CLI: Task execution escapes to PowerShell, becomes unresponsive

[ThatDragonOverThere]

Description

While executing a task, Claude Code somehow escapes/drops to PowerShell and becomes unresponsive. The task starts but control transfers to the underlying shell.

Environment

• Platform: Claude Code CLI (latest version)
• OS: Windows 10/11
• Shell: PowerShell
• Date observed: January 28, 2026

Behavior

1. Start a task in Claude Code
2. Task begins execution
3. Somehow "escapes" to PowerShell
4. Claude Code becomes unresponsive
5. Cannot continue working - requires restart

Related

This may be related to #21266 (input focus lost to PowerShell after gh commands), but this occurs during general task execution, not specifically after gh commands.

Expected Behavior

Task should execute within Claude Code without losing control to the underlying shell.

Actual Behavior

Control transfers to PowerShell mid-task, leaving Claude Code in an unresponsive state.

[ThatDragonOverThere]

Closing as duplicate of #21266 (input focus lost to PowerShell). Same root cause - control escaping to underlying shell.

[ThatDragonOverThere]

Reopening - this is a distinct issue from #21266. Focus loss is a different symptom than the app escaping to PowerShell and becoming completely unresponsive during task execution.

[ThatDragonOverThere]

Detailed Reproduction - Long-Running Task on Windows

Environment:

• Claude Code on Windows
• PowerShell terminal

What Was Happening

• Claude Code actively running a simulation task (54m 6s elapsed, 1.6k tokens)
• Agent was mid-workflow: "Re-run simulation and collect comparison numbers"
• Multiple sub-tasks were completed (shown with strikethrough)
• 6 files with pending edits (+351 -124 lines) awaiting acceptance

The Bug

Claude Code unexpectedly dropped out of the agent interface back to the raw PowerShell prompt. The terminal shows:

(tradingalertslive) PS C:\Users\Cassie\Desktop\trading_system> [0[Iplease continue

Notice the garbled escape sequence [0[I before "please continue" — this suggests:

1. CC lost control of the terminal
2. User input that should have gone to the CC agent went directly to PowerShell instead
3. The escape codes that CC uses for its UI leaked into the prompt

Expected Behavior

Typing "please continue" should have been interpreted by Claude Code as a continuation instruction.

Actual Behavior

Input went directly to PowerShell as a malformed command.

Possible Triggers

• Long-running task (54+ minutes)
• Large pending edit queue (6 files)

Note: This happens consistently, not tied to any specific terminal setup or remote session.

[ThatDragonOverThere]

New Reproduction — Feb 10, 2026

Version: Bun Canary v1.3.9-canary.51 (d5628db2) Windows x64
Claude Code version: Latest (Opus 4.6)
OS: Windows 11

What Was Happening

Claude Code was running a long sub-agent task (Step 4 verification gates on a 2.8 GB parquet file). Three parallel sub-agents were active:

✽ Running Step 4 verification… (11m 29s · ↓t12.0k tokens)
  ⎿  ◼ Step 4 verification gates + score continuity check
     ◼ Run Step 4 verification gate checks on trading system (3,910 → 7,157)
     ◼ Run Step 4 verification gates on ALL_MFE_MOMENTS.parquet

Multiple prior tasks were completed (shown with ✔ checkmarks). The task list, todo spinners, and UI were all rendering normally.

The Bug

Mid-execution (~11.5 minutes into the sub-agent run), Claude Code dropped out to the raw PowerShell prompt:

(tradingalertslive) PS C:\Users\Cassie>

The user's queued input messages (typed while the agent was working) were dumped directly into PowerShell instead of being interpreted by Claude Code. The CC TUI vanished entirely — no garbled escape codes this time, just a clean drop to shell.

Key Details

• Trigger: Long-running parallel sub-agents (~11+ minutes)
• Sub-agent output was LOST — the verification gate results were never returned
• Todo list state preserved on screen but non-interactive (rendered as dead text)
• No crash dialog or error — just silently dropped back to PS prompt
• This is now the 4th reproduction of this bug (previous: 54m task, gh command, and another long task)

Pattern

Every reproduction involves either:

1. Long-running tasks (11-54+ minutes), OR
2. Shell-invoking operations (gh commands)

The common thread seems to be the terminal control handoff — when CC delegates to a subprocess (sub-agent or shell command) for an extended period, it loses control of stdin/stdout and never recovers.