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Calling compact() in headless SDK sessions now returns a clear rejection instead of silently doing nothing
What
Headless sessions, meaning ones run with -p or through the SDK without the interactive terminal interface, now expose a compact() method, but calling it currently always fails with an explanatory error. That's because compaction in headless mode currently only happens inside a turn, triggered by a /compact prompt, not through a separate method call.
Why
This gives headless and SDK users a clear, catchable error explaining that compact() isn't available yet in that mode, instead of it failing silently or behaving unpredictably, so they know to work around it for now.
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Anthropic's release notes agree
Fixed resuming a session after /compact or another slash command ran via -p --resume: a spurious "Continue from where you left off." turn is…