GPT-6 Astra vs Claude Fable 5.1: which model is better for coding in 2026?

Output tokens

Output is the expensive half, and Astra writes around 27K tokens per task versus 78K for Fable 5.1. On the Intelligence Index, Astra costs $3.26 per task and Fable 5.1 $7.63.

Caching

Fable 5.1 charges $0.25 per million for cache reads, four times less than before. In agent sessions that run for hours, that helps a lot.

Example: one agent session

200K tokens of fresh input, 1.8M read from cache, and each model's typical output

• ✓You pay for the API yourself and every task counts
• ✓You live in the terminal: scripts, DevOps, CI, migrations
• ✓You already use ChatGPT or Codex daily
• ✓You need speed: Fast mode runs up to 2.5× faster (at twice the price)

• ✓Large refactors and multi-file migrations
• ✓Hard bugs where a confidently wrong answer is expensive
• ✓You already work in Claude Code or GitHub Copilot
• ✓Hours-long sessions with a lot of cached context

import OpenAI from "openai";

const client = new OpenAI();

const res = await client.responses.create({
  model: "gpt-6-astra",
  input: "Refactor this React hook to avoid extra renders: ...",
});

console.log(res.output_text);

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic();

const msg = await client.messages.create({
  model: "claude-fable-5-1",
  max_tokens: 16000,
  messages: [
    { role: "user", content: "Refactor this React hook to avoid extra renders: ..." },
  ],
});

for (const block of msg.content) {
  if (block.type === "text") console.log(block.text);
}

Claude Opus 5

Anthropic recommends starting here and moving up to Fable only if you need it.

Claude Sonnet 5

Fast for completions and small changes.

Muse Glimmer (Meta)

30B parameters, runs offline on a 24 GB GPU.