Side-by-side sourced facts
Both columns quote the same reviewed Epoch AI catalog artifact. The LMArena row quotes the separately pinned snapshot published July 12, 2026 and appears only for an exact source model match. Missing values stay missing.
| Field |  Claude Fable 5 |  GPT-5.5 |
|---|---|---|
| Developer | Anthropic | OpenAI |
| Released | June 9, 2026 | April 23, 2026 |
| Domains | Language, Multimodal | Multimodal, Language, Vision |
| Tasks | Language modeling/generation, Question answering | Language modeling/generation, Question answering |
| Access | API access | API access |
| Weights | Closed weights | Closed weights |
| LMArena rating | 1507.5 (95% interval 1500.0 to 1515.0, 7,856 battles) | No exact model match in this snapshot |
| Context window | Not reported by this source | Not reported by this source |
| Price | Not reported by this source | Not reported by this source |
Common questions
Is Claude Fable 5 better than GPT-5.5?
No published ranking covers both models in Model Gauntlet's approved sources: the LMArena snapshot published July 12, 2026 has no exact match for GPT-5.5. The Epoch catalog documents what each model is for; it does not measure which is better.
Which is newer, Claude Fable 5 or GPT-5.5?
According to Epoch AI's model catalog (retrieved July 14, 2026), Claude Fable 5 is newer: it was released June 9, 2026, while GPT-5.5 was released April 23, 2026.
Can you self-host Claude Fable 5 or GPT-5.5?
Neither, according to the Epoch records: both models are closed-weight with API access only, so self-hosting is not supported by this evidence.
Evidence boundary
This page declares no winner beyond what a named source's numbers say. Where the sources do not overlap, the page says so plainly. Task quality, price, context window, latency, and reliability are not reported by these sources, so no claim about them appears here. Both models still require hands-on evaluation on your own workload.