feat(core): add standardized lifecycle debug logging for agents

packages/core/src/agents/agent-factory.ts

@@ -8,6 +8,7 @@ import { type Config } from '../config/config.js';
 import { AgentHarness, type AgentHarnessOptions } from './harness.js';
 import { type AgentDefinition, type LocalAgentDefinition } from './types.js';
 import { MainAgentBehavior, SubagentBehavior } from './behavior.js';
+import { debugLogger } from '../utils/debugLogger.js';
 
 /**
  * Factory for creating agent executors/harnesses.
@@ -32,6 +33,10 @@ export class AgentFactory {
       behavior = new MainAgentBehavior(config, options.parentPromptId);
     }
 
+    debugLogger.debug(
+      `[AgentFactory] Creating harness for agent: ${behavior.name} (agentId: ${behavior.agentId})`,
+    );
+
     return new AgentHarness({
       config,
       behavior,

packages/core/src/agents/behavior.ts

@@ -38,6 +38,7 @@ import { promptIdContext } from '../utils/promptIdContext.js';
 import { logRecoveryAttempt } from '../telemetry/loggers.js';
 import { RecoveryAttemptEvent } from '../telemetry/types.js';
 import { DeadlineTimer } from '../utils/deadlineTimer.js';
+import { debugLogger } from '../utils/debugLogger.js';
 
 import type { ToolRegistry } from '../tools/tool-registry.js';
 
@@ -158,7 +159,11 @@ export class MainAgentBehavior implements AgentBehavior {
     this.agentId = `${parentPrefix}main-${randomIdPart}`;
   }
 
-  async initialize(_toolRegistry: ToolRegistry) {}
+  async initialize(_toolRegistry: ToolRegistry) {
+    debugLogger.debug(
+      `[MainAgentBehavior] [${this.name}:${this.agentId}] Initialized`,
+    );
+  }
 
   async getSystemInstruction() {
     const systemMemory = this.config.getUserMemory();
@@ -340,6 +345,9 @@ export class SubagentBehavior implements AgentBehavior {
   }
 
   async initialize(toolRegistry: ToolRegistry) {
+    debugLogger.debug(
+      `[SubagentBehavior] [${this.name}:${this.agentId}] Initializing tool registry`,
+    );
     const parentToolRegistry = this.config.getToolRegistry();
     if (this.definition.toolConfig) {
       for (const toolRef of this.definition.toolConfig.tools) {
@@ -479,6 +487,9 @@ export class SubagentBehavior implements AgentBehavior {
     reason: AgentTerminateMode,
     signal: AbortSignal,
   ): AsyncGenerator<ServerGeminiStreamEvent, boolean> {
+    debugLogger.debug(
+      `[SubagentBehavior] [${this.name}:${this.agentId}] Entering recovery mode. Reason: ${reason}`,
+    );
     const recoveryStartTime = Date.now();
     let success = false;
     const graceTimeoutController = new DeadlineTimer(

packages/core/src/agents/harness.ts

@@ -125,7 +125,7 @@ export class AgentHarness {
   ): AsyncGenerator<ServerGeminiStreamEvent, Turn> {
     const startTime = Date.now();
     debugLogger.debug(
-      `[AgentHarness] Starting unified ReAct loop for agent: ${this.behavior.name}`,
+      `[AgentHarness] [${this.behavior.name}:${this.behavior.agentId}] Starting unified ReAct loop`,
     );
 
     const maxTurnsLimit = maxTurns ?? DEFAULT_MAX_TURNS;
@@ -164,6 +164,10 @@ export class AgentHarness {
     try {
       while (this.turnCounter < maxTurnsLimit) {
         const promptId = `${this.behavior.agentId}#${this.turnCounter}`;
+        debugLogger.debug(
+          `[AgentHarness] [${this.behavior.name}:${this.behavior.agentId}] Starting turn ${this.turnCounter} (promptId: ${promptId})`,
+        );
+
         if (combinedSignal.aborted) {
           terminateReason = deadlineTimer.signal.aborted
             ? AgentTerminateMode.TIMEOUT
@@ -370,12 +374,16 @@ export class AgentHarness {
       }
     } finally {
       deadlineTimer.abort();
+      const duration = Date.now() - startTime;
+      debugLogger.debug(
+        `[AgentHarness] [${this.behavior.name}:${this.behavior.agentId}] Finished. Outcome: ${terminateReason}, Duration: ${duration}ms, Turns: ${this.turnCounter}`,
+      );
       logAgentFinish(
         this.config,
         new AgentFinishEvent(
           this.behavior.agentId,
           this.behavior.name,
-          Date.now() - startTime,
+          duration,
           this.turnCounter,
           terminateReason,
         ),
@@ -426,6 +434,10 @@ export class AgentHarness {
     );
     const otherCalls = calls.filter((c) => c.name !== TASK_COMPLETE_TOOL_NAME);
 
+    debugLogger.debug(
+      `[AgentHarness] [${this.behavior.name}:${this.behavior.agentId}] Executing ${calls.length} tool calls (${otherCalls.length} scheduled)`,
+    );
+
     let completedCalls: Array<{
       request: ToolCallRequestInfo;
       response: { responseParts: Part[] };