Claude Mythos 5 leaks in Dev Mode and API with tier-above-Opus pricing hints

• According to testingcatalog's Dev Mode sighting, a Claude-Mythos-5 slug appeared in Dev Mode, and AiBattle_'s API sighting said the same name briefly showed up in the API.
• Several leak accounts, including kimmonismus's tier claim, framed Mythos as a separate class above Opus, but Anthropic had not publicly confirmed a new tier by June 6.
• Pricing chatter split fast: kimmonismus's earlier pricing post circulated a $16 input and $80 output figure, while AiBattle_'s pricing speculation floated $25 and $125, and AiBattle_'s follow-up noted that both numbers were still unconfirmed.
• The stronger paper trail before the Mythos 5 slug was claude-oceanus-v1-p, which testingcatalog's Oceanus post and WesRoth's red-team post tied to red-team access and to the Mythos line.

You can read Anthropic's official Project Glasswing page, its Glasswing expansion post, and TestingCatalog's Oceanus report. The odd part is that the leak trail moved from claude-oceanus-v1-p in red-team channels to Claude-Mythos-5 in Dev Mode and the API, while the public Anthropic material still only talked about Mythos Preview and Glasswing.

The cleanest new fact on June 6 was the model name itself. Dev Mode sighting

According to testingcatalog's Dev Mode sighting, Anthropic exposed Claude-Mythos-5 in Dev Mode. AiBattle_'s API sighting said the same slug briefly appeared in the API, which is a stronger signal than pure rumor because it points to product surfaces rather than secondhand screenshots.

The surrounding interpretation was more speculative. chetaslua's spotted-slug post guessed Mythos would become its own family alongside Haiku, Sonnet, and Opus, and kimmonismus's tier-above-Opus claim called it a tier above Opus. Those are leak-account claims, not something Anthropic had said publicly by that point.

The price talk looked more like rumor triangulation than a leak with a source document.

Two numbers circulated at once:

• $16 input, $80 output per million tokens, per kimmonismus's pricing post
• $25 input, $125 output per million tokens, per AiBattle_'s pricing speculation
• 4x to 5x Opus pricing, according to bridgemindai's pricing reply

The only solid update in-thread was caution. In AiBattle_'s follow-up, the same account that floated the higher number said pricing was still unclear and could end up lower.

Before Mythos 5 showed up, the leak ecosystem was already following claude-oceanus-v1-p.

TestingCatalog's Oceanus report said claude-oceanus-v1-p appeared in the Claude Console on June 3 and that red teamers got access around the same time. testingcatalog's Oceanus red-team post and WesRoth's red-team post both treated Oceanus as a Mythos-related preview candidate.

The output-sharing wave added to that connection. testingcatalog's Oceanus preview post described Oceanus as a rumored upcoming Mythos version, while chetaslua's Mythos preview demo and chetaslua's 10-minute preview demo posted generated artifacts and labeled them Mythos preview output. None of that proved product naming, but it did establish a sequence: Oceanus checkpoint first, Mythos 5 slug second.

Anthropic's public material by June 6 confirmed Mythos Preview and a widening access program, not Mythos 5.

Anthropic's Project Glasswing page describes Claude Mythos Preview as the model powering a restricted cybersecurity initiative with launch partners including AWS, Apple, Cisco, Google, Microsoft, NVIDIA, and Palo Alto Networks. Its Glasswing expansion post says roughly 50 initial partners got access in April and that Anthropic was extending the program to about 150 additional organizations after those partners found more than 10,000 high or critical flaws.

That official trail matters because it narrows what was real on June 6:

• Mythos Preview existed publicly, via Glasswing.
• Access was restricted to vetted partners.
• Anthropic was expanding the program.
• Anthropic had not yet published a Claude-Mythos-5 announcement, pricing page, or model card.

So the leak story was not whether Mythos existed. Anthropic had already confirmed that. The new part was the apparent transition from a preview program and the Oceanus checkpoint name into a shippable Claude-Mythos-5 slug on product surfaces.