Sandbox SDK: Document memory leak fixes

src/content/docs/sandbox/api/lifecycle.mdx

@@ -94,6 +94,18 @@ Containers automatically sleep after 10 minutes of inactivity but still count to
 
 ---
 
+## Automatic state cleanup
+
+When a sandbox container sleeps or restarts, the Durable Object automatically cleans up stale state to prevent memory leaks:
+
+- Port authentication tokens are cleared
+- Session references are reset
+- Mount metadata is removed
+
+This ensures that each container restart starts with a clean state. Your persistent data in the container filesystem remains intact across restarts.
+
+---
+
 ## Related resources
 
 - [Sandbox lifecycle concept](/sandbox/concepts/sandboxes/) - Understanding container lifecycle and state

src/content/docs/sandbox/concepts/containers.mdx

@@ -55,6 +55,16 @@ const process = await sandbox.startProcess('node server.js');
 // Returns immediately, process runs in background
 ```
 
+### Memory management
+
+The container runtime includes optimizations for long-running sandboxes with many processes:
+
+- **Active processes** are kept in memory for fast access
+- **Completed processes** are persisted to disk (`/tmp/sandbox-internal/processes/`) and freed from memory to prevent unbounded growth
+- **Stream listeners** are automatically cleaned up when streaming operations complete or are cancelled
+
+These optimizations ensure stable memory usage even for sandboxes that execute hundreds or thousands of processes over their lifetime. Process history remains queryable after completion via the standard process APIs.
+
 ## Network capabilities
 
 **Outbound connections** work: