Claude Code version 2.1.257 introduces Claude Fable 5.1 as the new default Fable model, featuring a 1M context window and specific pricing tiers. The update also adds time format settings for timestamps and enhances security with a Containment Escape rule in auto mode.
- Added Claude Fable 5.1 (`claude-fable-5-1`) as the default Fable model with 1M context, $10/$50 per Mtok pricing, and $0.25/Mtok cache reads.
- Introduced `timeFormat` and `timeZone` settings to customize turn-end clock and transcript-view timestamps.
- Implemented a Containment Escape rule in auto mode to prevent auto-approval of cloud metadata-credential fetches and egress evasion unless expected.
- Added `CLAUDE_CODE_SUBAGENT_MODEL_FORCE` environment variable to apply subagent model overrides universally.
- Fixed numerous issues including background session stability, permission handling, and gateway credential management.
This release provides users with a new default model option and improves security posture by restricting automatic approvals for sensitive cloud operations.