For the complete documentation index, see llms.txt. Markdown versions of all docs pages are available by appending .md to any docs URL.

Codex

Configure Codex AI coding tool to use agentgateway

Configure Codex, the AI coding tool by OpenAI, to route requests through your agentgateway proxy.

Before you begin

1. Install the agentgateway binary.
2. Install either the Codex CLI or the ChatGPT desktop app.

Configure agentgateway

Start agentgateway with an OpenAI backend configuration. The wildcard * model name accepts any model. Codex sends the model in each request, so you do not need to pin a specific model.

1. Create a configuration file.

   cat > config.yaml << 'EOF'
   # yaml-language-server: $schema=https://agentgateway.dev/schema/config
   llm:
     models:
     - name: "*"
       provider: openAI
       params:
         apiKey: "$OPENAI_API_KEY"
   EOF

2. Start agentgateway.

   agentgateway -f config.yaml

Connect Codex to agentgateway

Codex CLI

Point Codex at agentgateway through one of the following methods.

codex -c 'model_provider="agentgateway"' -c 'model_providers.agentgateway.name="OpenAI via agentgateway"' -c 'model_providers.agentgateway.base_url="http://localhost:4000/v1"'

mkdir -p ~/.codex
cat > ~/.codex/agentgateway.config.toml <<'EOF'
model_provider = "agentgateway"

[model_providers.agentgateway]
name = "OpenAI via agentgateway"
base_url = "http://localhost:4000/v1"
wire_api = "responses"
EOF

codex --profile agentgateway

Verify the CLI connection

1. Send a test prompt through agentgateway. For the profile configuration, include the profile name:

   codex --profile agentgateway "Hello"

2. Verify that the request appears in the agentgateway logs.

   Example output:

   info  request gateway=default/default listener=llm route=internal/model:* endpoint=api.openai.com:443 http.method=POST http.path=/v1/responses http.status=200 protocol=llm gen_ai.operation.name=chat gen_ai.provider.name=openai duration=1687ms

For more configuration options, see the Codex CLI documentation.

Codex in the ChatGPT Desktop App

Codex is available in the ChatGPT desktop app. To use the same provider configuration with the app, back up and replace the user-level configuration, then restart the ChatGPT desktop app:

cp ~/.codex/config.toml ~/.codex/config.toml.bak
cat > ~/.codex/config.toml <<'EOF'
model_provider = "agentgateway"

[model_providers.agentgateway]
name = "OpenAI via agentgateway"
base_url = "http://localhost:4000/v1"
wire_api = "responses"
EOF

To edit the file through the app instead, open Settings > Configuration > Open config.toml and apply the same provider configuration.

Verify the app connection

1. Send a task from Codex in the ChatGPT desktop app.

2. Verify that the request appears in the agentgateway logs.

   Example output:

   info  request gateway=default/default listener=llm route=internal/model:* endpoint=api.openai.com:443 http.method=POST http.path=/v1/responses http.status=200 protocol=llm gen_ai.operation.name=chat gen_ai.provider.name=openai duration=1687ms

For more information, see the Codex app documentation and Codex configuration basics.

Codex also probes /v1/models to discover model metadata. Until agentgateway issue #1462 adds a gateway-generated model list, Codex may warn that model metadata is not found. That warning does not prevent /v1/responses traffic from routing.

Next steps