## What changed
- Add a `TestCodexBuilder` entry point that accepts an explicit `TestEnv`.
- Teach the exec-server test fixture to dispatch filesystem-helper invocations.
- Allow the fixture to receive the Linux sandbox executable through
`CODEX_TEST_LINUX_SANDBOX_EXE` and run the server on a multithreaded Tokio
runtime.
GitOrigin-RevId: cb9c27e9db0363d4022a084bc186ccc749e25a95
## Why
Delegated HTTP requests need to honor the same outbound proxy policy as the
Codex process that starts the exec server.
## What changed
- Pass the configured `HttpClientFactory` through local and remote exec-server
startup and use route-aware client pools for delegated HTTP and local MCP
requests.
- Preserve per-request timeouts and follow-or-stop redirect behavior while
keeping request URLs and sensitive response headers out of diagnostics.
## Testing
- Cover configured system-proxy routing across the exec-server transport.
- Cover both redirect policies and verify that success and failure logs do not
expose request or response secrets.
GitOrigin-RevId: 4af6aec1d265c4db62dfcb6e1fb076fb31736137
## Why
Sandbox wrappers replaced the process launch command and did not carry an
`ExecParams.arg0` override through to the inner process.
## What changed
- Route sandboxed Unix launches with a custom `arg0` through a helper mode that
re-execs the requested program with the override.
- Expose the helper executable to the filesystem sandbox and dispatch its mode
from Codex and exec-server test binaries.
## Testing
Add coverage for the prepared sandbox command and an end-to-end remote process
that verifies both the custom `arg0` and filesystem restrictions.
GitOrigin-RevId: c9f8eef3906d184e670184c2eeed250d5895a9ca
