Use native Codex steering and transcript deletion

server/src/session/process.rs

@@ -187,6 +187,39 @@ pub fn clear(session_dir: &Path) {
     }
 }
 
+/// Creates a session stdin fifo and opens it read-write for the child.
+///
+/// The child holding the write end is what keeps a detached JSON server from
+/// reading EOF when ai-server restarts and temporarily closes its own writer.
+pub fn make_fifo(path: &Path) -> Result<std::fs::File> {
+    if !path.exists() {
+        let c_path = std::ffi::CString::new(path.as_os_str().as_encoded_bytes())
+            .with_context(|| format!("{} is not a usable path", path.display()))?;
+        // SAFETY: `c_path` is nul-terminated and this call only reads it.
+        let made = unsafe { libc::mkfifo(c_path.as_ptr(), 0o600) };
+        if made != 0 {
+            return Err(std::io::Error::last_os_error())
+                .with_context(|| format!("creating the fifo {}", path.display()));
+        }
+    }
+    std::fs::OpenOptions::new()
+        .read(true)
+        .write(true)
+        .open(path)
+        .with_context(|| format!("opening the fifo {}", path.display()))
+}
+
+/// A fresh owner-only log for a detached session process.
+pub fn create_log(path: &Path) -> Result<std::fs::File> {
+    std::fs::OpenOptions::new()
+        .create(true)
+        .write(true)
+        .truncate(true)
+        .mode(0o600)
+        .open(path)
+        .with_context(|| format!("creating {}", path.display()))
+}
+
 /// Grace period between asking a session's process to stop and killing it.
 /// Here rather than beside each caller: two drivers plus the manager had
 /// written the same five seconds down separately.