Context fills extremely fast, forced compact at ~70% instead of 99%

Description

For the past several days, the context window fills up much faster than before. The session gets blocked at approximately 70% capacity and forces a compact, whereas previously it worked smoothly until ~99%.

This issue was slightly improved a few days ago but is still present.

Impact

• Implementation work is nearly impossible due to constant compacting
• Session becomes unusable very quickly
• Even with auto-compact disabled, manual compact is forced at ~70%

Steps to reproduce

1. Start a new session with Opus 4.5
2. Work normally (reading files, making edits, implementing features)
3. Context reaches ~70%
4. Session blocks and demands compact - cannot continue without compacting

Expected behavior

• Context should be usable until ~99% before requiring compact
• With auto-compact disabled, user should have control over when to compact

Actual behavior

• Session blocks at ~70% and forces compact
• Context fills up much faster than it did previously
• Makes normal development workflow very difficult

Environment

• Model: Opus 4.5 (claude-opus-4-5-20251101)
• Claude Code: Latest version
• OS: Linux

Additional context

This behavior change seems to have started recently. The same workflows that previously allowed full sessions now require multiple compacts.