14} />
+                                </button>
+                            </div>
                         </div>
                         <textarea
                             class={styles.input}

src/games/storywriter/components/editor.tsx

@@ -3,11 +3,14 @@ import { highlight } from "@common/highlight";
 import { useAppState, type Tab } from "../contexts/state";
 import styles from '../assets/editor.module.css';
 import { useMemo } from "preact/hooks";
+import clsx from "clsx";
 import { CharacterEditor } from "./character-editor";
 import { LocationEditor } from "./location-editor";
+import { ChaptersEditor } from "./chapters-editor";
 
 const TABS: { id: Tab; label: string }[] = [
     { id: "story", label: "Story" },
+    { id: "chapters", label: "Chapters" },
     { id: "lore", label: "Lore" },
     { id: "characters", label: "Characters" },
     { id: "locations", label: "Locations" },
@@ -51,7 +54,9 @@ export const Editor = () => {
 
     return (
         <div class={styles.editor}>
-            <div class={styles.title}>{currentStory.title}</div>
+            <div class={styles.title}>
+                {currentStory.title}
+            </div>
             <div class={styles.content}>
                 {currentStory.currentTab === "story" && (
                     <ContentEditable
@@ -75,12 +80,15 @@ export const Editor = () => {
                 {currentStory.currentTab === "locations" && (
                     <LocationEditor />
                 )}
+                {currentStory.currentTab === "chapters" && (
+                    <ChaptersEditor />
+                )}
             </div>
             <div class={styles.tabs}>
                 {TABS.map((tab) => (
                     <button
                         key={tab.id}
-                        class={`${styles.tab} ${currentStory.currentTab === tab.id ? styles.active : ""}`}
+                        class={clsx(styles.tab, currentStory.currentTab === tab.id && styles.active)}
                         onClick={() => handleTabChange(tab.id)}
                     >
                         {tab.label}

src/games/storywriter/contexts/state.tsx

@@ -2,6 +2,7 @@ import { createContext } from "preact";
 import { useContext, useMemo, useReducer } from "preact/hooks";
 
 import LLM from "../utils/llm";
+import Chapters from "../utils/chapters";
 import { useStoredReducer } from "@common/hooks/useStoredState";
 
 // ─── Types ────────────────────────────────────────────────────────────────────
@@ -10,7 +11,7 @@ export type ChatMessage = LLM.ChatMessage & {
     id: string;
 }
 
-export type Tab = "story" | "lore" | "characters" | "locations";
+export type Tab = "story" | "lore" | "characters" | "locations" | "chapters";
 
 export interface Character {
     id: string;
@@ -49,12 +50,12 @@ export interface Story {
     id: string;
     title: string;
     text: string;
-    lastModifiedChunk: string;
     lore: string;
     characters: Character[];
     locations: Location[];
     currentTab: Tab;
     chatMessages: ChatMessage[];
+    chapters: Chapters.Chapter[];
 }
 
 // ─── State ───────────────────────────────────────────────────────────────────
@@ -74,7 +75,7 @@ interface IState {
 type Action =
     | { type: 'CREATE_STORY'; title: string }
     | { type: 'RENAME_STORY'; id: string; title: string }
-    | { type: 'EDIT_STORY'; id: string; text: string; lastModifiedChunk?: string }
+    | { type: 'EDIT_STORY'; id: string; text: string }
     | { type: 'EDIT_LORE'; id: string; lore: string }
     | { type: 'SET_SYSTEM_INSTRUCTION'; systemInstruction: string }
     | { type: 'SET_CURRENT_TAB'; id: string; tab: Tab }
@@ -94,7 +95,9 @@ type Action =
     | { type: 'DELETE_CHARACTER_RELATION'; storyId: string; characterId: string; targetName: string }
     | { type: 'ADD_LOCATION'; storyId: string; location: Location }
     | { type: 'EDIT_LOCATION'; storyId: string; locationId: string; updates: Partial<Location> }
-    | { type: 'DELETE_LOCATION'; storyId: string; locationId: string };
+    | { type: 'DELETE_LOCATION'; storyId: string; locationId: string }
+    | { type: 'STORE_CHAPTER_SUMMARY'; storyId: string; header: string; hash: Chapters.Hash; summary: string }
+    | { type: 'CLEAN_CHAPTER_SUMMARIES'; storyId: string; validHashes: Record<string, Chapters.Hash[]> };
 
 // ─── Initial State ───────────────────────────────────────────────────────────
 
@@ -117,12 +120,12 @@ function reducer(state: IState, action: Action): IState {
                 id: crypto.randomUUID(),
                 title: action.title,
                 text: '',
-                lastModifiedChunk: '',
                 lore: '',
                 characters: [],
                 locations: [],
                 currentTab: 'story',
                 chatMessages: [],
+                chapters: [],
             };
             return {
                 ...state,
@@ -142,11 +145,7 @@ function reducer(state: IState, action: Action): IState {
             return {
                 ...state,
                 stories: state.stories.map(s =>
-                    s.id === action.id ? {
-                        ...s,
-                        text: action.text,
-                        lastModifiedChunk: action.lastModifiedChunk ?? s.lastModifiedChunk
-                    } : s
+                    s.id === action.id ? { ...s, text: action.text } : s
                 ),
             };
         }
@@ -368,6 +367,43 @@ function reducer(state: IState, action: Action): IState {
                 ),
             };
         }
+        case 'CLEAN_CHAPTER_SUMMARIES': {
+            return {
+                ...state,
+                stories: state.stories.map(s => {
+                    if (s.id !== action.storyId) return s;
+                    const chapters = (s.chapters ?? [])
+                        .filter(c => action.validHashes[c.header] !== undefined)
+                        .map(c => {
+                            const valid = new Set(action.validHashes[c.header]);
+                            const summaryCache = Object.fromEntries(
+                                Object.entries(c.summaryCache).filter(([hash]) => valid.has(hash))
+                            );
+                            return { ...c, summaryCache };
+                        });
+                    return { ...s, chapters };
+                }),
+            };
+        }
+        case 'STORE_CHAPTER_SUMMARY': {
+            return {
+                ...state,
+                stories: state.stories.map(s => {
+                    if (s.id !== action.storyId) return s;
+                    const chapters = s.chapters ?? [];
+                    const existing = chapters.find(c => c.header === action.header);
+                    const updated = existing
+                        ? Chapters.storeSummary(existing, action.hash, action.summary)
+                        : Chapters.storeSummary(Chapters.emptyChapter(action.header), action.hash, action.summary);
+                    return {
+                        ...s,
+                        chapters: existing
+                            ? chapters.map(c => c.header === action.header ? updated : c)
+                            : [...chapters, updated],
+                    };
+                }),
+            };
+        }
     }
 }
 

src/games/storywriter/utils/chapters.ts

@@ -0,0 +1,92 @@
+namespace Chapters {
+    export type Hash = string;
+
+    /** Persisted per-story, maps content hash -> cached summary */
+    export interface Chapter {
+        header: string;
+        summaryCache: Record<Hash, string>;
+    }
+
+    /** Transient result of parsing the story text */
+    export interface ParsedChapter {
+        header: string; // empty for preamble before first header
+        body: string;
+    }
+
+    export function hashChunk(text: string): Hash {
+        let h = 5381;
+        for (let i = 0; i < text.length; i++) {
+            h = (h * 33) ^ text.charCodeAt(i);
+        }
+        return (h >>> 0).toString(36);
+    }
+
+    const CHUNK_TARGET_CHARS = 2400; // ~800 tokens
+
+    /** Split a chapter body into paragraph-grouped chunks for summarization */
+    export function splitIntoChunks(body: string): string[] {
+        const paragraphs = body.split(/\n{2,}/).map(p => p.trim()).filter(Boolean);
+        const chunks: string[] = [];
+        let current = '';
+
+        for (const para of paragraphs) {
+            const sep = current ? '\n\n' : '';
+            if (current && current.length + sep.length + para.length > CHUNK_TARGET_CHARS) {
+                chunks.push(current);
+                current = para;
+            } else {
+                current = current + sep + para;
+            }
+        }
+
+        if (current) chunks.push(current);
+        return chunks;
+    }
+
+    /** Split story text into chapters by top-level `# ` headers */
+    export function parseText(text: string): ParsedChapter[] {
+        const lines = text.split('\n');
+        const result: ParsedChapter[] = [];
+        let currentHeader = '';
+        let currentLines: string[] = [];
+
+        for (const line of lines) {
+            if (line.startsWith('# ')) {
+                if (currentHeader || currentLines.length > 0) {
+                    result.push({ header: currentHeader, body: currentLines.join('\n').trim() });
+                }
+                currentHeader = line;
+                currentLines = [];
+            } else {
+                currentLines.push(line);
+            }
+        }
+
+        if (currentHeader || currentLines.length > 0) {
+            result.push({ header: currentHeader, body: currentLines.join('\n').trim() });
+        }
+
+        return result;
+    }
+
+    /**
+     * Look up a cached summary for a parsed chapter body.
+     * Returns the hash (for later cache writes) and the summary if it exists.
+     */
+    export function lookupSummary(chapter: Chapter, body: string): { hash: Hash; summary: string | null } {
+        const h = hashChunk(body);
+        return { hash: h, summary: chapter.summaryCache[h] ?? null };
+    }
+
+    /** Return a new Chapter with the summary stored under the given hash */
+    export function storeSummary(chapter: Chapter, hash: Hash, summary: string): Chapter {
+        return { ...chapter, summaryCache: { ...chapter.summaryCache, [hash]: summary } };
+    }
+
+    /** Create an empty Chapter record for a given header */
+    export function emptyChapter(header: string): Chapter {
+        return { header, summaryCache: {} };
+    }
+}
+
+export default Chapters;

src/games/storywriter/utils/prompt.ts

@@ -1,4 +1,5 @@
 import LLM from "./llm";
+import Chapters from "./chapters";
 import { type AppState, LocationScale } from "../contexts/state";
 import { Tools } from "./tools";
 
@@ -7,56 +8,106 @@ namespace Prompt {
         return text.length / 3;
     }
 
-    export function formatStoryText(text: string, tokenBudget: number): string {
+    const KEEP_RECENT_CHUNKS = 2;
+
+    interface ChunkSlot {
+        header: string;
+        body: string;
+        summary: string | null;
+        mode: 'full' | 'summary' | 'omitted';
+    }
+
+    function buildSlots(text: string, chapters: Chapters.Chapter[]): ChunkSlot[] {
+        const parsed = Chapters.parseText(text);
+        const slots: ChunkSlot[] = [];
+
+        for (const parsedChapter of parsed) {
+            const cachedChapter = chapters.find(c => c.header === parsedChapter.header)
+                ?? Chapters.emptyChapter(parsedChapter.header);
+            const chunks = Chapters.splitIntoChunks(parsedChapter.body);
+
+            for (const body of chunks) {
+                const { summary } = Chapters.lookupSummary(cachedChapter, body);
+                slots.push({ header: parsedChapter.header, body, summary, mode: 'full' });
+            }
+        }
+
+        return slots;
+    }
+
+    function countSlotTokens(slots: ChunkSlot[]): number {
+        let total = 0;
+        const countedHeaders = new Set<string>();
+
+        for (const slot of slots) {
+            if (slot.mode === 'omitted') continue;
+            if (slot.header && !countedHeaders.has(slot.header)) {
+                total += approxTokens(slot.header);
+                countedHeaders.add(slot.header);
+            }
+            total += approxTokens(slot.mode === 'summary' ? (slot.summary ?? '') : slot.body);
+        }
+
+        return total;
+    }
+
+    function renderSlots(slots: ChunkSlot[]): string {
+        const parts: string[] = [];
+        const shownHeaders = new Set<string>();
+
+        for (const slot of slots) {
+            const lines: string[] = [];
+
+            if (slot.header && !shownHeaders.has(slot.header)) {
+                lines.push(slot.header);
+                shownHeaders.add(slot.header);
+            }
+
+            const content = slot.mode === 'omitted' ? '[...]'
+                : slot.mode === 'summary' ? `[Summary: ${slot.summary}]`
+                : slot.body;
+            lines.push(content);
+            parts.push(lines.join('\n\n'));
+        }
+
+        return parts.join('\n\n');
+    }
+
+    export function formatStoryChunks(
+        text: string,
+        chapters: Chapters.Chapter[],
+        tokenBudget: number,
+    ): string {
         if (!text) return '';
 
-        if (approxTokens(text) <= tokenBudget / 2) {
-            return text;
+        const slots = buildSlots(text, chapters);
+        if (slots.length === 0) return '';
+
+        if (countSlotTokens(slots) <= tokenBudget) {
+            return renderSlots(slots);
         }
 
-        const lines = text.split('\n');
-        const separator = '[...]';
-        // Max chars for content = half-budget tokens * 3 chars/token, minus separator overhead
-        const targetChars = Math.floor(tokenBudget / 2 * 3) - separator.length - 2;
+        const recentStart = Math.max(0, slots.length - KEEP_RECENT_CHUNKS);
 
-        if (targetChars <= 0) {
-            return separator;
+        // Phase 1: summarize non-recent chunks, stop as soon as we fit
+        for (let i = 0; i < recentStart; i++) {
+            if (slots[i].summary) {
+                slots[i].mode = 'summary';
+                if (countSlotTokens(slots) <= tokenBudget) return renderSlots(slots);
+            }
         }
 
-        // 1/3 of budget for start, 2/3 for end
-        const startCharsMax = Math.floor(targetChars / 3);
-        const endCharsMax = targetChars - startCharsMax;
+        // Phase 2: delete from middle outward, never delete last slot
+        const middle = recentStart / 2;
+        const deletable = Array.from({ length: recentStart }, (_, i) => i)
+            .sort((a, b) => Math.abs(a - middle) - Math.abs(b - middle));
 
-        let startCharsUsed = 0;
-        let startEnd = 0;
-        for (let i = 0; i < lines.length; i++) {
-            const lineLen = lines[i].length + 1; // +1 for '\n'
-            if (startCharsUsed + lineLen > startCharsMax) break;
-            startCharsUsed += lineLen;
-            startEnd = i + 1;
+        for (const i of deletable) {
+            slots[i].mode = 'omitted';
+            if (countSlotTokens(slots) <= tokenBudget) break;
         }
 
-        let endCharsUsed = 0;
-        let endStart = lines.length;
-        for (let i = lines.length - 1; i >= startEnd; i--) {
-            const lineLen = lines[i].length + 1;
-            if (endCharsUsed + lineLen > endCharsMax) break;
-            endCharsUsed += lineLen;
-            endStart = i;
-        }
-
-        if (startEnd >= endStart) {
-            return text; // All lines fit after all
-        }
-
-        const startPart = lines.slice(0, startEnd).join('\n');
-        const endPart = lines.slice(endStart).join('\n');
-        const parts: string[] = [];
-        if (startPart) parts.push(startPart);
-        parts.push(separator);
-        if (endPart) parts.push(endPart);
-
-        return parts.join('\n');
+        return renderSlots(slots);
     }
 
     export function formatCharactersMarkdown(state: AppState): string {
@@ -138,17 +189,13 @@ namespace Prompt {
         }
 
         if (currentStory.text && storyTokenBudget > 0) {
-            const storyText = formatStoryText(currentStory.text, storyTokenBudget);
+            const storyText = formatStoryChunks(currentStory.text, currentStory.chapters ?? [], storyTokenBudget);
             if (storyText) {
                 parts.push(`## Story\n${storyText}`);
             }
         }
 
-        if (currentStory.lastModifiedChunk) {
-            parts.push(`## Last Modified Chunk\n${currentStory.lastModifiedChunk}`);
-        }
-
-        return parts.join('\n\n');
+return parts.join('\n\n');
     }
 
     export function compilePrompt(state: AppState, newMessages: LLM.ChatMessage[] = []): LLM.ChatCompletionRequest | null {

src/games/storywriter/utils/tools.ts

@@ -29,7 +29,6 @@ export namespace Tools {
                     type: 'EDIT_STORY',
                     id: appState.currentStory.id,
                     text: appState.currentStory.text + args.text,
-                    lastModifiedChunk: args.text
                 });
                 appState.dispatch({
                     type: 'SET_CURRENT_TAB',
@@ -246,7 +245,6 @@ export namespace Tools {
                     type: 'EDIT_STORY',
                     id: appState.currentStory.id,
                     text: appState.currentStory.text.replaceAll(args.old_text, args.new_text),
-                    lastModifiedChunk: args.replace_all ? undefined : args.new_text,
                 });
                 appState.dispatch({
                     type: 'SET_CURRENT_TAB',

src/games/storywriter/utils/useChapterSummarization.ts

@@ -0,0 +1,60 @@
+import { useRef, useState } from 'preact/hooks';
+import { useAppState, type AppState } from '../contexts/state';
+import Chapters from './chapters';
+import LLM from './llm';
+
+export function useChapterSummarization() {
+    const state = useAppState();
+    const stateRef = useRef<AppState>(state);
+    stateRef.current = state;
+
+    const [isSummarizing, setIsSummarizing] = useState(false);
+
+    const summarizeAll = async () => {
+        const { currentStory, connection, model, dispatch } = stateRef.current;
+        if (!currentStory || !connection || !model || isSummarizing) return;
+
+        setIsSummarizing(true);
+        try {
+            const parsed = Chapters.parseText(currentStory.text);
+            const validHashes: Record<string, Chapters.Hash[]> = {};
+
+            for (const parsedChapter of parsed) {
+                const chunks = Chapters.splitIntoChunks(parsedChapter.body);
+                const cachedChapter = (currentStory.chapters ?? [])
+                    .find(c => c.header === parsedChapter.header)
+                    ?? Chapters.emptyChapter(parsedChapter.header);
+
+                validHashes[parsedChapter.header] = [];
+
+                for (const body of chunks) {
+                    const { hash, summary } = Chapters.lookupSummary(cachedChapter, body);
+
+                    if (summary === null) {
+                        const newSummary = await LLM.summarize(connection, model.id, body);
+                        dispatch({
+                            type: 'STORE_CHAPTER_SUMMARY',
+                            storyId: currentStory.id,
+                            header: parsedChapter.header,
+                            hash,
+                            summary: newSummary,
+                        });
+                    }
+
+                    validHashes[parsedChapter.header].push(hash);
+                }
+            }
+
+            // Clean up stale cache entries
+            dispatch({
+                type: 'CLEAN_CHAPTER_SUMMARIES',
+                storyId: currentStory.id,
+                validHashes,
+            });
+        } finally {
+            setIsSummarizing(false);
+        }
+    };
+
+    return { summarizeAll, isSummarizing };
+}