Weekly Briefing: GPT-5.6, Claude Sonnet 5, Cowork mobile, Meta Muse Spark, and xAI's Grok 4.5
OpenAI's GPT-5.6 (Sol/Terra/Luna) + ChatGPT Work, Claude Sonnet 5 as a cheaper way to run agents, Cowork on mobile with a "reflect" dashboard, Meta Muse Spark 1.1, Gemini Spark on macOS, the MCP security reckoning, the async "work agent," xAI's Cursor-trained Grok 4.5 priced to undercut Opus — plus a Claude Code subagents tip.