Fordel StudiosAnthropic Accidentally Leaks Claude Code Source — Opus 4.7, Sonnet 4.8, and Mythos Next-Gen Exposed
What Happened
A missing config line left source maps in Claude Code's npm package, exposing ~500K lines. The leak revealed Opus 4.7, Sonnet 4.8, next-gen family Mythos, a new Capybara tier above Opus, Undercover Mode, and 44 feature flags including background agents and voice mode.
Our Take
Anthropic left source maps in Claude Code's npm package on March 31, exposing ~500K lines of internal TypeScript. The dump confirmed Opus 4.7, Sonnet 4.8, a next-gen family called Mythos, a Capybara tier above Opus, and 44 feature flags including background agent system Karios and an Undercover Mode that strips Anthropic branding for employees on external projects.
Any agent workflow hardcoding "claude-opus" as the ceiling tier is already undershooting. Capybara will break cost models before it has a public release date. Developers who treat model names as stable constants — not volatile identifiers — are building fragile routing layers on top of an API that Anthropic reshuffles without warning.
Teams using LiteLLM or similar routing abstractions should add a Capybara slot now. If you're calling the Claude API directly with a hardcoded model string and not doing capability-tier routing, this leak is a free heads-up you'd normally miss.
What To Do
Do route model selection through an abstraction layer like LiteLLM instead of hardcoding model strings because Anthropic's tier structure is expanding with Capybara and Mythos before any public announcement.
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