Auto-compact cannot be disabled — consolidated report with measurements #42817

Summary

This is a consolidated report covering the full auto-compact disable problem. It unifies 7+ existing issues with new measurements and reproduction data that none of the individual issues provide.

Core problem: There is no working method to prevent automatic context compaction. Every documented approach fails silently. This makes long sessions fundamentally unreliable.

What doesn't work (tested on v2.1.90, Opus 4.6 1M context)

New data: compaction triggers at ~35% context usage

I built a PostToolUse hook (context-watchdog.sh) that estimates cumulative token usage per session. Measurements from a real session (Apr 2, 2026):

• Session: omniquant-v2, Opus 4.6, 1M context window
• Estimated tokens at compaction: ~346K (~35% of 1M)
• Expected compaction: never (auto-compact disabled) or at ~95% (emergency)
• Actual: compacted mid-task, unprompted, at ~35%

This is not an emergency compaction near the context limit. The system is actively compacting at a third of capacity despite every available "disable" setting being off.

Impact

1. Context loss mid-task: Compaction discards decisions, file paths, variable names, and reasoning that cannot be recovered from code alone
2. Silent failure: No warning, no event, no hook fires before it happens (PreCompact hook exists but the compaction itself is the problem — it shouldn't happen at all)
3. Workarounds don't work: Users build elaborate hook systems (I have 3 hooks + snapshot persistence) but they're mitigating a problem that shouldn't exist
4. Trust erosion: Users cannot rely on Claude Code for any session longer than ~30 minutes of active tool use

What this issue is NOT

This is not a duplicate of any single existing issue. Each prior issue reports one symptom. This issue documents:

• All disable methods tested and failed (table above)
• Measured trigger point (35%, not 83% or 95%)
• The CLAUDE_AUTOCOMPACT_PCT_OVERRIDE Math.min() bug that prevents raising the threshold
• The gap between "auto-compact: false in /config UI" and actual behavior

Related issues (all open or closed-not-planned)

• autoCompactEnabled setting not recognized — no way to disable auto-compact #38483 — autoCompactEnabled not in schema
• autoCompact: false ignored - compaction triggers at ~78% #18264 — autoCompact: false ignored, triggers at ~78%
• [BUG] Context limit reached · /compact or /clear — forced at ~85% with autoCompact: false (Opus 4.6, v2.1.39) #24856 — Hard stop at ~85% with autoCompact: false
• [DOCS] No documentation for disabling auto-compaction #24589 — No documentation for disabling
• CLAUDE_AUTOCOMPACT_PCT_OVERRIDE cannot raise threshold above default (~83%) #31806 — CLAUDE_AUTOCOMPACT_PCT_OVERRIDE cannot raise threshold (Math.min bug)
• [FEATURE] Add --no-auto-compact command switch to Disable the auto-compaction #6689 — Feature request: --no-auto-compact flag
• [FEATURE] Add claudeCode.autoCompact settings to control context compaction behavior #10691 — Feature request: proper autoCompact settings

Proposed fix

In order of preference:

1. Respect the setting: When autoCompactEnabled is false (via any method), do not compact. Period. Let the user hit the context wall and decide.
2. Fix the Math.min bug: Allow CLAUDE_AUTOCOMPACT_PCT_OVERRIDE to raise the threshold above default, not just lower it.
3. Add a real CLI flag: --no-auto-compact that definitively prevents automatic compaction.
4. At minimum: Document honestly that auto-compact cannot be disabled, so users stop wasting time on settings that do nothing.

Reproduction

# 1. Disable auto-compact via all available methods
claude config set -g autoCompactEnabled false
# In settings.json env: "DISABLE_AUTO_COMPACT": "true"
# In /config UI: Auto-compact → false

# 2. Start a session with moderate tool use (~50 tool calls)
# 3. Monitor with a PostToolUse hook counting estimated tokens
# 4. Observe: compaction triggers at ~30-40% context usage

Environment

• Claude Code v2.1.90
• Model: Opus 4.6 (1M context)
• Platform: macOS Darwin 25.3.0
• Plan: Claude Max