Interconnects, the Substack of former AI2 post-training lead Nathan Lambert, is the inside-the-labs newsletter for the models and reasoning layer under agentic development, minus the hype. Facts below verified as of 2026-09-13.
He explains the research and the open-model ecosystem from someone who built it, which makes him the direct bridge between the frontier labs and the engineer choosing a model or an agent today.
What it is #
A Substack newsletter, website, and interview podcast by Nathan Lambert, a machine learning researcher who was a post-training lead at the Allen Institute for AI (Ai2) and co-led the OLMo open-model effort.
The newsletter describes itself as the cutting edge of AI from inside the frontier labs, minus the hype.
His Get Good at Agents (2026-01-21) piece and his
Claude Code reviews document how he actually operates coding agents in his own RL research.
Status #
Active and prolific as of 2026-09-13.
The newsletter reports over 82,000 subscribers as of 2026-09-13, and he published four posts in the week before verification (September 8 to 11, including an open-model reading list and a piece on open artifacts #24).
He released the RLHF Book (‘26) with a companion post-training course, and his site links to open-model tools he maintains: the Artifacts Hub, an Adoption Dashboard, and the ATOM Project.
He announced he is “currently doing something new” after leaving Ai2.
Strengths #
- He writes about post-training, reasoning, and open models from direct authorship rather than press coverage, so the technical claims are reliable.
- He uses the coding agents under discussion in his own research work, documenting real multi-agent and RL workflows rather than demos.
- The focus on open models and candid comparisons gives readers a usable lens for model selection without relying on benchmark marketing.
- The RLHF Book and course are a rare, grounded curriculum for the post-training layer that most practitioners never get.
Cautions #
- The newsletter is opinion-driven and fast-moving, so takes can shift and need re-checking against primary sources.
- Some posts are analysis and commentary rather than new findings, and readers must separate signal from churn.
- The writing is research-oriented and assumes familiarity with fine-tuning and RL concepts.
- He is an open-model advocate, so the open-versus-proprietary framing is a side he argues from, even when balanced.
Pricing #
Free to read, reader-supported via paid subscriptions. The RLHF Book is paid; parts of the course and companion materials are free.
Compared to #
- Lilian Weng: both explain the model and reasoning layer, but Weng surveys the broader research canon while Lambert tracks the current open-model and post-training state.
- Chip Huyen: the model-training microview versus the application-systems macroview; Lambert is upstream of where Huyen’s survey starts.
- Andrej Karpathy: both are researcher-writers who set vocabulary, but Lambert is high-cadence and tool-engaged while Karpathy is low-frequency and conceptual.
Bottom line #
Recommended for the engineer who wants to understand the reasoning-and-post-training layer behind the agents they use, and to pick open models with good information. Not for anyone who wants a mostly-vendor-neutral or application-level overview; this is the model-side view, argued from an open-model vantage.
Changes #
- 2026-08-29 - Created as the model-and-post-training band of the people and publications category expansion.
See also #
- Model Selection for Coding Tasks - the decision his model-and-reasoning coverage feeds
- Agentic Coding Tools Landscape - the harnesses he uses and evaluates in his own research
- Lilian Weng - the complementary research-survey voice
- Scaling the LLM Agent Company - the supervision and model questions his multi-agent RL work raises
References #
https://natolambert.com/ - his site with background, the RLHF Book, and the open-model tools
https://www.interconnects.ai/ - the newsletter, with subscriber and positioning claims
https://www.interconnects.ai/p/get-good-at-agents - his documented agent workflow and scoping argument
https://rlhfbook.com/ - the RLHF and post-training book and course
https://aiweekly.co/alerts/nathan-lamberts-rlhf-course-reaches-tool-use-and-agents - a third-party note that grounds his course contents and its stated limits