Anthropic releases Claude Fable 5 and Claude Mythos 5 — first generally available Mythos-class model
On June 9, 2026 Anthropic released Claude Fable 5, a Mythos-class model with safeguards for general use, and Claude Mythos 5, the same model with fewer safeguards for Project Glasswing partners and selected biology researchers. Priced at $10/$50 per million tokens, it was the most capable model Anthropic had made broadly available. Three days later US export controls forced Anthropic to suspend access.
Key facts
- Released June 9, 2026; ids claude-fable-5 and claude-mythos-5; $10 input / $50 output per 1M tokens
- Context 1M tokens, 128K output; always-on adaptive thinking
- Three classifier systems (cyber, bio/chem, distillation); blocked queries answered by Claude Opus 4.8 instead
- Mythos 5 restricted to Project Glasswing partners and select biology researchers
- Stripe reported a 50-million-line codebase migration done in one day (vs ~2 months manually)
- Completed Pokémon FireRed using vision alone (Anthropic)
- Access suspended June 12 under US export controls; restored globally July 1, 2026
What happened
Anthropic said on May 28 (Opus 4.8 launch) that it expected to bring Mythos-class models to all customers "in the coming weeks". Fable 5 was that release. Anthropic said its capabilities exceeded any model it had previously made generally available, with state-of-the-art results on nearly all benchmarks it tested, across software engineering, knowledge work, vision and science. The safety design routes risky cyber, bio and distillation queries to Opus 4.8. Anthropic also introduced 30-day data retention for safety monitoring.
Why it matters
This was the first time the class of model Anthropic had withheld in April (Mythos Preview) became available to the public. Within three days it also became the first frontier model pulled from the market by government export controls.
Changelog
- 2026-09-29: created
- 2026-09-29: added post link(s) (1) from Anthropic posts cluster
Videos (8)
Introducing Claude Fable 5
Anthropic · 2026-06-09 · officialThis is an announcement video from Anthropic introducing Claude Fable 5, presented by Alex Albert (Research Product Management) and Angeli Jain (Safeguards Product Management). The presenters discuss why a previous iteration (Claude Mythos Preview) was withheld from public release due to cybersecurity risks, and how…
Claude Fable 5 Took 60 Hours to Build This Game
RemakeBench · 2026-09-10 · ai-madePresented by the AI-development channel RemakeBench, this video documents a 67-hour autonomous game development sprint expanding a simple 7-hour "walking simulator" prototype into a full third-person stealth action samurai game. Orchestrated by GPT-5.6 Sol with Anthropic's Claude Fable 5 performing the core…
I Tested Fable 5.1 vs Fable 5 vs Opus 5 (Cost/Speed/Design)
Brock Mesarich | AI for Non Techies · 2026-09-08 · reviewIn this video, presenter Brock Mesarich conducts a hands-on benchmark comparing Anthropic's Claude Fable 5.1 against Claude Fable 5, Claude Opus 5, and OpenAI's Codex Sol / Terra models. He evaluates each model across three effort tiers (Low, High, and Max) on the same multi-step task: generating photorealistic…
Claude Fable 5.1 Should Not Be This Good (way better than Fable 5)
Zo · 2026-09-08 · communityIn this video, creator Zo tests Anthropic’s newly released Claude Fable 5.1 by challenging the model to write code for three playable games from scratch without external game engines. Across single-file HTML implementations, Fable 5.1 builds a browser voxel engine modeled after Minecraft, a 2D lane-defense clone of…
AI Made This Entire Video by Itself... (Claude Fable 5)
Dan Dingle · 2026-07-02 · ai-madeContent creator Dan Dingle tests Anthropic's Claude Fable 5 by prompting the model to generate synthetic video clips using "Seedance 2.0," create an AI clone of his face and voice to react to them, and automatically edit the final video in his signature style. The real Dan Dingle watches and comments on the…
Claude Fable 5: Better Than Opus 4.8?
Teacher's Tech · 2026-07-01 · communityJamie Keet from Teacher's Tech presents an independent hands-on evaluation of Anthropic's Claude Fable 5, comparing it head-to-head against Claude Opus 4.8. Through four practical business tests—analyzing charts in PDFs, auditing spreadsheet calculations, synthesizing multi-file launch memos, and testing domain…
More videos (2)
- This AI Short Drama Was Made With Claude Mythos + Higgsfield MCP ($10) TOAST · 2026-06-16
- Claude Fable 5 Made This Entire Video By Itself. Nate Herk | AI Automation · 2026-06-12
All videos with Gemini's descriptions: videos · llms-full.txt
Related posts (3)
- 8 Predictions for the Era of Continual Learning Dwarkesh Patel @dwarkesh_sp · blog · 2026-08-07
Dwarkesh's main 2026 essay predicts that once continual learning arrives it will make current safety regulation obsolete and give the leading labs strong moats. Zvi and Nathan Lambert responded. - Anthropic: US export-control directive suspends Fable 5 and Mythos 5 access for all foreign nationals Anthropic @AnthropicAI · x · 2026-06-12
The first known case of a US export-control order forcing a lab to take a released frontier model offline for all users. - Introducing Claude Fable 5: a Mythos-class model made safe for general use Claude @claudeai · x · 2026-06-09
The launch post for Anthropic's first publicly available Mythos-class model, which the US government suspended three days later.
Related events
- US export controls force Anthropic to suspend Claude Fable 5 / Mythos 5; access restored July 1 ★★★★
- Anthropic reveals Claude Mythos Preview, withholds it over cyber risk and launches Project Glasswing ★★★★★
- Anthropic releases Claude Fable 5.1 and Claude Mythos 5.1 ★★★★★
- Anthropic releases Claude Opus 4.8 with cheaper fast mode and Claude Code "dynamic workflows" ★★★
- Dario Amodei publishes "Policy on the AI Exponential", calling for binding frontier-AI regulation ★★★
- "Claude Fable 5 Made This Entire Video By Itself": the agent-made YouTube video becomes a genre ★★
- Claude Fable 5 finds a counterexample to the Jacobian conjecture in dimension 3 ★★★★★
- Anthropic releases Claude Opus 5 — near-Fable-5 intelligence at half the price ★★★★
- Anthropic releases Claude Opus 5.5 — Fable-5.1-level performance at $4/$20, first model of the Claude 5.5 family ★★★★★
Sources (7)
- officialClaude Fable 5 and Claude Mythos 5 (Anthropic)
- paperFable 5 / Mythos 5 System Card
- docsIntroducing Claude Fable 5 and Claude Mythos 5 (docs)
- officialClaude Fable product page
- discussionWikipedia: Claude Mythos
- videoIntroducing Claude Fable 5 (official video)
- officialClaude on X: Introducing Claude Fable 5
id: 2026-06-09-claude-fable-5-mythos-5 · updated 2026-09-29 · open in the interactive timeline