Pick Claude Fable 5.1 for terminal-bench-science agentic research (52.6%, more than double fable 5's 24.7%) or cursorbench 3.2 agentic coding (73.4%). 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 5.1 (Anthropic) and GPT-5.4 Mini (OpenAI) are two of the models people most often weigh against each other in 2026. Claude Fable 5.1 is anthropic's September 1, 2026 update to its Fable line for coding and knowledge work, keeping the 1M-token context of Fable 5 while cutting cache-read costs and roughly doubling agentic-research benchmark scores. 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 5.1 holds 2.5× more — 1M tokens (~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 5.1 is the newer model by about 6 months (released September 1, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Claude Fable 5.1
GPT-5.4 Mini
Provider
Anthropic (US)
OpenAI (US)
Released
September 1, 2026
March 17, 2026
Context window
1M tokens (~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
text, image, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Terminal-Bench-Science agentic research (52.6%, more than double Fable 5's 24.7%): Claude Fable 5.1 — Anthropic's September 1, 2026 update to its Fable line for coding and knowledge work, keeping the 1M-token context of Fable 5 while cutting cache-read costs and roughly doubling agentic-research benchmark scores — and it carries the larger 1M tokens context.
CursorBench 3.2 agentic coding (73.4%): Claude Fable 5.1 — Anthropic's September 1, 2026 update to its Fable line for coding and knowledge work, keeping the 1M-token context of Fable 5 while cutting cache-read costs and roughly doubling agentic-research benchmark scores — and it is the newer of the two.
Cache-read pricing cut to a quarter of other Claude models: Claude Fable 5.1 — GPT-5.4 Mini is comparatively weak here — smaller context than flagship models
Free for every ChatGPT user: GPT-5.4 Mini — OpenAI's free, fast workhorse — capable general AI with no subscription needed — and it runs cheaper at $0.75/$4.5 per 1M tokens.
Fast, low-cost general tasks: GPT-5.4 Mini — At $0.75/$4.5 per 1M tokens it undercuts Claude Fable 5.1 ($10/$50 per 1M tokens), and that gap compounds at volume.
Subagent capabilities: GPT-5.4 Mini — GPT-5.4 Mini lists subagent capabilities among its strengths; Claude Fable 5.1 does not.
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 5.1 — Its 1M tokens window is about 2.5× larger than GPT-5.4 Mini's 400K, 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 5.1, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases: Claude Fable 5.1 — Larger 1M tokens window fits more in one prompt.
Anyone whose priority is terminal-bench-science agentic research (52.6%, more than double fable 5's 24.7%): Claude Fable 5.1 — 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 5.1: where it fits
Anthropic's September 1, 2026 update to its Fable line for coding and knowledge work, keeping the 1M-token context of Fable 5 while cutting cache-read costs and roughly doubling agentic-research benchmark scores. Released September 1, 2026 by Anthropic, it is built for terminal-Bench-Science agentic research (52.6%, more than double Fable 5's 24.7%), cursorBench 3.2 agentic coding (73.4%), cache-read pricing cut to a quarter of other Claude models, and long, multistep, document-heavy professional work with 1M-token context.
Its trade-offs are real: anthropic has not published an official SWE-bench Verified score for this model, restricted Mythos 5.1 variant outscores it on some benchmarks due to lighter safeguards (Terminal-Bench 4.0: 60.9% vs 55.8%), and closed weights, no self-hosting option. 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 5.1 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 5.1 holds the larger context; and each leads in its own area — Claude Fable 5.1 for terminal-bench-science agentic research (52.6%, more than double fable 5's 24.7%), 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 5.1 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 5.1 leans toward terminal-bench-science agentic research (52.6%, more than double fable 5's 24.7%) 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 5.1 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 5.1 — 1M tokens 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 5.1 and GPT-5.4 Mini together?
Yes — a multi-model platform like LumiChats gives you Claude Fable 5.1, 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 5.1 or GPT-5.4 Mini?
Claude Fable 5.1 — released September 1, 2026, about 6 months after GPT-5.4 Mini.
Claude Fable 5.1 vs GPT-5.4 Mini
Anthropic · US | OpenAI · US · Updated June 2026
Quick verdict
Pick Claude Fable 5.1 for terminal-bench-science agentic research (52.6%, more than double fable 5's 24.7%) or cursorbench 3.2 agentic coding (73.4%). 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 5.1 (Anthropic) and GPT-5.4 Mini (OpenAI) are two of the models people most often weigh against each other in 2026. Claude Fable 5.1 is anthropic's September 1, 2026 update to its Fable line for coding and knowledge work, keeping the 1M-token context of Fable 5 while cutting cache-read costs and roughly doubling agentic-research benchmark scores. 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 5.1 holds 2.5× more — 1M tokens (~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 5.1 is the newer model by about 6 months (released September 1, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Claude Fable 5.1
GPT-5.4 Mini
Provider
Anthropic (US)
OpenAI (US)
Released
September 1, 2026
March 17, 2026
Context window
1M tokens (~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
text, image, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Terminal-Bench-Science agentic research (52.6%, more than double Fable 5's 24.7%)
Claude Fable 5.1
Anthropic's September 1, 2026 update to its Fable line for coding and knowledge work, keeping the 1M-token context of Fable 5 while cutting cache-read costs and roughly doubling agentic-research benchmark scores — and it carries the larger 1M tokens context.
CursorBench 3.2 agentic coding (73.4%)
Claude Fable 5.1
Anthropic's September 1, 2026 update to its Fable line for coding and knowledge work, keeping the 1M-token context of Fable 5 while cutting cache-read costs and roughly doubling agentic-research benchmark scores — and it is the newer of the two.
Cache-read pricing cut to a quarter of other Claude models
Claude Fable 5.1
GPT-5.4 Mini is comparatively weak here — smaller context than flagship models
Free for every ChatGPT user
GPT-5.4 Mini
OpenAI's free, fast workhorse — capable general AI with no subscription needed — and it runs cheaper at $0.75/$4.5 per 1M tokens.
Fast, low-cost general tasks
GPT-5.4 Mini
At $0.75/$4.5 per 1M tokens it undercuts Claude Fable 5.1 ($10/$50 per 1M tokens), and that gap compounds at volume.
Subagent capabilities
GPT-5.4 Mini
GPT-5.4 Mini lists subagent capabilities among its strengths; Claude Fable 5.1 does not.
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 5.1
Its 1M tokens window is about 2.5× larger than GPT-5.4 Mini's 400K, 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 5.1, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ Claude Fable 5.1
Larger 1M tokens window fits more in one prompt.
Anyone whose priority is terminal-bench-science agentic research (52.6%, more than double fable 5's 24.7%)
→ Claude Fable 5.1
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 5.1: where it fits
Anthropic's September 1, 2026 update to its Fable line for coding and knowledge work, keeping the 1M-token context of Fable 5 while cutting cache-read costs and roughly doubling agentic-research benchmark scores. Released September 1, 2026 by Anthropic, it is built for terminal-Bench-Science agentic research (52.6%, more than double Fable 5's 24.7%), cursorBench 3.2 agentic coding (73.4%), cache-read pricing cut to a quarter of other Claude models, and long, multistep, document-heavy professional work with 1M-token context.
Its trade-offs are real: anthropic has not published an official SWE-bench Verified score for this model, restricted Mythos 5.1 variant outscores it on some benchmarks due to lighter safeguards (Terminal-Bench 4.0: 60.9% vs 55.8%), and closed weights, no self-hosting option. 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 5.1 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 5.1 holds the larger context; and each leads in its own area — Claude Fable 5.1 for terminal-bench-science agentic research (52.6%, more than double fable 5's 24.7%), 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 5.1 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 5.1 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 5.1 leans toward terminal-bench-science agentic research (52.6%, more than double fable 5's 24.7%) 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 5.1 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 5.1 — 1M tokens 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 5.1 and GPT-5.4 Mini together?
Yes — a multi-model platform like LumiChats gives you Claude Fable 5.1, 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 5.1 or GPT-5.4 Mini?
Claude Fable 5.1 — released September 1, 2026, about 6 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.