Our first public proof: no-start-env v0.1 measures physical reasoning under real constraints. Read the results ↗

The physical world doesn't grade on a curve.

AI is leaving the chat window and entering machines. Second Nature builds training environments and evals where models must reason through physical state, causality, tools, and consequences — before they act in the real world.

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The physical world is missing
from the training set.

Manuals capture how machines should work. The knowledge of how they actually fail lives in the hands of people who build, operate, and repair them. We turn that tacit expertise into interactive, physics-grounded tasks with outcomes models cannot talk their way around.

110 1011
no-start-env — medium_corroded_ground · seed 41
# complaint: engine cranks slowly, won't start
agent → measure_voltage(battery_positive, battery_negative, resting)
12.58 V # battery looks healthy
agent → measure_voltage(battery_positive, battery_negative, cranking)
10.41 V # holds under load — not the battery
agent → measure_voltage(battery_negative, engine_block, cranking)
2.75 V # massive drop across the ground path
agent → replace_part(ground_strap) · attempt_start()
engine starts ✓ — root cause: corroded ground strap · score 100 / 100

One environment. A general method.

no-start-env is our first public proof: an agent gathers evidence, builds a causal picture, takes action, and is graded by what the simulated system actually does. That pattern extends from fault isolation to robot recovery, maintenance, and operation.

111 0001 1110 000
Mean score ⓘ pass^k ⓘ v0.1 ▾ Uncoached ⓘ
# ↑MODELEPISODESSCORE / 100
1fable-525 86.0root cause 19/25
2gpt-5.525 82.3root cause 20/25
3grok-425 74.9root cause 16/25
4sonnet-525 74.5root cause 19/25
5gemini-3.5-flash25 59.7root cause 14/25
6haiku-4.525 39.9root cause 10/25
7ministral-3b25 23.0root cause 6/25

A physical-reasoning gap you can measure.

Our first benchmark uses 5 vehicle electrical scenarios × 5 epochs with outcome-based grading. Showing 7 of 9 models; full table in the repo.

The platform

Training gyms and test rigs for physical intelligence.

01 / PHYSICS

Physics, not scripted answers

Agents interact with a live system model, not a tree of hand-authored responses. State, measurements, and consequences are computed from the governing physics, so each task can vary without breaking the rules of the machine.

02 / GRADING

Outcomes, not plausible text

Graders reward correct causal understanding, disciplined action, and efficient recovery against an expert baseline. The environment state decides whether an intervention worked; confident explanations and brute-force guessing do not.

03 / VERIFICATION

Expert verification is the moat

Models can generate simulations they cannot warrant. Every scenario is played and signed off by someone who understands the real system. In no-start-env, that review caught four plausible physics bugs that had passed the automated suite.

Applications

From model capability to machine reliability.

Built for frontier labs training general agents, robotics teams testing deployment readiness, and operators turning hard-won machine knowledge into repeatable practice. We measure whether a model can observe, localize, decide, and recover under physical constraints.

INTERACTIVEPHYSICS-GROUNDEDRL-READYEXPERT-VERIFIED
100 0100
WHAT PHYSICAL EVALS REVEAL · v0.1
Tool use without understanding.
Plans that break the physics.
Coaching dependence.
13.6-pt uncoached gap4 physics bugs human-caught
Open proof

Inspect our first environment.

no-start-env is open source and pip-installable. See how a physical system model, instrumented action space, outcome-based grader, and expert-verified invariants fit together — then run the benchmark on any Inspect-supported model.

$ git clone https://github.com/Jaiparmar940/rlenv
$ pip install -e ".[dev]"
$ python scripts/sanity_check.py # physics invariants
$ python scripts/run_evals.py --scenarios all
# → scored table: root cause · parts · efficiency

Build the missing
training ground.

We work with AI labs, robotics teams, and industrial operators to turn real machine behavior and hard-won domain knowledge into interactive training environments and rigorous evals. If your models must reason before they act, we'd like to talk.

Jaivir Parmar
Who's behind this

Built by Jaivir Parmar, whose work spans robotics, embedded systems, fabrication, and ECU-level diagnosis. no-start-env begins in a domain he can personally verify; every environment follows the same standard of hands-on domain sign-off before it ships.