LangChain's deepagents patches private state leaking from a parent agent into subagents

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langchain-quickjs 0.3.7, released 2026-09-06, fixes issue #3543 so private state is kept out of subagent propagation, and adds native streaming of PTC tool calls (#5735). The state-isolation fix matters beyond this package: in a spawn-subagents architecture, anything the parent holds privately is a candidate for accidental inheritance, and this is the same class of boundary failure that paper after paper is now benchmarking. Single-source (the release notes and linked commits) with no accompanying advisory, so treat the exposure scope as unquantified.