Show HN: Claude-thermos – keeps your Claude session warm for you
Claude-thermos is a new tool designed to prevent Claude Code's prompt cache from expiring during long sessions. By keeping the cache warm, it avoids costly re-encoding fees that occur when subagents cause the main agent's cache to time out.
Why it matters
As AI development costs rise, tools that optimize token usage and cache management are becoming essential for developers managing complex agentic workflows.
Stop 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.
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 .
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