# 2.2 — Body-based model dispatch (GREEN)

Phase: 2 — LLM surface
Stage: GREEN
Depends on: [2.1](2.1-model-registry.md), [1.1](1.1-reverse-proxy.md), [1.2](1.2-streaming-passthrough.md)

- [ ] `POST /v1/chat/completions` selects its upstream from the `model` field of the JSON request body
- [ ] The body reaching the upstream is byte-identical to the body received, `model` included — dispatch reads, it does not rewrite
- [ ] The upstream sees the canonical path `/v1/chat/completions`
- [ ] `"model":"reasoning"` reaches `reasoning-predictor.llm-serving:80`; `"model":"ornith:35b"` and `"model":"qwen2.5:3b-instruct"` both reach `ornith-predictor.llm-serving:80`
- [ ] `"stream":true` streams unbuffered — chunks reach the client as the upstream emits them, and are not accumulated in order to inspect the body
- [ ] A client disconnect mid-stream cancels the upstream request rather than orphaning it
- [ ] `reasoning_content` is passed through untouched alongside `content`; the gateway does not merge, reorder or strip either
- [ ] Reading the body to find `model` respects the route's body size cap and does not load an unbounded request into memory

This is the single capability Kong OSS lacked — `ai-proxy-advanced` is Enterprise-only —
and the entire reason this gateway exists. Everything else in this phase is a
consequence of it. Ports are 80, not 8080.

An orphaned generation holds one of only eight vLLM sequence slots in the cluster,
which is why disconnect cancellation belongs in the acceptance criteria of this task
and not only in the proxy layer.

## Verify

```bash
curl -s -o /dev/null -w '%{http_code}\n' localhost:8080/v1/chat/completions \
  -H 'content-type: application/json' \
  -d '{"model":"reasoning","messages":[{"role":"user","content":"hi"}]}'
# expected: 200, stub for reasoning-predictor recorded the hit with path /v1/chat/completions and an unmodified body

curl -s localhost:8080/v1/chat/completions -H 'content-type: application/json' \
  -d '{"model":"qwen2.5:3b-instruct","messages":[{"role":"user","content":"hi"}]}'
# expected: 200, ornith-predictor stub hit, reasoning-predictor stub not hit

curl -N -s localhost:8080/v1/chat/completions -H 'content-type: application/json' \
  -d '{"model":"reasoning","stream":true,"messages":[{"role":"user","content":"hi"}]}'
# expected: 200, content-type text/event-stream, first data: chunk arrives before the stub finishes emitting
```