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Keep children of a TTY-less runner away from the terminal - #27
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🟡 Changes recommended
The central detachment regression test does not exercise detachment on headless CI runners.
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What changed in this PR
Prevents non-TTY runners, particularly MCP operations, from hanging on hidden terminal prompts.
Changes:
- Detaches non-TTY subprocesses into independent Unix sessions.
- Disables Git terminal prompts and removes
GPG_TTY. - Adds documentation and regression tests.
| File | Description |
|---|---|
pkg/exec/runner.go |
Applies non-interactive environment and detachment. |
pkg/exec/runner_test.go |
Tests prompt environment and terminal isolation. |
pkg/exec/detach_unix.go |
Implements Unix session detachment. |
pkg/exec/detach_other.go |
Provides a non-Unix no-op. |
docs/architecture.md |
Documents subprocess terminal isolation. |
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An MCP stack_create in a repo with commit.gpgsign on and an SSH signing key that wasn't loaded into ssh-agent never came back. Capture mode gives git a closed stdin, but ssh-keygen asks for the passphrase on /dev/tty (the controlling terminal), and every child inherits that from whatever terminal the MCP server was started in. So git sat on a prompt nobody could see or answer until someone killed ssh-keygen by hand. gpg's pinentry and git's own credential prompt can do exactly the same. A runner built without a TTY now starts each child in its own session (setsid), so there is no controlling terminal and opening /dev/tty fails; it also sets GIT_TERMINAL_PROMPT=0 and drops GPG_TTY. The prompt turns into an immediate error the tool can return instead of a hang. The CLI runner with a terminal is untouched, so a passphrase prompt in an ordinary git stack create still works as before.
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An MCP
stack_createin a repo withcommit.gpgsignon and an SSH signing key that wasn't loaded into ssh-agent never came back. Capture mode gives git a closed stdin, but ssh-keygen asks for the passphrase on/dev/tty(the controlling terminal), and every child inherits that from whatever terminal the MCP server was started in. So git sat on a prompt nobody could see or answer until someone killed ssh-keygen by hand. gpg's pinentry and git's own credential prompt can do exactly the same.A runner built without a TTY now starts each child in its own session (setsid), so there is no controlling terminal and opening
/dev/ttyfails; it also setsGIT_TERMINAL_PROMPT=0and dropsGPG_TTY. The prompt turns into an immediate error the tool can return instead of a hang. The CLI runner with a terminal is untouched, so a passphrase prompt in an ordinarygit stack createstill works as before.