diff --git a/setup/register.test.ts b/setup/register.test.ts
index d47d95c..5a70740 100644
--- a/setup/register.test.ts
+++ b/setup/register.test.ts
@@ -1,4 +1,7 @@
-import { describe, it, expect, beforeEach } from 'vitest';
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
+import { afterEach, describe, it, expect, beforeEach } from 'vitest';
 
 import Database from 'better-sqlite3';
 
@@ -6,7 +9,7 @@ import Database from 'better-sqlite3';
  * Tests for the register step.
  *
  * Verifies: parameterized SQL (no injection), file templating,
- * apostrophe in names, .env updates.
+ * apostrophe in names, .env updates, CLAUDE.md template copy.
  */
 
 function createTestDb(): Database.Database {
@@ -255,3 +258,207 @@ describe('file templating', () => {
     expect(envContent).toContain('ASSISTANT_NAME="Nova"');
   });
 });
+
+describe('CLAUDE.md template copy', () => {
+  let tmpDir: string;
+  let groupsDir: string;
+
+  // Replicates register.ts template copy + name update logic
+  function simulateRegister(
+    folder: string,
+    isMain: boolean,
+    assistantName = 'Andy',
+  ): void {
+    const folderDir = path.join(groupsDir, folder);
+    fs.mkdirSync(path.join(folderDir, 'logs'), { recursive: true });
+
+    // Template copy — never overwrite existing (register.ts lines 119-135)
+    const dest = path.join(folderDir, 'CLAUDE.md');
+    if (!fs.existsSync(dest)) {
+      const templatePath = isMain
+        ? path.join(groupsDir, 'main', 'CLAUDE.md')
+        : path.join(groupsDir, 'global', 'CLAUDE.md');
+      if (fs.existsSync(templatePath)) {
+        fs.copyFileSync(templatePath, dest);
+      }
+    }
+
+    // Name update across all groups (register.ts lines 140-165)
+    if (assistantName !== 'Andy') {
+      const mdFiles = fs
+        .readdirSync(groupsDir)
+        .map((d) => path.join(groupsDir, d, 'CLAUDE.md'))
+        .filter((f) => fs.existsSync(f));
+
+      for (const mdFile of mdFiles) {
+        let content = fs.readFileSync(mdFile, 'utf-8');
+        content = content.replace(/^# Andy$/m, `# ${assistantName}`);
+        content = content.replace(
+          /You are Andy/g,
+          `You are ${assistantName}`,
+        );
+        fs.writeFileSync(mdFile, content);
+      }
+    }
+  }
+
+  function readGroupMd(folder: string): string {
+    return fs.readFileSync(
+      path.join(groupsDir, folder, 'CLAUDE.md'),
+      'utf-8',
+    );
+  }
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'nanoclaw-register-test-'));
+    groupsDir = path.join(tmpDir, 'groups');
+    fs.mkdirSync(path.join(groupsDir, 'main'), { recursive: true });
+    fs.mkdirSync(path.join(groupsDir, 'global'), { recursive: true });
+    fs.writeFileSync(
+      path.join(groupsDir, 'main', 'CLAUDE.md'),
+      '# Andy\n\nYou are Andy, a personal assistant.\n\n## Admin Context\n\nThis is the **main channel**.',
+    );
+    fs.writeFileSync(
+      path.join(groupsDir, 'global', 'CLAUDE.md'),
+      '# Andy\n\nYou are Andy, a personal assistant.',
+    );
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it('copies global template for non-main group', () => {
+    simulateRegister('telegram_dev-team', false);
+
+    const content = readGroupMd('telegram_dev-team');
+    expect(content).toContain('You are Andy');
+    expect(content).not.toContain('Admin Context');
+  });
+
+  it('copies main template for main group', () => {
+    simulateRegister('whatsapp_main', true);
+
+    expect(readGroupMd('whatsapp_main')).toContain('Admin Context');
+  });
+
+  it('each channel can have its own main with admin context', () => {
+    simulateRegister('whatsapp_main', true);
+    simulateRegister('telegram_main', true);
+    simulateRegister('slack_main', true);
+    simulateRegister('discord_main', true);
+
+    for (const folder of [
+      'whatsapp_main',
+      'telegram_main',
+      'slack_main',
+      'discord_main',
+    ]) {
+      const content = readGroupMd(folder);
+      expect(content).toContain('Admin Context');
+      expect(content).toContain('You are Andy');
+    }
+  });
+
+  it('non-main groups across channels get global template', () => {
+    simulateRegister('whatsapp_main', true);
+    simulateRegister('telegram_friends', false);
+    simulateRegister('slack_engineering', false);
+    simulateRegister('discord_general', false);
+
+    expect(readGroupMd('whatsapp_main')).toContain('Admin Context');
+    for (const folder of [
+      'telegram_friends',
+      'slack_engineering',
+      'discord_general',
+    ]) {
+      const content = readGroupMd(folder);
+      expect(content).toContain('You are Andy');
+      expect(content).not.toContain('Admin Context');
+    }
+  });
+
+  it('custom name propagates to all channels and groups', () => {
+    // Register multiple channels, last one sets custom name
+    simulateRegister('whatsapp_main', true);
+    simulateRegister('telegram_main', true);
+    simulateRegister('slack_devs', false);
+    // Final registration triggers name update across all
+    simulateRegister('discord_main', true, 'Luna');
+
+    for (const folder of [
+      'main',
+      'global',
+      'whatsapp_main',
+      'telegram_main',
+      'slack_devs',
+      'discord_main',
+    ]) {
+      const content = readGroupMd(folder);
+      expect(content).toContain('# Luna');
+      expect(content).toContain('You are Luna');
+      expect(content).not.toContain('Andy');
+    }
+  });
+
+  it('never overwrites existing CLAUDE.md on re-registration', () => {
+    simulateRegister('slack_main', true);
+    // User customizes the file extensively (persona, workspace, rules)
+    const mdPath = path.join(groupsDir, 'slack_main', 'CLAUDE.md');
+    fs.writeFileSync(
+      mdPath,
+      '# Gambi\n\nCustom persona with workspace rules and family context.',
+    );
+    // Re-registering same folder (e.g. re-running /add-slack)
+    simulateRegister('slack_main', true);
+
+    const content = readGroupMd('slack_main');
+    expect(content).toContain('Custom persona');
+    expect(content).not.toContain('Admin Context');
+  });
+
+  it('never overwrites when non-main becomes main (isMain changes)', () => {
+    // User registers a family group as non-main
+    simulateRegister('whatsapp_casa', false);
+    // User extensively customizes it (PARA system, task management, etc.)
+    const mdPath = path.join(groupsDir, 'whatsapp_casa', 'CLAUDE.md');
+    fs.writeFileSync(
+      mdPath,
+      '# Casa\n\nFamily group with PARA system, task management, shopping lists.',
+    );
+    // Later, user promotes to main (no trigger required) — CLAUDE.md must be preserved
+    simulateRegister('whatsapp_casa', true);
+
+    const content = readGroupMd('whatsapp_casa');
+    expect(content).toContain('PARA system');
+    expect(content).not.toContain('Admin Context');
+  });
+
+  it('preserves custom CLAUDE.md across channels when changing main', () => {
+    // Real-world scenario: WhatsApp main + customized Discord research channel
+    simulateRegister('whatsapp_main', true);
+    simulateRegister('discord_main', false);
+    const discordPath = path.join(groupsDir, 'discord_main', 'CLAUDE.md');
+    fs.writeFileSync(
+      discordPath,
+      '# Gambi HQ — Research Assistant\n\nResearch workflows for Laura and Ethan.',
+    );
+
+    // Discord becomes main too — custom content must survive
+    simulateRegister('discord_main', true);
+    expect(readGroupMd('discord_main')).toContain('Research Assistant');
+    // WhatsApp main also untouched
+    expect(readGroupMd('whatsapp_main')).toContain('Admin Context');
+  });
+
+  it('handles missing templates gracefully', () => {
+    fs.unlinkSync(path.join(groupsDir, 'global', 'CLAUDE.md'));
+    fs.unlinkSync(path.join(groupsDir, 'main', 'CLAUDE.md'));
+
+    simulateRegister('discord_general', false);
+
+    expect(
+      fs.existsSync(path.join(groupsDir, 'discord_general', 'CLAUDE.md')),
+    ).toBe(false);
+  });
+});
diff --git a/setup/register.ts b/setup/register.ts
index eeafa90..c08d910 100644
--- a/setup/register.ts
+++ b/setup/register.ts
@@ -116,6 +116,30 @@ export async function run(args: string[]): Promise<void> {
     recursive: true,
   });
 
+  // Create CLAUDE.md in the new group folder from template if it doesn't exist.
+  // The agent runs with CWD=/workspace/group and loads CLAUDE.md from there.
+  // Never overwrite an existing CLAUDE.md — users customize these extensively
+  // (persona, workspace structure, communication rules, family context, etc.)
+  // and a stock template replacement would destroy that work.
+  const groupClaudeMdPath = path.join(
+    projectRoot,
+    'groups',
+    parsed.folder,
+    'CLAUDE.md',
+  );
+  if (!fs.existsSync(groupClaudeMdPath)) {
+    const templatePath = parsed.isMain
+      ? path.join(projectRoot, 'groups', 'main', 'CLAUDE.md')
+      : path.join(projectRoot, 'groups', 'global', 'CLAUDE.md');
+    if (fs.existsSync(templatePath)) {
+      fs.copyFileSync(templatePath, groupClaudeMdPath);
+      logger.info(
+        { file: groupClaudeMdPath, template: templatePath },
+        'Created CLAUDE.md from template',
+      );
+    }
+  }
+
   // Update assistant name in CLAUDE.md files if different from default
   let nameUpdated = false;
   if (parsed.assistantName !== 'Andy') {
@@ -124,10 +148,11 @@ export async function run(args: string[]): Promise<void> {
       'Updating assistant name',
     );
 
-    const mdFiles = [
-      path.join(projectRoot, 'groups', 'global', 'CLAUDE.md'),
-      path.join(projectRoot, 'groups', parsed.folder, 'CLAUDE.md'),
-    ];
+    const groupsDir = path.join(projectRoot, 'groups');
+    const mdFiles = fs
+      .readdirSync(groupsDir)
+      .map((d) => path.join(groupsDir, d, 'CLAUDE.md'))
+      .filter((f) => fs.existsSync(f));
 
     for (const mdFile of mdFiles) {
       if (fs.existsSync(mdFile)) {