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

# Provider header interpolation

<Warning>
  **Provider `extra_headers` use a new value syntax.** Replace `{ literal = "value" }` with `"value"`, `{ env = "NAME" }` with `"{{ env.NAME }}"`, and `{ vault = "NAME" }` with `"{{ secrets.NAME }}"`.
</Warning>

## Provider header interpolation

Provider headers can now mix literal text with environment or secret values in one string, making bearer prefixes and gateway-specific formats straightforward. Secret tokens resolve only token-style vault entries, so missing, file, and OAuth secrets fail closed; put credentials in secrets rather than literal header values.

```toml theme={"languages":{"custom":["/languages/dot.json","/languages/fabro.json"]}}
[llm.providers.gateway.extra_headers]
Authorization = "Bearer {{ secrets.GATEWAY_TOKEN }}"
```

Provider `base_url` remains a literal string and is not interpolated.

## More

<Accordion title="Improvements">
  * Run graph zoom and pan now survive switching between the Overview and Stages tabs
</Accordion>