diff --git a/markitect/static/js/core/section-manager.js b/markitect/static/js/core/section-manager.js
new file mode 100644
index 00000000..291b8e69
--- /dev/null
+++ b/markitect/static/js/core/section-manager.js
@@ -0,0 +1,532 @@
+/**
+ * SectionManager Component
+ *
+ * Extracted from monolithic editor.js as part of architecture refactoring.
+ * Manages the collection of sections and their state transitions.
+ *
+ * Dependencies:
+ * - EditState enum (imported)
+ * - SectionType enum (imported)
+ * - Section class (imported)
+ * - debug function (imported)
+ */
+
+// Import dependencies - these will be separate modules
+const EditState = Object.freeze({
+    ORIGINAL: 'original',
+    EDITING: 'editing',
+    MODIFIED: 'modified',
+    SAVED: 'saved'
+});
+
+const SectionType = Object.freeze({
+    HEADING: 'heading',
+    PARAGRAPH: 'paragraph',
+    LIST: 'list',
+    CODE: 'code',
+    QUOTE: 'quote',
+    TABLE: 'table',
+    HR: 'hr',
+    IMAGE: 'image'
+});
+
+// Debug function (will be extracted to utils)
+function debug(message, category = 'INFO') {
+    // Simple console debug for now - will be enhanced later
+    console.log(`DEBUG ${category}: ${message}`);
+}
+
+/**
+ * Section Class - manages individual section state and content
+ */
+class Section {
+    constructor(id, markdown, type) {
+        this.id = id;
+        this.originalMarkdown = markdown;
+        this.currentMarkdown = markdown;
+        this.editingMarkdown = markdown;
+        this.pendingMarkdown = null;
+        this.type = type;
+        this.state = EditState.ORIGINAL;
+        this.domElement = null;
+        this.lastSaved = null;
+        this.created = new Date();
+    }
+
+    static generateId(markdown, position, strategy = 'hash', parentId = null) {
+        return this.generateIdWithStrategy(markdown, position, strategy, parentId);
+    }
+
+    static generateIdWithStrategy(markdown, position, strategy = 'hash', parentId = null) {
+        const sanitizedContent = this.sanitizeContentForId(markdown);
+        const normalizedContent = this.normalizeContentForHashing(sanitizedContent);
+        const sectionType = this.detectType(markdown);
+
+        switch (strategy) {
+            case 'timestamp':
+                return this.generateTimestampId(normalizedContent, position, sectionType);
+            case 'sequential':
+                return this.generateSequentialId(normalizedContent, position, sectionType);
+            case 'hierarchical':
+                return this.generateHierarchicalId(normalizedContent, position, parentId);
+            case 'hash':
+            default:
+                return this.generateAdvancedId(normalizedContent, position, sectionType);
+        }
+    }
+
+    static generateAdvancedId(content, position, sectionType) {
+        const contentHash = this.generateCryptoHash(content);
+        const safeType = sectionType || 'paragraph';
+        const typePrefix = safeType.substring(0, 3);
+        const positionHex = position.toString(16).padStart(2, '0');
+
+        return `section-${typePrefix}-${contentHash}-${positionHex}`;
+    }
+
+    static generateCryptoHash(content) {
+        let hash = 0;
+        if (content.length === 0) return '00000000';
+
+        for (let i = 0; i < content.length; i++) {
+            const char = content.charCodeAt(i);
+            hash = ((hash << 5) - hash) + char;
+            hash = hash & hash;
+        }
+
+        const hexHash = Math.abs(hash).toString(16).padStart(8, '0');
+        return hexHash.substring(0, 8);
+    }
+
+    static normalizeContentForHashing(content) {
+        if (!content || typeof content !== 'string') {
+            return '';
+        }
+
+        return content
+            .trim()
+            .replace(/\s+/g, ' ')
+            .replace(/\r\n/g, '\n')
+            .toLowerCase();
+    }
+
+    static sanitizeContentForId(content) {
+        if (!content || typeof content !== 'string') {
+            return '';
+        }
+
+        return content
+            .replace(/<[^>]*>/g, '')
+            .replace(/javascript:/gi, '')
+            .replace(/[^\w\s\-_.#]/g, '')
+            .trim();
+    }
+
+    static generateTimestampId(content, position = 0, sectionType = 'paragraph') {
+        const timestamp = Date.now().toString(36);
+        const contentSnippet = this.generateCryptoHash(content || '').substring(0, 4);
+        const safeType = sectionType || 'paragraph';
+        const typePrefix = safeType.substring(0, 3);
+
+        return `section-${typePrefix}-${contentSnippet}-${timestamp}`;
+    }
+
+    static generateSequentialId(content, position, sectionType = 'paragraph') {
+        const safeType = sectionType || 'paragraph';
+        const typePrefix = safeType.substring(0, 3);
+        const seqNumber = (position || 0).toString().padStart(3, '0');
+        const contentHash = this.generateCryptoHash(content || '').substring(0, 4);
+
+        return `section-${typePrefix}-seq${seqNumber}-${contentHash}`;
+    }
+
+    static generateHierarchicalId(content, position, parentId = null) {
+        const contentHash = this.generateCryptoHash(content || '').substring(0, 6);
+
+        if (parentId) {
+            const childIndex = (position || 0).toString().padStart(2, '0');
+            return `${parentId}-child-${childIndex}-${contentHash}`;
+        } else {
+            return `section-root-${position || 0}-${contentHash}`;
+        }
+    }
+
+    static detectType(markdown) {
+        if (!markdown || typeof markdown !== 'string') {
+            return SectionType.PARAGRAPH;
+        }
+
+        const content = markdown.replace(/^\n+|\n+$/g, '');
+        if (!content) {
+            return SectionType.PARAGRAPH;
+        }
+
+        const trimmed = content.trim();
+
+        // Detection order matters - most specific first
+        if (this.isHeading(trimmed)) {
+            return SectionType.HEADING;
+        }
+
+        if (this.isImage(trimmed)) {
+            return SectionType.IMAGE;
+        }
+
+        if (this.isCodeBlock(trimmed)) {
+            return SectionType.CODE;
+        }
+
+        return SectionType.PARAGRAPH;
+    }
+
+    static isHeading(trimmed) {
+        const headingPattern = /^#{1,6}\s+.+/;
+        return headingPattern.test(trimmed);
+    }
+
+    static isImage(trimmed) {
+        const imagePattern = /!\[.*?\]\([^)]+\)/;
+        return imagePattern.test(trimmed);
+    }
+
+    static isCodeBlock(trimmed) {
+        if (trimmed.startsWith('```') || trimmed.startsWith('~~~')) {
+            return true;
+        }
+        if (trimmed.includes('```') || trimmed.includes('~~~')) {
+            const codeBlockPattern = /```[\s\S]*?```|~~~[\s\S]*?~~~/;
+            if (codeBlockPattern.test(trimmed)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    startEdit() {
+        if (this.state === EditState.EDITING) {
+            throw new Error(`Section ${this.id} is already being edited`);
+        }
+        this.editingMarkdown = this.pendingMarkdown || this.currentMarkdown;
+        this.state = EditState.EDITING;
+        return this.editingMarkdown;
+    }
+
+    updateContent(markdown) {
+        if (this.state !== EditState.EDITING) {
+            throw new Error(`Section ${this.id} is not in editing state`);
+        }
+        this.editingMarkdown = markdown;
+    }
+
+    acceptChanges() {
+        if (this.state !== EditState.EDITING) {
+            throw new Error(`Section ${this.id} is not in editing state`);
+        }
+        this.currentMarkdown = this.editingMarkdown;
+        this.editingMarkdown = null;
+        this.pendingMarkdown = null;
+        this.state = EditState.SAVED;
+        this.lastSaved = new Date();
+        return this.currentMarkdown;
+    }
+
+    cancelChanges() {
+        if (this.state !== EditState.EDITING) {
+            throw new Error(`Section ${this.id} is not in editing state`);
+        }
+        this.editingMarkdown = null;
+        if (this.pendingMarkdown !== null) {
+            this.state = EditState.MODIFIED;
+            return this.pendingMarkdown;
+        } else if (this.lastSaved !== null) {
+            this.state = EditState.SAVED;
+            return this.currentMarkdown;
+        } else {
+            this.state = this.hasChanges() ? EditState.MODIFIED : EditState.ORIGINAL;
+            return this.currentMarkdown;
+        }
+    }
+
+    stopEditing() {
+        if (this.state !== EditState.EDITING) {
+            return this.state;
+        }
+
+        if (this.editingMarkdown && this.editingMarkdown !== this.currentMarkdown) {
+            this.pendingMarkdown = this.editingMarkdown;
+            this.state = EditState.MODIFIED;
+        } else {
+            this.pendingMarkdown = null;
+            if (this.lastSaved !== null) {
+                this.state = EditState.SAVED;
+            } else {
+                this.state = this.hasChanges() ? EditState.MODIFIED : EditState.ORIGINAL;
+            }
+        }
+
+        this.editingMarkdown = null;
+        return this.state;
+    }
+
+    resetToOriginal() {
+        this.currentMarkdown = this.originalMarkdown;
+        this.editingMarkdown = this.originalMarkdown;
+        this.pendingMarkdown = null;
+        this.state = EditState.ORIGINAL;
+        return this.originalMarkdown;
+    }
+
+    isEditing() {
+        return this.state === EditState.EDITING;
+    }
+
+    hasChanges() {
+        return this.currentMarkdown !== this.originalMarkdown;
+    }
+
+    getStatus() {
+        return {
+            id: this.id,
+            state: this.state,
+            hasChanges: this.hasChanges(),
+            isEditing: this.isEditing(),
+            contentLength: this.currentMarkdown.length,
+            lastSaved: this.lastSaved,
+            type: this.type,
+            originalLength: this.originalMarkdown.length,
+            currentLength: this.currentMarkdown.length
+        };
+    }
+
+    isImage() {
+        return this.type === SectionType.IMAGE;
+    }
+
+    redetectType(content = null) {
+        const markdown = content || this.currentMarkdown;
+        const oldType = this.type;
+        this.type = Section.detectType(markdown);
+
+        if (oldType !== this.type) {
+            debug(`Section ${this.id} type changed from ${oldType} to ${this.type}`, 'TYPE_DETECTION');
+        }
+
+        return this.type;
+    }
+}
+
+/**
+ * SectionManager - Manages the collection of sections
+ */
+class SectionManager {
+    constructor() {
+        this.sections = new Map();
+        this.listeners = new Map();
+        this.statusInterval = null;
+        this.lastStatusUpdate = new Date().toISOString();
+    }
+
+    on(event, callback) {
+        if (!this.listeners.has(event)) {
+            this.listeners.set(event, []);
+        }
+        this.listeners.get(event).push(callback);
+    }
+
+    emit(event, data) {
+        if (this.listeners.has(event)) {
+            this.listeners.get(event).forEach(callback => callback(data));
+        }
+    }
+
+    createSectionsFromMarkdown(markdownContent) {
+        const lines = markdownContent.split('\n');
+        const sections = [];
+        let currentSection = '';
+        let position = 0;
+
+        for (let i = 0; i < lines.length; i++) {
+            const line = lines[i];
+            const isHeading = /^#{1,6}\s/.test(line);
+            const isNewParagraph = line.trim() && i > 0 && !lines[i-1].trim();
+            const isNewSection = isHeading || isNewParagraph;
+
+            if (isNewSection && currentSection.trim()) {
+                const sectionId = Section.generateId(currentSection, position);
+                const sectionType = Section.detectType(currentSection);
+                const section = new Section(sectionId, currentSection.trim(), sectionType);
+                sections.push(section);
+                this.sections.set(sectionId, section);
+                position++;
+                currentSection = line;
+            } else {
+                if (currentSection) currentSection += '\n';
+                currentSection += line;
+            }
+        }
+
+        if (currentSection.trim()) {
+            const sectionId = Section.generateId(currentSection, position);
+            const sectionType = Section.detectType(currentSection);
+            const section = new Section(sectionId, currentSection.trim(), sectionType);
+            sections.push(section);
+            this.sections.set(sectionId, section);
+        }
+
+        this.emit('sections-created', { sections, count: sections.length });
+        return sections;
+    }
+
+    startEditing(sectionId) {
+        debug('MANAGER: startEditing called for: ' + sectionId, 'MANAGER');
+
+        const section = this.sections.get(sectionId);
+        if (!section) {
+            throw new Error(`Section ${sectionId} not found`);
+        }
+
+        if (section.isEditing()) {
+            debug('MANAGER: Section already in editing state: ' + sectionId, 'MANAGER');
+            return section.editingMarkdown;
+        }
+
+        debug('MANAGER: Starting edit for section: ' + sectionId, 'MANAGER');
+        const content = section.startEdit();
+
+        debug('MANAGER: About to emit edit-started event for: ' + sectionId, 'MANAGER');
+        this.emit('edit-started', { sectionId, content, section: section.getStatus() });
+        debug('MANAGER: Emitted edit-started event for: ' + sectionId, 'MANAGER');
+
+        return content;
+    }
+
+    updateContent(sectionId, markdown) {
+        const section = this.sections.get(sectionId);
+        if (!section) {
+            throw new Error(`Section ${sectionId} not found`);
+        }
+
+        const oldType = section.type;
+        section.updateContent(markdown);
+        const newType = section.redetectType(markdown);
+
+        const eventData = {
+            sectionId,
+            markdown,
+            section: section.getStatus(),
+            typeChanged: oldType !== newType,
+            oldType,
+            newType
+        };
+
+        this.emit('content-updated', eventData);
+
+        if (oldType !== newType) {
+            this.emit('section-type-changed', {
+                sectionId,
+                oldType,
+                newType,
+                section: section.getStatus()
+            });
+        }
+    }
+
+    acceptChanges(sectionId) {
+        const section = this.sections.get(sectionId);
+        if (!section) {
+            throw new Error(`Section ${sectionId} not found`);
+        }
+
+        const content = section.acceptChanges();
+        this.emit('changes-accepted', { sectionId, content, section: section.getStatus() });
+        return content;
+    }
+
+    cancelChanges(sectionId) {
+        const section = this.sections.get(sectionId);
+        if (!section) {
+            throw new Error(`Section ${sectionId} not found`);
+        }
+
+        const content = section.cancelChanges();
+        this.emit('changes-cancelled', { sectionId, content, section: section.getStatus() });
+        return content;
+    }
+
+    resetSection(sectionId) {
+        const section = this.sections.get(sectionId);
+        if (!section) {
+            throw new Error(`Section ${sectionId} not found`);
+        }
+
+        const content = section.resetToOriginal();
+        this.emit('section-reset', { sectionId, content, section: section.getStatus() });
+        return content;
+    }
+
+    getDocumentMarkdown() {
+        const sortedSections = Array.from(this.sections.values())
+            .sort((a, b) => a.created - b.created);
+
+        return sortedSections.map(section => section.currentMarkdown).join('\n\n');
+    }
+
+    getAllSections() {
+        return Array.from(this.sections.values());
+    }
+
+    getDocumentStatus() {
+        const sections = Array.from(this.sections.values());
+        const editingSections = sections.filter(section => section.isEditing).length;
+
+        return {
+            totalSections: sections.length,
+            editingSections: editingSections
+        };
+    }
+
+    extractHeadings(content) {
+        if (!content) return [];
+        const lines = content.split('\n');
+        return lines.filter(line => /^#{1,6}\s/.test(line.trim()));
+    }
+
+    handleSectionSplit(sectionId, newContent) {
+        const section = this.sections.get(sectionId);
+        if (!section) {
+            throw new Error(`Section ${sectionId} not found`);
+        }
+
+        // Remove the original section
+        this.sections.delete(sectionId);
+
+        // Create new sections from the content
+        const newSections = this.createSectionsFromMarkdown(newContent);
+
+        // Emit section-split event
+        this.emit('section-split', {
+            originalSectionId: sectionId,
+            newSections: newSections,
+            count: newSections.length
+        });
+
+        return newSections;
+    }
+
+    createSectionsFromContent(content) {
+        return this.createSectionsFromMarkdown(content);
+    }
+}
+
+// Export for use in tests and other modules
+if (typeof module !== 'undefined' && module.exports) {
+    module.exports = { SectionManager, Section, EditState, SectionType };
+}
+
+// Export for browser use
+if (typeof window !== 'undefined') {
+    window.SectionManager = SectionManager;
+    window.Section = Section;
+    window.EditState = EditState;
+    window.SectionType = SectionType;
+}
\ No newline at end of file
diff --git a/markitect/static/js/tests/refactor-test-runner.js b/markitect/static/js/tests/refactor-test-runner.js
new file mode 100644
index 00000000..ecc97529
--- /dev/null
+++ b/markitect/static/js/tests/refactor-test-runner.js
@@ -0,0 +1,216 @@
+#!/usr/bin/env node
+
+/**
+ * TDD Test Runner for JavaScript Refactoring
+ *
+ * Drives component extraction and testing during architecture refactoring.
+ * Ensures all functionality remains stable while achieving separation of concerns.
+ */
+
+class RefactorTestRunner {
+    constructor() {
+        this.tests = [];
+        this.passed = 0;
+        this.failed = 0;
+        this.currentSuite = null;
+        this.setupDOM();
+    }
+
+    setupDOM() {
+        // Set up minimal DOM environment for testing
+        if (typeof document === 'undefined') {
+            const { JSDOM } = require('jsdom');
+            const dom = new JSDOM('<!DOCTYPE html><html><body></body></html>', {
+                url: 'http://localhost',
+                pretendToBeVisual: true,
+                resources: 'usable'
+            });
+
+            global.window = dom.window;
+            global.document = dom.window.document;
+            global.HTMLElement = dom.window.HTMLElement;
+            global.Event = dom.window.Event;
+            global.CustomEvent = dom.window.CustomEvent;
+
+            // Only set navigator if it doesn't exist
+            if (typeof global.navigator === 'undefined') {
+                global.navigator = dom.window.navigator;
+            }
+        }
+    }
+
+    describe(suiteName, fn) {
+        console.log(`\n📁 ${suiteName}`);
+        this.currentSuite = suiteName;
+        fn();
+        this.currentSuite = null;
+    }
+
+    it(testName, fn) {
+        const fullName = this.currentSuite ? `${this.currentSuite}: ${testName}` : testName;
+
+        try {
+            fn();
+            console.log(`  ✅ ${testName}`);
+            this.passed++;
+        } catch (error) {
+            console.log(`  ❌ ${testName}`);
+            console.log(`     Error: ${error.message}`);
+            if (error.stack) {
+                console.log(`     Stack: ${error.stack.split('\n')[1]?.trim()}`);
+            }
+            this.failed++;
+        }
+    }
+
+    expect(actual) {
+        return {
+            toBe: (expected) => {
+                if (actual !== expected) {
+                    throw new Error(`Expected ${expected}, got ${actual}`);
+                }
+            },
+            toBeTruthy: () => {
+                if (!actual) {
+                    throw new Error(`Expected truthy value, got ${actual}`);
+                }
+            },
+            toBeFalsy: () => {
+                if (actual) {
+                    throw new Error(`Expected falsy value, got ${actual}`);
+                }
+            },
+            toEqual: (expected) => {
+                if (JSON.stringify(actual) !== JSON.stringify(expected)) {
+                    throw new Error(`Expected ${JSON.stringify(expected)}, got ${JSON.stringify(actual)}`);
+                }
+            },
+            toContain: (expected) => {
+                if (!actual.includes(expected)) {
+                    throw new Error(`Expected ${actual} to contain ${expected}`);
+                }
+            },
+            toHaveProperty: (property) => {
+                if (!(property in actual)) {
+                    throw new Error(`Expected object to have property ${property}`);
+                }
+            },
+            toBeInstanceOf: (expectedClass) => {
+                if (!(actual instanceof expectedClass)) {
+                    throw new Error(`Expected instance of ${expectedClass.name}, got ${actual.constructor.name}`);
+                }
+            }
+        };
+    }
+
+    /**
+     * Test that a component can be extracted from the monolith without breaking functionality
+     */
+    testComponentExtraction(componentName, extractFn, originalTests) {
+        this.describe(`Component Extraction: ${componentName}`, () => {
+            this.it('should extract without syntax errors', () => {
+                try {
+                    const component = extractFn();
+                    this.expect(component).toBeTruthy();
+                } catch (error) {
+                    throw new Error(`Component extraction failed: ${error.message}`);
+                }
+            });
+
+            this.it('should maintain original API', () => {
+                const component = extractFn();
+                originalTests.forEach(test => {
+                    try {
+                        test(component);
+                    } catch (error) {
+                        throw new Error(`API compatibility test failed: ${error.message}`);
+                    }
+                });
+            });
+        });
+    }
+
+    /**
+     * Test component integration after extraction
+     */
+    testComponentIntegration(components, integrationTests) {
+        this.describe('Component Integration', () => {
+            integrationTests.forEach((test, index) => {
+                this.it(`integration test ${index + 1}`, () => {
+                    test(components);
+                });
+            });
+        });
+    }
+
+    /**
+     * Setup test environment with mock dependencies
+     */
+    setupTestEnvironment() {
+        // Create test container
+        const container = document.createElement('div');
+        container.id = 'test-container';
+        container.innerHTML = '<div id="markdown-content"></div>';
+        document.body.appendChild(container);
+
+        // Mock any global dependencies
+        global.mockSectionManager = {
+            sections: new Map(),
+            createSectionsFromMarkdown: () => [],
+            startEditing: () => true,
+            stopEditing: () => true,
+            getAllSections: () => []
+        };
+
+        return { container };
+    }
+
+    /**
+     * Cleanup test environment
+     */
+    cleanupTestEnvironment() {
+        const container = document.getElementById('test-container');
+        if (container) {
+            container.remove();
+        }
+
+        // Clear any global mocks
+        delete global.mockSectionManager;
+    }
+
+    async run() {
+        console.log('🧪 TDD Refactoring Test Runner Starting...\n');
+
+        const startTime = Date.now();
+
+        // Run all collected tests
+        // Tests will be added by importing component test files
+
+        const endTime = Date.now();
+        const duration = endTime - startTime;
+
+        console.log(`\n📊 Test Results:`);
+        console.log(`   ✅ Passed: ${this.passed}`);
+        console.log(`   ❌ Failed: ${this.failed}`);
+        console.log(`   ⏱️  Duration: ${duration}ms`);
+
+        if (this.failed > 0) {
+            console.log(`\n❌ ${this.failed} test(s) failed. Refactoring should not proceed.`);
+            process.exit(1);
+        } else {
+            console.log(`\n✅ All tests passed! Refactoring is safe to continue.`);
+        }
+    }
+}
+
+// Export for use in component tests
+if (typeof module !== 'undefined' && module.exports) {
+    module.exports = { RefactorTestRunner };
+}
+
+// Export for browser use
+if (typeof window !== 'undefined') {
+    window.RefactorTestRunner = RefactorTestRunner;
+}
+
+module.exports = RefactorTestRunner;
\ No newline at end of file
diff --git a/markitect/static/js/tests/test-extracted-section-manager.js b/markitect/static/js/tests/test-extracted-section-manager.js
new file mode 100644
index 00000000..0eb51d01
--- /dev/null
+++ b/markitect/static/js/tests/test-extracted-section-manager.js
@@ -0,0 +1,226 @@
+#!/usr/bin/env node
+
+/**
+ * TDD Test for Extracted SectionManager Component
+ *
+ * Tests the extracted SectionManager component independently from the monolith.
+ * Verifies that all functionality is preserved after extraction.
+ */
+
+const RefactorTestRunner = require('./refactor-test-runner.js');
+
+const runner = new RefactorTestRunner();
+
+runner.describe('Extracted SectionManager Component', () => {
+
+    runner.it('should load extracted SectionManager component', () => {
+        // Load the extracted component
+        delete require.cache[require.resolve('../core/section-manager.js')];
+
+        try {
+            const module = require('../core/section-manager.js');
+            runner.expect(module.SectionManager).toBeTruthy();
+            runner.expect(module.Section).toBeTruthy();
+            runner.expect(module.EditState).toBeTruthy();
+            runner.expect(module.SectionType).toBeTruthy();
+
+            // Set globals for other tests
+            global.ExtractedSectionManager = module.SectionManager;
+            global.ExtractedSection = module.Section;
+            global.ExtractedEditState = module.EditState;
+            global.ExtractedSectionType = module.SectionType;
+        } catch (error) {
+            throw new Error(`Failed to load extracted SectionManager: ${error.message}`);
+        }
+    });
+
+    runner.it('should preserve constructor functionality', () => {
+        const SectionManager = global.ExtractedSectionManager;
+
+        const manager = new SectionManager();
+        runner.expect(manager).toBeInstanceOf(SectionManager);
+        runner.expect(manager.sections).toBeInstanceOf(Map);
+        runner.expect(manager.listeners).toBeInstanceOf(Map);
+    });
+
+    runner.it('should preserve section creation functionality', () => {
+        const SectionManager = global.ExtractedSectionManager;
+        const manager = new SectionManager();
+
+        const testMarkdown = `# Heading 1\nContent 1\n\n## Heading 2\nContent 2`;
+        const sections = manager.createSectionsFromMarkdown(testMarkdown);
+
+        runner.expect(Array.isArray(sections)).toBeTruthy();
+        runner.expect(sections.length).toBe(2);
+        runner.expect(sections[0].currentMarkdown).toContain('Heading 1');
+        runner.expect(sections[1].currentMarkdown).toContain('Heading 2');
+    });
+
+    runner.it('should preserve section editing functionality', () => {
+        const SectionManager = global.ExtractedSectionManager;
+        const manager = new SectionManager();
+
+        const sections = manager.createSectionsFromMarkdown('# Test\nContent');
+        const sectionId = sections[0].id;
+
+        // Test start editing
+        const content = manager.startEditing(sectionId);
+        runner.expect(content).toContain('Test');
+
+        const section = manager.sections.get(sectionId);
+        runner.expect(section.isEditing()).toBeTruthy();
+
+        // Test stop editing
+        section.stopEditing();
+        runner.expect(section.isEditing()).toBeFalsy();
+    });
+
+    runner.it('should preserve event system functionality', () => {
+        const SectionManager = global.ExtractedSectionManager;
+        const manager = new SectionManager();
+
+        let eventFired = false;
+        let eventData = null;
+
+        manager.on('test-event', (data) => {
+            eventFired = true;
+            eventData = data;
+        });
+
+        manager.emit('test-event', { test: 'data' });
+
+        runner.expect(eventFired).toBeTruthy();
+        runner.expect(eventData).toEqual({ test: 'data' });
+    });
+
+    runner.it('should preserve document status functionality', () => {
+        const SectionManager = global.ExtractedSectionManager;
+        const manager = new SectionManager();
+
+        manager.createSectionsFromMarkdown('# Test\nContent');
+        const status = manager.getDocumentStatus();
+
+        runner.expect(status).toHaveProperty('totalSections');
+        runner.expect(status).toHaveProperty('editingSections');
+        runner.expect(status.totalSections).toBe(1);
+    });
+
+    runner.it('should preserve getAllSections functionality', () => {
+        const SectionManager = global.ExtractedSectionManager;
+        const manager = new SectionManager();
+
+        const testMarkdown = '# One\nContent\n\n# Two\nMore content';
+        manager.createSectionsFromMarkdown(testMarkdown);
+
+        const allSections = manager.getAllSections();
+        runner.expect(Array.isArray(allSections)).toBeTruthy();
+        runner.expect(allSections.length).toBe(2);
+    });
+
+    runner.it('should preserve section splitting functionality', () => {
+        const SectionManager = global.ExtractedSectionManager;
+        const manager = new SectionManager();
+
+        const sections = manager.createSectionsFromMarkdown('# Original\nContent');
+        const sectionId = sections[0].id;
+
+        const newContent = '# Split 1\nContent 1\n\n# Split 2\nContent 2';
+        const newSections = manager.handleSectionSplit(sectionId, newContent);
+
+        runner.expect(Array.isArray(newSections)).toBeTruthy();
+        runner.expect(newSections.length).toBe(2);
+        runner.expect(manager.sections.has(sectionId)).toBeFalsy(); // Original removed
+    });
+
+    runner.it('should preserve Section class functionality', () => {
+        const Section = global.ExtractedSection;
+        const EditState = global.ExtractedEditState;
+
+        const section = new Section('test-id', '# Test Content', 'heading');
+
+        runner.expect(section.id).toBe('test-id');
+        runner.expect(section.currentMarkdown).toBe('# Test Content');
+        runner.expect(section.type).toBe('heading');
+        runner.expect(section.state).toBe(EditState.ORIGINAL);
+    });
+
+    runner.it('should preserve Section ID generation', () => {
+        const Section = global.ExtractedSection;
+
+        const id1 = Section.generateId('# Test Heading', 0);
+        const id2 = Section.generateId('# Different Heading', 1);
+
+        runner.expect(typeof id1 === 'string').toBeTruthy();
+        runner.expect(typeof id2 === 'string').toBeTruthy();
+        runner.expect(id1).toContain('section-');
+        runner.expect(id2).toContain('section-');
+        runner.expect(id1 !== id2).toBeTruthy(); // Should be unique
+    });
+
+    runner.it('should preserve Section type detection', () => {
+        const Section = global.ExtractedSection;
+        const SectionType = global.ExtractedSectionType;
+
+        runner.expect(Section.detectType('# Heading')).toBe(SectionType.HEADING);
+        runner.expect(Section.detectType('![Image](url)')).toBe(SectionType.IMAGE);
+        runner.expect(Section.detectType('```code```')).toBe(SectionType.CODE);
+        runner.expect(Section.detectType('Regular paragraph')).toBe(SectionType.PARAGRAPH);
+    });
+
+    // Comparative test - verify extracted component behaves identically to original
+    runner.it('should behave identically to original monolithic component', () => {
+        // Load both components
+        const originalModule = require('/home/worsch/markitect_project/markitect/static/editor.js');
+        const extractedModule = require('../core/section-manager.js');
+
+        const originalManager = new originalModule.SectionManager();
+        const extractedManager = new extractedModule.SectionManager();
+
+        const testMarkdown = '# Test\nContent\n\n## Subheading\nMore content';
+
+        // Debug: Check what each component produces
+        console.log('Creating sections with original component...');
+        const originalSections = originalManager.createSectionsFromMarkdown(testMarkdown);
+        console.log(`Original produced ${originalSections.length} sections`);
+
+        console.log('Creating sections with extracted component...');
+        const extractedSections = extractedManager.createSectionsFromMarkdown(testMarkdown);
+        console.log(`Extracted produced ${extractedSections.length} sections`);
+
+        if (originalSections.length > 0) {
+            console.log('Original first section:', originalSections[0].currentMarkdown);
+        }
+        if (extractedSections.length > 0) {
+            console.log('Extracted first section:', extractedSections[0].currentMarkdown);
+        }
+
+        // Should have same number of sections
+        runner.expect(extractedSections.length).toBe(originalSections.length);
+
+        // Should have same content
+        for (let i = 0; i < originalSections.length; i++) {
+            runner.expect(extractedSections[i].currentMarkdown).toBe(originalSections[i].currentMarkdown);
+            runner.expect(extractedSections[i].type).toBe(originalSections[i].type);
+        }
+
+        // Should have same document status structure
+        const originalStatus = originalManager.getDocumentStatus();
+        const extractedStatus = extractedManager.getDocumentStatus();
+
+        console.log('Original status:', originalStatus);
+        console.log('Extracted status:', extractedStatus);
+
+        runner.expect(extractedStatus.totalSections).toBe(originalStatus.totalSections);
+        runner.expect(extractedStatus.editingSections).toBe(originalStatus.editingSections);
+    });
+});
+
+module.exports = runner;
+
+// Run tests if called directly
+if (require.main === module) {
+    console.log('🧪 Testing Extracted SectionManager Component');
+    runner.run().then(() => {
+        console.log('✅ Extracted SectionManager tests completed');
+    });
+}
\ No newline at end of file
diff --git a/markitect/static/js/tests/test-section-manager-extraction.js b/markitect/static/js/tests/test-section-manager-extraction.js
new file mode 100644
index 00000000..1eecce5d
--- /dev/null
+++ b/markitect/static/js/tests/test-section-manager-extraction.js
@@ -0,0 +1,196 @@
+#!/usr/bin/env node
+
+/**
+ * TDD Test for SectionManager Component Extraction
+ *
+ * Tests the extraction of SectionManager from the monolithic editor.js
+ * Ensures all functionality is preserved during refactoring.
+ */
+
+const RefactorTestRunner = require('./refactor-test-runner.js');
+
+const runner = new RefactorTestRunner();
+
+// First, let's define what the SectionManager API should look like
+const EXPECTED_SECTION_MANAGER_API = [
+    'constructor',
+    'createSectionsFromMarkdown',
+    'startEditing',
+    'stopEditing',
+    'getAllSections',
+    'sections', // Map property, not method
+    'getDocumentStatus',
+    'getDocumentMarkdown',
+    'on', // event system
+    'emit', // event system
+    'handleSectionSplit',
+    'updateContent',
+    'acceptChanges',
+    'cancelChanges',
+    'resetSection'
+];
+
+runner.describe('SectionManager Component Extraction', () => {
+
+    runner.it('should define expected API methods', () => {
+        // This test defines what we expect from the extracted SectionManager
+        const expectedMethods = EXPECTED_SECTION_MANAGER_API;
+        runner.expect(expectedMethods.length).toBe(15);
+        runner.expect(expectedMethods).toContain('createSectionsFromMarkdown');
+        runner.expect(expectedMethods).toContain('startEditing');
+        runner.expect(expectedMethods).toContain('stopEditing');
+    });
+
+    runner.it('should extract from monolithic editor.js', () => {
+        // Load the monolithic editor.js to extract SectionManager
+        delete require.cache[require.resolve('/home/worsch/markitect_project/markitect/static/editor.js')];
+
+        try {
+            const editorModule = require('/home/worsch/markitect_project/markitect/static/editor.js');
+            runner.expect(editorModule.SectionManager).toBeTruthy();
+            // Set global for other tests
+            global.SectionManager = editorModule.SectionManager;
+            global.Section = editorModule.Section;
+            global.EditState = editorModule.EditState;
+        } catch (error) {
+            throw new Error(`Failed to load monolithic editor.js: ${error.message}`);
+        }
+    });
+
+    runner.it('should preserve SectionManager constructor functionality', () => {
+        const SectionManager = global.SectionManager;
+
+        const manager = new SectionManager();
+        runner.expect(manager).toBeInstanceOf(SectionManager);
+        runner.expect(manager.sections).toBeInstanceOf(Map);
+    });
+
+    runner.it('should preserve createSectionsFromMarkdown functionality', () => {
+        const SectionManager = global.SectionManager;
+        const manager = new SectionManager();
+
+        const testMarkdown = `# Heading 1\nContent 1\n\n## Heading 2\nContent 2`;
+        const sections = manager.createSectionsFromMarkdown(testMarkdown);
+
+        runner.expect(Array.isArray(sections)).toBeTruthy();
+        runner.expect(sections.length).toBe(2);
+        runner.expect(sections[0].currentMarkdown).toContain('Heading 1');
+        runner.expect(sections[1].currentMarkdown).toContain('Heading 2');
+    });
+
+    runner.it('should preserve section editing state management', () => {
+        const SectionManager = global.SectionManager;
+        const manager = new SectionManager();
+
+        const sections = manager.createSectionsFromMarkdown('# Test\nContent');
+        const sectionId = sections[0].id;
+
+        // Test start editing
+        runner.expect(manager.startEditing(sectionId)).toBeTruthy();
+        const section = manager.sections.get(sectionId);
+        runner.expect(section.isEditing()).toBeTruthy();
+
+        // Test stop editing
+        section.stopEditing();
+        runner.expect(section.isEditing()).toBeFalsy();
+    });
+
+    runner.it('should preserve event system functionality', () => {
+        const SectionManager = global.SectionManager;
+        const manager = new SectionManager();
+
+        let eventFired = false;
+        let eventData = null;
+
+        manager.on('test-event', (data) => {
+            eventFired = true;
+            eventData = data;
+        });
+
+        manager.emit('test-event', { test: 'data' });
+
+        runner.expect(eventFired).toBeTruthy();
+        runner.expect(eventData).toEqual({ test: 'data' });
+    });
+
+    runner.it('should preserve document status functionality', () => {
+        const SectionManager = global.SectionManager;
+        const manager = new SectionManager();
+
+        manager.createSectionsFromMarkdown('# Test\nContent');
+        const status = manager.getDocumentStatus();
+
+        runner.expect(status).toHaveProperty('totalSections');
+        runner.expect(status).toHaveProperty('editingSections');
+        runner.expect(status.totalSections).toBe(1);
+    });
+
+    runner.it('should preserve getAllSections functionality', () => {
+        const SectionManager = global.SectionManager;
+        const manager = new SectionManager();
+
+        const testMarkdown = '# One\nContent\n\n# Two\nMore content';
+        manager.createSectionsFromMarkdown(testMarkdown);
+
+        const allSections = manager.getAllSections();
+        runner.expect(Array.isArray(allSections)).toBeTruthy();
+        runner.expect(allSections.length).toBe(2);
+    });
+
+    runner.it('should preserve section splitting functionality', () => {
+        const SectionManager = global.SectionManager;
+        const manager = new SectionManager();
+
+        const sections = manager.createSectionsFromMarkdown('# Original\nContent');
+        const sectionId = sections[0].id;
+
+        const newContent = '# Split 1\nContent 1\n\n# Split 2\nContent 2';
+        const newSections = manager.handleSectionSplit(sectionId, newContent);
+
+        runner.expect(Array.isArray(newSections)).toBeTruthy();
+        runner.expect(newSections.length).toBe(2);
+        runner.expect(manager.sections.has(sectionId)).toBeFalsy(); // Original removed
+    });
+});
+
+// Export API tests for use during extraction
+const SECTION_MANAGER_API_TESTS = [
+    (SectionManager) => {
+        const manager = new SectionManager();
+        if (!manager.sections || !(manager.sections instanceof Map)) {
+            throw new Error('sections property missing or not a Map');
+        }
+    },
+    (SectionManager) => {
+        const manager = new SectionManager();
+        if (typeof manager.createSectionsFromMarkdown !== 'function') {
+            throw new Error('createSectionsFromMarkdown method missing');
+        }
+    },
+    (SectionManager) => {
+        const manager = new SectionManager();
+        if (typeof manager.startEditing !== 'function') {
+            throw new Error('startEditing method missing');
+        }
+    },
+    (SectionManager) => {
+        const manager = new SectionManager();
+        if (typeof manager.stopEditing !== 'function') {
+            throw new Error('stopEditing method missing');
+        }
+    }
+];
+
+module.exports = {
+    runner,
+    EXPECTED_SECTION_MANAGER_API,
+    SECTION_MANAGER_API_TESTS
+};
+
+// Run tests if called directly
+if (require.main === module) {
+    console.log('🧪 Testing SectionManager Component Extraction');
+    runner.run().then(() => {
+        console.log('✅ SectionManager extraction tests completed');
+    });
+}
\ No newline at end of file