Merge new summaries into persistent state (anchored iterative summarization), don't re-summarize from scratch

Digital Applied·medium signal

Factory's evaluation across 36,000 real engineering-session messages found that anchored iterative summarization — merging each new summary into a persistent running state — beats full-reconstruction summarization on accuracy, completeness, and continuity. The practical change: maintain one evolving summary object you append to, rather than re-summarizing the whole history every time you hit the threshold, which both loses fidelity and re-pays tokens. Pair with isolated subagents that each return only a 1,000–2,000 token condensed summary to the orchestrator.