API Headers Reference

Headers you can send with requests to the FreeInference API.

Authentication

Authorization

Authenticate requests using your API key.

Authorization: Bearer hyi-your-api-key

X-API-Key

Alternative authentication header. Accepts the same API key value without the Bearer prefix.

X-API-Key: hyi-your-api-key

Request Behavior

X-Reasoning-Passthrough

Controls how reasoning_content is handled in responses from /v1/chat/completions.

Value	Behavior
(missing or any other value)	Passthrough mode — reasoning_content is included in the response
false, 0, no (case-insensitive)	Strict OpenAI mode — reasoning_content is stripped from the response

X-Reasoning-Passthrough: false

X-Session-ID

Attach a stable session identifier for request correlation. This value is logged and can be used to trace a session across multiple requests.

X-Session-ID: 20260503-120000-abc123

Anthropic API

Anthropic-Version

Optional — used only for Anthropic client detection (e.g., to switch the response shape returned by /v1/models). Not enforced on /v1/messages or /anthropic/v1/messages, and not forwarded upstream by this gateway.

Anthropic-Version: 2023-06-01

anthropic-beta

Enable Anthropic beta features. This header is forwarded directly to the upstream Anthropic API.

anthropic-beta: feature-name

Tracing

X-Request-ID

Attach a custom request identifier. If not provided, one is auto-generated. The value is echoed back in the response.

X-Request-ID: my-custom-request-id

Qdrant Proxy

api-key

Authentication for the Qdrant proxy endpoint at /v1/qdrant/. Mapped to Authorization: Bearer <value> internally.

api-key: your-qdrant-key

Your Client Address

Requests reach the API through a CDN, and your address is taken from what the CDN reports — not from any forwarding header you send, which has no effect on it.

IPv6 addresses are recorded in full, but per-client rate limits and sticky routing group them by /64. A single client is usually delegated an entire prefix and rotates addresses inside it, so moving to a new address in the same prefix does not give you a fresh set of limits. IPv4 addresses are grouped per address.

Standard Headers

Header	Description
Content-Type	Request content type (e.g., application/json)
User-Agent	Client identification; affects Anthropic client detection
Host	Logged for debugging