LangChain Deep Agents (Python) Overview Two pains bite every team reproducing LangChain's late-2025 Deep Agents blueprint. Virtual-FS state grows unboundedly (P51). The planner and every subagent write plans, scratch notes, intermediate drafts, and tool outputs into . Nothing ever evicts them. After 50 tool calls, the checkpointed state is 8 MB ; every takes 400 ms ; a run that started at 1.2 s per node visit ends at 2.5 s per node visit. The LangSmith trace viewer times out loading the thread. The user sees latency doubling over the run with no obvious tool-level culprit. Subagent persona le…