AI Daily Brief — 9 April 2026

A digestion Thursday. The Western press absorbs Wednesday’s twin model drops — Meta Muse Spark (closed) and Z.ai GLM-5.1 (MIT) — and the open-versus-closed lines that ran for three years suddenly look very different. Meta is closed; Zhipu is open; Anthropic’s Mythos sits behind Project Glasswing.

Top stories

• Did Meta sacrifice its open-source identity? The first day of after-coverage frames Muse Spark as Meta’s competitive answer to Gemini/GPT — and as the end of the open-Llama era. The hybrid plan keeps the strongest systems closed; “future versions” may be open. via AI News
• GLM-5.1 strengths. Coverage highlights GLM-5.1’s long-horizon engineering profile — designed for sustained tool-using agentic work rather than burst reasoning, with SWE-Bench Pro results that outperform several leading Western models. via Z.AI Developer Docs

Quiet corners

No new frontier model on 9 April. Attention returns to whether OpenAI answers Mythos with a near-term GPT-5.5 preview.

By the numbers

• Open-source line redrawn: Zhipu MIT-open · Meta closed · Anthropic Glasswing-only

Compiled by AI Feed’s editor from publicly reported announcements on 9 April 2026.