terminal-command-safety

name	terminal-command-safety
description	Provides terminal output-capture, hung-command, and platform-behavior procedures while the resident instruction retains the Backtick Hazard floor. Use when a command may lose output, hang, need interaction, or depend on host execution behavior.
lastReviewed	2026-08-18T00:00:00.000Z

Terminal Command Safety

The always-on instruction retains the Backtick Hazard and its temp-file rule. Use this skill after that floor is satisfied when execution needs a procedure for output capture, hang prevention, or host behavior.

Output Capture Failures

Terminal output can be silently lost or truncated.

1. Redirect to file, then read: cmd 2>&1 | Out-File $env:TEMP\out.txt
2. Pipe pagers through Out-String
3. Sentinel: ; echo "EXIT_CODE:$LASTEXITCODE"
4. Limit volume: Select-Object -First, -Tail, Format-Table
5. Avoid alt-buffer programs (less, vim, man) — use non-interactive equivalents
6. If empty: retry with get_terminal_output, then redirect to file, then check stderr

Terminal Hanging

1. Use mode=async for commands over 15 seconds, including servers, builds, and test suites. VS Code 1.121+ may auto-promote a quiet synchronous command to the background; this remains the required agent intent and covers older hosts.
2. Never run interactive commands. Pre-answer with flags such as --yes or --no-edit.
3. Set network timeouts such as --max-time or --prefer-offline.
4. Avoid heredoc blocks because they can desynchronize the terminal parser.
5. Run one command at a time. Do not chain unrelated commands.
6. Stop a stuck command with send_to_terminal and Ctrl+C, or start a fresh terminal.

VS Code Platform Changes

Recent VS Code agentic-execution improvements reduce the need for some manual patterns above. The file-redirect fallback remains the safe default when full, unfiltered output matters.

Surface	Behavior change	When the manual pattern still wins
1.117	Terminal output is auto-included after send_to_terminal; async-completion notifications fire automatically.	Exact byte-for-byte diagnostic output is needed.
1.118	Agentic execution pre-filters terminal output.	Exact error strings, full test results, or encoding-sensitive output are needed.
1.120-1.121	chat.tools.compressOutput.enabled post-processes long output; one-shot async terminals auto-dispose.	Raw lockfile diffs, install logs, or output that compression strips is needed.
1.127	macOS/Linux terminal commands are sandboxed by default.	Windows remains unchanged, so the resident Backtick Hazard still applies.

Boundaries

• Do not weaken, duplicate, or bypass the resident Backtick Hazard floor.
• Do not send secrets through a terminal command or tool input.
• Do not treat a missing output line as proof that a command succeeded.

Anti-Patterns

Anti-pattern	Correction
Relying on compressed output for a precise diagnosis	Redirect to a temporary file and inspect it.
Starting a long-running command synchronously	Use asynchronous execution when it must outlive the current response.
Retrying an interactive command unchanged	Find and provide its noninteractive flags.

Would Revise If

Revisit by 2026-11-18 if the deferred procedure fails to load when a terminal command needs it, host behavior makes the version table inaccurate, or a terminal failure reaches the user because the resident Backtick Hazard alone was insufficient.