Breaking

Anthropic Accelerates Model Releases With Opus 5.5 Leak and Fable 5.1 in Claude Code

September 21, 2026 at 05:05 EDT

Foundation Models
Software Dev & Coding

Anthropic is poised to release new flagship and mid-tier AI models in rapid succession, marking an aggressive competitive push against OpenAI in the high-stakes model release cycle. Leaked documentation suggests Claude Opus 5.5—codenamed claude-wafer-eap—could launch as early as Tuesday, September 22, with a reported 20% price reduction and significant improvements in coding and 3D generation capabilities compared to the existing Opus 5.

Anthropic Model Race

Opus 5.5 Rumor vs. Fable 5.1 Reality

Anthropic accelerates model releases with leaked Opus 5.5 specs and confirmed Fable 5.1 deployment in Claude Code.

Opus 5.5 (Leaked)

$4/$20

Per million tokens (20% cheaper than Opus 5 at $5/$25)

Fable 5.1 Cache

75% Off

Prompt cache read pricing cuts costs on repeated queries

Opus 5 Benchmark

43.3%

Frontier-Bench score, outperforms Fable 5

Model Tier Comparison

Opus 5
$5/$25

Opus 5.5
(Expected)

Fable 5.1
$10/$50

Stacked cost comparison: Opus 5 baseline costs $5/$25; rumored Opus 5.5 undercuts at $4/$20; premium Fable 5.1 remains $10/$50 but improves via cache savings.

Developer Tradeoff: Opus 5 outperforms Fable 5.1 on several benchmarks at half the per-token cost, but Fable 5.1's improved reasoning and 75% cache-read savings appeal to teams running repeated analysis on large documents.

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