ADR 0002: Pass request bodies through without changes
- Status: Accepted
- Date: 2026-10-24
- Supersedes: none
Context
Clients such as Claude Code and Cline use the native Anthropic and OpenAI formats. These formats contain fields that agents need: prompt cache markers, thinking blocks, and tool-use details. A translation layer between formats can lose these fields or change their meaning.
Decision
Tollgate accepts /v1/messages and /v1/chat/completions in their native formats. It sends the original request bytes to the provider. It does not decode and encode the body again. Tollgate does not translate between formats by default.
Alternatives
- Translate all requests to one internal format, as LiteLLM does. This lets one route use providers with different formats, but it loses provider features.
- Translate only for a fallback to a provider with a different format. This is out of scope until after v2.
Consequences
- A fallback target must use the same API format as the route.
- New provider fields work at once, with no change to Tollgate.
- Tollgate decodes only the few fields that it needs, so the overhead stays low for large bodies.