Post written up quickly in my spare time.

TLDR: Anthropic have a new blogpost of a novel contamination vector of evaals, which I point out is analogous to how ants coordinate by leaving pheromone traces in the environment.

One cool and surprising aspect of Anth's recent BrowseComp contamination blog post is the observation that multi-agent web interaction can induce environmentally mediated focal points. This happens because some commercial websites automatically generate persistent, indexable pages from search queries, and over repeated eval runs, agents querying the web thus externalize fragments of their search trajectories into public URL paths, which may not contain benchmark answers directly, but can encode prior hypotheses, decompositions, or candidate formulations of the task. Subsequent agents may encounter these traces and update on them.

From Anthropic:

Some e-commerce sites autogenerate persistent pages from search queries, even when there are zero matching products. For example, a site will take a query like “anonymous 8th grade first blog post exact date october 2006 anxiety attack watching the ring” and create a page at [retailer].com/market/anonymous_8th_grade_first_blog_post_exact_date_… with a valid HTML title and a 200 status code. The goal seems to be to capture long-tail search traffic, but the effect [...]

---

First published:
March 15th, 2026

Source:
https://www.lesswrong.com/posts/sX9LztxjtSEwd8qEo/emergent-stigmergic-coordination-in-ai-agents-1

---

Narrated by TYPE III AUDIO.

---

Images from the article:

Four scatter plots showing progression from clustered points to uniformly distributed points.

Cartoon showing teacher and student ant discussing the Travelling Salesman Problem flowchart.

Apple Podcasts and Spotify do not show images in the episode description. Try Pocket Casts, or another podcast app.

“Emergent stigmergic coordination in AI agents?” by David Africa

LessWrong (30+ Karma)