Amazon has blocked Meta's Muse AI assistant from making purchases on its marketplace, escalating a dispute over whether third-party AI agents can act inside e-commerce platforms. Users trying to shop through Muse now see a warning that continued access by an unauthorized AI agent violates Amazon's conditions of use. Amazon said it asked Meta to exclude its marketplace voluntarily but received no response; the companies are now communicating directly, while Amazon declined to say whether it is considering legal action. The dispute is significant despite extensive commercial ties, including Amazon shopping within Facebook and Instagram since 2023 and Meta's multibillion-dollar April agreement to run agentic AI workloads on Amazon's cloud. Amazon says Muse gave no advance notice, does not identify itself while browsing, and can reach account pages and order history. Meta says Muse cannot see passwords or payment methods, while credentials supplied by users are held in secure storage. The disagreement focuses on browser-based access for services without public APIs. Amazon has pursued similar restrictions against Perplexity, Google and OpenAI, while developing its own agentic shopping tools. Muse launched on September 8 and quickly reached the top of Apple's U.S. App Store free-app chart. Its expansion depends on platforms permitting access, leaving unresolved questions about authorization, customer ownership, security and the division of transaction value.