Pick Claude Fable 5 for the hardest reasoning and most complex problems or long-horizon, multi-step agentic work. Pick GPT-5.4 Mini for free for every chatgpt user or fast, low-cost general tasks. On a tight budget at scale, GPT-5.4 Mini is the value pick.
Claude Fable 5 (Anthropic) and GPT-5.4 Mini (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-5.4 Mini is openAI's free, fast workhorse — capable general AI with no subscription needed. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences
Price: GPT-5.4 Mini is about 13× cheaper on input ($0.75/$4.5 per 1M tokens vs $10/$50 per 1M tokens) — a large enough gap that at scale it can be the single biggest line item in the decision.
Context window: Claude Fable 5 holds 2.5× more — 1M (~1,500 pages) vs 400K (~600 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
Recency: Claude Fable 5 is the newer model by about 3 months (released June 9, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Claude Fable 5
GPT-5.4 Mini
Provider
Anthropic (US)
OpenAI (US)
Released
June 9, 2026
March 17, 2026
Context window
1M (~1,500 pages)
400K (~600 pages)
Price (in/out)
$10/$50 per 1M tokens
$0.75/$4.5 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 — A core design strength of Claude Fable 5.
Long-horizon, multi-step agentic work: Claude Fable 5 — A core design strength of Claude Fable 5.
Frontier-level analysis and research: Claude Fable 5 — A core design strength of Claude Fable 5.
Free for every ChatGPT user: GPT-5.4 Mini — A core design strength of GPT-5.4 Mini.
Fast, low-cost general tasks: GPT-5.4 Mini — A core design strength of GPT-5.4 Mini.
Subagent capabilities: GPT-5.4 Mini — A core design strength of GPT-5.4 Mini.
Lowest cost at scale: GPT-5.4 Mini — At $0.75/$4.5 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input: Claude Fable 5 — Its 1M window is about 2.5× larger, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: GPT-5.4 Mini — At $0.75/$4.5 per 1M tokens it undercuts Claude Fable 5, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases: Claude Fable 5 — Larger 1M window fits more in one prompt.
Anyone whose priority is the hardest reasoning and most complex problems: Claude Fable 5 — It is specifically built for that.
Anyone whose priority is free for every chatgpt user: GPT-5.4 Mini — 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-5.4 Mini: where it fits
OpenAI's free, fast workhorse — capable general AI with no subscription needed. Released March 17, 2026 by OpenAI, it is built for free for every ChatGPT user, fast, low-cost general tasks, subagent capabilities, and native multimodal reasoning.
Its trade-offs: smaller context than flagship models, and not for the hardest reasoning. At $0.75 in / $4.5 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
Claude Fable 5 and GPT-5.4 Mini overlap enough that the right pick depends on your specific job. GPT-5.4 Mini costs less per token; Claude Fable 5 holds the larger context; and each leads in its own area — Claude Fable 5 for the hardest reasoning and most complex problems, GPT-5.4 Mini for free for every chatgpt user. Rather than crowning one, run the same hard task through both once and let the results decide.
Frequently asked questions
Is Claude Fable 5 or GPT-5.4 Mini 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-5.4 Mini leans toward free for every chatgpt user, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Fable 5 or GPT-5.4 Mini?
GPT-5.4 Mini is cheaper — $10/$50 per 1M tokens vs $0.75/$4.5 per 1M tokens, roughly 13× apart on input.
Which has the bigger context window?
Claude Fable 5 — 1M vs 400K, about 2.5× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both Claude Fable 5 and GPT-5.4 Mini together?
Yes — a multi-model platform like LumiChats gives you Claude Fable 5, GPT-5.4 Mini 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-5.4 Mini?
Claude Fable 5 — released June 9, 2026, about 3 months after GPT-5.4 Mini.
Claude Fable 5 vs GPT-5.4 Mini
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-5.4 Mini for free for every chatgpt user or fast, low-cost general tasks. On a tight budget at scale, GPT-5.4 Mini is the value pick.
Claude Fable 5 (Anthropic) and GPT-5.4 Mini (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-5.4 Mini is openAI's free, fast workhorse — capable general AI with no subscription needed. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences at a glance
▸Price: GPT-5.4 Mini is about 13× cheaper on input ($0.75/$4.5 per 1M tokens vs $10/$50 per 1M tokens) — a large enough gap that at scale it can be the single biggest line item in the decision.
▸Context window: Claude Fable 5 holds 2.5× more — 1M (~1,500 pages) vs 400K (~600 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
▸Recency: Claude Fable 5 is the newer model by about 3 months (released June 9, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Claude Fable 5
GPT-5.4 Mini
Provider
Anthropic (US)
OpenAI (US)
Released
June 9, 2026
March 17, 2026
Context window
1M (~1,500 pages)
400K (~600 pages)
Price (in/out)
$10/$50 per 1M tokens
$0.75/$4.5 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
A core design strength of Claude Fable 5.
Long-horizon, multi-step agentic work
Claude Fable 5
A core design strength of Claude Fable 5.
Frontier-level analysis and research
Claude Fable 5
A core design strength of Claude Fable 5.
Free for every ChatGPT user
GPT-5.4 Mini
A core design strength of GPT-5.4 Mini.
Fast, low-cost general tasks
GPT-5.4 Mini
A core design strength of GPT-5.4 Mini.
Subagent capabilities
GPT-5.4 Mini
A core design strength of GPT-5.4 Mini.
Lowest cost at scale
GPT-5.4 Mini
At $0.75/$4.5 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input
Claude Fable 5
Its 1M window is about 2.5× larger, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ GPT-5.4 Mini
At $0.75/$4.5 per 1M tokens it undercuts Claude Fable 5, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ Claude Fable 5
Larger 1M window fits more in one prompt.
Anyone whose priority is the hardest reasoning and most complex problems
→ Claude Fable 5
It is specifically built for that.
Anyone whose priority is free for every chatgpt user
→ GPT-5.4 Mini
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-5.4 Mini: where it fits
OpenAI's free, fast workhorse — capable general AI with no subscription needed. Released March 17, 2026 by OpenAI, it is built for free for every ChatGPT user, fast, low-cost general tasks, subagent capabilities, and native multimodal reasoning.
Its trade-offs: smaller context than flagship models, and not for the hardest reasoning. At $0.75 in / $4.5 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
Claude Fable 5 and GPT-5.4 Mini overlap enough that the right pick depends on your specific job. GPT-5.4 Mini costs less per token; Claude Fable 5 holds the larger context; and each leads in its own area — Claude Fable 5 for the hardest reasoning and most complex problems, GPT-5.4 Mini for free for every chatgpt user. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both Claude Fable 5 and GPT-5.4 Mini 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.
Is Claude Fable 5 or GPT-5.4 Mini 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-5.4 Mini leans toward free for every chatgpt user, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Fable 5 or GPT-5.4 Mini?
GPT-5.4 Mini is cheaper — $10/$50 per 1M tokens vs $0.75/$4.5 per 1M tokens, roughly 13× apart on input.
Which has the bigger context window?
Claude Fable 5 — 1M vs 400K, about 2.5× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both Claude Fable 5 and GPT-5.4 Mini together?
Yes — a multi-model platform like LumiChats gives you Claude Fable 5, GPT-5.4 Mini 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-5.4 Mini?
Claude Fable 5 — released June 9, 2026, about 3 months after GPT-5.4 Mini.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.