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Anthropic Releases Claude Fable 5.1 on Claude and Claude Code at Fable 5 Prices

September 1, 2026 at 14:17 EDT

Foundation Models
Software Dev & Coding
AI Agents

Anthropic has released Claude Fable 5.1 on Claude and Claude Code, matching Claude Fable 5's $10-per-million-input and $50-per-million-output prices while cutting cache-read costs by 75% to $0.25 per million tokens. A twin model, Claude Mythos 5.1, offers the same capabilities with looser safeguards and is limited to trusted access programs for cyberdefense and the life sciences.

September 1, 2026 · Anthropic

Claude Fable 5.1 is live — same list price, cheaper cache, higher agent scores

Anthropic's generally available Mythos-class successor is on Claude and Claude Code. Input and output stay at $10 / $50 per million tokens; cache reads fall 75% to $0.25, and Terminal-Bench-Science more than doubles versus Fable 5.

52.6%

Terminal-Bench-Science 0.1

75%

cheaper cache reads

~25%

lower typical token cost

$10 / $50

input / output per MTok

Terminal-Bench-Science 0.1

Accuracy, same unit. Column height is proportional to the score.

22.4%

GPT-5.6 Sol

24.7%

Fable 5

29.0%

Opus 5

52.6%

Fable 5.1

Takeaway: Fable 5.1 more than doubles Fable 5 on this scientific-agent benchmark.

Cache-read price per million tokens

Same unit ($). Four blocks versus one: Fable 5.1 cache reads cost a quarter as much.

$1.00

Fable 5

$0.25

Fable 5.1

Takeaway: Cache hits now cost 75% less, cutting typical token-billed work by about 25% and highly agentic runs by up to about 45%.

What improved

Same $10 / $50 list prices, 75% cheaper cache reads, and higher scores on long-horizon coding, science agents, spreadsheets, and slides. Partners report longer unattended runs and clearer writing.

What still constrains it

Pro still needs usage credits. Max still caps Fable at 50% of weekly limits. The model is slower, is not the default, can fall back to Opus, and drops forced tool use.

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