## Why
Private IP destinations always bypassed inherited upstream proxies, preventing their use for private networks reachable through an upstream VPN proxy.
## What changed
- Add `codex exec-server --proxy-private-ips-via-upstream`, also configurable with `CODEX_EXEC_SERVER_PROXY_PRIVATE_IPS_VIA_UPSTREAM=true`. The setting defaults to disabled.
- Allow permitted RFC 1918, carrier-grade NAT, and IPv6 unique-local destinations to use an applicable upstream proxy. Loopback and link-local destinations retain direct routing, and destination access policy still applies.
- Keep connections direct when no valid upstream proxy applies or `allow_upstream_proxy=false`. Errors after selecting an upstream proxy do not trigger a direct retry.
- Rename `ExecServerRuntimePaths` to `ExecServerRuntimeOptions` and carry the routing setting from executor startup into the managed network proxy.
## Testing
Add routing coverage for private address ranges, special-use addresses, and public targets with the option enabled and disabled. Verify that HTTP and CONNECT requests still enforce destination allowlists and denylists, and update the CLI help snapshot.
GitOrigin-RevId: b7c9cc7da0e0f545694a6521b74c9b36b7b92769
## Why
Linux pipe launches need session, parent-death signal, and descriptor setup. Move this work into a fresh, single-threaded executable image to avoid forking the app-server for child setup.
## What changed
- Register an early setup helper and launch it through `posix_spawn` for Linux pipe processes.
- Start the helper with an empty environment, then transfer the target environment over a control socket so loader settings cannot interfere with helper startup.
- Await target execution asynchronously, propagate setup and execution errors, and kill incomplete launches on cancellation.
- Preserve direct spawning as a fallback when the helper is unavailable or fails before target execution.
## Testing
Add coverage for launch semantics, avoiding fork, loader environment isolation, early argument dispatch, closed standard descriptors, and fallback under bootstrap failure or descriptor pressure. Add an app-server regression test that reuses a process handle after an execution failure.
GitOrigin-RevId: 079c673f0f22ebd531f8c57e5338095cc98acfdc
## 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
open-matt