feat: add runtime architecture diagram and flow summary to README

README.md

@@ -131,6 +131,70 @@ make ci
 
 ---
 
+# Laminar Runtime Architecture Diagram
+
+```mermaid
+flowchart TD
+
+    A["Arc&lt;RwLock&lt;AppState&gt;&gt;<br/><br/>Global shared runtime container"]
+
+    A --> B["AppState<br/><br/>Fields:<br/>- upstreams"]
+
+    B --> C["UpstreamPool<br/><br/>Fields:<br/>- id<br/>- current_index<br/>- backends"]
+
+    C --> D["AtomicUsize<br/><br/>Round robin index"]
+
+    C --> E["Vec Arc BackendState<br/><br/>Shared backend objects"]
+
+    E --> F["Arc BackendState<br/><br/>Reference counted backend state"]
+
+    F --> G["BackendState<br/><br/>Fields:<br/>- config<br/>- healthy<br/>- active_connections<br/>- failed_health_checks"]
+
+    G --> H["BackendServerConfig<br/><br/>Static backend configuration"]
+
+    G --> I["AtomicBool healthy<br/><br/>Backend health state"]
+
+    G --> J["AtomicUsize active_connections<br/><br/>Tracks active connections"]
+
+    K["TCP Proxy Task<br/><br/>Accepts client connections"]
+
+    K --> L["next_backend<br/><br/>Selects healthy backend"]
+
+    L --> F
+
+    K --> M["ConnectionGuard new<br/><br/>Starts connection tracking"]
+
+    M --> N["ConnectionGuard<br/><br/>Owns backend Arc"]
+
+    N --> J
+
+    N --> O["Drop implementation<br/><br/>Decrements connection count"]
+
+    P["Background Health Checker Task"]
+
+    P --> Q["check_backend_status<br/><br/>TCP health probe"]
+
+    Q --> I
+
+    R["Future Systems<br/><br/>Metrics<br/>Retries<br/>Least connections"]
+
+    R --> F
+```
+
+# Runtime Flow Summary
+
+1. Client connects to Laminar TCP proxy.
+2. Proxy task accesses shared AppState.
+3. next_backend() selects a healthy backend.
+4. Backend Arc is cloned and moved into ConnectionGuard.
+5. ConnectionGuard increments active_connections.
+6. TCP traffic is proxied between client and backend.
+7. When connection ends, ConnectionGuard drops automatically.
+8. active_connections is decremented safely.
+9. Background health checker continuously updates backend health state.
+
+---
+
 # CI Policy
 
 All pull requests must pass CI before merging.

src/proxy/tcp.rs

@@ -18,7 +18,7 @@ pub async fn start_tcp_proxy(address: &str, state: SharedAppState) -> anyhow::Re
 
         info!("new client connected {}", client_address);
         let state = state.clone();
-
+        // Arc<RwLock<AppState>> means SharedAppState only
         tokio::spawn(async move {
             if let Err(error) = handle_connection(client_stream, state).await {
                 error!("connection handling failed {:?}", error)
@@ -32,7 +32,7 @@ async fn handle_connection(mut stream: TcpStream, state: SharedAppState) -> anyh
         let state = state.read().await;
         let upstream = &state.upstreams[0];
         let backend_arc = match upstream.next_backend() {
-            Some(backend) => backend.clone(),
+            Some(backend) => backend,
             None => {
                 error!("no healthy backend available");
                 return Ok(());