Claude Code now compacts idle sessions before the cache expires
Version 2.1.299 adds idle compaction, so a long conversation left open for about 54 minutes gets compressed before your next message has to reprocess it all.
Anthropic shipped Claude Code 2.1.299 on 14 October, and the headline change is idle compaction: a conversation over 200,000 tokens that sits idle for roughly 54 minutes now gets compacted automatically before its one-hour prompt cache expires. The 200K-token floor is configurable with CLAUDE_CODE_IDLE_COMPACT_MIN_TOKENS, and the whole feature can be switched off with "idleCompaction": false in settings.json. Both settings need v2.1.290 or later.
The same release adds CLAUDE_CODE_DISABLE_FILE_MENTIONS, which makes Claude read the paths of @ file mentions with its own file tools instead of being handed the file contents directly, plus /effort and /fast commands in agent view to set defaults for new sessions, and a safe mode indicator in the agents view peek panel for background sessions.
Why it matters: without idle compaction, stepping away from a long session and coming back after the cache has expired meant your next message silently reprocessed the entire history at full price. Walking away mid-task, a common pattern with long-running agent work, no longer carries that reprocessing cost by default.
{
"idleCompaction": false
}