LangChain Ships Deep Agents v0.7 by Deleting Its Base System Prompt and Demoting Todo Lists to Opt-In

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Deep Agents v0.7 landed July 29 with a contrarian result for anyone building an agent harness: LangChain removed the base system prompt entirely and trimmed tool descriptions by 43%, cutting base input tokens roughly 65% (about 6k down to about 2k per default agent turn) with comparable performance across models. More pointedly, TodoListMiddleware moved from default to opt-in because evals showed it did not meaningfully help across most use cases, contradicting the todo-list-planning orthodoxy that ships in most agent scaffolds. Breaking changes include removal of deprecated backend factory support and a new delete tool in the default filesystem toolkit.