[waldekmastykarz]

devproxy --detach hung callers that capture its output (devproxy --detach 2>&1 | Out-String, $(devproxy --detach), subprocess/execSync with pipes).

Cause

On Windows, Process.Start calls CreateProcess with bInheritHandles = TRUE, so the daemon inherits every inheritable handle of the devproxy --detach parent, not just the redirected pipes assigned as its stdio. The stdout/stderr handles the caller passes in are inheritable, so the long-running daemon kept the caller's pipe open and the caller never saw EOF.

On Unix, fork/exec replaces fds 0–2 with the redirected pipes, so the caller's pipe isn't held (verified on macOS: out=$(devproxy --detach ... | cat) returns in ~1s).

Changes

• Before spawning the daemon, clear HANDLE_FLAG_INHERIT on the parent's std handles (StandardHandleInheritance, Windows-only, no-op elsewhere). The parent keeps using them; only inheritance is affected.
• Redirect the daemon's stdin too (and close it right away), so the daemon holds none of the caller's stdio. The daemon doesn't read stdin (hotkeys are already disabled for --_internal-daemon).
• Kept stdout/stderr redirected to pipes (rather than null) so early-startup failures are still reported by the parent.
• Added Detach_WithCapturedOutput_ParentOutputReachesEofWhileDaemonKeepsRunning (text + json): runs devproxy --detach with captured pipes, requires EOF within 15s of the parent exiting, and checks the daemon is still running.

Testing

• ProcessSmokeTests pass on macOS (11/11).
• Not run on Windows locally (CI is Linux-only); the new test is the regression guard there.

Closes #2080

[Copilot]

🟡 Changes recommended

The EOF-timeout assertion can fail before the daemon PID is captured, causing cleanup to leave the detached daemon running after the failed test.

1 open issue

• Ensure daemon is stopped when EOF timeout assertion fails · New

What changed in this PR

Fixes detached startup hanging callers that capture output by preventing the daemon from retaining the caller’s standard I/O handles.

Changes:

• Disables inheritance of the launcher’s standard handles on Windows.
• Redirects and closes daemon stdin while preserving stdout/stderr capture for startup errors.
• Adds text and JSON regression tests requiring captured output to reach EOF while the daemon remains running.

File	Description
DevProxy/​Proxy/​StandardHandleInheritance.cs	Adds Windows-only standard-handle inheritance control.
DevProxy/​Program.cs	Applies inheritance control and redirects daemon stdin.
DevProxy.Integration.Tests/​ProcessSmokeTests.cs	Tests captured-output EOF and continued daemon operation.

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

Reported checks cover only macOS tests and Linux builds, leaving Windows captured-output EOF—including merged stdout/stderr while the daemon remains alive—and early-startup error reporting unverified.

No open issues 🎉

1 resolved since last review

• Ensure daemon is stopped when EOF timeout assertion fails

_{Review effort: Balanced}