Claude Code v2.1.166: Fallback Model Config, Expanded Deny-Rule Globs, Cross-Session Security
Anthropic
Claude Code v2.1.166 (first seen June 6) adds a `fallbackModel` setting to configure up to three fallback models tried in order when the primary model is overloaded, expanded deny-rule glob support, and hardened cross-session message security. Also disables thinking on models that think by default via `MAX_THINKING_TOKENS=0` and per-model toggles. Fixes a wide range of terminal, auth, session, and UI bugs including recurring JetBrains terminal rendering issues, PowerShell command validation hangs, and voice-mode auth clearing. Two earlier releases on June 5 (v2.1.163, v2.1.165) added `/plugin list` with filtering, `requiredMinimumVersion`/`requiredMaximumVersion` managed settings, and hooks returning `additionalContext`.
Why it matters
The fallback model configuration is a meaningful reliability improvement for production deployments where primary model availability can be unpredictable.
Importance: 2/5
Official GitHub releases; three releases in two days with meaningful enterprise reliability and security improvements.