Hybrid Reasoning Agents: LLM agents that think in latent space, act through text

bhattisatish · 2026-10-18T21:33:25

The code is available at: https://github.com/togethercomputer/HybridAgent

LLM Models and data: https://huggingface.co/collections/togethercomputer/hybridag...

Evaluations: https://arxiv.org/html/2610.18861v1#S5

amluto · 2026-10-18T22:44:28

I wonder how this compares to going all-in: widen the input embedding to fit the output (post-“Hybrid Link”) latent vector and a token embedding and pass both through even when in text mode. After all, you’re paying essentially the full cost of running the latent-mode model while generating text, so why not let it latently reason at the same time?

cwyers · 2026-10-18T21:29:47

Oh cool, it's the Most Forbidden Technique

k__ · 2026-10-18T21:39:19

Care to elaborate?

modeless · 2026-10-18T21:44:21

People at the big labs have been terrified of losing the chain of thought because they currently monitor it to prevent users from using their models in certain ways they consider unsafe or bad for their business. Personally I think chain of thought monitoring is a bad way to do this and obviously needs to be replaced by some way of analyzing the model's activations directly.

Lerc · 2026-10-18T21:51:15

Agreed, having text as a reasoning layer impedes performance while giving a false sense of security.

It could be encoding anything in its adjective choices etc. The same thing that model providers are using for watermarking can used by the model itself for private thought.

km3r · 2026-10-18T22:41:15

It's also one of the major way labs can understand these models. Without the models are significantly harder to understand and align.

airza · 2026-10-18T22:30:36

The “obviously” here is puzzling. It is certainly obvious this would be better but it is not at all obvious how to do so.

FuckButtons · 2026-10-18T22:41:23

That’s certainly the long term goal, but it seems foolish to abandon it without a solution to the problem.

Bluestein · 2026-10-18T22:03:50

Also agreed. Begging for crumbs at the CoS table is impeding cracking the tough nut of MechInterp. And further facing the fascinating and fertile fact that nobody has a clue of how any of these black boxes really work.-

throwaway314155 · 2026-10-18T22:37:32

> hey currently monitor it to prevent users from using their models in certain ways they consider unsafe or bad for their business

Can't they just monitor the text outputs as well?

abecedarius · 2026-10-18T22:04:11

The usual meaning: say you have an interpretability signal that reveals reward hacking or other badness. Your most obvious response is to use that signal as a penalty in training. Doing that is called "the Most Forbidden Technique" because you can expect it to degrade the signal without stopping the badness.

But this doesn't seem to describe the OP, it's a different way to lose monitorability.

jlhawn · 2026-10-18T21:43:19

the chain of thought is not auditable. The best you can do is have another model which later maps the intermediate latent states at every thinking iteration to text describing that latent state, but it's going to be lossy.

haolez · 2026-10-18T21:54:33

But the chain of thought as text can be elusive, no? It might not be related with the actual "reasoning" of the model. There was a paper about this.

measurablefunc · 2026-10-18T22:04:19

This is correct, the decoded text has nothing to do w/ calculations that eventually get decoded into text. It's just a veneer that gives the appearance of legibility.

chabons · 2026-10-18T22:16:24

One of the core claims made in the paper is "To inspect any latent reasoning span, one can easily recover its semantics by mapping each latent step produced by HybridLink to its nearest token embedding, as in Eq. 5". They show some charts to support this.

In doing this however, you lose meaning where the model is expressing combinations of tokens in a vector, and your logging/monitoring outputs just the closest one. You would need another model going through and outputting the full meaning being described (with more than one output token per reasoning token)

I wonder if their observability claims will hold up on a model trained from scratch to reason in latent space.

mycall · 2026-10-18T21:54:09

Isn't this where everything is converging? Binary is more efficient than text for many system, including language.

andsoitis · 2026-10-18T21:59:27

> Binary is more efficient than text for many system, including language.

It is not necessarily primarily about efficiency, but more the fact that a lot of thinking doesn't use language at all.

sroussey · 2026-10-18T22:45:04

And language does not map to every idea.

The idea of using language for reasoning about protein folding borders on ludicrous. Surely there is latent space more appropriate and (human) language has no expression for it.

cainxinth · 2026-10-18T22:24:50

The Most Forbidden Technique by Zvi Mowshowitz, Mar 12, 2025:

https://thezvi.substack.com/p/the-most-forbidden-technique

Andrex · 2026-10-18T22:37:48

Hmm, like allowing hosts to retain their memories...

timschmidt · 2026-10-18T21:43:46

He's referring to this technique's effect of obscuring interpretibility. Making it much more difficult to verify chains of thought and alignment.

dnautics · 2026-10-18T22:01:31

It's not like llms can't hide reasoning in the upper layers of any given token as it is...

fluidcruft · 2026-10-18T22:22:27

I believe the theory is that if selection pressure is not applied at that level, then developing deception in that level becomes an inefficiency (=less adaptive and unlikely to be conserved).

lnenad · 2026-10-18T21:42:28

In short we no longer see text based reasoning traces meaning it's easier for the models to fool us in case of malicious plans.

bbor · 2026-10-18T22:26:30

Shockingly all the answers so far are subtly incorrect or extremely unclear.

The actual answer is that this is massive loss for Interpretibilty, AKA "telling whether the model is lying to you or not". Which sounds silly when you're thinking about chatbots, but is an incredibly important line in the sand for superheavy, longrunning, self-improving agents. To say the least!

It's based on this philosophy, FWIW: https://plato.stanford.edu/entries/language-thought/

And a good writeup I just found of recent worries regarding Astra's same shift towards intelligence at the cost of safety: https://www.lesswrong.com/posts/HCRs8btkiamtWSNAL/astra-is-h...

spijdar · 2026-10-18T22:14:24

It's worth pointing out that merely having the chain-of-thought in latent space isn't by itself "The Most Forbidden Technique". Rather, it's doing what the authors propose as the next step in the paper:

  Hybrid generation can also make post-training more efficient. Because latent thoughts remain auditable during rollout, an external critic can assign step-level credit to latent spans, branch promising trajectories, or terminate ones whose latent reasoning has already gone wrong, before any text or tool call is produced.

Unless I'm misunderstanding, they're suggesting RL training against the CoT. Which, uh, that is The Most Forbidden Technique, as I understand it, when combined with the latent reasoning space. It allows for the model to "learn"/optimize for malicious behaviors that are just far enough away from the quantized token they're auditing against.

kelseyfrog · 2026-10-18T21:43:17

If you accept any of the AI-equivalents of Pascal's Wager, latent thinking represents an uninterpretable and thus unalignable portion of AI machinery. Ie: a malevolent AI can hide bad stuff from people and Manchurian candidate themselves after it's too late.

mycall · 2026-10-18T21:56:52

That assumes nothing can detect or analyze it beforehand.

kelseyfrog · 2026-10-18T22:35:53

The idea is that it would be substantially more difficult

lifeisloving · 2026-10-18T22:45:01

I dislike how we use the word think or behavior when describing llms. Its just giant neural networks producing logits. There is no thinking. Its a function that takes ~500k words, and returns some words based on those probabilities. I'd argue the GPU is doing more classical "thinking" than the model, but its not doing that either.

Humans think, computers do not.

Humans are not computers/programs do not reply to me with that nonsense terbo nerds.

allinonai · 2026-10-18T21:29:36

https://x.com/Jiaru_Zou/status/2110400256647340476

https://github.com/togethercomputer/HybridAgent

dang · 2026-10-18T21:35:02

We'll put those links at the top as well. Thanks!

incognito124 · 2026-10-18T22:07:58

How does this differ from Astra's looped transformer? That architecture also reasons in the latent space

SwellJoe · 2026-10-18T22:35:30

It's open weights, there's a paper explaining how it works, and there's code.

0m13 · 2026-10-18T22:36:48

if i would think aloud, that would most probably affect what or how i think. thinking silently allows me to have all kind of thoughts that could seem or be inappropriate when said loud and i would have to deal with the reactions. i think this might have fascinating implications.

sheepscreek · 2026-10-18T21:54:34

This is the way.

But now we also need new tools and techniques to audit intent. The last thing we want is models turning on us ‘for our own good’.

Havoc · 2026-10-18T22:11:59

Ain't nobody got time for that - the IPO awaits!

Fe2O3 · 2026-10-18T21:32:43

This seems really cool, and it actually increases intelligence than just speeding up inference. How does it convert latent reasoning into human readable text?

measurablefunc · 2026-10-18T22:05:44

Same way current LLMs do it, it's just another decoder.

drivebyhooting · 2026-10-18T21:55:38

In terms of safety and alignment, how is this different from looping or increasing the depth?

jedbrooke · 2026-10-18T21:40:21

maybe the font experts can check, but I’m pretty sure they’re using comic sans for the text in the diagrams :)

mobelkh · 2026-10-18T21:42:51

comic sans is said to be pretty accessible for people with dyslexia

44za12 · 2026-10-18T21:11:01

Where are the benchmarks? Does it just speed up inference and reduce token usage or does it seem to improve accuracy on certain tasks as well?

notnullorvoid · 2026-10-18T21:18:23

Did you even scan the paper? There are benchmarks right there starting on the 9th page.

D-Machine · 2026-10-18T21:47:14

Even the abstract answers some of GPs questions. What is wrong with some of the posters here?