CompareChat model comparison

Claude Fable 5.1 vs GPT-6 Luna

These two replace both sides of the GPT-5.6 Luna vs Claude Fable 5 comparison: Fable 5.1 succeeds Fable 5, and GPT-6 Luna succeeds GPT-5.6 Luna. Both are Paid-tier and take images; they differ in reasoning range, Fast availability, and one app-level role.

Capabilities reviewed 2026-09-26 · Evidence reviewed 2026-09-26

Try Claude Fable 5.1 Try GPT-6 Luna
How this comparison was made

Method and test inputs

This page lines up Claude Fable 5.1 and GPT-6 Luna using three repository sources: the generated public model catalog, the reasoning presets the customer chat picker defines for each model, and the artifact defaults in the Vizify app profile. It is a configuration comparison; it does not score outputs from either model and does not quote outside benchmarks.

  • Public catalog records for claude-fable-5.1 and gpt-6-luna
  • Chat-picker reasoning presets for both models
  • Artifact model defaults in the Vizify app profile
  • The earlier GPT-5.6 Luna vs Claude Fable 5 comparison, for continuity
Side by side

Claude Fable 5.1 vs GPT-6 Luna

CriterionClaude Fable 5.1GPT-6 Luna
Access in VizifyPaid tier: Pro or a credit pack purchasePaid tier: Pro or a credit pack purchase
InputText and imagesText and images
Reasoning steps in the pickerFive: off, low, medium, high, extra highSix: none, low, medium, high, extra high, max
Default and top stepMedium by default; extra high at the topMedium by default; max at the top
Fast variantNone listedGPT-6 Luna Fast, at twice the credits per token
Other role in the app profileNone; selected only from the chat pickerConfigured model for Vizify's HTML and React code-artifact generator
Predecessor, still availableClaude Fable 5 (/models/claude-fable-5/)GPT-5.6 Luna (/models/gpt-5-6/)
Choosing

Which one fits your task

Option A

Claude Fable 5.1

The successor to Claude Fable 5, documented on the Anthropic page, with a five-step effort control that tops out at extra high.

  • Carrying a Claude Fable 5 workflow forward to its successor
  • Choosing an effort step from off to extra high per request
  • Claude-family replies to a prompt with an attached image

Go with Claude Fable 5.1 if you are upgrading from Fable 5 or want a Claude model whose effort you can still set yourself, from off to extra high.

Try Claude Fable 5.1Claude Fable 5.1 details
Option B

GPT-6 Luna

The successor to GPT-5.6 Luna, with a six-step effort control up to max and a Fast variant; it is also the app profile's code-artifact model.

  • Moving a GPT-5.6 Luna conversation onto GPT-6
  • Requests where the max effort step or a Fast variant matters to you
  • GPT-family replies to a prompt that includes an uploaded image

Go with GPT-6 Luna if you are upgrading from GPT-5.6 Luna, want the extra max step, or want a Fast option. Its code-artifact role is a configuration fact, not a quality ranking.

Try GPT-6 LunaGPT-6 Luna details
Before you rely on this

Current limitations

  • Both models were checked against repository configuration on 2026-09-26. The page has no evidence about which one writes, reasons, or codes better.
  • GPT-6 Luna being the code-artifact model means the code generator step uses it whatever chat model you picked; the Agent can also write an artifact directly without that step.
  • Claude Fable 5 and GPT-5.6 Luna are compared on their own page and are only referenced here as predecessors.
  • Vizify never merges answers from Fable 5.1 and GPT-6 Luna; each message goes to the single model selected at the time.
  • Presets, tiers, and artifact defaults live in configuration that can change independently of this page.

This comparison is the follow-up to GPT-5.6 Luna vs Claude Fable 5. Each side of that page now has a successor in Vizify, and both successors keep what their predecessors had in common: Paid-tier access and text-plus-image input. Fable 5 and GPT-5.6 Luna are still available, so moving is a choice rather than a migration.

Reasoning control is where they part. Claude Fable 5.1 keeps the five-step range Fable 5 had, from off to extra high. GPT-6 Luna carries the six-step GPT range, adding max above extra high. Both default to medium, and both let you turn reasoning off entirely for a request.

GPT-6 Luna also has two properties Fable 5.1 does not. It comes with a Fast variant at twice the per-token credit rate, and the Vizify app profile names it as the model behind the code-artifact generator for HTML and React output. That second point is about configuration: if your chat model is Fable 5.1 and the Agent calls the code generator, that one step runs on GPT-6 Luna. It says nothing about which model writes better code.

FAQ

Questions about Claude Fable 5.1 and GPT-6 Luna

Is Claude Fable 5.1 or GPT-6 Luna better?

Vizify does not publish a ranking between them. The verifiable differences are the reasoning range, the Fast option on the GPT side, and GPT-6 Luna's configured role as the code-artifact model.

How do the reasoning settings differ?

Claude Fable 5.1 offers off, low, medium, high, and extra high. GPT-6 Luna offers none, low, medium, high, extra high, and max. Both start at medium, and both can switch reasoning off.

Is there a Claude Fable 5.1 Fast?

Not in the current catalog. GPT-6 Luna has a Fast variant, which is the same model on a faster serving tier at twice the credits per input and output token.

What does it mean that GPT-6 Luna is the code-artifact model?

Vizify's app profile names GPT-6 Luna for its HTML and React code generator. When the Agent uses that generator, the step runs on GPT-6 Luna even if your chat model is Claude Fable 5.1.

Are Claude Fable 5 and GPT-5.6 Luna going away?

No. Both remain in Vizify's catalog. Fable 5 keeps its page at /models/claude-fable-5/ and GPT-5.6 Luna at /models/gpt-5-6/, and existing conversations on them keep working.

Can free accounts use either model?

No. Both require Pro or a credit pack purchase; the free chat model is GPT-5.4 Mini.

Related

Keep comparing

GPT-5.6 Luna vs Claude Fable 5

The predecessor pairing this page updates; both of those models remain available.

Open

Claude Fable 5.1 on the Anthropic page

Fable 5.1 with Opus 5.5 and every other Claude model, including reasoning controls per model.

Open

GPT-6 Luna on the OpenAI page

GPT-6 Luna, Sol, and Astra, their Fast variants, and the earlier GPT chat models.

Open

Claude Opus 5.5 vs GPT-6 Sol

The other new Claude-versus-GPT-6 pairing, with fixed versus adjustable reasoning.

Open

ChatGPT alternative

Where Claude and other non-GPT options sit in Vizify's chat catalog.

Open
Switch to a successor

Open Vizify and continue with Claude Fable 5.1 or GPT-6 Luna.

Open Vizify Browse all models