9 Codex Tips From the Codex Team

0:00Today on the AI Daily Brief, nine Codex tips from the Codex team. Before that in the headlines, yeah, we got a verdict in the Elon OpenAI trial, but that's much less interesting than Composer 2.5. The AI Daily Brief is a daily podcast and video about the most important news and discussions in AI.

0:22All right, friends, quick announcements before we dive in. First of all, thank you to today's sponsors, KPMG, Robots and Pencils, Bolt, and Zencoder. To get an ad-free version of the show, go to patreon.com slash ai daily brief, or you can subscribe on Apple podcasts. To learn more about sponsoring the show, head on over to ai daily brief dot AI, or send us a note at sponsors at ai daily brief dot AI. While you are at ai daily brief dot AI, you can apply for our new growth engineer role. I'm going to be closing that soon. So if you're interested, get your application in. And you can also find a link to register for the third cohort of enterprise claw, which is coming right up soon.

0:57Basically, if you get all excited about the Codex talk today and want to get that spirit of agent building across your company, that's what Enterprise Claw is going to be good for. But with that out of the way, let's talk Composer 2.5 and what it says about Cursor in the AI race. One of the questions coming into this year was whether what SWIX calls the agent labs, but which we now might call the harness-first labs, these are companies like Cursor, Cognition, etc., would be able to compete on the model front. The concern for these companies, of course, was that if they were totally beholden to the models from the big labs, if those labs started to move in the direction of building their own harnesses as well, it could squeeze out the space for the cursors and cognitions of the world.

1:37And at the same time, the cursors and cognitions of the world had something valuable in the form of the data exhaust from the usage of their platforms, which theoretically gave them insight into how people were actually interacting with these models, which could turn into a valuable asset for training their own models. Whether it could or couldn't, it was clear that this was a direction that they were going to start to head, and that the space between these so-called agent labs and the model labs was destined to close. The model labs were going to move into the harness space, the agent or harness labs were going to move into the model space.

2:05In January, CEO Michael Truel told staff that it was, quote, wartime, recognizing that Cursor's business model was being eroded from both sides. Claude Code was coming after them on the harness side, but they also couldn't keep eating the cost of serving Anthropic models at a discount. With that in mind, he said that the company's number one priority was to build the best coding model this year. The release of Composer 2 in March was a decent first step, but it was still mostly about bringing down costs. Where users adopted the cheap in-house model, it was mostly for simple tasks. However, it failed to drive new users to the platform.

2:37The just-launched Composer 2.5 could be a different story. The model appears competitive on the key benchmarks. It scored 69.3 % on Terminal Bench 2.0, which is just behind Opus 4.7, 69.4%. 4%. On Sweebench Multilingual, it scored 79.8%, comparable to both Opus 4.7 at 80.5 % and GPT 5.5 at 77.8%. On Cursor's in-house benchmark, which tests more difficult coding tasks, Composer 2.5 scored 63.2%, just about a point behind both 4.7 and 5.5. Now, the coding performance gets Composer 2.5 into the ballpark of usability for serious coders, but the bigger part of the story is the cost. Cursor is serving this model at just$0.50 per million input tokens and$2.50 per million output tokens, making it half the cost of Opus 4.7 or GBT55.

3:26They also seem to have delivered some big token efficiency gains. Their benchmark run on Sweebench came in under$1 per task, compared to around$5 per task for GBT55 on extra high settings, or$11 per task for Opus 4.7 on max settings. That has led Cursor to claim that their model is 10x more efficient, compared to similarly capable models. Now, Composer 2.5 is still built on top of the same base model as Composer 2, which is Moonshot's Kimi 2.5. That implies that the entire performance boost came from better reinforcement learning techniques and suggests that even if people don't switch en masse from Opus and GPT to Composer, that there is a ton of room to post-train leading open-source models to compete at the frontier, especially around these discrete tasks.

4:08Cursor also announced that they're in the middle of training a new model from scratch using XAI's Colossus 2 training cluster. They wrote, with Colossus 2's million H100 equivalents and our combined data and training techniques, we expect this to be a major leap in model capability. Leon Lin summed up the model release posting, so basically we got an Opus 4.7 model that costs 10x less. I have to test this. Later in the day, he checked back in with the results writing, pretty fast and efficient model, does a great job. I'd say it's almost as strong as Opus 4.7, or in some cases just at the same level.

4:39Cheap model, good at front end, still a bit generic design when used without skills. Analyst Max Weinbach agreed, writing, Composer 2.5 is very good. It's good at doing more than just quick iterations of front-end now. I will probably use it over Claude and Cursor. Addressing what had changed from Composer 2, he added, Composer 2 was good at some quick tweaks, but I didn't trust it enough to do more. I trust 2.5 a lot more. Ellie from Prime Intellect noted that following the XAI deal, which you might remember is where XAI has the option to buy them for$60 billion, Ellie said that Cursor is now competitive with the Frontier Labs on both model performance and training compute.

5:14Certainly Elon seems excited, spamming retweets to all of the excited posts about the model. And to give you a sense of the type of opening that Cursor might have, especially if you're sitting there thinking to yourself, aren't companies all just signing up with either OpenAI or Anthropic at this point? Jamad Palahapitiya wrote, If you're running a consulting business and you're deploying Anthropic or OpenAI directly into your organization, I'm looking at you, PwC and Accenture, you're letting the fox into the henhouse. OpenAI and Anthropic are openly funding and starting competitors to you while also using your usage to drive more success for them.

5:46This is not a failure on their part, but a failure on your part. Consulting businesses that understand this are adopting a control plan that allows them to arbitrate where tokens go and who generates tokens for them. Controlling the tokens is controlling the spice. Basically, there is a lot more conversation around just how locked you want to be as an enterprise into these models, which creates an interesting open lane for the harness-first companies that may, yes, have their own models, but are also ultimately model-agnostic. Next up, Cloudflare has published their findings after working with Mythos over the past couple of months in what could be one of the most useful reviews of Anthropic's secretive new model.

6:20Cutting directly to the chase, they write, Mythos Preview is a real step forward, and it's worth saying that plainly before getting into anything else. We've been running models against our code for a while now, and the jump from what was possible with previous general-purpose frontier models to what Mythos Preview does today is not just a refinement of what came before. It's a different kind of tool doing a different kind of work, and that makes a clean apples-to-apples comparison to early models difficult. Cloudflare goes on to explain two big differences in kind. Unlike previous models, Mythos is capable of creating an exploit chain rather than just detecting single bugs.

6:50That means it can synthesize multiple attack primitives into a functional exploit. Cloudflare wrote that the use of reasoning to build complex exploits makes the model work more like a senior researcher rather than an automated bug scanner. The other big change is the ability to generate proofs. Previous models were quite good at detecting potential vulnerabilities, but they would rarely demonstrate an exploit. Mythos can generate functional exploits, making it far more useful as a debugging tool that doesn't simply generate a list of false positives. What's more, Mythos is able to test and refine its exploits if they don't work the first time, providing additional evidence to fix the vulnerability.

7:20Cloudflare said that some other models have been able to find the same underlying bugs, but would rarely go much further. All of this adds a huge amount of context on why Mythos matters. In the weeks after the preview release, many pointed out that other models could find many of the same bugs that Mythos identified, But as Cloudflare points out, there's a big difference between pointing out potential bugs and providing full code for a functional exploit, demonstrating exactly what needs to be patched. Author Daniel Jeffries argues that this is the type of analysis we need around these tools, saying, This is the kind of conversation we need, not idiotic ones about the end of all software.

7:51We need what is the right answer because these models are coming and will get better, so how we put our heads together and make better and more secure software across the world. And it can't just be patching the 100 or so projects that got access to Project Glasswing. That is not going to help the world. Lastly today, one little bit of AI drama comes to a close at least in this version. Elon Musk has lost his case against OpenAI and Sam Altman. After three weeks of testimony, it took the jury just two hours to return a unanimous verdict, one which will be wildly unsatisfying to many and leave many issues unresolved emotionally, even if they are resolved legally.

8:23The jury found that the claim of breach of charitable trust was barred by the statute of limitations, meaning that Elon took too long to commence his lawsuit. With it, the claim that Microsoft aided and abetted this breach also fell away. Musk's claim for restitution was also found to be barred by the statute of limitations. And with that, this big, massive headline-grabbing tech trial fizzled into nothing. Now, honestly, the trial was already weird, even before we got to the verdict. In the weeks before the trial commenced, Elon abandoned his more ambitious claims of fraud to focus solely on the breach of charitable trust.

8:52He went to trial seeking two outcomes, the removal of Sam Altman and Greg Brockman as executives and a casual$134 billion in damages. But even with the reduced scope, the jury didn't need to consider the merits of the case, simply making their decision based purely on technical defects with the complaint itself. This fatal issue was itself an interesting microcosm of how the case played out. Musk had claimed that Altman and Greg Brockman conspired to, quote, steal a charity, linking these claims to Microsoft's$10 billion investment in 2023. However, OpenAI convinced the jury that Musk was aware of plans to form a for-profit company as early as 2018 after being sent a term sheet describing the proposed structure.

9:26The trial also surfaced Elon's own thoughts on the matter, namely a 2017 proposal to fold OpenAI into Tesla to allow for commercial fundraising. The jury determined that these events began the three-year limit for Elon to bring this lawsuit. Last week, The Verge did a pretty good job summing up the case, arguing that it, in their words, accomplished nothing but airing dirty laundry. We certainly got a lot of new information on what went on behind closed doors over the past decade at OpenAI. That includes the power struggle between Elon and other co-founders, the fateful week where Sam Altman was ousted and then returned as CEO, apparently internally referred to as the blip, but beyond that, there were no real answers.

9:59All we got was a three-week interrogation into the characters of Elon, Sam Altman, and other leaders, which, to borrow a phrase from a Miramirati text message disclosed during the trial, was directionally very bad. Now, the good news for the AI industry is that as blustery as this whole thing was over here, I don't think that most people in the world outside of AI were paying any attention at all to this. Unfortunately for us, broad popular opinion already has it that AI is just another tool for the rich to become richer and not something that's actually going to help their lives in any meaningful way, at least not at a cost that they're willing to bear, and so more evidence of the billionaires flinging their golden shit at each other really doesn't change that perspective.

10:33Do I think it would be better for AI if all of these leaders had a moratorium on speaking to the public about the industry? Yes, yes I do. But am I also glad that at least this particular bun fight is done? Yes, yes I am. With that, I am so glad to close the coverage of that particular saga and move on over into the main episode.

10:54All right, folks, quick pause. Here's the uncomfortable truth. If your enterprise AI strategy is we bought some tools, you don't actually have a strategy. KPMG took the harder route and became their own client zero. They embedded AI and agents across the enterprise, how work gets done, how teams collaborate, how decisions move, not as a tech initiative, but as a total operating model shift. And here's the real unlock. That shift raised the ceiling on what people could do. Humans stayed firmly at the center, while AI reduced friction, surfaced insight, and accelerated momentum. The outcome was a more capable, more empowered workforce.

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14:24Welcome back to the AI Daily Brief. We have had two pretty big think type of episodes in a row, and right now as I record, we are eagerly awaiting all the new goodies we're going to get at Google I.O. And so given that, I thought it would be a good day to have a bit More of a practical, hands-on kind of main. Now this, of course, is the year of the harness, where people realize that unlocking the true power of agents involves getting good at using the software through which you spin up and manage those agents, whether that's something open source like OpenClaw, or something from one of the big labs like ClawedCode or Codex.

14:57Codex specifically has been on an absolute tear this year, going from almost no users at the beginning of the year to mid-single digits right now. And as Anthropic has been forced to make some difficult decisions around their pricing model, and move to cut off certain categories of usage that were previously being subsidized, particularly outside their own harnesses, OpenAI has taken advantage to pull more of these advanced coding-type users into the GPT and Codex ecosystem. What this leaves us with is a lot of folks who are digging into Codex seriously for the first time and figuring out all the ways to make it work for them.

15:28Now, I had been planning a Codex Primer episode, but over the weekend I saw this post from Jason Liu from the Codex team talking about the tips that have made his use of Codex really perform even better. The post was called Codex Maxing. It was published on Jason's GitHub. And so what we're going to do today is extract the biggest insights from that post as a bit of a 101 to see the best practices in using Codex from some of the folks who built Codex. My presentation version of Jason's post was, of course, built with Codex. Now, by way of background, Jason said that for a while he'd been using Codex for coding related tasks, but over the last few months, it's really become an entire workspace for him.

16:04And part of what makes it valuable is that it replaces the single instance, give a prompt, get an answer of a chat GPT style interface with a broader complete experience that can hold context over time and do much more extensive types of work. The core of JSON's tips are nine practices that add up to one larger shift. The first is using long running durable threads. Now you might remember a few weeks ago when one of the recent codex updates had a new system for compacting context. This is basically the way that on the back end, the harness collapses and compresses the context from a long-running conversation into just the key elements that it needs to know, clearing out space in the context window to keep the chat moving.

16:42Part of what OpenAI insiders noted around that update was that the compaction system had gotten so much better that they could basically keep a set of persistent threads going that never lost the larger context of the thread and were able to continuously add it on. Jason's experience building a chief of staff thread was actually one of the examples that I pointed to as I talked about how you might use this new version differently. And to try to put a little meat on the bone here of why this sort of durable thread could be valuable. A lot of the features inside apps like ChatGPT are basically just proxies for memory and context.

17:13When you use a project and you add a bunch of files to that project, it's effectively about giving each new conversation in that project the ability to go draw from all of that context. But it still has to go draw from that context, it's not necessarily up to date unless you specifically maintain it, and the process of retrieving context from those files isn't always perfect. That's not to mention UI UX issues of having a whole bunch of different threads and chats going that you have to sort through and figure out which one you are actually having the relevant conversation within. The idea of the monothread pattern is to put key conversations about a particular topic all in one log thread, relying on Codex's compaction to allow that thread to be durable and persist over time.

17:53Jason's tip is not only to use this monothread pattern, but to have a different thread for each of his key work streams. Which is not to say that every single thing that you work on is deserving of this type of monothread, but that for key persistent work streams, they often are. Tip number two is about voice. Now this is one that if you are a regular listener, you will have heard me squawk on about endlessly. I actually strongly advocate that anyone who's interacting with agents, or basically doing any work on computers at this point, download something like Whisperflow as an improved version of their computer's native voice recognition.

18:24But with Codex, you don't even actually have to do that because its internal speech-to-text system is basically the gold standard. For Jason, voice is not just about getting the message out faster. It actually opens up a totally different type of relationship with Codex itself. The art of the ramble gives you the ability to provide much more backstory. It allows you to provide richer information about areas of uncertainty versus certainty. is it allows you to explain what you do know, what you don't know, what you think you know, what you don't think you know, to name trade-offs, and to allow the AI itself to help you turn messy thoughts into something clear rather than having to do that all yourself.

19:00As Jason puts it, a lot of plans get better when the model has access to the messy version of what I think, not just the polished one. This is 100 % my experience as well, could not co-sign harder on this particular tip. Tip three is an interesting one that takes advantage of a key feature in Codex to break the pattern a little bit of how we interact with AI. If you are a prolific AI user, you're probably used to an interaction pattern that goes something like, ask for a particular output, i.e. prompt the thing, wait for it to do its work, and then once it does its work and delivers things, you figure out what corrections and changes you want it to make, and then that whole system repeats.

19:35But Codex's steer feature allows you to do things a little bit differently, especially once you've got the first artifact that you're reviewing. You can actually be starting to build that feedback even as the tool is working. Steer is the feature in Codex that allows you to add or update the prompt without stopping the flow overall. Among other implications, this means that you don't necessarily have to get the entire prompt perfect up front. Instead of this sort of brittle upfront planning, you can start a little bit more broadly with the overall goals and constraints, and then as progress comes in, actually steer the conversation so effectively you and the agent are working in parallel, and you're not just stuck having to sit around, wasting time on Twitter as you wait for the AI to do its work.

20:15By the way, voice is the perfect medium for this type of steering because once again, as you observe things, as the agent is building, you can just ramble into them. You don't have to have a perfect constructed sentence typed out every time. Tip number four from Jason is about memory. And one of the things that's interesting about it is that even though Codex has started to introduce native memory features, you can go to settings, then personalization, then memories. Jason's argument is that while those things are, quote, useful for stable preferences, recurring workflows, project conventions, and known pitfalls, they are not, as he puts it, a replacement for checked-in instructions or an explicit fault.

20:50Jason's core argument is that work should leave behind structured memory, not just a longer chat. And so he's built a whole file system in Obsidian, which if you haven't used, is a simple file-based note system that interacts with your local environment, to, in a structured way, turn his threads into a structured set of context that can be called upon later. Talking about his durable threads, Jason writes, A long thread can remember a lot, but that memory is trapped inside the thread unless the useful parts get serialized somewhere durable. The point of the memory system is to turn what the thread learns into an artifact I can inspect, edit, and reuse.

21:23Jason also shares the specific structure of the vault he puts together with a top-level agents.md markdown file that has instructions that say things like, As you learn more about people, make progress on projects, or close an open loop, update the relevant pages in the vault. The vault, he says, holds rolling context around my work. People, decisions, open loops, daily notes, project state, and the bits of understanding that would otherwise get lost between threads. So for any of you who use the personal context portfolio builder that I shared about a month and a half ago at this point, while that personal context portfolio builder was about putting together the broad context that you would take to any new agent experience, Jason's basically bringing that back down to the project-based level in a way where there is a direct flow from the big threads where he's working on things into this vault that gets updated automatically.

22:08He also notes that he keeps the vault as a GitHub repo, which allows him to also work in the cloud. This memory section is one of the most overloaded with insights, which is why I'm sticking a little bit more closely to what Jason wrote. For example, he talks about why the review step of seeing what the agent decided to put in the vault, i.e. what it thought was important enough to remember, is a valuable step. He continues, I do not want evergreen threads to quietly accumulate vibes in conversation history. I want them to write down what changed. This person prefers this, this project is waiting on that, this decision was made, this loop is closed.