terminal-tools — foundations

These tools give you a real terminal: foreground exec with smart envelopes, background jobs with offset-based log streaming, persistent PTY shells, and filesystem search. Bash-only on POSIX.

Tool preference (read first)

Before reaching for terminal-tools, check whether a higher-level tool already covers the task. Shell is for system operations the other servers don't reach.

• Reading files → files-tools.read_file (handles size, paging, line-numbered output) — NOT terminal_exec("cat ...")
• Editing files → files-tools.edit_file (atomic patch with diff verification) — NOT terminal_exec("sed -i ...")
• Writing files → files-tools.write_file — NOT terminal_exec("echo > ...")
• In-project search → files-tools.search_files (project-scoped, code-aware) — use terminal_rg only for raw paths outside the project (/var/log, /etc)
• Browser / web pages → gcu-tools.browser_* for rendered pages — NOT terminal_exec("curl ...")
• Web search → hive_tools.web_search — NOT scraping
• System operations (process exec, jobs, PTYs, raw fs search) → terminal-tools. This is its territory.

The standard envelope

Every spawn-style call (terminal_exec, the auto-promoted job state) returns this shape:

{
  "exit_code": 0,                    // null when auto-backgrounded or pre-spawn error
  "stdout": "...",                   // decoded, truncated to max_output_kb (default 256 KB)
  "stderr": "...",
  "stdout_truncated_bytes": 0,       // > 0 means more is in output_handle
  "stderr_truncated_bytes": 0,
  "runtime_ms": 42,
  "pid": 12345,
  "output_handle": null,             // "out_<hex>" when truncated — paginate with terminal_output_get
  "timed_out": false,
  "semantic_status": "ok",           // "ok" | "signal" | "error" — read THIS, not just exit_code
  "semantic_message": null,          // e.g. "No matches found" for grep exit 1
  "warning": null,                   // e.g. "may force-remove files" for rm -rf
  "auto_backgrounded": false,
  "job_id": null                     // set when auto_backgrounded=true
}

Auto-promotion (the core mental model)

terminal_exec runs commands in the foreground until the auto-background budget (default 30s) elapses. Past that point, the process is silently transferred to a background job and the call returns immediately with:

{ "auto_backgrounded": true, "exit_code": null, "job_id": "job_<hex>", ... }

When you see auto_backgrounded: true, pivot to polling. The job is still running:

terminal_job_logs(job_id, since_offset=0, wait_until_exit=true, wait_timeout_sec=60)
  → blocks server-side until the job exits or the timeout, returns logs + status

You're not failing — you're freed up to do other work while the long task runs.

To force pure-foreground (kill on timeout_sec), pass auto_background_after_sec=0. Use this when you genuinely don't want a background job (small commands where promotion would surprise you).

Semantic exit codes — read semantic_status, not raw exit_code

Several common commands use exit 1 for legitimate non-error states:

For these, semantic_status will be "ok" even when exit_code == 1, with semantic_message describing why ("No matches found"). For everything else, semantic_status defaults to "ok" on 0 and "error" on nonzero.

Rule: always check semantic_status first. Only fall back to exit_code when you need the exact number (e.g. distinguishing make errors).

Destructive warnings — re-read your command

The envelope's warning field is set when the command matches a known destructive pattern (rm -rf, git push --force, git reset --hard, DROP TABLE, kubectl delete, terraform destroy, etc.). The command still ran — the warning is informational. Use it as a "did I mean to do that?" prompt before trusting subsequent steps that depend on the side effect.

If a warning appears unexpectedly, stop and verify: was the destructive action intended, or did a path/glob slip in?

Output handles — never lose output

When stdout_truncated_bytes > 0 or stderr_truncated_bytes > 0, the inline output was capped at max_output_kb (default 256 KB). The full bytes are stashed under output_handle for 5 minutes. Paginate with:

terminal_output_get(output_handle, since_offset=0, max_kb=64)
  → { data, offset, next_offset, eof, expired }

Track next_offset across calls. If expired: true, re-run the command (the handle's TTL has lapsed).

The store has a 64 MB cap with LRU eviction. For huge outputs, prefer terminal_job_start + terminal_job_logs polling (4 MB ring buffer per stream, infinite total throughput).

Bash, not zsh — even on macOS

terminal_exec and terminal_pty_open always invoke /bin/bash. The user's $SHELL is ignored. Explicit shell="/bin/zsh" is rejected with a clear error. This is a deliberate security stance, not aesthetic — zsh has command/builtin classes (zmodload, =cmd expansion, zpty, ztcp, zf_*) that bypass bash-shaped checks. The terminal-tools-pty-sessions skill explains the implications for PTY sessions specifically.

ZDOTDIR and ZSH_* env vars are stripped before exec to prevent zsh dotfiles leaking in. Bash dotfiles still apply when invoked interactively (e.g. PTY sessions use bash --norc --noprofile to keep things predictable).

Pipelines and complex commands

Pipes (|), redirects (>, <, >>), conditionals (&&, ||, ;), and globs (*, ?, [) are detected automatically. You can pass them with the default shell=False and the runtime will transparently route through /bin/bash -c and surface auto_shell: true in the envelope:

terminal_exec("ps aux | sort -k3 -rn | head -40")
  → { exit_code: 0, stdout: "...", auto_shell: true, ... }

For simple argv commands (no metacharacters) shell=False is faster and direct-execs the binary. For commands with shell features but no metacharacters that the detector catches (rare — exotic bash builtins, here-strings), pass shell=True explicitly:

terminal_exec("set -e; complicated bash logic", shell=True)

Quoted strings work either way — the detector uses shlex.split which handles "quoted args with spaces" correctly.

When to use what (cheat sheet)

See references/exit_codes.md for the full POSIX + signal-induced + semantic catalog.