AI/agent terminal sessions pollute PSReadLine history #5123

Summary

When AI agents (e.g., GitHub Copilot, VS Code terminal agents) execute commands in PowerShell terminals, those commands are saved to PSReadLine history indistinguishably from user-typed commands. This pollutes history recall with commands the user never typed, inflates frequency counts, and degrades the usefulness of history recall.

Problem

AI coding assistants routinely run commands like Get-ChildItem, dotnet build, git status, etc. in integrated terminals. These get recorded to PSReadLine history (both text file and SQLite modes) as if the user typed them. Over time this means:

• History recall is noisy — Up arrow surfaces agent commands the user didn't type
• Frequency-based ranking is skewed — location-aware recall ranks agent-repeated commands higher than user favorites
• HistoryNoDuplicates doesn't help — the commands are real commands, just not user-initiated

Current Workaround

Users can add this to their $PROFILE:

# Requires the agent to set this env var before launching pwsh
if ($env:PSREADLINE_HISTORY_SAVE -eq '0') {
    Set-PSReadLineOption -AddToHistoryHandler { [Microsoft.PowerShell.AddToHistoryOption]::MemoryOnly }
}

But this is fragile because:

1. The agent must set the env var — requires cooperation from VS Code / Copilot
2. Agents that use pwsh -NoProfile bypass the check entirely
3. Users must manually add the snippet

Proposal

Add a built-in environment variable check in PSReadLine's initialization, so that agent-spawned terminals can opt out of persistent history without requiring profile configuration:

// During PSReadLine init, before any history writes
if (Environment.GetEnvironmentVariable("PSREADLINE_HISTORY_SAVE") == "0")
{
    Options.AddToHistoryHandler = _ => AddToHistoryOption.MemoryOnly;
}

This way:

• Any agent framework just sets PSREADLINE_HISTORY_SAVE=0 as a process environment variable before launching pwsh
• Works regardless of -NoProfile
• No user configuration needed
• Commands still available in the current session's memory (Up arrow works), just not persisted to disk

Environment

• VS Code with GitHub Copilot agent terminals