Add Delegation Support in Create Hook for Agent Routing

- Introduced delegation functionality in the Create hook, allowing agents to route requests to sub-agents without invoking LLM processing.
- Updated the HookCreateResponse structure to include a Delegate field, enabling immediate delegation to another agent.
- Enhanced the Stream method to handle delegation responses, ensuring proper stream closure and error handling for delegated agents.
- Improved logging for delegation actions to facilitate debugging and traceability in agent interactions.

agent/assistant/agent.go

@@ -169,6 +169,36 @@ func (ast *Assistant) Stream(ctx *context.Context, inputMessages []context.Messa
 		// Log the create response
 		ast.traceCreateHook(agentNode, createResponse)
 		ctx.Logger.HookComplete("Create")
+
+		// Check if Create hook wants to delegate to another agent
+		// This allows early routing to sub-agents without LLM call
+		if createResponse != nil && createResponse.Delegate != nil {
+			ctx.Logger.Debug("Create hook delegating to agent: %s", createResponse.Delegate.AgentID)
+
+			// Delegate to target agent (reuse existing delegation logic from next.go)
+			delegateResponse, err := ast.handleDelegation(ctx, createResponse.Delegate, streamHandler)
+			if err != nil {
+				finalStatus = context.ResumeStatusFailed
+				finalError = err
+				ast.traceAgentFail(agentNode, err)
+				ast.sendStreamEndOnError(ctx, streamHandler, streamStartTime, err)
+				return nil, err
+			}
+
+			// For root stack, send stream_end and close output
+			// (delegated agent handles its own stream events, but root needs to close)
+			if ctx.Stack != nil && ctx.Stack.IsRoot() {
+				ast.sendAgentStreamEnd(ctx, streamHandler, streamStartTime, "completed", nil, nil)
+				if err := ctx.CloseOutput(); err != nil {
+					if trace, _ := ctx.Trace(); trace != nil {
+						trace.Error(i18n.Tr(ast.ID, ctx.Locale, "assistant.agent.stream.close_error"), map[string]any{"error": err.Error()})
+					}
+				}
+			}
+
+			// Return delegated response directly (skip LLM call and Next hook)
+			return delegateResponse, nil
+		}
 	}
 
 	// ================================================

agent/context/types.go

@@ -391,6 +391,10 @@ type HookCreateResponse struct {
 	// - SearchIntent: fine-grained control with specific types, confidence, etc.
 	// - nil: use default behavior (determined by __yao.needsearch agent)
 	Search any `json:"search,omitempty"` // Search mode: bool | SearchIntent | nil
+
+	// Delegate: if provided, delegate to another agent immediately (skip LLM call)
+	// This allows Create hook to route to sub-agents before any LLM processing
+	Delegate *DelegateConfig `json:"delegate,omitempty"`
 }
 
 // NextHookPayload payload for the next hook