Claude Fable 5 vs. Kimi K3: Same results, one-third the cost, 4x slower

Moonshot AI released Kimi K3 in mid-July, selling it as a serious professional coding tool that competes head-on with Claude and GPT, at a lower price. It’s a 2.8-trillion-parameter open-weight model, the largest ever out of China. The company says it rivals Anthropic’s Opus 4.8.

The Kimi K3 API runs $3 per million input tokens and $15 per million output. Anthropic’s top model, Fable 5, costs $10 per million input tokens and $50 per million output. That’s more than three times the price for both input and output.

A model that costs a third as much is only a good deal if the output and user experience meet current expectations. To find out where Kimi K3 stands against the professional tools it’s chasing, I gave Kimi K3 and Fable 5 the same three real coding jobs and tracked every token.

See also: Kimi K3 tops Arena’s coding leaderboard — and it’s open-weight

The tests

I used fd, the Rust file-finder from sharkdp. fd is a fast, friendlier replacement for the Unix find command. I chose it because it is real production Rust with a deep, documented bug history to pull from.

Kimi K3 is not available in coding tools like Cursor yet, so I completed the three tests using native CLIs. I ran Kimi K3 inside Moonshot’s new Kimi Code terminal agent (version 0.27.0), and Fable 5 inside Claude Code (version 2.1.212). I used identical prompts, so the model and CLIs were the only variables. I built a new folder for each test on each model (six total), so each test was standalone.

Here are the three tests I ran (in this order):

a bug fix

a multi-file refactor

a feature build

For every test, I recorded time (using a stopwatch), tokens, and cost from Cursor’s usage dashboard.

Earlier this week, I ran Grok 4.5 against Claude Opus 4.8 on the same three tasks in the same repo using identical prompts, which you can read here [add link]. Since all four models ran the same tests, you could consider this pair of articles Fable vs Kimi vs Opus vs Grok.

Setting up Kimi

This was a…