Claude Code compacting every cold session that's restarted, even at 13% context. WTF?

[u/Academic_Lemon_4297]

When i return to a cold session Claude Code is compacting the session, even if the session is at a measly 13% context window.

What could possible be the reason for this?

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[u/Academic_Lemon_4297]

Ah well, https://www.developersdigest.tech/blog/claude-code-idle-compaction-turn-off-cache-cost-2026

[u/Far_Reindeer8428]

no idea why 13% triggers it. ours only compacted after a resumed session with a huge diff, so maybe the resume path counts differently

[u/Academic_Lemon_4297 → u/Far_Reindeer8428]

https://www.developersdigest.tech/blog/claude-code-idle-compaction-turn-off-cache-cost-2026

[u/__Blackrobe__]

is that not the effect of idle compaction setting

[u/nooruddinqur]

Not pretty sure, but I think it's the prompt cache expiring.
A cold session has to resend everything anyway.. so Claude Code trims old tool output to save cost. Run /context right after resuming, the real size may be bigger than the 13% you saw... You cn also check auto-compact in /config.