Drop #18: Fable 5 Returns Globally — and Sonnet 5 Becomes the New Default
A big week on Anthropic's own product surface for a change. On June 30 the company shipped three announcements in a single day: Fable 5 cleared to return worldwide, Claude Sonnet 5 launched as the new default model, and Claude Science became generally available. Two of these directly change what you see in Cowork's model picker. Here is what happened and what to do about it.
Fable 5 Is Back in Cowork
On June 30, Anthropic announced that the US government lifted the export controls that had kept Claude Fable 5 and Mythos 5 suspended since June 12. Fable 5 returned globally on July 1 across the Claude Platform, Claude.ai, Claude Code, and Claude Cowork. For Pro, Max, Team, and select Enterprise plans, Fable 5 is included for up to 50% of weekly usage limits through July 7, after which it is available via usage credits.
The redeployment came with new safeguards. Anthropic says it trained an improved safety classifier that blocks the reported bypass technique in over 99% of cases; when a request to Fable 5 is blocked, it is rerouted to Opus 4.8. The company acknowledges the tighter classifier may flag more benign coding and debugging requests, and says it will keep tuning false positives down.
Alongside the redeployment, Anthropic and partners including Amazon, Microsoft, and Google proposed an industry-wide framework for scoring the severity of AI jailbreaks on four criteria — capability gain, breadth, ease of weaponization, and discoverability — and opened a HackerOne program where researchers can submit cyber jailbreaks they find in Fable 5.
Sonnet 5 Is the New Default for Everyday Work
The same day, Anthropic introduced Claude Sonnet 5, which it calls its most agentic Sonnet yet — performance close to Opus 4.8 at lower prices, and a substantial improvement over Sonnet 4.6 in reasoning, tool use, coding, and knowledge work. Sonnet 5 is now the default model for Free and Pro plans, and is available to Max, Team, and Enterprise users, in Claude Code, and on the Claude Platform at introductory pricing of $2 per million input tokens and $10 per million output tokens through August 31, 2026.
Two details matter for Cowork users. First, Anthropic says it increased rate limits across Chat, Cowork, Claude Code, and the Claude Platform to accommodate the higher token usage of higher effort levels. Second, the safety notes: Sonnet 5 shows lower rates of hallucination and sycophancy than Sonnet 4.6 and is better at resisting hijack attempts in prompt injection attacks — directly relevant if you let Cowork browse the web or read inbound documents on your behalf.
Also This Week: Claude Science
Rounding out the June 30 announcements, Anthropic released Claude Science, an AI workbench for scientists that integrates the tools and packages researchers most often use, produces auditable artifacts, and provides flexible access to computing resources. Not a Cowork feature — but a signal of how quickly Anthropic is spinning up specialized work surfaces on the same models Cowork runs on.
Tip of the Week: Match the Model to the Job
With Fable 5 back in the picker and Sonnet 5 the new default, which model runs your Cowork session is now a real decision. Through July 7, Fable 5 is included for up to 50% of weekly usage on paid plans — so this week is the time to route your heaviest jobs to it.
❌ Weak
Run everything on whatever model is selected, from renaming files to the quarterly analysis.✅ Strong
Keep Sonnet 5 for routine delegation — file cleanup, drafts, connector updates — and switch to Fable 5 for the one big job this week where quality matters most, like a deep research report or a messy cross-connector workflow.The rule of thumb: default model for volume, frontier model for the few tasks you would otherwise have done yourself.
Worth Reading This Week
- → Redeploying Fable 5 - Anthropic - The full timeline of the export-control episode and what changed in the safeguards.
- → Introducing Claude Sonnet 5 - Anthropic - Benchmarks, pricing, and availability details for the new default model.
- → More details on Fable 5's cyber safeguards and our jailbreak framework - Anthropic - The July 2 follow-up on how the classifiers work.
- → Claude Science, an AI workbench for scientists - Anthropic - What the new research surface includes.
Two new options in the model picker and an included-usage window that closes July 7 — this is the rare week where checking your model settings is the highest-leverage thing a Cowork user can do.
Until next time.
— The ClaudeCowork.com team