Context compaction triggers at ~16% usage on Opus 4.6 (1M context)

Bug

Context compaction is firing at approximately 16% context utilization on Opus 4.6 (1M context). In my current session, compaction has triggered twice despite being nowhere near context limits.

Expected behavior

Compaction should trigger at a much higher utilization threshold — closer to 80-90%, not 16%.

Environment

• Model: Claude Opus 4.6 (1M context) — claude-opus-4-6[1m]
• Platform: macOS (Darwin 25.2.0)
• Shell: zsh

Notes

The 1M context window is appreciated, but the early compaction negates much of the benefit. It appears the compaction threshold may not have been updated to account for the larger context size.