Anthropic two new model codenames leaked: Claude Marshmallow and Melon
Developers discovered on Aug 24 two undisclosed Anthropic codenames claude-marshmallow-eap and claude-melon-eap in internal testing.
On August 24, developers discovered two previously undisclosed model codenames in the Anthropic API and Discord community: claude-marshmallow-eap and claude-melon-eap. The eap suffix indicates both models are still in internal testing and only accessible to a limited number of developers.
Early testers reported that Marshmallow overall outperforms Melon, with conversational naturalness even exceeding the currently released Opus 5, though neither matches flagship Fable 5. The community speculates the two new models likely belong to Opus or Sonnet iteration lines, possibly new-generation Haiku candidates.
This is not the first time an Anthropic EAP codename has leaked early. In early July, Claude Honeycomb EAP briefly appeared in the Cursor code editor before being removed. Anthropic officially released Opus 5 on July 24, which the industry widely associates with Honeycomb.