Anthropic's July 20 update to Claude Code, version 2.1.216, fixed a normalization bug that made sessions get quadratically slower with every turn, not linearly slower. The bug caused computational cost to grow quadratically with session length, meaning each doubling of session length quadrupled the normalization cost. For a 50-turn session, a linear algorithm takes 50 units of work, while the quadratic version runs at 2,500 units — a 50-fold difference. The fix restructures normalization to a single linear scan, making performance independent of turn accumulation. This fix most benefits developers running 50- and 100-turn auto mode sessions, which became generally available on July 10, 2026. The release also included a new sandbox.filesystem.disabled configuration option, a correction for OAuth token rotations surfacing as false permission denials, and agent session-restore improvements. The update landed amid at least six separate platform disruptions between July 16 and July 22 that complicated its rollout.