Claude Haiku 5.5 API Guide: Model ID, Setup and Billing Checks

Use claude-haiku-5-5 for Claude Haiku 5.5. As of October 8, 2026, that exact ID appears in the LLMAPI public model catalogue and on the subscription page. Start by choosing your billing mode, then configure the URL expected by your client.

Anthropic positions Haiku 5.5 for high-volume tasks where latency matters, including classification, extraction and routing. The practical question is whether it handles your own inputs reliably enough for the job. A catalogue entry confirms that a model is listed; your account permissions, remaining quota and an actual request determine whether you can use it at that moment.

Where Haiku 5.5 fits

The official Claude model overview presents Haiku 5.5 alongside Sonnet 5.5, Opus 5.5 and Fable 5.1. For Haiku, begin with focused tasks that have a clear expected result.

These are suggested evaluation tasks, not benchmark results:

Include incomplete and ambiguous examples in your evaluation. Decide in advance when the response should leave a field empty or request human review. Measure answer quality and latency on the same sample before changing a production workflow; vendor positioning does not replace that check.

Keep the model ID and billing mode together

The identifier is claude-haiku-5-5. Do not silently replace it with claude-haiku-4-5-20251001: those are different catalogue entries.

For a subscription, use a subscription key and confirm that your plan is active with quota remaining. The subscription page lists Haiku 5.5 among the included models and explains that listed models share a token-weighted usage quota. Longer contexts can consume more usage units, so a short request and a long conversation should not be treated as equal usage.

For separately billed API use, check the current channel catalogue and select a channel that lists the model. API billing uses a separate key and balance. Do not infer an API channel's price or access from the subscription listing; check the selected channel and your account before calling it.

The official overview is the reference for vendor specifications. Your LLMAPI product selection and account settings determine the service configuration you are actually using. Keeping those two checks separate makes it easier to diagnose a model-selection error without changing unrelated client settings.

Configure the URL your client expects

The API setup tool provides settings by client and checks URL formatting without requiring you to enter a key.

A base URL is the starting point from which a client constructs a request. A complete endpoint already includes the request path. Putting the messages endpoint into a base-URL field can produce the wrong final path.

For Claude Code on macOS or Linux, the documented terminal setup is:

export ANTHROPIC_BASE_URL="https://llmapi.pro"
export ANTHROPIC_AUTH_TOKEN="YOUR_API_KEY"
claude

Replace the placeholder privately with the key for your chosen billing mode. Launch the client from that terminal, then use claude-haiku-5-5 in its model-selection setting. These environment variables configure the connection; they do not select the model by themselves.

For other clients or operating systems, follow the corresponding guide in the documentation. Match the provider type and model field to that client's instructions. The setup tool's URL check runs locally in the browser, so passing it does not validate a key or make an inference request.

Make the first check small

After configuration, send one short task with an easy-to-inspect expected answer. Record the exact model ID, client and billing mode you used. Confirm that the response contains the expected content before moving to a longer prompt or a batch of work.

If the request fails, use the error to choose the next check:

This is a setup and evaluation guide, not a report of a benchmark run. Use your own small request to establish access, then test representative classification, extraction or routing examples before expanding usage.