// HACKER NEWS — CYBERSECURITY
RTK reports token savings, but our cost benchmarks disagree
RTK (Rust Token Killer) filters and compresses terminal output before the AI agent reads it. With over 79k GitHub stars today, RTK is one of the most popular tools to make AI coding cheaper.
One X post saying RTK could cut Claude Code tokens by up to 60% reached 313K views.
Yet JetBrains’s SkillsBench run found no savings. The README has a disclaimer:
RTK cuts up to 90% of the bash output your agent reads. […] it is not the same as cutting your bill by 90%.
So “less terminal output” is not the same as “cheaper AI coding”. It can help, be a no-op, or backfire (more turns or lower quality). In this post, we present our findings after several days and over $1,500 spent on tokens.
RTK can rewrite Git, test, package and file commands the agent runs through its shell tool (Bash in Claude Code, bash in OpenCode). Each rewrite returns a terser version of the same output.
For example, RTK keeps file names, sizes and permissions (644 means rw-r—r—), but drops the owner and date:
RTK compresses terminal output, so we tested it on Terminal-Bench 2.1, a benchmark with heavy terminal interaction. We stayed on 2.1 rather than the newer 3.0 and 4.0: agents pass most 2.1 tasks, while 3.0 and 4.0 are still a challenge. Cost only matters for tasks that pass.
We ran Claude Code with Fable 5.0, and OpenCode with DeepSeek V4 Pro 0813 through OpenRouter. Each task was scheduled five times without RTK and five times with it, on the same model route, platform and task-specific timeout.
After removing four Fable security tasks that got refusals, the final comparison covers 85 Fable tasks and 89 DeepSeek tasks, or 1,740 attempts.