Original Reddit post

I’ve been down the compression and cache rabbit hole for weeks, across a few posts (Anthropic caching, OpenAI caching, RTK, Headroom). Pulling it together here because it’s about your Claude Code bill. The pitch you keep seeing is: install a “compress your context” tool and cut your token spend. I don’t think it holds up, and on Claude it can go the other way. Why the tools fight the wrong layer:

  1. They shrink one tool result. Your bill is set by resending the whole history hundreds of times per task. Trimming the newest 2KB of output does nothing about the near-full 200K window that rides along on every call.
  2. RTK’s “tokens saved” counter compares raw vs filtered output at about chars/4. It can’t see cache writes, cache reads, or that the agent already truncates big output on its own. It’s counting characters it deleted, not money. Why caching makes it worse, not better:
  3. On Claude a cached read is 10% of input, not 0%. A high cache rate isn’t free. It’s the same context going round again, not new work.
  4. Anthropic’s cache keys on an exact, byte-identical prefix. A tool that rewrites something upstream knocks the whole tail off the cache and back to full price.
  5. A cache write is 125% of input against a 10% read. Touching already-cached content can cost more than it ever removes. To break even, a change has to strip most of the whole invalidated tail, not just the block it edited. The one independent benchmark that exists (JetBrains) measured RTK raising Claude Code costs and debunked the 60-90% savings headline. It didn’t lower them. What actually moves the bill is runtime-level and boring: stop reinjecting context that hasn’t changed, retire tool output once it’s used, put small jobs on cheap models, and give yourself budgets you can see. None of that is compression. I wrote the whole thing up with the per-call numbers and every source linked. I’ll drop the link in a comment. Disclosure: I build tooling in this space and it’s in the writeup, so measure cost-per-successful-task in paired runs before trusting anyone, me included. Delete the compression plugins first either way. submitted by /u/KitchenAmoeba4438

Originally posted by u/KitchenAmoeba4438 on r/ClaudeCode