fx - Phaseo Docs

fx is an open-source coding agent from Vercel Labs. It can call any OpenAI-compatible Chat Completions endpoint through a named custom connection, so Phaseo works as its model gateway. fx runs on macOS and Linux.

1) Configure fx

Use the Phaseo CLI to add the connection, sync compatible Phaseo models, and make Phaseo fx’s active provider:

phaseo login
phaseo fx --model openai/gpt-5.6-terra

When fx is missing in an interactive terminal, Phaseo shows the official installer command and asks before running it. The command then:

adds a phaseo connection to ~/.fx/settings.json, preserving your other settings and connections;
syncs up to 256 compatible Phaseo models, the most fx accepts, with their context and output limits;
sets phaseo as the active fx provider and records the previous provider so removal can restore it;
creates a Phaseo CLI: fx API Key, which expires after 90 days and has a $100 monthly spend limit, and stores it in the owner-only file ~/.config/phaseo/integrations/fx.env. Run phaseo fx again to replace an expired key.

Use --catalog default to configure only the selected model, or --dry-run to preview the file changes.

2) Load the key in your shell

fx reads custom-connection keys only from environment variables, never from its settings file. Add this line to ~/.zshrc or ~/.bashrc once, then open a new terminal:

[ -f "$HOME/.config/phaseo/integrations/fx.env" ] && . "$HOME/.config/phaseo/integrations/fx.env"

The line sets PHASEO_FX_API_KEY when the file exists and does nothing after you remove the integration.

3) Start fx

fx

Switch models with /model, or pick any Phaseo model ID for a single run with FX_MODEL=<id> fx. Switch back to another provider with fx provider <name>.

Manual configuration

Add the connection to ~/.fx/settings.json. fx does not accept custom connections in a project .fx.json.

{
  "provider": "phaseo",
  "providers": {
    "phaseo": {
      "protocol": "openai-chat-completions",
      "base_url": "https://api.phaseo.app/v1",
      "auth": { "type": "bearer", "env": "PHASEO_API_KEY" },
      "model_metadata": {
        "openai/gpt-5.6-terra": { "context_window": 400000, "max_output_tokens": 128000 }
      }
    }
  },
  "models": { "phaseo": "openai/gpt-5.6-terra" }
}

Then export PHASEO_API_KEY and run fx. Without a context_window, fx cannot work out when to compact the conversation, so declare limits for the models you use. The limits above are examples; take real values from the Models endpoint.

Remove

phaseo integrations remove fx

This removes the phaseo connection and model, restores your previous fx provider if Phaseo is still active, deletes the key file, and revokes the key.

Verification

Run fx status --json to confirm the active provider, endpoint, and model.
Run a small prompt such as fx ask "Summarize README.md" before file-editing work.
If fx reports a missing credential, open a new terminal or check that the shell-profile line is present.
AI Gateway-only fx features, such as gateway web search and credit checks, are not available through custom connections.

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fx

1) Configure fx

2) Load the key in your shell

3) Start fx

Manual configuration

Remove

Verification

​1) Configure fx

​2) Load the key in your shell

​3) Start fx

​Manual configuration

​Remove

​Verification

1) Configure fx

2) Load the key in your shell

3) Start fx

Manual configuration

Remove

Verification