fix: patch stale rootAgent references in ADK agent tree

ADK's BaseAgent computes rootAgent once at construction. Module-level
singleton sub-agents get rootAgent=self since no parent exists yet.
When the planning agent later sets parentAgent via setParentAgentForSubAgents(),
rootAgent is never recomputed — so all sub-agent transfers fail with
"Agent X not found in the agent tree." even for the root agent itself.

Add fixAgentTreeRoots() to recursively patch rootAgent on all descendants
after the planning agent hierarchy is constructed.

Author: elicollinson

claude.md

@@ -10,13 +10,8 @@ Before pushing any code changes, you **must** complete the following verificatio
 
 After making any code changes, always start by running the code simplifier plugin to ensure the code is clean and follows best practices.
 
-The code-simplifier is an Anthropic-published plugin for Claude Code. Run it via:
+The code-simplifier is an Anthropic-published agent plugin for Claude Code. Run it via: the code-simplifier:codesimplifier agent
 
-```bash
-/simplify
-```
-
-Or use the Claude Code CLI with the code-simplifier plugin enabled.
 
 ### 2. Run Unit Tests
 

src/agents/planning.ts

@@ -131,6 +131,24 @@ function getDynamicInstruction(context: InstructionContext): string {
   return baseInstruction.replace('{plan_state}', currentPlan);
 }
 
+/**
+ * Fix stale rootAgent references in the agent tree.
+ *
+ * ADK's BaseAgent computes `rootAgent` once at construction time by traversing
+ * `parentAgent` upward. But when agents are created as module-level singletons
+ * (before any parent exists), their `rootAgent` points to themselves. When the
+ * parent later calls `setParentAgentForSubAgents()`, it sets `parentAgent` but
+ * never recomputes `rootAgent`. This causes `getAgentByName()` to fail when
+ * sub-agents attempt transfers — they only search their own empty subtree.
+ */
+function fixAgentTreeRoots(agent: LlmAgent, root: LlmAgent): void {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any -- rootAgent is not exposed in ADK's public types
+  (agent as any).rootAgent = root;
+  for (const sub of agent.subAgents) {
+    fixAgentTreeRoots(sub as LlmAgent, root);
+  }
+}
+
 /**
  * Creates a planning agent with dynamic MCP tools
  * Use this when you need MCP tools to be fully initialized
@@ -163,12 +181,21 @@ Transfer back to planning_agent immediately.`,
     ...additionalSubAgents,
   ];
 
-  return new LlmAgent({
+  const planningAgent = new LlmAgent({
     name: 'planning_agent',
     model: modelName,
     description: 'Orchestrates multi-step tasks across specialist agents.',
     instruction: getDynamicInstruction,
     afterModelCallback: saveMemoriesOnFinalResponse,
     subAgents,
   });
+
+  // Fix stale rootAgent references (ADK bug workaround)
+  fixAgentTreeRoots(planningAgent, planningAgent);
+
+  agentLogger.debug(
+    '[Planning] Agent tree rootAgent fix applied — all sub-agents now reference planning_agent as root'
+  );
+
+  return planningAgent;
 }

src/agents/runner.ts

@@ -48,15 +48,15 @@ function serializeError(error: unknown): string {
 }
 
 /**
- * Debug: Log the agent hierarchy
+ * Debug: Log the agent hierarchy with model and rootAgent info
  */
-export function logAgentHierarchy(agent: LlmAgent, indent = 0) {
+export function logAgentHierarchy(agent: LlmAgent, indent = 0): void {
   const prefix = '  '.repeat(indent);
-  agentLogger.debug(`${prefix}[Agent] ${agent.name} (model: ${agent.model})`);
-  if (agent.subAgents && agent.subAgents.length > 0) {
-    for (const subAgent of agent.subAgents) {
-      logAgentHierarchy(subAgent as LlmAgent, indent + 1);
-    }
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any -- rootAgent is not exposed in ADK's public types
+  const rootName = (agent as any).rootAgent?.name ?? 'unknown';
+  agentLogger.debug(`${prefix}[Agent] ${agent.name} (model: ${agent.model}, root: ${rootName})`);
+  for (const subAgent of agent.subAgents) {
+    logAgentHierarchy(subAgent as LlmAgent, indent + 1);
   }
 }
 
@@ -66,6 +66,7 @@ export function logAgentHierarchy(agent: LlmAgent, indent = 0) {
  */
 export async function createRunner(): Promise<InMemoryRunner> {
   const initializedRootAgent = await createPlanningAgent();
+  logAgentHierarchy(initializedRootAgent);
   return new InMemoryRunner({
     agent: initializedRootAgent,
     appName: APP_NAME,