Anthropic launches Fable 5.1 AI model with lower costs

Anthropic on Tuesday released Claude Fable 5.1, a new AI model that the company says delivers stronger coding performance at a lower price than its predecessor, arriving as a closely watched index of AI token prices fell to record lows.

Cheaper Cache Reads, Stronger Benchmarks

Fable 5.1 costs roughly 25% less than Fable 5 for typical workloads, with savings reaching up to 45% for complex coding tasks, according to Anthropic's announcement. The price reduction comes from a 75% cut to cache read costs, now $0.25 per million tokens, while standard input and output pricing remains unchanged at $10 and $50 per million tokens, respectively.bloomberg+1

On benchmarks, the model scored 55.8% on Terminal-Bench 4.0, an agentic coding evaluation, compared with 42% for Fable 5 and 52.3% for OpenAI's GPT-5.6 Sol. Early-access partners offered pointed praise: the investment firm Millennium said Fable 5.1 identified the root cause of a rare software crash that had eluded the firm's engineers for years, while Cognition, the company behind the AI coding agent Devin, said it would migrate its traffic from Opus 5 to Fable 5.1 on launch day.anthropic

Token Price Deflation Puts Pressure on AI Providers

The release lands as the LLM Token Expenditure Index, tracked by intelligence firm Silicon Data, dropped to 97 cents per million tokens on Monday — its lowest reading since the index's creation late last year and less than half its summer peak. The decline has been fueled in part by the rise of open-source Chinese models such as Moonshot's Kimi K3, as well as price cuts from OpenAI on its GPT-5.6 models and the spread of dynamic pricing across frontier labs, according to Syz Group investing chief Charles-Henry Monchau.cnbc+1

The slide could complicate the financial outlook for both Anthropic and OpenAI, which confidentially filed for initial public offerings this summer. "Token deflation compresses the revenue line while compute commitments stay fixed," Monchau wrote.cnbc

Data Retention Shift Addresses Enterprise Pushback

Alongside the model launch, Anthropic introduced Enterprise Frontier Safeguards, a system that stores customer data in the customer's own cloud infrastructure rather than on Anthropic's servers. The change addresses concerns that had surfaced after the company imposed a 30-day data retention requirement on enterprise traffic for its Fable and Mythos models in June. Reuters Thomson Reuters Corporation ↗ 5.56% reported in August that Anthropic had been coordinating with more than 100 customers, including Salesforce ↗ 2.92%, to develop the new system. Eligible customers can use Fable 5.1 with zero data retention immediately, with the full safeguards system rolling out in phases beginning this fall.reuters+1

Shares of major technology companies were lower on Tuesday. The Nasdaq Composite slid nearly 1%, while the S&P 500 ticked down 0.4%.cnbc