Stage 3 of the candle-native pivot. neuron now serves
POST /v1/chat/completions backed by candle's quantized_qwen3 forward
pass on a per-model serialised generation loop, returning the standard
OpenAI ChatCompletionResponse envelope.
Pipeline per request:
- Look up the LoadedModel by request.model (404 if absent).
- Apply the Qwen3 chat template across all messages.
- Tokenize, then spawn_blocking onto tokio's blocking pool to acquire
the per-model arch lock and run prefill + greedy/temperature/top-p
sampling via LogitsProcessor.
- Stop on <|im_end|>/<|endoftext|> EOS or max_tokens (finish_reason
"stop" vs "length").
- Decode with skip_special_tokens=true, build OpenAI response with
prompt/completion/total usage counts.
Supporting changes:
- HarnessRegistry now stores Arc<dyn Harness> and caches a typed
Arc<CandleHarness> so inference routes bypass dyn-Trait dispatch.
- LoadedModel.arch becomes Arc<Mutex<ModelArch>> so the lock guard
can be moved into spawn_blocking.
- NeuronState gains an Option<Arc<CandleHarness>> field for the new
inference route.
- Typed InferenceError lets the handler map ModelNotLoaded → 404 and
other failures → 500 without string-matching anyhow messages.
- stream=true returns 501 until Stage 4 wires up SSE.
- Two leftover mistral.rs string references in proxy.rs and cortex-cli
(missed during the Stage 1 sweep) are corrected here.
Three new default-feature tests cover the no-candle 503, model-not-
loaded 404, and stream=true 501 paths. The cuda-integration test from
Stage 2 still covers real load/unload; a streaming-feature gated test
exercising actual generation will arrive with Stage 4.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
rob thijssen
729317d1ef
