TL;DR — On 2026-09-01 Anthropic shipped Claude Fable 5.1 and Claude Mythos 5.1: the same model with two safeguard stacks. Fable 5.1 is generally available. Cache reads cost 75% less. Official notes cover coding, knowledge work, and long-running research — not audio or video. If you need chapters from a long lecture, paste the link; you do not pick claude-fable-5-1.
Paste a long-form video URL — BibiGPT turns it into chapters, a transcript, and follow-up Q&A.
As of 2026-09-08, Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 on 2026-09-01: one model, two safeguard stacks. Fable is GA. Cache reads cost 75% less. Official notes list coding, knowledge work, and long-running research — not audio or video. If you need a lecture turned into searchable notes, paste the link into BibiGPT instead of picking claude-fable-5-1.
A coding and knowledge-work flagship, not a video SKU. Anthropic shipped one underlying model with two safeguard stacks — then said nothing about audio or video.
Claude Fable 5.1 and Claude Mythos 5.1 are the same model. Fable 5.1 is generally available. Mythos 5.1 is limited to trusted-access programs for cybersecurity and life sciences. Model ID on the API: claude-fable-5-1.
Input and output stay $10 / $50 per 1M tokens, same as Fable 5. Cache reads now cost $0.25 per 1M tokens — 75% less. Anthropic estimates about 25% cheaper on typical workloads and up to about 45% on highly agentic work.
Official notes highlight coding, knowledge work, Terminal-Bench-Science 52.6% (Fable 5: 24.7%), and agentic research. Audio and video are not listed. Do not write Fable into a transcription stack.
A cheaper, stronger research model helps teams that already run Claude themselves. It does not replace a product that files chapters, a transcript, and follow-up Q&A for a human.
Paste a YouTube, lecture, or podcast URL, get chapters and a transcript. The point of a video assistant is the artifact — not a model ID on an API dashboard.
Fable 5.1 defaults to High effort in Claude Code and Medium on Claude.ai. Those are agent-loop knobs. A 90-minute course still needs timestamps, export, and a place to ask follow-up questions.
Enterprise Frontier Safeguards store monitoring data in customer-controlled cloud infrastructure and roll out in phases this fall. Eligible customers can use Fable 5.1 with zero data retention until then. That is an enterprise path, not a public video model.
Headline shifts from Anthropic's 2026-09-01 announcement.
Fable 5.1 and Mythos 5.1 share one underlying model. Fable is generally available. Mythos is trusted-access only for cybersecurity and life sciences. Model ID: claude-fable-5-1. Official notes do not name audio or video.
List price stays $10 / $50 per 1M input/output tokens. Cache reads drop to $0.25 per 1M tokens. Anthropic estimates about 25% cheaper on typical workloads and up to about 45% on highly agentic work.
Terminal-Bench-Science 0.1: Fable 5.1 scores 52.6% versus Fable 5 at 24.7% in Anthropic's setup. Terminal-Bench 4.0: 55.8% (Mythos 5.1 60.9%) versus Fable 5 at 42.0%. These are agentic research and coding benches, not video scores.
Enterprise Frontier Safeguards store monitoring data in customer-controlled cloud infrastructure. Rollout starts this fall. Until EFS is available, eligible customers can use Fable 5.1 with zero data retention.
The announcement covers coding, knowledge work, and scientific research. It does not list audio or video input. A 90-minute lecture still needs timestamps and export. That is the BibiGPT path, not a Fable integration.
Where the SKU matters — and where a summarizer is the actual product.
Use Fable 5.1 on your own agent traces for coding, research, or document drafts. Then still dump the finished lecture into BibiGPT so humans get chapters instead of a raw token dump. That is two products, not one integration.
A 90-minute course video does not need a model ID. Paste the URL, export the transcript, ask follow-up questions. That is the BibiGPT path — a substitute workflow, not a Fable or Mythos integration.
For a three-hour interview you want searchable notes, then an agent that can cite those notes. Transcribe and summarize in BibiGPT first. Point an existing Agent skill at that artifact. Do not pretend BibiGPT has wired Fable 5.1.
The summarizer is the product. The other URLs keep same-week model launches from colliding.
Paste a long-form URL. Get chapters, a transcript, and follow-up Q&A.
The podcast-shaped tool for long interviews and shows.
Prior Claude family coverage — keep Opus intent on its own URL.
Same-week OpenAI work-model SKU. Official card also skips audio and video.
Launch claims come from Anthropic's own announcement and model page plus independent coverage.
On 2026-09-01 Anthropic introduced Claude Fable 5.1 and Claude Mythos 5.1 as the same model with different safeguards. Fable 5.1 is generally available. Cache reads cost 75% less ($0.25 per 1M tokens). Typical workloads about 25% cheaper; highly agentic work up to about 45%. Terminal-Bench-Science 52.6% versus Fable 5 at 24.7%.
Anthropic — Introducing Claude Fable 5.1 and Claude Mythos 5.1 (2026-09-01) ↗The Claude Fable 5.1 model page lists release date 2026-09-01, model ID claude-fable-5-1, 1M context, 128K max output, $10 / $50 per 1M input/output tokens, cache reads $0.25 per 1M tokens, and knowledge cutoff June 2026.
Claude API — Claude Fable 5.1 model page ↗TechCrunch reported the 2026-09-01 Fable / Mythos 5.1 launch as twinned versions of Anthropic's most advanced model, with lower token cost and fewer false-positive safeguard blocks. Fable is unrestricted and available that day; Mythos stays partner-only for cyber and life-sciences research.
TechCrunch — Anthropic's new Fable release is cheaper, less restrictive (2026-09-01) ↗VentureBeat reported the same-day launch with a 75% cut in Fable cache-read pricing and the Enterprise Frontier Safeguards architecture for monitoring data stored in customer-controlled infrastructure.
VentureBeat — Claude Fable 5.1 and Mythos 5.1 cache-read cut (2026-09-01) ↗Claude Fable 5.1 is Anthropic's generally available coding and knowledge-work model launched on 2026-09-01. It is the same underlying model as Claude Mythos 5.1, with a stricter public safeguard stack. Official materials do not list audio or video capability.
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Paste a long YouTube, lecture, or podcast URL into BibiGPT. You get chapters, a transcript, and follow-up Q&A — without picking Claude Fable 5.1, Claude Mythos 5.1, or a Claude API SKU.
