# DeepSeek-Reasonix — Terminal Coding Agent Built Around DeepSeek's Prefix Cache Reports a 99.82% Cache Hit Rate, Cutting a 435M-Token Day From ~$61 to ~$12

> A terminal coding agent that bets on DeepSeek's prefix cache to keep long sessions cheap.

- Org: esengine
- Date: 2026-05-24
- Category: repo, tool
- Source: https://github.com/esengine/DeepSeek-Reasonix
- Canonical page: https://ai-tldr.dev/releases/esengine-deepseek-reasonix/

## In short

Open-source terminal coding agent built only for DeepSeek's API. It holds prompt prefixes byte-stable to maximize cache hits, with a reported 99.82% hit rate over 435M input tokens in a day that cut the workload to about $12.

## What it is

Reasonix is an open-source command-line coding agent that talks directly to DeepSeek's API with no provider-abstraction layer. It runs in your terminal, reads and edits files, and runs tasks, defaulting to DeepSeek-V4-Flash with a per-turn or per-session switch to V4-Pro.

## How it works

It is engineered around DeepSeek's byte-stable prefix cache: the agent keeps the prompt prefix identical across turns so cached tokens stay valid, using four mechanisms to avoid cache-invalidating edits. A tool-call repair layer fixes malformed tool calls so a turn rarely has to restart. The maintainers report a 99.82% cache hit rate across 435M input tokens in one day.

## Why it matters

Prefix-cache misses are the main hidden cost of long agent sessions. By holding the prefix stable, the same 435M-token day that would cost about $61 uncached on V4-Flash drops to roughly $12, making always-on agents affordable for solo developers.

## Who it's for

developers using DeepSeek's API

## Try it

npx reasonix code

## Links

- [Project Site](https://esengine.github.io/DeepSeek-Reasonix/)
- [GitHub Repo](https://github.com/esengine/DeepSeek-Reasonix)
- [Releases](https://github.com/esengine/DeepSeek-Reasonix/releases)
- [DeepSeek Integration](https://api-docs.deepseek.com/quick_start/agent_integrations/reasonix)