feat: experimental Windows backend (pywinpty) (v0.3.0)

[mabry1985]

Follow-up B (Windows). pty_session.py gains a WinPtySession (winpty.PtyProcess) alongside the POSIX PtySession, selected by open_session() on sys.platform. The Unix-only imports (pty/fcntl/termios) are guarded so the module imports on Windows. api._bridge uses open_session. pywinpty is declared in requires_pip (sys_platform=='win32') — not auto-installed.

EXPERIMENTAL — untested in our Linux CI; the POSIX path stays the supported, tested one. A Windows user needs to validate. Tests cover: open_session picks POSIX here, WinPtySession._build_env (TERM + scrub), and its clear PtyError when pywinpty is absent. 19 tests green.

[protoquinn]

👀 Quinn is reviewing — verdict (PASS / WARN / FAIL) + findings to follow.

[protoquinn]

QA Audit — PR #3 | feat: experimental Windows backend (pywinpty) (v0.3.0)

VERDICT: WARN (non-terminal — CI test still in_progress)

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CI Status

• test: in_progress ⏳

Diff Review

• Adds WinPtySession (pywinpty backend) alongside POSIX PtySession, selected by open_session() factory on sys.platform — clean abstraction (pty_session.py:197+, api.py:109).
• Unix imports (pty/fcntl/termios) guarded with if sys.platform != "win32" — module imports on Windows (pty_session.py:11-14).
• Manifest declares pywinpty>=2.0; sys_platform=='win32' in requires_pip, NOT auto-installed — experimental posture is clear (protoagent.plugin.yaml:16-18).
• Docs updated: README, roadmap, file table — consistent messaging (README.md).

Observations

• LOW: WinPtySession.write() silently swallows all exceptions (pty_session.py ~line 265). If the PTY process has died, the caller never knows. The read() path already treats failures as EOF, which is reasonable; consider at least logging write failures.
• LOW: clawpatch structural review unavailable for this repo — review is diff-based only.
• GAP: diff truncated at 200/295 lines. open_session(), resize(), poll(), aclose() are not visible in the fetched diff. Tests (19 green per PR description) cover open_session platform selection and _build_env — these give confidence, but the unseen methods should be spot-checked by a human.
• No unresolved CodeRabbit threads.

The architecture is sound: factory pattern, guarded imports, clear experimental labeling. The POSIX path is untouched. Mergeable once CI is terminal-green.

— Quinn, QA Engineer

[protoquinn]

Submitted COMMENT review on #3.