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FireRouter uses a bring-your-own-key contract. The service validates your Fireworks key on every request and forwards your provider key only on pass-through legs to closed-source models. FireRouter does not store provider keys server-side.

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Required keys

The FireRouter model currently routes pass-through requests to Claude Opus 4.8 (claude-opus-4-8), so an Anthropic key is required on every request. This pass-through model is subject to change.

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Fireworks key header

Send your Fireworks API key with either header:
The legacy header X-FireRouter-Fireworks-Key is also accepted. New integrations should prefer X-Fireworks-Api-Key.

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Anthropic provider key

The canonical header for Anthropic pass-through is:
x-api-key and Authorization: Bearer are also accepted for Anthropic clients that send credentials that way. For new integrations, prefer x-anthropic-api-key. Example:

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Common errors