Rendering Performance and Stability Hardening in v2.1.70

A Stability and Performance Release

Claude Code v2.1.70, released on March 6, 2026, ships zero new headline features. Instead, Anthropic focused the release entirely on performance improvements and fixing edge-case reliability issues that had accumulated across previous versions.

Performance Improvements

Rendering Efficiency

Prompt input re-renders during turns have been reduced by approximately 74%, achieved by isolating animated elements and stabilizing component memoization. The spinner performance was also improved by decoupling the 50ms animation loop from the surrounding shell, reducing CPU overhead during active turns.

Startup Memory Savings

Two startup-time memory reductions ship in this version. Users without custom CA certificates benefit from a ~426KB reduction in startup memory. More significantly, baseline memory at startup was reduced by ~16MB by deferring Yoga WASM preloading until it is actually needed.

Remote Control Server Load

The Remote Control /poll interval while connected has been changed from 1–2 seconds to once every 10 minutes, reducing server load by approximately 300x.

Long Session Memory

Multiple memory reductions for extended sessions are included: reduced memory footprint for SDK and CCR sessions using stream-json output, reduced memory usage when resuming large sessions including compacted history, and improved memory usage in long sessions by stabilizing onSubmit across message updates.

Bug Fixes

Proxy and Gateway Compatibility

Two significant fixes address enterprise environments using third-party API gateways. First, API 400 errors when using ANTHROPIC_BASE_URL with a third-party gateway are resolved. Second, the effort parameter error when using custom Bedrock inference profiles is fixed.

Voice Mode on Windows

Voice mode was failing on the Windows native binary with "native audio module could not be loaded," and push-to-talk was not activating on session start. Both issues are corrected.

Clipboard and Text Rendering

Clipboard operations involving non-ASCII text — CJK characters and emoji — were being corrupted on Windows and WSL. The fix routes these operations through PowerShell Set-Clipboard instead.

Other Notable Fixes

• Fixed empty model responses immediately after ToolSearch
• Fixed Enter inserting a newline instead of submitting over slow SSH
• Fixed repeated "Model updated to Opus 4.6" notifications
• Fixed feature flags read during early startup never refreshing their disk cache
• Fixed skill listing being re-injected on every --resume (~600 tokens saved per resume)