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TLDR
Jev, a system one decision model, is 20-200x faster and 40-1000x cheaper than LLMs for making decisions, making it ideal for guardrails in AI coding workflows. Its most practical use case is replacing regex or LLM-based pre-tool use hooks to block risky agent actions like reading secrets or deleting files, with near-zero false positives and sub-second latency. The real value comes from sandwiching Jev between LLM calls: the LLM sets up the decision context and acts on Jev's output, while Jev handles the fast, cheap classification.
Key points
Jev is 20-200x faster and 40-1000x cheaper than LLMs for decision-making tasks.
Jev can replace regex or LLM-based pre-tool use hooks to block risky agent actions.
Jev can play video games in real-time for testing, catching bugs that LLMs cannot.
Jev can classify GitHub issues to route workflows and select appropriate model tiers.
Jev works best when sandwiched between LLM calls for setup and follow-up actions.
Tools mentioned
Techniques
- system one models
- pre-tool use hooks
- guardrails
- workflow classification
- gameplay testing
- browser automation
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Transcript (captions)
Jev is incredible. It was released recently and it popularized a type of AI model called system one models which specialize in making decisions instead of generating text. And so it's actually
way different from LLMs like Claude and GPT. And so it's opened up a whole new sprawl of use cases that everyone is sharing on the internet right now. And people are sharing a lot of really fun
and cool use cases with Jev. But something I'm hearing a lot, especially from people in my Dynamis community, is that the use cases are cool, but they're not always the most practical, right?
There's not a lot that you see and you're like, "Okay, I need to go incorporate this in my AI workflows right now." And so that's why I want to make this video just quickly showing
specifically for AI coding for incredible Jev use cases to make your AI coding workflows faster and more token efficient, which is a big deal right now, especially with how bad the rate
limits are. Now, if you follow the latest in AI, there is a very good chance that you've heard of Jev and probably even tried it out for yourself. Now, Jev is not the first kind of
decision model like this, but that's a whole another topic for another video. The point is Jev is really powerful. The way it works is you give it some kind of situation, which they call state, and
then you also supply with a list of multiple choice questions, and in parallel, it's going to answer each one of those questions with a probability, which is basically its confidence score.
Now, the thing is you can already do this with large language models, especially with structured output. You can have it make decisions that you can key off of for the rest of your
workflow. But what makes Jev so awesome is that it is 20 to 200 times faster than LLM at making decisions. And it's also 40 to a,000 times cheaper. Obviously, the big range here being you
can use different LLMs to compare against Jev. no matter the LLM that you use, Jev is going to be more accurate, faster, and cheaper for making any kinds of decisions. And so, at a high level,
when you think of like Jev as the decision maker, that's an endless number of possibilities that you can use it for. And so, that's why I want to get really specific with you here, just
quickly showing you, giving you inspiration for different ways that we can use it very practically. Now, for each one of these Jev use cases, they're valuable enough where I could make an
entire video going into how to build and incorporate it. But for right now, I just want to stay more high level. I want to keep this short and sweet, giving you inspiration here. So, you can
even pick a couple of these and maybe build them out yourself. And then also in my Dynamis community this Friday, I am running a workshop getting a lot deeper into these use cases. So, check
that out if you're interested. And yeah, like I said, a lot more content coming soon diving deeper into Jev cuz this is exciting for me. I actually said this in my first video on Jev. This is the first
AI model in a while that I'm genuinely excited for, and I think you'll see why as we get into these four use cases here. So, with that, let's just get right into it. My favorite use case for
Jev right now in my AI coding workflows is for security. Because the thing is, and you've probably seen this yourself, AI coding assistants are way too willing to do things that they shouldn't, like
read your environment variables, delete an entire folder, even if you have things in your global rules or skills to not do this, especially once you really start to bloat the context of a
conversation, or if you have a prompt that kind of gives it a workaround, it's going to figure out ways to do these things. And so that's why we need guard rails to prevent our agents from
performing destructive actions. and Jev can really be that guardrail. So the most popular and effective way to implement these guardrails for our coding agents is using hooks which was
introduced in claude code. But now pretty much every single coding agent has the idea of hooks where we can attach automations to run at different events that take place in the life cycle
of our coding agent. And so the most popular event is pre-tool use. So when the agent is about to perform an action like read a file or run a command, we can run an automation to basically
analyze that and either block the agent from performing that action or allow it to continue. And so you can see where we're going with this here because one of the most popular use cases is having
a pre-tool use hook that tries to analyze the agent's action to determine if it's going to read av file. Right? We don't want our secrets exposed into the context of our coding agent. And so it
has the opportunity to dish out an error code to essentially block that action. So the agent has to do something different like for example reading the&enb.example
instead. Now the problem with this hook until jevv is that we either have to have an LLM analyze every single call or we have to have some kind of deterministic process with regular
expressions. Either way, it's going to be expensive or not very accurate. Now, let's just scrap the idea of using an LLM right away. Because if we're going to analyze every single action the agent
wants to take, that's going to cost you hundreds or thousands of dollars throughout the month just to block these sensitive calls that might happen once in a while. And so, what I've done until
Jev is I use regular expressions. And so, I have a hook that runs that just does pattern matching to try to figure out the agent is trying to do something like reading my Google credentials,
reading my deleting a folder, whatever it is. But the problem is there are so many different ways that an agent is able to do these destructive actions because it can read the file directly.
It can write a Python script to do so or a bash command like right there are a million different things. And so we have this massive laundry list here and this doesn't even catch everything and there
are also a lot of false positives. And so what I've done is I've taken this pre-tool use hook and I've replaced it with my JevGuard. And I'll show you some stats in a little bit. This is so coste
effective and reliable. So with system one models again we give it state and a list of multiple choice questions. And so for anything that can go wrong with an agent action I'm asking if it is the
case right like are we exposing secrets it's going to say either true or false and we give some instructions for added context. This is part of the state and then is it destroying any data like
removing an entire folder any kind of exfiltration where we're maybe sending sensitive data out like through a prompt injection attack. And then another really cool one here is we can just
analyze is the agent going off task. And so we can use this pre-tool use hook for even more than just security. Just generally having another uh sort of model as a judge making sure that we're
staying on track for what we are trying to accomplish. And then as far as the state goes, the situation that's the main input to Jev. We're giving it the tool name, the effect of it, the input
like the arguments to the tool and also our current working directory. And so that gives it the holistic picture. And so when I ask Jev, I'm actually just using Jev right through open router with
their new decision endpoint. And then I'm giving it this state along with all the questions that I showed you above. So I've only been using this hook for a little bit since Jev just came out, but
my initial results are incredible. So my previous version of the hook using regular expressions, you can see that it didn't block that many of the risky calls. Now, obviously risky is
subjective. I've been pretty happy with this hook overall, but the main problem I've had with it is the false positives, blocking things that really shouldn't be blocked, like just writing the word.v
out to a markdown document. And then going to using an LLM, it does a really good job. I mean, not that many false positives. It blocks most risky calls. But even using something really fast and
cheap like Haiku, it still takes over a second. And yeah, it's only about a tenth of a penny per analysis, but that really adds up when your agent makes thousands of calls every single day. And
then we get to Jev. Jev blocks almost every single risky call, barely has any false positives. It is a quarter of a second for every single analysis, and it is a fraction of a fraction of a penny.
So, it's cost-effective, and it's fast. It gives us essentially the reasoning capability of an LLM for this kind of decision, but it feels like it's free. I mean, I know it's not quite free, but
yeah, it's not like it breaks the bank in any way. All right, so our next use case is game play testing. And this really applies to any type of application that requires a model to
make snap decisions or respond to things in real time. I'm just using video games as an example because it's really cool to watch Jev play the game. And it is something that I'm building myself for
real. And so with anything like a game, when you have 60 frames per second or 30 frames per second, a large language model is way too slow to respond to things. By the time it analyzes the
scene to make a decision, the scene is already passed, right? right? And the character is going to be dead in the game, for example. But Jev is able to keep up. It is incredible to watch. And
this is also very practical because we always want to have that validation step in our AI coding workflow. So for a video game, you know, after we build the next feature, we want the model to be
able to play the game as a user actually would. And that wasn't really realistic before until Jev. So take a look at this. I have a live example of Jev playing one of the games that I'm
building a proof of concept for right now. It looks like I'm playing. The character is attacking, dodging, moving around the map. You can see the decisions that Jev is making on the
lefth hand side right here with probabilities for all the different actions that we're giving as the options because again, it's all about the state, which is, you know, where everyone is in
the game and then the decisions like what move are we going to do next. And I have hands off the keyboard. It seriously looks like I am playing this right now. It is so cool. And so as it's
making the decisions and processing the state of the game, we can also analyze how things are going in general and act on that, right? Like maybe we do discover bugs for real as we're playing
the game. The kind of thing that an LLM could never really discover by itself just by, you know, running unit tests. And so I've been running this for real as I've been building new features in
the game. And it's genuinely caught bugs that the large language model is not able to by itself cuz the LLM can't really play the game. And yes, it can run like other tests and harnesses that
I build, but that's more deterministic and it's not really playing the game as a user actually would. And so the important thing is we still have to use a large language model to build the
harness for Jev, right? Like it has to figure out how do we translate the state of the game into the input to Jev. What are the options that we give it for different moves it can perform? So we
build that up front with the LLM, but then all of our testing going forward uses Jev. So, it's super fast, reliable, and cost-effective. One other thing that I have experimented with in the past for
video games is making it so that the large language model can actually slow down the game. So, it can play it frame by frame. That was kind of my way to have it actually play the game as a user
would before Jev. But, as you can imagine, that was incredibly slow and expensive. Now, I hope you can also see the pattern emerging as we're going through these use cases. We are never
really going to use Jev by itself. It is super powerful to use it in combination with LLMs because Jev is really good at making decisions, but it can't craft the decisions in the state upfront or really
act on them. And so the best way to use Jev is generally to sandwich it in between calls to a large language model. Like for example, with gameplay testing, we have an LLM build the harness and
then act on the bugs that Jev finds when it plays the game. Or with the security here, we have the coding agent performing different actions. Jev analyzes an action and if it blocks it,
then the agent, the LLM, has to figure out something else to do, right? Jev is never really the end of our workflow. It's always just making parts of our workflows faster and more efficient.
Now, another really good example of this takes us to our third use case with browser testing. Using a model to go through a web page and operate it as a user would in the validation step of our
AI coding workflow. It's very similar to gameplay testing. But the thing is, large language models have typically been decent at this because unlike with something like a video game, an agent
doesn't have to respond in real time to events with a website usually. And so, it's able to take its time and analyze the page to pick the next action. But, you guessed it, it is still slow and
expensive using an LLM compared to Jev. And Jev is even more reliable for this kind of browser automation. So, you probably use tools like the Playright MCP or Verscell's agent browser CLI to
do browser testing with an LLM. And now we have a lot of open- source tools coming out, the same kind of thing, but using Jev instead of an LLM. And it works incredibly well. There's a lot of
cool examples here showing at different websites that Jev is clicking around. The most important thing to keep in mind is you don't always have the opportunity to use Jev for literally everything
because Jev can't generate text like an LLM can. So if there's anything that requires free form text as an input to a site, typically you still need a large language model for part of the workflow.
But as much as you possibly can, you want to use Jev when you're just making decisions like what should I focus on or what button should I click. And so most of the workflow for your browser
automation should be driven by Jev now. So I'll link to this GitHub repo in the description. This is the best open source project I've seen for Jev browser use, but yeah, there are a lot of them
and you can also roll your own. I built my own browser automation with Jev as I've been testing it out. Like on this app right here, this is Dino Chat, which is in production right now. You can go
to chat.dynamus.ai and talk to this agent. It basically is able to search through all my YouTube content and then if you're logged in with the same email you use in the
Dynamis community, it'll also pull from my workshop and course content. So, it's a really cool app. And I've tested building different features and having Jev go through them exactly as a user
would. So, I won't bore you with a full test run right now, but I do want to show you just really quickly live Jev working on this site. And so, any text that you see at input is pre-generated
from an LLM, but everything else it is deciding live. The chat box to click into, the button to press to sign in, for example, and then also everything that it's doing here can be analyzed by
the LLM after to figure out if there's any bugs that it needs to iterate on. All right, the last of the four use cases here for Jev is workflow classification. And this is becoming
more and more important for me over time. I want my workflows to be dynamic. For example, I don't always want to use the same large language model. It depends on the difficulty of the task.
And so for the sake of token efficiency, I might want something at the start of the workflow that classifies what tier of model I need to use. Another good example is sometimes based on the type
of work that comes in, I need to be using different skills or different steps. And so a really clear example of this is when you have a GitHub issue that you want to work on. It might be a
bug that you have to investigate and fix or a feature that you have to plan and build. And so I don't want to have to make that decision for myself. That's not going to scale with my AI coding
workflows. I need something to classify that and direct the workflow at the beginning. And that is what Jeb is for. And this exact workflow I'm describing to you here with the different
classification steps, I have built that as an archon workflow. So, I've covered Archon a lot on my channel before. It's my open- source harness builder that allows you to build these larger AI
coding workflows very easily for a lot of the different things that I've been covering in this video. And of course, I've been incorporating Jev with my Archon workflows. And so, what you're
looking at right here is the graph visualization where we take in a GitHub issue and we use Jev to classify two things. What is the tier of model that we need to knock this out? Because maybe
it's something super simple. We can't just use something like sonnet 5. and then also deciding the route. Is this again like I said earlier a bug we have to investigate and fix or is it a
feature we have to plan and build out. And so this is the YAML file that makes up the entire archon workflow. And for each step where I want to call upon Jev, I just have this Python script where I
give the arguments and it forms the decision, asks Jev, and then the rest of the workflow is going to act on the output of Jev. And I'll even quickly show you the Python script because we
can see all the questions we're sending into Jev at the very top. It is so powerful how you can ask a ton of questions that Jeb will answer in parallel for super cheap. So like what
kind of work does this GitHub issue ask for? Is it, you know, a bug or a feature that that determines the skills that we use for the rest of the workflow? What's the tier of model that we need? Right?
like based on the difficulty of the task. A fast model like I don't know GBT6 Terra, something standard like Sonnet 5 or GBT6 Soul, maybe a strong model like Opus 5.5 or GBT6 Astra. You
get the idea, right? Like Jev is making that determination. And in my testing, it does a very good job just generally understanding the difficulties of tasks and the type of tasks. And so back over
to this specific run for the classification here, it figured that it is a bug that needs to be investigated. And then for the tier selection here, I'll go to the logs really quickly. I
know it's kind of hard to pick out, but when the next step ran, it did investigate standard, as in it was using that middle tier of the model here. So, whatever I have selected for that,
something like a sonnet 5. And of course, I was the judge myself for all the jev testing that I did here. So I ran this archon workflow 12 times and every single time I completely agreed
with the decisions with the classifications that it made up front. There's also a separate archon workflow more for pull request reviewing. And so using classification up front to figure
out what kind of review do we need like is this a bigger thing that needs a full architecture review or just a light chore that has to be validated quickly. And it wasn't perfect but still 15 out
of 16 is pretty darn good. And if we look at the cost here, a fraction of a penny versus what it would typically cost an LLM. And again, 32 cents per poll request, that is really going to
add up, especially with a project like Archon where we are dealing with dozens, hundreds of poll requests and issues every week. So there you have it. Those are my four favorite use cases for using
Jev in AI coding workflows. And of course, let me know in the comments if you want me to make a dedicated video for any of these cuz I could certainly go a lot deeper and help you incorporate
these into your workflows as well. And so if you appreciated this video, you're looking forward to more things on Jev and AI coding, I would really appreciate a like and a subscribe. And with that, I
will see you in the next video.