Anthropic’s Secret AI Model Mythos Audits Entire Zcash Protocol, Finds No New Bugs

Zooko Thanks Anthropic After Full Protocol Audit

The statement came directly from Zooko, the online handle for Zooko Wilcox-O’Hearn, computer security specialist, cryptographer, and co-creator of Zcash. Writing on X, he said:

“Thanks, Anthropic, for helping protect Zcash users. At Shielded Labs’s request, they ran a security audit of Zcash with Mythos. It did not find any more serious bugs in the Zcash protocol. Shielded Labs and others are continuing security hardening work. Stay tuned for updates.”

The post arrived one week after the public disclosure of a critical soundness bug in the Orchard shielded pool, which had triggered a 38% to 50% price collapse in ZEC within 48 hours of going public on June 4 and 5.

What Mythos Is and Why It Matters

Anthropic’s Mythos Preview is the company’s most advanced AI model, introduced in April 2026 as part of its Project Glasswing defensive security initiative. Unlike the Claude models available to the general public, Mythos is not publicly accessible. Anthropic restricts access to a limited group of trusted partners, including major technology companies and critical infrastructure projects, precisely because of its capabilities in autonomous security research, zero-day vulnerability detection, and complex codebase analysis.

Many observers in the X thread wondered how the Zcash team was allowed to use Mythos. Zooko’s statement came just before both Claude’s Fable 5 and Mythos were shut down by the U.S. government this weekend. Image source: X.

Shielded Labs, the nonprofit organization supporting Zcash development, secured access to Mythos and directed the audit at the entire Zcash protocol.

The Orchard Bug That Triggered the Crisis

The Mythos audit follows a harrowing episode for Zcash holders. In late May 2026, security researcher Taylor Hornby, working under contract with Shielded Labs, used a custom AI auditing framework built around Claude Opus 4.8 to identify an under-constrained circuit element in the Orchard shielded pool’s zero-knowledge proof system. The flaw had existed since Orchard’s activation in May 2022 and had gone undetected for approximately four years despite prior expert audits.

The bug represented a supply- inflation risk. An attacker with sufficient technical knowledge could have minted counterfeit ZEC inside the privacy pool, entirely undetectable on-chain.

Developers moved fast. A soft fork on June 2 temporarily disabled all Orchard actions. A hard fork on June 3, the NU6.2 upgrade, activated a corrected circuit and re-enabled Orchard with no chain split.

Public disclosure on June 4 and 5 still triggered a sharp selloff. ZEC fell from a pre-disclosure price near $624 to intraday lows approaching $300 on some exchanges, wiping billions from the market cap in hours.

What the Clean Audit Means for ZEC Holders

The Mythos result does not close the book on security work. Zooko was explicit that efforts continue. Shielded Labs and other contributors are pressing forward with security hardening, which includes formal verification of the Orchard circuit, additional AI-assisted auditing, and plans to hire a Head of Security and a dedicated cryptographer.

The Ironwood upgrade, targeting activation in late July 2026, will deploy a new shielded pool using the corrected Orchard circuit and enforce stricter turnstile accounting to allow independent supply verification. The Ironwood proposal directly addresses lingering questions about supply integrity that the Orchard bug introduced.

ZEC Price Holds Above $400

As of June 13, ZEC trades in the $411 to $416 range, stabilizing above the $400 support level after recovering 45% to 80% from June 5 lows. The market cap sits near $6.9 to $7.0 billion. ZEC ranks in the top 12 to 15 cryptocurrencies by market cap at current prices.

The Mythos audit result, combined with the speed of the emergency fix and the Ironwood roadmap, has supported the recovery. Price remains well below the June 4 peak near $624, with the next major catalyst likely tied to progress on Ironwood.

Security Work Continues

Zooko’s statement closed with a clear signal: this is not a declaration of completion. “Stay tuned for updates,” he wrote, pointing to an ongoing program that now includes some of the most advanced AI security tooling available anywhere.

For ZEC holders, the clean Mythos audit provides meaningful reassurance after a turbulent two weeks. The protocol’s most powerful available reviewer found nothing new. The team is still looking.