AI Gateway custom providers appear to prepend `/v1` to provider-specific endpoint paths

[matijagrcic]

When using an AI Gateway custom provider via the provider-specific endpoint, Gateway appears to prepend /v1 to the upstream path even when the custom provider base_url is configured without /v1.

Per the docs, this route:

https://gateway.ai.cloudflare.com/v1/{account_id}/{gateway_id}/custom-{slug}/{provider-path}

should map to:

{base_url}/{provider-path}

Docs reference:
Custom Providers -> Via provider-specific endpoint

In my case, the custom provider is configured as:

• slug: exa-provider
• base_url: https://api.exa.ai

So this Gateway request:

POST .../custom-exa-provider/search

should go upstream to:

POST https://api.exa.ai/search

But the actual upstream behavior looks like:

POST https://api.exa.ai/v1/search

Steps to reproduce

1. Create a custom provider with:
   • slug: exa-provider
   • base_url: https://api.exa.ai
2. Create a provider config / BYOK alias for that provider.
3. Send this request through AI Gateway:

curl -sS -i -X POST \
  "https://gateway.ai.cloudflare.com/v1/${ACCOUNT_ID}/${GATEWAY_ID}/custom-exa-provider/search" \
  -H "cf-aig-authorization: Bearer ${AI_GATEWAY_TOKEN}" \
  -H "cf-aig-byok-alias: ${BYOK_ALIAS}" \
  -H "Content-Type: application/json" \
  -d '{"query":"Satya Nadella","category":"people","numResults":2}'