Summary
Released July 22, 2026, Claude Code v2.1.218 fixes a bug where message-normalization cost grew quadratically with the number of turns, causing multi-second stalls and slow resumes in long auto-mode sessions, and resolves a class of false command denials when an OAuth token expired or rotated mid-session.
What changed
Claude Code v2.1.218 eliminated quadratic growth in per-turn message normalization that stalled long sessions, and fixed auto mode incorrectly denying commands when an OAuth token expired or rotated mid-session.
Why it matters
Long-running autonomous coding sessions are where these bugs bit hardest; removing the quadratic slowdown makes extended auto-mode work usable at scale, and fixing token-rotation denials removes a confusing class of interruptions, both improving reliability for agentic coding workflows.
Evidence excerpt
Fixed a slowdown in long sessions where message normalization cost grew quadratically with the number of turns, causing multi-second stalls and slow resumes.