Pick Claude Fable 5 for the hardest reasoning and most complex problems or long-horizon, multi-step agentic work. Pick Grok Code Fast 1 for fast, cheap agentic coding at $0.20/$1.50 or low-latency code generation and terminal tasks. On a tight budget at scale, Grok Code Fast 1 is the value pick.
Claude Fable 5 (Anthropic) and Grok Code Fast 1 (xAI) 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. Grok Code Fast 1 is xAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences
Price: Grok Code Fast 1 is about 50× cheaper on input ($0.2/$1.5 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 3.9× more — 1M (~1,500 pages) vs 256K (~384 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 10 months (released June 9, 2026), usually meaning fresher training data and capabilities.
Specifications
Spec
Claude Fable 5
Grok Code Fast 1
Provider
Anthropic (US)
xAI (US)
Released
June 9, 2026
August 28, 2025
Context window
1M (~1,500 pages)
256K (~384 pages)
Price (in/out)
$10/$50 per 1M tokens
$0.2/$1.5 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, 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 — 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 carries the larger 1M context.
Long-horizon, multi-step agentic work: Claude Fable 5 — Its 1M window holds about 3.9× more than Grok Code Fast 1's 256K in a single prompt.
Frontier-level analysis and research: Claude Fable 5 — Grok Code Fast 1 is comparatively weak here — a speed-tier coding model, not a frontier reasoner
Fast, cheap agentic coding at $0.20/$1.50: Grok Code Fast 1 — At $0.2/$1.5 per 1M tokens it undercuts Claude Fable 5 ($10/$50 per 1M tokens), and that gap compounds at volume.
Low-latency code generation and terminal tasks: Grok Code Fast 1 — XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality — and it runs cheaper at $0.2/$1.5 per 1M tokens.
High-volume coding pipelines where speed beats peak quality: Grok Code Fast 1 — Grok Code Fast 1 lists high-volume coding pipelines where speed beats peak quality among its strengths; Claude Fable 5 does not.
Lowest cost at scale: Grok Code Fast 1 — At $0.2/$1.5 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 3.9× larger than Grok Code Fast 1's 256K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: Grok Code Fast 1 — At $0.2/$1.5 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 fast, cheap agentic coding at $0.20/$1.50: Grok Code Fast 1 — 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.
Grok Code Fast 1: where it fits
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. Released August 28, 2025 by xAI, it is built for fast, cheap agentic coding at $0.20/$1.50, low-latency code generation and terminal tasks, high-volume coding pipelines where speed beats peak quality, and a 256K window sized for real codebases.
Its trade-offs: text and code only — no image, audio or video input, xAI did not publish a SWE-Bench Verified score, a speed-tier coding model, not a frontier reasoner, and narrow focus — built for code, not general knowledge work. At $0.2 in / $1.5 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
Claude Fable 5 and Grok Code Fast 1 overlap enough that the right pick depends on your specific job. Grok Code Fast 1 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, Grok Code Fast 1 for fast, cheap agentic coding at $0.20/$1.50. 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 Grok Code Fast 1 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 Grok Code Fast 1 leans toward fast, cheap agentic coding at $0.20/$1.50, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Fable 5 or Grok Code Fast 1?
Grok Code Fast 1 is cheaper — $10/$50 per 1M tokens vs $0.2/$1.5 per 1M tokens, roughly 50× apart on input.
Which has the bigger context window?
Claude Fable 5 — 1M vs 256K, about 3.9× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both Claude Fable 5 and Grok Code Fast 1 together?
Yes — a multi-model platform like LumiChats gives you Claude Fable 5, Grok Code Fast 1 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 Grok Code Fast 1?
Claude Fable 5 — released June 9, 2026, about 10 months after Grok Code Fast 1.
Claude Fable 5 vs Grok Code Fast 1
Anthropic · US | xAI · 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 Grok Code Fast 1 for fast, cheap agentic coding at $0.20/$1.50 or low-latency code generation and terminal tasks. On a tight budget at scale, Grok Code Fast 1 is the value pick.
Claude Fable 5 (Anthropic) and Grok Code Fast 1 (xAI) 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. Grok Code Fast 1 is xAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences at a glance
▸Price: Grok Code Fast 1 is about 50× cheaper on input ($0.2/$1.5 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 3.9× more — 1M (~1,500 pages) vs 256K (~384 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 10 months (released June 9, 2026), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
Claude Fable 5
Grok Code Fast 1
Provider
Anthropic (US)
xAI (US)
Released
June 9, 2026
August 28, 2025
Context window
1M (~1,500 pages)
256K (~384 pages)
Price (in/out)
$10/$50 per 1M tokens
$0.2/$1.5 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, 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
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 carries the larger 1M context.
Long-horizon, multi-step agentic work
Claude Fable 5
Its 1M window holds about 3.9× more than Grok Code Fast 1's 256K in a single prompt.
Frontier-level analysis and research
Claude Fable 5
Grok Code Fast 1 is comparatively weak here — a speed-tier coding model, not a frontier reasoner
Fast, cheap agentic coding at $0.20/$1.50
Grok Code Fast 1
At $0.2/$1.5 per 1M tokens it undercuts Claude Fable 5 ($10/$50 per 1M tokens), and that gap compounds at volume.
Low-latency code generation and terminal tasks
Grok Code Fast 1
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality — and it runs cheaper at $0.2/$1.5 per 1M tokens.
High-volume coding pipelines where speed beats peak quality
Grok Code Fast 1
Grok Code Fast 1 lists high-volume coding pipelines where speed beats peak quality among its strengths; Claude Fable 5 does not.
Lowest cost at scale
Grok Code Fast 1
At $0.2/$1.5 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 3.9× larger than Grok Code Fast 1's 256K, fitting roughly 1,500 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ Grok Code Fast 1
At $0.2/$1.5 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 fast, cheap agentic coding at $0.20/$1.50
→ Grok Code Fast 1
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.
Grok Code Fast 1: where it fits
XAI's speed-tier coding model at $0.20/$1.50 with a 256K window — cheap, fast agentic code over frontier quality. Released August 28, 2025 by xAI, it is built for fast, cheap agentic coding at $0.20/$1.50, low-latency code generation and terminal tasks, high-volume coding pipelines where speed beats peak quality, and a 256K window sized for real codebases.
Its trade-offs: text and code only — no image, audio or video input, xAI did not publish a SWE-Bench Verified score, a speed-tier coding model, not a frontier reasoner, and narrow focus — built for code, not general knowledge work. At $0.2 in / $1.5 out per million tokens, it sits in the budget price band.
The bottom line for this matchup
Claude Fable 5 and Grok Code Fast 1 overlap enough that the right pick depends on your specific job. Grok Code Fast 1 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, Grok Code Fast 1 for fast, cheap agentic coding at $0.20/$1.50. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both Claude Fable 5 and Grok Code Fast 1 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 Grok Code Fast 1 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 Grok Code Fast 1 leans toward fast, cheap agentic coding at $0.20/$1.50, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, Claude Fable 5 or Grok Code Fast 1?
Grok Code Fast 1 is cheaper — $10/$50 per 1M tokens vs $0.2/$1.5 per 1M tokens, roughly 50× apart on input.
Which has the bigger context window?
Claude Fable 5 — 1M vs 256K, about 3.9× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both Claude Fable 5 and Grok Code Fast 1 together?
Yes — a multi-model platform like LumiChats gives you Claude Fable 5, Grok Code Fast 1 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 Grok Code Fast 1?
Claude Fable 5 — released June 9, 2026, about 10 months after Grok Code Fast 1.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.