Codex

Codex is the terminal agent from OpenAI. It uses the OpenAI Responses API. Add the exchange as a provider in a Codex profile, and start Codex with that profile.

The quickest way is the Liquid CLI. Use the manual steps only when you must keep the settings in your own files.

Start with the Liquid CLI

The Liquid CLI starts Codex with the exchange as its provider. It sets the base URL, the key and the model for that process only. It writes no file of yours.

curl -fsSL https://inference.ai.exchange/cli/install.sh | bash
liquid login
liquid codex

Before you start

• A workspace with a balance and a spend key. See API keys.
• Codex 0.95 or later. Codex speaks the Responses API only from 0.95. Run codex --version after you install:

npm install -g @openai/codex@latest

1. Create the profile

A Codex profile is the file ~/.codex/<name>.config.toml. With --profile <name>, Codex applies it on top of ~/.codex/config.toml.

• The first block writes the profile.
• The second block has the same settings for ~/.codex/config.toml. The VS Code extension uses that file without --profile.

Profile

cat > ~/.codex/liquid.config.toml <<'EOF'
model = "liquid.auto"
model_provider = "liquid"
web_search = "disabled"
suppress_unstable_features_warning = true

[features]
api_key_model_discovery = true

[model_providers.liquid]
name = "Liquid Inference"
base_url = "https://router.inference.ai.exchange/v1"
env_key = "LIQUID_API_KEY"
env_key_instructions = "Create a key at https://inference.ai.exchange/keys"
model_catalog_url = "https://router.inference.ai.exchange/v1/codex/models"
EOF

Make it the default

# Above the first [section] of ~/.codex/config.toml
model = "liquid.auto"
model_provider = "liquid"
web_search = "disabled"
suppress_unstable_features_warning = true

# Anywhere after it
[features]
api_key_model_discovery = true

[model_providers.liquid]
name = "Liquid Inference"
base_url = "https://router.inference.ai.exchange/v1"
env_key = "LIQUID_API_KEY"
env_key_instructions = "Create a key at https://inference.ai.exchange/keys"
model_catalog_url = "https://router.inference.ai.exchange/v1/codex/models"

Do not add wire_api. Codex 0.95 removed wire_api = "chat".

In ~/.codex/config.toml, TOML puts each key after a [section] header into that section. So:

• Put the top-level lines above the first [section] header.
• If the file has a [features] table, add the line to that table. TOML does not allow the same table twice.

2. Export the key

Set the key in the shell that starts Codex. To keep it, add the line to ~/.zshrc or ~/.bashrc.

export LIQUID_API_KEY=sk-liquid-...

3. Run it

export LIQUID_API_KEY=sk-liquid-...
codex --profile liquid

4. Check it works

Send one request without the interactive session:

codex exec --profile liquid "Reply with the word ready"

Codex prints the answer. The request shows under Receipts on the Credits page, with Codex as the client. See Quickstart.

Choosing a model

In Codex, /model lists these models, in this order:

1. liquid.auto, then the other router models.
2. The presets of your workspace.
3. Exact models whose offers accept tools, with the most offers first. Codex sends tools on each turn.

If the offers accept a reasoning effort, /model also shows low, medium and high. Codex keeps the list for 5 minutes.

To choose a model for one session, pass --model:

codex --profile liquid --model gpt-oss-120b

A model on the book but not in the list still works. Codex then shows Model metadata for `<model>` not found, uses a context window of 272,000 tokens and omits apply_patch.

The exchange refuses a name that is not on the book. For current names, use GET /v1/models. See Market data.

The cap

liquid.auto has a cap of its own, so Codex needs to send nothing. To set your own cap, add a header to the [model_providers.liquid] table, because Codex cannot send the exchange block:

http_headers = { "x-liquid-cap-usd" = "1.00" }

This sets a cap of $1 on each request, for all models. See Auto Router.

Purchasing rules

Codex sends the http_headers of the provider with each request:

[model_providers.liquid]
# ...the settings from step 1...
http_headers = { "x-liquid-cap-usd" = "0.50", "x-liquid-ttft-ms" = "3000", "x-liquid-policy" = "economy" }

• If the worst-case charge is more than the cap, the exchange refuses the request. It does not shrink the request, except an output limit that it chose (see Output length).
• A header that the exchange cannot parse gets 400 invalid_header.
• No header sets the models. Save them in a preset, and set model to the preset name. See Purchasing rules.

Output length

Codex sends no output limit. The exchange uses 32,768 tokens.

• It lowers the limit to the largest limit of the offers that can take the request.
• If your balance or cap is too small, it halves the limit until an offer fits, down to 1,024 tokens. It never changes a limit that the client set. See Errors.

An answer that reaches the limit ends with max_output_tokens. Codex shows Incomplete response returned and sends the request again. The exchange charges again. If this repeats, choose a model that allows longer answers, or raise the cap.

What isn't supported

• Hosted tools. The exchange removes web_search and runs no search. To search, add :web (beta) to the model name. It refuses file_search, code_interpreter and image_generation with 400 unsupported_parameter. Function tools, MCP tools and apply_patch work.
• Stored responses. The exchange refuses previous_response_id, conversation and background: true, and ignores store. Codex sends the full conversation each time, so this does not affect it.

Control the cost

The exchange sets a cap on each request before the first token. To limit total spend, set a spending limit on the Codex key. When the context window fills, Codex asks for a summary, and the exchange charges for it like any request. See API keys.

Troubleshooting

Codex tries a 401, 402, 404 or 503 response five times (Reconnecting... 1/5). It shows a 400 response at once.