fix: enforce metadata write deadlines

agent-session-id: dev3.dotfiles-cos-misc-issue-1329-upstream
agent-tool: Codex
agent-tool-version: 0.145.0
agent-model: gpt-5.6-sol
agent-runtime-profile: /nix/store/qlk5xbdfmj5nn1q145j0fx73f2pmdjj7-coding-agent-runtime-profile/share/coding-agents/profile.json
agent-skills-manifest: /nix/store/2km8dbiyv3wc484l1hd8n2lh65121qvq-agent-skills-corpus/share/agent-skills/manifest.json
tooling-profile: dotfiles@unknown-dirty

Author: schickling-assistant

src/run.rs

@@ -87,6 +87,9 @@ fn write_all_before(
         return Err(std::io::Error::last_os_error()).context("make metadata stdin nonblocking");
     }
     while !input.is_empty() {
+        if Instant::now() >= deadline {
+            return Ok(false);
+        }
         match stdin.write(input) {
             Ok(0) => {
                 return Err(std::io::Error::from(std::io::ErrorKind::WriteZero))
@@ -2374,6 +2377,22 @@ mod tests {
         );
     }
 
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn expired_write_deadline_prevents_further_progress() {
+        use std::os::fd::{FromRawFd as _, OwnedFd};
+
+        let mut pipe_fds = [0; 2];
+        assert_eq!(unsafe { libc::pipe2(pipe_fds.as_mut_ptr(), libc::O_CLOEXEC) }, 0);
+        let _reader = unsafe { OwnedFd::from_raw_fd(pipe_fds[0]) };
+        let writer = unsafe { OwnedFd::from_raw_fd(pipe_fds[1]) };
+
+        assert!(
+            !write_all_before(ChildStdin::from(writer), b"x", Instant::now()).unwrap(),
+            "an expired child deadline still allowed stdin progress"
+        );
+    }
+
     #[test]
     fn expired_cleanup_deadline_hands_reaping_off_without_blocking() {
         let child = Command::new("sleep").arg("60").spawn().unwrap();