## Summary
Add explicit, model-visible network policy decision metadata to blocked
proxy responses/errors.
Introduces a standardized prefix line: `CODEX_NETWORK_POLICY_DECISION
{json}`
and wires it through blocked paths for:
- HTTP requests
- HTTPS CONNECT
- SOCKS5 TCP/UDP denials
## Why
The model should see *why* a request was blocked
(reason/source/protocol/host/port) so it can choose the correct next
action.
## Notes
- This PR is intentionally independent of config-layering/network-rule
runtime integration.
- Focus is blocked decision surface only.
This add a new crate, `codex-network-proxy`, a local network proxy
service used by Codex to enforce fine-grained network policy (domain
allow/deny) and to surface blocked network events for interactive
approvals.
- New crate: `codex-rs/network-proxy/` (`codex-network-proxy` binary +
library)
- Core capabilities:
- HTTP proxy support (including CONNECT tunneling)
- SOCKS5 proxy support (in the later PR)
- policy evaluation (allowed/denied domain lists; denylist wins;
wildcard support)
- small admin API for polling/reload/mode changes
- optional MITM support for HTTPS CONNECT to enforce “limited mode”
method restrictions (later PR)
Will follow up integration with codex in subsequent PRs.
## Testing
- `cd codex-rs && cargo build -p codex-network-proxy`
- `cd codex-rs && cargo run -p codex-network-proxy -- proxy`
