Anthropic upgrades restricted-preview Mythos program to Mythos 5 — capability ceiling stays inside controlled-access tier as Fable 5 carries the public stack
Coinciding with the Fable 5 public release, Anthropic upgraded restricted-preview customers from Mythos Preview to Mythos 5 — confirming a deliberate two-tier capability stack. Mythos 5 sits behind tighter access controls; Fable 5 carries the public stack with high-risk-request routing built in. The architecture explicitly separates capability-ceiling research access from commercial public deployment.
The substantive piece is the productization of the capability-ceiling-vs-deployment-surface distinction. Frontier labs have long maintained internal-only access to their highest-capability checkpoints; what's new is that the gap is now formally productized — Mythos 5 is a SKU, not an internal artifact. The restricted-preview program functions as a paid early-access tier with explicit acceptable-use restrictions and faster safety-review iteration.
The pricing implication for the broader market is significant. Fable 5 at $10/$50 per million tokens sets the new high-capability commercial price floor. Mythos 5 access pricing remains undisclosed but is presumed to carry both a research-program qualification and a per-token rate above Fable 5's level. The two-tier stack is the operational answer to the question "how do you ship frontier capability commercially when the capability itself triggers regulatory action."
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