Fable 5.1 as default, Containment Escape rule tightens auto-approval scope. 40+ fixes are quiet but critical for operational stability
Claude Code v2.1.257: Fable 5.1 Release and Enhanced Security Controls
Original: v2.1.257
Importance: マイナーバージョンアップで新モデル追加と多数のバグ修正が含まれるが、破壊的変更なく既存ワークフロー継続可能
Summary
Claude Code v2.1.257 introduces Claude Fable 5.1 as the default Fable model with 1M context window and cache reads at $0.25/Mtok. Major additions include timezone/time format settings, a new Containment Escape rule blocking auto-approved cloud metadata fetches and cross-tenant egress, and session-level effort adjustment. Over 40 bug fixes address session dispatch logic, keybinding conflicts in claude agents, Remote Control prompt-cache issues, credential/auth header conflicts across Bedrock/Vertex/Foundry, and telemetry handling on warm starts.
Key Points
- Claude Fable 5.1 now default with 1M context, pricing $10/$50/Mtok
- Containment Escape rule restricts auto-approved metadata fetches for better security
- 40+ bug fixes, especially session management and auth header issues
- CLAUDE_CODE_SUBAGENT_MODEL_FORCE enables flexible subagent model override
- Time format & timezone settings added for localization support
Source: https://github.com/anthropics/claude-code/releases/tag/v2.1.257
Outlet: Claude Code Releases
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