URL-based routing

Some tools can only be pointed at a base URL and cannot send custom request headers. Instead of adding sleev-harness and sleev-provider (or sleev-base-url) headers, you can put all the routing information in the base URL itself. Sleev recognizes a reserved /sleev/<harness>/<provider> path prefix on the gateway and reads the harness and provider from it:

ANTHROPIC_BASE_URL=http://127.0.0.1:17321/sleev/hermes/anthropic

This is equivalent to sending sleev-harness: hermes and sleev-provider: anthropic on every request, but the harness never has to know about Sleev headers — it just uses the URL as its base.

For a custom upstream not built into Sleev, put the complete upstream API URL after the harness name:

NOVITA_BASE_URL=http://127.0.0.1:17321/sleev/hermes/https://api.novita.ai/openai/v1

The endpoint path the harness appends after the reserved prefix is forwarded upstream, and the prefix is removed before anything leaves the gateway. Provider credentials still travel in the request's normal Authorization or API key header. Harness names accept the same values and aliases as the sleev-harness header.