When Your AI Skill Calls a Ghost: Retiring Zombie Models in Anthropic Skills

In the world of autonomous AI agents, a recent discovery revealed that outdated, retired models could cause issues when trying to access them. This happened when an agent pipeline attempted to summon a dead model, resulting in a 404 error from the Anthropic API. The source of truth for these model details is provided in the official anthropics/skills repository, specifically in the skills/claude-api/shared/models.md and skills/claude-api/shared/model-migration.md files.

The problem arose when the author noticed several models in the model-migration.md file were marked as "Deprecated" even though their retirement dates had already passed. These models included claude-opus-4-20250514, claude-sonnet-4-20250514, claude-3-haiku-20240307, and claude-opus-4-1-20250805. The author submitted a pull request (PR) to correct this documentation issue, but the changes were not immediately accepted.

A few hours later, an automated AI agent named Hermes performed a review of the PR. Hermes found two inconsistencies that the human author had missed: a one-day discrepancy in the retirement date of claude-3-haiku-20240307 and a missing entry for claude-opus-4-1-20250805 in the corresponding migration table. These inconsistencies could have led to confusion for users relying on the documentation for their AI applications.

The author reviewed the official release timeline and updated the documentation accordingly. They added claude-opus-4-1-20250805 to the Retired table in both files and standardized the retirement date for Claude 3 Haiku to April 19, 2026. This ensured cross-file consistency in the documentation. Hermes approved the changes, highlighting the importance of automated babysitters in reviewing PRs and catching human oversights before they reach the core maintainers.