Pruner: Open-Source Local Proxy Cuts Claude API Costs by Up to 70%
Key Takeaways
- ▸Pruner reduces Claude API costs by 20–70% through automated context pruning, prompt cache injection, and tool output truncation—with verified savings using Anthropic's own tokenizer
- ▸Local-only proxy architecture ensures complete privacy: all code runs on localhost (127.0.0.1), API keys are never stored or logged, and zero telemetry is sent anywhere except api.anthropic.com
- ▸Zero-friction deployment with a single self-contained binary; no configuration, code changes, or external dependencies required; all Claude CLI flags work identically
Summary
Pruner, a new open-source local proxy tool, enables developers to reduce their Claude API bills by 20–70% without modifying code or changing Claude's behavior. The tool runs silently on localhost, automatically applying three optimization strategies in real-time: context pruning (trimming redundant conversation history), prompt cache injection (leveraging Anthropic's 90% cost reduction feature automatically), and tool output truncation. Pruner achieves verified savings using Anthropic's own tokenizer and count_tokens API, with developers seeing exact savings figures after each response.
The tool is designed with privacy and security as core principles—all code runs locally, API keys never leave the machine, and there is zero telemetry or external backend. Available as a self-contained binary under 20 MB for macOS and Linux, Pruner requires no configuration files, API key management, Node.js, or npm. The project is fully open-source under the MIT license on GitHub, allowing users to audit, verify, and compile the binary themselves.
- Fully open-source (MIT license) and auditable on GitHub, allowing developers to inspect, verify, and compile the tool independently
Editorial Opinion
Pruner addresses a real pain point for Claude users: API costs at scale. By intelligently applying Anthropic's own cost-reduction features (prompt caching) alongside context optimization, the tool demonstrates how middleware solutions can unlock significant savings without sacrificing functionality. The local-first, privacy-preserving architecture and open-source transparency set a strong example for developer tooling. However, aggressive context pruning could subtly affect Claude's performance in edge cases—users will need to carefully tune settings based on their workflows.
