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Claude Fable 5 Ranks Grok 4.5 as 'Opus-Class' as Prices Diverge Up to 10x

July 8, 2026 at 22:51 EDT

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Anthropic's Claude Fable 5 reportedly classified Grok 4.5, the new model xAI (SpaceXAI brand) released on July 8, 2026, as an "Opus 4.8 or Fable-class model," renewing attention on the performance-versus-cost battle among frontier models.

July 8, 2026 · Frontier Model Watch

Grok 4.5 vs. Fable 5: When Price Beats the Benchmark

xAI's new Grok 4.5 lands 5× cheaper than Anthropic's top-tier Fable 5 — reviving the debate over whether benchmark gaps still matter once you factor in cost per task.

$2 / $6

Grok 4.5 input / output per 1M tokens

$10 / $50

Fable 5 input / output per 1M tokens

<5%

Fable 5 sessions that fall back to Opus 4.8

Output price per 1M tokens

Each block = $6. Taller column = more expensive.

Grok 4.5

$25

Opus 4.8

$50

Fable 5

SWE-Bench Pro — accuracy vs. cost

Fable 580.4%

Opus 4.869.2%

Grok 4.564.7%

On automation tasks (AutomationBench-AA) the ranking flips: Grok 4.5 leads at 51% at just $0.34/task vs. Fable 5's $1.35/task.

GROK 4.5 — the cost play

Opus-class output at a fraction of the price
Token-efficient for high-iteration agents
Wins on long-running SWE, finance & automation workflows

FABLE 5 — the capability play

Best on long, complex and creative tasks
Safety-first: auto-fallback to Opus 4.8
Premium price and fallback frequency draw criticism

The strategic split

Anthropic prioritizes safety while pushing cutting-edge capability — xAI chases high-volume demand through price-performance. With a 5× price gap, the takeaway is blunt: benchmark leads may matter far less than dollars per task.

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