Reasonix Integration

Reasonix is an open-source coding agent with a terminal interface, desktop app, and editor integration. Its current release supports OpenAI-compatible endpoints, so you can connect it directly to Halfbill.

Install

Install the current native CLI:

pnpm add -g reasonix
reasonix --version

See the installation instructions for other platforms and installation methods. These instructions apply to Reasonix 1.x; the older 0.x release uses a different configuration format.

Connect to Halfbill

Run the provider setup:

reasonix setup

Add an OpenAI-compatible provider with these values:

Choose Save and exit, then select this provider as your default.

Reasonix stores provider definitions in ~/.reasonix/config.toml on macOS and Linux, or %AppData%\reasonix\config.toml on Windows. A minimal configuration looks like this:

default_model = "halfbill"

[[providers]]
name = "halfbill"
kind = "openai"
base_url = "https://api.halfbill.uk/v1"
model = "claude-sonnet-5"
api_key_env = "HALFBILL_API_KEY"
headers = { x-source = "reasonix" }

Copy your preferred model ID from the catalogue.

Save the key through reasonix setup. The api_key_env field names the entry in Reasonix's own .env file. Current Reasonix reads provider secrets from that file inside its configuration directory; exporting a shell variable alone does not configure the key.

Using Halfbill Code? A Halfbill Code plan key works the same way; use the canonical model ID.

Try a coding task

Start Reasonix from your project directory:

cd your-project
reasonix

Ask it to fix a specific problem and verify the result:

Fix slugify.ts so all tests pass. Read the files, make the smallest fix,
run node --test slugify.test.ts, and summarize. Do not edit the tests.

Reasonix can read files, propose edits, and execute tests. Review any permission prompts before allowing commands. For a one-shot task, use reasonix run "your task".

Check the request's model, tokens, and cost in your Halfbill dashboard.

Troubleshooting

Missing key or authentication error

Open reasonix setup and save your Halfbill key for the configured provider. Check that api_key_env matches the entry in Reasonix's own .env file. Keep that file out of your project repository.

Model not found

Copy the exact ID from the models page. In Reasonix, --model halfbill selects the configured provider; the provider's model field selects the Halfbill model.

Requests go to another provider

Set default_model = "halfbill", or launch with reasonix --model halfbill. Check for a project-level reasonix.toml, which can override your user configuration.

Connection errors

Use kind = "openai" and include /v1 in the base URL. For configuration and diagnostic commands, see the Reasonix guide.