fix(orchestrator): resolve high-priority issues from code review

1. Race condition fix: Removed frontend direct lockSession call in
   useOrchestratorExecution.ts - session locking now handled purely
   via backend WebSocket broadcast (CLI_SESSION_LOCKED)

2. WebSocket handlers: Added handleSessionLockedMessage and
   handleSessionUnlockedMessage to sessionManagerStore.ts

3. useWebSocket integration: Added case handlers for
   CLI_SESSION_LOCKED and CLI_SESSION_UNLOCKED messages

4. API input validation: Added validation for sessionConfig,
   stepTimeout, and errorStrategy in execute-in-session endpoint

5. Fixed wsBroadcast reference: Changed to broadcastToClients
   from context

ccw/frontend/src/hooks/useWebSocket.ts

@@ -9,6 +9,10 @@ import { useExecutionStore } from '@/stores/executionStore';
 import { useFlowStore } from '@/stores';
 import { useCliStreamStore } from '@/stores/cliStreamStore';
 import { useCliSessionStore } from '@/stores/cliSessionStore';
+import {
+  handleSessionLockedMessage,
+  handleSessionUnlockedMessage,
+} from '@/stores/sessionManagerStore';
 import {
   OrchestratorMessageSchema,
   type OrchestratorWebSocketMessage,
@@ -212,6 +216,30 @@ export function useWebSocket(options: UseWebSocketOptions = {}): UseWebSocketRet
               break;
             }
 
+            case 'CLI_SESSION_LOCKED': {
+              const { sessionKey, reason, executionId, timestamp } = data.payload ?? {};
+              if (typeof sessionKey === 'string') {
+                handleSessionLockedMessage({
+                  sessionKey,
+                  reason: reason ?? 'Workflow execution',
+                  executionId,
+                  timestamp: timestamp ?? new Date().toISOString(),
+                });
+              }
+              break;
+            }
+
+            case 'CLI_SESSION_UNLOCKED': {
+              const { sessionKey, timestamp } = data.payload ?? {};
+              if (typeof sessionKey === 'string') {
+                handleSessionUnlockedMessage({
+                  sessionKey,
+                  timestamp: timestamp ?? new Date().toISOString(),
+                });
+              }
+              break;
+            }
+
             case 'CLI_OUTPUT': {
               const { executionId, chunkType, data: outputData, unit } = data.payload;
 

ccw/frontend/src/stores/sessionManagerStore.ts

@@ -35,6 +35,50 @@ const initialState: SessionManagerState = {
 /** Module-level worker reference. Worker objects are not serializable. */
 let _workerRef: Worker | null = null;
 
+// ========== WebSocket Session Lock Message Handler ==========
+
+/**
+ * Handle CLI_SESSION_LOCKED WebSocket message from backend.
+ * Updates session metadata to reflect locked state.
+ */
+export function handleSessionLockedMessage(payload: {
+  sessionKey: string;
+  reason: string;
+  executionId?: string;
+  timestamp: string;
+}): void {
+  const store = useSessionManagerStore.getState();
+  store.updateTerminalMeta(payload.sessionKey, {
+    status: 'locked',
+    isLocked: true,
+    lockReason: payload.reason,
+    lockedByExecutionId: payload.executionId,
+    lockedAt: payload.timestamp,
+  });
+}
+
+/**
+ * Handle CLI_SESSION_UNLOCKED WebSocket message from backend.
+ * Updates session metadata to reflect unlocked state.
+ */
+export function handleSessionUnlockedMessage(payload: {
+  sessionKey: string;
+  timestamp: string;
+}): void {
+  const store = useSessionManagerStore.getState();
+  const existing = store.terminalMetas[payload.sessionKey];
+  // Only unlock if currently locked
+  if (existing?.isLocked) {
+    store.updateTerminalMeta(payload.sessionKey, {
+      status: 'active',
+      isLocked: false,
+      lockReason: undefined,
+      lockedByExecutionId: undefined,
+      lockedAt: undefined,
+    });
+  }
+}
+
 // ========== Worker Message Handler ==========
 
 function _handleWorkerMessage(event: MessageEvent<MonitorAlert>): void {

ccw/src/core/routes/orchestrator-routes.ts

@@ -1307,6 +1307,37 @@ export async function handleOrchestratorRoutes(ctx: RouteContext): Promise<boole
         errorStrategy?: 'pause' | 'skip' | 'stop';
       };
 
+      // Input validation
+      const validTools = ['claude', 'gemini', 'qwen', 'codex', 'opencode'];
+      const validShells = ['bash', 'pwsh', 'cmd'];
+      const validErrorStrategies = ['pause', 'skip', 'stop'];
+
+      if (sessionConfig) {
+        if (sessionConfig.tool && !validTools.includes(sessionConfig.tool)) {
+          return { success: false, error: `Invalid tool. Must be one of: ${validTools.join(', ')}`, status: 400 };
+        }
+        if (sessionConfig.preferredShell && !validShells.includes(sessionConfig.preferredShell)) {
+          return { success: false, error: `Invalid preferredShell. Must be one of: ${validShells.join(', ')}`, status: 400 };
+        }
+        if (sessionConfig.model && typeof sessionConfig.model !== 'string') {
+          return { success: false, error: 'model must be a string', status: 400 };
+        }
+      }
+
+      if (inputVariables && typeof inputVariables !== 'object') {
+        return { success: false, error: 'variables must be an object', status: 400 };
+      }
+
+      if (stepTimeout !== undefined) {
+        if (typeof stepTimeout !== 'number' || stepTimeout < 1000 || stepTimeout > 3600000) {
+          return { success: false, error: 'stepTimeout must be a number between 1000 and 3600000 (ms)', status: 400 };
+        }
+      }
+
+      if (!validErrorStrategies.includes(errorStrategy)) {
+        return { success: false, error: `Invalid errorStrategy. Must be one of: ${validErrorStrategies.join(', ')}`, status: 400 };
+      }
+
       try {
         // Verify flow exists
         const flow = await readFlowStorage(workflowDir, flowId);
@@ -1355,31 +1386,27 @@ export async function handleOrchestratorRoutes(ctx: RouteContext): Promise<boole
         broadcastExecutionStateUpdate(execution);
 
         // Broadcast EXECUTION_STARTED to WebSocket clients
-        if (wsBroadcast) {
-          wsBroadcast({
-            type: 'EXECUTION_STARTED',
-            payload: {
-              executionId: execId,
-              flowId: flowId,
-              sessionKey: sessionKey,
-              stepName: flow.name,
-              timestamp: now
-            }
-          });
-        }
+        broadcastToClients({
+          type: 'EXECUTION_STARTED',
+          payload: {
+            executionId: execId,
+            flowId: flowId,
+            sessionKey: sessionKey,
+            stepName: flow.name,
+            timestamp: now
+          }
+        });
 
         // Lock the session (via WebSocket broadcast for frontend to handle)
-        if (wsBroadcast) {
-          wsBroadcast({
-            type: 'CLI_SESSION_LOCKED',
-            payload: {
-              sessionKey: sessionKey,
-              reason: `Executing workflow: ${flow.name}`,
-              executionId: execId,
-              timestamp: now
-            }
-          });
-        }
+        broadcastToClients({
+          type: 'CLI_SESSION_LOCKED',
+          payload: {
+            sessionKey: sessionKey,
+            reason: `Executing workflow: ${flow.name}`,
+            executionId: execId,
+            timestamp: now
+          }
+        });
 
         // TODO: Implement actual step-by-step execution in PTY session
         // For now, mark as running and let the frontend handle the orchestration