Matthew Finlayson
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mattf.nl
Matthew Finlayson
@mattf.nl
NLP PhD @ USC
Previously at AI2, Harvard
mattf1n.github.io
Pinned
We discovered that language models leave a natural "signature" on their API outputs that's extremely hard to fake. Here's how it works 🔍

📄 arxiv.org/abs/2510.14086 1/
Every Language Model Has a Forgery-Resistant Signature
The ubiquity of closed-weight language models with public-facing APIs has generated interest in forensic methods, both for extracting hidden model details (e.g., parameters) and for identifying...
arxiv.org
Reposted by Matthew Finlayson
Gordon ramsey: Excuse me darling, what’s going on in there
LLM architect: the uhh model’s outputs lie on a high-dimensional ellipse
Gordon: on a high-dimensional ellipse?
Architect: correct, a high-dimensional ellipse
Gordon: fuck me. Ok thank you darling
October 18, 2025 at 7:21 PM
We discovered that language models leave a natural "signature" on their API outputs that's extremely hard to fake. Here's how it works 🔍

📄 arxiv.org/abs/2510.14086 1/
Every Language Model Has a Forgery-Resistant Signature
The ubiquity of closed-weight language models with public-facing APIs has generated interest in forensic methods, both for extracting hidden model details (e.g., parameters) and for identifying...
arxiv.org
October 17, 2025 at 5:59 PM
I didn't believe when I first saw, but:
We trained a prompt stealing model that gets >3x SoTA accuracy.
The secret is representing LLM outputs *correctly*

🚲 Demo/blog: mattf1n.github.io/pils
📄: arxiv.org/abs/2506.17090
🤖: huggingface.co/dill-lab/pi...
🧑‍💻: github.com/dill-lab/PILS
June 23, 2025 at 8:49 PM
Reposted by Matthew Finlayson
I wish the ML community would stop trying to turn every technique into a brand name. Just give the thing a descriptive name and call it what it is.

Forced backronyms like this are counter productive.
too distracted by this to read the actual content
June 11, 2025 at 3:10 PM
It appears that the only fonts with optical sizes that work with pdflatex are the computer/latin modern fonts. I would kill for a free pdflatex-compatible Times clone with optical sizes so my small text can look good in ArXiv/conference submissions.
June 4, 2025 at 4:05 PM
If you are writing a paper for #colm2025 and LaTeX keeps increasing your line height to accommodate things like superscripts, consider using $\smash{2^d}$, but beware of character overlaps.
March 16, 2025 at 2:32 AM
This project was made feasible by the excellent open-source LLM training library @fairseq2.bsky.social; I highly recommend giving it a look! It made both SFT and DPO a piece of cake 🍰
🧵 Adapting your LLM for new tasks is dangerous! A bad training set degrades models by encouraging hallucinations and other misbehavior. Our paper remedies this for RAG training by replacing gold responses with self-generated demonstrations. Check it out here: https://arxiv.org/abs/2502.10
February 25, 2025 at 9:58 PM
🧵 Adapting your LLM for new tasks is dangerous! A bad training set degrades models by encouraging hallucinations and other misbehavior. Our paper remedies this for RAG training by replacing gold responses with self-generated demonstrations. Check it out here: https://arxiv.org/abs/2502.10
February 25, 2025 at 9:55 PM
Putting together an unofficial usc Beamer template, I noticed that the USC style guide lists 4 formats for “cardinal red” but each of them is different:

PMS 201 C is #9D2235
CMYK: 7, 100, 65, 32 is #A1003D
RGB: 135, 27, 30 is #991B1E
HEX: #990000

Is this normal? The CMYK is especially egregious.
December 12, 2024 at 5:16 PM
In Vancouver for NeurIPS but don't have Taylor Swift tickets?

You can still spend the day going through our tutorial reading list:
cmu-l3.github.io/neurips2024-...

Tuesday December 10, 1:30-4:00pm @ West Exhibition Hall C, NeurIPS
December 9, 2024 at 1:43 AM
Curious about all this inference-time scaling hype? Attend our NeurIPS tutorial: Beyond Decoding: Meta-Generation Algorithms for LLMs (Tue. 1:30)! We have a top-notch panelist lineup.

Our website: cmu-l3.github.io/neurips2024-...
December 6, 2024 at 5:18 PM
Reposted by Matthew Finlayson
What's that? A fully open LM competitive with Gemma and Qwen*?

Happy to have helped a bit with this release (Tulu 3 recipe used here)! OLMo-2 13B actually beats Tulu 3 8B on these evals, making it a SOTA fully open LM!!!

(*on the benchmarks we looked at, see tweet for more)
Meet OLMo 2, the best fully open language model to date, including a family of 7B and 13B models trained up to 5T tokens. OLMo 2 outperforms other fully open models and competes with open-weight models like Llama 3.1 8B — As always, we released our data, code, recipes and more 🎁
November 26, 2024 at 8:54 PM
These folks have had a huge impact on my research
A starter pack for research on Formal Languages and Neural Networks!

go.bsky.app/eKG7Ua
November 26, 2024 at 6:39 PM
Reposted by Matthew Finlayson
#socalnlp is the biggest it's ever been in 2024! We have 3 poster sessions up from 2! How many years until it's a two-day event?? 🤯
November 22, 2024 at 9:50 PM
This is niche but the LLM360 logo always reminds me of the 2014 iOS game Oquonie
November 22, 2024 at 7:23 PM
Hottest new research challenge: find the lost LLM head!
We actually have all the weights.... except the LM head for this blursed checkpoint. Don't ask.
oh btw, we accidentally deleted our "BEST" Tulu 3 70B model. This one was only our second best model, so if we cook up an even better one again, we'll give it to the people.

405B is being planned 🤞🤡
November 22, 2024 at 7:30 AM
Everyone follow Sean! He's been working nonstop to perfect our upcoming NeurIPS tutorial
I was honored to give a talk at Simons Institute on inference-time algorithms and meta-generation!

simons.berkeley.edu/talks/sean-w...

It was a sneak-preview subset of our NeurIPS tutorial:
cmu-l3.github.io/neurips2024-...
November 22, 2024 at 12:31 AM
Reposted by Matthew Finlayson
As "X is all you need" and "Transformers are Y" paper titles have died, I propose that we similarly retire:

- X of thought
- Chain of Y
- "[topic] a comprehensive survey" where [topic] is exclusively post-2022 papers
- Claims of reasoning/world model/planning based on private defns of one
November 21, 2024 at 10:20 AM
Reposted by Matthew Finlayson
I made a map! Thank you to my 2019 self for providing the code github.com/mattf1n/Reli...
November 17, 2024 at 3:28 PM
Today I learned you can add a citation link to your GitHub repo. citation-file-format.github.io
citation-file-format.github.io
November 15, 2024 at 6:52 PM
Reposted by Matthew Finlayson
Oh my, USC is an empire!
USC NLP folks are on Bluesky!
Follow my amazing colleagues here

go.bsky.app/KUwSZ6W
November 15, 2024 at 12:02 AM
Reposted by Matthew Finlayson
And we're having a great time at #EMNLP2024, come talk to us!
November 14, 2024 at 11:34 PM
I’m proud of this tikz drawing I made today for our upcoming NeurIPS tutorial on decoding (our paper: arxiv.org/abs/2406.16838)
November 14, 2024 at 5:02 AM
Reposted by Matthew Finlayson
I'll be presenting "Distributional Properties of Subword Regularization" with @zouharvi.bsky.social and Naoaki Okazaki at #EMNLP.

arxiv.org/abs/2408.11443

The idea is that stochastic variants of BPE/MaxMatch produce very biased tokenization distributions, which is probably bad for modeling.

#NLP
November 9, 2024 at 5:06 PM