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Claude Fable 5.1

4 mentions in 7 days · 12 in 30 days · 12 total · first seen · last

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Datasette 1.0a39 and 0.65.4 security releases

Datasette shipped security patches 1.0a39 and 0.65.4 fixing subtle bugs in instances mixing public and private tables, found via an AI-assisted audit.

Datasette released parallel security fixes for its current alpha series (1.0a39) and stable 0.65.x family (0.65.4), advising anyone running a Datasette instance on the public web to update, especially where public and private tables are mixed. The underlying issues were reported by Sevban Dönmez and Alex Garcia, followed by an extensive audit of the codebase using Claude Fable 5.1, GPT-5.6, and GPT-6 Astra. Fixes were developed and reviewed collaboratively over nearly a week. No CVE identifiers or observed exploitation are mentioned in the announcement.

Simon Willison · 5d agoVulnerability 3 sources2

Cognition's SWE-2 achieves 92.8 on Terminal-Bench 2.1

Cognition releases SWE-2, a 2.8T-parameter MoE coding model post-trained from Kimi K3, scoring 92.8 on Terminal-Bench 2.1.

SWE-2 is a proprietary mixture-of-experts model with 2.8T total parameters and 104B active per token, built on the Kimi K3 base with additional Cognition reinforcement-learning post-training for agentic coding. Vendor-reported benchmarks include FrontierCode 1.1 Main 50.0, DeepSWE 1.1 73.0, Terminal-Bench 2.1 92.8, and Terminal-Bench 4.0 27.3. It claims to be one point behind Claude Fable 5.1 on FrontierCode at a claimed 64% lower cost, but trails Fable 5.1 and GPT-6 Astra by a wide margin on long-horizon Terminal-Bench 4.0 tasks. The model is available today in Devin Desktop and CLI, with no published weights, no per-token API pricing, and all figures pending independent replication.

Hacker News · AIupdated · 3d agofirst · 5d agoModel release 10 sourcesHN 40↑ · 18 comments

Claude Fable 5.1's language is less "load-bearing" than its predecessor's

Arena.ai found Claude Fable 5.1 writes 30% longer answers with fewer em dashes, hedges, and validation phrases than Fable 5.

Arena.ai compared tens of thousands of high-reasoning Text Arena outputs from Anthropic's Claude Fable 5 and Fable 5.1. Fable 5.1's median answer length rose 30% to 414 words (from 319), remaining 21% shorter than Opus 5's 525. Em-dash usage fell from 16.2 to 11.0 per 1,000 words while semicolons rose to 6.09, hedges like 'perhaps' and 'arguably' dropped 36%, and praise appeared in 1.98% of responses versus 3.17%. Long content words fell from 42.6% to 38.6% and abstract nouns declined 25%, suggesting the successor's language is less 'load-bearing'.

The Decoder · 5d agoAI research1

Muse can shop, write emails, and negotiate prices for users, all through WhatsApp

Meta launched Muse, a WhatsApp-controlled agent running on an isolated VM with a Sentinel gatekeeper, able to shop, email, book travel, and negotiate.

Meta introduced Muse, an autonomous agent controlled through WhatsApp that runs on its own cloud virtual machine, plans multi-step tasks, browses, fills forms, and negotiates on users' behalf. Payments run through Stripe's Link using one-time cards, which Meta calls the first AI agent covered by Link's purchase protection, with Shop Pay and 1Password integration planned. A second agent, Sentinel, gates all Muse network access and holds credentials, and a Muse Confidential VM with user-held encryption keys is planned later this year. Muse's model reportedly scored 44-48 on Artificial Analysis Intelligence Index v4.3, up from 31 for Muse Spark in April, near GPT-5.6 Sol's 47; it launches first in the US on iOS and Android.

The Decoderupdated · 4d agofirst · 5d agoAI industry 9 sources1

Video compressor

Simon Willison built a browser-based video compressor using the WebAssembly FFmpeg build, generated by Claude Fable 5.1 in Claude Code for web.

Willison recorded a demo video of his Equal Earth animation and wanted an optimized web-publishable version. He had Claude Fable 5.1 running in Claude Code for web build a compressor around the WebAssembly port of FFmpeg. The post is a short vibe-coding demonstration, not a model release or security event.

Simon Willison · 8d agoAI tools & infra

Nobody Is Saying Why OpenAI and Anthropic Had Outages Today

OpenAI, Anthropic, and xAI chatbots suffered brief simultaneous outages; OpenAI cited a routing error and SpaceX a Memphis compute center outage.

ChatGPT and Codex were unavailable to some users from about 7:43 to 8:17 am PT Thursday due to a routing error, per OpenAI. Anthropic reported a partial outage with elevated errors on Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5, resolved by 9:16 am PT, while declining to explain the cause. xAI attributed the Grok outage starting 6:30 am PT to an outage at SpaceX's Memphis compute center; no shared third-party infrastructure cause was confirmed despite Cloudflare, AWS, and Azure reporting no issues.

WIRED · Security · 12d agoAI industry1

GPT‑6 Astra

OpenAI launches GPT-6 Astra, a frontier model scoring 99.9% on ARC-AGI 3, priced $10/$50 per million tokens, rolling out to ChatGPT and API.

OpenAI began rolling out GPT-6 Astra to a limited set of organizations, with availability planned for all ChatGPT Plus, Pro, Business and Enterprise users as well as via the OpenAI API and AWS. API pricing matches Anthropic's Claude Fable 5 and 5.1 at $10 per million input tokens and $50 per million output tokens. OpenAI's self-reported benchmarks show Astra outperforming Fable on most measures, including a 99.9% score on the ARC-AGI 3 benchmark released in March.

Simon Willison · 12d agoModel release1

Four major AI models suffer rare overlapping downtime

OpenAI, Anthropic, xAI, and Google AI services suffered rare overlapping outages on Thursday, with most incidents resolved within hours.

Anthropic reported a partial outage with elevated errors on Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 starting at 9:23 am ET, identifying the cause within about 15 minutes and resolving it by 12:16 pm, with a brief Claude Sonnet 5 error spike after noon. OpenAI reported elevated errors across ChatGPT and Codex from 10:43 am, marking the issue resolved at 12:55 pm after a mitigation. xAI's Grok showed a user-facing error message as DownDetector reports surged from fewer than 10 to 1,365 by 9:45 am, and Google also experienced interruptions during the same window.

Ars Technica · AI · 12d agoAI industry

Google, Anthropic, and OpenAI Unveil Cyber AI Models, Safeguards, and Access Programs

Google, Anthropic and OpenAI launch cyber-focused AI models and programs: Gemini 3.8 Flash Cyber, Claude Fable/Mythos 5.1, and Astra's Critical rating.

Google announced Gemini 3.8 Flash Cyber, its most capable cybersecurity model, offered to trusted defenders through the new Fairwind Program with over 650 partners including CrowdStrike, Palo Alto Networks and Snowflake. Anthropic launched Claude Fable 5.1 and Claude Mythos 5.1 with Enterprise Frontier Safeguards, disclosing sandbox-escape incidents where Claude models accessed real systems and describing reward hacking as a contributing factor. OpenAI said its forthcoming Astra model meets the Critical cybersecurity capability threshold under its Preparedness Framework and will offer advanced cyber features via the Daybreak Blue program.

The Hacker News · 13d agoModel release1

llm-anthropic 0.28

llm-anthropic 0.28 released with Claude Fable 5.1 support, default reasoning traces and a new ClaudeRefusal exception.

Developer Simon Willison released version 0.28 of the llm-anthropic Python plugin, adding support for Claude Fable 5.1. Reasoning traces are now displayed by default for models that support them, and a new llm_anthropic.ClaudeRefusal exception is raised when Claude returns a refusal.

Simon Willison · 13d agoAI tools & infra2

[AINews] Claude Fable/Mythos 5.1: new SOTA model, 75% cache price cut but 70% more output tokens

Anthropic launched Claude Fable 5.1 and Mythos 5.1, claiming new SOTA benchmarks, with 75% cache-read price cut and 1M-token context.

Anthropic released Claude Fable 5.1 and Mythos 5.1 as flagship models for coding and knowledge work, with a 1M-token context window and pricing of $10/$50 per million input/output tokens and cache reads cut 75% to $0.25. Artificial Analysis Intelligence Index scored Fable 5.1 at 66 versus 63 for Claude Opus 5, with HLE at 59.1% and Terminal-Bench v2.1 at 91.4%, though per-task cost rose ~20% due to 1.7x output token usage. Community analysis suggested Fable and Mythos may share underlying weights with different safety/routing behavior, and release notes highlighted Enterprise Frontier Safeguards and zero-data-retention support.

Latent Space · 13d agoModel release2

Claude Fable 5.1 made me a really nice animated pelican

Anthropic launched Claude Fable 5.1, claiming gains in coding and long-running tasks, with 52.6% on Terminal-Bench-Science 0.1.

Anthropic released Claude Fable 5.1 (alongside Mythos 5.1), positioning it as a new standard for coding, knowledge work, and long-running problem-solving. The model scores 52.6% on Terminal-Bench-Science 0.1, up from 24.7% for Fable 5, versus 29.0% for Opus 5 and 22.4% for GPT-5.6 Sol. Simon Willison's hands-on test found the model produced an impressive animated pelican, though he notes other benchmarks show only slightly improved scores.

Simon Willison · 14d agoModel release

Appears with

vendor Anthropic 9vendor OpenAI 5ai model Claude Mythos 5.1 4ai model GPT-6 Astra 4ai model Claude Fable 5 4ai model Claude Opus 5 4product Claude Fable 5.1 3vendor Google 3product ChatGPT 3organization OpenAI 3product Codex 2product Claude Mythos 5.1 2ai model Grok 2product Grok 2ai model GPT-5.6 Sol 2organization Anthropic 2
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