Claude Fable 5 vs GPT-5.5
Anthropic · US | OpenAI · US · Updated June 2026
Quick verdict
Pick Claude Fable 5 for the hardest reasoning and most complex problems or long-horizon, multi-step agentic work. Pick GPT-5.5 for terminal, cli and computer-use automation or long-horizon tool sequencing. On a tight budget at scale, GPT-5.5 is the value pick.
Claude Fable 5 (Anthropic) and GPT-5.5 (OpenAI) are two of the models people most often weigh against each other in 2026. Claude Fable 5 is anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive. GPT-5.5 is openAI's first fully retrained base since GPT-4.5 — the terminal and computer-use champion. Their biggest split is price, and the breakdown below shows exactly how that plays out for your workload.
Key differences at a glance
- ▸Price: GPT-5.5 is about 2× cheaper on input ($5/$30 per 1M tokens vs $10/$50 per 1M tokens) — meaningful once you are processing millions of tokens a month.
- ▸Context window: both advertise 1M (~1,500 pages). Tie on paper — test on your own long inputs, since usable recall varies by model.
- ▸Recency: Claude Fable 5 is the newer model by about 47 days (released June 9, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
| Spec | Claude Fable 5 | GPT-5.5 |
|---|---|---|
| Provider | Anthropic (US) | OpenAI (US) |
| Released | June 9, 2026 | April 23, 2026 |
| Context window | 1M (~1,500 pages) | 1M (~1,500 pages) |
| Price (in/out) | $10/$50 per 1M tokens | $5/$30 per 1M tokens |
| Open weight? | No — API only | No — API only |
| Modalities | text, image, code | text, image, code |
| SWE-Bench Verified | Not published | Not published |
| MRCR v2 @ 1M | Not published | Not published |
Who wins what
The hardest reasoning and most complex problems
Claude Fable 5
GPT-5.5 is comparatively weak here — trails Opus 4.8 on hardest coding benchmarks
Long-horizon, multi-step agentic work
Claude Fable 5
Anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive — and it is the newer of the two.
Frontier-level analysis and research
Claude Fable 5
Claude Fable 5 lists frontier-level analysis and research among its strengths; GPT-5.5 does not.
Terminal, CLI and computer-use automation
GPT-5.5
OpenAI's first fully retrained base since GPT-4.5 — the terminal and computer-use champion — and it runs cheaper at $5/$30 per 1M tokens.
Long-horizon tool sequencing
GPT-5.5
GPT-5.5 lists long-horizon tool sequencing among its strengths; Claude Fable 5 does not.
Strong agentic coding and reasoning
GPT-5.5
GPT-5.5 lists strong agentic coding and reasoning among its strengths; Claude Fable 5 does not.
Lowest cost at scale
GPT-5.5
At $5/$30 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Which should you pick?
A cost-sensitive startup shipping high volume
→ GPT-5.5
At $5/$30 per 1M tokens it undercuts Claude Fable 5, and on millions of tokens that margin decides the monthly bill.
Anyone whose priority is the hardest reasoning and most complex problems
→ Claude Fable 5
It is specifically built for that.
Anyone whose priority is terminal, cli and computer-use automation
→ GPT-5.5
That is its strongest area.
Claude Fable 5: where it fits
Anthropic's top public Mythos-class model and its most capable yet, though tier access was temporarily suspended in June 2026 under a US export-control directive. Released June 9, 2026 by Anthropic, it is built for the hardest reasoning and most complex problems, long-horizon, multi-step agentic work, frontier-level analysis and research, and work where maximum capability outweighs cost.
Its trade-offs are real: highest price in the Claude lineup, and tier access was temporarily suspended in June 2026 under a US export-control directive. At $10 in / $50 out per million tokens, it sits in the premium price band.
GPT-5.5: where it fits
OpenAI's first fully retrained base since GPT-4.5 — the terminal and computer-use champion. Released April 23, 2026 by OpenAI, it is built for terminal, CLI and computer-use automation, long-horizon tool sequencing, strong agentic coding and reasoning, and browser-driving agents.
Its trade-offs: trails Opus 4.8 on hardest coding benchmarks, and tiered long-context pricing above 272K tokens. At $5 in / $30 out per million tokens, it sits in the premium price band.
The bottom line for this matchup
Claude Fable 5 and GPT-5.5 overlap enough that the right pick depends on your specific job. GPT-5.5 costs less per token; and each leads in its own area — Claude Fable 5 for the hardest reasoning and most complex problems, GPT-5.5 for terminal, cli and computer-use automation. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both Claude Fable 5 and GPT-5.5 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
See pricingFrequently asked questions
Is Claude Fable 5 or GPT-5.5 better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, Claude Fable 5 leans toward the hardest reasoning and most complex problems while GPT-5.5 leans toward terminal, cli and computer-use automation, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Fable 5 or GPT-5.5?
GPT-5.5 is cheaper — $10/$50 per 1M tokens vs $5/$30 per 1M tokens, roughly 2× apart on input.
Which has the bigger context window?
Both advertise 1M (~1,500 pages). Remember advertised ≠ usable: recall typically degrades before the ceiling.
Can I use both Claude Fable 5 and GPT-5.5 together?
Yes — a multi-model platform like LumiChats gives you Claude Fable 5, GPT-5.5 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, Claude Fable 5 or GPT-5.5?
Claude Fable 5 — released June 9, 2026, about 47 days after GPT-5.5.
Related comparisons
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.