fix: backup existing hook before overwriting during install

src/cli.ts

@@ -99,7 +99,7 @@ async function runInstallCommand(options: { force?: boolean; silent?: boolean })
   }
 
   // Install
-  const result = await install({ silent: options.silent });
+  const result = await install({ silent: options.silent, force: options.force });
 
   if (!result.success) {
     logger.blank();

src/install.ts

@@ -4,8 +4,8 @@
 
 import fs from 'fs/promises';
 import { Logger } from './utils/logger.js';
-import { getConfig, toGitPath } from './utils/paths.js';
-import { createHookInstallPlan } from './utils/hook.js';
+import { getConfig, toGitPath, pathExists } from './utils/paths.js';
+import { createHookInstallPlan, isNococliHook } from './utils/hook.js';
 import { getTemplateDir, setTemplateDir } from './utils/git.js';
 import { detectPowerShellRuntime } from './utils/runtime.js';
 import type { InstallOptions } from './types.js';
@@ -44,6 +44,20 @@ export async function install(options: InstallOptions = {}): Promise<InstallResu
       powerShellCommand: powerShellRuntime ?? undefined,
     });
 
+    // Backup existing hooks that are not from nococli
+    if (!options.force) {
+      for (const file of installPlan.files) {
+        if (await pathExists(file.path)) {
+          const existingContent = await fs.readFile(file.path, 'utf8');
+          if (!isNococliHook(existingContent)) {
+            const backupPath = `${file.path}.bak`;
+            await fs.copyFile(file.path, backupPath);
+            logger.warning(`Existing hook backed up to ${backupPath}`);
+          }
+        }
+      }
+    }
+
     for (const file of installPlan.files) {
       await fs.writeFile(file.path, file.content, {
         mode: file.mode,

src/uninstall.ts

@@ -4,7 +4,7 @@
 
 import fs from 'fs/promises';
 import { Logger } from './utils/logger.js';
-import { getConfig } from './utils/paths.js';
+import { getConfig, pathExists } from './utils/paths.js';
 import { unsetGitConfig } from './utils/git.js';
 import type { UninstallOptions } from './types.js';
 import type { HookMode } from './types.js';
@@ -39,6 +39,15 @@ export async function uninstall(options: UninstallOptions = {}): Promise<Uninsta
       logger.info('PowerShell hook file not found (already removed?)');
     }
 
+    // Restore backups if they exist
+    for (const hookPath of [config.hookFile, config.powerShellHookFile]) {
+      const backupPath = `${hookPath}.bak`;
+      if (await pathExists(backupPath)) {
+        await fs.rename(backupPath, hookPath);
+        logger.success(`Restored previous hook from ${backupPath}`);
+      }
+    }
+
     try {
       const hooksExists = await fs
         .access(config.hooksDir)

src/utils/hook.ts

@@ -220,6 +220,19 @@ export function createHookInstallPlan(options: HookInstallPlanOptions): HookInst
   };
 }
 
+/**
+ * Markers used to identify a nococli-generated hook file.
+ * Covers both Node.js (//) and PowerShell (#) comment styles.
+ */
+export const NOCO_HOOK_MARKERS = ['Generated by noco', 'nococli:'] as const;
+
+/**
+ * Check if hook content was generated by nococli.
+ */
+export function isNococliHook(content: string): boolean {
+  return NOCO_HOOK_MARKERS.some((marker) => content.includes(marker));
+}
+
 /**
  * Get list of default AI patterns
  */