TLDR

TLDR AI 2025-09-15

Grok 4 Fast ๐Ÿค–, post-training 101 ๐Ÿ“ˆ, xAI layoffs ๐Ÿ’ผ

Baseten Raises $150M Series D at $2.15B Valuation (Sponsor)

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Headlines & Launches

xAI launches Grok 4 Fast in early access beta with up to 10x speed (1 minute read)

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Deep Dives & Analysis

Post-Training 101 for LLMs (39 minute read)

The Vertical AI Playbook (Book)

Breaking GPT-OSS: A brief investigation (6 minute read)

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Engineering & Research

The Illusion of Diminishing Returns: Measuring Long Horizon Execution in LLMs (1 minute read)

The second wave of MCP: Building for LLMs, not developers (3 minute read)

VaultGemma: The world's most capable differentially private LLM (11 minute read)

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Miscellaneous

AI Will Not Make You Rich (35 minute read)

You should be rewriting your prompts (6 minute read)

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Quick Links

Understanding GPU Architecture (35 minute read)

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