# GPT-5.6 Luna and Fable 5 Compared in a Bug-Fixing Cost Benchmark

DevFeed: [GPT-5.6 Luna and Fable 5 Compared in a Bug-Fixing Cost Benchmark](<https://devfeed.tech/articles/how-to-cut-your-ai-bill-from-200-to-20-a-month-39168.md>)

Original publisher: [Read original article](<https://www.productcompass.pm/p/ai-coding-bill-20-a-month>)

Author: Paweł Huryn

Published: 2026-08-02T12:24:55Z

Content type: opinion

Language: en

Sources: [The Product Compass](<https://devfeed.tech/sources/the-product-compass.md>)

Topics: [Artificial Intelligence](<https://devfeed.tech/topics/ai.md>), [Benchmark](<https://devfeed.tech/topics/benchmark.md>), [anthropic](<https://devfeed.tech/topics/anthropic.md>), [Claude](<https://devfeed.tech/topics/claude.md>), [OpenAI](<https://devfeed.tech/topics/openai.md>), [ChatGPT](<https://devfeed.tech/topics/chatgpt.md>), [API](<https://devfeed.tech/topics/api.md>), [Claude Code](<https://devfeed.tech/topics/claude-code.md>), [context window](<https://devfeed.tech/topics/context-window.md>), [coding](<https://devfeed.tech/topics/coding.md>)

Tags: [ai](<https://devfeed.tech/tags/ai.md>), [api](<https://devfeed.tech/tags/api.md>), [benchmark](<https://devfeed.tech/tags/benchmark.md>), [chatgpt](<https://devfeed.tech/tags/chatgpt.md>), [claude](<https://devfeed.tech/tags/claude.md>), [claude-code](<https://devfeed.tech/tags/claude-code.md>), [efficiency](<https://devfeed.tech/tags/efficiency.md>), [performance](<https://devfeed.tech/tags/performance.md>), [token](<https://devfeed.tech/tags/token.md>)

## AI overview

The article describes experiments comparing AI model performance and cost for bug fixing. In the author's benchmark, GPT-5.6 Luna at maximum reasoning effort fixed 33 of 105 hidden bugs at an API cost of $1.80, while Fable 5 fixed 29 at a cost of $104.

## Source excerpt

Measured, not estimated: 105 hidden bugs, 10 frontier models, 14 runs. The $1.80 run beat the $104 one. My routing, and the setup.