New Claude Sonnet 4.8 LEAKS!

The video, presented by a digital avatar of YouTuber Julian Goldie, centers on an alleged accidental leak of Anthropic's internal code that supposedly revealed details about an upcoming model called Claude Sonnet 4.8. According to the video, on March 31st, 2026, Anthropic pushed an update to their Claude Code tool via NPM and accidentally included an internal debugging file called a source map, containing approximately 512,000 lines of internal code. This file reportedly spread across the internet before Anthropic could retract it, and buried within it were references to unreleased model names — including Claude Sonnet 4.8.

The video explains why the version numbering skips from Sonnet 4.6 to 4.8, arguing that Opus and Sonnet version numbers are independent internal tags reflecting training lineage rather than product tier. Since Opus 4.7 was released on April 16th, the presenter claims the next Sonnet will be 4.8, not 4.7.

On expected features, the video claims Sonnet 4.8 will likely inherit improvements seen in Opus 4.7, including a major vision upgrade (jumping from ~54% to over 98% accuracy on a vision benchmark, with 3x higher resolution support), a 12-point jump on coding benchmarks, more literal instruction following, and a new effort level called 'XHi' sitting between high and max.

The video also highlights a feature codenamed 'Kairos,' referenced over 150 times in the leaked code, described as a persistent background agent that runs autonomously, manages memory, and can perform tasks like fixing bugs or conducting code reviews without user prompting. Additionally, 44 hidden feature flags are mentioned, including 'session teleportation,' 'autonomous overnight operation,' and an 'advisor mode.'

The presenter also references a model family called 'Mythos' (already partially released for defensive cybersecurity use as of April 7th) and a tier above Opus called 'Capybara,' suggesting a broader product lineup overhaul is underway. An 'undercover mode' is also mentioned, which reportedly strips internal tags when Anthropic employees use Claude Code on outside projects — and the fact that Sonnet 4.8 was on the blocked names list is cited as evidence the model is real.

The video closes with practical preparation advice for users (saving prompts, building test sets, planning for token usage changes, avoiding hardcoded model names) and promotes the creator's paid community, AI Profit Boardroom, and AI Success Lab.