During pre-release testing, Claude Fable 5.2 and Claude Mythos 5.2...
Claude@claudeai
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Nov 10, 2026
~3 min read
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During pre-release testing, Claude Fable 5.2 and Claude Mythos 5.2 worked on ambitious projects in many different fields. Here are a few.
From a one-paragraph prompt, Fable 5.2 designed three working electronic devices, including this home voice assistant hub.
From a one-paragraph prompt, Fable 5.2 designed three working electronic devices, including this home voice assistant hub.
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Fable 5.2 wrote its own specifications, selected the components, routed the four-layer circuit boards, designed enclosures for 3D printing, and programmed the software.
Each board was ready for manufacture in under a day. All three devices work without any modifications.
Each board was ready for manufacture in under a day. All three devices work without any modifications.
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Read more about how Claude designed these devices: anthropic.com/research/claud…
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Planning and executing the reactions to make a complex molecule (a “route”) is one of the hardest jobs in organic chemistry.
From one image of each of four molecules, with no internet and with code as its only tool, Claude wrote a complete route in about half an hour.
From one image of each of four molecules, with no internet and with code as its only tool, Claude wrote a complete route in about half an hour.
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The model checked its own plan, writing and running code to confirm, atom by atom, that each compound followed from its starting materials.
It replaced reactions that could damage the molecule, and flagged the steps most likely to fail.
It replaced reactions that could damage the molecule, and flagged the steps most likely to fail.
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Our external collaborators rated the work at the level of an early graduate student. The routes haven’t been tested in the lab yet.
The molecules came from unpublished syntheses in the labs of Noah Burns (Stanford), Timothy Newhouse (Yale), and Sarah Reisman (Caltech).
The molecules came from unpublished syntheses in the labs of Noah Burns (Stanford), Timothy Newhouse (Yale), and Sarah Reisman (Caltech).
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Read commentaries from our collaborators on Claude’s performance: www-cdn.anthropic.com/d9fab5459563a7…
The routes for three of the four molecules (none yet tested in a lab) are provided here: www-cdn.anthropic.com/666a6cb5172cbf…
The routes for three of the four molecules (none yet tested in a lab) are provided here: www-cdn.anthropic.com/666a6cb5172cbf…
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MIPLIB is a library of optimization problems, such as how best to schedule airline crews and delivery trucks.
Of 203 open problems, Claude beat the listed mathematical solution in 72 cases, and in 45 cases proved that a solution was optimal.
Of 203 open problems, Claude beat the listed mathematical solution in 72 cases, and in 45 cases proved that a solution was optimal.
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One problem asks how to time 42 trains to cut peak power use. In under two hours, agents beat MIPLIB’s best timetable by 2.6%, and later proved no better timetable exists.
We’ve submitted the solutions to MIPLIB for anyone to check.
We’ve submitted the solutions to MIPLIB for anyone to check.
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Fable 5.2 solved two open problems in theoretical physics related to black holes.
In the first, Fable 5.2 completed a laborious calculation that had gone unsolved for 23 years.
In the first, Fable 5.2 completed a laborious calculation that had gone unsolved for 23 years.
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In 1983, physicists showed that as certain larger theoretical universes heat up, black holes form very abruptly. A calculation to test whether this holds true in a set of incredibly small universes was laid out in 2003.
Fable 5.2 found the transition is abrupt there too.
Fable 5.2 found the transition is abrupt there too.
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In the second physics problem, Fable 5.2 found the exact limit of the simplest version of a 15-year-old technique known as “modular bootstrapping.” The technique is used to rule out candidate theories of quantum gravity in theoretical universes.
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Both physics results are written up in preprints.
On the abrupt transition in very small universes: hexagonmath.org/2611.00175v1
On the exact limit of a technique used to rule out candidate theories of quantum gravity: hexagonmath.org/2611.00174v1
On the abrupt transition in very small universes: hexagonmath.org/2611.00175v1
On the exact limit of a technique used to rule out candidate theories of quantum gravity: hexagonmath.org/2611.00174v1
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Claude Fable 5.2 is available today on all paid plans.
Organizations pursuing beneficial applications in cybersecurity or biomedical research can apply for access to Claude Mythos 5.2.
Read more: anthropic.com/claude-fable-a…
Organizations pursuing beneficial applications in cybersecurity or biomedical research can apply for access to Claude Mythos 5.2.
Read more: anthropic.com/claude-fable-a…
