GoKawiilStop paying to rebuild your Claude Code cache. When your main agent waits on a subagent for more than 5 minutes, its prompt cache silently expires, and the next turn re-encodes your entire conversation at the write rate instead of reading it back cheap. On long sessions with many subagents that's roughly 20% of your bill. claude-thermos keeps the cache warm so you never pay that tax.
Use
Run Claude Code exactly as you normally would, but through claude-thermos with uvx :
uvx claude-thermos # instead of: claude uvx claude-thermos -p " fix the bug " # any claude args pass straight through
Requires Python 3.11+ and the claude CLI on your PATH .
That's it. Warming runs automatically in the background. To disable it for a run without changing the command, set CLAUDE_WARMER_DISABLE=1 .
Tuning (all optional):
Flag Default Meaning --idle 270 Seconds the main agent must be idle before warming kicks in --interval 270 Seconds between warming cycles --max-cycles 4 Max warms per idle episode ( auto for unlimited) --subagent-window 540 Seconds a subagent counts as "still active"
Why your cache keeps expiring
Claude Code's prompt cache uses a 5-minute TTL. Every turn, your whole conversation history is served from cache at 0.1x the input price instead of being re-sent at full price, as long as the cache stays alive.
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