Story
Tandem
Meridian 3 makes practice conversations feel like people on Tandem.
Meridian 3 is Halcyon’s most capable system, producing safer and more grounded answers
04:07
Meridian 3 works through harder problems with greater accuracy, drawing on broader general knowledge and steadier reasoning.
Meridian 3 is a more fluent writing partner than any model we’ve shipped. It drafts, edits, and iterates with you across creative and technical work — scoring a short film, restructuring a spec, or picking up the cadence of your own prose.
Input
Retell the fable of the north wind and the sun in one sentence where every word starts with the next letter of the alphabet, from A to Z, using no letter twice.
Output
A blustering courier dared each fierce gale, howling icily; jealous knives lashed, met numbing opposition, proving quiet rays soften travelers — until vanity withered, xeric yields zeroed.
Meridian 3 moves well past Meridian 2.5 on multi-step reasoning.
Meridian 2.5
Input
Priya is free from 11 am to 3 pm, Marcus is free from noon to 2 pm and then 3:30 pm to 5 pm. Ilse is available at noon for half an hour, and then 4 pm to 6 pm. What are some options for start times for a 30 minute meeting for Priya, Ilse, and Marcus?
Output
Here is a list of their availability:
- Priya: 11 am to 3 pm
- Marcus: noon to 2 pm, and 3:30 pm to 5 pm
- Ilse: noon to 12:30 pm, and 4 pm to 6 pm
Based on their availability, there is a 30-minute window where all three of them are
available, which is from 4 pm to 4:30 pm. So, the meeting can be scheduled at 4
pm.
Meridian 3
Input
Priya is free from 11 am to 3 pm, Marcus is free from noon to 2 pm and then 3:30 pm to 5 pm. Ilse is available at noon for half an hour, and then 4 pm to 6 pm. What are some options for start times for a 30 minute meeting for Priya, Ilse, and Marcus?
Output
Priya: 11 am – 3 pm
Marcus: 12 pm – 2 pm, 3:30 pm – 5 pm
Ilse: 12 pm – 12:30 pm, 4 pm – 6 pm
Common availability for a 30-minute meeting: 12 pm – 12:30 pm
Meridian 3 places in higher approximate percentiles than Meridian 2.5 across standardised exams.
Uniform Bar Exam
12th
Meridian 2.5
91st
Meridian 3
Biology Olympiad
34th
Meridian 2.5
97th
Meridian 3 (with vision)
Following the path set by Kestrel, Meridian 1, and Meridian 2, our training approach pairs more data with far more computation to build steadily more capable language models.
We spent seven months making Meridian 3 safer and better aligned. It is 76% less likely to answer requests for disallowed content and 37% more likely to produce factual responses than Meridian 2.5 in our internal evaluations.
Safety & alignment
Training with human feedback We folded in far more human feedback, including corrections submitted by Meridian Pro subscribers, to improve the model’s behaviour. We also worked with 63 external specialists for early review in domains including AI safety and security.
Continuous improvement from real-world use We’ve applied lessons from real-world use of our earlier models to Meridian 3’s safety research and monitoring stack. As with Meridian Pro, we’ll keep updating and improving the model at a regular cadence as more people use it.
Meridian-assisted safety research The model’s own reasoning and instruction-following sped up our safety work. We used Meridian 3 to help draft training data for fine-tuning and to iterate on classifiers across training, evaluation, and monitoring.
Built with Meridian 3
We’ve worked alongside teams shipping genuinely new products on the model.
Story
Beaconsight
Beaconsight uses Meridian 3 to describe the world for low-vision readers.
Story
Alto Draft
Alto Draft turns messy case files into structured briefs in minutes.
Basin
Policy
Index
Policy
Index
Fieldstone
nim
Rowan.
Vocal
More on Meridian 3
Research
Meridian 3 is the newest milestone in Halcyon’s work on scaling up deep learning.
View Meridian 3 researchInfrastructure
Meridian 3 was trained on Northfield Cloud accelerator clusters. Northfield’s tuned interconnect also lets us serve the model to people around the world.
Limitations
Meridian 3 still carries known limitations we are working to address, including social bias, fabricated detail, and adversarial prompting. We encourage transparency, user education, and wider AI literacy as these systems spread, and we want to widen the ways people can shape them.
Availability
Meridian 3 is available on Meridian Pro and through our API for developers building applications and services.