Codex Network Proxy Quickstart (Local)

This is a compact guide to build and validate the Codex network proxy locally.

Build

From the Codex repo:

cd /Users/viyatb/code/codex/codex-rs
cargo build -p codex-network-proxy

For MITM support:

cargo build -p codex-network-proxy --features mitm

Configure

Add this to ~/.codex/config.toml:

[network_proxy]
enabled = true
proxy_url = "http://127.0.0.1:3128"
admin_url = "http://127.0.0.1:8080"
mode = "limited" # or "full"
prompt_on_block = true
poll_interval_ms = 1000

[network_proxy.policy]
allowedDomains = ["example.com", "*.github.com"]
deniedDomains = ["metadata.google.internal", "169.254.*"]

[network_proxy.mitm]
enabled = false

Run the proxy

cd /Users/viyatb/code/codex/codex-rs
cargo run -p codex-network-proxy -- proxy

With MITM:

cargo run -p codex-network-proxy --features mitm -- proxy

Test with curl

HTTP/HTTPS via proxy:

export HTTP_PROXY="http://127.0.0.1:3128"
export HTTPS_PROXY="http://127.0.0.1:3128"
curl -sS https://example.com

Limited mode + HTTPS requires MITM. If MITM is on, trust the generated CA:

security add-trusted-cert -d -r trustRoot \
  -k ~/Library/Keychains/login.keychain-db \
  ~/.codex/network_proxy/mitm/ca.pem

Or pass the CA directly:

curl --cacert ~/.codex/network_proxy/mitm/ca.pem -sS https://example.com

Admin endpoints

Reload config after edits:

curl -fsS -X POST http://127.0.0.1:8080/reload

Switch modes:

curl -fsS -X POST http://127.0.0.1:8080/mode -d '{"mode":"full"}'

Codex integration sanity check

Start the proxy.
Launch Codex with the proxy enabled in config.
Run a network command (e.g., curl https://example.com).
Confirm you see the allow/deny prompt and that the proxy logs reflect the decision.

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