Claude Code 2.1.216 Update: Fixes Lag and Boosts Security

Claude Code CLI recently released version 2.1.216, bringing 40 CLI changes and 1 system prompt adjustment. This update optimizes flexibility by adding a sandbox toggle, completely fixes the long-session lag issue, and significantly strengthens overall security and permission controls.

Key Details and Performance Fixes

According to @ClaudeCodeLog, the new version adds the sandbox.filesystem.disabled option, allowing users to bypass file system isolation while retaining network egress control. Additionally, the update removes an irrelevant Bun HMR log and specifically fixes the quadratic lag issue in long sessions, greatly improving the interactive experience.

Security Hardening and Defense Mechanisms

@AlexKim points out that the changelogs for 2.1.214 and 2.1.216 read like a strict security audit report. Bash permission checks now default to a "fail-deny" strategy, introduce an interception mechanism for commands exceeding 10,000 characters, and defend against potential permission bypasses using Unicode spoofing.

System Prompt Changes

Details from @ClaudeCodeLog indicate that the token count for the system prompt in this version increased by 14.0% (an addition of 3,099 tokens). This raises the system prompt's proportion from 38.4% to 52.3%, while the tool-related proportion correspondingly drops to 47.7%.

2026-07-21 ~ 2026-07-22 · 5 related posts

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