[Bug] Terminal hangs during agent operations with 5+ minute input lag

Bug Description
Bug Report - Terminal Hanging/Lag Issue

Version: Claude Code CLI v2.1.37 (regression started after v2.1.20)

Issue: Terminal becomes completely unresponsive during agent operations. Cannot type input while
agent is working. 5+ minute hang before agent starts responding to submitted messages. Severe UI
lag throughout session.

Frequency: Consistent across all sessions, regardless of model (Opus 4.6, Sonnet 4.5)

Impact: Completely blocks productive work. User paying $100/Month for service that's unusable.

Environment:

• OS: Windows 11
• Terminal: PowerShell (qiskit_env)
• Session type: Long-running technical work sessions (100K+ tokens typical)
• Hardware: RTX 3060 12GB x2, 64GB RAM

Expected: Agent works in background, terminal remains responsive for user input during agent
operations.

Actual: Terminal freezes completely during agent tool execution. 5-min delays before agent begins
processing messages.

Reproducible: Yes, every session since v2.1.20.

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 2.1.37
• Feedback ID: 8524bd45-c8dc-4309-a6af-2ce1c320aff3

Errors

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