## Summary
This is PR 2 of the Windows sandbox runner split.
PR 1 introduced the framed IPC runner foundation and related Windows
sandbox infrastructure without changing the active elevated one-shot
execution path. This PR switches that elevated one-shot path over to the
new runner IPC transport and removes the old request-file bootstrap that
PR 1 intentionally left in place.
After this change, ordinary elevated Windows sandbox commands still
behave as one-shot executions, but they now run as the simple case of
the same helper/IPC transport that later unified_exec work will build
on.
## Why this is needed for unified_exec
Windows elevated sandboxed execution crosses a user boundary: the CLI
launches a helper as the sandbox user and has to manage command
execution from outside that security context. For one-shot commands, the
old request-file/bootstrap flow was sufficient. For unified_exec, it is
not.
Unified_exec needs a long-lived bidirectional channel so the parent can:
- send a spawn request
- receive structured spawn success/failure
- stream stdout and stderr incrementally
- eventually support stdin writes, termination, and other session
lifecycle events
This PR does not add long-lived sessions yet. It converts the existing
elevated one-shot path to use the same framed IPC transport so that PR 3
can add unified_exec session semantics on top of a transport that is
already exercised by normal elevated command execution.
## Scope
This PR:
- updates `windows-sandbox-rs/src/elevated_impl.rs` to launch the runner
with named pipes, send a framed `SpawnRequest`, wait for `SpawnReady`,
and collect framed `Output`/`Exit` messages
- removes the old `--request-file=...` execution path from
`windows-sandbox-rs/src/elevated/command_runner_win.rs`
- keeps the public behavior one-shot: no session reuse or interactive
unified_exec behavior is introduced here
This PR does not:
- add Windows unified_exec session support
- add background terminal reuse
- add PTY session lifecycle management
## Why Windows needs this and Linux/macOS do not
On Linux and macOS, the existing sandbox/process model composes much
more directly with long-lived process control. The parent can generally
spawn and own the child process (or PTY) directly inside the sandbox
model we already use.
Windows elevated sandboxing is different. The parent is not directly
managing the sandboxed process in the same way; it launches across a
different user/security context. That means long-lived control requires
an explicit helper process plus IPC for spawn, output, exit, and later
stdin/session control.
So the extra machinery here is not because unified_exec is conceptually
different on Windows. It is because the elevated Windows sandbox
boundary requires a helper-mediated transport to support it cleanly.
## Validation
- `cargo test -p codex-windows-sandbox`
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