Anthropic News | Claude Code v2.1.166 Adds Fallback Model Configuration
With Claude Code releases coming in rapid succession, many developers may be wondering which updates are worth their attention. In this article, the Clauder Navi editorial team covers two releases from June 6 as official Anthropic information for June 7, 2026: v2.1.166 (a major feature release adding fallback model configuration, deny glob patterns, the ability to disable thinking mode, and more) and the maintenance release v2.1.167.
The biggest news for June 7, 2026 is Claude Code v2.1.166, released on June 6. The headline feature is the addition of fallback model configuration (fallbackModel), which allows up to three alternative models to be automatically tried when the primary model is unavailable due to high load or other reasons. This is a practical improvement that reduces waiting time and manual retries for long-running tasks and team workflows. Also notable is the addition of glob pattern support in deny rules, allowing "*" to block all tools at once — a useful addition for organizations looking to enforce stricter security policies.
v2.1.166 is also packed with bug fixes. JetBrains IDE (IntelliJ / PyCharm / WebStorm 2026.1+) terminal flickering, Windows PowerShell hangs, and macOS daemon CPU spikes are all addressed in a single release, making this a significant update for teams working across multiple platforms. A crash affecting background sessions inside git worktrees has also been fixed, providing clear benefits for developers who manage multiple branches in parallel.
v2.1.167, released roughly 40 minutes after v2.1.166, is described only as "bug fixes and reliability improvements" with no individual items disclosed — it appears to be a maintenance patch following v2.1.166. If you have run claude update, this version will have been applied automatically. There are no new posts on the Anthropic News or Engineering Blog today; the story of the day is the accelerating pace of Claude Code development.
目次 (5)
[1] Claude Code v2.1.166 — Adds Fallback Model Configuration and Thinking Mode Control
On June 6, 2026, at 09:55 JST, Anthropic released Claude Code v2.1.166. Source: claude-code v2.1.166 Release Notes.
The most significant addition in this release is fallback model configuration (fallbackModel). You can now specify up to three alternative models in your configuration file alongside the primary model; if the primary model is unavailable due to high load or other reasons, the system automatically switches to the next option. This directly improves stability for enterprise use cases and long-running tasks. Engineer impact: ★★★
Next, glob pattern support in deny rules has been added. You can now use "*" to block all tools at once. Previously, individual tool names had to be enumerated, but security policies can now be written more concisely. Engineer impact: ★★
In addition, explicit disabling of thinking mode is now supported. By specifying MAX_THINKING_TOKENS=0 or --thinking disabled, you can explicitly turn off thinking steps. This makes it easier to control costs in situations where a simpler approach is preferred. Engineer impact: ★★
Bug Fix Details
v2.1.166 also includes several practical bug fixes.
- JetBrains IDE: Terminal flickering in IntelliJ / PyCharm / WebStorm 2026.1 and later has been resolved. This is a significant fix for Java and Kotlin developers.
- Windows PowerShell: A hang that occurred during certain operations has been fixed.
- macOS daemon: A CPU spike in the background daemon process has been fixed, improving stability in environments where Claude Code runs as a persistent process.
- git worktree: A crash affecting background sessions inside a worktree has been resolved. This is a significant fix for developers who manage multiple branches in parallel.
All of these fixes span platforms and work styles, and together represent improvements that many engineers who use Claude Code daily will notice.
[2] Claude Code v2.1.167 — Maintenance Release with Bug Fixes and Reliability Improvements
On June 6, 2026, at 10:33 JST — roughly 40 minutes after v2.1.166 — Claude Code v2.1.167 was released. Source: claude-code v2.1.167 Release Notes.
The release notes state only "Bug fixes and reliability improvements" with no individual changes listed. This appears to be an immediate patch aimed at stabilizing the fallback model configuration, glob pattern support, and thinking mode control introduced in v2.1.166. If you have already applied the latest version via claude update, this version will have been applied automatically. No special action is required. Engineer impact: ★
What to Watch Next
There are no new posts on Anthropic News or the Engineering Blog today — it has been a day focused solely on Claude Code tooling updates. v2.1.163 (June 4) added version management settings and a plugin list command, and now v2.1.166 brings fallback models, deny glob patterns, and thinking mode control. Feature enhancements that support stable operation for teams and organizations continue to accumulate, and a clear direction toward enterprise governance capabilities is emerging. The next question is when the next post will come from Anthropic News or the Engineering Blog, which have been quiet for a while. The Clauder Navi editorial team will continue to keep you updated.
Sources
- Claude Code v2.1.166 Release Notes: https://github.com/anthropics/claude-code/releases/tag/v2.1.166
- Claude Code v2.1.167 Release Notes: https://github.com/anthropics/claude-code/releases/tag/v2.1.167
- Anthropic News: https://www.anthropic.com/news
- Anthropic Engineering Blog: https://www.anthropic.com/engineering
