> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fortapi.com/llms.txt
> Use this file to discover all available pages before exploring further.

# FAQ

> Quick answers on auth, base_url, models, billing, and errors

<AccordionGroup>
  <Accordion title="Should base_url include /v1?">
    Depends on the protocol:

    * **OpenAI protocol**: include `/v1` — `https://www.fortapi.com/v1`.
    * **Anthropic SDK**: `ANTHROPIC_BASE_URL` does **not** include `/v1` — `https://www.fortapi.com`. The SDK appends `/v1/messages` itself; adding `/v1` causes a 404.
  </Accordion>

  <Accordion title="Getting 401 / auth failed?">
    * You must use a **FortAPI** token (`sk-...`), not an OpenAI / Anthropic key.
    * Check for stray whitespace or line breaks.
    * In the console under **Tokens**, confirm the key isn't disabled or expired.
    * See [Errors](/en/errors).
  </Accordion>

  <Accordion title="Getting 404 / model not found?">
    * The model name is misspelled or isn't on the main site's Pricing page. Verify and re-enter it.
    * It can also be a wrong base\_url (see the `/v1` question above).
  </Accordion>

  <Accordion title="Getting 403 / insufficient balance?">
    Your account balance is used up (**it's 403, not 402**). Check the balance on the console home page and top up to resume. It can also mean the token is disabled or the group has no access to that model. See [Billing & quota](/en/billing).
  </Accordion>

  <Accordion title="How do I switch models / providers?">
    Just change the `model` field in your request. The **same key** can call OpenAI / Claude / Gemini / Grok and more — FortAPI converts the protocol automatically. Available model names are on the main site's Pricing page.
  </Accordion>

  <Accordion title="Lost my API key — can I see it again?">
    Yes. Go back to the **Tokens** page in the console and click the eye icon on that token to reveal it, or use "Copy key" to copy the full key.
  </Accordion>

  <Accordion title="Streaming produces no output / hangs?">
    * Make sure you pass `stream: true` and consume it with your SDK's streaming iterator (see the streaming example in the [API Reference](/en/api-reference)).
    * If parsing raw SSE, note each line starts with `data: ` and ends with `data: [DONE]`.
    * Response buffering in a client/proxy can make streaming look "stuck" — disable buffering.
  </Accordion>

  <Accordion title="Frequent 429s?">
    You're being rate limited. Retry with exponential backoff rather than hammering. See [Rate limits](/en/rate-limits).
  </Accordion>

  <Accordion title="OpenAI vs Claude protocol — which should I use?">
    Both are supported and work with the same key. Use the OpenAI protocol for existing OpenAI / LangChain code; use the Claude protocol when you need Claude-native features like thinking blocks. See the comparison table in the [API Reference](/en/api-reference).
  </Accordion>
</AccordionGroup>

Still stuck? Email [support@fortapi.com](mailto:support@fortapi.com) — including the `request id` from the error helps us locate it faster.