hermes-claude-auth is a runtime patching tool that enables hermes-agent to use Claude Code subscription credentials by bypassing Anthropic's server-side OAuth validation. It works through a Python import hook that monkey-patches hermes-agent's anthropic adapter to modify outgoing API requests with proper billing headers, system prompt restructuring, and Claude Code fingerprint matching. The tool consists of three main components: the core bypass logic (anthropic_billing_bypass.py) that implements complex request transformation, an import hook mechanism (sitecustomize_hook.py) for runtime patching, and installation/uninstallation scripts. The bypass handles billing header signing, system prompt relocation, tool name namespacing, Stainless header spoofing, tool pair repair, effort stripping for haiku models, temperature fixing for Opus 4.6, and account metadata mapping. It's designed to be idempotent and tracks upstream changes from the opencode-claude-auth project.