We've reached a point where LLMs are capable enough to power many agentic workflows, yet relatively few AI agents make it into stable, long-term production. In your experience, what's been the hardest engineering challenge to solve? Tool reliability? Long-term memory? Planning and reasoning? Context management? Evaluation and benchmarking? Authentication and permissions? Multi-agent orchestration? Cost and latency? Human-in-the-loop approval? Something else? If you've...