Fable 5.1

Anthropic has released Claude Fable 5.1, according to Ben's Bites, which writes that the model is the best available now. The newsletter said that instead of a clear quality jump, it found the model faster and easier to talk to over 24 hours of use. Fable 5.1 has a new system prompt that bans it from repeating song lyrics and copyrighted logos and tweaks its response style.

Anthropic also reduced the cost of caching inputs for Fable by 75%, making API usage about 25% cheaper than before, the newsletter said. Among things people are building with Fable, it listed Mario and GTA-style games and 3D rendering of a house using code in Blender.

The newsletter also reported that OpenAI's Astra is coming soon, with rumours saying it could arrive the same day. It named two more new models, Gemini 3.8 Flash and Muse Spark 1.3, saying both are impressive, have the same base price and similar performance, and framing the question as who can subsidise more tokens. Flash 3.8 comes at 50% off for the rest of the year, while Meta is giving a 90% cut in exchange for your data, according to the newsletter.

Separately, the newsletter described another new Meta model, Muse Voice transcribe, as looking really insane for transcription use cases, and said it wished the model were open-source.

In other items, the newsletter said Gemini models can now decide which parts of a video are worth watching. Rather than sampling a video at a fixed frame rate, they search across frames, audio and transcripts for the moments they need, using 88% fewer tokens, costing up to 66% cheaper and with a minor bump in accuracy on benchmarks, it said. It also reported that Inworld built Realtime TTS-2 for the next wave of consumer apps, which it said takes three things: text-based voice design, sub-100ms latency at P99, and one voice identity across 200+ languages.

The newsletter also noted Claude Code/Cowork can now use your computer in the background while you do other work, just like Codex; previously Claude would take over the computer, making it unusable while it worked. It said WebMCP adds tools agents can use for any action you can take on a website, versus having to use the UI, and that Vercel's agent-browser now uses WebMCP if present and falls back to clicking around the UI.