fix #1563 (cdp): resolve page leaks and race conditions in concurrent crawling

Fix memory leaks and race conditions when using arun_many() with managed CDP browsers. Each crawl now gets proper page isolation with automatic cleanup while maintaining shared browser context.

Key fixes:
- Close non-session pages after crawling to prevent tab accumulation
- Add thread-safe page creation with locks to avoid concurrent access
- Improve page lifecycle management for managed vs non-managed browsers
- Keep session pages alive for authentication persistence
- Prevent TOCTOU (time-of-check-time-of-use) race conditions

This ensures stable parallel crawling without memory growth or browser instability.

crawl4ai/async_crawler_strategy.py

@@ -1047,14 +1047,28 @@ class AsyncPlaywrightCrawlerStrategy(AsyncCrawlerStrategy):
             raise e
 
         finally:
-            # If no session_id is given we should close the page
+            # Clean up page after crawl completes
+            # For managed CDP browsers, close pages that are not part of a session to prevent memory leaks
             all_contexts = page.context.browser.contexts
-            total_pages = sum(len(context.pages) for context in all_contexts)                
+            total_pages = sum(len(context.pages) for context in all_contexts)
+            
+            should_close_page = False
+            
             if config.session_id:
+                # Session pages are kept alive for reuse
                 pass
-            elif total_pages <= 1 and (self.browser_config.use_managed_browser or self.browser_config.headless):
+            elif self.browser_config.use_managed_browser:
+                # For managed browsers (CDP), close non-session pages to prevent tab accumulation
+                # This is especially important for arun_many() with multiple concurrent crawls
+                should_close_page = True
+            elif total_pages <= 1 and self.browser_config.headless:
+                # Keep the last page in headless mode to avoid closing the browser
                 pass
             else:
+                # For non-managed browsers, close the page
+                should_close_page = True
+            
+            if should_close_page:
                 # Detach listeners before closing to prevent potential errors during close
                 if config.capture_network_requests:
                     page.remove_listener("request", handle_request_capture)

crawl4ai/browser_manager.py

@@ -1035,34 +1035,20 @@ class BrowserManager:
             self.sessions[crawlerRunConfig.session_id] = (context, page, time.time())
             return page, context
 
-        # If using a managed browser, just grab the shared default_context
+        # If using a managed browser, reuse the default context and create new pages
         if self.config.use_managed_browser:
+            context = self.default_context
             if self.config.storage_state:
-                context = await self.create_browser_context(crawlerRunConfig)
+                # Clone runtime state from storage to the shared context
-                ctx = self.default_context        # default context, one window only
+                ctx = self.default_context
                 ctx = await clone_runtime_state(context, ctx, crawlerRunConfig, self.config)
-                # Avoid concurrent new_page on shared persistent context
+            
-                # See GH-1198: context.pages can be empty under races
+            # Always create a new page for concurrent safety
-                async with self._page_lock:
+            # The page-level isolation prevents race conditions while sharing the same context
-                    page = await ctx.new_page()
+            async with self._page_lock:
-                await self._apply_stealth_to_page(page)
+                page = await context.new_page()
-            else:
+            
-                context = self.default_context
+            await self._apply_stealth_to_page(page)
-                pages = context.pages
-                page = next((p for p in pages if p.url == crawlerRunConfig.url), None)
-                if not page:
-                    if pages:
-                        page = pages[0]
-                    else:
-                        # Double-check under lock to avoid TOCTOU and ensure only
-                        # one task calls new_page when pages=[] concurrently
-                        async with self._page_lock:
-                            pages = context.pages
-                            if pages:
-                                page = pages[0]
-                            else:
-                                page = await context.new_page()
-                                await self._apply_stealth_to_page(page)
         else:
             # Otherwise, check if we have an existing context for this config
             config_signature = self._make_config_signature(crawlerRunConfig)

docs/md_v2/advanced/cdp-browser-crawling.md

@@ -0,0 +1,594 @@
+# CDP Browser Crawling
+
+> **New in v0.7.6**: Efficient concurrent crawling with managed CDP (Chrome DevTools Protocol) browsers. Connect to a running browser instance and perform multiple crawls without spawning new windows.
+
+## 1. Overview
+
+When working with CDP browsers, you can connect to an existing browser instance instead of launching a new one for each crawl. This is particularly useful for:
+
+- **Development**: Keep your browser open with DevTools for debugging
+- **Persistent Sessions**: Maintain authentication across multiple crawls  
+- **Resource Efficiency**: Reuse a single browser instance for multiple operations
+- **Concurrent Crawling**: Run multiple crawls simultaneously with proper isolation
+
+**Key Benefits:**
+
+- ✅ Single browser window with multiple tabs (no window clutter)
+- ✅ Shared state (cookies, localStorage) across crawls
+- ✅ Concurrent safety with automatic page isolation
+- ✅ Automatic cleanup to prevent memory leaks
+- ✅ Works seamlessly with `arun_many()` for parallel crawling
+
+---
+
+## 2. Quick Start
+
+### 2.1 Starting a CDP Browser
+
+Use the Crawl4AI CLI to start a managed CDP browser:
+
+```bash
+# Start CDP browser on default port (9222)
+crwl cdp
+
+# Start on custom port
+crwl cdp -d 9223
+
+# Start in headless mode
+crwl cdp --headless
+```
+
+The browser will stay running until you press 'q' or close the terminal.
+
+### 2.2 Basic CDP Connection
+
+```python
+import asyncio
+from crawl4ai import AsyncWebCrawler, BrowserConfig, CrawlerRunConfig
+
+async def main():
+    # Configure CDP connection
+    browser_cfg = BrowserConfig(
+        browser_type="chromium",
+        cdp_url="http://localhost:9222",
+        verbose=True
+    )
+    
+    # Crawl a single URL
+    async with AsyncWebCrawler(config=browser_cfg) as crawler:
+        result = await crawler.arun(
+            url="https://example.com",
+            config=CrawlerRunConfig()
+        )
+        print(f"Success: {result.success}")
+        print(f"Content length: {len(result.markdown)}")
+
+if __name__ == "__main__":
+    asyncio.run(main())
+```
+
+---
+
+## 3. Concurrent Crawling with arun_many()
+
+The real power of CDP crawling shines with `arun_many()`. The browser manager automatically handles:
+
+- **Page Isolation**: Each crawl gets its own tab
+- **Context Sharing**: All tabs share cookies and localStorage
+- **Concurrent Safety**: Proper locking prevents race conditions
+- **Auto Cleanup**: Tabs are closed after crawling (except sessions)
+
+### 3.1 Basic Concurrent Crawling
+
+```python
+import asyncio
+from crawl4ai import AsyncWebCrawler, BrowserConfig, CrawlerRunConfig, CacheMode
+
+async def crawl_multiple_urls():
+    # URLs to crawl
+    urls = [
+        "https://example.com",
+        "https://httpbin.org/html",
+        "https://www.python.org",
+    ]
+    
+    # Configure CDP browser
+    browser_cfg = BrowserConfig(
+        browser_type="chromium",
+        cdp_url="http://localhost:9222",
+        verbose=False
+    )
+    
+    # Configure crawler (bypass cache for fresh data)
+    crawler_cfg = CrawlerRunConfig(
+        cache_mode=CacheMode.BYPASS
+    )
+    
+    # Crawl all URLs concurrently
+    async with AsyncWebCrawler(config=browser_cfg) as crawler:
+        results = await crawler.arun_many(
+            urls=urls,
+            config=crawler_cfg
+        )
+        
+        # Process results
+        for result in results:
+            print(f"\nURL: {result.url}")
+            if result.success:
+                print(f"✓ Success | Content length: {len(result.markdown)}")
+            else:
+                print(f"✗ Failed: {result.error_message}")
+
+if __name__ == "__main__":
+    asyncio.run(crawl_multiple_urls())
+```
+
+### 3.2 With Session Management
+
+Use sessions to maintain authentication and state across individual crawls:
+
+```python
+async def crawl_with_sessions():
+    browser_cfg = BrowserConfig(
+        browser_type="chromium",
+        cdp_url="http://localhost:9222"
+    )
+    
+    async with AsyncWebCrawler(config=browser_cfg) as crawler:
+        # First crawl: Login page
+        login_result = await crawler.arun(
+            url="https://example.com/login",
+            config=CrawlerRunConfig(
+                session_id="my-session",  # Session persists
+                js_code="document.querySelector('#login').click();"
+            )
+        )
+        
+        # Second crawl: Reuse authenticated session
+        dashboard_result = await crawler.arun(
+            url="https://example.com/dashboard",
+            config=CrawlerRunConfig(
+                session_id="my-session"  # Same session, cookies preserved
+            )
+        )
+```
+
+---
+
+## 4. How It Works
+
+### 4.1 Browser Context Reuse
+
+When using CDP browsers, Crawl4AI:
+
+1. **Connects** to the existing browser via CDP URL
+2. **Reuses** the default browser context (single window)
+3. **Creates** new pages (tabs) for each crawl
+4. **Locks** page creation to prevent concurrent races
+5. **Cleans up** pages after crawling (unless it's a session)
+
+```python
+# Internal behavior (simplified)
+if self.config.use_managed_browser:
+    context = self.default_context  # Shared context
+    
+    # Thread-safe page creation
+    async with self._page_lock:
+        page = await context.new_page()  # New tab per crawl
+    
+    # After crawl completes
+    if not config.session_id:
+        await page.close()  # Auto cleanup
+```
+
+### 4.2 Page Lifecycle
+
+```mermaid
+graph TD
+    A[Start Crawl] --> B{Has session_id?}
+    B -->|Yes| C[Reuse existing page]
+    B -->|No| D[Create new page/tab]
+    D --> E[Navigate & Extract]
+    C --> E
+    E --> F{Is session?}
+    F -->|Yes| G[Keep page open]
+    F -->|No| H[Close page]
+    H --> I[End]
+    G --> I
+```
+
+### 4.3 State Sharing
+
+All pages in the same context share:
+
+- 🍪 **Cookies**: Authentication tokens, preferences
+- 💾 **localStorage**: Client-side data storage
+- 🔐 **sessionStorage**: Per-tab session data
+- 🌐 **Network cache**: Shared HTTP cache
+
+This makes it perfect for crawling authenticated sites or maintaining state across multiple pages.
+
+---
+
+## 5. Configuration Options
+
+### 5.1 BrowserConfig for CDP
+
+```python
+browser_cfg = BrowserConfig(
+    browser_type="chromium",           # Must be "chromium" for CDP
+    cdp_url="http://localhost:9222",   # CDP endpoint URL
+    verbose=True,                      # Log browser operations
+    
+    # Optional: Override headers for all requests
+    headers={
+        "Accept-Language": "en-US,en;q=0.9",
+    },
+    
+    # Optional: Set user agent
+    user_agent="Mozilla/5.0 ...",
+    
+    # Optional: Enable stealth mode (requires dedicated browser)
+    # enable_stealth=False,  # Not compatible with CDP
+)
+```
+
+### 5.2 CrawlerRunConfig Options
+
+```python
+crawler_cfg = CrawlerRunConfig(
+    # Session management
+    session_id="my-session",           # Persist page across calls
+    
+    # Caching
+    cache_mode=CacheMode.BYPASS,       # Fresh data every time
+    
+    # Browser location (affects timezone, locale)
+    locale="en-US",
+    timezone_id="America/New_York",
+    geolocation={
+        "latitude": 40.7128,
+        "longitude": -74.0060
+    },
+    
+    # Proxy (per-crawl override)
+    proxy_config={
+        "server": "http://proxy.example.com:8080",
+        "username": "user",
+        "password": "pass"
+    }
+)
+```
+
+---
+
+## 6. Advanced Patterns
+
+### 6.1 Streaming Results
+
+Process URLs as they complete instead of waiting for all:
+
+```python
+async def stream_crawl_results():
+    browser_cfg = BrowserConfig(
+        browser_type="chromium",
+        cdp_url="http://localhost:9222"
+    )
+    
+    urls = ["https://example.com" for _ in range(100)]
+    
+    async with AsyncWebCrawler(config=browser_cfg) as crawler:
+        # Stream results as they complete
+        async for result in crawler.arun_many(
+            urls=urls,
+            config=CrawlerRunConfig(stream=True)
+        ):
+            if result.success:
+                print(f"✓ {result.url}: {len(result.markdown)} chars")
+                # Process immediately instead of waiting for all
+                await save_to_database(result)
+```
+
+### 6.2 Custom Concurrency Control
+
+```python
+from crawl4ai import CrawlerRunConfig
+
+# Limit concurrent crawls to 3
+crawler_cfg = CrawlerRunConfig(
+    semaphore_count=3,      # Max 3 concurrent requests
+    mean_delay=0.5,         # Average 0.5s delay between requests
+    max_range=1.0,          # +/- 1s random delay
+)
+
+async with AsyncWebCrawler(config=browser_cfg) as crawler:
+    results = await crawler.arun_many(urls, config=crawler_cfg)
+```
+
+### 6.3 Multi-Config Crawling
+
+Different configurations for different URL groups:
+
+```python
+from crawl4ai import CrawlerRunConfig
+
+# Fast crawl for static pages
+fast_config = CrawlerRunConfig(
+    wait_until="domcontentloaded",
+    page_timeout=30000
+)
+
+# Slow crawl for dynamic pages
+slow_config = CrawlerRunConfig(
+    wait_until="networkidle",
+    page_timeout=60000,
+    js_code="window.scrollTo(0, document.body.scrollHeight);"
+)
+
+configs = [fast_config, slow_config, fast_config]
+urls = ["https://static.com", "https://dynamic.com", "https://static2.com"]
+
+async with AsyncWebCrawler(config=browser_cfg) as crawler:
+    results = await crawler.arun_many(urls, configs=configs)
+```
+
+---
+
+## 7. Best Practices
+
+### 7.1 Resource Management
+
+✅ **DO:**
+```python
+# Use context manager for automatic cleanup
+async with AsyncWebCrawler(config=browser_cfg) as crawler:
+    results = await crawler.arun_many(urls)
+# Browser connection closed automatically
+```
+
+❌ **DON'T:**
+```python
+# Manual management risks resource leaks
+crawler = AsyncWebCrawler(config=browser_cfg)
+await crawler.start()
+results = await crawler.arun_many(urls)
+# Forgot to call crawler.close()!
+```
+
+### 7.2 Session Management
+
+✅ **DO:**
+```python
+# Use sessions for related crawls
+config = CrawlerRunConfig(session_id="user-flow")
+await crawler.arun(login_url, config=config)
+await crawler.arun(dashboard_url, config=config)
+await crawler.kill_session("user-flow")  # Clean up when done
+```
+
+❌ **DON'T:**
+```python
+# Creating new session IDs unnecessarily
+for i in range(100):
+    config = CrawlerRunConfig(session_id=f"session-{i}")
+    await crawler.arun(url, config=config)
+# 100 unclosed sessions accumulate!
+```
+
+### 7.3 Error Handling
+
+```python
+async def robust_crawl(urls):
+    browser_cfg = BrowserConfig(
+        browser_type="chromium",
+        cdp_url="http://localhost:9222"
+    )
+    
+    try:
+        async with AsyncWebCrawler(config=browser_cfg) as crawler:
+            results = await crawler.arun_many(urls)
+            
+            # Separate successes and failures
+            successes = [r for r in results if r.success]
+            failures = [r for r in results if not r.success]
+            
+            print(f"✓ {len(successes)} succeeded")
+            print(f"✗ {len(failures)} failed")
+            
+            # Retry failures with different config
+            if failures:
+                retry_urls = [r.url for r in failures]
+                retry_config = CrawlerRunConfig(
+                    page_timeout=120000,  # Longer timeout
+                    wait_until="networkidle"
+                )
+                retry_results = await crawler.arun_many(
+                    retry_urls, 
+                    config=retry_config
+                )
+                
+            return successes + retry_results
+            
+    except Exception as e:
+        print(f"Fatal error: {e}")
+        return []
+```
+
+---
+
+## 8. Troubleshooting
+
+### 8.1 Connection Issues
+
+**Problem**: `Cannot connect to CDP browser`
+
+```python
+# Check CDP browser is running
+$ lsof -i :9222
+# Should show: Chromium  PID USER   FD   TYPE  ...
+
+# Or start it if not running
+$ crwl cdp
+```
+
+**Problem**: `ERR_ABORTED` errors in concurrent crawls
+
+✅ **Fixed in v0.7.6**: This issue has been resolved. Pages are now properly isolated with locking.
+
+### 8.2 Performance Issues
+
+**Problem**: Too many open tabs
+
+```python
+# Ensure you're not using session_id for everything
+config = CrawlerRunConfig()  # No session_id
+await crawler.arun_many(urls, config=config)
+# Pages auto-close after crawling
+```
+
+**Problem**: Memory leaks
+
+```python
+# Always use context manager
+async with AsyncWebCrawler(config=browser_cfg) as crawler:
+    # Crawling code here
+    pass
+# Automatic cleanup on exit
+```
+
+### 8.3 State Issues
+
+**Problem**: Cookies not persisting
+
+```python
+# Use the same context (automatic with CDP)
+browser_cfg = BrowserConfig(cdp_url="http://localhost:9222")
+# All crawls share cookies automatically
+```
+
+**Problem**: Need isolated state
+
+```python
+# Use different CDP endpoints or non-CDP browsers
+browser_cfg_1 = BrowserConfig(cdp_url="http://localhost:9222")
+browser_cfg_2 = BrowserConfig(cdp_url="http://localhost:9223")
+# Completely isolated browsers
+```
+
+---
+
+## 9. Comparison: CDP vs Regular Browsers
+
+| Feature | CDP Browser | Regular Browser |
+|---------|-------------|-----------------|
+| **Window Management** | ✅ Single window, multiple tabs | ❌ New window per context |
+| **Startup Time** | ✅ Instant (already running) | ⏱️ ~2-3s per launch |
+| **State Sharing** | ✅ Shared cookies/localStorage | ⚠️ Isolated by default |
+| **Concurrent Safety** | ✅ Automatic locking | ✅ Separate processes |
+| **Memory Usage** | ✅ Lower (shared browser) | ⚠️ Higher (multiple processes) |
+| **Session Persistence** | ✅ Native support | ✅ Via session_id |
+| **Stealth Mode** | ❌ Not compatible | ✅ Full support |
+| **Best For** | Development, authenticated crawls | Production, isolated crawls |
+
+---
+
+## 10. Real-World Examples
+
+### 10.1 E-commerce Product Scraping
+
+```python
+async def scrape_products():
+    browser_cfg = BrowserConfig(
+        browser_type="chromium",
+        cdp_url="http://localhost:9222"
+    )
+    
+    # Get product URLs from category page
+    async with AsyncWebCrawler(config=browser_cfg) as crawler:
+        category_result = await crawler.arun(
+            url="https://shop.example.com/category",
+            config=CrawlerRunConfig(
+                css_selector=".product-link"
+            )
+        )
+        
+        # Extract product URLs
+        product_urls = extract_urls(category_result.links)
+        
+        # Crawl all products concurrently
+        product_results = await crawler.arun_many(
+            urls=product_urls,
+            config=CrawlerRunConfig(
+                css_selector=".product-details",
+                semaphore_count=5  # Polite crawling
+            )
+        )
+        
+        return [extract_product_data(r) for r in product_results]
+```
+
+### 10.2 News Article Monitoring
+
+```python
+import asyncio
+from datetime import datetime
+
+async def monitor_news_sites():
+    browser_cfg = BrowserConfig(
+        browser_type="chromium",
+        cdp_url="http://localhost:9222"
+    )
+    
+    news_sites = [
+        "https://news.site1.com",
+        "https://news.site2.com",
+        "https://news.site3.com"
+    ]
+    
+    async with AsyncWebCrawler(config=browser_cfg) as crawler:
+        while True:
+            print(f"\n[{datetime.now()}] Checking for updates...")
+            
+            results = await crawler.arun_many(
+                urls=news_sites,
+                config=CrawlerRunConfig(
+                    cache_mode=CacheMode.BYPASS,  # Always fresh
+                    css_selector=".article-headline"
+                )
+            )
+            
+            for result in results:
+                if result.success:
+                    headlines = extract_headlines(result)
+                    for headline in headlines:
+                        if is_new(headline):
+                            notify_user(headline)
+            
+            # Check every 5 minutes
+            await asyncio.sleep(300)
+```
+
+---
+
+## 11. Summary
+
+CDP browser crawling offers:
+
+- 🚀 **Performance**: Faster startup, lower resource usage
+- 🔄 **State Management**: Shared cookies and authentication
+- 🎯 **Concurrent Safety**: Automatic page isolation and cleanup
+- 💻 **Developer Friendly**: Visual debugging with DevTools
+
+**When to use CDP:**
+- Development and debugging
+- Authenticated crawling (login required)
+- Sequential crawls needing state
+- Resource-constrained environments
+
+**When to use regular browsers:**
+- Production deployments
+- Maximum isolation required  
+- Stealth mode needed
+- Distributed/cloud crawling
+
+For most use cases, **CDP browsers provide the best balance** of performance, convenience, and safety.

tests/test_arun_many_cdp.py

@@ -0,0 +1,63 @@
+"""
+Test for arun_many with managed CDP browser to ensure each crawl gets its own tab.
+"""
+import pytest
+import asyncio
+from crawl4ai import AsyncWebCrawler, BrowserConfig, CrawlerRunConfig, CacheMode
+
+
+@pytest.mark.asyncio
+async def test_arun_many_with_cdp():
+    """Test arun_many opens a new tab for each url with managed CDP browser."""
+    # NOTE: Requires a running CDP browser at localhost:9222
+    # Can be started with: crwl cdp -d 9222
+    browser_cfg = BrowserConfig(
+        browser_type="cdp",
+        cdp_url="http://localhost:9222",
+        verbose=False,
+    )
+    urls = [
+        "https://example.com",
+        "https://httpbin.org/html",
+        "https://www.python.org",
+    ]
+    crawler_cfg = CrawlerRunConfig(
+        cache_mode=CacheMode.BYPASS,
+    )
+    async with AsyncWebCrawler(config=browser_cfg) as crawler:
+        results = await crawler.arun_many(urls=urls, config=crawler_cfg)
+        # All results should be successful and distinct
+        assert len(results) == 3
+        for result in results:
+            assert result.success, f"Crawl failed: {result.url} - {result.error_message}"
+            assert result.markdown is not None
+
+
+@pytest.mark.asyncio
+async def test_arun_many_with_cdp_sequential():
+    """Test arun_many sequentially to isolate issues."""
+    browser_cfg = BrowserConfig(
+        browser_type="cdp",
+        cdp_url="http://localhost:9222",
+        verbose=True,
+    )
+    urls = [
+        "https://example.com",
+        "https://httpbin.org/html", 
+        "https://www.python.org",
+    ]
+    crawler_cfg = CrawlerRunConfig(
+        cache_mode=CacheMode.BYPASS,
+    )
+    async with AsyncWebCrawler(config=browser_cfg) as crawler:
+        results = []
+        for url in urls:
+            result = await crawler.arun(url=url, config=crawler_cfg)
+            results.append(result)
+            assert result.success, f"Crawl failed: {result.url} - {result.error_message}"
+            assert result.markdown is not None
+        assert len(results) == 3
+
+
+if __name__ == "__main__":
+    asyncio.run(test_arun_many_with_cdp())