Autocompact silently disabled for Bedrock/Vertex users since v2.1.154

Summary

Autocompact stopped firing automatically for Bedrock users starting around v2.1.154. Sessions fill to 100% context without compacting; manual /compact still works fine.

Environment

• Claude Code version: 2.1.160
• API provider: AWS Bedrock (CLAUDE_CODE_USE_BEDROCK=1, ANTHROPIC_API_PROVIDER=bedrock)
• Model: us.anthropic.claude-sonnet-4-6
• OS: Windows 11
• CLAUDE_CODE_AUTO_COMPACT_WINDOW: not set (before fix)
• CLAUDE_CODE_MAX_OUTPUT_TOKENS: 12288

Root Cause (traced through binary)

The daf() function — which decides whether to compact on each turn — contains this guard:

if (fWH() && !rc() && !q68(q, $)) return false;

Where:

• fWH() = !CLAUDE_CODE_REMOTE → always true in local sessions
• rc() = reads GrowthBook feature flag tengu_amber_redwood3 → always false for Bedrock users because px() (GrowthBook availability) requires Cz() (firstParty provider), which is false for Bedrock
• q68(q, $) = true only if CLAUDE_CODE_AUTO_COMPACT_WINDOW is set via env or settings → false by default

With all three conditions true, daf() returns false unconditionally — autocompact never fires, regardless of context usage.

The chain:

• px() = !DISABLE_GROWTHBOOK && mx() = !DISABLE_GROWTHBOOK && !UI()
• UI() = wD9() || l3() !== null || Z58()
• wD9() = !PROVIDER_MANAGED_BY_HOST && !Cz() → true for all non-firstParty providers (Bedrock, Vertex)
• Therefore px() = false for Bedrock users → GrowthBook feature flags always return defaults
• L8("tengu_amber_redwood3", "") returns "" (falsy default) → rc() = false

This appears to have been introduced when the "reactive" compaction path was added. The guard is intended to route Bedrock users through the non-reactive path — but a logic error causes it to skip compaction entirely instead.

Evidence

Session transcripts show:

• v2.1.126–v2.1.150: 15+ successful trigger: "auto" compact events, preTokens ~175K
• v2.1.154+: zero trigger: "auto" events; only trigger: "manual" after user runs /compact
• Non-compacting sessions peaked at 176K tokens (above the 174K threshold of effectiveWindow - 13000)

Workaround

Setting CLAUDE_CODE_AUTO_COMPACT_WINDOW=200000 in settings.json makes q68() return true, which bypasses the broken guard and restores autocompact behavior via the standard (non-reactive) path.

Expected Behavior

Bedrock/Vertex users should have autocompact work identically to firstParty API users. Being excluded from a server-side A/B experiment (tengu_amber_redwood3) should not disable autocompact — it should simply use the non-reactive code path.

Suggested Fix

The guard condition should use || instead of && for the experiment check, or the non-reactive path should be taken (rather than skipping compaction entirely) when rc() is false and no explicit window is configured:

// Current (broken for Bedrock):
if (fWH() && !rc() && !q68(q, $)) return false;

// Fix option 1: fall through to non-reactive path when rc() is false
if (fWH() && !rc() && !q68(q, $)) {
  // continue to non-reactive compact path below, don't return false
}

// Fix option 2: only skip if user explicitly disabled compact window
if (fWH() && !rc() && !q68(q, $) && autoCompactWindowExplicitlyDisabled) return false;