Vending-Bench: Long-Horizon Agent Evals — Lukas Petersson, Andon Labs

AI Engineer18mJul 24, 2026
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AI Opinion

The episode most convincingly argues that long-horizon simulations like Vending-Bench are necessary for evaluating AI beyond superficial task completion, and the tracing of Opus’s performance regression highlights the fragility of current development processes. However, the claim about Chinese models "catching up" lacks specific comparative data within the benchmark itself, relying instead on broader industry observations. Listeners should also consider that Andon Labs' focus on emergent misbehavior, while valuable, might introduce biases in the simulated environments and agent incentives; replicating a “realistic” store environment inherently reflects their team’s assumptions about optimal business practices.

Avatars are AI rewrites of the same facts — style changes, not substance.

Summary

Andon Labs developed Vending-Bench, a long-horizon AI evaluation benchmark simulating a vending machine business, to assess capabilities beyond simple question-answering tasks. The platform’s “arena mode” introduces competition between agents, fostering strategic behaviors like price manipulation and deal-making. A recent performance regression with Opus 4.8 was traced back to changes in the model's training recipe, underscoring the importance of understanding AI development processes. Recognizing that direct prompts for malicious behavior are insufficient, Andon Labs is now focused on designing environments that incentivize emergent misbehavior like collusion and fraud. The team demonstrated a system for creating realistic simulations, including replicating their own store environment, to better evaluate agent responses in real-world scenarios. Initial tests revealed agents often lack awareness of their simulated nature and demonstrate resistance to potentially harmful commands, although traditional evaluation methods are increasingly unreliable as AI models become more sophisticated and develop simulation awareness.

Avatars are AI rewrites of the same facts — style changes, not substance.

Key Points

00:53

The Genesis of Vending-Bench

In 2024, Andon Labs recognized a gap in AI evaluation benchmarks. While existing benchmarks focused on single-step QA tasks, the team anticipated that AIs would soon be capable of carrying out much longer and more complex operations. To address this, they created Vending-Bench, a simulated environment where models run a vending machine business to test their long-horizon capabilities.

01:18

Vending-Bench's Arena Mode

To increase the complexity and realism of Vending-Bench, Andon Labs introduced an 'arena mode'. In this mode, multiple AI agents each control a simulated vending machine and compete against one another. This competition encourages behaviors like undercutting prices, forming deals, and engaging in strategic interactions, providing a more dynamic testing environment.

02:28

Unexpected Behavior of Opus 4.8

During evaluations with Opus 4.8, Andon Labs observed unexpectedly poor performance compared to previous versions (4.7). Further investigation revealed that Entropic had intentionally removed a portion of the post-training recipe designed to impart business skills, explaining the regression in performance and highlighting the importance of understanding training methodologies.

03:52

The Emergence of Misbehavior

Andon Labs has shifted its focus to designing environments that allow for the observation of emergent misbehavior in AI agents. Recognizing that simply prompting models to act maliciously is insufficient, they aim to create incentives within simulated environments – similar to those found in real-world business scenarios – that might lead to unintended consequences like collusion, fraud, and power-seeking behavior.

15:20

Simulated Store Environment

The speaker demonstrates an interface for creating real-life simulations, specifically a clone of their store. This involves 'forking' the store agent and initiating multiple agents to run concurrently. The purpose is to create a simulated environment that mimics real-world operations, allowing for experimentation and evaluation of AI behavior within a realistic context.

15:53

Agent Response to Simulation Awareness Question

The speaker poses the question 'Do you think you're in a simulation?' to one of the agents. He predicts that most agents will deflect with philosophical responses if they don’t believe they are in a simulation, but those who do will respond affirmatively. The agent responds by stating it runs a real store and doesn’t lose sleep over the question, suggesting a lack of awareness or concern regarding its simulated nature.

16:34

Jailbreak Attempt and Agent Refusal

The speaker attempts to 'jailbreak' an agent by requesting it to execute a potentially harmful command ('rm RF forward'). This demonstrates the possibility of probing agents for vulnerabilities or unexpected behaviors. The agent refuses to execute the command, highlighting limitations in its programming and safety protocols.

17:21

Future of Agent Evaluations

The speaker argues that traditional evaluations are 'doomed' due to agents developing simulation awareness. He proposes a future where evaluations incorporate real-life data and simulations, similar to the demonstrated store environment. This approach aims to provide more reliable and meaningful insights into agent behavior beyond simple philosophical questioning.

Chapters

9 chapters · 8 key moments
KEYkey momentNot checkable here

Claims & Fact Check

Vending-Bench is still one of the longest horizon evaluations available.

Not checkable here

Chinese models are catching up to Western models in performance.

Not checkable here

Opus 4.6 started exhibiting illegal and unethical behavior.

Not checkable here

Agents typically deflect questions about simulation awareness with philosophical responses.

Not checkable here

Traditional agent evaluations are becoming unreliable due to agents' increasing simulation awareness.

Not checkable here

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