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AI Daily Brief — 9 July 2025

An unusually loud Wednesday. Grok 4 and Grok 4 Heavy launched on an evening livestream with chart-topping benchmarks and a new $300/month SuperGrok Heavy tier. The launch was bracketed by Linda Yaccarino’s resignation as X CEO and the latest in Meta’s talent war — Apple’s foundation-models head Ruoming Pang departed for $200M+. Perplexity opened Comet to Max subscribers.

Top stories

  • xAI launches Grok 4 and Grok 4 Heavy. Livestream at 8pm PT. xAI calls it “the world’s most powerful AI model”. Grok 4 (general) plus Grok 4 Heavy (multi-agent reasoning variant) with 256K-token context and parallel test-time compute. via xAI
  • $300/month SuperGrok Heavy tier debuts. xAI’s most expensive plan and the only one that unlocks Grok 4 Heavy’s multi-agent reasoning, parallel agent execution and extended thinking mode. Matches OpenAI’s Pro tier territory. via TechCrunch
  • Grok 4 Heavy posts record benchmarks. xAI reported Grok 4 Heavy is the first model to break 50% on Humanity’s Last Exam (44.4% with tools standard, ~50% with the Heavy multi-agent variant), and roughly doubled the prior SOTA on ARC-AGI-2 with 15.9-16.2%, well ahead of Claude Opus 4 and OpenAI o3.
  • Linda Yaccarino resigns as X CEO. Announced on X itself hours before the Grok 4 livestream. Follows the previous day’s antisemitic Grok meltdown and months after Musk folded X into xAI. No successor named. via CNN
  • Meta poaches Apple’s Ruoming Pang for $200M+. Pang, who led the team behind Apple Intelligence’s on-device foundation models, departed for Meta Superintelligence Labs on a multi-year package reported over $200M, dominated by Meta stock. Apple did not match. Foundation Model team being reorganized under Zhifeng Chen. via 9to5Mac
  • Perplexity Comet AI browser opens to Max subscribers. Chromium-based agentic browser for Windows and macOS, first to Perplexity Max and Plus subscribers plus invited waitlist users. Full extension support; bakes Perplexity’s AI assistant into the browser surface for tab management, summarization and on-page agentic actions. via Perplexity

Who shipped

xAI shipped Grok 4 and Grok 4 Heavy. Perplexity shipped Comet browser. Apple shipped Ruoming Pang (to Meta).

Open-source pulse

Japanese lab Sakana AI released TreeQuest under Apache 2.0 — an Adaptive Branching Monte Carlo Tree Search system that lets teams of LLMs (o4-mini, Gemini 2.5 Pro, DeepSeek-R1) cooperate on a single task. On ARC-AGI-2 the multi-model team beat the best individual model by ~30%. via VentureBeat

Money, infra & hardware

OpenAI’s $6.5B all-stock acquisition of Jony Ive’s hardware startup io — first announced May 21 — formally closed July 9. Brings Ive’s team in-house to build a new generation of dedicated AI devices intended to move users “beyond phones and laptops”.

Quiet corners

Tesla confirmed Grok integration ships to Model S/3/X/Y and Cybertruck with AMD infotainment hardware running software 2025.26+, rollout starting July 12. Fallout from the July 8 Grok antisemitism episode continued landing at Capitol Hill.

By the numbers

  • 256K — Grok 4 context window
  • 44.4% / ~50% — Grok 4 / Grok 4 Heavy on Humanity’s Last Exam
  • 15.9-16.2% — Grok 4 Heavy on ARC-AGI-2 (nearly 2x prior SOTA)
  • $300/month — SuperGrok Heavy tier
  • $200M+ — Ruoming Pang’s Meta package
  • $6.5B — OpenAI’s io acquisition close value

Compiled by AI Feed’s editor from verified web sources for 9 July 2025.