Anthropic's Marshmallow and Melon Model Codenames Surface Ahead of Possible Release

On August 24, multiple developers and users discovered two new model IDs in Anthropic's systems and API: claude-marshmallow-eap and claude-melon-eap. The "eap" suffix indicates an Early Access Program, typically signaling an imminent release. Speculation points to an updated Opus or possibly a new Haiku, but no performance claims have been officially confirmed.

Confirmed

• The two model IDs are genuinely visible in Anthropic's API and systems, independently reported by kimmonismus, eyishazyer, and others
• The eap suffix denotes the Early Access Program
• The naming scheme has shifted from animal names to fruit/food codenames

Unconfirmed

• According to a leak relayed by davidad, Marshmallow outperforms Melon and beats Opus 5 at conversation, though neither reaches rumored Fable-related benchmarks; heypearlai cautions that all claims rest on a single screenshot, and past codenames like "Fruitcake" and "Honey…" proved unreliable
• Commenters on eyishazyer's post suggest Anthropic typically tests two checkpoints in parallel and releases only one; both models repeatedly hitting max token limits on identical questions is consistent with A/B testing, but this remains community inference
• SimplyAnnisa attributed the models to DeepSeek and flagged excessive "thinking Tokens" consumption, contradicting other sources that identify Anthropic; given the identical token-limit behavior described, the attribution is doubtful and the Anthropic account should be preferred

Why it matters

• New codename leaks often precede releases; an Opus update would be a major iteration of Anthropic's flagship model
• The dual-checkpoint race mechanism, if real, offers a glimpse into Anthropic's internal evaluation process: parallel testing, winner-takes-release

2026-08-24 ~ 2026-08-24 · 6 related posts

• [source] New Claude Models 'Marshmallow' and 'Melon' Spotted, Likely Opus Update — kimmonismus · 2026-08-24
• [source] Anthropic 'Marshmallow' and 'Melon' Models Leaked in API — 机器之心 · 2026-08-24
• Anthropic Opus rumors based on single screenshot: analyst urges caution — heypearlai · 2026-08-24
• [source] Anthropic's dual codenames melon and marshmallow: picking one, not launching two — eyishazyer · 2026-08-24
• Leak: Anthropic Testing New Models 'Marshmallow' and 'Melon', Marshmallow Beats Opus 5 in Chat — davidad · 2026-08-24
• DeepSeek's New Models Burn Through 'Thinking Tokens' During Testing — SimplyAnnisa · 2026-08-24