May 05, 2026 • Version: 2026.5.7

[Regression] post-attach.update-sentinel ~9s Sync Block Per model_call in v2026.5.7

The update-sentinel check now executes on every post-attach phase instead of only at startup, causing ~9 second event loop blocks in regions with poor npm/GitHub connectivity.

🔍 Symptoms

Primary Manifestations

The regression introduces synchronous blocking during the post-attach lifecycle phase, which was previously instantaneous:

[diagnostic] liveness warning: reasons=event_loop_delay,event_loop_utilization,cpu
  interval=30s
  eventLoopDelayP99Ms=15854.5
  eventLoopDelayMaxMs=15854.5
  eventLoopUtilization=0.997
  cpuCoreRatio=1.004
  active=0
  waiting=0
  queued=1
  phase=channels.feishu.start-account
  recentPhases=sidecars.model-prewarm:13047ms,post-attach.update-sentinel:9336ms
  work=[queued=agent:main:main(idle/model_call,q=1,age=0s last=model_call:started)]

Before vs After Comparison

Phase	Before (v2026.5.6)	After (v2026.5.7)
`post-attach.update-sentinel`	0ms	9336ms
`sidecars.model-prewarm`	10212ms	13047ms
Total blocking before AI call	~10s	~22s
`eventLoopUtilization`	Normal	0.997 (saturated)

Observable Symptoms

Repeated liveness warnings every 30 seconds containing event_loop_delay and event_loop_utilization reasons
CPU saturation at 100% (cpuCoreRatio=1.004) despite idle async work
Phase jamming: channels.feishu.start-account phase blocks indefinitely
Feishu websocket healthy: bot open_id resolves correctly, but sentinel check blocks alongside it
Model responses delayed by 20+ seconds per invocation

Reproduction Trigger

Every model_call now triggers the post-attach.update-sentinel phase. The blocking duration scales with network latency to npm registry or GitHub endpoints.

🧠 Root Cause

Architectural Shift in v2026.5.7

The regression stems from a lifecycle placement change for the update sentinel check: