Meta Platforms has delayed the developer API for its closed-source Muse Spark AI model yet again and, as of June 2, has set no firm launch date, The Wall Street Journal reported. A company spokesman told Reuters on June 3 that the interface was in partner testing and would ship in June, but the slip already stretches nearly two months past Muse Spark's April debut, when chief AI officer Alexandr Wang told developers it would arrive "soon."
A Closed Model With No Public Access
Muse Spark is the first Meta model released without downloadable weights — meaning an API is the only route for outside developers to build with it. Beyond a handful of evaluation firms that Meta granted pre-launch access, the broader developer community has effectively been locked out for two months. The model already powers Meta's consumer AI assistant inside Facebook, Instagram, WhatsApp, Messenger and Threads.
Two Slips Since April
The first delay, from April to May, was blamed on bugs found in testing and the need to expand serving infrastructure. The timeline then moved to June. Meta and the WSJ's sources have not cited a performance or safety issue, despite internal evaluations Meta says rank Muse Spark competitive with OpenAI and Anthropic models and ahead of xAI's Grok on most tests — claims outside developers cannot yet verify.
The $145B Capex Question
The stall lands as Meta has raised its 2026 capital expenditure forecast to as much as $145 billion, up from a January range of $115B to $135B — a step-up that knocked the stock more than 5% in April after-hours trading. CEO Mark Zuckerberg has hinted a Meta cloud business is "definitely on the table" to monetize spare GPU capacity. Without a working API, that revenue path stays theoretical.
Behemoth, Then Muse Spark
Muse Spark comes out of Superintelligence Labs and its TBD Lab unit, formed after Meta's $14.3B investment in Scale AI brought Wang in as chief AI officer. It follows Behemoth, the model Meta delayed in 2025 and ultimately shelved. This week the company pressed an adjacent monetization lever, debuting a business agent for WhatsApp, Instagram and Messenger at its Conversations event in London with more than a million businesses already in test markets including India, Mexico and Brazil. For context on rival AI launches see Microsoft's MAI-Code-1, Anthropic's Project Glasswing expansion and DeepSeek's $7.4B round.
Reporting based on coverage from The Wall Street Journal, Reuters and Implicator.ai.