Codex config

Place the config at ~/.codex/config.toml

model = "gpt-5.2"
model_reasoning_effort = "high"
model_provider = "my_llm_gateway"
 
[model_providers.my_llm_gateway]
name = "My LLM GATEWAY"
base_url = "https://llm.gateway/api/v2"
env_key = "MY_ENV"
wire_api = "responses"
query_params = {}

MCPs

One way of adding MCPs is to put them in the ~/.codex/config.toml

[mcp_servers.context7]
url = "https://mcp.context7.com/mcp"
http_headers = { "CONTEXT7_API_KEY" = "CTX7_KEY" }
 
 
[mcp_servers.perplexity]
command = "npx"
args = ["-y", "perplexity-mcp"]
env = { "PERPLEXITY_API_KEY" = "PPLX_KEY" }

Codex vs Claude Code

A very interesting read at Codex vs. Claude Code (Today)