Josef Chen

· 14 min read

Agentic Robotics Flips the Build Order

GPT-6 Astra drives robots now, which is awkward timing for Physical Intelligence's $20 billion round.

Johannes Vermeer, The Lacemaker, c. 1669 to 1671. Oil on canvas. Musée du Louvre, Paris.
Johannes Vermeer, The Lacemaker, c. 1669 to 1671. Oil on canvas. Musée du Louvre, Paris.

In October, University of Illinois researchers gave a coding agent a UR5e robotic arm with force sensing at its wrist and the deceptively challenging job of opening a see-through drawer (deceptively because a camera looks straight through it). FORCA, their agent, running on Claude Fable 5, wrote the Python that controlled the robot and managed to open the drawer four out of ten times using only the camera feed. Once it was allowed to read the force sensor, it was able to iteratively improve its program using the force feedback (a bit like a coding agent using a test suite to identify and squash bugs) until the program opened the drawer in all ten trials. Then Claude left, and the program kept opening the drawer with no model in the loop.

Same agent, with and without touch. A coding agent's final program on a real UR5e arm, with no foundation-model calls, ten trials per task. Drawer: 4 of 10 with one camera only, 10 of 10 with a wrist force sensor. Door handle: 1 of 10 with one camera only, 10 of 10 with force. The program finds the handle by eye, then refines the grasp by touch.

VLAs (vision-language-action models) are single neural networks that map camera images and language instructions to motor commands, and they have been the focus of most robot foundation model efforts at big labs over the last three years. In other words, the labs built the hands first and put a planner on top to give them orders. Figure's Helix splits the job in two. Helix System 2, analogous to what Daniel Kahneman calls slow thinking, works out what to do and runs at 7 to 9 Hz, while Helix System 1, analogous to fast thinking, translates those instructions into motor commands for Figure's arms at 200 Hz. The instructions between them are embeddings, basically a list of numbers that only have meaning to the models trained on them.

Illinois turned it around: start with the System 2 model, have it practise on a real robot's arm, and let it write the code that performs the motions. Ken Goldberg at Berkeley, who says he had "always been cautious and skeptical of near-term adoption of robots", calls this order Agentic Robotics.

My thesis: agentic robotics puts System 2 first and has it write System 1. The learned policy keeps the behaviours an agent can't check with the sensors it has, and agents call it as a tool when they reach one.

How the robot gets built, roughly. Until 2025: a planner passes embeddings or words to one learned policy, the VLA, which sees, reads and acts, as in Helix, GR00T N1 and Hi Robot. 2026, two routes. A rented frontier model practises through tools and writes a program that runs without it, as in RAX and FORCA; in RAX, an exception hands control back. Or the model stays in the loop and calls a learned policy as a tool, as in Harness VLA and EBench, or keeps acting through code, as in PyRUA-Lean.

Astra writes better than it drives#

Eighteen days after OpenAI released GPT-6 Astra (on 3 September, with a focus on computer use and coding), the RoboDojo team gave it access to only one action (move gripper to target) and a recipe describing each of 42 simulated manipulation tasks. Without any robot-specific fine-tuning1OpenAI hasn't said whether Astra was trained on any robot data. The RoboDojo paper says there was "no robot-specific or task-specific fine-tuning performed for this evaluation", but whether some of RoboDojo's material made it into Astra's training data is, the authors write, "unquantified rather than ruled out". it achieved a success rate of 22.48%, outperforming the best of 40 trained policies on the 10 September leaderboard (19.34%). (For comparison, GPT-5.5 could only achieve 0.88% using the same action.) This is not a level playing field. The trained policies aren't shown the recipes, Astra does poorly on precision (4%, while the best trained policy in aggregate manages 16.75%), and the simulator waits while it thinks: in RoboDojo, Astra is moving for 8 to 76 seconds while thinking for an average of 55 minutes.

Same robot, same tool, new model. RoboDojo average success across 42 simulated tasks: GPT-5.5 through a gripper tool 0.88%, GPT-6 Astra through the same tool 22.48%, the best of 40 trained policies on 10 September 19.34%, VPP2, a learned model, on 9 October 32.26%. Only the model changed between the first two, and the simulator paused while Astra thought.

Just one day after appearing on the board, two world-action models from LiberAI overtook Astra, and as of 9 October Astra, directly controlling the gripper, ranked tenth. However, when the PyRUA-Lean team used the same model to generate Python code (with a higher reasoning effort) over some basic geometric functions and a segmentation model, without recipes or learned policies, its average task success rate increased to 51.6%, 2.3 times higher than when controlling the gripper directly and 19.4 percentage points higher than the leaderboard leader at the time.

As the PyRUA-Lean authors stress, these are comparisons of systems, not just models. Changing the planner from GPT-5.5 to Astra changes system performance from 0.88% to 22.48%. (No retraining, since planner and controller communicate via language.) If they communicated via embeddings, changing to a better planner would usually require retraining the controller. Changing the harness changes system performance from 22.48% to 51.6%. In contrast, compiled programs are immutable except for intentional recompilation, which is likely what you want at a factory. Phillip Isola at MIT wrote in September that if LLMs can competently control robots, "Every robot with an internet connection becomes a potential tool for Fable, Astra, and other AIs."

On 26 September, Stanford's HomeBody team showed Astra commanding a Unitree G1 humanoid as it explored a kitchen it had never seen.

On 12 October, Unitree's founder, Wang Xingxing, said his biggest mistake in the last ten years was "not believing in AI enough" (in Zilan Qian's translation).

Altimeter's Freda Duan called Astra robotics' GPT-3 moment, and said some in robotics seem "reluctant to acknowledge it". I'm happy to admit it. The most important robot brain this year came from a chatbot company, and lots of robot foundation-model companies are, whether they like it or not, building hands for rented brains. Jim Fan has gone further:

(Self-reported. Like every head-to-head number in this section, it comes from simulation.)

Back in July I wrote about a reflex that monitors the policy driving a robot, sees when it's about to screw up, and passes control to a bigger model if things start to look dicey, because "A chatbot gets a free ten seconds to think; a robot arm drops what it's holding." I thought of it as System 1 calling in System 2 for backup. I had the order wrong. In October the frontier model ran first and wrote the System 1 code itself, and the reflex survived as an exception that hands control back. I got the clock right, at least: a Unitree G1 controlled directly by a frontier model took a median of 24.84 seconds per request. On the G1, Astra spends about 90% of each run deliberating. A mind that slow can't be System 1.

The chef writes the recipe and leaves#

Robot cells have long been built by a specialist who writes the recipe, programs the robot (often using a teach pendant), commissions the cell, adjusts it to its environment and then walks away. The robot does its job, often in a production line, for the next 12 to 15 years. In 2014, a spot-welding cell cost $133,000, of which the robot's hardware and software accounted for only a quarter, according to BCG estimates; some $46,000 went on installation, programming and integration. An agent can't do the installing; the programming is the part it might automate. Language models have been used to generate robot programs since at least 2022 (see the Code as Policies paper). What's new is that these agents practise on real robots. Where VLA labs are trying to replace the robot's program, these agents are trying to replace the programmer. It is already in production: Goldberg writes that his Ambi Robotics co-founder, Jeff Mahler, applied an agentic robotics harness to a real industrial problem and deployed the result to robots sorting packages across the US.

RAX, released in October, lets a coding agent (either Codex or Claude Code) control a robot through tool calls, with its cameras, its controls and a fixed budget of practice episodes. Given an air fryer, the agent figured out how to open it, load it and close it again, which took 72.3 minutes of model time. It then wrote a Python program of about 1,500 lines, with no learned perception and no learned policy, that does the same thing. The thinking time was greatly decreased (from 72 minutes to 18 seconds), although the arm's movement time was about the same (from 2.9 to 2.5 minutes). This whole session (from exploration to the ninth run of the program) took place in the course of a morning (09:18 to 12:05).

The air fryer: 72 minutes of thinking, then 18 seconds of code. RAX on a real Franka arm. The agent's first success: 72.3 minutes of model time plus 2.9 minutes of robot calls, 262,400 output tokens. The program it then wrote, about 1,500 lines of Python: 18 seconds of code plus 2.5 minutes of robot calls, with 2,000 output tokens from the agent monitoring it. Nine runs of one program, runs 2 to 10: run 2 a safety stop when the elbow hit a camera; run 3 not described; runs 4, 5 and 8 needed a resume; runs 6, 7, 9 and 10 clean and unattended, as the agent scored them.

Our first robot was held together with zip ties and delusion. Three engineers iterated it up to version 547, which as of last year was still dishing out thousands of meals a month. RAX's agent debugged its own program in a morning.

If you've built coding agents, this will look familiar. The agent writes programs that use the same tools it has access to when acting, so any program it develops interactively can be run as-is in autonomous mode. If a program wants to do something that breaks a limit, the tool call fails and the agent gets a message telling it which limit it broke, so that it can try a different approach. If a program gets stuck, it can throw an exception to hand control back to the agent. Every robot has a skills repository, each agent session works on its own branch, and changes are merged only with evidence that they worked unattended. The agent scored 4 of the 9 program runs as clean and unattended (although a human still reset the environment in between).

Tidying a lab corner on a real Rainbow RB-Y1, from a side camera: park the chair, stack the cups, put the cups and a banana in a basket, put the basket on a cabinet, tuck the chair, put a box on the cabinet. The cups-and-banana step had no stored skill, so the agent wrote code on the spot; the other five ran on four skills it wrote in five earlier sessions. An operator stayed in the loop and corrected it in chat; the run took 98 minutes. Photo: Huang et al., RAX, arXiv 2610.22496, CC BY 4.0, cropped.

At MicroFactory, Astra and Claude Opus are still in the loop, but "computer vision code written by the model" does the fast work.

On its first run, the agent's program ended in a safety stop: the robot's elbow bumped into one of the cameras and knocked another out of calibration. The agent can add safety constraints on top of those already in place, but it cannot loosen them. RAX already performs self-collision, joint-limit and workspace-bound checks, and won't move unless armed by a human operator. These checks model the robot, not its environment, which is why its elbow could still collide with a camera in its way. After that collision, when a banana was placed in front of the same camera, the agent wouldn't pick it, because its forearm would come within about 1 cm of the camera; it asked for the banana to be moved instead. In Illinois, the researchers hard-coded a 30 N force limit. RoboDojo's authors stopped their own real-robot evaluation after the model "repeatedly issued physically unreasonable or unsafe actions, and some incidents damaged equipment; no person was injured", and concluded that such incidents "motivate independent safety checks and stopping mechanisms rather than reliance on the model's judgment alone." Goldberg himself warns that "exploration can damage hardware or the environment." And LLMs can't always be counted on to say no:

The hands still matter#

In the first route, the chef writes the recipe and leaves. In the other, the chef stays and runs the kitchen, as in Auguste Escoffier's brigade system, introduced in 1890 when he took over the kitchens of the newly opened Savoy Hotel in London: divide the kitchen into stations, each run by a cook who specialises in that station's work, so that the chef de cuisine can, in Britannica's words, "oversee the entire operation".

Harness VLA, likewise, delegates the planning and memory burden to a coding agent (Claude Code or Codex in their experiments) and sees a frozen VLA's performance increase from 50.0% to 82.4% on LIBERO-Pro, a simulation benchmark. It has scripts for the easy parts of the task and invokes the VLA (via a single function) for the contact-rich parts. Which planner does better isn't fixed: Claude Code beat Codex on LIBERO-Pro, 82.4% to 72.1%, and Codex beat Claude Code on RoboCasa365, 55.4% to 48.6%.

Harness VLA, one simulated rollout on LIBERO-Pro, three frames: move_to, a move the planner picks, over the basket; release, after which the milk carton lands outside it; and vla_act, a call in which the frozen VLA re-grasps it. The same frozen VLA scored 50.0% run directly and 82.4% with Claude Code planning and its memory. The paper calls these planner-selected contact attempts, not continuous control. Frames: Harness VLA, arXiv 2607.08448, CC BY 4.0.

How hard to press on a potato is something I've done since I was six in my parents' restaurant and still can't articulate. I assumed that was exactly what you'd hand to a learned policy. The Illinois robot was given a cucumber to peel, held by a person. Its program logged the force on the wrist 100 times a second and attempted to keep it within the range of 4.5 to 7.5 N. When the agent realised there were gaps in the peel, it referred to the force data and added a new rule: stop the blade until it makes contact again. Contact was lost only 2.2% of the time, against 40.6% for the vision-only agent. I guess I could have written it down. Letting go of an object and grasping it again is harder without touch. In PhysLadder, Astra acting directly on arms with no force sensors (the thing that rescued the drawer) went from 80% on placing and aligning, on a real robot, to 0% once it had to break and re-make contact. Its authors say the roles of "model decisions, sensing, and robot execution remain to be isolated".

Rodney Brooks has never been polite about the hands. "Watch any humanoid video. It's really terrible manipulation," he said on a podcast in October. Cloth is the strongest case against this essay, and Physical Intelligence's laundry-folding demos make it. Dyna's robot, it says, can complete a full shift at a commercial laundry, using its learned model DYNA 2 and a higher-level vision-language model to direct it. On cloth, trained policies still have the edge over agents.

The problem of knowing when you've failed is a hard one, and one I return to often in my research. Some domains make it easier than others: coding agents can run tests to see if they pass, and embodied agents can use whatever sensors they have (the gripper's width in Physical Agency, force traces in Illinois). In one case a RAX robot's base hit a cabinet during a turn the agent had planned by hand, after which the agent checked the base's swept footprint before every base move.

Trial 1: the base swings into the cabinet. Four frames of a real Rainbow RB-Y1's base swinging into a cabinet during a turn the agent planned by hand. Afterwards the agent wrote itself a rule: check every base move against its swept footprint before it runs. The rule is the agent's own code, a check, not a verified safety function. Photo: Huang et al., RAX, arXiv 2610.22496, CC BY 4.0, cropped.

Follow the meter#

But practice does not come for free. Across its simulated and real experiments, RAX used over $100,000 worth of API credits. The agent's first success on the air fryer took 262,400 output tokens; after that, each run of the resulting program used about 2,000, which the agent needed to watch the execution. In Illinois, token usage drops to zero once the program is deployed, since it never calls a language model. The pattern of API costs mirrors that of the expert it's replacing: expensive while programming the cell, and relatively cheap thereafter. Over a robot's 12 to 15 years in service, the meter that keeps running belongs to the hands.

While the model stays in the loop, the hybrid is cheaper than direct control and better than either half on its own. In EBench, given direct control, Astra achieved a success rate of 46.7%, at a token cost of $16.82 per success. When able to delegate control to Physical Intelligence's π0.5 policy (fine-tuned for EBench; the cost of π0.5 inference not included), Astra's success rate rose to 53.0% at $4.99 per success, beating π0.5 by itself (41.4%). It didn't beat the best trained policy in the benchmark, a world-action model that reached 55.3% on its own; paired with a different world-action model, Astra reached 56.0%. Robot foundation models are already for rent. Dream Labs prices its flagship model at $3 an hour, and Jeremy Collins of Dream Labs put it on X: "A model like Dream-1 will soon be a tool call for LLMs, and that gets more feasible as LLMs inevitably get faster and cheaper."

Skild AI was reportedly valued at over $14 billion in January and claimed $100 million of recurring revenue in September. Physical Intelligence has no revenue, yet its reported $20 billion valuation, up from more than $11 billion in March, and an October API launch titled "Frontier Models for Every Robot" are priced as if it will one day own the robot's brain. Even inside the company, Stone Tao, a researcher there, wrote in September of "the feeling that Astra could just zero shot all the robotics foundation model companies", before offering the hybrid answer: "leverage astra together with a good robotics model". But here's the thing about Helix: its halves communicate in embeddings, and that means the hands and the brain are trained together. Once they communicate in tool calls, the maker of the robot can rent one half and buy the other, and, at least this autumn, the best brain came from a chatbot company. (Physical Intelligence can still be the best hands your AI brain can rent. That's a good business.) Valuing it at $20 billion means betting that most of the work robots do looks like laundry.

Brooks, on the same podcast: "a lot of wasted capital is going into collecting data sets, which I don't think are gonna be useful in the long run." Nobody raising a teleoperation round wants to hear it. I suspect most useful robot work looks more like a drawer than like laundry: a job where a sensor can tell the program it failed.

A drawer, again#

SayCan had a drawer too, in 2022. Its planner got all 21 drawer requests right, but the robot only succeeded a third of the time. Its low-level skills were the limiting factor, trained on 68,000 teleoperated demonstrations and 12,000 successful episodes filtered from 276,000 it collected on its own. This October in Illinois, the planner practised on one drawer eight times, then wrote a skill for it that uses the force sensor in the wrist. Then it left.

Braindump by Josef Chen


  1. OpenAI hasn't said whether Astra was trained on any robot data. The RoboDojo paper says there was "no robot-specific or task-specific fine-tuning performed for this evaluation", but whether some of RoboDojo's material made it into Astra's training data is, the authors write, "unquantified rather than ruled out".

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