Copilot CLI Feedback: PowerShell Process Leak on Windows

[takurooper]

Describe the bug

Copilot CLI Feedback: PowerShell Process Leak on Windows

Issue

Copilot CLI does not clean up winpty-agent and pwsh processes after tool execution on Windows, causing significant memory accumulation over time.

Environment

• OS: Windows 11
• Shell: PowerShell 7 (pwsh)
• Copilot CLI: latest version
• Terminal: Windows Terminal

Observed Behavior

When Copilot CLI executes the powershell tool, it spawns a winpty-agent → pwsh process pair for each invocation. After the tool execution completes, neither process is terminated. Over a single session, dozens of orphan processes accumulate.

Example (observed data from a single work session):

Copilot Session	Duration	Orphan pwsh	Orphan winpty-agent	Wasted Memory
Session 1 (oldest)	~3 hours	44	44	~3,500 MB
Session 2	~30 min	2	2	~200 MB
Session 3	~20 min	4	4	~300 MB
Total		50	50	~4,000 MB

Each orphan pwsh process consumes ~75 MB of memory and is completely idle (average CPU: 9 seconds total over 3 hours of uptime — only startup initialization).

Impact

• Memory: 50 orphan processes × ~75 MB = ~4 GB wasted RAM
• Process table: 100+ unnecessary processes (pwsh + winpty-agent)
• User confusion: Resource monitoring tools show alarming process counts

Workaround

Manual cleanup of orphan processes by terminating pwsh processes whose parent is a winpty-agent spawned by a copilot process.

Affected version

0.0.406

Steps to reproduce the behavior

1. Start Copilot CLI on Windows (copilot)
2. Execute several prompts that trigger the powershell tool
3. Check process tree: Get-Process -Name pwsh | Select Id, @{N='Parent';E={$_.Parent.Id}}
4. Observe that each tool execution leaves behind a winpty-agent → pwsh pair

Expected behavior

Copilot CLI should terminate winpty-agent and pwsh processes after the associated shell session/tool execution is complete, or at minimum reuse existing shell sessions instead of spawning new ones for each tool call.

Additional context

No response