Autocompact regression since 2.1.153 (up to the latest 2.1.161 version): "0% until auto-compact" replaced by "100% context used", compaction never triggers

Bug Description

Auto-compact stopped triggering between versions 2.1.152 and 2.1.153. The status bar indicator changed from 0% until auto-compact (working) to 100% context used (broken), and compaction never fires — sessions hit 100% context and die.

Still broken on the latest version (2.1.161 as of 2026-06-03).

Screenshots showing both indicators — will attach below.

<img width="395" height="124" alt="Image" src="https://github.com/user-attachments/assets/b0e3f707-3f20-4bd9-940d-0996ad35c964" />

<img width="366" height="113" alt="Image" src="https://github.com/user-attachments/assets/c250e5f8-1526-44ac-a93d-ddac84c36c02" />

Bisect

| Version | Status | Indicator |
|---------|--------|-----------|
| 2.1.150 | OK | 0% until auto-compact |
| 2.1.152 | OK | 0% until auto-compact |
| 2.1.153 | BROKEN | 100% context used |
| 2.1.154 | BROKEN | 100% context used |
| 2.1.161 (latest) | BROKEN | 100% context used |

Bisected by downloading native binaries for each version from npm (@anthropic-ai/claude-code-linux-x64@VERSION) and switching via symlink. The regression is between 2.1.152 and 2.1.153.

Setting "autoCompact": true in ~/.claude/settings.json does not fix the issue.

Environment

• Platform: Linux x86_64 (glibc)
• Model: claude-opus-4-6
• Context: 200k (Claude Max)
• Versions tested: 2.1.142 through 2.1.161
• Settings: effortLevel: "high", alwaysThinkingEnabled: true

2.1.153 changelog review

Nothing in the 2.1.153 changelog mentions autocompact or context management. Likely candidates for the silent regression:

• /model now saves selection as the default for new sessions — model picker was refactored (previous autocompact threshold bug in 2.1.141 was also caused by /model changes)
• "Fixed excessive memory usage (multiple GB) when resuming a session" — session loading refactor may have affected context size checking

Related issues

• #64504, #64277, #64370, #63426 — all report autocompact not triggering on recent versions
• #63186, #64773 — CLAUDE_AUTOCOMPACT_PCT_OVERRIDE silently ignored